LB 134 Universal Monitor II ID No.: 62688BA2 Rev. No.:

Transcription

1 Program version V 1.00 and higher LB 134 Universal Monitor II ID No.: 62688BA2 Rev. No.:

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3 Content Contents WORKING WITH THE USER'S MANUAL... V SAFETY INSTRUCTIONS... VII 1. DESIGN AND MODE OF OPERATION OF THE LB Overview LB 134 Probes Nuclides and Measurement Types Measurement Results as Raw Data and Calculated Units Background measurement Various Averaging Methods Important Measuring Parameters at a Glance SYSTEM DESCRIPTION Enclosure with Electronics Module Operating and Display Elements Design of the Display Function keys and their meaning Warning Signals Power Supply Working with Batteries Working with Rechargeable Batteries and PSU Power Supply for External Probes Power Supply and Program Memory Data Interface Scope of Delivery Wall Bracket (Optional Accessories) COMMISSIONING Connecting the Device The First Control Measurement Basic Parameter Setup Installation of Wall Bracket for Stationary Operation Possible Problems during Commissioning SOFTWARE DESIGN AND OPERATION Software Design Measurement Menu Display Key Functions Labeled Push Buttons and their Function Softkeys Operation Selecting Menus and Options Editing: Entering Numbers and Letters Selecting Items from a List How to Access the System Menu LED Indicators CONTAMINATION MEASUREMENTS Requirements for Contamination Measurements Function Check Measuring and Saving the Background I

4 Content Creating the Small Nuclide Table Importance and Editing the Other Nuclide Parameters Measurement of Contaminations CPS Measurement Measurement of Area Activities Explanations on Raw Data and Calculated Units Measured Result as a Function of the Contaminated Surface Exceeding of Limit Values SOFTWARE FUNCTIONS Measurement of Contamination, Activity or Doserate Description of the Individual System Menu Items Use Internal DR Detector Background Measurement Mode Measurement Parameters Ratemeter Counter/Timer Search Nuclides/Measurement Types Integral Reset Display Mode Upload and Download Memory and Parameters Parameters Date/Time Language Device Address Calibration Type Light Off [min] Backlight Headphones/Relay Power Supply Hardware Factory setting Alarm Type Ticks Enable Menus PROBES FOR THE LB Internal Dose rate Probe Scintillator Probes with ZnS for Contamination Measurements Cleaning the Detector Window of Contamination Probes with Scintillator Changing the Window Foil of Contamination Probes with Scintillator Contamination Probes LB 1231 and LB LB 1233 with Alpha-Beta P10 Counter Tube LB 6359 and Refill Station LB 1231 with Beta-Gamma Counter Tube LB Counter Tube Change Dose Rate Probe LB 1236-H Neutron Dose Rate Probe LB Neutron Survey Meter LB Nal Scintillation Counter Probe LB II

5 Content 7.8 Activity Probe for Solid Samples LB Tritium Surface Contamination Monitor Device Configuration Application Probe Assembly Counting Gas Supply Tritium Probe with Trolley Commissioning of Tritium Probe Practical Hints for Operation and Measurement Performance Check Efficiency and Detection Limits Working with the β-γ-probe MAINTENANCE Battery Replacement Charging Rechargeable Batteries BASIS OF CALCULATION Calculating the Count Rate Ratemeter Function Search Mode Counter/Timer Function Determination of Calibration Factors in the Event of Contamination DECISION THRESHOLDS AND DETECTION LIMITS APPENDIX Calibration Factors for LB 1342 Scint-Contamination Probe (170 cm²) Calibration Factors for LB 1231 and LB Calibration Factors for LB 1341 (Xenon detector) Calibration Factors for LB 1343, Scintillation Detector (345 cm²) F²C Communication Protocol and Commands Status Definition in LB Transmission Protocol Command Overview Parameter Locking with Jumper J Pin Assignment of the Fischer Sockets Example of RS485 Network with Multiple LB 134 as Dose Rate Monitor TECHNICAL DATA LB 134 UMO II INDEX III

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7 Working with the User's Manual Working with the User's Manual A brief overview of the structure of this user's manual helps you find important information quickly and easily: Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 provides basic information on the design and the mode of operation of the LB 134, the measurement and averaging methods, and the meaning of the displays cps and calculated measurement units. contains a description of the monitor: The design of the device with its control and display elements indicators, the importance of the function keys and the different of power supply options. describes how to take the LB 134 into operation. describes the structure and operation of the software. provides information on the contamination measurement: Prerequisites of the measurement, measurement procedure and explanation of the individual types of measurement. documents all software functions of the LB 134 on the System menu. This is the reference section of the manual. provides an overview of all probes that can be connected at this time, including the data sheets. Chapter 8 describes the maintenance works to be performed on the LB 134. Chapter 9 Chapter 10 Chapter 11 Chapter 12 provides information about the basis of calculation employed by the LB 134 and the statistical accuracy. In addition, the conversion of the measured unit from counts per second to area activities is described so that you can determine your own calibration factors using the specified formula and a calibration source and enter them in the LB 134. describes the statistical error, decision threshold and detection limit. The Appendix contains the calibration factor tables. provides an overview of the technical data. V

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9 Safety Instructions Safety Instructions Use and Function Special instructions The LB 134 is a versatile and flexible instrument designed for use in radiation protection for contamination, activity and doserate measurements. The LB 134 can be employed wherever contamination, activities or doserates caused by radioactive substances occur and are to be monitored: In the medical nuclide laboratory, in radiation research, in nuclear power plants, and in the environment in general. If statutory provisions exist concerning the installation and/or operation of radiation measuring devices, the operator must ensure that these regulations are complied with. The manufacturer has done everything possible to guarantee that the equipment functions safely. The user must ensure that the LB 134 is set up and installed properly to ensure safe operation. With regard to the detectors, please keep in mind: Use caution when measuring rough or sharp objects to avoid damage to the sensitive window foil of the contamination probes. Handle all detectors with care, as the detectors contain either counting gas, a scintillator or a crystal. Proper use and handling of the LB 134 requires that the user is familiar with the user's manual. Therefore, user should read this manual carefully before taking the device into operation. To ensure the correct performance of the device we recommend carrying out the tests and maintenance routines recommended by the manufacturer. Any service and maintenance work above and beyond those described in this user's manual must be performed by BERTHOLD TECHNOLOGIES or by service technicians authorized by BERTHOLD TECHNOLOGIES. VII

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11 Design and Mode of Operation of the LB Design and Mode of Operation of the LB Overview The LB 134 is a versatile and flexible instrument designed for use in radiation protection for contamination, activity and dose rate measurements. It can be employed whenever alpha, beta and gamma contaminations on surfaces such as floors, walls, tables, objects, clothes or the skin, caused by radioactive substances occur and need to be monitored; moreover, it can be used to determine the gamma and neutron dose rate. The contamination detectors with scintillator can be used to distinguish alpha nuclides, on one hand, and beta and gamma nuclides, on the other hand, and to measure them simultaneously. Furthermore, measuring probes are also available which can be used to determine CPS values only, as in these cases calibration in physical units is not possible for various reasons. The LB 134 includes a microprocessor unit with all the necessary electronic functions and interfaces, and an internal gamma dose rate probe. As an alternative to this probe, a variety of different probes for different measurement tasks can be connected externally; we then have a combination device that consists of a basic unit LB 134 and one external probe each, which is connected to the basic unit via a spiral cable. To extend the life of the batteries/rechargeable batteries, the supply of the internal probe is switched off in the menu when not in use. Nine different detectors can be connected to the UMO LB 123 which has been on the market for many years; up to 15 detectors can be connected to the new generation LB 134. The basic instrument identifies the connected detector either via a code resistor (LB123 UMO probes) or via EEprom memory in the detector, which communicates via a I²C bus. This means that the older probes of the UMO LB 123 are compatible. After the detector has been identified, the corresponding parameters will be loaded from memory and measurements are performed with these parameters. Each detector has its own set of parameters that can be changed via the LB 134 keyboard or via data communication. The LB 134 may be used for the above-mentioned measurement functions either as a portable and/or as a semistationary device. Special holding devices are provided (e.g. wall bracket). Single counter events can also be signaled acoustically, alarms can be communicated visually and audibly and can be switched on and off. Additionally, these signals can also be sent to a headphone connected to the device via a jack plug. In this case, the integrated piezo loudspeaker is disabled. Alphas and betas can be distinguished acoustically by their beeps of different lengths. The display backlight can be toggled 1

12 Design and Mode of Operation of the LB134 on and off via a button. In the graphics mode, the measured values can be represented as a function of time, in the ratemeter mode, you always see the graph of the last 120 seconds. A separate jumper allows you to lock certain parameters optionally through the hardware, for example, background values or calibration factors in dose rate probes. The parameters are permanently stored in a memory chip powered by a long-life Li cell. The device includes a USB interface to a host and a device connector to allow communication with a PC or to connect a memory stick. Two other functions can be operated via a separate 6-pin Fischer connector: An external low-voltage relay can be connected, which is enabled when an alarm in the first or second measuring channel is exceeded. This can be used in the event of an alarm, for example, to operate a signal lamp. Furthermore, an RS485 interface is available, allowing integration of the device into a local network. Up to 32 measuring devices, including central computer, can be integrated in this network with a cable length of up to 1000 m. The baud rate to be set depends on the cable length and the number of connected devices. The standard cable used is a shielded twisted pair data cable which has to be terminated at each end of the bus with 120 ohms. The F²C protocol, which is also implemented in some other BT devices, is used for serial data communication via RS485 and USB interface. All parameters can be up- and downloaded with this protocol. Many more features regarding measurement options are available. The device is fully remote controllable. Using a service program, a new program can be transferred via USB interface to the device. A PC control program allows remote control and data transmission with archiving and many graphics options and parameter upload and download. The measurement data memory can also be transferred to the PC. With the USB memory stick, the measurement data memory can be transmitted and the parameters can be uploaded and downloaded. The device is optimally protected against environmental influences such as moisture, dust and temperature. 2

13 Design and Mode of Operation of the LB LB 134 Probes The integrated gamma dose rate probe LB 1346 is a Geiger- Müller tube and is suitable for the low dose rate range from 0.1 µsv/h to 20 msv/h and for an energy range from 50 to 1300 kev. Calibration factor: µsv/h/cps, intrinsic background: 0.07 cps. The probe is calibrated to the H*(10) standard (ambient equivalent dose rate). To extend the life of the batteries/rechargeable batteries, the supply of the internal probe is switched off in the menu when not in use. Currently, the following probes can be connected externally using a coiled cable: LB-number Detector type Application LB 1231 Proportional counter tube, Xe gas βγ contamination LB 1233 Proportional counter tube, P10 gas αβγ contamination LB 1234 NaI crystal, 1" γ activity, only cps value LB 1238 End-window proportional counter tube αβγ activity LB 1239 Proportional counter tube, P10 gas Tritium contamination LB 6411 He-3 proportional counter tube Neutron dose rate LB He-3 proportional counter tube, Neutron dose rate reduced pressure LB 1236-H10 Proportional counter tube γ dose rate LB 6414 He-3 proportional counter tube Neutron search LB 6386 P10 proportional counter tube, large-area αβγ contamination LB 6376 Xe proportional counter tube, large-area βγ contamination LB 1342 ZnS scintillation detector 170cm² αβγ contamination LB 1343 ZnS scintillation detector 300cm² αβγ contamination LB 1341 Xe proportional counter tube 170 cm² βγ contamination More detailed probe data can be found in chapter 7. The following important probe dependent parameters are stored in the parameter sets for each probe: Calibration factors, dead times, allowed measuring ranges, alarm levels, units, fail thresholds and more. The calibration factors for the contamination probes are stored both for the older DIN standard as well as for the more recent DIN ISO 7503 standard. The intrinsic background, which is a detector property, is stored for the gamma dose rate probes and should not be changed. 3

14 Design and Mode of Operation of the LB Nuclides and Measurement Types A separate calibration factor is needed for each nuclide to determine alpha, beta or gamma contamination. We distinguish between alpha and beta/gamma nuclides and assign a calibration factor to each nuclide. Betas and gammas are essentially measured in the same measuring channel and cannot be distinguished alone with the detector. Since there are two different definitions for the calibration of the detectors, according to the DIN and DIN ISO 7503 standards, we need two calibration factors for each nuclide. The nuclide tables of the contamination probes contain about 70 nuclides with the following entries for each nuclide: Name, DIN and ISO calibration factor, alarm threshold, type of radiation (α, β, γ or n), unit, integral threshold, integral unit, time base for integration and status indication whether it is enabled. Before each measurement, you have to select the desired alpha and beta nuclide so that the correct settings are selected. DIN or ISO standard are determined on initial setup of the device by the supervisor and set in the system parameters, and is then usually not changed any more. Nuclides can be deleted or entered new or their parameters can be changed. When using a gamma or neutron doserate probe, for example, no nuclide data are needed because these probes are energy independent and, therefore, nuclide independent in the defined measuring range. You do not have to select a nuclide prior to the measurement. Instead of a nuclide selection, the LB 134 includes a "measuring type" selection for these and similar probes. Each measuring type also has, very similar to the parameters of a nuclide, a parameter set with almost the same entries; however, there is only one calibration factor. This can be used, for example, to define one of the following measurement types: Dose rate 1: With calibration factor for ambient dose equivalent rate H*(10), unit µsv/h, thresholds as desired Dose rate 2: With calibration factor for ambient dose equivalent rate H*(10), unit mrem/h, thresholds as desired (USA) etc. Of course, the correct calibration factors must be entered for the parameters of the individual measurement types. Using this method, one can very quickly change, similar to the nuclides, the measurement types to adapt to the requirements of other countries. 4

15 Design and Mode of Operation of the LB Measurement Results as Raw Data and Calculated Units The LB 134 is able to output raw data as counts per second or, depending on the application, different measured physical quantitities calculated using a calibration factor. Typical units for calculation are for Contamination: Dose rate: Bq/cm², pci/cm² µsv/h, mrem/h, µgy/h, R/h For most probes, the calculation is very simple: Measured value = Calibration factor * (gross rate background) Of course, the gross rate is corrected with respect to dead time or linearity (as in a ZnS scintillator). The displayed accuracy of the measurement due to counting statistics also takes into account the background and the background measuring time. The uncertainty in the calibration factor is not included. In the counter/timer mode, the statistical accuracy G is: G = Rb + Ro Tp To /(Rb Ro) 100 (%) In the ratemeter mode: G = Rb + Ro 2 tau To /(Rb Ro) 100 (%) Where: Rb Ro Tp To tau gross count rate cps background count rate cps sample measurement time s background measurement time s time constant s With preset time constant (also see below under Ratemeter), tau is the entered time constant, with preset accuracy, tau is determined every second from the current count rate and the entered accuracy. For a high accuracy, one should always measure the background as long as possible, e.g. one hour. With increasing sample measurement time in the counter/timer mode, the accuracy is the better, the lower the accuracy value. In the ratemeter mode with preset time constant, the accuracy, with a given tau, also depends on the count rate. To get a higher accuracy with the same count rate, we need to enter a larger time constant. With preset accuracy, you just have to enter a smaller number. 5

16 Design and Mode of Operation of the LB134 Two different methods are available to average the statistical fluctuations in count rates. For searching of hidden radioactivity: a ratemeter mode, where the average value traces the actual rates somewhat delayed; for single sample measurements: a counter/timer function where the counts are added up over a fixed preset measuring time and divided by the elapsed measuring time after background correction. Counts per second (cps) In the simplest case, the LB 134 measures the radiation activity in counts per second. Since the number of counts detected per second is subject to statistical fluctuations, e.g. the abovementioned ongoing averaging (ratemeter) is carried out so that the displayed value is matched to the count rate and the displayed measured value is less and less subject to statistical fluctuations within a short measurement time. Calculated unit of measurement in contamination measurements The simultaneous determination of alpha and beta contamination in two measuring channels is a rather complicated measurement method with this device and therefore has to be treated in more detail. The results of measurements with other probes are always obtained in a very similar way, but in most cases only through one measuring channel, e.g. dose rate probes, Tritium probe or NaI crystal probe. So, if the contamination is to be measured in Bq/cm² (i.e. activities per unit area), the count rate has to be converted to area activities. The conversion factor is different for each nuclide. The individual factors are stored in the device. In each case, therefore, the nuclide or nuclide mixture to be measured must be set on the device prior to measurement. One can set an alpha nuclide for the alpha channel and a nuclide with beta or gamma radiation for the beta-gamma channel. The radiation types are distinguished in the course of the measurement. The measurement is performed at the same time. This does not mean, however, that the LB 134 is capable of measuring these nuclides selectively; rather, the monitor treats contamination (i.e. the measured count rate) as if it were caused by the respective radionuclide. The conversion is based on calibration factors determined for each nuclide. They are not only dependent on - type of radiation, 6

17 Design and Mode of Operation of the LB134 - radiation energy and - decay pattern of the respective nuclide, but other factors are also relevant, such as: - detector sensitivity, - measuring geometry, - self-absorption in the source. The calibration factor indicates the value with which the background-corrected gross counts per second must be multiplied to obtain data displayed in Bq/cm². Accordingly, a Bq/cm² measurement is only correct when the set and measured nuclide match. When setting the unit Bq/cm² and selecting the respective nuclide, the LB 134 automatically converts the measured cps to Bq/cm². The software includes a (editable) nuclide library with about 70 different nuclides and their calibration factors for measurement of the area activity. Moreover, 9 empty positions are available to enter the calibration factors for other nuclides. What to do with unknown nuclides? In practice, however, we often encounter a nuclide mix containing unknown or only partially known nuclides; let us, therefore, consider the following alternatives: Nuclide mix of unknown composition If you do not know the composition, select a calibration factor for alpha or beta sources which is calculated from the average value of the alpha or beta sources which are most frequently encountered after an accident in a nuclear power plant. If you do not know the nuclides, use the setting ß-tot (beta total). Nuclide mix of known composition To measure the activities of several nuclides at the same time, you can do the averaging yourself (if necessary with weighing) and enter the calibration factor. Another alternative is to set a so-called reference nuclide. This means that you select an isotope with medium energy stored in the nuclide library of the device which corresponds to the nuclide mix to be measured. For non-contamination probes, there are various types of measurements, instead of the nuclide table, which can be used to quickly carry out various measurement tasks. 7

18 Design and Mode of Operation of the LB134 Calculated unit of measurement in γ and n doserate measurements Currently, two probes with different energy-compensated counter tubes are available for γ or n doserate measurement; they output the radiation effect as ambient equivalent doserate in units of μsv/h (micro Sievert/h). The integrated probe LB 1346 is an energy-compensated Geiger-Mueller counter tube for the range from 0.1 to 20,000 µsv/h and an energy range from kev. The external probe LB 1236-H10 is an energycompensated proportional counter tube for the measuring range from 0.05 to 10,000 µsv/h and an energy range from 30 to 1300 kev. With the integration function, the doserate can be integrated over time to dose, with dose and integration time being displayed. The calibration factors, the dead times and the intrinsic background have been determined by Berthold Technologies and are already set in the device. The determination of the neutron doserate with the probe LB 6411 or LB is quite similar to the method described here; a He-3 counter tube is used to measure the thermal neutrons generated with the help of a moderator through a nuclear reaction. Without knowing the neutron spectrum to be measured, we get the correct neutron doserate and the corresponding dose within a range from 30 nsv/h to 100 msv/h. Calculated unit of measurement in activity measurements The LB 134 is used to measure the activity of samples (alpha, beta and gamma radiation). One can also choose to display the count rate (cps) or the decay rate (Bq/pCi/dpm, etc.). In this function, the alpha-beta proportional counter tube LB 1238 with end window (about 30 mm diameter) is used as a detector. In contrast to conventional Geiger-Müller end window counter tubes, the counter tube LB 1238 can distinguish alpha and beta activities. The samples are usually measured in the Counter-Timer mode to achieve a high accuracy. The statistical accuracy or the measurement time can be selected as a parameter for the measuring time. Similar to the contamination measurement, in this measurement mode you have to enter separate calibration factors for each nuclide which match your measuring arrangement and the nuclide to be measured. In this measurement mode, the calibration factor is also determined using a sample with known activity. The ratemeter mode is used in this function, for example, for the rapid detection of radiation or radioactive sources, for example, in chromatography, to see if the radioactively labeled sample already appears in the column. 8

19 Design and Mode of Operation of the LB Background measurement 1.6 Various Averaging Methods The background, the normal environmental radiation, is measured in cps. It is automatically subtracted from sample measurements. Gross and raw data values can be displayed on the screen simultaneously. The background measurement can be started automatically after switching on the device. The background should be re-measured every now and then; for sample measurements requiring a high accuracy, we recommend to measure the background directly before carrying out the sample measurement. Since the size of the background and the associated measurement time affect the accuracy of a sample measurement, the background should always be determined using a long measurement time, e.g. 1 hour or more. The size of the background itself depends on the detector and the shielding. If you know that radioactive sources are present in the measurement environment, you should change the location for the sample measurements and, of course, for the background measurement. The LB 134 features the following measurement modes: a) Search Mode to quickly search for contamination, doserates or activities. In this measurement mode, the device is very sensitive to different radiation activities and shows changes very quickly. b) The Ratemeter mode does not react as fast to differences in activity, but is more accurate. In the ratemeter mode one can work with a common time constant or the statistical accuracy. In the second case, the device calculates every second a dynamic time constant from the entered accuracy and the actual count rate which ensures that the measured value reaches this accuracy. If count rate jumps occur, this will not be true directly, but after a certain averaging time, when the count rate is reasonably stable, the actual accuracy will approach the entered value. The measurement time determines when measured values are stored or transmitted. The number of cycles indicates how often measured values are stored. The ratemeter has a dynamic component that ensures that the displayed value tracks the real value as quickly as possible if fast activity changes occur. Since some detectors such as Geiger-Müller counter tubes may occasionally generate interference pulses outside the Gaussian statistics, an additional software burst filter has been added to avoid unrealistic activity jumps. 9

20 Design and Mode of Operation of the LB134 c) The Counter-Timer mode is designed for a high accuracy. The measurement time or the statistical accuracy can be chosen as a measure of the duration of a measurement. In the operating modes "Search" and "Ratemeter", measurements are carried out to find contamination. In this mode, the display quickly follows a change of the radiation field. In the search mode, a lower measurement accuracy is accepted in order to detect changes even faster. An accurate measurement requires in contrast to the search mode averaging of the count rates over an extended period of time. The LB 134 is able to do this automatically in the ratemeter mode, provided that the average count rate remains within the statistical significance all the time during this period. This can be taken for granted, for example, when measuring contamination and the unit is not moved as long as the measurement is running. However, in order to perform stationary measurements with a given accuracy for the mean value, you should select the operating mode Counter-Timer. In this measuring mode, either the averaging time or the statistical accuracy of the measured value can be selected. 1.7 Important Measuring Parameters at a Glance Alarm thresholds Calibration factors Alarm thresholds can be set for each measurement type and for each nuclide; exceeding of these thresholds is signaled visually and audibly. Moreover, in this case the measured value flashes every second. An integral threshold can also be set for the integral value or dose value; exceeding of this threshold is signaled visually and audibly. Contamination monitors include two calibration factors for each nuclide, since the detectors can be calibrated in accordance with two different standards (DIN und DIN ISO 7503 Norm). When purchasing the device, the supervisor determines the standard according to which the measurements are to be carried out and selects the appropriate standard in the corresponding menu. For all other probes there is only a single calibration factor for the nuclides or for measurement types. If a probe cannot be calibrated, we only get raw data and the calibration factor is then 1 for the unit cps or 60 for the unit cpm. The calibration factor is multiplied by the net count rate to obtain the desired unit of measurement. 10

21 Design and Mode of Operation of the LB134 Units Integral calculation time Measuring range limits Fail threshold Each nuclide and each measurement type (see above) has one unit for the measured value and one unit for the integral or dose value. The units consist of strings of up to 6 characters; they can be entered from the keyboard or like any other parameter via the USB interface. These units appear on the display behind the respective measurement results and also with the stored or transmitted data. Examples: Bq, pci, Bq/cm², µsv/h, mrem/h, etc. During the measurement, the current integral value or the dose and the integration time elapsed until then is determined every second by addition. If you have selected the unit counts per second (cps), you get counts through adding up (counts). If you have selected the unit µsv/h, as for the dose rate, then the time base is not second but hour. Therefore, before the addition, the value must be divided by 3600, since every second is added up. When entering the integral calculation time or the time base, this divisor is selected correctly. You can choose between seconds, minutes or hours. There is an upper measuring range value for each channel. OVR appears on the display if this value is exceeded. In this case, the integral calculation (dose) and the integral time will be stopped. The upper limits are determined and set by the manufacturer. When working with ZnS scintillator for contamination measurements, please keep in mind a special feature because of the method used. Since alphas cause quite a bit of afterglow in the scintillator, the beta channel is blocked for about 1.3 ms when an alpha event occurs. Therefore, the message "Beta invalid" appears in the beta channel if the alpha rate is greater than 750 cps. The upper limit for the alpha channel is nevertheless 5,000 cps, for the beta channel 50,000 cps. Each detector has its own fail threshold and fail time because the backgrounds are very different and we do not want to get any false alarms, but on the other hand, we would like to get failure messages as quickly as possible. In contamination probes, failure monitoring always refers to the beta channel. A counter/timer measurement monitoring whether the probe count rate has fallen below the fail threshold is constantly running in the background during a normal measurement. This test is carried out at the end of the fail time and, where appropriate, the error message "Fail" is output. Then, this measurement will start new. Please proceed as follows to determine fail threshold and fail time. Basically, you want a failure to be indicated as early as possible and you choose a small fail time. However, this largely depends on the background rate of the detector. If this background rate is very small, you have to adjust the fail time. When determining the two parameters, it is assumed that the background rate of the detector is Gaussian distributed. To get no 11

22 Design and Mode of Operation of the LB134 false alarms, if possible, you need to set the threshold so low that with the selected measurement time the threshold is, for example, 6 standard deviations below the mean background value. Then the probability that the background rate at the end of the fail time is lower is less than 1.0E-06 and then there is virtually no false alarm. Example: Background Ro = 0.5 cps; set measuring time Ta = 600 s; then it holds for standard deviation S: S = Ro Ta =0.029 cps 6 standard deviations = cps Fail threshold = Ro 6 S = 0.33 cps At Ta = 300 s, the fail threshold would be cps. If you get a negative fail threshold, you have to increase the fail time. However, you can always increase the number of standard deviations to be quite sure that you do not get any false alarms. Dead time Each detector has its own dead time which depends on the detector properties and the subsequent amplifier and discriminator electronics. With gas-filled counter tubes and NaI crystals this is typically 1 to 3 µs. The effect of the dead time is that count rates with increasing size do not increase linearly any more at some point, but go into saturation. This effect is corrected to a certain degree by the dead-time correction and the curve is linearized again. The dead times for the individual detectors are determined and preset at the factory. The formula used is: Rcorr = Rmeas / ( 1 tau * Rmeas) Where Rmeas: Tau: Rcorr: measured count rate in cps Dead time in s dead-time corrected count rate Alpha only / Beta only mode Three modes can be used in a detector with simultaneous alpha/beta measurement: Alpha/Beta simultaneously Only alpha device Only beta device If you select alpha only or beta only, the device behaves as if it is measuring only alphas or only betas. The results of the other type of radiation appear never and nowhere. With simultaneous 12

23 Design and Mode of Operation of the LB134 alpha/beta measurement one can select the view in three variants: Alpha and beta values as large display, alpha values large and beta values on the info bar, beta values large and alpha values on the info bar. Store measured values Up to 2,400 individual measured values can be stored and transferred to a PC or a memory stick via USB interface. The important parameters are saved with the stored values. This depends on the measurement mode. The memory can be used as a memory with fixed length or as a FIFO. With FIFO there is a write and a read pointer. If FIFO is full, everything starts again from scratch and the oldest value is overwritten. The FIFO can be read out and edited via the USB interface using special commands. In a fixed-length memory storing ends when it is full and an error message is displayed; a status bit is set. The following data is stored for each measurement: Date/time, status, measuring time, measured value 1 (alpha), measured value 2 (beta), unit, integral value 1, integral value 2, unit integral value, integral time (h). The status includes: Probe type, detector failure, alarm 1, alarm 2, integral alarm 1, integral alarm 2, measurement active, FIFO 75% full, memory full, measuring range OVR1, measuring range OVR2, beta channel invalid. A total of 12 ASCII HEX characters. 13

24 2. System Description 2. System Description 2.1 Enclosure with Electronics Module The splash-proof enclosure contains the measurement and control electronics, the internal dose rate probe LB 1346, the software and the control elements of the monitor (see Figure 2.1). Figure 2.1: Basic unit LB 134 Electronics The complete electronics with integrated dose rate probe LB 1346 (including software and high-voltage generation) is located inside the case. The connections for external components are on the left and right. At the bottom, there are two contacts to charge the batteries when the unit is placed in the wall bracket. The internal dose rate probe LB 1346 is mounted on top behind a bulge in the case. 14

25 2. System Description Figure 2.2: Position of internal dose rate probe Connections The connections for the power supply unit (PSU), the headphones (jack plug), relay connection for the external signal lamp and RS485 communication are located on the left side of the device. USB host and device connections and the Fischer connector for the external probes are located on the right side. Headphones PSU Relays and RS485 Figure 2.3a: Left side of LB 134 with connections 15

26 2. System Description Probe USB Device USB - Host Figure 2.3b: Right side of LB 134 with connections Operating voltage The device can either be operated via power supply unit (PSU) (6 V), via rechargeable batteries (4x Mignon 1.2 V) or via batteries (4x Mignon 1.5V), located at the bottom of the device (see Figure 2.4). If the PSU is connected, the operating voltage is supplied through the line voltage and the rechargeable batteries can be charged. The charging process starts automatically. During charging, the device is mains powered. If the LB 134 is connected directly to mains or to the charging station, the unit turns on automatically. Battery compartment cover Contacts wall holder Figure 2.4: LB 134 (rear view) 16

27 2. System Description 2.2 Operating and Display Elements Measurement, operation and display are controlled by the software integrated in the LB 134. Results, menus and user information are displayed on a monochrome LCD graphics module (192 x 64 pixel) with LED backlight and scratch-resistant Plexiglas. The device is operated by means of six function keys below the display. Alarm and status signals are output via two LEDs and a buzzer Design of the Display Measurement menu Top line (black background): Measurement mode and probe name are displayed in the top line. Center panel: Net measured value(s), with unit of measurement and measurement nuclide(s)/measurement type or net (= cps measurement). With simultaneous / measurement, both measured values are displayed. Below that, information on the measurement is displayed which can be selected via the Info softkey: e.g. gross values or display as Scale from 0-100% relative to the alarm threshold of the selected nuclide and many more. Measurement mode Measured value Info line Softkeys (menu) Function keys Figure 2.5: Display and function keys Bottom line (black background): Displays menus and functions that can be selected via the buttons below the display (so-called softkeys). The top four function buttons have the function assigned to them by the softkeys located directly above each button. 17

28 2. System Description System menu On the System menu the menus and functions are displayed for selection, and parameters can be edited. The selection and parameter input takes place via the push buttons. The bottom line of the display shows the function of the push buttons. Figure 2.6: Softkeys directly below the display Function keys and their meaning The device and software is operated using six push buttons, two of which are labeled with their function name. In the Measurement menu, the top four buttons have the function assigned to them by the softkey located directly above each button. The softkeys are displayed in the bottom line of the display (in black) Warning Signals LED indicators Top LED Bottom LED Acoustic signal Battery change The LEDs on the membrane keypad indicate the following states: Alarm when threshold is exceeded After pressing a button the LED lights up as long as the processor is busy processing the triggered function. When the threshold is exceeded, a warning signal is output (provided this has been set in the Parameters menu). The red LED (top) is flashing. In the Parameters menu you can choose Visual or Audible as signal type. If the battery/rechargeable battery voltage displayed after power on is below 4 V for battery operation and below 4.5 V for re- 18

29 2. System Description chargeable battery operation, the remaining battery life is 2-4 hours max.! 2.3 Power Supply In this case, the batteries need to be replaced. Remove the battery cover by pulling it downward. Figure 2.7: Open battery compartment The device can be operated with 4 batteries or (Mignon 1.5V) rechargeable batteries (Mignon 1.2V). The polarity of the batteries is indicated at the bottom of the battery compartment (see. Figure 2.7). Whenever you turn on the device, you will be informed about the status of the batteries: The voltage can be viewed on the menu Parameter/Power supply. Note: The RAM which stores the measured values, settings and the date is regularly supplied with power by a lithium backup battery when the device is not powered via the mains or batteries/rechargeable batteries. In order to avoid loss of data, we recommend replacing the lithium battery while the unit is powered via the mains or batteries/rechargeable batteries. The lithium battery is located on the motherboard and should be replaced only by trained personnel. 19

30 2. System Description Working with Batteries If batteries are used as power supply, you must select Battery in the Parameter/Power Supply menu. With this setting, the Charge function is disabled Working with Rechargeable Batteries and PSU If rechargeable batteries are used as power supply, you have to select Accu in the Parameter/Power Supply menu. With this setting, the Charge function is enabled when the charging mode is set to ON (indicated by an X in the square box). Do not enable the charge function while batteries are in the device. The device turns on automatically when the LB134 is connected to mains, directly or through the wall holder. The charging process restarts depending on the settings in Cell Type, Charge Mode and Charge Time: The charging process only takes place when the device is switched on Power Supply for External Probes Batteries or rechargeable batteries supply power to the basic unit and also to the external probes (5 V). The high voltage in the probes is adjusted internally in the probes, but may also be set using the control voltage (see below). The default setting for the control voltage is 2.5 V Power Supply and Program Memory 1. The software program, the factory-set calibration factors and any fixed settings are stored in FLASH and are independent of the power supply. 2. The user-defined calibration factors, threshold settings, date, measured values, etc. are stored in RAM (Li-batterybuffered). Using the Reset function (factory settings under Parameters/Factory setting), these values can be deleted, in which case the factory-defined settings are loaded. This function is available only when the appropriate privileges have been assigned. 20

31 2. System Description 2.4 Data Interface The LB 134 has two USB ports, a USB host and a USB device interface with the appropriate connectors. However, both cannot be used simultaneously. A memory stick can be connected to the USB host interface, and a PC to the device interface. Parameters can be uploaded and downloaded, currently measured data or the entire memory contents can be transferred to PC and various measurement functions can be executed using a PC program. The program creates different graphics and archives measured data or parameter files. The complete measurement data memory can be transferred or parameters can be uploaded to and downloaded from the memory stick. Furthermore, an RS485 interface is available, allowing integration of the device into a local network. Up to 32 measuring devices including central computer can be integrated in this network with a cable length of up to 1000 m. The baud rate to be set depends on the cable length and the number of connected devices. The standard cable used is a shielded twisted pair data cable which has to be terminated at each end of the bus between both wires with 120 ohms. The cable shielding is connected to ground at the central station of the network. The shielding may also be connected to device ground at the individual measuring stations with LB 134, as long as they are operated with the power supply units provided, as these do not have any connection to the local ground (no protective earth connection) and thus cannot produce any undesirable ground potential differences. The F²C protocol, which is also implemented in some other BT devices, is used for serial data communication via USB or the RS485 interface. The baud rate for the USB interface is always constant at 38,400 baud and cannot be changed; for the RS485 interface it can be selected between 2,400 and 38,400 baud. (Menu Parameter/Hardware). The other parameters are fixed: data bits: 8; parity: none; start bit: 1, stop bit 1, no handshake. At the end of each cycle, if selected, the following data is written to a memory (read-only memory or FIFO): 21

32 2. System Description Date/Time: (Memory number: is sent with F 2 C) Cycle number: (ushort) Status: 12 characters, ASCII Hex Sample measurement time [sec]: (ushort) Nuclide name / Measurement type name 1: Text [7] Measured value 1: float Unit 1: Text [6] Integral value 1: float Integral unit 1: Text [6] Accuracy 1: Float Nuclide name 2: Text [7] Measured value 2: float Unit 2: Text [6] Integral value 2: float Integral unit 2: Text [6] Accuracy 2: Float Integral time since last reset [h]: float Required disk space per record: (6 bytes) (2 bytes) (12 bytes) (2 bytes) (8 bytes) (4 bytes) (7 bytes) (4 bytes) (7 bytes) (4 bytes) (8 bytes) (4 bytes) (7 bytes) (4 bytes) (7 bytes) (4 bytes) (4 bytes) (94 bytes) The depth of the FIFO is 2400 measured data. With Read FIFO, the above data are transferred in this order after sending the header data (frame). The current status of the measuring device is determined every second. This includes the states of all errors and alarms. This information is summarized in 12 Ascii hex characters, with each bit corresponding to a particular state. These 12 characters are transmitted with the Get status command and with Store automatically each current measurement time is saved to memory. On request, the communication protocol can be supplied with a command list. 2.5 Scope of Delivery Basic equipment Standard accessories Optional accessories Measurement and display unit LB 134 with integrated dose rate probe LB set of Ni/MH rechargeable batteries (Mignon (AA) 1.2V/2.5Ah) 1 power supply unit (PSU) 1 bag with strap User manual wall bracket for LB 134 basic unit (incl. screws and dowels) Wall bracket for LB 1343 contamination probe Different probes for the desired measurement tasks 22

33 2. System Description 2.6 Wall Bracket (Optional Accessories) The optional wall holder bracket is used as Charging station (only with rechargable battery operation). The LB 134 turns on automatically when the PSU is connected to the wall bracket and to mains. The charging process takes place only when the unit is (still) turned on and when Accu is set as Cell type in the menu Parameter/Power Supply! Stationary application. The wall bracket is designed such that the monitor is about 3 cm from the wall. Measurements can be carried out in the battery or rechargeable battery mode. We recommend working with the device with rechargeable batteries and the PSU connected (see charging station). Scope of delivery The delivery comprises the wall bracket and one set of dowels and screws 4 mm in diameter. These dowels and screws should be adequate for most walls. Other dowels/screws may have to be used depending on the type of wall. The spacing of the drilled holes for fixing the wall bracket is 85 mm. Wall bracket (with mounting holes 5 mm in diameter) Charging contacts PSU connector Figure 2.8: Wall bracket 23

34 2. System Description Figure 2.9: LB 134 with wall bracket 24

35 3. Commissioning 3. Commissioning 3.1 Connecting the Device Unpack the device carefully. Supply the device with power. The device can be operated with batteries (Mignon 1.5V) or rechargeable batteries (Mignon 1.2V) or PSU (ID58067): Battery or rechargeable battery operation: Remove the battery compartment cover by pushing it down. Insert the batteries into the battery compartment as indicated at the bottom of battery compartment. See Figure 2.7. Mains operation: Plug the power supply cord on the left side of the device into the corresponding jack, and secure it with the screw cap. Plug the power adapter into the power outlet. The device will be switched on automatically. If the detector LB 1342 or LB 1343 is supplied, remove the transport protection for the entrance window of the detector on the device bottom by pushing out the black metal plate. Keep the plate and always use it to protect the window foil against damage during transport. Press the On/Off button in the bottom left corner to turn on the unit. After power on, the device shows the software version, battery/rechargeable battery voltage, free memory space and the date for 3 seconds, then changes directly in the ratemeter or counter-timer mode and is ready for operation immediately. Depending on the connected probe, the measured value or the measured values of the measuring channel or both channels (beta-gamma and alpha channel) are displayed. Figure 3.1: Measured value display of the internal dose rate probe after power on 25

36 3. Commissioning 3.2 The First Control Measurement If you do not want to measure with the internal dose rate probe, connect the desired external probe first to the device using the spiral cable. Press the ON/OFF button to turn on the unit. After power on, the device shows the software version and the battery/rechargeable battery voltage and then automatically switches to the measurement mode. The LB number of the probe is displayed in the top row. If this is not the same as the LB number of the probe, this means that the internal probe is selected. In this case, please enter the menu by pressing the menu button: If the checkbox in the top right corner is ticked, this means that the internal dose rate probe is used, even when the external probe is connected. As the cursor (left arrow) is already in this line, you can disable the internal probe by pressing Enter; then the external probe will be used (the X is removed). Press ESC to go to the Measurement menu. Now you can run measurements with the external probe. If you want to test the functionality of the device first, you can do this using the test source, you are also using otherwise, in the same geometry in front of the detector and compare the displayed value with the target value that you have obtained during the first commissioning. Depending on the probe used, you have to position the respective test source accordingly, as otherwise the measurement result is not correct. When working with the LB 1342, slide the metal plate with the test source Sr-90 in front of the detector. After about 10 seconds measurement time, read the measured value and compare it with the value indicated on the test source. Your reading should reach this value with a tolerance of +/- 20% after about 10 seconds. 26

37 3. Commissioning 3.3 Basic Parameter Setup Before starting any measurements, you have to define the most important parameters and change the factory-set parameters (alarm thresholds, background, etc.) to match your needs and circumstances. Check and/or change the following parameters: Set the Language. Enter Date/Time. Important for your documentation. Date and time are stored with each measurement. Define Meas. Parameters for the individual measurement modes and measurement channels in the Measuring Settings menu. If necessary, define calibration factors for additional nuclides or nuclide mixes and adjust the nuclide-specific warning thresholds. Nuclide or measurement type selection for the measurement. In order to select the nuclides or types of measurement required for your needs during an on-going measurement directly you should select the relevant nuclides/types of measurement in the small nuclide table/measurement type table for the measurement menu. Perform background measurement. The background is subtracted for each measurement. The background should match your ambient conditions and you should check and update it occasionally (at least once a week). For dose rate probes, there is a so-called intrinsic background, which is determined under very special measuring conditions in the factory (special and extensive shielding). This value must not be changed. To simplify handling, the device allows you to hide single or all menus for the measurement operation. On the other hand, the menus can be enabled only to View only the parameters or to View and change the parameters. The supervisor of the unit should carefully consider which menu mode is suitable for his area of work. A password is required to enable the menu. Upon delivery, the password is 0. 27

38 3. Commissioning 3.4 Installation of Wall Bracket for Stationary Operation For stationary operation, mount the wall bracket on the wall using the supplied screws and wall plugs (at about chest height). Connect the PSU to the wall bracket and to mains. We recommend using rechargeable batteries for this application; select Accu in the Power Supply menu. Set the Charge Mode to On (X). Place the LB 134 in the wall bracket. The unit turns on automatically. If you are working with an external probe, this probe must also be mounted on the wall in the vicinity of the device and connected to the device with a coiled cable. For RS485 networking, connect the shielded twisted pair data cable to the device using a 6-pin Fischer connector. The last device and the first device or data center at the ends of the bus cable must be terminated with 120 ohms (either in the plug or a wiring box). Now you are ready to perform stationary measurements provided the appropriate device settings have been done. 28

39 3. Commissioning 3.5 Possible Problems during Commissioning The following errors or error messages may be encountered during commissioning: Error (message) No message in display Cause/Remedy Batteries are exhausted. Replace batteries. No power supply. Check connection cable. Target count rate of test sources not reached or Background count rate is too low. or Displayed count rate is "0.0 CPS" Correct detector and possibly check tightness: o o For scint detectors: If detector foil is defective and light enters, the high voltage turns off, count rate is zero. Then the device must be turned off. For gas-filled contamination detectors: If detector is OK, the detector foil must be smooth, tense and plane. A slack, wrinkly foil indicates that the counter tube is damaged. Please call Service! Possibly, HV unit of detector is defective. Replace the detector if the HV unit is defective. The set background is too high. To check this, push the Info button to view the gross data. Connection electronics <--> check probe INV (only scint detector) OVF Count rate in alpha channel > 750 cps. Above this count rate, no meaningful measurement is possible in the beta channel. Measured value above the measuring range For scint detectors: Count rate in alpha channel > 5000 cps or Count rate in beta channel > cps. 29

40 4. Software Design and Operation 4. Software Design and Operation 4.1 Software Design System menu The software of the LB 134 has a menu-based user interface. All functions and parameter settings are selected from the System menu. The main menu items of an alpha-beta contamination probe are as follows (in a dose rate probe Nuclides is replaced by Meas. Types): Figure 4.1: System menu for alpha-beta probe Several dots (...) behind a menu item indicate that this function leads to further displays. For menu items showing a parameter setting (e.g. menu item Meas. Mode), the setting can be changed directly by selecting the respective menu item with the cursor ( ) and pressing the Enter key. You select an item with (left button) and change the setting with the Enter key. To select a menu or an option, move the cursor to the desired menu item and then press the Enter key. 30

41 4. Software Design and Operation 4.2 Measurement Menu Display The Measurement menu appears a) immediately after switching on the device or b) by pressing ESC on the System menu. We have chosen a dose rate measurement as an example. If you press the double arrow key ( ) on the right, further functions appear in the bottom line. If you press the double arrow key on the right once more, further functions appear in the bottom line. If you press this key once more, the first functions appear again (see first picture). The functions are explained in detail. Figure 4.2: Measurement menu of a doserate probe In the measurement menu, the type of radiation is displayed first that was set on leaving the measurement menu. In an alpha-beta contamination probe, you can then choose whether both types of radiation are to be displayed at the same time or what type of radiation (measuring channel) is to appear as the main display. The other measuring channel is then displayed in the info bar. 31

42 4. Software Design and Operation In the menu item Display Mode you can toggle between these modes of display. You can select additional information to the main display by briefly pressing the Info button in each of the three modes of display. The three display options for alpha and beta contamination show the following three displays. Main display: - channel Main display: Both channels Main display -channel Top line of display Second line (only 1 channel) 2 nd /3 rd line with 2 channels Center (one channel) Info line, second line from the bottom Scroll with Info Bottom line Indication of Measurement mode (ratemeter, counter/timer...) and LB number of the probe and Status (buzzer / light) and on the left the storage number at the time of saving Left: Nuclide or Measurement type or Net/Gross Right: Radiation type Radiation type, nuclide/measurement type, measured value, unit (third line same as second line but only for channel 2) Net/gross results during the measurement (in [cps], [Bq/cm 2] or µsv/h or according to the selected nuclide(s) and/measurement type(s) or the computed unit of the measurement Measured value of the 2 nd measuring channel, dose (integral value), bar graph, accuracy, calibration factor, date and time, background with measurement time, minimum and maximum value, raw data value, net count rate, measuring time at N cycles, accuracy of the mean, selectable by repeatedly pressing (briefly) the Info button Display of softkey function relative to the selected mode. Counter/Timer: During measurement: Info, Stop, Graph After the measurement: Nuclide, Start, Menu, Info, Mode, Save, Graph, Start, Integral Ratemeter: Search: During measurement: Nuclide, Save, Menu, Info, Mode, Graph, Reset, Integral start During measurement: same as Ratemeter During the measurement, the Nuclide/Measurement type stored in the small nuclide library can be selected by repeatedly pressing the Nuclide/Measurement type button (separately for each type of radiation). 32

43 4. Software Design and Operation Info button Main display: - channel Press this button repeatedly and briefly to display additional information on the ongoing measurement. Even after measurement end, further information is available for counter-timer and background measurement measurements. Depending on the measurement mode, the following additional information is displayed: Main display: - channel Additional display of the measured value of the 2 nd channel (here alpha channel) % Scale. This bar graph shows the ratio of the respective measured value to the set threshold value. Expressed as a percentage of the threshold value. If the threshold is exceeded, the top LED flashes and an alarm is triggered if preset. The multiplication factor is indicated next to the graph: x10; x100; x1000. Accuracy of 1 st measuring channel Threshold value and calibration factor of the 1 st measuring channel Cycle X of N, measuring time, preset measuring time Background that is subtracted Minimum and maximum value of the current measurement in the 1 st /2 nd channel. Gross measured value Mean value over N cycles, total measurement time, MV accuracy also available 33

44 4. Software Design and Operation 4.3 Key Functions A long keystroke is identified by a double tone and by a brief flashing of the lower LED. Then you can release the button. The software is operated using the 4 push buttons in the middle, below the display. They have the following functions: In the Measurement menu and during measurements, softkeys (menu options) are displayed in the bottom line of the display which assign their respective function to the button located directly below the softkey. Push the button to select that option Labeled Push Buttons and their Function The label on each key indicates the function of this key. Turning on/off the device. Push this button for about 0.5 seconds to power on, and for at least 1 second to power off. Turning on/off the buzzer and the LCD backlight and adjusting the display contrast (keep button pushed until the desired value is reached). The current status is displayed in the top line of the display. If the LCD backlight is turned on: The backlight turns off automatically if no button is pushed for 60 seconds. It is turned on again automatically when a button is pushed Softkeys The software is operated using so-called softkeys. Softkeys are software-controlled key functions which assign the push buttons their current functions on the display. They are shown in the bottom line. Line with softkeys Figure 4.3: Softkeys and assigned functions 34

45 4. Software Design and Operation Explanation of the example in Figure 4.3: Press the third button (Menu) to enter the System menu to select the individual menus. Press the Meas. Type button repeatedly (if you are working with contamination probes you will see Nuclides here instead) to scroll through the small nuclide library/measurement type table and you can select the desired nuclide/measurement type of the displayed type of radiation for the current measurement. If the display does not switch to another nuclide/measurement type when you press this button, this means that no further nuclide/measurement type has been defined. Press the Save button to save the measurement. Press the button to go to the next functional level (see above). 4.4 Operation Selecting Menus and Options On the System Menu, move the cursor ( ) to the desired menu or the option by pressing the key and then press Enter. The relevant menu item is enabled and the associated page is displayed Editing: Entering Numbers and Letters Move the cursor ( ) to the desired parameter by pressing the key and then press Enter. This enables the editing mode for the respective parameter and the first digit is marked by the cursor. Figure 4.4: Selecting a parameter Start typing here to make a new entry. To overwrite an existing digit, move the cursor to the desired digit. Now select the desired number by repeatedly pressing the key. To enter the second place, press the button and then select the desired number by repeatedly pressing the key. 35

46 4. Software Design and Operation Proceed in the same manner with all digits of the desired number. Once all digits of the desired number have been entered, press Enter to confirm. Letters are entered in the same way ( abc...z) Selecting Items from a List If you can only select predefined values or categories from a list, proceed as follows: Select the parameter with the cursor. Press the Enter key. The editing mode is enabled. Repeated press the to view the available options one after the other. Select the desired option with Enter. The selection is accepted. Examples: Setting the Measurement Mode Ratemeter Counter-Timer Search Measurement settings for ratemeter measurements: Averaging criterion Time constant or Accuracy How to Access the System Menu After power on After power on, the device automatically goes into the measuring mode which was set when the device was turned off (Measurement menu). In the Ratemeter mode: Select the Menu option by pressing the Menu key. You get into the System Menu. In the Counter-Timer mode: Stop the running measurement by pressing Stop. The Menu softkey appears. Then press the Menu button. 36

47 4. Software Design and Operation During parameter input Quit the edit mode by pressing Enter or Esc. Press Esc once more. This will bring you to the one next menu in the menu tree until you get to the System Menu. Figure 4.5: System menu with menu items LED Indicators The two LEDs on the membrane keypad indicate different states: Top LED: Alarm when the threshold is exceeded. Bottom LED: When you press a button for a longer time then this LED goes on for a very short moment to indicate that you can release the button. This is used to move the cursor backward in a menu. 37

48 5. Contamination Measurements 5. Contamination Measurements In this chapter we will discuss the contamination measurement, which is representative of the performance of other measurements. Other measurements, for example, activity measurements of samples or dose rate measurements, are very similar, but they still differ in some respects. Contamination and activity measurements usually deal with specific nuclides or nuclide mixes, whereas we usually do not know the nuclides in a dose rate measurement. Selectable measurement types were therefore introduced instead of nuclides to quickly switch between different units (e.g. µsv/h and mrem/h). In all cases, you can use the ratemeter function or the counter timer function, depending on accuracy considerations. Sample measurements, however, should essentially be performed using the counter timer function. You can also calculate the integral over the measurement unit in all types of measurement, which is of major importance in dose rate measurements for the calculation of the dose. In contamination measurements, one can determine the counts for a given period from the cps values through integration by selecting Net. We will now take a closer look at a contamination measurement. Contamination measurements can be performed immediately after starting up the device and in conjunction with an external contamination probe. After power on, the device starts a measurement immediately and displays the results for the preset nuclide and measurement mode or for the background measurement (if the autostart function has been enabled). Please note that the following three operations have to be performed as a prerequisite for adequate contamination measurements: 1. After commissioning of the monitor and later at regular intervals, you have to perform a functional check and verify the correct operation of the device. This is also required by 67 of the Radiation Protection Ordinance (in Germany). 2. Usually, we first measure the ambient radiation caused by the activities (= background) to obtain the pure surface radiation. The stored background is subtracted automatically from all measurements. 3. Nuclide-specific alarm thresholds are entered for the radiation to be measured; audible and visual alarms are triggered when these thresholds are exceeded. 38

49 5. Contamination Measurements 5.1 Requirements for Contamination Measurements Function Check Turn the device on and make sure sufficient battery capacity is available. Warnings: If the battery/rechargeable battery voltage displayed after power on is below 4V for battery operation and below 4.5 V for rechargeable battery operation, the remaining battery life is 2-4 hours max.! Eliminate this problem prior to measurement! Slide the plate with the test source on the detector and read the measured value after about 10 seconds. After this time, a sufficient measuring accuracy is reached. You can also use the System Test function of the PC program. You can check if the measured value coincides with a target value within a given limit. Compare the measured value with the target value that is specified on the test source for each detector type and the selected source type. The device is working properly only if your measured value is within the specified range of variation Measuring and Saving the Background The background, the environmental radiation, is measured in cps. It is automatically subtracted from sample measurements. Gross and net values can be displayed on the screen. Proceed as follows Select Background on the System Menu. The background parameters and the start option will be displayed. 39

50 5. Contamination Measurements Figure 4.6: Background menu for contamination probe Set the desired parameters for the background measurement. Background: Shows the currently stored - background. It may come from a background measurement or it can be entered manually. The stored background is always subtracted from each measurement. Background: Shows the currently stored background. It may come from a background measurement or it can be entered manually. The stored background is always subtracted from each measurement. Meas. Time: Autostart: Enter the desired measuring time. Enter at least 60 seconds, better 600 seconds in order to get accurate results. When ON is set (X mark), a background measurement is carried out automatically whenever the device is turned on. BG Meas. Time: If a background measurement was carried out, the elapsed background measurement time is entered here after saving. On the other hand, if you have entered the background by hand, you have to enter the measuring time associated with the background, so that the accuracy calculation is correct for a contamination measurement. Start the background measurement by moving the cursor ( ) to Measure background and press the Enter key. Then the background measurement starts. Figure 4.7: Background measurement The measured values and the elapsed measuring time are displayed continuously. At the end of the measuring time, 40

51 5. Contamination Measurements the background measured for both measuring channels is displayed. End of the background measurement: When the preset measuring time is over or by pressing the Stop button. The following softkeys are now enabled: Save the background, Start a new background measurement, back to the system Menu and Info. Figure 4.8: Display at the end of a background measurement Select the Save option by pressing the Save button The stored background is displayed on the menu next to background and background (see Figure 4.6). The background should be measured daily or occasionally or it should be measured new and stored whenever changing the environment to avoid incorrect results! Automatic background measurement With the autostart function enabled, a background measurement is carried out with the preset parameters whenever the device is turned on. At the end of the background measurement (measuring time is over or stop) the value determined can be stored via the Save button or a new background measurement can be started with Start. 41

52 5. Contamination Measurements Procedure Automatic background measurement after power on of the device. BG measurement finished (at the end of measurement or by pressing Stop) Saving the BG values Figure 4.9: Display at the end of a background measurement Press ESC twice to start the contamination measurement. Figure 4.10: Return to the measurement menu Creating the Small Nuclide Table To be able to select particular nuclides for a sample measurement, you first have to select those nuclides from the nuclide table that you use most frequently and that you wish to access directly during measurements. These nuclides are stored in a small nuclide table to which you have direct access during each measurement via the Nuclides softkey. The scope of the small nuclide table is adjustable (minimum: net; maximum: all nuclides). This allows you to switch to another nuclide at any time. Upon delivery, the small nuclide table already includes several nuclides. At the same time, you can enter Alarm Thresholds for these nuclides; when they are exceeded, an alarm signal is output. 42

53 5. Contamination Measurements If the nuclide or nuclide mix to be measured is not yet included in the small nuclide table, proceed as follows Select Nuclides on the System Menu. Figure 4.11: System menu Press the Enter key. The nuclide table is displayed. The nuclides contained in the small nuclide table are marked with an X. Figure 4.12: Nuclide table. Pre-selected nuclides are marked by an X. Move the cursor to the nuclide you wish to include in the small nuclide table using the key, and then press the key to go to the next function level. Now press the Edit button. A new menu will appear listing all nuclide parameters: Name, Active, Radiation Type, Mass Number, Unit, Cal. Factor A-100 (according to DIN 25415), Cal. Factor ISO (according to DIN ISO ), Alarm Threshold, Integral Threshold, Integral Unit and Time Base. Now move the cursor to Active to select the nuclide with Enter. Press ESC twice to quit the nuclide table. You get into the System Menu. 43

54 5. Contamination Measurements Importance and Editing the Other Nuclide Parameters In addition to the activation of a nuclide, there are the following parameters: Figure 4.13: The parameters of a nuclide Edit procedure Move the cursor (->) to the desired menu item. Press the Enter key. A list of options or the field for parameter input appears (see above). Enter the desired value, or select an entry from the list. Confirm your entry by pressing the Enter key. Meaning of the parameters Name: Name of nuclide Active: Select nuclide for selection prior to a measurement (small nuclide list) Radiation Type: Alpha, beta/gamma, gamma, neutron Mass Number: Mass number from the nuclide table Unit: Physical unit Cal. Factor A-100 Calibration factor according to DIN

55 5. Contamination Measurements Cal. Factor ISO Calibration factor according to DIN ISO Alarm Threshold: Alarm threshold for visual and audible alarm in the same unit as above Integral Threshold: Threshold for the integral value of the measurement unit Integral Unit: Unit of the integral value Time Base: Used for calculating the integral, for s the measurement value is added linearly every second, for min each measured value is first divided by 60 and then added, for h each measured value is first divided by 3600 and then added (e.g. for µsv/h) 5.2 Measurement of Contaminations Two types of measurement are available for surface contamination measurements: 1. Measurement of the net count rate in CPS (counts per second). 2. Measurement of the net activities per area with the unit Bq/cm²; the nuclide or nuclide mix to be measured has to be set. Both types of measurement can be selected in the Ratemeter, the Search or the Counter-Timer measurement mode. The measuring channel (, or and ) is selected on the System menu under the menu item Display Mode. The nuclide are set in the Measurement menu by repeatedly pressing the Nuclides key. In the and mode, however, a new softkey group appears with separate keys for the alpha and beta channel, which allows separate nuclide selection. You pass through the nuclides selected from the nuclide table (small nuclide table) and the measurement mode Gross and Net [cps] in cyclical order. The selected nuclide is displayed in the top left corner of the display. When passing through the small nuclide table only the nuclides of the set measuring channel (type of radiation or ) are displayed: So, if only the channel is set on the Measurement menu, only nuclides are displayed when you are going through the small nuclide table. From the nuclide table you select those nuclides you need most often (e.g. Net [cps], -tot, C-14, etc.). By pressing the Nuclides button one can switch directly from this preliminary selection during the measurement. 45

56 5. Contamination Measurements Each display shows the currently measured value, the unit of measurement and, on the left, the selected nuclide and the measurement mode. The measured value for the new setting is displayed virtually with no time delay whenever there is a change in display. In the counter/timer mode, the measurement must first be stopped for a nuclide change. The detector has to be held as closely as possible to the surface to be measured (be careful not to damage the foil!). Depending on the level of the count rate, in the counter/timer mode a different measurement duration and in the ratemeter mode a different time constant or preset accuracy has to be used to obtain a fairly low statistical error. Decreasing statistical fluctuations become apparent from the fact that the displayed measured values show less and less deviations. The stored background rate is automatically subtracted CPS Measurement Start the measurement by selecting the desired measurement mode (Ratemeter, Counter/Timer...) on the System Menu and then press ESC to go to the measurement menu. If gross or net [cps] is not yet set, select this setting from the small nuclide table. Press the Nuclides button repeatedly until Gross or Net is displayed in the second row of the display (see below). Display Net 2 nd measuring channel Figure 4.14: CPS measurement Press the Info softkey to view further information on the ongoing measurement Measurement of Area Activities Start the measurement by selecting the desired measurement mode (Ratemeter, Counter/Timer...) on the System Menu and then press ESC to go to the measurement menu. 46

57 5. Contamination Measurements In the Display Mode menu you can change the display layout. Then select the nuclide to be measured: - If two measuring channels are displayed, press the Nuclides key first. Then the function of the softkey changes. Using the keys and you can now set the and the nuclides separately. Figure 4.15: Nuclide selection with simultaneous / measurement In the selected measurement mode (Bq/cm²), the detected count rates (cps) are converted to area activities (Bq/cm²) using a calibration factor entered in the device. The previously saved background rate is automatically subtracted, so that the net area activities are displayed here. Press the Info softkey to view further information on the ongoing measurement. The Graph function allows you to present the change of the measured value over time graphically. The graph runs from right to left and you always see the values of the last 120 seconds. With Delete the graph can be reset and it starts all over again. In the counter/timer mode we get a new pixel in the graph for each elapsed cycle. Figure 4.16: Change in the -values over time displayed as a graph 47

58 5. Contamination Measurements Explanations on Raw Data and Calculated Units In this chapter you will learn to choose the appropriate measurement mode for each situation, and what differences there are between the individual modes: Net [cps] Net - counts per second In this measurement mode, the net count rate coming from the detector is displayed, provided that a stored background is available. In addition, the gross count rate can also be displayed. This measurement mode is always used to determine a general change of the degree of contamination or the radiation level or if you do not know which nuclide contains the contamination. Bq/cm² Area activities In this and the following measurement mode, the detector count rates (cps) are converted into area activities using a calibration factor stored in the device (Bq/cm²). The stored background rate is automatically subtracted. e.g. Beta sources (total) = β-tot -tot means "Beta total". In this case, the conversion factor does not refer to a specific radionuclide, e.g. iodine-131, but is based on the average factor of a nuclide mix which can typically be expected after a reactor accident. This measurement mode is used a) to check whether the limit values for surface contamination stipulated in regulations or provisions have been exceeded, and b) the contamination has been caused by a recent power plant accident and its composition is not known. e.g. Cs-137 (or another nuclide) In this measurement mode, the conversion factor is related to the surface activity of a particular nuclide. The nuclide can be retrieved from the built-in nuclide library. This measurement mode is used 48

59 5. Contamination Measurements a) to check whether the limit values stipulated in regulations or provisions have been exceeded, and b) the contamination has been caused by a well-known radionuclide. If you are dealing with a mixture of radionuclides and you know the individual nuclides, you can use a so-called reference nuclide which accounts for either the main portion of the mixture or is particularly dangerous (with fresh fission products, this will almost always be I-131). Caution! This measurement mode does not mean, however, that the monitor is able to measure the contamination of a radionuclide in a mixture deliberately and selectively. It only evaluates the contamination as if it were caused by the respective radionuclide. New nuclide It is possible to add new nuclides or nuclides that were not yet entered to the nuclide list. Go to the Nuclides menu and select Add. Then enter all parameters mentioned above, such as name, calibration factors, thresholds, etc. The new nuclide must be activated to view it in the small nuclide list. This measurement mode is used a) to measure a nuclide that is not included in the nuclide library. Prerequisite is the calibration of the device with an appropriate calibration source, or b) to measure a particular nuclide mix containing nuclides from the nuclide library. 5.3 Measured Result as a Function of the Contaminated Surface The calibration factors for the Bq/cm² display determined at the factory and stored in the LB 134 in the setting A-100 (according to DIN 25415) refer to calibration sources having the dimensions 10 cm x 10 cm and an activity certified by the German Calibration Service respectively in the setting ISO 7503 (according to DIN ISO ) refer to the active detector area and an surface emission rate certified by the German Calibration Service. Comparative measurements with other devices which also display in Bq/cm², therefore, will only lead to consistent results when these devices were also calibrated with such sources. So if you get other values from comparative measurements than those displayed by LB 134, please check 49

60 5. Contamination Measurements a) whether the same radionuclide has been set, and b) whether the source used for calibration meets the above mentioned requirements. When measuring area contaminations, the extent of the contamination relative to the standardized area of the calibration source of 100 cm² (in the setting A-100) also plays a role. For measurements according to 44 of the Radiation Protection Ordinance (Germany), the averaging area can be up to 300 cm². The measurement area of the probe LB 1342 is 118 mm x 145 mm (171 cm²) at a transmission of 80%. In the LB 1343 probe the active measurement area is 345 cm². For contaminations less than 100 cm² this averaging is done automatically due to the aforementioned calibration conditions. A contamination of, say, 10 Bq/cm², but an expansion of only 50 cm², is displayed as 5 Bq/cm² (distributed over 100 cm²) as a result of this averaging. However, if the extent of the contamination is greater than 100 cm², the monitor overevaluates: It shows at 10 Bq/cm², spread over 150 cm², for example, 15 Bq/cm². 5.4 Exceeding of Limit Values Any exceeding of user-defined limit values is indicated on the display by a flashing measured value ( or ). Moreover, an alarm signal is output (visual as flashing LED, audible as short alarm beep), if preset (see System menu: Parameter->Alarm). The alarm is displayed in any case, no matter which measurement mode you are in. Figure 4.17: Exceeding of limit values If the entrance window is defective (light enters the counting chamber) and the count rate is exceeded for a short time, the scintillation detector is turned off, i.e. the high voltage is turned off. In this case, the entrance window must be replaced. 50

61 6. Software Functions 6. Software Functions In this chapter you will find information on all measurement functions, parameters and service functions in the order they appear on the System Menu. It starts with the description of the actual measurement of contamination, activity or dose rate. For a detailed description of the software operation please refer to chapter 4 (how to select the System menu and menu items, editing, etc.). You have access to all menu items from the System Menu. See also Table 6.1. After start-up and configuration of the device, only those menu items appear for which the user has read or edit rights. The user rights are password protected and can be changed only by the device supervisor under the item Menus Enable. There, the rights: Off, Read only and Read and Edit can be assigned. Off means the menu does not appear in the menu list. Read only means you can view the parameters but you cannot edit them. Read and Edit means that you can also edit the parameters. Next, we will describe the measurement function. 6.1 Measurement of Contamination, Activity or Doserate After power-on or when you press the ESC key on the System Menu, the Measurement menu appears and in the Ratemeter or Search mode the measurement starts automatically in the preset measurement mode using the selected parameters. In the Counter/Timer mode, you have to press the Start button. The active measurement mode, the LB number of the probe and the current measurement results are displayed. Example in the Ratemeter mode: Press the double arrow key on the right to access more functions in the bottom line. 51

62 6. Software Functions System Menu Options Live Display Measurement Use Int. DR-Det. Background OFF, ON Start Measuring BG Alpha/ BG Beta-Gamma Meas. Time Autostart OFF, ON Ratemeter, Counter-Timer, Search Meas. Mode Meas. Parameters Meas. Time Cycles Avg. Mode Time Constant / Accuracy Sigma Factor Auto Save Auto Send Nuclides Nuclide List... Name Active Yes / No Radiation Type Mass Number Unit, etc.... Integral Reset Yes / No Display Mode α + β, α, β Memory Show Memory Delete Memory Memory USB Stick Para USB Stick USB Stick Para Memory Mode Finite memory or FIFO System Test Start Measuring Parameter: Meas. Time, Nuclide, Ref. Value, Max. Dev. Date/Time Language German / English Device Addr. 1 to 255 Calib. Type ISO , A-100 Backlight Dark, Medium, Bright Headphones / Relay Headphones or relays for alarm Power Supply Battery Type Battery or Accu Charge Mode Yes / No Charge Time in h Line Volt. in V Batt. Volt. in V Hardware Detector Type LB number Ser. No. Det. Ser. No. Device Ctrl. Volt. for ext. Probe in V Baud Rate Baud Key Sounds on / off Serial ready yes / no Vinculum Program. On / Off (only final test) Dead Time α and β channel Fail Time in s Fail Thr. in cps Detector Mode: α + β, only α, only β Transmission α Range upp. α and β channel Alarm Type Factory Defaults Yes / No Optical OFF, ON Acoustic OFF, ON Ticks -Ticks OFF, ON -Ticks OFF, ON Enable Menus Enter Password Background Meas. Mode Meas. Parameters Nuclides Integral Reset Display Mode Memory etc. Table 6.1 All menus at a glance 52

63 6. Software Functions If you press the double arrow key on the right once more, further functions appear in the bottom line. If you press this key once more, the first functions appear again (see first picture). The functions are explained in detail. Figure 6.1: Display in Ratemeter mode Nuclide Save Menu Mode Graph Select the desired nuclide or nuclides from the small nuclide table depending on the selected measuring channel. (The contents of the small nuclide table is selected on the Nuclides menu.) The nuclides can be selected during a measurement. If you are working with dose rate probes, the Measurement mode is displayed here and instead of nuclides you can select preset measurement types. Saves the measurement results of the stopped or completed measurement in the Counter/Timer mode. In the Ratemeter mode you can save the results any time. Go to the System Menu. Three functions can be selected: Ratemeter, Counter/Timer and Search which are selected here. Shows a graph of the measured values as a function of time. In the Ratemeter mode the seconds values are recorded from right to left. In the Counter/Timer mode, a dot is drawn from right to left at the end of each measurement. 120 dots max. are displayed. 53

64 6. Software Functions Reset Start Start/Stop Menu Info This button resets the Ratemeter parameters, such as min/max values, cycle storage time, smoothing filter parameters. Starts the integral calculation, summing up of the measured values; for dose rate it starts the dose calculation, start of the integral time. If the integration was stopped before, it will continue now. The integration will start all over again only after an integral reset (see chapter 6.8). Starts or stops a measurement in the Counter/Timer mode. The Ratemeter or the Search function run continuously, separate start of the measurement is not necessary. Return to the System Menu. Press this button briefly and repeatedly to view information on the running measurement. Additional information is displayed depending on the measurement mode, see chapter Description of the Individual System Menu Items The following four displays list all system menu items that are available in an alpha beta contamination probe. We will now describe these menus and sub-menus in detail. 54

65 6. Software Functions Figure 6.2: System menu for alpha-beta probe 6.3 Use Internal DR Detector If the checkbox to the right in this menu row is ticked, this means that the internal dose rate probe is used, even when the external probe is connected. When the cursor (left arrow) is already in this row, the internal probe can be enabled or disabled by pressing Enter. If it is not enabled, then the external probe is used (the X has been cleared). When not enabled, the power supply of the internal probe is turned off to save power. If the internal probe is disabled and no probe is connected, you will see the following display. na means that the internal probe is not turned on (not activated). Dr na Figure 6.3: Display with internal probe turned off and no external probe connected 6.4 Background The background menu depends on the type of probe that is connected. Basically, you can always enter the background; however, with some probes one cannot determine the background using the measurement function to be started here. For an alpha beta contamination probe there are two backgrounds that here are either determined through a background measurement and stored or, if they are already known, can be entered directly. 55

66 6. Software Functions The functions and settings are explained below: Figure 6.4: Background menu with options for the contamination probe The currently stored background is always subtracted from each measurement (in each measurement mode). Start measurement Starts the background measurement in one or both measuring channels simultaneously using the parameters defined on this page. The background can also be entered manually in cps in the row BG α or BG β, provided the Background menu is enabled for reading and editing. The following display appears after the start of the background measurement: Background measurement a) Ongoing measurement (after 32 seconds) b) Measurement stopped after 1:03 minutes Figure 6.5: Background measurement 56

67 6. Software Functions a) The info line can be used while a measurement is running to view the accuracy or the time and date. b) At the end of the measurement, the backgrounds ( and ) can be saved (Save button) and information on the measurement can be viewed (Info button). During a background measurement, the softkeys have the following functions: Save Start/Stop Esc Info This softkey is displayed only when the measurement has been completed. Press this button to store the measured background in the Background menu in the line BG α and BG β. Stop is displayed while a measurement is running, Start is displayed if a measurement has been stopped or completed. Return to the Background menu. Press this button repeatedly and briefly to view the following additional information: Accuracy Elapsed Measuring Time and Preset Time Date and Time Negative values For statistical reasons it may happen that the stored and subtracted background is greater than the currently measured count rate. Mathematically this results in negative count rates. Negative numbers are suppressed in order not to confuse the user (display zero). If the negative values are in fact only a result of statistical fluctuations, then the result will constantly vary around 0. That's a good sign indicating that the stored and the currently measured background coincide on the average. However, if the value is visible all the time, this indicates that the stored background is too high. In this case: Check the background and, where necessary, carry out a new measurement and store the new value! 57

68 6. Software Functions Measuring time [s] Enter the measuring time in seconds. It should be at least 60 seconds to obtain accurate measurement results. Note that the preset measuring time limits the background measurement, no matter what accuracy is reached! The actual measuring time can be viewed by pressing the Info button. It is stored internally and is taken into account in further calculations. The background should be measured daily or occasionally or it should be measured new and stored whenever changing the environment to avoid false values in the net result! The stored background is displayed in the Background menu. This value is subtracted from each subsequent sample measurement. Autostart Here the autostart function can be enabled (X) or disabled ( ). When the autostart function is enabled, a background measurement is carried out automatically using the preset parameters whenever the device is turned on. Upon completion of the background measurement (by manual stop or expiration of the measuring time), store the measured background by pressing the Save softkey. Only then you can start regular measurements (contamination, activity, dose rate) by exiting the Background menu and the System menu. Please note: If the autostart function is active, a measurement should be started only after saving and accepting the result of the current background measurement. BG / BG β The currently stored background is displayed. It can come from a background measurement (see above) or it can be entered manually. For other contamination probes you see here only BG [cps]. Manual change: After selecting this option, press the Enter key. Move the cursor with the button to the desired position and set the desired number by repeatedly pressing the key. If this is a multi-digit number, press the button to go to the next digit and set this digit as described above. Once the desired value has been entered, press the Enter key. Thus, the entered digit is stored as a new background. BG measuring time At the end of a background measurement, the measuring time is displayed in seconds. If you want to enter the backgrounds as values, you have to enter the associated measuring time here; otherwise the statistical error of the subsequent measurement results is calculated incorrectly. 58

69 6. Software Functions 6.5 Measurement Mode In this menu, you can select three different averaging methods for the measurement results: Counter/Timer, Ratemeter and Search Mode. The associated parameters are set in the Measurement Parameters menu. The selected averaging mode is retained even after the device has been powered off and on again. See chapter 1.6 for an explanation of the averaging method. Proceed as follows On the System Menu the currently set measurement mode is displayed next to the option Measurement mode. To change the setting, select the Measurement mode option ( ), and press the Enter key. Then, the current setting is marked by an. Press the key button repeatedly to scroll through the selectable measurement modes in cyclic order. Once the desired measurement mode is displayed, press the Enter key. The selected setting is accepted. Figure 6.6: Selecting the desired measurement mode 6.6 Measurement Parameters Ratemeter If you select the Ratemeter measurement mode, you will see the following options: 59

70 6. Software Functions Figure 6.7: Parameters for Ratemeter measurements Avg. Mode Time Const. Accuracy [%] Sigma Factor Cycle Time (s) Cycles Auto Save Auto Send Set the type of averaging. You can select Time Constant or Accuracy. Enter the desired time constant, i.e. the time to be used to smooth the measured values. With smaller time constants, the measurement is more sensitive and reacts more rapidly, but is less accurate. Default setting is 120 seconds. If the accuracy is defaulted, a time constant is determined from this accuracy and the actual count rate corresponding to that accuracy. Specifies the number of standard deviations which defines at which deviation of the currently measured value from the mean value the time constant will be reset to 1 second and then is increased by one each second until the above time constant is reached. (good for fast response of displayed value in case of fast changes of activity) In Ratemeter mode, the cycle time defines how often storage is performed or how many times the data are to be transferred via USB interface. The ratemeter continues to run uninterrupted. If you press the RESET button, the ratemeter is initialized. The cycle parameters for all measurement modes are defined in this menu: One defines whether the measurement is saved only once (setting: 1) the measurement is stored after each cycle (setting 0, = endless) a predefined number of cycles is to be stored (setting N, where N can be between 2 and 9999). Enable (X) or disable ( ) the automatic save function. Stored data can be viewed on the Memory menu either on the display or copied to a memory stick and transferred to a PC. The current saving process is displayed in the upper left corner of the display. Enable (X) or disable ( ) the automatic transfer function via USB to the PC. When enabled, the results are automatically transmitted every cycle time. 60

71 6. Software Functions Counter/Timer If you select the measurement mode Counter/Timer, you will see the following options: Display for alpha beta contamination probe. Display for dose rate probe. Figure 6.8: Parameters for a Counter/Timer measurement, for two different probes Measuring Time Cycles Preset Acc. (%) Auto Save Measuring time of a cycle in seconds. The cycle parameters for all measurement modes are defined in this menu: One defines whether the measurement is to be performed once (setting: 1) the measurement is to be repeatedly constantly (setting 0) a predefined number of cycles is to be performed (setting N, where N can be between 2 and 9999). Once the accuracy of the measurement is less than the preset accuracy, a measurement cycle is stopped even if the preset measuring time has not yet been reached. If there are two measuring channels (e.g. alpha and beta channel), the measurement cycle is stopped as soon as both accuracies are below the two preset accuracies. If you want to stop a measurement via the preset measuring time, you have to enter a very small value for the preset accuracy to make sure it will never be reached, for example, 0.01%. Enable (X) or disable ( ) the automatic save function. Stored data can be viewed on the Memory menu either on the display or 61

72 6. Software Functions copied to a memory stick and transferred to a PC. The current saving process is displayed in the upper left corner of the display. Auto Send Enable (X) or disable ( ) the automatic transfer function via USB to the PC. When enabled, the results are automatically transmitted every cycle time Search If you select the measurement mode Search, you will see the following options: Figure 6.9: Parameters for Search mode Cycle Time (s) Cycles Auto Save Auto send Same function as in Ratemeter Same function as in Ratemeter Same function as in Ratemeter Same function as in Ratemeter 6.7 Nuclides/Measurement Types Display of the Nuclides/Measurement Types Table with editing option. After selecting this menu option, the first 4 nuclides/measurement types of the nuclide/measurement type table are displayed. The cursor is at the top position. Briefly press the key to move the cursor down; to move the cursor up, you have to press this key longer. Briefly press the Pg up/pg down key to scroll one page forward in the nuclide table; to scroll back one page, you have to press this key longer. In this way, you can scroll through the entire nuclide table. Press the key to view new function keys: New, Edit and Delete, to define new nuclides, edit or delete existing nuclides. In an alpha beta probe, however, the first six entries cannot be deleted, in a doserate probe, the first two entries cannot be de- 62

73 6. Software Functions leted. The following three displays show the first 12 nuclides for an alpha beta contamination probe. Figure 6.10: The first twelve nuclide entries for alpha-beta probe The next two displays show examples of measurement types for a dose rate probe. Figure 6.11: The first eight nuclide entries for a doserate probe Contents of the nuclide/measurement type table The nuclide/measurement type table currently contains about 70 nuclides and 12 measurement types with calibration factors. Moreover, it includes a nuclide mix for alpha and beta sources 63

74 6. Software Functions "α-tot" and " -tot". In addition, it includes the units Net [cps] and Gross [cps] for alpha and beta-gamma SOURCES. The following information is included for each nuclide: name, active, radiation type, mass number, unit, two calibration factors A-100 (according to DIN 25415) and ISO (according to DIN ISO ), one alarm threshold for the measured value, one alarm threshold for the integral value, the unit for the integral value and the time base for the integral calculation that can be edited by the user. Figure 6.12: Nuclide parameters for contamination probe 64

75 6. Software Functions Figure 6.13: Measurement type parameters for a dose rate probe The following information is included for each measurement type: name, active, radiation type, the order in the list, unit, one calibration factor, one alarm threshold for the measured value, one alarm threshold for the integral value, the unit for the integral value and the time base for the integral calculation that can be edited by the user. Selection for small nuclide/ measurement type table Editing the nuclide table In the nuclide/measurement type table you can select individual nuclides / measurement types for the small nuclide / measurement type table (Measurement menu). To select a nuclide/measurement type, mark the menu item Active with an X by pressing the ENTER key. The selected nuclide / measurement type can then be set directly in a measurement. Press the Enter key again to clear the selection. Be careful when editing the nuclide table. The calibration factors have been determined correctly in the factory for all entries. The setting of the nuclide-specific alarm thresholds is important for the user to trigger audible and visual alarm signals when these thresholds are exceeded. Proceed as follows Move the cursor ( ) to the desired nuclide. Press the button to go to the Edit menu. Now press the Edit button. This will take you to the page on which the parameters for that nuclide/measurement type can be edited. Enter the desired values. Confirm your entry by briefly pressing the Enter key. Figure 6.14: Editing the nuclide parameters of C-11 65

76 6. Software Functions The parameters in detail: Name Active Radiation type Mass number Unit Nuclide name. Change the status to passive or active. Shows the type of radiation of the nuclide ( or or γ or n). Physical mass number of the nuclide or order of the measurement type (1, 2, 3, ) Unit of measurement, e.g. cps, Bq/cm², µsv/h, mrem/h etc. Calibration factor (A-100) Calibration factor according to DIN standard relative to an area of 100 cm². For gross or net, the calibration factor is always "1". The second calibration factor appears only for contamination probes; for all other probes there is only one calibration factor. Calibration factor (ISO) Alarm threshold Limit values Calibration factor according to DIN ISO standard. For gross or net, the calibration factor is always "1". The second calibration factor appears only for contamination probes; for all other probes there is only one calibration factor. An alarm threshold can be set for the individual nuclides/measurement types. If the stored alarm threshold is exceeded during a measurement, the measured values and the top LED start flashing and you will hear a permanent alarm, which will be turned off only when you quit the measurement mode or when the measured value has dropped below the alarm threshold. Moreover, the exceeding of the alarm threshold is also indicated on the bar graph: The percent indication is switched over using the factors 10, 100 and 1000, so that it is immediately apparent by which factor the entered threshold has been exceeded. Under the Radiation Protection Ordinance of August 1, 2001 in Germany the limit values for contaminations are nuclidespecific. In operational monitoring areas, these limit values are 10x higher than outside the monitored area. May be different in other countries. Examples for limit values outside monitored areas in Bq/cm²: C-14: 100 S-35: 100 Ca-45: 100 Fe-55: 100 Ni-63: 100 Tc-99: 10 Tl-201: 10 66

77 6. Software Functions Sr-90: 1 When the limit value is exceeded, measures have to be taken immediately to avoid the spreading of the contamination (German Radiation Protection Ordinance 44). Moreover, the measured value has to be recorded in this case. Integral threshold Integral unit Time base Measured values are integrated each second during the measurement. For example, the summation of the dose rate (µsv/h) results in the dose µsv. For contamination probes we can integrate the net values (cps), and then we would get counts. The value obtained is compared with the integral threshold and an alarm message is generated when this threshold is exceeded. Here the unit of the integral value is entered as text, e.g. µsv, mrem, counts or pulses. During the measurement, the current integral value or the dose and the integration time elapsed until then is determined every second through addition. If you have selected the unit counts per second (cps), you get counts through adding up (counts). If you have selected the unit µsv/h, as for the dose rate, then the time base is not seconds but hours. Therefore, before the addition, the value must be divided by 3600, since every second is added up. This divisor is selected correctly when entering the integral calculation time or the time base. You can select s, m or h. 6.8 Integral Reset The integral values / dose and the associated integral time are reset. Figure 6.15: Resetting the integral values and integral time 67

78 6. Software Functions 6.9 Display Mode You can select one of three possible display modes for a connected alpha beta contamination probe. Figure 6.16: Selection options in the display mode In the first case, the alpha and beta channel are shown the same size. Figure 6.17: Display mode α + β In the second case, the alpha channel result is displayed large and the result of the beta channel will appear in the info line. Figure 6.18: Display mode α In the third case, the beta channel result is displayed large and the result of the alpha channel will appear in the info line. Figure 6.19: Display mode β 68

79 6. Software Functions 6.10 Upload and Download Memory and Parameters The following storage operations and parameters up- and downloads can be performed with this menu item: The results entered in the memory can be displayed sequentially on the display. The entire memory can be erased with a single command. The entire memory content can be transferred to a USB stick and can be evaluated on a PC. Therefore the Berthold PC program for the LB 134 is necessary. All parameters can be written to the USB stick with a single command. All parameters that were previously written to the USB stick can be transferred to another LB 134. With the Berthold PC program LB 134, the parameters can be written to the USB stick from a file and then transferred to a LB 134 with the stick. On the other hand, the parameters on the USB stick can be read and archived by this PC program. The data memory can be operated in two different modes. On the one hand, as a finite memory with a current length of 2400 entries. On the other hand, as a FIFO memory; once the memory is full, the oldest entry is overwritten by the new data. For this mode, there is a write pointer and a read pointer for reading the FIFO. The F²C protocol is used for communication. Both interfaces, USB and RS485, have access to the FIFO with this protocol. In general, this type of communication with the FIFO is performed via the RS485 digital data network. Therefore, there is only one common read pointer. The storage of the measured values takes place either via the corresponding softkey or through the automatic storage function (see Autosave menu) When you save the measurement, the number under which the measured values are stored in memory is displayed on the top left. 69

80 6. Software Functions The measurements are stored in the order they have been saved in the RAM memory. The pages are numbered consecutively; one page is used for each measured value. Figure 6.20: Options on the Memory menu Show Memory Shows the current memory contents on the display. Memory contents of alpha, beta contamination probe in Ratemeter mode. Memory contents of alpha, beta contamination probe in Counter/Timer mode Memory contents of dose rate probe in Ratemeter mode 70

81 6. Software Functions Memory contents of dose rate probe in Counter/Timer mode Figure 6.21: Examples for Show Memory menu To go to the desired results, you have the following options: key: short push: Next measurement key: long push: Back one measurement Pg key: short push: Next page Pg key: long push: Back one page If you save a cyclical measurement, you will see in the first line, for example, (# 2/3) of the current cycle / preset total cycles. With two measuring channels, the integration time appears twice, but is always the same size. Delete Memory Memory USB Stick Para USB Stick USB Stick Para Clears the entire memory contents! Writes the entire memory contents to the USB stick. The display shows: Write data to USB stick successful. Writes all parameters to the USB stick. The display shows: Write data to USB stick successful. Writes all parameters from the USB Stick to the LB134. The display shows: Write data to Memory successful. Display of memory contents Example contamination Example dose rate Line 1: No./Qty., Cycle N of M, LB-number Line 2: Date, Time, RM/CT, Meas. time s Line 3: Radiation type, Nuclide, Measured value1, Unit1, accuracy1 % Line 4: Radiation type, Integral, I.value1, I.unit1, Integration time h Line 5: Radiation type, Nuclide, Measured value2, Unit1, accuracy 2 % Line 6: Radiation type, Integral, I.value2, I.unit2, Integration time h Line 1: No./Qty., Cycle N of M, LB-number Line 2: Date, Time, RM/CT, Meas. time s Line 3: Radiation type, Meas. type, Measured value, Unit, accuracy % Line 4: Radiation type, Integral, I.value, I.unit, Integration time h 71

82 6. Software Functions 6.11 Parameters The following device parameters are set on this menu: Figure 6.29: Menu items under Parameters Date/Time Here you can check and set the date and time. This time information is used when storing the measured values. If the memory with the time information is deleted (e.g. by storing the LB 134 without batteries), the date and time will be automatically queried when the device is turned on. The entry is made as shown below: DD.MM.YYYY or HH:MM:SS. Figure 6.30: Entering the date and time 72

83 6. Software Functions Language This menu item allows you to choose German or English as user interface language Device Address Enter a device address between 1 and 255 for networking with the RS485 bus. If the LB 134 receives a command via the USB or RS485 interface, the address contained therein must match the above address for the command to be processed Calibration Type You can select calibration sets in accordance with DIN ISO and DIN (A-100). Both types of calibration are described in detail in chapter Light Off [min] Here you can enter the automatic switch-off time for the display backlight. If the backlight is turned on, it will be switched off automatically when the time preset here is over Backlight Here you can enter the brightness for the display backlight. You can choose Bright, Medium and Dark. If no key is pressed for 60 seconds, the display light goes out automatically Headphones/Relay Here you can choose whether to connect a relay to the left 6 pin Fischer jack or a headset to the jack plug socket (3.5 mm diameter). Default is the headset. An external low-voltage relay can be connected, which is enabled when an alarm limit in the first or second channel is exceeded. In the event of an alarm, this could be used, for example, to operate an external signal lamp. The relay can be supplied with 5V on pin 2 of the Fischer jack, the other terminal of the relay passes through pin 1 to a transistor, which is internally protected by a diode (US1K). The maximum current must not exceed 50 ma. The relay can also be supplied with an external 73

84 6. Software Functions voltage of +12V; in this case, the ground of the external supply must be connected to pin 3 (ground). The second connection goes again to pin 1. Again, the maximum current must be less than 50 ma Power Supply Depending on the type of battery, the following parameters can be set: When Battery has been set, the following display appears: Figure 6.31: Display when working with batteries When Accu has been set, the following display appears: Figure 6.32: Display when working with rechargeable batteries Battery Type: Battery or Accu Here you can specify whether the LB 134 should work in the battery or rechargeable battery mode. If Accu is set, the parameters Charge Mode and Charge Time are displayed as well. Note: The rechargeable batteries in the device can be charged automatically with the setting Accu when the device is placed in the wall bracket connected to the power supply (the device turns on automatically), or 74

85 6. Software Functions the power supply is connected directly to the device and the LB 134 is turned on. To this end, the Charge Mode must be set to On (X). The menu item Charge Time allows you to limit the duration of the charging process to 12 hours max. to prevent overcharging. Taking the device out of the wall bracket and replacing it later, or switching the device off and then on again results in a restart of the charging process, provided the charge mode is active. No charge process is started if the charge is at 80% or higher. Caution! The charge function is active only when the device is turned on! Charge Mode Charge Time Line Voltage Battery Voltage Here you can set the charge mode (X). Only with setting Accu. Enter the duration of the charge process. Only with setting Accu. Maximum 12 hours. The current line voltage in volts is displayed. This value is determined and output by the device. Here the current battery voltage in volts (or rechargeable battery voltage) is displayed. Please take into account that the battery voltage indication is not correct as long as line voltage is being supplied, as the battery is not in use during this time Hardware The Hardware menu includes the following parameters: 75

86 6. Software Functions Figure 6.33: Hardware parameters In a single-channel probe, e.g. a dose rate probe, the parameters for the second channel do not appear and the table is slightly shorter. The parameters in detail: Detector Type: The LB number of the detector used is displayed here; it may also be the internal dose rate probe (LB 1346). This parameter cannot be edited. Ser. No. Detector: The serial number of the detector is entered at the factory or taken from the probe. Ser. No. Device: The serial number of the LB 134 device is entered at the factory; it cannot be edited. Control Voltage (V): For many probes, the control voltage is not needed for the probe high voltage, with a few exceptions. Normally, the value is set to 2.5V. 76

87 6. Software Functions Baud Rate: The baud rate for the USB interface is always baud and cannot be changed. The baud rate for the RS485 interface can be set between 2400 and and depends on the length of the data cable and the number of connected devices. The shorter the line and the less devices are connected, the higher may be the baud rate. The other parameters are 8 data bits, 1 start bit, 1 stop bit and no parity. Key Sounds: When this function is enabled, you hear a short beep whenever a key is pressed. Serial ready: This parameter must always be enabled for data communication. If this parameter is disabled, then the processor goes to sleep every second for about 700 ms and the battery life of the battery/rechargeable batteries is significantly prolonged. Vinculum Prog On: To program the USB Vinculum chip in the final testing in the factory, this parameter must be enabled and then disabled again for the normal measurement operation. Dead Time: The dead time of the detectors for the individual channels in microseconds are set at the factory. Fail Time / Fail Threshold: Each detector has its own fail threshold and fail time because the backgrounds are very different and we do not want to get any false alarms, but on the other hand, we would like to get failure messages as quickly as possible. For contamination probes, failure monitoring always refers to the beta channel. During a normal measurement, a counter/timer measurement monitoring whether the probe count rate has fallen below the fail threshold is constantly running in the background. This test 77

88 6. Software Functions is carried out at the end of fail time and, where appropriate, the error message "Failure" is output. Then this measurement will start new. See section: 1.7 for information on how to calculate the values. Detector Mode: (Only for alpha beta contamination probes) Three modes can be used for a detector with simultaneous alpha/ beta measurement: Alpha/Beta simultaneously Only alpha device Only beta device If you select alpha only or beta only, the device behaves as if it were measuring only alphas or only betas. The results of the other type of radiation don t appear. With simultaneous alpha/beta measurement one can choose three display variants: Alpha and beta values displayed large, alpha values large and beta values on the info bar, beta values large and alpha values on the info bar. Transmissions for alpha and beta channel Display or entry of a factor that takes into account the attenuation through the grid. The entry is made separately for and. Parameter has no influence to cps values. Upper measuring range Here, the upper limit value is specified for the allowable measuring ranges of the probes. When exceeding the upper limit, OVF is displayed instead of the measurement result. In this case, the integral is stopped Factory setting All parameters can be reset to factory settings. This function clears all user-defined settings Alarm Type Here you can set whether the alarm is to be triggered upon exceeding of the threshold or if the alarm is to be indicated visually only through the upper red LED. Optical and acoustic alarm can also be set at the same time. 78

89 6. Software Functions Figure 6.34 Alarm settings If the alarm is set to Acoustic or Optical/Acoustic, you will hear, in addition to the visual alarm, an acoustic signal when the threshold is exceeded. The respective threshold is stored specific to the nuclide or specific to the measurement mode in the nuclide/measurement type table and can be edited Ticks Here the measuring channel (radiation type) can be set in which acoustic ticks are to be heard; for an alpha beta contamination probe there are two entries. For a dose rate probe, only one channel can be activated. Figure 6.35: Selection of measuring channel for acoustic indication of individual events 79

90 6. Software Functions 6.14 Enable Menus To simplify handling, the device allows you to hide single or all menus for the measurement operation. On the other hand, the menus can be enabled to view only the parameters or to view and edit the parameters. Figure 6.36: Menus to enable functions Figure 6.37: Selection rights for the menus The device supervisor should carefully consider which menu mode is suitable for his area of work and which menu items should be accessible to other members of staff. A password is required to enable the menu. Upon delivery, the password is 0. At this point, the password can be changed and is still valid after switching off the device. 80

91 7. Probes for the LB Probes for the LB Internal Dose rate Probe The integrated gamma dose rate probe is a Geiger-Müller counter tube and is suitable for the low dose rate range from 0.1 µsv/h to 20 msv/h and for an energy range from 50 to 1300 kev. Calibration factor: µsv/h/cps, intrinsic background: 0.07 cps. The probe is calibrated to the H*(10) standard (ambient equivalent dose rate). To extend the life of the batteries/rechargeable batteries, the power supply of the internal probe is switched off in the menu when the probe is not in use. 7.2 Scintillator Probes with ZnS for Contamination Measurements In this chapter we will describe the Berthold scintillation probes designed for the measurement of alpha, beta and gamma contamination in detail. The principle of operation of scintillation counters In conventional scintillation counters, the radiation to be measured hits one or several scintillator layers. The resulting light flashes are passed on directly, or bundled by a suitable reflector, to the photomultiplier. The current state of the art Up to now, sandwich detectors consisting of two layers were used to measure alpha, beta and gamma radiation: ZnS for the alpha radiation and plastic scintillators for beta and gamma radiation, with the ZnS layer facing the sample. The disadvantages of this method are the low sensitivity for low-energy beta radiation, which must penetrate the ZnS layer, and a poor discrimination between types of radiation (strong spillover effects in the beta channel), and high manufacturing costs. Moreover, with smaller beta energies, such as C-14, these detectors show a higher position dependence through the detector surface. New measurement method by BERTHOLD TECHNOLOGIES Contamination detectors with ZnS scintillators use a single scintillator made of zinc sulfide (ZnS) to measure the radioactivity. The radiation to be measured strikes the scintillator. The resulting flashes of light are conducted by a suitable reflector to a photomultiplier with a suitable preamplifier and discriminator stage and measured. 81

92 7. Probes for the LB 134 Using special evaluation and correlation circuits, the individual types of radiation such as alpha and beta/gamma/x-ray radiation are distinguished, separated and measured simultaneously (patented by BERTHOLD TECHNOLOGIES). Part of the spillover of alpha particles into the beta channel is corrected by software. The advantages of this method are therefore: high measuring accuracy precise distinction of radiation types high sensitivity even at low energies low costs for the scintillator, and ease of maintenance. Results can be displayed either as a count rate (cps = counts per second) or as area activities (Bq/cm²). A metal grid protects the entrance window of the detector against damage. Currently, two scintillator probes are available: LB 1342 with 170 cm² surface and LB 1343 with 345 cm² surface. The patented correlation method allows to measure alpha and beta radiation separately and simultaneously, without any additional plastic scintillator, and with good efficiency and low local variation. The temperature dependence in the range -20 C to 40 C is only about %. The dynamic range of the beta radiation is 0-50,000 cps and for alpha radiation 0-5,000 cps. Figure 7.1: LB 1342, scintillation probe with 170 cm² (LB 1341, Xe gas probe in the same enclosure) 82

93 7. Probes for the LB 134 Figure 7.2: LB 1343, scintillation probe with 345 cm² The scintillator is applied on a transparent carrier. The foil is stretched over a frame and protected by a metal grid. The detector is fixed to the underside of the cover with four screws. The frame with foil can easily be exchanged. The radiation entrance window can be protected by a metal protection plate. The reflector and the photomultiplier are located in the case, directly behind the scintillator. The enclosure also accommodates the electronics with evaluation and correlation circuit. The associated high-voltage is already set at the factory. A service adapter is required to check and change the high voltage; this work must be carried out by experienced service personnel Cleaning the Detector Window of Contamination Probes with Scintillator The window foil of the detector is sensitive to mechanical damage. It is therefore protected by a protective grid. However, everything should be done to avoid destruction of the window foil (sharp objects, measurement on stubble fields, rose bushes and cat's paws!). For easy cleaning of a dirty window foil, you can take off the outer protective grid after cautiously loosening the Phillips screws. Carefully clean the detector window foil with a soft brush (dust) or with alcohol or detergent solution. Then dry it using a hairdryer that must not be too hot. When you re-insert the protective grid, please be careful not to damage the foil with the screws or the screwdriver! 83

94 7. Probes for the LB Changing the Window Foil of Contamination Probes with Scintillator A damaged detector window foil can easily be replaced by the user. BERTHOLD TECHNOLOGIES supplies a foil stretched over a frame as spare part. When replacing the foil, make sure that the exchange takes place in a dry and dust-free place, moisture or dirt cannot penetrate into the gap during the exchange! the frame is replaced in semi-darkness, as the photomultiplier and the scintillator are sensitive to light. Do not work with the device for 12 hours to allow the phosphorescence to decay. Proceed as follows Change the foil in a darkened room (semi-darkness), as the photomultiplier and the scintillator will be exposed to light in the course of this process. Turn device off and, if necessary, pull the power cord. Place the device with the detector facing up onto a solid, clean support. Open the 4 Phillips screws holding the protective grid. Take off the protective grid. Remove the frame with foil. Insert the new frame with the foil such that the sealing lip sits perfectly to rule out any incidence of light. Attach protective grid again and fix it with the 4 Phillips screws. Wait 12 hours before you start working with the device to allow the phosphorescence radiation to decay. 84

95 7. Probes for the LB 134 Technical data: Sensitive detector area Entrance window Geometric transmission LB 1342:118mm x 145mm, 170 cm² LB 1343: 150 mm x 230 mm, 300 cm² Layer thickness: 6um Weight per unit area: 0.4 mg/cm² 80% Background Sensitivity to 1 µsv/h external gamma radiation (Cs 137) LB 1342: Alpha channel: approx. 0.1cps, beta channel: approx. 10cps LB 1343: Alpha channel: approx. 0.1cps, beta channel: approx. 15cps Alpha channel: not detectable Beta channel: < 100cps Spillover Alpha into beta channel (Po-210): < 20% Measuring range (linearity deviation error < 10%) Local variation Responsiveness Temperature range Protection type Overrange indication Light-proof/ Entrance window External magnetic fields Beta into alpha channel (Sr-90): < 2*10-5 Alpha channel: cps Beta channel: cps (for alpha channel < 750cps) Both channels: 20% Temperature range operation: (no condensation) -20 C C Stability of background over T-range: 10% Temperature range storage: IP53 β: >50000cps Overrange Indication α: >5000cps Overrange Indication Sunlight Close to PC monitor <10cps -40 C C no visible influences 85

96 7. Probes for the LB Contamination Probes LB 1231 and LB 1233 Two different hand probes as proportional counters are available for contamination measurements: 1. LB 1231 with beta-gamma-xenon detector LB LB 1233 with alpha-beta-p10 gas flow counter tubes LB 6359 The LB 1231 probe with its entrance window made of a very thin titanium foil can only measure beta/gamma radiation, the LB 1233 with its very thin entrance window made of a Mylar foil can in addition measure alpha radiation. Design of the hand probes Protective case with exchangeable detector: The proportional counter tube is fixed to the protective case with handle (hood) by means of snap locks (Figure 7.3). Figure 7.3: Probe LB1231 The hood incorporates a small printed circuit board (Figure 7.4) for coding the connected detector. 86

97 7. Probes for the LB 134 Figure 7.4: Basic assembly of the contamination probes, the probe can be connected to the UMO LB 123 and also to the LB 134. A foam rubber edge between case and detector protects the electronics of the hand probe from humidity and water. The 8- pin cable connection from the basic unit LB 134 is waterproof. The protective case accommodates an electronic board (contamination probe adapter) which is connected to the respective counter tube via a flat ribbon cable and serves to identify the detectors. The connected probe type is transferred to the software program in the LB 134 and there it activates the respective parameters and calibration factors. Figure 7.5: Protective case (bottom view) 87

98 7. Probes for the LB 134 Both counter tubes consist of a gas-filled counting chamber with counting wires. The counter tubes incorporate the necessary electronics such as amplifier and high voltage generator; therefore, the plug-in connection between the case (hood) and the detector does not carry any high voltage, so there is no hazard in touching it. The respective operating voltage and the high voltage values for plateau measurements are set to the optimum value for each counter tube at the factory. Operating point for 2 contamination probes Detector LB 1231 LB 1233 (Xenon) (P10 Gas) Beta HV 1850 V 1800 V Alpha HV V A service adapter is required to check and change the high voltage; this work must be carried out by experienced service personnel LB 1233 with Alpha-Beta P10 Counter Tube LB 6359 and Refill Station This counter tube is designed as follows: Electronic part as an attachment to the counting chamber, the counting chamber with counting wires, the replaceable window foil (metallized plastic on both sides, 0.3 mg/cm 2 ) and the mesh grid frame. This detector can be connected to a local or central P10 gas supply. The detector is automatically refilled and flushed when it is placed into the wall holder. Figure 7.6: Wall bracket for LB

99 7. Probes for the LB 134 A P10-gas cylinder (local) with double pressure reducer or a central P10 gas supply can be used to flush and fill the detector. The P10 gas is a gas mixture consisting of 90% argon and 10% methane. A pre-connected pressure regulator or a needle valve should be used for the central gas supply. The maximum flow rate should not exceed 100 cm³/min! Gas is supplied and drained via 2 self-closing valves each at the wall bracket and on the rear of the counter tube. Place the hand-held probe into the wall bracket (see Figure 7.6) such that the measuring area of the counter tube is facing you. Make sure that the valves are pushed into each other (at the end you have to overcome a slight resistance) until they fit together perfectly. Thus, the valves will catch and open: P10 gas flows into the detector and exits the counter tube again as soon as an adequate overpressure has built up. The gas exits via a rotameter which allows you to set the gas flow to an adequate rate (see Figure 7.7). The rotameter indicates a flow from 0 to 300 cm³/min on a scale from 0 to 30 (multiplication factor 10). Do not use a higher flow rate than 100 cm³/min to avoid damage to the window foil! Figure 7.7: Function of the P10 gas refill station The detector can be flushed or refilled in the idle position; no extra flush-cycle is required when using it as a stationary instrument. 89

100 7. Probes for the LB 134 All valves close automatically when the detector is lifted off the bracket; this stops the gas supply and keeps the P10 gas in the counting chamber. The operation life after filling or flushing is at least 8 hours with a loss in efficiency of less than 5 %. See also Figure 7.8 which shows the efficiency of a counter tube filled with P10 gas over the course of 3 days. Efficacy of the P10 flow-through counter tube as a function of time. The following diagram shows the efficiency after a counter tube filling with P10 gas, for alpha and also for beta sources, as a function of the time. The average loss in efficiency for beta sources is 0.1% / h. The average loss in efficiency for alpha sources is 0.05 % / h. The diagram illustrates that measurements over 8 hours are easily possible with one counter tube filling with less than 5% loss in efficiency. Figure 7.8: Efficiency of a counter tube filled with P10 gas as a function of time Commissioning of the alpha-beta detector with P10 gas supply 1. First, unscrew the valve opener (counter-clockwise) from one of the two valves of the P10 flow-through counter tube. The valve opener, a screw with a borehole, ensures that no over- or under-pressure builds up in the detector during transport which may damage the detector foil. Keep the 90

101 7. Probes for the LB 134 valve opener in a safe place and use it for transportation or storage. 2. Using the screws and dowels supplied with the instrument, install the wall bracket for the detector LB 6359 on a vertical wall in a convenient height. If you intend to use the monitor not just for field measurements but also as a semi-stationary instrument for measurement of the hands, you should install the wall bracket in a higher position, so that you can easily place your hand from above onto the measuring area of the counter tube. 3. Connecting the gas supply When using P10 gas bottles, first install a double pressure reducer on the gas bottle; make sure the pressure reducer is closed. When the instrument is connected to the central P10 gas supply, you need a pressure reducer or a needle valve which has to be closed during start-up. 4. Slip one end of the supplied PVC hose over the left valve nozzle of the wall bracket and connect the other end to your gas source (pressure reducer of gas bottle or central gas supply system) (see Figure 7.7). 5. Connect the outlet valve with the rotameter. 6. Attach another piece of hose to the rotameter output for the gas outlet. Its length should not exceed 6 m. 7. Place the hand probe into the wall bracket such that the measuring area of the detector is facing you and that you can place your hand from above onto the counter tube. Insert the hand probe so far that the valves are pushed into each other (at the end you have to overcome a slight resistance) until they fit together perfectly (visual check!). Thus, the self-closing valves on the wall bracket and the detector are firmly connected with each other. 8. Slowly open the gas flow regulator to let the gas flow through the detector as illustrated in Figure Wait for the rotameter to react to the gas flow before increasing the flow rate. 10. Gradually open the regulator so much that you get a flow rate between 70 and 100 cm³/min (i.e. the indicator on the rotameter should be between 5 and 10; "10" corresponds to 100 cm³/min). After about 15 minutes the detector is flushed 91

102 7. Probes for the LB 134 and ready for operation (operation time at least 8 hours with a loss in efficiency of less than 5 %). Replacing the window foil of αβcounter tubes A spare foil on a frame is standard accessory for this counter tube. Other foil frames can be provided by the manufacturer. 1. To change the window foil frame, place the hand probe with the grid facing up on a clean, not too smooth surface (rubber mat, towel) to secure it against slipping during work. 2. Carefully loosen and remove the 12 Phillips screws on alternative sides using the screwdriver (accessory). 3. First, remove the outer frame with the dense mesh screen and then lift off the square screen frame onto which the foil is glued (see Figure 7.9). Do not pull the rubber seal ring out of the groove and do not damage it! 4. Check if all 6 counting wires inside the counter are stretched tight and show any sign of damage. Otherwise, return the counter tube to the manufacturer for repair. 5. Inspect the new foil to verify that it is not damaged. Prevent penetration of dust, lints, small particles, etc. into the open counter tube! 6. Attach the square screen frame with the foil facing down, then the frame with the mesh screen, reinsert the screws loosely and tighten them alternatingly (see Figure 7.9), 7. Then place the P10 counter tube for flushing into the refill station. While flushing the counter tube, the foil must noticeable bulge out and stay that way for some time; otherwise it is not tight. Check and, if necessary, reassemble it again! 92

103 7. Probes for the LB 134 Figure 7.9: Assembly of counter tube window LB 1231 with Beta-Gamma Counter Tube LB 6357 This counter tube is filled with Xenon and tightly sealed. Neither refilling nor flushing is required; therefore, this counter tube does not include any refill nozzles or valves. The Xenon counter tube for the measurement of beta and gamma radiation cannot be opened by the user. The window foil (5 mg/cm² Titan foil) can only be replaced by Berthold. However, the mesh grid frame can be removed to clean the foil. The beta-gamma counter tube may also be inserted into a wall bracket for semi-stationary operation Counter Tube Change The counter tube attached to the hand probe case by snap locks can easily be changed without any tools. A counter tube must be replaced if you want to switch from beta-gamma to alpha-beta measurements and vice versa. The sealed Xenon-filled counter tube LB 6357 is used for betagamma measurements. The P-10 flow-through counter tube LB 6359 is used for alpha-beta measurements. A counter tube change is also required when a defective counter tube must be replaced by a new one. When replacing counter tubes, please make sure that the LB134 is off the foam rubber edge is not damaged the replacement takes place in a dry and clean environment and that under no circumstances moisture or dirt can penetrate into the gap! Proceed as follows to replace the counter tube 93

104 7. Probes for the LB Switch the LB 134 off. 2. Place the hand probe with the counter tube facing up onto a solid, clean support. 3. Open both snap locks. 4. Carefully lift off the counter tube. 5. Pull the connector from the hood at the respective flap. 6. Slip on connector of new counter tube, check if it is properly seated; insert nose of plug into groove of socket! 7. Carefully install counter tube; do not twist or jam the counter tube cable. 8. Close snap locks without force. After power on, the LB 134 microprocessor identifies the connected probe and sets its program and all calibration factors, alarm thresholds, etc. accordingly. Caution! Never open a snap lock before you have placed the instrument on a firm support! Otherwise, the counter tube may fall down and/or rupture the counter tube cable. 7.4 Dose Rate Probe LB 1236-H10 The probe LB 1236-H10 with energy compensated proportional counter tube (50 nsv/h 10 msv/h) is available for gamma dose rate measurements with external probe. It consists of a preamplifier/hv generator in a cylindrical case, which also serves as a handle, and the firmly installed counter tube. For dose rate measurements we are interested in the effect of radiation, i.e. the ambient equivalent dose rate and not the number of counts. Accordingly, these counter tubes are equipped with a sophisticated energy filter system (consisting of different materials). The exactly calculated construction of the energy compensation filter system ensures that the count rates triggered in the proportional counter tube are largely independent of the energy of the gamma radiation. The unit of the ambient dose equivalent rate is μsv/h. The unit of the ambient dose equivalent (integrated dose rate) is μsv (in USA usually mrem). The highest sensitivity of these counter tubes is perpendicular to the longitudinal axis. The center of the active area is marked by a blue ring on the probe case. Due to this quench, the counter tube should always be held vertical or transverse to the radiation incident direction. 94

105 7. Probes for the LB 134 Figure 7.10: Dose rate probe LB 1236-H10 The detector background is determined at the factory for each probe and can be taken from the supplied data sheet. The detector background values are entered in the Background submenu. Connect the detector with the 8-pin connector Fischer to the turned off LB 134. After power on of the LB 134, the connected detector is checked and identified by the software, and the respective parameters are loaded. If there is a detector failure (defect), the entire probe has to be replaced. The counter tubes cannot be replaced by the customer, but only by BERTHOLD service technicians. Technical data of the probe LB 1236-H10 Calibration factor μsv/h/cps Intrinsic background cps < 0,1 cps Nominal operating ranges probe LB 1236-H10 Parameter Range Max. Deviation Energy of gammas 30 kev 1,3 MeV ± 30% Preferred Direction Direction of incoming radiation Ambient Temperature Vertical to counter axis ± 45 to main radiation direction, blue ring around probe ± 20% -10 to +60 C ± 20% 95

106 7. Probes for the LB 134 Relative Humidity 20 to 95 % ± 20% Pressure range hpa ± 5% Table 7.1: Nominal operating ranges of LB 1236-H10, tested by the PTB in Braunschweig 7.5 Neutron Dose Rate Probe LB 6411 The LB 6411 neutron probe is designed for measurement of the ambient equivalent dose of neutron radiation as recommended by the International Commission on Radiological Protection ICRP of It was developed within the framework of a technology transfer project supported by the Department of Dosimetry of the Research Center Karlsruhe (KIT). The probe was optimized with respect to the energy response in accordance with the new equivalent dose conversion factors by ICRP 60. The LB 6411 neutron probe can be used both as a portable monitor and as a stationary measuring device. Major areas of application are in the nuclear field in reactors and the nuclear fuel cycle, in the field of research in accelerators and in the industrial sector in the use of neutron sources. Figure 7.12: Neutron Dose rate Probe LB 6411 The LB 6411 probe consists of a moderator sphere made of PE with a composite 3 He recoil proton counter tube at its center. The probe also includes the high voltage supply and a preamplifier. It can be connected directly to the LB 134 UMo II. In the energy range between 1 and 10 MeV the sensitivity is about 3 counts per nsv. Measuring range For 0.1 µsv/h the count rate related to a neutron energy in the range of 3 MeV is about 0.1 cps. At about 0.1 µsv/h ambient 96

107 7. Probes for the LB 134 level, the extremely low background of 0.05 cps permits reliable measurements of 0.1 µsv/h. The upper limit of the measuring range is 100 msv/h. Technical data: Unit of measurement: Ambient dose equivalent rate H*(10) Measuring range: 30 nsv/h to 100 msv/h Sensitivity: 2.83 counts per nsv or 0.79 cps per µsv/h Background: 0.05 cps Neutron energy range: Thermal to 20 MeV Energy dependency: in the range from 50 kev to 10 MeV ± 30% γ-sensitivity: <40 µsv/h up to to 100 msv/h, Cs-137 gamma field Temperature range: -10 to 50 C 7.6 Neutron Survey Meter LB 6414 The LB 6414 is a portable survey monitor for neutron radiation with extremely high sensitivity. The energy-dependent response probability is optimized for fission neutrons. There are many interesting applications, in particular the search for plutonium. Figure 7.13: Neutron Survey Meter LB 6414 The probe is particularly suitable to prevent illegal transportation of plutonium across borders or in airports. The following table shows the detection limit at 1m distance from the source: Measuring time Ex-weapons plutonium Reactor plutonium 1 s 303 g 67 g 10 s 47 g 10 g 100 s 12 g 2.6 g 97

108 7. Probes for the LB 134 Technical data Neutron detector: Electronics: Fluence Response: Detection limit: Neutron energy: Pu-240 equivalent: Mass response: Ambient dose equivalent response to H*(10): Dimensions: Weight: Typical background: 3 He proportional counter tube in PE Moderator Preamplifier, discriminator, high-voltage 26.4 cm 2 for fission neutrons 10.7 cm 2 for Am-Be 75 g ex-weapons plutonium in 5s at 1m distance (confidence interval 95%) Optimized for 10 to 1000 kev energy range 0.2 cps per g of Pu-240 in 1 m distance 27 counts/nsv or 0.13 μsv/h per cps for Am-Be source 68 counts/nsv or 0.05 μsv/h per cps for Cf-252 source 310 mm x 180 mm x 130 mm (LxWxH) 3850 g 0.06 cps 7.7 Nal Scintillation Counter Probe LB 1234 The NaI Scintillation Counter Probe LB 1234 is offering a high γ-sensitivity in the energy range between 25 kev and 2 MeV. This makes it the ideal device to search for and rapidly detect radioactive sources in radiation protection, in industry, in nuclear medicine, in the laboratory and at authorities. Typical applications are in the transport control, waste monitoring, border and baggage check, the control of scrap metal, the localization of contamination or the activity measurement. The universal battery-powered monitor LB 134 with data storage and adjustable alarm is used as measuring and display system. 98

109 7. Probes for the LB 134 Figure 7.14: NaI Scintillation Probe LB1234 for the LB134 Technical data: Scintillator: 1 x 1 NaI crystal γ-response: 250 cps per μsv/h in 137 Cs radiation field 3000 cps per μsv/h in 241 Am radiation field Background: approx. 30 cps at 100 nsv/h γ-ambient level Energy range: 25 kev to 2 MeV (wall material 0.5mm aluminum) Dimensions: Ø 40 mm x 305 mm (rear Ø 50 mm) Temperature range: -10 C to 40 C Protection type: IP 65 (according to DIN IEC 60529) Electronics: PMT, active voltage divider, high voltage supply and charge sensitive preamplifier with discriminator 7.8 Activity Probe for Solid Samples LB 1238 The proportional end window probe LB 1238 is used for activity measurements; it is suitable for alpha-beta measurements. It can be used as portable probe (e.g. in chromatography) or stationary for solid sample measurements, such as planchets or wipe tests. The probe consists of an amplifier/hv generator with alpha-beta pulse height discrimination in a cylindrical case with built-in end window proportional counter tube type Vacutec (window diameter = 29 mm). It has two pulse outputs, one each for the alpha and one for the beta rate. The probe can be inserted in the small lead chamber LB 7411 to measure planchets up to 25 mm diameter. 99

110 7. Probes for the LB 134 Figure 7.15: Lead shielding and activity probe LB 1238 Technical data: Detector: Proportional end window counter tube Entrance window: Mica window, about 2 mg/cm² Energy range: Alpha: from 3 MeV Beta: from 40 kev Responsiveness: Am-241 approx. 18% Sr-90 approx. 46% Protective grid: Covers approx. 30% Background: Alpha channel: typ counts/min Beta channel: typ. 13 counts/min Measuring range: Background up to cps Operating voltage: typ V 100

111 7. Probes for the LB Tritium Surface Contamination Monitor Device Configuration The Tritium Surface Contamination Probe LB 1239 consists of the following parts: Windowless Tritium probe LB 1239 with combined spiral cable/gas tubing for connection to the LB 134 and gas supply (8-pin to 11-pin spiral cable and transparent PVC tubing with 3 mm internal diameter) Figure 7.17: Tritium probe LB 1239 Aperture plate drwg # to be placed on top of the Tritium probe (held in position by magnets). Trolley drawing # with gas shut-off valve and gas flow meter (rotameter) with a measuring range 0 to 3000 cm³/min. The trolley includes a console for LB 134, Tritium probe and beta-gamma probe (option). Caution: The value on the rotameter scale has to be multiplied by liters P10 gas cylinder with double pressure reducer, mounted on trolley. Option for extending the range of applications: Beta-gamma probe LB 1231, also mounted on the trolley and alternatively connected to the LB

112 7. Probes for the LB 134 Figure 7.18: Tritium Surface Contamination Monitor: Trolley with UMO basic unit, Tritium probe, β-γ-probe and P10 gas cylinder, UMO is replaced by LB Application The Tritium probe LB 1239 is a windowless proportional counter tube detecting Tritium on plane surfaces with very high efficiency. This counter tube makes it possible to meet the detection limit stipulated by the German Radiological Protection Act for surface contamination with Tritium on large flat areas. The Tritium probe incorporates a preamplifier and a high voltage generator; for measurement, it simply has to be connected to the basic LB 134 unit via a 8-pin cable and a P10 gas supply tubing. The user-friendly assembly of the instruments on a trolley with P10 gas cylinder as gas supply and a console for the Tritium probe with automatic gas shut-off ensures simple and quick handling in the laboratory. In addition, a β-γ-probe can be mounted on the console (optional) and connected to the LB 134 by changing the connection cable Probe Assembly The Tritium probe LB 1239 is a windowless proportional counter tube incorporating a preamplifier and a high voltage unit. The LB 134 software identifies the probe and controls the high voltage. The windowless counter tube aperture is 150 mm x 15 mm with an effective area of 22 cm². Electrically it is terminated by five thin cathode wires and mechanically it is enclosed by a finemesh nylon grid providing dust protection. The counting chamber is only 5 mm high. This reduces both background and gas 102

113 7. Probes for the LB 134 consumption and ensures a steady gas flow. Three parallel counting wires ensure a constantly high response probability over the entire aperture area. Four spacers keep the detector at a constant distance of 2 mm from the surface being monitored without coming in contact with it. We supply an aperture plate as an accessory which is held in position by magnets. It is used, for example, to measure finger tips. Figure 7.19: The window side of the Tritium probe LB The Tritium probe is connected to the basic unit LB 134 using a spiral cable; the LB 134 automatically identifies the probe after power on, switches to the CPS mode and takes over the HV control. The Tritium probe is a flow-through counter tube using P10 gas as counting gas for operation (approx cm³/min). The counting gas enters the probe via a transparent PVC tubing and exits at the window opening, building up a layer of gas between the contaminated surface and the counting wires which is required for the measurement. The gas flow is cut off as soon as the probe is correctly placed onto the console on the trolley. This turns off the gas flow switch; it is turned on only when taking off the probe again for another measurement Counting Gas Supply The counting gas used is P10 (gas mixture consisting of 90% Argon and 10% Methane). A 3-liter cylinder with double pressure reducer is mounted on a small trolley. The gas flows through a transparent PVC tubing (internal Ø 5mm) to the gas shut-off valve which opens when the probe is lifted off and closes when it is put down again. From there it flows via the gas flow meter (rotameter) to the Tritium probe. 103

114 7. Probes for the LB 134 This ensures that only the required amount of counting gas is consumed and that the cylinder valve need not be opened and closed after each measurement. The rotameter shows a gas flow of cm³/min. For measurement, the gas flow should be set to 2000 cm³/min. Caution! The value on the rotameter scale has to be multiplied by 10. Figure 7.20: Schematic layout of the gas cycle Double pressure reducer -> valve Valve -> rotameter (bottom) Rotameter (top) -> probe Setting the gas flow 1. The tubing is connected correctly. The probe is in the holder on the console, so that the gas valve is closed. The double pressure reducer is closed. 2. Lift the probe from the console to open the gas valve, so the gas can flow through the rotameter. 3. Open the tap of the P10 gas cylinder. 4. Slowly open the double pressure reducer and adjust it such that the rotameter indicates 200. Keep in mind that it takes some time until the gas has reached the rotameter. 104

115 7. Probes for the LB Place the probe back in its compartment. The probe is still ready for operation, but no gas leaks out. If the probe is not used for a longer period of time (e.g. over night) you just have to close the tap of the gas cylinder. If it is opened again, the correct gas flow is set automatically Tritium Probe with Trolley The trolley is specifically designed to accommodate all instruments necessary for the measurement of Tritium (LB 134, Tritium probe, P10 gas cylinder) and the probe LB 1231 to measure beta-gamma radiation (β-γ-probe) and allows simple and quick handling. Assembly The trolley with 2 wheels rests firmly on two fixed feet on the floor. For transportation, simply tilt it back at the handle to raise the feet and you can pull or push the trolley on its wheels. The 3-liter P-10 gas cylinder is strapped to the vertical pipe, starting at the wheel axle and ending in the trolley handle. It also supports the console for the measuring instruments. The console is equipped with holders for the Tritium probe (right) and a β - γ probe (optional). At the rear, the probes are held in place by a black tapered metal bar, at the front by resilient plastic pivots, at the side by metal bars. The compartment for the Tritium probe includes an opening for the spring switch of the gas valve. When the probe is inserted, the gas valve is closed and when the probe is removed, the gas valve opens. In the center of the console there are two retention cradles, into which the LB 134 is placed and secured by knurled screws. The rotameter indicating the actual gas flow is installed to the left of the Tritium probe. Inserting the Tritium Probe The Tritium probe has to be inserted correctly to make sure that the gas flow valve switch is closed. (a) Take the probe by its handle and with the rear side first put it onto the console, directly at the black rail. Then push the front side down along the resilient pivots. 105

116 7. Probes for the LB 134 b) You may also proceed in reverse order: First, put the front side of the probe against the pivots and then push the rear side down against the tapered bar. Figure 7.22: Inserting the Tritium probe Figure 7.22: Closing the gas valve when inserting the probe Commissioning of Tritium Probe Sdfsf 1. Remove the transport packaging and check the equipment parts for completeness and integrity. Installing the P10 gas cylinder and double pressure reducer 2. Place the P10 gas cylinder (closed!) in the holding device on the trolley and secure it with both straps. 3. Screw the closed double pressure reducer onto the gas cylinder by placing the sleeve nut onto the screw 106

117 7. Probes for the LB 134 thread (left-hand thread!) of the gas cylinder and fixing it using a 27 mm wrench. Installing the Tritium probe on the trolley console 4. Take off the protection cap (cardboard) from the counter tube. 5. Place the Tritium probe on the right side of the trolley console into the compartment provided for this purpose, thus closing the valve switch for the gas flow. 6. Hold the probe at the handle and with the rear end first, set it onto the console, directly against the black bar. Then push the front side down along the resilient pivots. You may also proceed in reverse order: First, put the front side of the probe against the pivots and then push the rear panel down against the tapered bar. Connecting cables and tubing 7. Place the transparent PVC-tubing which is already fixed to the valve inlet onto the double pressure reducer. The connection valve -> rotameter (bottom nozzle) is already installed in the factory. 8. Now take the spiral cable containing a gas tubing. Cable and tubing run nearly parallel, ensuring simple handling. 9. Using the spiral cable, connect the LB 134 and the Tritium probe. The 11-pin socket of LB 134 is located on the right side of the instrument, that of the probe on the front side facing the user. 10. Plug one end of the gas tubing connected to the spiral cable onto the rotameter outlet (at the top of the rotameter) and the other onto the probe inlet. Setting the gas pressure 107

118 7. Probes for the LB Take the Tritium probe out of the holding device to open the gas valve and place it on a flat table surface. 12. With the double pressure reducer closed, open the P10 gas cylinder. 13. Slowly open the double pressure reducer until the rotameter indicates a level of 200. Keep in mind that it takes a certain time until the gas has reached the rotameter. When using the aperture plate, less gas is needed, so that the double pressure reducer may be set to about 100cm³/min. 14. Re-place the probe again in the holding device. Measurement 15. Turn the LB 134 on. The instrument identifies the connected Tritium probe and sets the measurement mode accordingly. 16. The instrument is ready for measuring surfaces contaminated with Tritium: take the probe out of the holding device and place it onto the surface being measured. The measured Tritium activity is indicated on the LB 134 display. If necessary, run a test measurement using the appropriate test source. 17. For the measurement of finger tips, place the aperture plate over the probe. The plate is held by magnets. When using the aperture plate, the gas flow has to be reduced and adjusted accordingly. End of measurement 18. Once the measurement is over, re-place the Tritium probe correctly in its position (see steps 5. and 6.) to close the gas valve. 19. Close the P10 gas cylinder if you do not use the probe for a longer period of time. Using the β-γ-probe On the left side of the trolley console there is space for the β-γ probe LB 1231; its connecting cable to the LB 134 is placed in a holder. 1. Turn off the LB Pull out the spiral cable connecting the Tritium probe to the LB Insert the spiral cable of the β-γ-probe into the LB 134 socket. 108

119 7. Probes for the LB Turn the LB 134 on. The software identifies the connected β-γ-probe and sets the measurement mode accordingly. 5. If necessary, run a test measurement using a suitable test source Practical Hints for Operation and Measurement Operation with LB 134 The measurement of Tritium with the LB 134 and the connected Tritium probe is carried out in the same manner as the contamination measurement described above. Probe and calibration factors are set such that only Tritium activities are determined and displayed. Measuring flat, horizontal areas The counter tube LB 1239 with the entire open window length, i.e. without the aperture plate, is used for measuring flat areas. In this case the window opening must always face down and be completely covered by the surface being measured to rule out any unrestrained leaking out of the counting gases from parts of the window opening. Please move the counter tube slowly when scanning the surface. Measuring irregular areas, clothing, finger tips, wipe tests For these measurements the aperture plate is placed onto the probe. This reduces the effective area but allows monitoring of critical areas for Tritium contamination. The aperture plate should be used when interference is caused by possible electromagnetic charges on surfaces when the window area is fully opened (too high or irregular count rates). After use, the probe must be re-placed immediately into the holder on the trolley console to shut off the gas flow. If you don't use the instrument for a longer period of time, close the valve of the P10 gas cylinder! Performance Check The regular performance check that is required by the German Radiological Protection Act can be carried out using any betaemitting radionuclide, for example, a Sr-90 source. Simply place the Tritium probe on the respective source. Due to the window- 109

120 7. Probes for the LB 134 less measurement, the count rates measured by the Tritium probe are typically about 20% higher than indicated on the control substance (contrary to the Xenon probe LB 1231 which is sealed by a 5 mg Titan window foil). Test measurements with 3 H substances, however, may also cause problems, because even minor distance changes, contamination of the source or decay of Tritium in the course of time will result in changes in the count rate which are not due to the instrument itself. The Tritium half-life of years must also be taken into account (see the table below). Upon request, the 3 H calibration source TRR (~ 10 kbq) can be supplied as control substance. The number of Beta particles emitted into the half-space as well as the reference data is marked on the plate. In the case of 3 H, one will measure about 85% of the emitted particles Efficiency and Detection Limits Detecting 3 H Contamination There is no completely satisfactory method for detecting 3 H contamination. The following options are available: Direct measurement using the Monitor LB 134/LB

121 7. Probes for the LB 134 Wipe test (using glycerin or toluene-saturated filter papers, then measurement with the probe LB 1239 or in a liquid scintillation counter) Washing down or rinsing clothing, followed by measuring liquid samples in the liquid scintillation counter. The direct measurement is the first choice for flat, smooth surfaces which do not allow 3 H contamination to penetrate. Such surfaces are specified for the working surfaces in the radionuclide laboratory. This probe is ideally suited for this because of its large window opening. Rough surfaces such as absorbent paper or wood make the measurement increasingly inaccurate since self-absorption in the contaminated medium can be considerable due to the low energy of the Beta particles. In this case, other methods of detection may have to be used (wipe test, washing down or rinsing followed by measurement in the liquid scintillation counter). To ensure an accurate measurement, the large window opening of the counter tube LB 1239 requires that the surface to be monitored should totally cover the opening. For this reason, the counter tube needs to be placed onto the surface, for example, the table top, from above. At the same time, this ensures that the minimum distance is kept. When surfaces to be monitored are not horizontal or flat, or if they do not fully cover the window opening, then the aperture plate supplied has to be used. In conjunction with the aperture plate the Tritium probe can also be used for detecting contamination on finger tips and, to a limited extent, also on specific areas on clothing, for instance after it has been splashed. However, in this case it is only possible to give a qualitative indication since the extent of the selfabsorption remains unknown. Let us use an example to illustrate this: The maximum range of a 3 H Beta particle of maximum energy (18.6 kev) emitted at right angles to the surface is only 8 µm in material having a density of 1; the average range of medium-energy particles, on the other hand, is 0.2 μm. When taking a direct measurement one can therefore at best detect the activity in a layer of approximately 0.5 µm corresponding to a surface density of 0.05 mg per cm². The methods used in the wipe test or when washing items are more suitable from this point of view for detecting Tritium activity on rough surfaces or fabrics. However, their efficiency is completely indeterminate. What fraction of the activity is wiped off or removed by washing depends very much on individual conditions. 111

122 7. Probes for the LB 134 For further details see the DIN standard T2 "Decontamination of Radioactively Contaminated Surfaces; Determination of Surface Contamination". Calibration Factor and Detection Limits of the Tritium Probe LB 1239 When the probe LB 1239 is correctly positioned over a flat surface, about 85% of the Beta particles emitted from the surface below the window opening will be detected and counted, because the electrons created outside the actual counting room are "pulled" into the detector. For a 3 H-source that is free of self-absorption we will therefore get the following calibration factors: Point source Area source 2.2 Bq (6 x 10E-5 μci) per cps 0.1 Bq/cm² (2.7 x 10E-6 μci/cm²) per cps (with window completely open) 1 Bq/cm² (2.7 x 10E-5 μci/cm²) per cps with aperture plate exceeding the size of the window opening With a background of approx. 1 s -1 this results in the following detection limits for 3 H substances at a statistical safety of 3σ: Ratemeter time constant *) τ = 200s point source activity approx Bq (free of self-absorption) approx nci area-specific activity approx Bq/cm² approx E-5μCi/cm² *) With the LB 134 the time constant in the normal measurement mode is 120 s. The Counter/Timer mode can be used for more accurate measurements. The limit threshold for 5 Bq/cm 2 (according to the German Radiological Protection Act, Appendix IX) is 55 cps -1 with fully open window or 5 cps with aperture plate Working with the β-γ-probe On the left side of the trolley console there is the compartment for the β-γ-probe LB Its connection cable to the LB 134 can be hooked into the circular holding device. Proceed as follows if you want to use this probe instead of the Tritium probe: 112

123 7. Probes for the LB Turn off the LB Pull out the spiral cable connecting the Tritium probe to the LB Insert the spiral cable of the β-γ-probe into the LB 134 socket. 4. Turn the LB 134 on. The software identifies the connected β- γ-probe and sets the measurement mode accordingly. 5. Perform a control measurement. 113

124 8. Maintenance 8. Maintenance 8.1 Battery Replacement The device requires four AA dry batteries, Mignon with 1.5 volts or 4 Mignon rechargeable batteries with 1.2 volts. The operating time with a new set of batteries is longer than 15 hours of continuous use for the basic device with internal probe (without backlight and without USB communication) and 10 hours for fully charged rechargeable batteries. A set of rechargeable batteries is included with the device. The battery compartment, located on the back of the monitor, is closed by a cover plate. Pull the cover downward to take it off. Replace the batteries as shown in Figure 8.1. Then secure the batteries with the cover plate. Figure 8.1: Batteries in the battery compartment If you continue to operate the device with dead batteries, the device turns off automatically as soon as the battery voltage is no longer sufficient for proper operation. In this case, you have to replace the batteries to be able to restart the device. Remove the batteries if the device is not used for rather long period of time, e.g. several months. 114

125 8. Maintenance 8.2 Charging Rechargeable Batteries Only Ni-MH rechargeable batteries may be used in the LB 134 (eneloop Pro AA 2450 mah). Select the battery type "Accu" on the menu Parameters/Power Supply. Connect the LB 134 to the power supply to charge the batteries (the device is switched on automatically) and the charge process starts if the parameters in the menu Parameters/Power Supply/Charge Mode have been set accordingly. In the meantime, measurements can be performed because the device operates with mains voltage in this operation mode. The charging function is active only when the device is turned on! The charging process is completed as soon as the time period specified in Charge Time is over. Warning: If there are batteries in the battery compartment instead of rechargeable batteries and you select "Accu" and start the charging process, this can lead to overheating of the batteries and damage the device. 115

126 9. Basis of Calculation 9. Basis of Calculation 9.1 Calculating the Count Rate The LB 134 updates the calculation of the raw data in CPS (counts per second) every second, i.e. the further calculation is based on 1 second intervals. General Formulas and Terms t T Measuring time: c Time constant of the ratemeter [s] Relative statistical error in % T I Length of an interval (always 1s) Counting pulses of the current interval n i n T i R Count rate (raw data) in actual second Rb Rb-1 R R T n 0 0 I Gross count rate (mean raw data) Gross count rate of the preceding interval Net count rate Background count rate Background measuring time The gross count rate in the ratemeter mode is calculated using an exponential weighting according to the formula: R b W * R (1 W)* Rb 1 The weighing factor W is determined as follows: W = t 1 After the start of measurement, t starts at 1 and is incremented by 1 every second, until the value of the time constant T c has been reached and then remains at that level. In the Counter/Timer measurement (see below), the time constant corresponds to measuring time after which the measurement is terminated. The number of seconds used for averaging is determined depending on the measurement mode and can thus determine whether a high degree of accuracy with slower response time to activity changes, or a quick adaptation to changes associated with a lower accuracy is obtained. 116

127 9. Basis of Calculation 9.2 Ratemeter Function The weighting factor W described in chapter 9.1 can be determined either as a function of the time constant or the accuracy: a) Preset time constant: The number of seconds entered indicates the maximum time constant that is used for averaging, which means that at a set time constant of 100 s, the weighting factor is calculated with W=1/100 after 100 s. In this case, the accuracy that can be reached is dependent on the count rate and the time constant. b) Preset accuracy: When a relative accuracy R R b b *100 in percent is to be reached, t in the above formula must be replaced by T c 1 1 * * Rb Preset accuracy is recommended for higher count rates (100 cps and higher). If the count rate changes statistically significant within a short period, then t is reset to 1 again and thus the new measured values are again given more weight. The reject criterion can be adjusted individually. For this purpose, the standard deviation R T b I, with TI = 1 s is used as a measure of the statistical accuracy. If the difference between the current measured value and the current average is greater than an adjustable number of standard deviations, then the averaging starts again from the beginning and t is reset to 1. For the ratemeter, the preset reject criterion is

128 9. Basis of Calculation Definition of statistical errors: Formula abs. error rel. error Gross count rate R b W * R (1 W)* Rb 1 R R b b R b 2T 1 Net count rate Rn ( Rb R0 ) n c Rb R R or R Basis of Calculation Ratemeter: n R T 0 0 Rb 2T 1 c R b R R n n Parameters Designation Variable Unit Default Averaging Time (preset: time, accuracy) Time constant (preset time) T c [s] 120 Accuracy (preset accuracy) P [%] 3.0 Sigma factor S 4.0 Nuclide (with calibration factor K) K Net Preset time constant: W 1 for t W 1 for T c t T c t T c Preset accuracy: W 1 R t for b P / R 100 b W 1 R b for P / 100 T c Rb Reset and recalculate of W, t and R R S * b R b Rb if 9.3 Search Mode In the Search mode, the same computational algorithms are used as in the Ratemeter mode to calculate the mean values. The preset reject criterion is 5. The time constant for the averaging is 20 s. As a result, the display reacts much faster to changes in the count rate than in the ratemeter mode. 118

129 9. Basis of Calculation Basis of calculation: Parameters Designation Variable Unit Default Time constant (preset time) T [s] 10 c Sigma factor S 5 Nuclide (with calibration factor K) K Net Preset time constant: W 1 for t W 1 for T c t T c t T c Reset and recalculate of W, t and Rb if R Rb S * Rb 9.4 Counter/Timer Function In the Counter/Timer mode, all measured values in a given time interval are combined to form an arithmetic average. There are three stop criteria for the time interval: a) Time: Here the measurement runs until the set time in seconds is over. b) Accuracy: Here the criterion for the end of the measurement is given by the achieved relative accuracy in %: ( = 100 / n ), n = number of counts The preset values (time: 120 s, counts: 1000 s, accuracy: 3.0%) have to be adapted accordingly to the requirements of the measurement. Absolute statistical error: R n R t b R T 0 0 t elapsed measuring time 119

130 9. Basis of Calculation 9.5 Determination of Calibration Factors in the Event of Contamination The explanation of the basic principles of the Becquerel calculation is not only of a documentary nature; rather, it is meant to enable you to determine calibration factors for other nuclides for contamination measurements, which are not included in the nuclide library of the LB 134. New nuclides can be added to the nuclide list. To convert counts per second into decays per second per cm 2, the calibration factor K must be determined for each nuclide and each detector type according to the formula Contamination = C x cps [Bq/cm 2 ] Contamination = area activity in Bq/cm² C = calibration factor in Bq/cm 2 /cps cps = measured net counts per second For the determination of C according to the DIN standard, a calibration source with known activity per cm 2 is used (standardized to 100 cm 2 ) and measured with the LB 134. The result of the measurement is converted using the formula C = A/cps into Bq/cm 2 /cps. A = calibration source activity in Bq/cm 2 Requirements for the calibration source Sources meeting the requirements of the international standard ISO Nr "Reference Sources for Calibration of Surface Contamination Monitors" should be used to comply with the ISO-7503 standard for the calibration for beta measurements. This standard requires that the measured values must relate to the surface emission rate, i.e. beta particles per second and cm 2 being emitted from the test source surface. Berthold Technologies offers two different selectable types of calibration (on the Nuclides menu) with the designations "A100" and "ISO 7503". The A-100 calibration of Berthold Technologies contamination monitors is done using the following equations relative to the activity of the reference source and the reference surface W of 100cm² (A is the activity of the calibration source in Bq): 120

131 9. Basis of Calculation RSource RBgrd Detection (1) (A in Bq) A N A A CAL Surface Surface 1 W Detection CAL Sample Bgrd (2) N R R (3) RSample RBgrd (4) W Detection The ISO calibration is performed according to the International Standard ISO [1] relative to the surface emission rate q2 of the reference source and the sensitive detector surface W, as a reference surface. In accordance with ISO , the equations 5-8 also take into account the emission efficiency Source. N A A Detection CAL Surface R Source q 2 R Bgrd (5) 1 W Detection CAL Sample source Bgrd (6) N R R (7) R R Sample Bgrd Surface (8) (Bq/cm²) Detection W source In this formula the area W is explicitly included, therefore use for the emission rate q2π the total number of betas per second. If the surface emission rate is not available, as in this case, we use q 2 A 2 The emitter efficiency source of alpha emitters must be assumed to be 0.25, that of beta emitters 0.50 [1]. For some beta emitters with low beta energies we also have to use If the sensitive detector area is larger than 300 cm 2, 300 cm 2 is used for W. [1] DIN ISO : : Evaluation of surface contamination; beta-emitters (maximum beta energy greater than 0,15 MeV) and alpha-emitters; identical with ISO :

132 9. Basis of Calculation Proceed as follows 1. Select the CPS measurement mode. 2. Place the probe on the calibration source as centered as possible, so that as little as possible activity is lost. 3. Measure the calibration source with a measurement time of 60 seconds. 4. Calculate the constant C using the formula given above. 5. Enter the calibration factor determined in the parameter list of the newly defined nuclide. The supplied test sources are no calibration sources. They are point sources and therefore cannot be used for the calculation of area activities. 122

133 10. Decision Thresholds and Detection Limits 10. Decision Thresholds and Detection Limits This chapter shows the statistical error, the decision threshold and the detection limit in accordance with ISO for measurements with the LB 134. The uncertainty in the calibration factor is taken into account in this formula but not in the firmware of the LB 134. In the Counter/Timer mode, the calculation formula for activities, contamination and dose rate in the LB 134 is as follows (the units in all formulas are the same and depend on the measurement method, e.g. Bq/cm² or µsv/h, etc.): Basic formula for activity: A = K (Rg Ro) Statistical total error including uncertainty in the calibration factor: u(a) = K 2 ( Rg tg + Ro to ) + A2 u2 (k) k 2 Decision threshold: EG = K 1,65 Ro ( 1 tg + 1 to ) Detection limit: NG = K (3,3 Ro ( ) + 2,7225 ) / (1 2,7225 u2 (K) ) tg to tg K² Where K calibration factor Rg gross rate Ro background rate tg measuring time in s to background measuring time in s A activity k1- = k1-β 1.65 (quantile) u(k) / k relative error of calibration factor (= percentage value divided by 100); if the error in the calibration factor should not be taken into account, u(k) will be set to zero in the formulae. All variables have the same unit. The unit depends on the calibration. In the Ratemeter mode, the measuring time tg must be replaced by 2 * τ and τ is the entered time constant in s. 123

134 11. Appendix 11. Appendix 11.1 Calibration Factors for LB 1342 Scint-Contamination Probe (170 cm²) List of radionuclides with calibration factors that are hard-coded in the LB 134 (for the scint detector) for the conversion of cps to Bq/cm 2. Test sources with a standardized area of 10 cm x 10 cm were used (A-100). The factors according to ISO have been determined in compliance with the requirements of the standard. LB1342 6) Limit values 1) Nuclide CH eff src in Bq/cm² Efficiency in % Efficiencies, response, calibration factors and decision thresholds and detection limits ISO ) Response in s -1 Bq -1 cm 2 Calibration factor in s Bq cm -2 Decision thr. in Bq/cm² 5) Detection limit in Bq/cm² 4)5) Beta b-g C-11 b-g N-13 b-g C-14 b-g O-15 b-g F-18 b-g Na-22 b-g P-32 b-g P-33 b-g S-35 b-g Cl-36 b-g K-40 b-g K-42 b-g Ca-45 b-g Sc-46 b-g Ca-47+ b-g Cr-51 b-g Mn-54 b-g Fe-55 b-g Co-57 b-g Co-58 b-g Fe-59 b-g Co-60 b-g Ni-63 b-g Ga-67 b-g Se-75 b-g Sr-85 b-g Rb-86 b-g Sr-89 b-g Sr-90+ b-g Y-90 b-g Tc-99m b-g Tc-99 b-g Ru-106+ b-g In-111 b-g Sn-113+ b-g I-123 b-g I-125 b-g

135 11. Appendix LB ) Limit values 1) Nuclide CH eff src in Bq/cm² Efficiency in % Efficiencies, response, calibration factors and decision thresholds and detection limits ISO ) Response in s -1 Bq -1 cm 2 Calibration factor in s Bq cm -2 Decision thr. in Bq/cm² 5) Detection limit in Bq/cm² 4)5) I-131 b-g Cs-137+ b-g Pm-147 b-g Sm-153 b-g Er-169 b-g Re-186 b-g Re-188 b-g Au-198 b-g Tl-201 b-g Tl-204 b-g U-238sec b-g Pu-238 b-g Am-241 b-g Po-210 a U-238sec a Pu-238 a Pu-239 a Am-241 a Alpha a ) Limit values taken from the German Radiation Protection Ordinance 2001, Annex III, Table 1, column 4 3) Values relative to the surface emission rate and 170 cm² sensitive detector area according to DIN ISO ) Decision threshold and minimum detectable activity (MDA) are in accordance with ISO calculated with a measuring time of 200 s for the background and 30 s for the sample measurement 5) Background count rate used from 0.1 cps for alpha and to 10 cps for beta-gamma measurements 6) Valid from LB 134 software version

136 11. Appendix LB ) Nuclide CH eff src Limit values 1) in Bq/cm² Efficiency in % Efficiencies, response, calibration factors and decision thresholds and detection limits A-100 2) Response in s -1 Bq -1 cm 2 Calibration factor in s Bq cm -2 Decision threshold in Bq/cm² 5) Detection limit in Bq/cm² 4)5) Beta b-g C-11 b-g N-13 b-g C-14 b-g O-15 b-g F-18 b-g Na-22 b-g P-32 b-g P-33 b-g S-35 b-g Cl-36 b-g K-40 b-g K-42 b-g Ca-45 b-g Sc-46 b-g Ca-47+ b-g Cr-51 b-g Mn-54 b-g Fe-55 b-g Co-57 b-g Co-58 b-g Fe-59 b-g Co-60 b-g Ni-63 b-g Ga-67 b-g Se-75 b-g Sr-85 b-g Rb-86 b-g Sr-89 b-g Sr-90+ b-g Y-90 b-g Tc-99m b-g Tc-99 b-g Ru-106+ b-g In-111 b-g Sn-113+ b-g I-123 b-g I-125 b-g I-131 b-g Cs-137+ b-g Pm-147 b-g Sm-153 b-g Er-169 b-g Re-186 b-g

137 11. Appendix LB ) Nuclide CH eff src Limit values 1) in Bq/cm² Efficiency in % Efficiencies, response, calibration factors and decision thresholds and detection limits A-100 2) Response in s -1 Bq -1 cm 2 Calibration factor in s Bq cm -2 Decision threshold in Bq/cm² 5) Detection limit in Bq/cm² 4)5) Re-188 b-g Au-198 b-g Tl-201 b-g Tl-204 b-g U-238sec b-g Pu-238 b-g Am-241 b-g Po-210 a U-238sec a Pu-238 a Pu-239 a Am-241 a Alpha a ) Limit values taken from the German Radiation Protection Ordinance 2001, Annex III, Table 1, column 4 2) Values relative to the activity and 100 cm² source area (DIN 44801) 4) Decision threshold and minimum detectable activity (MDA) are in accordance with ISO calculated with a measuring time of 200 s for the background and 30 s for the sample measurement 5) Background count rate used from 0.1 cps for alpha and to 10 cps for beta-gamma measurements 6) Valid from LB 134 software version

138 11. Appendix 11.2 Calibration Factors for LB 1231 and LB 1233 Nuclide LB 1231 (Xenon) Channel A-100 calibration factor in Bq/cm²/cps LB 1233 (P-10 Gas) Channel A-100 calibration factor in Bq/cm²/cps α-tot Beta - Gamma --- Alpha βγ-tot Beta - Gamma 0.05 Beta - Gamma C-14 Beta - Gamma Beta - Gamma F-18 Beta - Gamma Beta - Gamma P-32 Beta - Gamma 0.04 Beta - Gamma P-33 Beta - Gamma Beta - Gamma S-35 Beta - Gamma Beta - Gamma Cl-36 Beta - Gamma 0.05 Beta - Gamma Cr-51 Beta - Gamma Beta - Gamma 0.30 Mn-54 Beta - Gamma 1.16 Beta - Gamma Co-57 Beta - Gamma Beta - Gamma Co-58 Beta - Gamma Beta - Gamma Fe-59 Beta - Gamma Beta - Gamma Co-60 Beta - Gamma Beta - Gamma Ga-67 Beta - Gamma Beta - Gamma Se-75 Beta - Gamma Beta - Gamma Sr-89 Beta - Gamma Beta - Gamma Sr-90+ Beta - Gamma Beta - Gamma Tc-99m Beta - Gamma Beta - Gamma In-111 Beta - Gamma Beta - Gamma Sn-113+ Beta - Gamma Beta - Gamma I-123 Beta - Gamma Beta - Gamma I-125 Beta - Gamma Beta - Gamma I-131 Beta - Gamma Beta - Gamma Cs-137+ Beta - Gamma 0.06 Beta - Gamma Pm-147 Beta - Gamma Beta - Gamma Tl-201 Beta - Gamma Beta - Gamma Tl-204 Beta - Gamma Beta - Gamma Pb-210 Beta - Gamma Beta - Gamma Po-210 Beta - Gamma --- Alpha U-238se Beta - Gamma Alpha Pu-238 Beta - Gamma Alpha Pu-239 Beta - Gamma Alpha Am-241 Beta - Gamma Alpha

139 11. Appendix 11.3 Calibration Factors for LB 1341 (Xenon detector) Nuclide Channel A-100 calibration factor in Bq/cm²/cps ISO Calibration factor in Bq/cm²/cps Beta-tot Beta - Gamma C-11 Beta - Gamma N-13 Beta - Gamma C-14 Beta - Gamma O-15 Beta - Gamma F-18 Beta - Gamma Na-22 Beta - Gamma P-32 Beta - Gamma P-33 Beta - Gamma S-35 Beta - Gamma Cl-36 Beta - Gamma K-40 Beta - Gamma K-42 Beta - Gamma Ca-45 Beta - Gamma Sc-46 Beta - Gamma Ca-47 Beta - Gamma Cr-51 Beta - Gamma Mn-54 Beta - Gamma Fe-55 Beta - Gamma Co-57 Beta - Gamma Co-58 Beta - Gamma Fe-59 Beta - Gamma C0-60 Beta - Gamma Ga-67 Beta - Gamma Se-75 Beta - Gamma Sr-85 Beta - Gamma Rb-86 Beta - Gamma Sr-89 Beta - Gamma SrY-90 Beta - Gamma Y-90 Beta - Gamma Tc-99 Beta - Gamma Tc-99m Beta - Gamma Ru-106 Beta - Gamma In-111 Beta - Gamma Sn-113 Beta - Gamma In114m Beta - Gamma I-123 Beta - Gamma I-125 Beta - Gamma I-129 Beta - Gamma I-131 Beta - Gamma Cs-137 Beta - Gamma Pm-147 Beta - Gamma Sm-153 Beta - Gamma Er-169 Beta - Gamma Re-186 Beta - Gamma Au-198 Beta - Gamma Tl-201 Beta - Gamma Tl-204 Beta - Gamma Pb-210 Beta - Gamma Ra-224 Beta - Gamma Ra-226 Beta - Gamma

140 11. Appendix U-238 Beta - Gamma Pu-238 Beta - Gamma Pu-239 Beta - Gamma Am-241 Beta - Gamma

141 11. Appendix 11.4 Calibration Factors for LB 1343, Scintillation Detector (345 cm²) Nuclide Channel A-100 calibration factor in Bq/cm²/cps ISO Calibration factor in Bq/cm²/cps Beta - total Beta - Gamma C-11 Beta - Gamma N-13 Beta - Gamma C-14 Beta - Gamma O-15 Beta - Gamma F-18 Beta - Gamma Na-22 Beta - Gamma P-32 Beta - Gamma P-33 Beta - Gamma S-35 Beta - Gamma Cl-36 Beta - Gamma K-40 Beta - Gamma K-42 Beta - Gamma Ca-45 Beta - Gamma Sc-46 Beta - Gamma Ca-47+ Beta - Gamma Cr-51 Beta - Gamma Mn-54 Beta - Gamma Fe-55 Beta - Gamma Co-57 Beta - Gamma Co-58 Beta - Gamma Fe-59 Beta - Gamma Co-60 Beta - Gamma Ni-63 Beta - Gamma Ga-67 Beta - Gamma Se-75 Beta - Gamma Sr-85 Beta - Gamma Rb-86 Beta - Gamma Sr-89 Beta - Gamma Sr-90+ Beta - Gamma Y-90 Beta - Gamma Tc-99m Beta - Gamma Tc-99 Beta - Gamma Ru-106+ Beta - Gamma In-111 Beta - Gamma Sn-113+ Beta - Gamma I-123 Beta - Gamma I-125 Beta - Gamma I-131 Beta - Gamma Cs-137+ Beta - Gamma Pm-147 Beta - Gamma Sm-153 Beta - Gamma Er-169 Beta - Gamma Re-186 Beta - Gamma Re-188 Beta - Gamma Au-198 Beta - Gamma Tl-201 Beta - Gamma Tl-204 Beta - Gamma U-238sec Beta - Gamma Am-241 Beta - Gamma Pu-238 Alpha

142 11. Appendix Am-241 Alpha Po-210 Alpha U-238sec Alpha Pu-238 Alpha Pu-239 Alpha Am-241 Alpha Alpha - total Alpha

143 11. Appendix 11.5 F²C Communication Protocol and Commands The LB 134 has several communication options with the PC, via the USB port and via the RS485 interface. The baud rate for the USB interface is always 38400, for RS485 it can be set under Parameters/Hardware. The other parameters are fixed: (data bits: 8; parity: none; start bit: 1, stop bit 1, no handshake). Many functions of the device can be remote controlled by an external PC or stored data can be transferred to this PC. Also, both the parameters and the FIFO data can be transferred to a USB stick. The parameters can also be restored from the stick to the device. At the end of each cycle, the following data is written to a memory (FIFO): Date/Time: (Memory number: is sent with F2C) Cycle number: (ushort) Status: 12 character, ASCII Hex Sample measurement time [sec]: (ushort) Nuclide name / Measurement type name 1: Text[7] Measured value 1: float Unit 1: Text[6] Integral value 1: float Integral unit 1: Text[6] Nuclide name 2: Text[7] Measured value 2: float Unit 2: Text[6] Integral value 2: float Integral unit 2: Text[6] Integral time since last reset [h]: float The depth of the FIFO is 2400 measured data. With Read FIFO, the above data are transmitted in this order after the frame, see examples at the end Status Definition in LB 134 The current status of the measuring device is determined every second. This includes the states of all errors and alarms. This information is summarized in 12 Ascii hex characters, with each bit corresponding to a particular state. These 5 characters are transmitted with the Get status command and with Autosave they are stored to the memory after each current measuring time. 133

144 11. Appendix The individual characters are explained in the following table. Character no. Decimal Status Meaning value 8 0 / 1 Alarm Integral 2 on/off / 1 Alarm Integral 1 on/off 2 0 / 1 Alarm measured value 2 b on / off 1 0 / 1 Alarm measured value 1 (a) on / off 8 0 / 1 FIFO overwritten 4 0 / 1 Probe failure off / on / 1 FIFO 75% full 1 0 / 1 Memory full 8 0 / 1 System test in progress 4 0 / 1 Clearance in progress / 1 Measurement in progress 1 0 / 1 Background in progress 8 0 / / / 1 1 when data above measuring range / 1 1 when data above measuring range / 1 Mean value bit 4 0 / 1 Search measuring mode / 1 Ratem measurement mode 1 0 / 1 C/T measurement mode 8 0 / 1 Beta channel invalid 4 0 / 1 Detector mode only b / 1 Detector mode only a 1 0 / 1 Detector mode a/b Detector number / / / 1 Clearance: contaminated, no / yes 1 0 / 1 System test OK, no /yes Byte free The order in the telegram is from left to right 1, 2, 3, 4;

145 11. Appendix Transmission Protocol Basic condition The LB 134 can send and receive. The response time of the LB 134 is at most 2 seconds. The transmission pattern is as follows: * TDV FDV PRC MBR TYP ITM (MSK Data)*CSM*CR < Frame header > < Frame > where (..) optional TDV to device FDV from device PRC Process MBR Member TYP Type ITM Item MSK Mask on data FFFFFF (not used) Data data variable length CSM checksum empty if no checksum 00 - FF 8 Bit checksum CR carriage return (Minimum length = 20, maximum 255) The stars "*" must always be included, even if CSM is empty. The LB 134 answers, with TDV and FDV being exchanged in the frame. The LB 134 does not respond to request, if 1. TDV does not match address 2. FDV is not between 9001 and The transmission pattern is incorrect 4. The checksum is not correct Explanation of the transmission frame 1. TDV = logical address of LB 134 set by user program 2. FDV = logical address of host computer, set in the user program. Always PRC = process 00 = system level 01 = read radiological data 03 = digital outputs on/off, reset 135

146 11. Appendix 4. MBR = channel of a processor 1,2,3 = digital inputs 1,2,3,4,5 = fault outputs 1.2 = analog outputs 5. TYPE = type of request 00 = not connected 01 = measured results 02 = measuring parameters 03 = execute action 6. ITM = element of a request, command 7. CSM = checksum If empty, no check 8. MSK = data mask for selection of very specific individual data, e.g. from the FIFO; not in operation Command Overview The following commands can be sent from a host computer. The structure is as described above. Only the content is displayed: Comment: If commands are sent with no parameters, the device answers with the parameters currently set. If any command is sent with the TDV 0000, the device answers with its device identification. However, this should only be done if only one device is connected to the bus, as all devices respond to this command. 136

147 11. Appendix PRC MBR TYP ITM MSK Data Comment and TDV=0000, DevID will be send NN Current detector index (1..N) NN Brightness of display (1,2,3) Read Date Time dd/mm/yy hh.mm.ss Set Date Time NN Set language (1 = deu, 2 = engl) NN Set autosave (0, 1) NN Set autosend data (0, 1) NN Set memory as FIFO/fixed (0, 1) NNNN Set Device Address NN Set opti alarm (0, 1) NN Set acousti alarm (0, 1) NN Set vibration alarm (0, 1), not implemented NNNN Set timeout device (min) NN Set battery type (0=batt, 1=accu) NN Set charge mode (0, 1) NNNN Set charge time (min) NNNNNN Set serial number device as ULONG NN Set baud rate (1,2,3,4,5) NN Number of implemented detectors (read only) FIFO operations Read current measured data from FIFO (WR) Read oldest measured data from FIFO (RD) Increment read pointer and read oldest FIFO status Reset Fifo (Reset RD/WR Pointer) Read status Store current value Read number of measured data in FIFO Set read marker back by 1 for Read all FIFO data Reset read pointer (RD) Background Start background measurement Stop background measurement Send backgrounds (2 values) Sample measurement Start sample measurement Stop sample measurement Read current measured data (Measurement) Integration Start integral calculation Stop integral calculation Reset integral value and I-time 137

148 11. Appendix Parameters PRC MBR TYP ITM MSK Data Comment In the following, nn will be used as detector type: nn = nn NNNN Set sample measurement time in sec nn NNNN Set background measurement time in sec nn NN Set measurement mode (1=RM, 2=ZT, 3=S) nn NN Set averaging type (1=time constant, 2=accuracy) nn float Set time constant in sec nn float Set accuracy in % nn float Set Sigma factor nn float Set preset error alpha % nn float Set preset error (beta) % nn NNNN Set number of cycles nn float Set measuring range low alpha nn float Set measuring range low (beta) nn float Set measuring range high alpha nn float Set measuring range high (beta) nn float Set control voltage HVcntrl nn NNNN Set fail time in s nn float Set fail threshold cps nn float Set background alpha in cps nn float Set background (beta) in cps nn float Set background measurement time (measured) PRC MBR TYP ITM MSK Data Comment nn NN Select Nuclide/Meas. type sample measurement a nn NN Select Nuclide/Meas. type sample meas. (b) nn float Set grid transmission factor a nn float Set grid transmission factor (b) nn float Set dead time (alpha) µs nn float Set dead time beta µs nn NNNNNN Set detector name (Text) nn NN Set display mode (1=ab big, 2=a big, b small, 3=a small, b big) nn NN Set detector mode (1=ab, 2=only a, 3=only b) 138

149 11. Appendix nn NNNNNN Set Serial number detectors nn NN Set Ticks (a) on/off (1/0) nn NN Set Ticks b on/off (1/0) Nuclide parameters Detector type: nn = 1..20, Nuclide index: jj = for nuclides, for measurement modes nn jj --- NNNNNN Nuclide/Measurement type Name NN Nuclide/Measurement type activate (0/1) NN Nu/Ma Radiation type (0=a, 1=b, 2=g, 3=n) NNNNNN Nuclide/Measurement type Unit (Text) float Nuclide/Measurement type threshold float Nuclide/Measurement type integral threshold NNNNNN Nuclide/Measurement type integral unit (Text) NN Nuclide/Measurement type Time base (0=s, 1=min, 2=h) float Nuclide/Measurement type k-factor (din) float Nuclide/Measurement type k-factor iso nn NN Number of nuclides of detector (read only) nn NN Number of fixed nuclides of detector (read only) nn NN Number of nuclides of detector (read only) Remarks: For data format number, any entry is permitted (e.g.: 123, 3.45). For integer, only integers without commas may be entered. Numerical input in exponential presentation possible, for example, 1.3E06. Error messages: Instead of the data, error messages from the LB 134 may be displayed (message instead of data): a) - 1 Data have no meaning, for example: b values in only a channel for a/b detector. b) Status: Character no. 2 Bit 4 set. Data memory has been overwritten via the read mark If over a longer time the FIFO is not read, but the storage continues cyclically, the read mark of the last element read is eventually passt by the write pointer, so that data that are still unread will be overwritten from here on. If thereafter the oldest FIFO element is read, in the status character no. 2 bit 4 is set and the reading mark is placed directly in front of the write pointer. c) --FIFO BOTTOM-- Data memory read mark reset to the beginning 139

150 11. Appendix d) --FIFO EMPTY-- Data memory empty or write pointer on 1 st position e) --FIFO TOP-- Data memory read pointer has reached the write pointer. Separator between response data is the colon. Example of frame with F2C protocol: Command: Get current or oldest FIFO element for all probes Command to LB 134: * **CR Response from LB 134: * :50:03:0037:0002: :0030:Netto:0:cps:0:cts:DosisL1: :µsv/h: :µsv: :0:0:0:0.07:0000:lb1346*70* Meaning of parameters and measured value of the response: *FDV TDV Probe code Date Time : No.of FIFOelement : Zyclus number : 12xAsciihexStatus : M.Time : Nuclide1 : M.Value1 : unit1 : Intvalue1 : Intunit1 : Nuclide2 : M.value2 : unit2 : Intvalue2 : Intunit2 : IntTime : Rawdata1 : Background1 : Rawdata2 : Background2 :No.Zycles : LB1346 * Checksume * Example for transferred data during automatic data transfer to the PC: With LB 1342 Alpha-Beta contamination probe, ratemeter, 10s measuring time, 0 cycles (endless) :16:52 10 s a:netto 1.16E-03 cps >100 % 0.0 cts 0.0 h LB1342 RM bg:netto cps 2.2 % 0.0 cts 0.0 h :17:02 10 s a:netto 1.06E-03 cps >100 % 0.0 cts 0.0 h LB1342 RM bg:netto cps 2.2 % 0.0 cts 0.0 h :17:12 10 s a:netto 9.79E-04 cps >100 % 0.0 cts 0.0 h LB1342 RM bg:netto cps 2.2 % 0.0 cts 0.0 h Explanation: Date Time M.Time s Nuclidename1 M.value1 unit1 accuracy1 % Intvalue1 IntUnit1 IntTime h LB-Number Mode Nuclidename2 M.value2 unit2 accuracy2 % Intvalue2 IntUnit2 IntTime h 140

151 11. Appendix With LB 1342 Alpha-Beta contamination probe, Counter/Timer, 10s measuring time, 3 cycles Explanation: LB1342 (1) (LB Number of probe) , 16:36:03 (Date and Time) NE 0.0 cps 0.0 cps 600 s (Background and BG Time) Netto cps (C-Factor and alarm threshold) Netto cps (C-Factor and alarm threshold) :36:13 10 s a:netto cps % 0.0 cts 0.0 h LB1342 ZT bg:netto cps 13.5 % 0.0 cts 0.0 h :36:23 10 s a:netto cps % 0.0 cts 0.0 h LB1342 ZT bg:netto cps 10.9 % 0.0 cts 0.0 h :36:33 10 s a:netto 0.0 cps % 0.0 cts 0.0 h LB1342 ZT bg:netto cps 11.1 % 0.0 cts 0.0 h :36:33 30 s a:netto cps 70.7 % 0.0 cts 0.0 h LB1342 ZT M bg:netto cps 6.7 % 0.0 cts 0.0 h Explanation: Date Time M.Time s Nuclidename1 M.value1 unit1 accuracy1 % Intvalue1 IntUnit1 IntTime h LB-Number Mode Nuclidename2 M.value2 unit2 accuracy2 % Intvalue2 IntUnit2 IntTime h The last two lines belong to the mean value over the three cycles. In a single-channel probe, e.g. doserate probe, the measured values are missing in the second row. 141

152 11. Appendix 11.6 Parameter Locking with Jumper J3 There may be the need, with the internal and external dose rate probe, to protect certain parameters from being changed by means of a hardware interlock, e.g. calibration factor, background, dead time. Jumper J3 can be used for this purpose. If this jumper is closed, the necessary parameters cannot be changed via the keyboard nor via the interfaces. Normally, the jumper is open. The following PCB layout of the processor board shows the position of jumper J3. Figure 11.1: Position of jumper J Pin Assignment of the Fischer Sockets 11 pin Fischer socket: external probe Pin number Meaning 1 Counting pulse 1, differential input 1 A 2 Counting pulse 2, differential input 2 A 3 Ground 4 + 5V output for probes 5 SDA for EEPROM in probes 6 Control voltage for the HV of probes 7 Code input resistance 8 SCL for EEPROM in probes 9 differential input 1 B 10 differential input 2 B 11 Control input normal - differential counting signal (0 volts = differential input, open = normal counting signal, TTL) 142

153 11. Appendix 6 pin Fischer socket: external relay or RS485 interface Pin number Meaning 1 Relay terminal (transistor side) 2 +5 Volts for relay, max. 50 ma 3 Ground 4 A line for RS485 5 B line for RS485 6 Ground 2 1 Figure 11.2: Pin assignment of the 6-pin Fischer socket (type DEU104A ) 3 pin jack plug socket Connection for standard headphones, 3 pin For 3.5 mm diameter plug 3 pin power supply connector, socket Please use only Berthold power supply, 6 VDC, 1.5 A USB host connector To connect a USB memory stick USB device connector To connect a PC or notebook for data communication 143