A DATA ANALYSIS CODE FOR MCNP MESH AND STANDARD TALLIES

Transcription

1 Supercomputng n uclear Applcatons (M&C + SA 007) Monterey, Calforna, Aprl 15-19, 007, on CD-ROM, Amercan uclear Socety, LaGrange Par, IL (007) A DATA AALYSIS CODE FOR MCP MESH AD STADARD TALLIES Kenneth A. Van Rper Whte Roc Scence P. O. Box 479, Los Alamos, M vr@rt66.com ABSTRACT We descrbe a computer program, provsonally named Krempe, developed for the analyss and presentaton of mesh and other talles from Monte Carlo radaton transport codes MCP and MCPX. Data along a lne can be extracted from mesh talles and the profle plotted. Peas n the profle can be ftted to a Gaussan. We descrbe the use of such a ft to obtan a measure of the spatal spreadng of a partcle beam. Smoothng functons are avalable to average over nose. Addtonal fttng functons are avalable for peas n an energy spectrum. Talles as a functon of energy or other varables can be plotted n a varety of styles. Multple talles can be shown together, each wth an optonal ndependent scalng factor. A new tally can be defned from lnear combnaton of two talles. Data s mported from MCTAL fles. A lst shows avalable talles.a sequence of talles can be plotted n three dmensons. Key Words: MCP, MCPX, Mesh Tally 1. ITRODUCTIO Whte Roc Scence recently nvolved n a smulaton project that ncluded characterzaton of the spatal profle of a partcle beam and analyss and comparson of talles as a functon of energy. A method for quantfyng the spatal spreadng of the beam was requred. The large volume of tally data requred a means to qucly plot, compare, and annotate the data. Partners n the project were nterested n nnovatve and effectve technques for presentng the results. We developed the Krempe program to plot spatal profles extracted from mesh talles and ft Gaussan curves to peas found n the profles. The Full Wdth at Half Maxmum (FWHM) of the Gaussan ft s a measure of the beam spreadng. The program ncludes features for plottng regular talles such as flux versus energy. A number of fttng functons are avalable for analyss of these spectra. The Monte Carlo radaton transport code MCPX.50[1] was used for the wor; the wor descrbed here s also applcable to other versons of MCPX and to MCP[].. MESH TALLY PROFILES Mesh talles gve the values of a quantty, such as flux or dose, on a rectangular, cylndrcal, or sphercal grd. The data can be read from mesh tally fles wrtten by MCPX and MCP and

2 Kenneth A. Van Rper from the MCTAL fles wrtten by both codes that contans all tally data. The MCPX mesh tally fle MDATA must frst be converted to ASCII format..1. Data Extracton The profle data s extracted from the mesh talles by varyng one coordnate wth the others held fxed. A summed profle s also avalable where one coordnate s held fxed and the data s summed over the second drecton. For example, one can sum (or average) the data n the Y drecton for each X value for a fxed value of Z. The user can specfy the fxed coordnates by ether value or mesh ndex. Profles can be extracted from both Cartesan and cylndrcal mesh talles. The extracted data can be wrtten to a fle as well as plotted. The relatve errors along wth the data can be extracted. For extracton n the radal drecton of a cylndrcal mesh tally, the data can be repeated n the negatve radal drecton. Ths mrrorng of the data s useful when the values pea at R = 0 so that a full Gaussan ft can be appled... Pea Fttng The user must locate the pea n the plot by marng a Regon of Interest (ROI) around the pea. The marng s made wth the mouse or by readng a fle contanng the lmts of the ROI. The ROI s shown as a colored regon below the curve. The ponts wthn the ROI are then ft to a Gaussan x B y = A exp C (1) where y s the flux or other data from the mesh tally and x s the value of the chosen free coordnate. The parameters A, B, and C are determned by the fttng algorthm usng the Levenbertσ = 1 Marquardt method. Each pont s weghted by y thereby gvng greater sgnfcance to the pea values. C determnes the wdth of the functon. An example of a ftted pea s shown n Fg. 1. The Cartesan mesh tally s from a smple model of a proton beam drected nto a box flled wth water. The data was extracted n a drecton perpendcular to the beam. Addtonal fttng functons are dscussed n the next secton. The program shows the fttng parameters n equaton 1 together wth ther uncertantes, the FWHM, the Ch Square value of the ft, and the sum of the devatons of the data from the ft. A resdual plot showng the dfference between the data and the ft can be shown below the man plot. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 /10

3 A DATA AALYSIS CODE FOR MCP MESH AD STADARD TALLIES Proton Beam Into Water 5x10-5 4x10-5 Gaussan Ft A = 4.5e-5, B=-.6, C = 8.6 3x10-5 x10-5 Partcles / cm^ / s x10-6 4x10-6 3x10-6 x Plottng Styles Y (cm) Fgure 1. Mesh Tally Profle (blac), ROI (yellow), and Gaussan ft (red). The data can be plotted bnned as shown n Fg. 1 or smply as connected ponts. For ether opton, the profle can be plotted as a lne, ponts (Fg. ), or a flled regon. Error bars, vsble n Fg. 1, are avalable to show the relatve errors from the mesh tally. Any number of addtonal curves can be added to the plot, each wth a dfferent color. Scalng factors and offsets can be appled to the comparson curves n both the horzontal and vertcal drectons. The user can set the color and vsblty of the varous plot components and choose lnear or logarthmc scales for the axes. The plots can be exported as PostScrpt or btmap fles. Fgs. 1 and 4 were saved as PostScrpt and converted to a PDF fles usng Adobe Acrobat Dstller. The PDF fles were then mported nto ths document. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 3/10

4 Kenneth A. Van Rper Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 4/10.4 Data Smoothng Several smoothng functons can be appled to the data. The smoothng may be made wth a smple averagng or wth a bnomal weghtng functon. The smoothed data Y for pont s () for odd order and orgnal data Y. For smple averagng,. For bnomal smoothng, (3) where (4) Fg. shows a smoothng functon (red curve) appled to nosy data (dar ponts). Fgure. Orgnal Data Ponts and Smoothed Curve., ' / / + = = Y a Y a / = 1 + = + + = / / / / a! )! (! m m n n m n =

5 A DATA AALYSIS CODE FOR MCP MESH AD STADARD TALLIES 3. TALLY PLOTS 3.1. Tally Lst Wndow The program can mport nontalles from one or more MCTAL fles. The tally lst wndow, shown n Fg. 3, dsplays the talles loaded. The user can select one or more talles to plot from the lst. Several column headngs have not been set wde enough to dsplay ther full text. The columns are Tally (tally number), Fle (MCTAL fle name), Partcle, Cell/Surf (cell or surface on whch the tally was taen), Segment, Cosne, Tme, Mult, User, and Type. The column wdths can be adjusted so that felds that reman the same can be hdden. The lst as dsplayed n Fg. 3 assumes talles plotted as a functon of energy. It can be set to use another quantty as the free varable. Fgure 3. Tally Lst Wndow The three lnes below the lst pertan to the selected tally (hghlghted tally number n the frst column): 1) The frst lne of the nput fle, ) the full path of the MCTAL fle, and 3) the tally comment (f any) defned wth the MCP FC nput lne. The Plot button shows the tally n a new plot and wndow. The Compare button shows the tally n an exstng plot (or a new plot f one does not exst). If more than one plot wndow s present, the last actve wndow s used for the comparson plot. Double clcng the tally number n the frst column results n ether a new plot or a comparson plot accordng to the chec boxes n the penultmate lne. The value n the Multpler feld affects the selected tally only. Changng the multpler and replottng adds a new curve to the plot rather than changng the exstng curve. The latter can be accomplshed on a dalog where multpler and offset factors for the comparson curves are set. The ndvdual multplers are n addton to any overall multpler than may be n effect. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 5/10

6 Kenneth A. Van Rper Tally selecton can also be made by readng a fle lstng the talles to be plotted. Each lne n the fle contans the nformaton shown n the tally lst as well as a strng for the legend and a multpler f desred. Defaults can be set for values that do not change. All entres are eyword drven. Multple plots and the names of PostScrpt fles for output can be defned n a sngle fle. 3.. Plot Annotaton Fg. 4 s a plot of the talles lsted n Fg. 3. The curves are dstngushed by color (lne style optons dashed, dotted, etc. wll be added n future versons). The lnes gvng the angle bns for each curve are entered n the Legend feld n the tally lst wndow. The text can be changed n the legend dalog and a header (Angle n Fg. 4) specfed. The dalog also controls whether or not the legend s shown. The legend can be postoned anywhere wthn the plot or to the rght of the plot (n whch case the horzontal extent of the graph s decreased). The poston of the legend s gven on the dalog n ether nches or centmeters; the full extent of the plot s assumed to be 11 Photons at Sol Surface Photons / cm^ / s x10-5 x x10-6 x10-6 Angle E (ev) Fgure 4. Plot of Talles Lsted n Fg. 3. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 6/10

7 A DATA AALYSIS CODE FOR MCP MESH AD STADARD TALLIES by 8.5 nches. One can also poston the legend wth the mouse. When wthn the plot, the legend can n a sngle column as shown or dvded nto multple columns. The plot ttle (Photons at Sol Surface n Fg. 4) s taen from the tally comment. The ttle and X and Y labels can be set on a dalog. The labels, ttle (unless overrdden by a tally comment), and legend header are remembered from graph to graph and between executons of the program Scalng The same plottng styles descrbed above are avalable for the tally plots, as s the applcaton of smoothng functons. The X and Y scales can be lnear or logarthmc. The plot scalng s set by the extent of the data. A small offset from the extremes of the data s used for the mnmum and maxmum vertcal scale. When comparson curves are added, the scalng can reman fxed or expand to accommodate the addtonal data. Overall multplers can be specfed n the X and Y drectons. In Fg. 4, an X multpler of 1000 s used to present the talles as a functon of energy n ev rather than the default of MeV. The multplers reman n effect from plot to plot and between executons of the program. The toolbar at the top of the program contans scalng buttons that Move the curves up or down eepng the same vertcal scalng Increase or decrease the vertcal scalng eepng the same mnmum Increase of decrease the vertcal scalng eepng the same maxmum Shft the curves left or rght Expand or decrease the horzontal scale Holdng down the control or alt eys decreases the amount be whch the scalng changes. Exact values for the lmts can be entered on a dalog. The horzontal buttons a greyed and thus not functonal when ther use would show no more data. For example, when the full X range s dsplayed, the decrease button s greyed. The horzontal expanson and contracton s centered on a vertcal cursor. An nformaton wndow shows the X and Y values (for the frst curve plotted) at the poston of the cursor Tally Combnng When two and only two talles are selected n the tally lst, the Combne button s present at the bottom of the tally lst wndow. The button shows a dalog n whch a new tally s defned as a lnear combnaton of the two selected talles. The new tally can be plotted or added to an exstng plot. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 7/10

8 Kenneth A. Van Rper 3.5. Fttng Functons Fgure 5. An ROI ft (yellow curve) wth a Gaussan (red curve) plus an exponental tal. In addton to the Gaussan, addtonal curves are avalable for fttng peas n an energy spectrum. The double Gaussan permts a dfferent wdth (parameter C n eq. 1) on ether sde of the pea. The Gaussan plus exponental tal ft s the sum of a Gaussan and a low energy exponental. A cutoff factor drops the tal contrbuton to zero as the pea poston s approached from below: A y = x B x B D x B C + exp exp E < x B A exp x B C (5) where A, B, C, and D are determned by the fttng algorthm, and the cutoff factor s. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 8/10

9 A DATA AALYSIS CODE FOR MCP MESH AD STADARD TALLIES [ x B ] = 1 exp 04. ( ). (6) Fg. 5 shows an ROI ft as a Gaussan plus an exponental tal. A plot of the ft resduals s shown below the man plot. Three addtonal functons ft the pea regon wth a Gaussan and no, 1, or the sum of exponental tals at lower energy. The pea regon s defned n terms of fractons of the heght or wdth of the ROI. Polynomal fts can be used for smooth curves An automatc pea search algorthm loos for peas n the spectrum and places an ROI around those found. The algorthm maes use of a generalzed second dfference method. Ths method dentfes the extent of peas by fndng a maxmum n a weghted average of the numercal second dervatve of the spectrum. 4. THREE DIMESIOAL TALLY PLOTS Sequences of talles can be plotted n three dmensons (3D). For a set of talles wth dfferent tme, cosne, or segment bns, the thrd dmenson s taen from the bn boundares. Otherwse, the user must specfy the separatons between the talles. Fg. 6 shows a 3D representaton of the talles shown n Fg. 4. A thrd dmenson can be added to a plane from a mesh tally based on the data values. The 3D plot s based on OpenGL. The user can rotate, scale, and move the mage wth the mouse and eystroes. Dfferent color schemes and plot styles are avalable. 5. STATUS AD DEVELOPMET PLAS The Krempe analyss code s presently under development and used by Whte Roc Scence. It runs on Wndows. Although t s used at present for data from MCPX and MCP, t can accept data from other sources n varous smple formats. It wll be made avalable to users after more testng and completon of documentaton. Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, 007 9/10

10 Kenneth A. Van Rper Fgure 6. 3D Plot of the Talles Shown n Fg. 4. REFERECES [1] L. S. WATERS, Edtor, MCPX User s Manual, Los Alamos atonal Laboratory Report TPO-E83-G-UG-X-0001, (1999). [] J. F. BRIESMEISTER, Edtor, MCP - A General Monte Carlo -Partcle Transport Code, Los Alamos atonal Laboratory Report LA M (000). Supercomputng n uclear Applcatons (M&C + SA 007), Monterey, CA, /10