X-rays see all X-ray computed microtomography (µct) a novel technique available at CERN for material and metrological inspection

Transcription

1 X-rays see all X-ray computed microtomography (µct) a novel technique available at CERN for material and metrological inspection Mariusz Jedrychowski EN/MME-MM

2 Introduction of new technique at CERN 12/12/2017 Shipment of Zeiss Metrotom CT 1500 to Bdg The lead-shielded closed-cabinet system came assembled in a 8100 kg truck pallet. 16/05/2018 Article on CERN Bulletin X rays see all 2

3 Open Day 6 th June X rays see all 3

4 What we can see with X-rays? An x-ray radiograph of A Misereuse Accroupie Photography by Craig Boyko/Art Gallery of Ontario Wilhelm Roentgen X rays see all 4

5 What we can see with X-rays? Voids / filling imperfections Brazing inspection Molibden-Graphite prototype collimation material for HL-LHC (WP5-Collimation ARIES) High X-ray absorption inclusions Electric circuit X rays see all 5

6 µct outstanding possibility to see and analyse in 3D Inclusion analysis for Mo-Gr samples X rays see all 6

7 µct outstanding possibility to see in 3D Superconducting cable for ITER project Voltage: 225 kv, Distance: 160 mm Voxel size: 50 µm, Projections: 2000, Integration time: 2 s, Measurement time: 2.5 h Top View Front View X rays see all 7

8 µct outstanding possibility to see in 3D Superconducting cable for ITER project X rays see all 8

9 µct outstanding possibility to see in 3D Superconducting cable for ITER project X rays see all 9

10 µct outstanding possibility to see in 3D CLIC Spiral Load 3D printed titanium object Voltage: 220 kv, Distance: 750 mm, Voxel size: 111 µm, Projections: 2050, Integration time: 1000 ms, Measurement time: 1.5 h X rays see all 10

11 Overview 1. X-ray computed tomography Short introduction Possibilities: NDT, metrology 2. Zeiss Metrotom CT specification 3. Software 4. Applications gallery 5. X-rays see all. How far we can see with µct in practice? 6. Image processing techniques developed at CERN X rays see all 11

12 X-ray computed (micro)tomography - µct Tube/detector distance determines the available measuring range: Flat image detector high-resolution: 2048 x 2048 pixels Projections 2D radiography Piece Regions with different X-ray absorption X-ray tube determines the range of applications: a smaller focal spot is used for high resolution, a higher voltage is used for more absorbent (denser/thicker) pieces Rotary table Precision axes The workpiece can be moved on four axes with extreme precision provided by coordinate measuring technology which, in result, allows metrology measurements X rays see all 12

13 X-ray computed (micro)tomography - µct 30 cm X rays see all 13

14 X-ray computed (micro)tomography - µct 22.5º 3D reconstruction 3D set of grey level voxels Projections 2D radiography X rays see all 14

15 Zeiss Metrotom CT X-ray generator Detector Sample holder Rotary table X rays see all 15

16 Zeiss Metrotom CT Specification Microfocus X-ray tube: Max. voltage 225 kv Max. current 3000 µa Max power 500 W Min. focal spot size 7 µm High resolution flat panel imager: 40 x 40 cm 2048 x 2048 pixels, 16 bit Material Polymer > 300 Aluminium 300 Titanium 200 Steel 50 Copper Max. through thickness [mm] Tube-detector distance: 1375 mm Max. spatial resolution: 4 μm Inoptimum conditions: small piece and contrasting materials. Typically voxel size is 10 to 100 μm Max through thickness Length measurement error [µm]: 9 μm + L/ X rays see all 16

17 Sample size vs voxel size extended field of view Carbon piece for ALICE detector Horizontal and vertical extensions used, 5 scans merged, Voltage: 190 kv, Distance: 437 mm, Voxel size: 65 µm, time: 6.5 h CT data size: 112 GB 70 cm Projection: 80 Surface mesh X rays see all 17

18 Analysis possibilities provided by CT data Obtained CT data are stored in form of 3D lattice of voxels that allows a wide range of analyses to be performed: 1. 2D Cross-sections 2. 3D Qualitative visualization 3. Separation of different parts in a sample - grey level value segmentation 4. Particle analysis (size, position and shape descriptors) 5. Weld assessment 6. Surface mesh extraction 7. Wall thickness 8. Advanced applications: classification, quality control, corrections for additive manufacturing settings, metrology measurements, FEM simulations based on CT data X rays see all 18

19 Software X rays see all 19

20 NDT Applications qualitative observations Copper micro Nozzle Beam hardening 3 cm 3D volume with clipping plane Voltage: 220 kv, Distance: 165 mm, Voxel size: 26 µm, Projections: 1750 Image avg.: 3 images Measurement time: 3 h X rays see all 20

21 NDT Applications qualitative observations 11 T magnet coil 80 cm 3D volume side view Voltage: 225 kv, Distance: 470 mm, Voxel size: 70 µm, Projections: 3000, Measurement time: 2 h X rays see all 21

22 NDT Applications qualitative observations 1.5 cm Connector in cryogenic instrumentation for LHC Voltage: 220 kv, Distance: 90 mm, Voxel size: 15 µm, Projections: 2050, Measurement time: 2.5h X rays see all 22

23 NDT Applications electronics Electronic component for ATLAS Forward Proton Detector Shorts ground-high voltage cable due to air bubbles found inside ATLAS Chip Aim: to understand issues related with IC packaging problem 1 cm 2.5 cm Voltage: 220 kv, Scan time: 1 h 10 min, Voxel size: 23 µm 3D volume and Top View cross-section Voltage: 215 kv, Distance: 55 mm, Voxel size: 9.64 µm, Projections: 2050, Integration time: 2 s, Measurement time: 2.5 h X rays see all 23

24 NDT Applications Porosity/Inclusion analysis Inclusion analysis for Mo-Gr samples Porosity in brazed layers of NA62 connector 1.5 cm X rays see all 24

25 NDT Applications Porosity analysis Test piece Filling Conformity with Unrolled brazing surface identification % EN ISO quality level C 1 >90% YES 2 >95% YES 3 >90% YES Copper brazed with steel 4 >90% YES 5 >85% YES 6 90% YES 2.5 cm brazed connections for R2E-LHC X rays see all 25

26 NDT Applications Wall thickness analysis Analysis of wall thickness of ALICE aluminium tubular segments 90 cm X rays see all 26

27 NDT Applications quantitative observations PCB with socket Aim: to understand issues related with loosen connection between socket and plug Voltage: 220 kv, Distance: 150 mm, Voxel size: 23 µm, Projections: 2050, Integration time: 2000 ms, Measurement time: 2.5 h Comparison: bad vs good socket X rays see all 27

28 NDT Applications quantitative observations CLIC Spiral Load Voltage: 220 kv, Distance: 750 mm, Voxel size: 111 µm, Projections: 2050, Integration time: 1000 ms, Measurement time: 1.5 h Surface rendering X rays see all 28

29 Metrology Applications 1 Importation of tomographic data on Calypso 2 Preparation measurement program 3 Use of specific Calypso algorithms such as Curve, Freeform for surface measurements of Freeform shapes (impossible on VG Studio) 4 Same program than CMM: possibility to pass from CT to CMM for the same part X rays see all 29

30 Metrology Applications CLIC Spiral Load Nominal-Actual Comparison X rays see all 30

31 Applications - metrology Titanium printed spring with Zirconia sphere Aim: Metrology measurements in order to quantify sphericity and roundness of the interface between sphere and spring 0.5 cm Projection: 90 2D cross-section Voltage: 215 kv, Distance: 55 mm, Voxel size: 9.64 µm, Projections: 1600 Image avg.: off, Integration time: 2000 ms, Measurement time: 1 h 3D volume with clipping plane X rays see all 31

32 Applications - metrology Titanium printed serpentine Aim: Metrology measurements for machining purpose estimation of thickness to be removed 3 scans merged Voltage: 215 kv, Distance: 186 mm, Voxel size: µm, Measurement time: 4 h 12 cm 3D volume with clipping plane X rays see all 32

33 Voxel size (Resolution) What is the voxel size for my sample? It depends on: 1. magnification (x position) / sample size 2. beam intensity / Image Contrast / Image Quality focal spot size (micro focus nano focus X-ray tube) beam filtration 3. sample orientation acquisition time and data size resolution vs detectability X rays see all 33

34 1. Magnification / voxel size Tube/piece/detector distances magnification M = D/x Object A cube defined by W x W x W is considered 410 Top View X - ray tube x W Detector D = 1375 mm W = 2048 * voxel_size (assuming that detector area is fully filled in by object projection) W / x = 410 mm / D (from Thales relation) voxel_size [µm] = 410/1375 * x [µm] /2048 = * x [mm] X rays see all 34

35 1. Magnification voxel size vs sample size Distance [mm] Voxel size [µm] W [mm] ( Sample size ) Magnification But this is the best case. In practice sample is not perfectly aligned with detector center/plane. Also, because of maximum thickness to be passed through by X-rays (tilted orientation). Hence, it has to be placed further away from the X-ray tube in order to decrease magnification (fit inside projection frame) X rays see all 35

36 2. Influence of focal spot size Point Source Small Focal Spot Large Focal Spot Object Image Detector penumbra Focal spot size has to be adjusted in respect to object size in order to avoid blurred projections X rays see all 36

37 2. Effect of focal spot size blurred projections X rays see all 37

38 2. Spot size blurred projections Spot size = 90 µm Current = 500 µa Voltage = 180 kv Magnification = X rays see all 38

39 2. Spot size blurred projections Spot size = 36 µm Current = 200 µa Voltage = 180 kv Magnification = X rays see all 39

40 2. Spot size sharp projections Spot size = 7 µm Current = 50 µa Voltage = 180 kv Magnification = X rays see all 40

41 2. Spot size reconstructed thin tungsten wire voxel size 9.3 µm Spot size = 7 µm Spot size = 46 µm X rays see all 41

42 3. Beam intensity why beam has to be filtered? Beam hardening (BH) artefact Main reason of BH Uncorrected BH Corrected BH X-rays see all 42

43 3. Beam intensity why beam has to be filtered? Theoretical energy spectra for 420-kV X-ray source with tungsten target, calculated combining 5-keV intervals. Spectra consist of continuous Bremsstrahlung and characteristic K-series peaks at and kev. R.A. Ketcham, W.D. Carlson / Computers & Geosciences 27 (2001) X-rays see all 43

44 3. Beam intensity Filtering of Energy distribution No filter, 220 kv, 400 µa, spot size = 88 µm Cu = 2 mm, 220 kv, 400 µa, spot size = 88 µm No filter, 180 kv, 490 µa, spot size = 88 µm Cu = 2 mm, 180 kv, 490 µa, spot size = 88 µm X rays see all 44

45 3. Beam intensity how it can be increased We take advantage of detector capabilities in order to increase signal registered Solution Consequence Longer integration time => Longer acquisition Higher gain (signal amplification) => increased noise Binning 2 x 2 => reduced CT voxel size (increased detector pixel size, 1024 x 1024 px instead of 2048 x 2048 px) X rays see all 45

46 3. Beam intensity [Gain = 16, Integration time = 2 s] Cu = 2.5 mm, 220 kv, 488 µa, spot size = 70 µa Cu = 2.5 mm, 220 kv, 45 µa, spot size = 7 µa Contrast = Max Intensity Min Intensity X rays see all 46

47 4. Sample orientation Feldkamp reconstruction artefact electronic components in power amplifiers for LIU-SPS project X rays see all 47

48 Sample orientation Feldkamp reconstruction artefact X rays see all 48

49 Sample orientation Feldkamp reconstruction artefact X rays see all 49

50 4. Sample orientation Feldkamp reconstruction artefact X rays see all 50

51 Developed Applications Pore segmentation algorithms Several image processing methods were developed in order to estimate porosity of brazing Final result Standard approach Developed algorithm X rays see all 51

52 Developed Applications CT vs Ultrasound inspection A method was developed in order to compare porosity estimation obtained from µct measurements and ultrasound inspection Voltage: 215 kv, Distance: 90 mm, Voxel size: 15 µm, Projections: 1600, Measurement time: 2 h Defects found by UT (red areas on the left) and CT (dark areas on the right) X rays see all 52

53 Developed Applications X-ray radioscopy Sphere diameter < 20 µm! Chip0FF Chip1FF Chip2FF Chip3FF Chip4FF Chip5FF Chip6FF Chip7FF Chip8FF Chip9FF X rays see all 53

54 Developed Applications X-ray radioscopy A Flat Field algorithm was developed at CERN in order to perform manual X-ray radioscopy using Zeiss Metrotom CT standard scan mode imposes sample rotation which limits resolution in the case of a flat sample. Corrected Image = (Raw_Projection Dark_Frame)/(Bright_Frame Dark_Frame) RAW projection Bright Frame (Gain) Dark Frame (no beam) Corrected projection X rays see all 54

55 Developed Applications X-ray radioscopy Width = 15 cm X rays see all 55

56 Summary 1. NDT New possibilities to analyse quantitatively and qualitatively internal structure of materials 2. METROLOGY Complementary to CMM and other measurement means Good accuracy for many parts 3. Custom Algorithms and image processing methods were developed. One of them will be presented at the ict Conference 2019 in Padova X rays see all 56

57 Thank you for your attention!

58 Developed Applications Pore segmentation algorithms Several image processing methods were developed in order to estimate porosity of brazing Standard threshold CLAHE Noise reduction Auto local threshold Binary cleaning Final result X rays see all 58

59 Applications - metrology Titanium sample 3D printed and polished (designed for crab cavity) Aim: 1. Comparison of 3D printed sample with CAD model used for printing. Voltage: 220 kv 2. Estimation of surface thickness removed during following polishing Distance: 755 mm Voxel size: 112 µm Projections: 2200 Image avg.: 3 images Integration time: 1 s Measurement time: 2 h Projection: 90 3D volume with clipping plane Nominal/actual comparison with CAD model X rays see all 59