High Energy Digital Radiography & 3D-CT for Industrial Systems

Transcription

1 DIR International Symposium on Digital industrial Radiology and Computed Tomography, June 25-27, 2007, Lyon, France High Energy Digital Radiography & 3D-CT for Industrial Systems Non-Destructive Evaluation (N.D.E.) at A.W.E. Aldermaston UK Richard Watson Senior Engineer NDE British Crown 2007/MOD Page 1 of 24

2 High Energy Digital Radiography Introduction CT imaging High Energy definition / Facilities Digital Detectors Test objects, alignment, shielding Position and motion control Experiments, collimation, filters Data handling Results Summary British Crown 2007/MOD Page 2 of 24

3 CT Imaging An enormous amount of useful data is lost in the process of projecting 3D Data onto a 2D image plane. Additionally, overlaying parts within complex assemblies can make radiographic film interpretation difficult, a CT slice enables a different view of the data for analysis Conventional Film Radiograph CT slice Image British Crown 2007/MOD Page 3 of 24

4 CT Imaging Fan Beam System X-ray Computed Tomography (CT) provides the 3rd dimensional view. AWE currently has a number of CT systems. 2D array CT Systems British Crown 2007/MOD Page 4 of 24

5 High Energy Digital Radiography High Energy Definition: > 1MeV In the medical imaging sector, next generation scintillator materials, Am- Si flat panel imaging sensors together with major advances in CCD technology promise high fidelity, high resolution digital images at lower X-ray dose to patients. The same technology is being developed for industrial applications. Most industrial systems are designed to work at significantly lower energies typically KeV with a maximum up to 300KeV Our systems use much higher energies typically 4 10 MeV British Crown 2007/MOD Page 5 of 24

6 High Energy Digital Radiography Facilities at AWE 2 Facilities have been used during development. 4.2 MeV Linac - NDE Development use 2 10 MeV Minac NDE Development use Some limited work has been done with Computed Radiography systems at high energy X-Ray set 4MeV to 10MeV Detector Collection of image data Object British Crown 2007/MOD Page 6 of 24

7 Digital Radiography Detectors Scintillator 45 turning mirror Camera Pb Shielding We are currently developing DRTR & CT systems for the radiographic imaging of components & assemblies. Systems include a lens coupled, glass scintillator, X-ray energies typically 4MeV - 10 MeV. Hammamatsu ORCA 1280 x 1024 pixels 14 bit detector Image size 2.5MB British Crown 2007/MOD Page 7 of 24

8 Digital Radiography Detectors Amorphous silicon AmSi flat panel detector X-ray energies typically 4MeV - 10 MeV. Based on Varian Paxscan 4030 High Energy coating, X-Tek 3200 x 2304 pixels 12 bit detector Image size 14.7MB British Crown 2007/MOD Page 8 of 24

9 Digital Radiography Detectors Computed Radiography An example CR film scanner using Phosphor plates instead of film for high energy Radiography Problems with noise on image System used :- High Resolution screens (50µm), 4175 x 5084 pixels 12 bit detector Image size 60.7 MB This system was lent to us by another section at AWE British Crown 2007/MOD Page 9 of 24

10 High Energy Test Objects Design of the Radiographic Test Pieces High Z section (4.2 MeV) Low Z section (420KeV) Interlocking cylinders 125mm Al block Tungsten British Crown 2007/MOD Page 10 of 24

11 High Energy Test Objects Copper Vessel with Steel insert Side view Top view Base view British Crown 2007/MOD Page 11 of 24

12 High Energy Radiography Alignment, Shielding, Motion control Shielding 100mm Pb Camera system 1.1 tonne housing 150mm Pb AmSi FPD 1.5 tonne housing Alignment Beam Detector Turntable Object Motion Control Precision Turntables, with rotation and one translation axis. British Crown 2007/MOD Page 12 of 24

13 High Energy Radiography Collimation, Filters, scatter Collimation Tungsten collimator at source Filters 1 5 mm at source; 3mm in normal conditions 0.5 2mm Cu at detector Scatter Back scatter Component internal scatter British Crown 2007/MOD Page 13 of 24

14 Data Handling / Image Processing Digital Camera & Flat Panel Detector (FPD) Frame acquisition time and read out Black & White References 1Deg Steps : 360 images Frame averaging Typical data set sizes Camera 0.9 GB FPD 5.2 GB Now tending to use smaller rotational steps, typically 0.4 (900 images), thus larger data requirements; Camera 2.25GB FPD 13.23GB Utilising methods to reduce data handling British Crown 2007/MOD Page 14 of 24

15 Data Sets Typical sizes Slices Dataset size in MB Pixels (x) (Mb) dataset 1024s, 8b 1024s, 16b British Crown 2007/MOD Page 15 of 24

16 Results Images from some experiments:- Example graphs from FPD system taken with 4.2MeV Linac Digital Radiograph from FPD taken with 6Mev Minac Rotational Sequence British Crown 2007/MOD Page 16 of 24

17 Results Example graph from CR system taken with 6MeV Betatron British Crown 2007/MOD Page 17 of 24

18 Results Example graph from CR system taken with 4.2MeV Linac British Crown 2007/MOD Page 18 of 24

19 Results Images from some experiments:- Slice plane Slice view - Animation CT data set created from FPD system taken with 10MeV 8MeV British Crown 2007/MOD Page 19 of 24

20 Results Images from some experiments:- 3D CT view - Animation CT data set created from 2D array system taken with 10MeV 8MeV British Crown 2007/MOD Page 20 of 24

21 Further Data Set - AMBER Steel vessel, created as part of a Model Based Engineering project (amber) Amber 8bit animation.avi Amber 8bit slice through Z axis.avi Amber 8bit with slice plane.avi Amber vgs.avi CT data set created from Camera system taken with 10MeV 6MeV British Crown 2007/MOD Page 21 of 24

22 Image Processing & CT Acquisition PC advances in recent times have enables much larger data sets to be processed within a reasonable time. We currently use a 64bit PC with 16GB RAM, 2 x dual core CPUs, which can reconstruct a 1k cube in < 10 minute Multi-rotation enables objects to be scanned which are larger than the detector width. Image stitching when scanning large objects Measurements with 3D volumetric data VGS & Haptics British Crown 2007/MOD Page 22 of 24

23 Future Work We are doing further experiments to help characterise our systems and to further improve the resolution. We are investigating Neural networking as a means of helping to identify features within a radiograph Explore the use of Monte Carlo N Particle (MCNP) methods to improve the results Extend the range of test components and materials used to validate the systems Looking at other acquisition systems, interested in CR (computed radiography) & LDA (Linear Diode Array) for high energy work. Haptics Tactile tool to interact with and analyse & use as a measurement tool. British Crown 2007/MOD Page 23 of 24

24 High Energy Radiography & 3D-CT for Industrial Systems - Summary 2 Main High energy sources used, 3 rd used only for CR 4.2MeV Linac 6 10 MeV Minac 6 MeV Betatron 2 Detectors (DR & CT), 3 rd Images only 14bit CCD Camera & Scintillator 12bit Flat Panel AmSi Detector High Res CR Plates 2 Acquisition systems (commercial) British Crown 2007/MOD Page 24 of 24

25 High Energy Digital Radiography & 3D- CT for Industrial Systems Thank you for your time Any further questions? Richard Watson Senior Engineer NDE AWE Aldermaston UK British Crown 2007/MOD Page 25 of 24