1. IEAP CTU Prague 8 th December, 2004Tomáš Holý Neutron tomography with Medipix-2 Tomáš Holý, Jan Jakůbek, Stanislav Pospíšil, Josef Uher

2. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Outline Tomography principles Filtered backprojection algorithm Adaptation of Medipix-2 for neutron detection Examples of micro-tomography reconstructions Comparison with Medipix-1 Conclusion and outlook

3. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Tomography measurement Medipix-2 detector Sample Step motor Slice of sample and its projection on detector Parallel neutron beam

4. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Neutron transmission Neutron beam intensity attenuation: a(x,y) – attenuation coefficient function Sample attenuating the beam Projection on detector plane Reconstruction of a(x,y)

5. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Parallel projections Projection P (t) x y Object slice a(x,y) Radon transform of a(x, y) Projection at

6. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Filtered back-projection algorithm Based on Fourier Slice Theorem: S (w) is Fourier transform of projection P (t) A(u, v) is Fourier transform of a(x,y) Projections are filtered with ramp filter |w| and backprojected along angle to slice reconstruction Additional smoothing of projections can improve noise level Filtered projections Reconstruction

7. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Filtered back-projection algorithm

8. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Medipix-2 device with converter Reaction: 6 Li + n (2.05 MeV) + 3 H (2.72 MeV) Cross section: 940 barns (0.0253 eV) 256x256 pixels, 55x55 µm 2 each, active area 1,98 cm 2 Each pixel contains 2 discriminators, 2x3-bit thresholds adjustments and 13-bit pseudo-random counter 300 µm thick silicon detector Converter layer ( 6 Li) Silicon detector Bump bonding Readout chip

9. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Thermal neutron source NEUTRA station of spallation neutron source SINQ in Paul Scherrer Institute, Villigen, Switzerland Intensity about 10 7 neutrons/cm 2 s at proton accelerator current of 1 mA and proton energy of 590 MeV Beam cross section is 40 cm in diameter

10. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Lemo connector Reconstruction from 100 projections Each projection 150 s

11. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Potentiometer Reconstruction from 100 projections Each projection 150 s

12. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Tooth Reconstruction from 100 projections Each projection 150 s

13. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Cartridge – comparison with Medipix-1 Reconstruction from 48 projections Each projection 90 s Medipix-1 64x64 pixels Each pixel 170x170 µm 2 300 µm thick silicon detector Neutron source Horizontal channel of the LVR-15 nuclear research reactor at Nuclear Physics Institute of the Czech Academy of Sciences at Rez near Prague. Intensity ~10 7 neutrons/cm 2 s (at reactor power of 8MW) Beam Cross section: 4 mm x 60 mm The divergence of the beam is < 0.5°

14. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Cartridge – Medipix-1 with X-rays Reconstruction from 48 projections Each projection 30 s Medipix-1 64x64 pixels Each pixel 170x170 µm 2

15. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Cartridge – Medipix-2 Reconstruction from 100 projections Each projection 150 s

16. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Conclusion and outlook Medipix-2 offers excellent properties for neutron micro- tomography – very good spatial resolution and unlimited dynamic range Tomography expertiments requires synchronization of several devices. In Medisoft4 is no way to synchronize actions with other programs => complete acqusition is necessary => time demanding offline analysis It is necessary to develop flexible software for acquistion control allowing other application to access Medipix-2 device and providing interprocess synchronization

17. Institute of Experimental and Applied Physics Czech Technical University in Prague IEAP CTU Prague 8 th December, 2004Tomáš Holý Basic user interface (MpxCtrlUI.dll) Data sharing and process synchronization plugin Custom plugins (experiment specific) Communication plugins Client interface library User application Plugins Architecture Muros + NI card Muros HW library (MpxHw.dll) Control library (MpxCtrl.dll) Manager (MpxManager.dll) Medipix Loader (MpxLoader.exe) USB HW library, …Dummy HW library, … USB User application Hardware independent access to Medipix Auto-initialization and chipboard configuration handling Multiple acquisition handling (custom size stream/frame buffer, integral buffer, thread-level buffer synchronization) Callback function registration Implemented in C++, limited number of platform dependent calls, no MFC Hardware independent access to Medipix Auto-initialization and chipboard configuration handling Multiple acquisition handling (custom size stream/frame buffer, integral buffer, thread-level buffer synchronization) Callback function registration Implemented in C++, limited number of platform dependent calls, no MFC Plugin management (plugin registration, initialization, …) Provides access to MpxCtrl library, Windows messages (for convenient MFC plugins usage), tray menu Provides communication between plugins Implemented in C++ Load-time dynamic linking of MpxCtrl.dll Run-time dynamic linking of registered plugins Plugin management (plugin registration, initialization, …) Provides access to MpxCtrl library, Windows messages (for convenient MFC plugins usage), tray menu Provides communication between plugins Implemented in C++ Load-time dynamic linking of MpxCtrl.dll Run-time dynamic linking of registered plugins Medipix Manager initialization Tray menu building Forwards all incoming Win messages to Medipix Manager Load-time dynamic linking of MpxManager.dll Implemented in C++, MFC Medipix Manager initialization Tray menu building Forwards all incoming Win messages to Medipix Manager Load-time dynamic linking of MpxManager.dll Implemented in C++, MFC Basic user interface for Medipix Control Chipboard configuration management Basic data acquisition control Simple data preview Custom plugin optionally loaded by manager Load-time dynamic linking of MpxManager.dll Implemented in C++ (MFC regular DLL) Basic user interface for Medipix Control Chipboard configuration management Basic data acquisition control Simple data preview Custom plugin optionally loaded by manager Load-time dynamic linking of MpxManager.dll Implemented in C++ (MFC regular DLL) Exclusive access to HW Hardware detection and diagnostics Exports set of basic functions for hardware independent access to Medipix Single threaded Implementation in C Exclusive access to HW Hardware detection and diagnostics Exports set of basic functions for hardware independent access to Medipix Single threaded Implementation in C