1. Imaging Properties of the Medipix2 System exploiting Single and Dual Energy Thresholds L. Tlustos 1, R. Ballabriga 1, M. Campbell 1, E. Heijne 1, k Kincade 2, X. Llopart 1, P. Stejskal 3 1 Ph Department, CERN, Geneva, Switzerland 2 University of Canterbury, Christchurch, New Zealand 3 Institute of Experimental and Applied Physics, Technical University of Prague, Czech Republic.

2. 27 September 2004Michael Campbell The Medipix2 Consortium  Institut de Fisca d'Altes Energies, Barcelona, Spain  University of Cagliari and INFN Section thereof, Italy  CEA, Paris, France  CERN, Geneva, Switzerland,  Universitat Freiburg, Freiburg, Germany,  University of Glasgow, Scotland  Universita' di Napoli and INFN Section thereof, Italy  NIKHEF, Amsterdam, The Netherlands  University of Pisa and INFN Section thereof, Italy  University of Auvergne, Clermont Ferrand, France,  Laboratory of Molecular Biology, Cambridge England  Mitthogskolan, Sundsvall, Sweden,  Czech Technical University, Prague, Czech Republic  ESRF, Grenoble, France  Academy of Sciences of the Czech Republic, Prague  Universität Erlangen-Nurnberg, Erlangen, Germany  University of California, Berkeley, USA

3. 27 September 2004Michael Campbell Outline  Motivation and a brief overview of the Medipix2 system  MTF, NPS and DQE for a single photon counting system as a function of lower threshold  Imaging of an object using the energy window  Concluding remarks

4. 27 September 2004Michael Campbell Introduction and Motivation  Single photon counting provides clean images across a wide range of incoming photon fluxes  Flexible – many applications  Energy selective x-ray imaging possible  MTF, NPS and DQE as a function of threshold - Medipix2 readout chip and a 300  m thick Si sensor  First energy selective images of an object using a polychromatic source

5. 27 September 2004Michael Campbell Hybrid Pixel Detector Detector and electronics readout are optimized separately

6. 27 September 2004Michael Campbell Hybrid Pixel Detector - Cross Section

7. 27 September 2004Michael Campbell Charge sensitive preamplifier with individual leakage current compensation 2 discriminators with globally adjustable threshold 3-bit local fine tuning of the threshold per discriminator 1 test and1 mask bit External shutter activates the counter 13-bit pseudo-random counter 1 Overflow bit Medipix2 Cell Schematic

8. 27 September 2004Michael Campbell Medipix2 Cell Layout

9. 27 September 2004Michael Campbell Medipix2 Chip Architecture 256 x 256 pixels 10ms readout time

10. 27 September 2004Michael Campbell Medipix2 bump bonded to a 300  m Si sensor

11. 27 September 2004Michael Campbell Bumps of readout side

12. 27 September 2004Michael Campbell Bumps of readout side – close up

13. 27 September 2004Michael Campbell 90 Sr source scanned in real time 20 frames per second – limited by DAQ not chip

14. 27 September 2004Michael Campbell Calculated incoming spectrum and position of thresholds used Siefert FK-61-04x12 X-ray tube, W-target, 2.5 mm Al, V peak = 25 kV. Thresholds 9.1 keV 11.3 keV 12.8 keV 18.8 keV

15. 27 September 2004Michael Campbell Measures MTF @ various thresholds

16. 27 September 2004Michael Campbell NPS @ different thresholds NB. Dose changed from threshold to threshold to obtain good statistics

17. 27 September 2004Michael Campbell DQE @ different thresholds

18. 27 September 2004Michael Campbell Summary of measurements

19. 27 September 2004Michael Campbell Spectrum of X-ray source using energy window Threshold windows 1.4 keV 2.8 keV 4.2 keV Sn in bump bond 63% Ag in die attach glue Siefert FK-61-04x12 X-ray tube, W-target, 2.5 mm Al, V peak = 50 kV. Raw sum of counts in all 64 000 pixels versus global threshold Spectroscopic information – insight into environment

20. 27 September 2004Michael Campbell Image of a Swatch (16.1-19.6 keV)

21. 27 September 2004Michael Campbell Image of a Swatch (21.6-25.1 keV)

22. 27 September 2004Michael Campbell Image of a Swatch (27.1-31.4 keV)

23. 27 September 2004Michael Campbell Image of a Swatch (40.0-43.5 keV)

24. 27 September 2004Michael Campbell Comparison (16.1 – 19.6 keV)21.6 – 25.1 keV) (16.1 – 19.6 keV) (21.6 – 25.1 keV)

25. 27 September 2004Michael Campbell Comparison (27.1 - 31.4 keV)21.6 – 25.1 keV) (27.1 - 31.4 keV) (21.6 – 25.1 keV)

26. 27 September 2004Michael Campbell Comparison (27.1 - 31.4 keV)40.0 - 43.5 keV) (27.1 - 31.4 keV) (40.0 - 43.5 keV)

27. 27 September 2004Michael Campbell Concluding remarks  The Medipix2 system offers clean particle imaging  MTF is typically 70% at pixel pitch. This can be enhanced by increasing threshold but at the expense of DQE  Energy window measurements provide insight into environment  Quantitative evaluation of the imaging properties using the energy window in preparation  Maybe the window should be used to exclude given energies!  And finally, a message for those who doubt the future of photon counting energy sensitive imaging systems…..

28. 27 September 2004Michael Campbell …the clock is ticking! < 1 frame/sec. Limited by DAQ software

29. 27 September 2004Michael Campbell Acknowledgements  Fellow members of the Medipix Consortium www.cern.ch/medipix  Colleagues from Nikhef for Muros2 readout system J. Visschers H. Verkooijen  Colleagues the Naples group for Medisoft4.0 P. Russo G. Mettivier M.C. Montesi