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.

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

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

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

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

27 September 2004Michael Campbell Hybrid Pixel Detector - Cross Section

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

27 September 2004Michael Campbell Medipix2 Cell Layout

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

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

27 September 2004Michael Campbell Bumps of readout side

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

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

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

27 September 2004Michael Campbell Measures various thresholds

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

27 September 2004Michael Campbell different thresholds

27 September 2004Michael Campbell Summary of measurements

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 pixels versus global threshold Spectroscopic information – insight into environment

27 September 2004Michael Campbell Image of a Swatch ( keV)

27 September 2004Michael Campbell Image of a Swatch ( keV)

27 September 2004Michael Campbell Image of a Swatch ( keV)

27 September 2004Michael Campbell Image of a Swatch ( keV)

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)

27 September 2004Michael Campbell Comparison ( keV)21.6 – 25.1 keV) ( keV) (21.6 – 25.1 keV)

27 September 2004Michael Campbell Comparison ( keV) keV) ( keV) ( keV)

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…..

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

27 September 2004Michael Campbell Acknowledgements  Fellow members of the Medipix Consortium  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