Performance limits of a 55 Performance limits of a 55 m m pixel CdTe detector pixel CdTe detector G.Pellegrini, M. Lozano , R. Martinez, M. Ullan Centro Nacional de Microelectronica, Barcelona, 08193, Spain M. Chmeissani , M. Maiorino, G. Blanchot, J. Garcia C. Puigdengoles Institut de Física d'Altes Energies, UAB Campus, 08193 Bellaterra, Spain
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Performance limits of a 55 m pixel CdTe detector G.Pellegrini, M. Lozano, R. Martinez, M. Ullan Centro Nacional de Microelectronica, Barcelona, 08193,
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Performance limits of a 55Performance limits of a 55mm pixel CdTe detector pixel CdTe detector
G.Pellegrini, M. Lozano , R. Martinez, M. Ullan Centro Nacional de Microelectronica, Barcelona, 08193, Spain
M. Chmeissani , M. Maiorino, G. Blanchot, J. Garcia C. Puigdengoles
Institut de Física d'Altes Energies, UAB Campus, 08193 Bellaterra, Spain
2004 IEEE NSSGiulio Pellegrini
Objectives of the researchObjectives of the research
CdTe is one of the most widely studied material in the field of X-ray detection for energies above 10keV, due to its high absorption efficiency.
CdTe detectors for imaging applications are usually fabricated in thick substrates and with pixel size smaller than 100μm.
However, reducing the pixel size might lead to an increase in the charge shared among neighboring pixels due to the low mobility of the major carriers.
The operation of a pixel detector is strongly influenced by the ratio of the pixel size to the thickness of the detector.
We present charge sharing results from simulation and experimental data obtained with a specific purpose circuitry using Medipix-II with CdTe detectors.
Simulation results combining DESSIS and Geant4 Monte Carlo simulation.
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Experimetal results at V=-100V
Experimental result using an Americium source. The detector was biased at –100V.
Average relative charge sharing for the 3x3 matrix simulated and measured experimentally.
2004 IEEE NSSGiulio Pellegrini
ConclusionsConclusions
The data collected with the pixilated CdTe coupled to Medipix-II chip and the simulated results by DESSIS are in good agreement , thus one can use such a model to optimize the design of the pixilated CdTe detector for photon counting readout ASICS.
A 1mm thick CdTe with small pixel pitch will have poor performance when coupled to Photon Counting (PC) ASIC. Either it does not trigger, if the threshold is relatively too high, or many pixels count the same photon if the threshold is very low.