Comparison of energy resolution spectra of CdTe TIMEPIX detector working in photon counting and time-over-threshold mode

• Published in: 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC) pp. 1 - 4
• Main Authors: Krapohl, D., Frojdh, C., Frojdh, E., Gimenez, E. N., Maneuski, D., O'Shea, V., Tartoni, N., Thungstrom, G., Wilhelm, H., Wraight, K.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.01.2013
• Subjects: Detectors; Diamonds; Energy measurement; Energy resolution; Light sources; Noise; Photonics
• ISSN: 1082-3654; 2577-0829
• DOI: 10.1109/NSSMIC.2013.6829825

Hybrid pixel detectors like the Medipix and TIMEPIX developed by the Medipix collaboration combined with high-z materials are of growing interest. In particular the TIMEPIX detector can be operated in photon counting mode and time-over-threshold mode (ToT) to obtain spectral information. Previous studies showed that 110 μm pixel sizes obtain a better energy resolution than 55 μm pixel sizes. Furthermore, threshold scans obtained a better spectral resolution than operation in ToT mode. In this work the influence of noise sources in different measurement approaches on the spectral response of a TIMEPIX chip bump-bonded to CdTe sensor are presented. Two 1mm thick CdTe sensors with pixel sizes of 55 μm and 110 μm, bump-bonded to a TIMEPIX readout chip, were evaluated at the Diamond Light Source synchrotron. A finely collimated, perpendicular pencil beam with x-ray energies of 25 keV and 79 keV was used to investigate single pixels. A small area of 10×10 pixels was investigated in ToT-mode and compared to a threshold scan of the same pixels on both detectors. The measurements are compared to an analytical SPICE/Python simulation that emulates photon counting and time-over-threshold mode.