Test apparatus to monitor time-domain signals from semiconductor-detector pixel arrays

Kyle Haston, H. Bradford Barber, Lars R. Furenlid, Esen Salçin, Vaibhav Bora

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Pixellated semiconductor detectors, such as CdZnTe, CdTe, or TlBr, are used for gamma-ray imaging in medicine and astronomy. Data analysis for these detectors typically estimates the position (x, y, z) and energy (E) of each interacting gamma ray from a set of detector signals {Si} corresponding to completed charge transport on the hit pixel and any of its neighbors that take part in charge sharing, plus the cathode. However, it is clear from an analysis of signal induction, that there are transient signal on all pixel electrodes during the charge transport and, when there is charge trapping, small negative residual signals on all electrodes. If we wish to optimally obtain the event parameters, we should take all these signals into account. We wish to estimate x,y,z and E from the set of all electrode signals, {Si(t)}, including time dependence, using maximum-likelihood techniques[1]. To do this, we need to determine the probability of the electrode signals, given the event parameters {x, y, z, E}, i.e. Pr( {Si(t)} | {x, y, z, E} ). Thus we need to map the detector response of all pixels, {Si(t)}, for a large number of events with known x,y,z and E.In this paper we demonstrate the existence of the transient signals and residual signals and determine their magnitudes. They are typically 50-100 times smaller than the hit-pixel signals. We then describe development of an apparatus to measure the response of a 16-pixel semiconductor detector and show some preliminary results. We also discuss techniques for measuring the event parameters for individual gamma-ray interactions, a requirement for determining Pr( {S i(t)} | {x, y, z, E}).

Original languageEnglish (US)
Title of host publicationMedical Applications of Radiation Detectors
StatePublished - 2011
EventMedical Applications of Radiation Detectors - San Diego, CA, United States
Duration: Aug 24 2011Aug 25 2011

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherMedical Applications of Radiation Detectors
Country/TerritoryUnited States
CitySan Diego, CA


  • CZT
  • CdTe
  • CdZnTe
  • Ramo's theorem
  • TlBr
  • electronic readout
  • induced signals
  • pixel detectors
  • semiconductor detector
  • test apparatus

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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