Speaker
Description
ClearMind project aims to develop a fast detection module for TOF-PET.
We propose a position-sensitive detector consisting of a monolithic PbWO${_4}$ scintillating crystal on which is directly deposited a bialkali photoelectric layer. This detector optimizes the transmission of light photons to the photoelectric layer. Photons are generated by two processus : the Cherenkov effect and the scintillation.
To fully exploit the potential of this detector, we need to caracterize crystal properties such as the scintillation yield and the different time constants. According to the literature, the time dependence of the scintillating processus can be modelized by a multi-exponential decay function ; each of exponential component are related to a different luminescent center. The scintillation of PbWO${_4}$ presents two main scintillation time constants, a fast one about 2 ns and a slow one about 6-10 ns.
We studied the scintillation light yield and time constants as a function of the crystal temperature for four different PbWO${_4}$ crystals, provided by three different producer : CRYTUR (CMS doping), EPIC (undoped) and SICCAS (CMS doping, Y-doping).
All crystals show 4-fold increase in the scintillation light yield when cooled to -25°C. EPIC undoped crystal shows the highest yield. The time measured constants are similar to the different technologies and we observe that scintillation is slowing down when crystal is cooled. This trend is more marked on the slow time constant.
