DETECTOR OPTIMIZATION FOR HAND-HELD CSI(TL) HGI2 GAMMA-RAY SCINTILLATION SPECTROMETER APPLICATIONS/

Gamma-ray spectrometers using mercuric iodide (HgI2) photodetectors (P Ds) coupled with CsI(T1) scintillators have shown excellent energy res olutions and high detection efficiency at room temperature [1-5]. Addi tionally HgI2 semiconductor PDs allow for extreme miniaturization of t he detector packaging compared with photomultiplier tube (PMT) based d etectors. These advantages make possible the construction of a new gen eration of hand-held gamma-ray spectrometers. Studies of detector opti mization for this application have been undertaken. Several contact ma terials including hydrogel and semi-transparent metal films have been evaluated and compared for their performances and long term stability. In order to provide higher gamma-ray detection efficiency (i.e., larg er scintillator volume), but without causing significant degradation o f the excellent response achieved with the matched scintillator/PD int erface, the scintillator/PD configuration has been studied A Monte Car lo simulation model has been developed so that the spectral shape can be predicted for various scintillator shapes and surface treatments.