A Novel Radiation Detector Consisting of an HgI2 Photodetector Coupled to a Scintillator

HgI2 photodetectors have been used in conjunction with CsI(Tl) and BGO to detect the light pulses from gamma rays and alpha particles. The photocurrent response to light of a typical HgI2 photodetector is presented and discussed. The spectral response is appropriate for most important scintillators, which have their maximum emission between 400 and 560 nm. Energy spectra obtained with an HgI2 photodetector coupled to a CsI(Tl) scintillator crystal are presented for gamma rays from 137Cs, a 68Ga positron source, 241Am and 99mTc, as well as for the K x-rays from Pb. The photopeak energy resolution value for 511 keV annihilation gamma rays with the CsI(Tl)-HgI2 combination was about 10%. Spectra obtained with an HgI2 photodetector coupled to a BGO scintillator crystal are presented for the annihilation gamma rays from a 68Ga positron source (19% photopeak resolution) and the alpha particles from a 244Cm source. Estimates of the quantum efficiencies for an HgI2 photodetector coupled to CsI(Tl) and BGO scintillator crystals give values in excess of 70%. A brief discussion is given of the limits on energy resolution set by the electronic noise. Potential applications of this novel radiation detection device and the advantages over photomultiplier-based devices are discussed.