Development of a new rectangular NaI(Tl) scintillator and spectroscopy of low-energy charged particles

Standard NaI(Tl) scintillators have only one optical window and are housed in airtight protective enclosures to protect against hygroscopicity from moisture in the air. For these reasons, NaI(Tl) scintillators are unsuitable for the collection of scintillation photons or for the detection of low-energy (<1 MeV) charged particles. To overcome these disadvantages, a rectangular NaI(Tl) scintillator has been newly developed. In this paper, we estimate the photon response of this new scintillator. The energy resolution was DeltaE (Full Width at Half Maximum)=7.5+/-0.2% for 662 keV gamma rays from a (137)Cs standard source. The number of photoelectrons was 3,686 for the photoelectric peak. Good energy resolution and photon collection were therefore confirmed for this specialized form of NaI(Tl) scintillator. The ability of this scintillator to detect low-energy particles was confirmed by successful measurement of low-energy charged particles (250-700 keV region) from a (137)Cs thin film radioisotope source.