Study and experimentation of a high resolution gamma camera based on thick CsI(Tl) crystals

Abstract

In nuclear physics basic research and, particularly, in gamma ray spectroscopy, the use of an imaging detector can be extremely useful to reduce the Doppler Broadening effect, in experiments where the gamma-ray source moves at high/relativistic velocity. Thick scintillators (>1 cm) are required to improve the detection efficiency in combination with spatial and energy resolution, hence coating materials must be carefully chosen for a trade-off between spectroscopic and imaging performances. In this work, we propose the use of HICAM, a recently developed gamma camera based on an array of Silicon Drift Detectors, coupled to a 2 cm thick CsI(TI) scintillator. Different strategies were tested, using both polished and rough crystals, applying several materials on the surfaces and carefully studying the optical coupling with the photodetectors. In the best case, the camera has shown an average spatial resolution of 2.6 mm and energy resolution below 8% with a Cs-137 collimated source (662 keV). Statistical reconstruction methods are also employed to determine the position of interaction.