Temperature Dependence of CsI:Tl Scintillation Pulse Shapes from -183°C to +90°C Measured with a SiPM Readout

A custom designed cryostat was constructed to measure the response of a CsI:Tl scintillator in temperature range from -183°C up to +90°C. The light readout was realized using a SiPM developed by FBK in near ultraviolet high density (NUV-HD) technology. The crystal and the SiPM were installed on separated copper frames. The crystal was cooled down by liquid nitrogen, while the SiPM was kept at temperature close to room temperature. A separation of 1 mm was kept between the crystal and the photodetector to ensure thermal isolation. The temperature of the crystal could be varied by heaters on the scintillator frame and was continuously monitored using a coil shaped resistance thermometer. The CsI:Tl scintillation decay profiles were recorded in the entire temperature range provided by the cryostat.