Temperature dependence of CsI(Tl) gamma-ray excited scintillation characteristics

Abstract

The gamma-ray excited, temperature dependent scintillation characteristics of CsI(Tl) are reported over the temperature range of-100 to +50°C. The modified Bollinger-Thomas and shaped square wave methods were used to measure the rise and decay times. Emission spectra were measured using a monochromator and corrected for monochromator and photocathode spectral efficiencies. The shaped square wave method was also used to determine the scintillation yield as was a current mode method. The thermoluminescence emissions of CsI(TI) were measured using the same current mode method. At room temperature, CsI(T1) was found to have two primary decay components with decay time constants of T1=679±10 ns (63.7%) and T z = 3.34±0.14 Ws (36.1%), and to have emission bands at about 400 and 560 rim. The T1 luminescent state was observed to be populated by an exponential process with a resulting rise time constant of 19 .6±1 .9 ns at room temperature. An ultra-fast decay component with a < 0.5 ns decay time was found to emit about 0.2% (about 100 photons/MeV) of the total scintillation light. Except for the ultra-fast decay time, the rise and decay time constants were observed to increase exponentially with inverse temperature. At-80°C T1 and TZ were determined to be 2.22±0.33 ws and 18.0±2.59 ws, respectively, while the 400 rim emission band was not observed below-50°C. At +50°C the decay constants were found to be 628 ns (70.5%) and 2.63 ws (29.3%) and both emission bands were present. The scintillation yield of CsI(TI) was observed to be only slightly temperature dependent between-30 and +50°C, peaking at about-30°C (about 6% above the room temperature yield) and monotonically decreasing above and below this temperature. Four different commercially available CsI(TI) crystals were used. Minimal variations in the measured scintillation characteristics were observed among these four crystals. Thermoluminescence emissions were observed to have peak yields at-90,-65,-40, +20, and possibly-55°C. The relative magnitudes and number of thermolummescence peaks were found to vary from crystal to crystal.

Non-proportionality in the scintillation response and the energy resolution obtainable with scintillation crystals

“…Schotanus, et al [53] report a yield of 4900 phe/MeV and an energy resolution of 7.3% employing an XP2020Q PMT and 6 ps shaping time. There have appeared several reports on the scintillation decay of CsI(Tl+) [52]. Schotanus et al report a fast component of about 600 ns and a slow component of 3.4 ps with intensity ratio fastlslow = 1.2.…”

“…CsZ(TZ+): CsI(Tl+) shows a broad emission band extending from 350 to 700 nm with a maximum near 560 nm [52]. Schotanus, et al [53] report a yield of 4900 phe/MeV and an energy resolution of 7.3% employing an XP2020Q PMT and 6 ps shaping time.…”

Temperature gain correction for CsI(Tl) detection systems based on digital pulse shape analysis

“…6 and known from the literature [3,13] the decay time of the MPS decreases as the temperature rises. Thus, in principle, the decay constants may serve as a pulse shape parameter.…”

“…[3,4]). The decay time and relative intensity of those components were measured to be also dependent on the ambient temperature when excited by γ-rays.…”

Optimal Optical Conditions and Positioning Scheme for an Ultrahigh-Resolution Silicon Drift Detector-Based Gamma Camera

“…10) Figure 2(b) shows the simulated photon collection curve of NaI and CsI as a function of time. For CsI, a shaping time of about 20 ms was required to fully collect photons compared with the shaping time of about 2 ms for NaI(Tl).…”