Energy resolution and energy–light response of CsI(Tl) scintillators for charged particle detection

Abstract

This article describes the crystal selection and quality control utilized to develop and calibrate a high resolution array of CsI(Tl) scintillator crystals for the detection of energetic charged particles. Alpha sources are used to test the light output variation due to thallium doping gradients. Selection of crystals with better than 1% non-uniformity in light output is accomplished using this method.Tests with a 240 MeV alpha beam reveal that local light output variations within each of the tested CsI(Tl) crystals limit the resolution to about 0.5%. Charge and mass dependences in the energy -light output relationship are determined by calibrating with energetic projectile fragmentation beams.

Non-linearity effects on the light-output calibration of light charged particles in CsI(Tl) scintillator crystals

“…The absence of firm energy-light constraints in the energy regions of Z ≥ 2 affected by the crystal non-linearity makes it extremely difficult to perform a systematic correction of the resulting effects. This is a limitation, as also pointed out in [29], for the energy resolution of the crystal in applications involving the detection of high-energy particles. Experiments involving direct beams with different energies to directly strike the crystal at different depths, could help in performing a systematic study of non-uniformity effects experienced by heavier ions.…”

“…This formula is often used in the literature to calibrate the light response of hydrogen isotopes assuming negligible quenching effects [29]. However, the quantity S is usually not a constant since it contains a spatial dependence of the type one can express the spatial dependence of the scintillation efficiency with the following simplified equation…”

“…Figure 12 shows a zoom to the low energy region of Figure 11 Figure 11. It is important to stress that the linear hypothesis made in previous hydrogen light output calibrations performed with 4-cm HiRA crystals [29] (where the smaller dynamic range and the limited calibration points did not allow for a detailed study of non-linearity effects) resulted in an incorrect determination of the zero offsets. To demonstrate the validity of our approach for all crystals in the array, Figure 13 shows the same proton-recoil kinematic lines as described by Figure 4 but with data combined from the full cluster of 48 HiRA10 crystals, covering the angular range shown on Figure 1 Table 3 He ELoss Table 4 He WMU Exp 4 He ELoss Table 6 Region Constrained by WMU data large detection angles for the lower energy (panel a) is mainly because of the higher angular uncertainty of the HiRA10 pixels due to the larger beam spot on the target achieved for the 28 MeV/u beam during the NSCL experiment.…”

“…In the equation, a 0 is a gain factor, A represents the Z = 1 isotope mass number and a 1 , a 2 are empirical non-linearity parameters that satisfy the relation [29] (where the smaller dynamic range and the limited calibration points did not allow for a detailed study of non-linearity effects) resulted in an incorrect determination of the zero offsets. To demonstrate the validity of our approach for all crystals in the array, Figure 13 shows the same proton-recoil kinematic lines as described by Figure 4 large detection angles for the lower energy (panel a) is mainly because of the higher angular uncertainty of the HiRA10 pixels due to the larger beam spot on the target achieved for the 28 MeV/u beam during the NSCL experiment.…”

Mixed ZnSxSe1–x Crystals as a Possible Material for Alpha-Particle and X-ray Detectors

“…The luminescence kinetics in ZnSe(Te) crystals is "slow": up to a hundred microseconds. Scintillators based on CsI(Tl) and NaI(Tl) are hygroscopic and require the additional moisture protection [3]. The shortcoming of ZnS(Ag)-based crystals consists in that they badly transmit photons of visible light and can only be used as thin layers [4].…”