Light yield non-proportionality of inorganic crystals and its effect on cosmic-ray measurements

Abstract

The multi-TeV energy region of the cosmic-ray spectra has been recently explored by direct detection experiments that used calorimetric techniques to measure the energy of the cosmic particles. Interesting spectral features have been observed in both all-electron and nuclei spectra. However, the interpretation of the results is compromised by the disagreements between the data obtained from the various experiments, that are not reconcilable with the quoted experimental uncertainties. Understanding the reason for the discrepancy among the measurements is of fundamental importance in view of the forthcoming high-energy cosmic-ray experiments planned for space, as well as for the correct interpretation of the available results. The purpose of this work is to investigate the possibility that a systematic effect may derive from the non-proportionality of the light response of inorganic crystals, typically used in high-energy calorimetry due to their excellent energy-resolution performance. The main reason for the non-proportionality of the crystals is that scintillation light yield depends on ionisation density. Experimental data obtained with ion beams were used to characterize the light response of various scintillator materials. The obtained luminous efficiencies were used as input of a Monte Carlo simulation to perform a comparative study of the effect of the light-yield non-proportionality on the detection of high-energy electromagnetic and hadronic showers. The result of this study indicates that, if the calorimeter response is calibrated by using the energy deposit of minimum ionizing particles, the measured shower energy might be affected by a significant systematic shift, at the level of few percent, whose sign and magnitude depend specifically on the type of scintillator material used.

High‐resolution three‐dimensional dosimetry in clinically relevant volumes utilizing optically stimulated luminescence

“…At high ionization densities, that is, high linear energy transfer (LET), the luminescent response of scintillators is known to experience quenching, which is the underlying cause of non‐proportionality effects in scintillators 33 . In the case of organic scintillators, this quenching behavior can be modeled by the empirical Birks' law, stating that $$$$\begin{equation} \frac{\mathrm{d}L}{\mathrm{d}x} \propto \frac{\frac{\mathrm{d}E}{\mathrm{d}x}}{1+B\frac{\mathrm{d}E}{\mathrm{d}x}}\ , \end{equation}$$$$where $$\frac{\mathrm{d}L}{\mathrm{d}x}$$ is the differential light yield, $$\frac{\mathrm{d}E}{\mathrm{d}x}$$ is the ionization density (deposited energy per step length from simulations), and $$B$$ is the Birks coefficient.…”

“…At high ionization densities, that is, high linear energy transfer (LET), the luminescent response of scintillators is known to experience quenching, which is the underlying cause of non-proportionality effects in scintillators. 33 In the case of organic scintillators, this quenching behavior can be modeled by the empirical Birks' law, stating that…”

“…where dL dx is the differential light yield, dE dx is the ionization density (deposited energy per step length from simulations), and B is the Birks coefficient. This model may be expanded to include inorganic scintillators by adding an Onsager mechanism, 33 that models light responses from low-LET regions and successfully describe the supralinear behavior exhibited in self -activated materials. However, in the case of YSO:Ce, the quenching behavior has been shown to resemble that of organic scintillators up to LET values of 100 MeV/cm.…”

Diffuse Emission of Galactic High-energy Neutrinos from a Global Fit of Cosmic Rays

“…The measurements of the hadronic intensities are however not necessarily consistent between different experiments. The most commonly cited reason for this is uncertainties in the (relative) energy scale calibrations of different experiments, in particular for indirect observations such as those by IceTop and KASCADE, but also for calorimetric experiments such as DAMPE (Adriani et al 2022a). We here follow Dembinski et al (2017) in introducing one nuisance parameter α k per experiment k in order to rescale the experimental intensities.…”

The High Energy cosmic-Radiation Detection HERD facility: a future space instrument for cosmic-ray detection and gamma-ray astronomy

“…As summarized in Tab.1, the HERD experiment is designed to reach 𝐺 𝑒 𝑓 𝑓 higher than 2 𝑚 2 𝑠𝑟 for e − + e + and 1 𝑚 2 𝑠𝑟 for p and nuclei, and 𝜎 𝐸 /𝐸 better than 2% for e − + e + and 30% for p and nuclei. This is possible thanks to an innovative geometry based on a homogeneous, isotropic and finely-segmented 3D calorimeter, as demonstrated by the Calocube collaboration [10][11][12][13][14][15][16][17][18]. As shown in Fig.…”