Impact of geometry on light collection efficiency of scintillation detectors for cryogenic rare event searches

TL;DR

This study uses simulations and measurements to optimize the geometry and surface treatment of scintillation detectors, enhancing light collection efficiency for cryogenic rare event searches such as dark matter and double beta decay experiments.

Contribution

The paper identifies the optimal scintillator shape and reflector configuration to maximize light collection efficiency, validated by both simulations and experimental measurements.

Findings

Triangular prism scintillators with truncated cone mirrors yield highest efficiency.

Simulation results closely match experimental measurements.

Optimized geometries improve detector performance in cryogenic conditions.

Abstract

Simulations of photon propagation in scintillation detectors were performed with the aim to find the optimal scintillator geometry, surface treatment, and shape of external reflector in order to achieve maximum light collection efficiency for detector configurations that avoid direct optical coupling, a situation that is commonly found in cryogenic scintillating bolometers in experimental searches for double beta decay and dark matter. To evaluate the light collection efficiency of various geometrical configurations we used the ZEMAX ray-tracing software. It was found that scintillators in the shape of a triangular prism with an external mirror shaped as truncated cone gives the highest light collection efficiency. The results of the simulations were confirmed by carrying out measurements of the light collection efficiencies of CaWO4 crystal scintillators. A comparison of simulated and measured values of light output shows good agreement