A Study of NaI(Tl) crystal encapsulation using organic scintillators for the dark matter search

Abstract

Scintillating NaI(Tl) crystals are used for various rare decay experiments, such as dark matter searches. However, the hygroscopicity of NaI(Tl) crystals makes the construction of crystal detectors in these experiments challenging. Therefore, the crystal requires a tight encapsulation to prevent from air contact. More importantly, in a low radioactivity measurement, identification of external radiations and surface contamination is crucial to characterize the origin of total crystal radioactivities. Studies for the NaI(Tl) crystal encapsulation with active organic scintillator vetoes have been performed to mitigate the above-mentioned issues simultaneously. A bare crystal is directly coupled with liquid and plastic scintillators to tag external radiations that penetrate from the outer part of the crystal. We report the pulse shape discrimination between organic scintillator and the crystal scintillator in a single detector setup and their long-term stability.