Investigation of Fractures as a Background in Rare-Event Searches

Abstract

Rare-event searches in particle physics put immense effort into precisely controlling their backgrounds. However, not always considered is the effect of fractoluminescence if the active material fractures. The effect of atmosphere on the fractoluminescence of the scintillator BGO (Bi4Ge3O12) has been studied by stressing samples in a double-cleavage drilled compression (DCDC) geometry to fracture. A system has been developed to fracture samples in a controllable atmosphere and analyze the light and acoustic emissions. By analyzing the fracture of BGO, it has been demonstrated that the force required and the energy dissipated in fracture are increased as the water vapour in the atmosphere is reduced. It has also been demonstrated that the quantity of emitted photons increases in nitrogen rich atmospheres. These results demonstrate the importance of controlling both the atmosphere and stresses inside particle detectors. In addition, in order to study the effect of cryogenic temperature on fractures in particle detectors, a microfabricated polysilicon fracture apparatus has been designed and subjected to first tests.