Sound and Light from Fractures in Scintillators

Abstract

Prompted by intriguing events observed in certain particle-physics searches for rare events, we study light and acoustic emission simultaneously in some inorganic scintillators subject to mechanical stress. We observe mechanoluminescence in ${\mathrm{Bi}}_{4}{\mathrm{Ge}}_{3}{\mathrm{O}}_{12}$, ${\mathrm{CdWO}}_{4}$, and ${\mathrm{ZnWO}}_{4}$, in various mechanical configurations at room temperature and ambient pressure. We analyze the temporal and amplitude correlations between the light emission and the acoustic emission during fracture. A novel application of the precise energy calibration of ${\mathrm{Bi}}_{4}{\mathrm{Ge}}_{3}{\mathrm{O}}_{12}$ provided by radioactive sources allows us to deduce that the fraction of elastic energy converted to light is at least $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$.