Influence of Annealing on the Optical and Scintillation Properties of CaWO$_4$ Single Crystals

Understand

We investigate the influence of oxygen annealing on the room temperature optical and scintillation properties of CaWO$_4$ single crystals that are being produced for direct Dark Matter search experiments.

• The applied annealing procedure reduces the absorption coefficient at the peak position of the scintillation spectrum ($\sim430$ nm) by a factor of $\sim6$ and leads to an even larger reduction of the scattering coefficient.
• Furthermore, the annealing has no significant influence on the \emph{intrinsic} light yield.
• An additional absorption occurring at $\sim400$ nm suggests the formation of O$^-$ hole centers.