Anisotropic Response Measurements of ZnWO$_4$ Scintillators to Neutrons for Developing the Direction-Sensitive Dark Matter Detector

TL;DR

This study measures the anisotropic scintillation response of ZnWO$_4$ crystals to neutrons, demonstrating potential for direction-sensitive dark matter detection by analyzing directional light yield variations.

Contribution

It provides the first quantitative measurement of the anisotropic quenching factors in ZnWO$_4$ for neutron-induced recoils, advancing the development of direction-sensitive dark matter detectors.

Findings

Measured quenching factors of 0.235 and 0.199 for two perpendicular surfaces.

Confirmed 15.3% anisotropy in scintillation response.

Demonstrated directional dependence of light yields in ZnWO$_4$.

Abstract

The scintillation yields of ZnWO$_4$ crystals change depending on the incident direction of particles. This property can be used as a direction-sensitive dark matter detector. So, we investigated the ZnWO$_4$ light yields ratio of neutron-induced nuclear recoils to gamma-ray induced electron recoils(quenching factor). Two surfaces almost perpendicular to the crystal axis of ZnWO$_4$ were irradiated with a quasi-monochromatic neutron beam of 0.885MeV, and the quenching factors of both surfaces for the oxygen-nucleus recoil in the ZnWO$_4$ crystal were measured. The obtained quenching factors of the two surfaces were 0.235 $\pm$ 0.026 and 0.199 $\pm$ 0.020, respectively confirming 15.3$\%$ of anisotropy.