Low background detector with enriched 116CdWO4 crystal scintillators to search for double beta decay of 116Cd

Abstract

A cadmium tungstate crystal boule enriched in ${}^{116}$Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two ${}^{116}$CdWO${}_4$ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third ${}^{116}$CdWO${}_4$ sample (326 g) was tested with the help of ultra-low background high purity germanium ${\hat{I}}^3$ detector. Monte Carlo simulations of double ${\hat{I}}^2$ processes in ${}^{116}$Cd were used to estimate the sensitivity of an experiment to search for double ${\hat{I}}^2$ decay of ${}^{116}$Cd.

24 pages, 13 figures, 3 tables, accepted for publication on Journal of Instrumentation