Spatially uniform calibration of a liquid xenon detector at low energies using K83mr

Abstract

A difficult task with many particle detectors focusing on interactions below $\sim 100\text{keV}$ is to perform a calibration in the appropriate energy range that adequately probes all regions of the detector. Because detector response can vary greatly in various locations within the device, a spatially uniform calibration is important. We present a new method for calibration of liquid xenon (LXe) detectors, using the short-lived ${}^{83\text{m}}\text{K}\text{r}$ . This source has transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses uniformly in all regions of the detector. Even for low source activities, the existence of the two transitions provides a method of identifying the decays that is free of background. We find that at decreasing energies, the LXe light yield increases, while the amount of electric field quenching is diminished. Additionally, we show that if any long-lived radioactive backgrounds are introduced by this method, they will present less than $67\times {10}^{-6}\text{events}{\text{kg}}^{-1}{\text{day}}^{-1}{\text{keV}}^{-1}$ in the next generation of LXe dark matter direct detection searches.