Using 220Rn to calibrate liquid noble gas detectors

TL;DR

This paper introduces a 220Rn calibration source for liquid noble gas detectors, enabling low-energy vertex resolution evaluation without long-term radioactivity, demonstrated with a xenon test chamber.

Contribution

Development of a 220Rn calibration method that provides consecutive decay events for detector calibration without leaving long-lived radioisotopes.

Findings

Successful introduction of 220Rn atoms into a xenon chamber

Ability to evaluate vertex resolution at low energies

No long-term radioactive contamination left in the detector

Abstract

In this paper, we describe 220Rn calibration source that was developed for liquid noble gas detectors. The key advantage of this source is that it can provide 212Bi-212Po consecutive events, which enables us to evaluate the vertex resolution of a detector at low energy by comparing low-energy events of 212Bi and corresponding higher-energy alpha-rays from 212Po. Since 220Rn is a noble gas, a hot metal getter can be used when introduced using xenon as the carrier gas. In addition, no long-life radioactive isotopes are left behind in the detector after the calibration is complete; this has clear advantage over the use of 222Rn which leaves long- life radioactivity, i.e., 210Pb. Using a small liquid xenon test chamber, we developed a system to introduce 220Rn via the xenon carrier gas; we demonstrated the successful introduction of 6 times 10^2 220Rn atoms in our test environment.