Limits on the release of Rb isotopes from a zeolite based 83mKr calibration source for the XENON project

TL;DR

This study investigates the release limits of 83Rb from a zeolite-based 83mKr calibration source for the XENON dark matter experiment, ensuring minimal contamination risk with no detectable 83Rb release observed.

Contribution

It provides the first experimental upper limits on 83Rb release from zeolite-embedded sources used for noble gas calibration in low-background experiments.

Findings

No detectable 83Rb release was observed.

The upper limit on 83Rb activity release confirms suitability for XENON.

Constraints on release of 84Rb and 86Rb were established.

Abstract

The isomer 83mKr with its half-life of 1.83 h is an ideal calibration source for a liquid noble gas dark matter experiment like the XENON project. However, the risk of contamination of the detector with traces of the much longer lived mother isotop 83Rb (86.2 d half-life) has to be ruled out. In this work the release of 83Rb atoms from a 1.8 MBq 83Rb source embedded in zeolite beads has been investigated. To do so, a cryogenic trap has been connected to the source for about 10 days, after which it was removed and probed for the strongest 83Rb gamma-rays with an ultra-sensitive Germanium detector. No signal has been found. The corresponding upper limit on the released 83Rb activity means that the investigated type of source can be used in the XENON project and similar low-background experiments as 83mKr generator without a significant risk of contaminating the detector. The measurements also allow to set upper limits on the possible release of the isotopes 84Rb and 86Rb, traces of which were created alongside the production of 83Rb at the Rez cyclotron.