Reduction of $^{222}$Rn-induced Backgrounds in a Hermetic Dual-Phase Xenon Time Projection Chamber

TL;DR

This paper demonstrates that a hermetic dual-phase xenon TPC can significantly reduce $^{222}$Rn backgrounds, crucial for next-generation dark matter detectors aiming for ultra-low background levels.

Contribution

The study introduces and tests a hermetic TPC design that mechanically separates the target volume from Rn-emitting surfaces, showing its effectiveness in background reduction.

Findings

Hermetic TPC successfully operated over several weeks.

Scaling results indicate effective Rn reduction at DARWIN scale.

Hermetic design achieves required background levels despite imperfect separation.

Abstract

The continuous emanation of $^{222}$Rn from detector surfaces causes the dominant background in current liquid xenon time projection chambers (TPCs) searching for dark matter. A significant reduction is required for the next generation of detectors which are aiming to reach the neutrino floor, such as DARWIN. $^{222}$Rn-induced back\-grounds can be reduced using a hermetic TPC, in which the sensitive target volume is mechanically separated from the rest of the detector containing the majority of Rn-emanating surfaces. We present a hermetic TPC that mainly follows the well-established design of leading xenon TPCs and has been operated successfully over a period of several weeks. By scaling up the results achieved to the DARWIN-scale, we show that the hermetic TPC concept can reduce the $^{222}$Rn concentration to the required level, even with imperfect separation of the volumes.