GraXe, graphene and xenon for neutrinoless double beta decay searches

TL;DR

GraXe is a novel neutrinoless double beta decay detector combining liquid xenon and graphene to achieve ultra-low background levels, leveraging existing materials and technologies for a feasible and highly sensitive experiment.

Contribution

This paper introduces the GraXe detector concept, integrating graphene with liquid xenon to enhance background suppression in neutrinoless double beta decay searches.

Findings

Conceptual design of GraXe detector with graphene-coated sphere

Potential for ultra-low background due to shielding and material purity

Utilization of existing enriched xenon and cryogenic technology

Abstract

We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in Xe-136. GraXe combines a popular detection medium in rare-event searches, liquid xenon, with a new, background-free material, graphene. In our baseline design of GraXe, a sphere made of graphene-coated titanium mesh and filled with liquid xenon (LXe) enriched in the Xe-136 isotope is immersed in a large volume of natural LXe instrumented with photodetectors. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large frequency range, and impermeable to the xenon. Event position could be deduced from the light pattern detected in the photosensors. External backgrounds would be shielded by the buffer of natural LXe, leaving the ultra-radiopure internal volume virtually free of background. Industrial graphene can be manufactured at a competitive cost to produce the sphere. Enriching xenon in the isotope Xe-136 is easy and relatively cheap, and there is already near one ton of enriched xenon available in the world (currently being used by the EXO, KamLAND-Zen and NEXT experiments). All the cryogenic know-how is readily available from the numerous experiments using liquid xenon. An experiment using the GraXe concept appears realistic and affordable in a short time scale, and its physics potential is enormous.