AXEL: High-pressure Xe gas TPC for BG-free $0\nu2\beta$ decay search

TL;DR

AXEL is a high-pressure xenon gas TPC with a novel ELCC readout system, demonstrating promising energy resolution for neutrinoless double-beta decay search and developing advanced techniques for background reduction in future large-scale detectors.

Contribution

The paper introduces the AXEL detector with a unique ELCC readout system and reports its performance, including energy resolution and background reduction strategies for future large-scale experiments.

Findings

Energy resolution of 0.82-1.74% at Q-value

Successful demonstration of ELCC with prototype detector

Development of background reduction techniques for 1-ton scale

Abstract

AXEL is a high-pressure xenon gas time projection chamber for neutrinoless double-beta decay (0n2b) search. The AXEL has a unique readout system called ELCC which has a cellular structure and photosensors to detect electroluminescence light produced by ionization electrons. We demonstrated the performance of the ELCC with a small prototype detector (AXEL-HP10L). The obtained energy resolution corresponds to 0.82 -- 1.74% (FWHM) at the 0n2b Q-value. We are constructing a new prototype (AXEL-HP180L) in order to study the energy resolution at the Q-value of 0n2b with a new design of ELCC with unit structure, newly developed electronics board, field-shaping electrodes, and Cockcroft-Walton-type high voltage power supply. For a future 1-ton scale large AXEL detector, we are developing new background-reduction techniques; topology identification with machine learning, positive-ion detection, and active-shield options.