Design and performance of a 180 L high-pressure xenon gas TPC as a prototype for a large-scale neutrinoless double-beta decay search

A high-pressure xenon gas time projection chamber, with a unique cellular readout structure based on electroluminescence, has been developed for a large-scale neutrinoless double-beta decay search. In order to evaluate the detector performance and validate its design, a 180 L size prototype is being constructed and its commissioning with partial detector has been performed. The obtained energy resolution at 4.0 bar is 1.73 |$\pm$| 0.07% (FWHM) at 511 keV. The energy resolution at the |$^{136}$|Xe neutrinoless double-beta decay |$Q$|-value is estimated to be between 0.79 and 1.52% (FWHM) by extrapolation. Reconstructed event topologies show patterns peculiar to the track endpoint that can be used to distinguish |$0\nu\beta\beta$| signals from gamma-ray backgrounds.