Development of a dual-phase xenon time projection chamber prototype for the RELICS experiment

The RELICS (REactor neutrino LIquid xenon Coherent elastic Scattering) experiment aims to detect coherent elastic neutrino-nucleus scattering from reactor antineutrinos using a dual-phase xenon time projection chamber (TPC). To validate the detector concept and ensure technical reliability for the full-scale experiment, a dedicated prototype was designed, constructed, and operated. This work presents an overview of the design, construction, and operational performance of the prototype, with emphasis on its major subsystems, including the TPC, cryogenics and xenon purification systems, slow control, and data acquisition. During operation, the detector demonstrated the capability to achieve a sub-keV energy threshold required for the RELICS physics program, as reflected by a measured single electron gain of (34.30 ± 0.01 (stat.)) PE/e- and the successful detection of 0.27keV L-shell decay events from 37Ar. In addition, essential data analysis techniques and simulation frameworks were developed and validated, establishing the technical foundation for future RELICS operations. The successful construction and operation of this prototype confirm the feasibility of the core technologies and provide the experimental basis for the full-scale RELICS detector.