A Prototype High-Pressure Xenon Detector for NEXT

We describe the operation and ongoing development of a high-pressure xenon time projection chamber (TPC). This detector is designed to measure the energy of ionizing radiation with high precision and has achieved an energy resolution of near 1 percent FWHM for 662 keV gamma rays emitted from a ¹³⁷Cs source. It is being developed as a prototype for the experiment NEXT (Neutrino Experiment with a Xenon TPC), in which a larger TPC, NEXT-100, will be stationed in the Canfranc underground laboratory in Spain. The experiment will combine good energy resolution with silicon photomultiplier-based particle tracking to search for neutrinoless double beta decay with approximately 100 kg of xenon enriched to the isotope ¹³⁶Xe.