The NEXT collaboration is pleased to announce the start-up of HD-DEMO, a new prototype detector now entering its commissioning phase at the Donostia International Physics Center (DIPC). HD-DEMO moves beyond the architecture of its predecessors, introducing technological solutions aimed at improving performance and scalability for future detectors.
HD-DEMO is a vertically symmetric detector, with the cathode positioned at its center and two drift regions extending toward either end. The most significant design change is the replacement of the Energy Plane’s photomultiplier tubes (PMTs) with a barrel of wavelength-shifting optical fibers covering the detector’s inner walls. PMTs are a known source of radioactive background, so their elimination is a major step toward more radiopure detector designs. In addition, the fibers also do away with the mechanical complication of housing the PMTs in a separate volume from the high-pressure xenon, simplifying the overall detector design. The electroluminescence region retains the well-proven two-parallel-mesh configuration, while a SiPM sensor plane behind it enables high-resolution topological reconstruction of particle tracks.
The detector is currently being commissioned using alpha particles from environmental radon and a ²²Na source. A live event display is also available online. HD-DEMO marks a crucial milestone on the path to a next-generation, tonne-scale experiment, demonstrating the key technologies needed to push the sensitivity frontier in the search for neutrinoless double beta decay.