Speaker
Description
The Neutron Veto of the XENONnT experiment is a Gd-loaded water Cherenkov detector designed to tag radiogenic neutrons from detector materials, a primary source of nuclear recoil backgrounds in the WIMP search. It consists of a water volume surrounding the cryostat, enclosed by reflective ePTFE panels to enhance light collection and instrumented with 120 8-inch PMTs.
After the first science runs with demineralized water, the Neutron Veto was upgraded by loading the water with Gd at a mass concentration of 0.2%. Gd loading enhances neutron capture and yields a higher-energy capture signal, improving detection efficiency and shortening capture times.
The performance of the upgraded Neutron Veto during Science Run 2 is reported. The neutron tagging efficiency increased from about 50% to about 80% after Gd loading, leading to a reduction by about a factor of two of the radiogenic neutron-induced nuclear recoil background in the TPC. The upgraded system provides improved background rejection for current and future direct dark matter searches.
| Main Contribution topic | Direct detection |
|---|---|
| Secondary contribution topic | Instrumentation for Dark Matter |