Speaker
Description
Dual-phase liquid argon TPCs can reach sub-keV thresholds by counting single ionization electrons, as DarkSide-50 showed. These thresholds are still limited by argon's 15.8 eV ionization energy and by the large share of nuclear recoil energy that is lost as heat. We present an R&D program to lower them by doping LAr with xenon and with photo-sensitive dopants, both of which have lower ionization energies than argon. Xenon doping raises the ionization yield and makes energy that would otherwise be lost as heat detectable. Photo-sensitive dopants also convert scintillation light into ionization electrons, and because they are hydrogen-rich, they add ¹H as a light target that is kinematically well matched to low-mass dark matter. The effect of either kind of dopant on eV-scale nuclear recoils has never been measured. We describe LOADED, a dual-phase TPC, and a cryogenic system based on proven xenon-doping techniques. We also describe ways to stop electroluminescence from re-ionizing the dopant, and planned neutron calibrations. This technology could enable tonne-scale searches for light dark matter and reactor CEνNS.