Ionization Yield of Low-Energy Nuclear Recoils in a Dual-Phase Argon Detector

Dual-phase argon detectors are the choice of several direct Dark Matter searches and have been proposed for detection of coherent neutrino-nucleus scattering (CNS). CNS is an as-yet undetected flavor-blind interaction predicted by the Standard Model. A small dual-phase argon detector, $\sim $250 g active mass, is being built at Lawrence Livermore National Laboratory to investigate the ionization yield of nuclear recoils in the energy range relevant to CNS detection, sub-10 keV. Two measurements are currently planned for this detector. The first will utilize elastic neutron scattering, taking advantage of the 80-keV resonance in $^{40}$Ar, to measure ionization yield at 8 keV. The second will employ nuclear resonance fluorescence on $^{40}$Ar, as a source of nuclear recoils, to map to ionization yield from 0.1-6 keV. Requirements of CNS observation are discussed along with detector commissioning and preparations for both planned measurements.