COHERENT: Use of Photodetectors for Neutrino detection in Liquid Argon

The COHERENT Collaboration first observed CEvNS (coherent elastic neutron-nucleus scattering) in 2017 with a 15 kg CsI(Na) detector with confirmation in a 24 kg liquid argon detector in 2021. Since that time, numerous detectors have been developed using a variety of nuclei with the goal of observing more CEvNS events for better sensitivity to beyond-standard-model physics. COH-Ar-750, a 610 kg (fiducial mass) liquid Argon nuclei detector, is currently under development. Calibrated 3-inch photomultiplier tubes with sufficiently low dark rate will allow for detection of scintillation within the argon chamber. Dark rates, single-photoelectron spectra, and gain values from tested PMTs have been measured and will be presented along with a description of the apparatus. We will also describe the design and calibration of a liquid cryogen level detector that weas used to monitor the liquid nitrogen levels in the test chamber.