PMT Performance Studies for Neutrino Interactions for COHERENT

A coherent elastic neutrino-nucleus scattering (CEvNS) event occurs when momentum transfer is small compared to the inverse size of a nucleus, scattering coherently from the constituent nucleons. The COHERENT collaboration has observed this interaction, and continues to perform precise measurements in several detectors at the Oak Ridge Spallation Neutron Source. Understanding CEvNS events will help us learn more about supernovae, weak nuclear form factors and dark matter. We’re currently constructing COH-Ar-750, a 750 kg liquid argon scintillator detector. The detector will feature 122 R14374 3” PMTs. PMTs are essential to measure the signal from CEvNS events. We tested the gain, dark rate, and peak to valley ratio at room and liquid nitrogen temperatures to assure quality performance of the PMT in liquid argon over a wide dynamic range. Linearity was tested at different light levels with neutral density filters. This work exhibits that the PMT and amplifier chain resolves single photoelectrons, and we’re continuing linearity tests to verify performance for high light-output events. This will pave the way for the next generation of CEvNS studies with COH-Ar-750.