Low Energy Phonon Bursts Created By Fast Neutron Damage

TL;DR

This study investigates whether fast neutron damage causes low energy phonon bursts in solid state detectors used for dark matter and neutrino searches, finding that neutron damage is not the main source of observed excess events.

Contribution

First measurement of phonon bursts caused by fast neutron damage in solid state detectors, comparing neutron-exposed and control detectors to assess their impact on low energy event excesses.

Findings

Neutron damage-induced phonon bursts are not the dominant source of excess events.

Differences in spectral shape and rate dependence suggest other origins for the excess.

Spectral rate scaled to neutron exposure shows minimal contribution from neutron damage.

Abstract

Solid state athermal phonon calorimeters used in the search for low mass dark matter or coherent neutrino-nucleus interactions have long observed a large excess of events below several hundred eV. The relaxation of damage created by the interaction of fast cosmic ray neutrons with the detector has been proposed as a source of these excess events. By comparing neutron exposed detectors to control detectors, we report the first measurement of phonon bursts caused by damage created by fast neutrons. Differences in the spectral shape, the rate dependence on thermal history, and the observed spectral rate scaled to the neutron exposure between irradiated and control detectors suggest that our observed LEE backgrounds are not dominated by neutron damage-induced phonon bursts.