Measurement of the low-energy quenching factor in germanium using an $^{88}$Y/Be photoneutron source

TL;DR

This study measures the low-energy quenching factor in germanium using an $^{88}$Y/Be source, confirming the Lindhard model's applicability and providing precise quenching factor values for nuclear recoils between 0.3 and 8.5 keV.

Contribution

It provides the first detailed measurement of the germanium quenching factor at sub-keV energies using a photoneutron source and Monte Carlo simulations.

Findings

Best fit Lindhard parameter k=0.179±0.001

Quenching factor ranges from 13.7% to 25.3% for 0.3-8.5 keV recoils

Agreement with previous measurements and model validation

Abstract

We employ an $^{88}$Y/Be photoneutron source to derive the quenching factor for neutron-induced nuclear recoils in germanium, probing recoil energies from a few hundred eV$_{nr}$ to 8.5keV$_{nr}$. A comprehensive Monte Carlo simulation of our setup is compared to experimental data employing a Lindhard model with a free electronic energy loss $k$ and an adiabatic correction for sub-keV$_{nr}$ nuclear recoils. The best fit $k=0.179\pm 0.001$ obtained using a Monte Carlo Markov Chain (MCMC) ensemble sampler is in good agreement with previous measurements, confirming the adequacy of the Lindhard model to describe the stopping of few-keV ions in germanium crystals at a temperature of $\sim$77 K. This value of $k$ corresponds to a quenching factor of 13.7 % to 25.3 % for nuclear recoil energies between 0.3 keV$_{nr}$ and 8.5 keV$_{nr}$, respectively.