Measurement of the total neutron cross section on argon in the 20 to 70 keV energy range

TL;DR

This paper reports new measurements of the neutron total cross section on argon in the 20 to 70 keV range, resolving previous discrepancies and improving understanding for neutrino and dark matter experiments using liquid argon.

Contribution

The study provides the first precise measurements of the neutron cross section on argon in this energy range using a thick target, clarifying previous data inconsistencies.

Findings

Resolved discrepancies in neutron cross section data for argon.

Provided new cross section values for 20-70 keV neutrons.

Enhanced accuracy for neutron interaction modeling in liquid argon.

Abstract

The cross section for neutron interactions on argon is an important design and operational parameter for a number of neutrino, dark matter, and neutrinoless double beta decay experiments which use liquid argon as a detection or shielding medium. There is a discrepancy between the evaluated total cross section in the $20$ to $70~\rm$\,keV neutron kinetic energy region given in the ENDF database and a single measurement conducted by an experiment with a thin target (0.2 atoms/barn) optimized for higher cross sections. This gives rise to significant uncertainty in the interaction length of neutrons in liquid argon. This discrepancy is now resolved by new results presented here from the Argon Resonance Transport Interaction Experiment (ARTIE), a thick target experiment (3.3 atoms/barn) optimized for the small cross sections in this energy region.