Understanding the Enhancement of Scintillation Light in Xenon-Doped Liquid Argon

TL;DR

This paper investigates how adding small amounts of xenon to liquid argon enhances scintillation light, revealing the role of absorption and energy transfer mechanisms, and introduces a model matching experimental observations.

Contribution

It presents a new model for light production in xenon-doped argon that accounts for absorption and re-emission, explaining the observed light yield enhancement.

Findings

Adding ~10 ppm xenon doubles the light yield compared to pure argon.

Absorption of argon excimer emission by atomic xenon significantly impacts light yield.

The proposed model accurately reproduces the time dependence of light emission in xenon-doped argon.

Abstract

Measuring the scintillation light in noble gases is an important detection technique in particle physics. Numerous rare event searches like neutrino beam experiments, neutrino-less double beta-decay, and dark matter searches use argon-based detectors. In liquid argon, the light yield can be enhanced by the addition of a small quantity of xenon, where $\sim 10 - 1000$ ppm are added. The general enhancement mechanism and its pathway via an energy transfer between argon and xenon excimers is well known, however the importance of absorption of argon excimer emission by atomic xenon has not been fully appreciated. This absorption significantly reduces the light yield in commercially available argon which contains trace amounts ($\rm \sim 0.1$ ppm) of xenon. The addition of a small xenon dopant of $\sim 10$ ppm recovers this lost light resulting in an increased light yield over un-doped argon of about a factor of two. In this paper we introduce a model for the light production in xenon doped argon, including absorption and re-emission, and compare it to the measured time dependence of light emission in xenon-doped argon.