Scintillation and optical properties of xenon-doped liquid argon

TL;DR

This study investigates how adding xenon to liquid argon improves its scintillation and optical properties, demonstrating significant enhancements in light yield, lifetime, and attenuation length for particle detection applications.

Contribution

It provides a comprehensive characterization of xenon-doped liquid argon, including precise measurements of key optical parameters across various xenon concentrations.

Findings

Doubling of photoelectron yield at highest xenon concentration

Tenfold reduction in triplet lifetime to ~90 ns

Tenfold increase in attenuation length over 6 meters

Abstract

Liquid argon (LAr) is a common choice as detection medium in particle physics and rare-event searches. Challenges of LAr scintillation light detection include its short emission wavelength, long scintillation time and short attenuation length. The addition of small amounts of xenon to LAr is known to improve the scintillation and optical properties. We present a characterization campaign on xenon-doped liquid argon (XeDLAr) with target xenon concentrations ranging from 0 to 300 ppm by mass encompassing the measurement of the photoelectron yield $Y$ , effective triplet lifetime $\tau_3$ and effective attenuation length $\lambda_\mathrm{att}$. The measurements were conducted in the Subterranean Cryogenic ARgon Facility, SCARF, a 1 t (XeD)LAr test stand in the shallow underground laboratory (UGL) of TU-Munich. These three scintillation and optical parameters were observed simultaneously with a single setup, the Legend Liquid Argon Monitoring Apparatus, LLAMA. The actual xenon concentrations in the liquid and gaseous phases were determined with the Impurity DEtector For Investigation of Xenon, IDEFIX, a mass spectrometer setup, and successful doping was confirmed. At the highest dopant concentration we find a doubling of $Y$ , a tenfold reduction of $\tau_3$ to $\sim$ 90 ns and a tenfold increase of $\lambda_{att}$ to over 6 m.