Large-Scale, Precision Xenon Doping of Liquid Argon

Abstract

The detection of scintillation light from liquid argon is an experimental technique key to a number of current and future nuclear/particle physics experiments, such as neutrino physics, neutrinoless double beta decay and dark matter searches. Although the idea of adding small quantities of xenon (doping) to enhance the light yield has attracted considerable interest, this technique has never been demonstrated at the necessary scale. Here we report on xenon doping in a 100 l crogenic vessel. We observed an increase in light yield by a factor of 1.81±0.04 at a dopant concentration of 10 ppm, consistent with a Geant4 prediction of 1.83±0.02. We determine a lower limit on the attenuation length of 3 m at a concentration of 10 ppm.

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

“…The ratio of the T 0 at 10 ppm to 0 ppm (both with the PMT (RAN) triggers, one finds a factor of more than two increase in the light yield. From simulation (as has been previously reported for this data [6]), a factor of approximately two is found. The reason given for this increase in reference [6]) is the increase in the transparency of LAr to the 175 nm scintillation of xenon compared to the 128 nm scintillation of argon.…”

“…From simulation (as has been previously reported for this data [6]), a factor of approximately two is found. The reason given for this increase in reference [6]) is the increase in the transparency of LAr to the 175 nm scintillation of xenon compared to the 128 nm scintillation of argon. This increase in transparency itself has been attributed to the xenon presence in commercial argon [13].…”

“…The data used in this paper has been previously described [6]. Our apparatus is a 100L liquid argon cryostat viewed by one 3 Hamamatsu R11065 PMT with a TPB coated acrylic disk fixed to the front of the tube.…”

“…We inserted xenon corresponding to added concentrations of 0, 1, 2, 5, and 10 ppm with an uncertainty of 6%. The data was taken under two trigger conditions: a PMT trigger (referred to in [6] as a random trigger, RAN) and a cosmic ray muon trigger (MU) derived from coincidence between scintillator panels placed above and below the cryostat. All the data was taken with the RAN trigger except for the 10 ppm (amount of added xenon) data which was taken with both MU and RAN triggers.…”

“…Previous work has demonstrated that a small dopant concentration of ∼ 10 ppm is sufficient to transfer a large portion of the scintillation to the xenon emission wavelength and to increase the total light yield. [5], [6].…”