The scintillation of liquid argon

Abstract

A spectroscopic study of liquid argon from the vacuum ultraviolet at 110 nm to 1000 nm is presented. Excitation was performed using continuous and pulsed 12 keV electron beams. The emission is dominated by the analogue of the so called 2 nd excimer continuum. Various additional emission features were found. The time structure of the light emission has been measured for a set of well defined wavelength positions. The results help to interpret literature data in the context of liquid rare gas detectors in which the wavelength information is lost due to the use of wavelength shifters.

Attenuation of vacuum ultraviolet light in liquid argon

“…6 in comparison with the emission spectrum observed in [13]. All purification steps described in Sect.…”

“…Here we follow this way backwards to emphasize the most critical issues by describing them first. Already in the emission spectra of [13] it was found that it is difficult to remove other rare gases from argon, xenon in particular. Why krypton never played a role in our experiments cannot be answered by the authors, so far.…”

“…Measurements exposing a 1 mm thick Teflon sheet of 16 g weight for 1 h to 2 bar xenon led to an increase of 25 mg in weight, Fig. 10 The transmission of chemically purified but not distilled liquid argon (upper panel) is shown in comparison with the fluorescence spectrum of liquid argon (lower panel [13]). The two pronounced absorption dips at 126.5 and 141.0 nm are related to xenon impurities, as described in detail in [14].…”

Ion-beam excitation of liquid argon

“…[8,13,14]). Therefore, in the following we will use a nomenclature which is common for the gas phase to describe also the "gas kinetic" processes leading to light emission of LAr, being aware that this terminology might be partly inadequate for the liquid phase.…”

“…In addition, they can be cleaned chemically to a high level of purity, which is important in terms of background: radioactive impurities can be removed from the LRg efficiently, as well as even some of the long-lived radioisotopes of other rare gases like 85 Kr from xenon [5]. Also impurities like oxygen or water which alter the light yield [6] or light-emission time constants [6][7][8][9] can be removed.…”