Spectroscopic analysis of the argon scintillation with a wavelength sensitive particle detector

TL;DR

This study provides a detailed spectroscopic analysis of argon scintillation, revealing that the dominant early light emission occurs in the 160-325 nm range, challenging the assumption of monochromatic 128 nm emission, and suggests new particle detection methods.

Contribution

The paper presents the first detailed time-resolved spectroscopic measurements of argon scintillation across pressures and fields, highlighting the significance of the third continuum emission for particle detection.

Findings

Dominant early emission in 160-325 nm range, not at 128 nm.

Third continuum emission linked to highly charged argon ions.

Pressure and field effects on scintillation components characterized.

Abstract

We performed a time-resolved spectroscopic study of the VUV/UV argon scintillation as a function of pressure and electric field, by means of a wavelength sensitive detector operated with different radioactive sources. Our work conveys new evidence of distinctive features of the argon light which are in contrast with the general assumption that, for particle detection purposes, the scintillation can be considered to be largely monochromatic at 128 nm (second continuum). The wavelength and the time-resolved analysis of the photon emission reveal that the dominant component of the argon scintillation during first tens of ns is in the range [160, 325] nm. This light is consistent with the third continuum emission from highly charged argon ions/molecules. This component of the scintillation is field-independent up to 25 V/cm/bar and shows a very mild dependence with pressure in the range [1,16] bar. The dynamics of the second continuum emission is dominated by the excimer formation time, whose variation as a function of the pressure has been measured. Additionally, the time and pressure-dependent features of electron-ion recombination, in the second continuum band, have been measured. This study opens new paths toward a novel particle identification technique based on the spectral information of the noble-elements scintillation light.