Infrared scintillation yield in gaseous and liquid argon

TL;DR

This paper measures the first primary and secondary scintillation yields in gaseous and liquid argon within the near infrared and visible spectrum, using G-APDs and pulsed X-ray irradiation, with implications for rare-event physics experiments.

Contribution

It provides the first measurements of NIR and visible scintillation yields in gaseous and liquid argon for both primary and secondary scintillations, using novel detection methods.

Findings

Primary scintillation yield in gaseous Ar: 17000 photons/MeV in NIR

Primary scintillation yield in liquid Ar: 510 photons/MeV

Gaseous Ar electroluminescence amplification: 13 photons/electron/kV

Abstract

The study of primary and secondary scintillations in noble gases and liquids is of paramount importance to rare-event experiments using noble gas media. In the present work, the scintillation yield in gaseous and liquid Ar has for the first time been measured in the near infrared (NIR) and visible region, both for primary and secondary (proportional) scintillations, using Geiger-mode avalanche photodiodes (G-APDs) and pulsed X-ray irradiation. The primary scintillation yield of the fast component was measured to be 17000 photon/MeV in gaseous Ar in the NIR, in the range of 690-1000 nm, and 510 photon/MeV in liquid Ar, in the range of 400-1000 nm. Proportional NIR scintillations (electroluminescence) in gaseous Ar have been also observed; their amplification parameter at 163 K was measured to be 13 photons per drifting electron per kV. Possible applications of NIR scintillations in high energy physics experiments are discussed.