Electron emission properties of two-phase argon and argon-nitrogen avalanche detectors

TL;DR

This study investigates electron emission in two-phase argon and argon-nitrogen avalanche detectors, revealing different emission components and their dependence on electric fields, with implications for detector efficiency and behavior.

Contribution

It provides new insights into the electron emission mechanisms and the effects of nitrogen doping in two-phase argon avalanche detectors.

Findings

Slow emission dominates in pure Ar at high fields.

Fast emission dominates in Ar+N2 at high fields.

Emission efficiency is similar in both pure Ar and Ar+N2.

Abstract

Electron emission properties of two-phase Ar avalanche detectors are studied. The detectors investigated comprised a liquid Ar or Ar+N2 layer followed by a multi-GEM multiplier operated in the saturated vapour at 84 K. Two components of the electron emission through the liquid-gas interface were observed: fast and slow. In Ar, the slow emission component dominated even at higher fields, reaching 2 kV/cm. In Ar+N2 on the contrary, the fast emission component dominated at higher fields, the slow component being disappeared. This is explained by the electron backscattering effect in the gas phase. The slow component decay time constant was inversely proportional to the electric field, which is compatible with thermionic emission model. The electron emission efficiencies in two-phase Ar and Ar+N2 were estimated to be close to each other.