Neutral Bremsstrahlung in TPCs

TL;DR

This paper investigates neutral bremsstrahlung (NBrS) as a source of electroluminescence in noble gas-based TPCs, expanding understanding beyond traditional excimer-based emission and analyzing spectral and pressure-dependent properties.

Contribution

It extends the theoretical framework of NBrS in noble gases and mixtures, providing new experimental results and insights into spectral content and pressure scaling.

Findings

NBrS observed in argon and xenon mixtures.

Spectral content varies with pressure and mixture composition.

NBrS contributes significantly to electroluminescence in certain conditions.

Abstract

Traditionally, it has been assumed that electroluminescence (EL) in time projection chambers was purely an excimer-based emission. This idea changed when neutral bremsstrahlung (NBrS) was observed first in argon and subsequently in xenon a few years ago. In this work we explore further the framework used to explain these observations, presenting results for noble gas -based mixtures, as well as mixtures including small fractions of a molecular additive (`quencher'). Spectral content and yields are discussed in some cases of contemporary interest, together with their pressure-scalings.