Infrared spectroscopy of surface charges in plasma-facing dielectrics

TL;DR

This paper introduces a method using infrared spectroscopy to measure surface charges at plasma-dielectric interfaces by analyzing signal attenuation, with a theoretical model linking charge to optical response.

Contribution

It presents a novel spectroscopic technique and a theoretical framework for quantifying surface charges in plasma-facing dielectrics.

Findings

Surface charge causes measurable attenuation in IR transmission.

The optical response can be modeled with a classical Drude term.

The method efficiently infers surface charge magnitude from spectral data.

Abstract

We propose to measure the surface charge accumulating at the interface between a plasma and a dielectric by infrared spectroscopy using the dielectric as a multi-internal reflection element. The surplus charge leads to an attenuation of the transmitted signal from which the magnitude of the charge can be inferred. Calculating the optical response perturbatively in first order from the Boltzmann equation for the electron-hole plasma inside the solid, we can show that in the parameter range of interest a classical Drude term results. Only the integrated surface charge enters, opening up thereby a very efficient analysis of measured data.