# Electron neutral collision frequency measurement with the hairpin resonator probe

## TL;DR

This paper introduces a method to measure electron neutral collision frequency in plasma using hairpin resonator probes, validated through experiments and simulations across various gases and pressures.

## Contribution

It presents a novel approach employing a two-wire transmission line model and a minimization technique for accurate collision frequency measurement in plasma.

## Key findings

- Good agreement with HPEM simulations.
- Effective measurement across different gases and pressures.
- Method improves accuracy of plasma diagnostics.

## Abstract

Electron neutral collision frequency is measured using both grounded and floating hairpin resonator probes in a 27 MHz parallel plate capacitively coupled plasma (CCP). Operating conditions are 0.1-2 Torr (13.3-267 Pa) in Ar, He, and Ar-He gas mixtures. The method treats the hairpin probe as a two wire transmission line immersed in a dielectric medium. A minimization method is applied during the pressure and sheath correction process by sweeping over assumed collision frequencies in order to obtain the measured collision frequency. Results are compared to hybrid plasma equipment module (HPEM) simulations and show good agreement.