Coherent high-frequency axial oscillations in a partially magnetized direct current magnetron discharge

TL;DR

This paper reports the observation of coherent high-frequency axial oscillations in a neon plasma within a magnetron discharge, analyzing their characteristics and proposing a wave propagation model to explain their behavior.

Contribution

It introduces the first detailed analysis of high-frequency axial oscillations in a partially magnetized DC magnetron discharge and applies a lower-hybrid wave theory for modeling.

Findings

Coherent 60 MHz oscillations observed at low currents.

Emergence of 5-10 MHz fluctuations above a certain current threshold.

Oscillations suggest axial wave propagation and turbulence-driven inverse cascade.

Abstract

High frequency oscillations are observed in a neon plasma of a direct current magnetron discharge. At low discharge currents, we see highly coherent 60 MHz fluctuations. Above a distinct current threshold, secondary 5 - 10 MHz fluctuations emerge in addition to turbulent fluctuations in the 60 - 100 MHz range. The oscillations in the total discharge current suggest axial wave propagation. A lower-hybrid wave theory is invoked to model the high frequency oscillations. We attribute the low frequency modes to a turbulence-driven inverse cascade process, as suggested by recent simulations.