Diagnostics of hot electrons leaving the ECR plasma sustained by the high-power gyrotron

TL;DR

This study investigates the energy distribution of electrons in high-power ECR plasma sources, revealing a threshold-like regime with bursts of energetic electrons and potential kinetic instabilities, using a novel diagnostic approach.

Contribution

It introduces a new method to measure electron loss distributions in high-power ECR plasma sources, linking electron bursts to plasma instabilities.

Findings

Discovered threshold-like regimes with energetic electron bursts

Identified correlation between bremsstrahlung spectra and electron distributions

Observed potential development of kinetic instabilities

Abstract

Energy distribution of electrons in the plasma sustained by the electron-cyclotron resonance (ECR) discharge has a complicated shape as a function of various parameters that still remains unknown. Meanwhile, it is an important plasma characteristic. Some methods and approaches give the possibility to estimate or measure the properties of the distributions of the electrons lost from the plasma. One of them, similar to the ion mass spectrometry, was used in this work to obtain such distributions in the non-classical continuous ECR ion source with high (up to $ 50-100$ W/cm$ ^ 3 $) energy input for the first time along with bremsstrahlung spectra. For certain parameters, a threshold-like regime was discovered, which comprised of the bursts of energetic electrons, bremsstrahlung and, supposedly, the development of kinetic instabilities.