Experimental Study of Diamond Like Carbon (DLC) Coated Electrodes for Pulsed High Gradient Electron Gun

TL;DR

This study evaluates DLC coated electrodes in a pulsed high-gradient electron gun, demonstrating high electric fields without breakdown and effective photo-emission, advancing electrode technology for free electron lasers.

Contribution

It presents experimental data on DLC coated electrodes showing their superior performance in high-gradient vacuum environments for electron gun applications.

Findings

Achieved electric fields over 250MV/m without breakdown.

Demonstrated photo-emission at gradients up to 150MV/m.

DLC coatings outperform other surface treatments in vacuum gap insulation.

Abstract

For the SwissFEL Free Electron Laser project at the Paul Scherrer Institute, a pulsed High Gradient (HG) electron gun was used to study low emittance electron sources. Different metals and surface treatments for the cathode and anode were studied for their HG suitability. Diamond Like Carbon (DLC) coatings are found to perform exceptionally well for vacuum gap insulation. A set of DLC coated electrodes with different coating parameters were tested for both vacuum breakdown and photo electron emission. Surface electric fields over 250MV/m (350 - 400kV, pulsed) were achieved without breakdown. From the same surface, it was possible to photo-emit an electron beam at gradients up to 150MV/m. The test setup and the experimental results are presented