Investigation on different materials after pulsed high field conditioning and low-energy H- irradiation

TL;DR

This study evaluates various materials' performance under pulsed high electric fields and low-energy hydrogen irradiation, focusing on their breakdown resistance and surface modifications relevant for RFQ applications at CERN.

Contribution

It provides experimental data on material robustness and metallurgical changes after high-voltage conditioning and irradiation, aiding material selection for high-field RF components.

Findings

Materials exhibit varying breakdown thresholds and surface modifications.

Metallurgical analysis reveals changes in microstructure post-irradiation.

Certain materials demonstrate superior robustness to high electric fields.

Abstract

During operation, the radio-frequency quadrupole (RFQ) of the LINAC4 at CERN is exposed to high electric fields, which can lead to vacuum breakdown. It is also subject to beam loss, which can cause surface modification, including blistering, which can result in reduced electric field holding and an increased breakdown rate. First, experiments to study the high-voltage conditioning process and electrical breakdown statistics have been conducted using pulsed high voltage DC systems in order to identify materials with high electric field handling capability and robustness to low-energy irradiation. In this paper, we discuss the results obtained for the different materials tested. To complement these, an investigation of their metallurgical properties using advanced microscopic techniques was done to observe and characterize the different materials and to compare results before and after irradiation and breakdown testing.