An integrated Approach to Understanding Vacuum Arcs

TL;DR

This paper presents a comprehensive four-stage model of vacuum arcs, integrating experimental data and mechanisms to better understand arc initiation, evolution, and damage, which are critical for large-scale accelerator and fusion device design.

Contribution

It introduces a unified, experimentally supported four-stage model of vacuum arcs that incorporates all active mechanisms and explains relevant data across various conditions.

Findings

Surface damage caused by differential cooling leads to high field enhancements.

The model explains arc trigger, plasma formation, evolution, and surface damage phases.

Data from experiments and failure analysis support the model's phases.

Abstract

Although used in the design and costing of large projects such as linear colliders and tokamaks, the theory of vacuum arcs and gradient limits is not well understood. Almost 120 years after the isolation of vacuum arcs, the exact mechanisms of the arcs and the damage they produce still being debated. We describe our simple and general model of the vacuum arc that can incorporate all active mechanisms and aims to explain all relevant data. Our four stage model, is based on experiments done at 805 MHz with a variety of cavity geometries, magnetic fields, and experimental techniques as well as data from Atom Probe Tomography and failure analysis of microelectronics. The model considers the trigger, plasma formation, plasma evolution and surface damage phases of the arc. Our data clearly shows surface damage produced by differential cooling capable of producing local high field enhancements $\beta \sim 200$, and arcing in subsequent pulses. We update the model and discuss new features while also pointing out where new data would be useful in extending the model to a wider range of frequencies.