Demonstration of sub-GV/m Accelerating Field in a Photoemission Electron Gun Powered by Nanosecond $X$-Band Radiofrequency Pulses

TL;DR

This paper demonstrates an RF photoemission electron gun achieving nearly 400 MV/m accelerating field using nanosecond X-band RF pulses, with stable operation and no significant breakdown, paving the way for brighter electron beams.

Contribution

First experimental demonstration of a high-gradient RF photoemission gun operating near 400 MV/m with stable, breakdown-free performance using nanosecond X-band RF pulses.

Findings

Achieved 400 MV/m accelerating field at the photocathode surface.

No major RF breakdown or significant dark current observed over three weeks.

Operated in RF transient mode with short 9 ns pulses.

Abstract

Radiofrequency (RF) electron guns operating at high accelerating gradients offer a pathway to producing bright electron bunches. Such beams are expected to revolutionize many areas of science: they could form the backbone of next-generation compact x-ray free-electron lasers or provide coherent ultrafast quantum electron probes. We report on the experimental demonstration of an RF photoemission electron source supporting an accelerating field close to 400~MV/m at the photocathode surface. The gun was operated in an RF transient mode driven by short $\sim 9$~ns X-band (\SI{11.7}{\giga\hertz}) RF pulses. We did not observe any major RF breakdown or significant dark current over a three-week experimental run at high accelerating fields. The demonstrated paradigm provides a viable path to forming relativistic electron beams with unprecedented brightness.