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arXiv · 2411.01754

Experimental demonstration of dark current mitigation by an over-inserted plug in a normal conducting VHF gun

X. -H. Wang·G. Shu·H. Qian·X. Li·Z. Liu·Z. Jiang·H. Meng·C. Xing·Q. Zhou·H. Deng
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Abstract

The room temperature continuous wave (CW) very-high-frequency (VHF) gun is one of the candidates for the electron gun of the high-repetition-rate free-electron lasers (FELs). The VHF gun operates with a cathode gradient of ~ 20 MV/m and an accelerating voltage of ~ 750 kV. The gun dark current emission leads to beam loss along the FEL machine, therefore is a critical parameter for the performance of the CW gun. In this paper, we presents a systematic study of the dark current reduction of the VHF gun, including cathode region optimizations, dark current tracking simulations and measurements. Over-inserted cathode plugs were tested in two VHF guns of different acceleration gap sizes, and both demonstrated significant dark current reduction ratios of more than two orders of magnitude.

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X. -H. Wang, G. Shu, H. Qian, X. Li, Z. Liu, Z. Jiang, H. Meng, C. Xing, Q. Zhou, H. Deng. 2024-11-04. Experimental demonstration of dark current mitigation by an over-inserted plug in a normal conducting VHF gun. https://arxiv.org/abs/2411.01754

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