High Performance Operation of a Direct-Current and Superconducting Radio-Frequency Combined Photocathode Gun

/ Authors

H. Jia, T. Li, T. Wang, Y. Zhao, X. Zhang, H. Xu, Z. Liu, J. Liu, L. Lin, H. Xie

and 7 more authors

L. Feng, F. Wang, F. Zhu, J. Hao, S. Quan, K. Liu, S. Huang

/ Abstract

Superconducting radio-frequency (SRF) guns are promising candidates to deliver high brightness continuous-wave (CW) electron beams for new generations of coherent linac light sources, ultrafast electron diffractions, MeV pulsed beam applications, etc. To solve the compatibility problem of semiconductor photocathodes, a hybrid gun combining a direct-current gap and an SRF cavity has been developed. The gun, employing K2CsSb photocathodes driven by a green laser, has been brought into stable CW operation with a dark current below 100 pA, delivering electron beams at an energy gain of 2.4 MeV, an electron bunch charge of 100 pC, and a repetition rate of 1 MHz. A normalized beam emittance of 0.54 mm-mrad has been achieved at the bunch charge of 100 pC and peak current of about 6 A. CW operation at 81.25 MHz repetition rate has also been tested with the maximum average beam current reaching 3 mA.