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

[Jay Benesch]

https://arxiv.org/abs/2406.00659

H. Jia, T. Li, T. Wang, Y. Zhao, X. Zhang, H. Xu, Z. Liu, J. Liu, L. 
Lin, H. Xie, L. Feng, F. Wang, F. Zhu, J. Hao, S. Quan, K. Liu, S. Huang

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.

Comments:	6 pages, 5 figures
Subjects:	Accelerator Physics (physics.acc-ph)

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With a variation on this producing polarized electrons, the positron 
source could use an existing quarter CM to get the electrons up to 10 
MeV for injection into standard CMs.