Characterization of the upgraded photoinjector at the Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility

Hanxun Xu; Shuai Ma; Wenhao Li; Lanbin Li; Weijun Wang; Dexin Xiao; Jianxin Wang; Yu Liu; Longgang Yan; Lijun Chen; Xuming Shen; Jie Liu; Zheng Zhou; Peng Li; Kui Zhou; Xinfan Yang; Dai Wu; Ming Li

doi:10.1063/5.0225417

Characterization of the upgraded photoinjector at the Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility

Rev Sci Instrum. 2025 Jan 1;96(1):013302. doi: 10.1063/5.0225417.

Authors

Hanxun Xu¹, Shuai Ma¹, Wenhao Li¹, Lanbin Li¹, Weijun Wang¹, Dexin Xiao¹, Jianxin Wang¹, Yu Liu¹, Longgang Yan¹, Lijun Chen¹, Xuming Shen¹, Jie Liu¹, Zheng Zhou¹, Peng Li¹, Kui Zhou¹, Xinfan Yang¹, Dai Wu¹, Ming Li¹

Affiliation

¹ National Key Laboratory of Science and Technology on Advanced Laser and High Power Microwave, Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China.

PMID: 39853172
DOI: 10.1063/5.0225417

Abstract

The Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility (CAEP THz FEL, CTFEL) has been operated as a user facility for over five years. To further meet the growing demands of modern science, an upgrade project for an infrared-terahertz free electron laser facility based on CTFEL has been proposed to broaden the frequency range from 0.1-4.2 to 0.1-125 THz. Recently we upgraded the CTFEL photoinjector in order to fulfill the beam injection requirements of the infrared-terahertz free electron laser facility. In this paper, we measured the beam parameters of the upgraded CTFEL photoinjector. A Michelson interferometer was constructed to measure the auto-correlation of the coherent transition radiation emitted by the electron bunch. Both the Kramers-Kronig reconstruction method and the time-domain fitting approach have been employed to estimate the bunch length, resulting in a root-mean-square bunch length of 0.30 ps. A normalized transverse emittance of 5.62 π mm mrad was determined by a quadrupole scan. The measured mean energy of the electron bunch is adjustable between 6 and 8 MeV with an energy spread of less than 0.5%. These measurements prove that the upgraded CTFEL photoinjector fulfills the injection requirements of the facility to be built.