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arXiv · 1906.08074

Rapid thermal emittance and quantum efficiency mapping of a cesium telluride cathode in an rf photoinjector using multiple laser beamlets

Lianmin Zheng·Jiahang Shao·Eric E. Wisniewski·John G. Power·Yingchao Du·Wanming Liu·Charles E. Whiteford·Manoel Conde·Scott Doran·Chunguang Jing·Chuanxiang Tang
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Abstract

Thermal emittance and quantum efficiency (QE) are key figures of merit of photocathodes, and their uniformity is critical to high-performance photoinjectors. Several QE mapping technologies have been successfully developed; however, there is still a dearth of information on thermal emittance maps. This is because of the extremely time-consuming procedure to gather measurements by scanning a small beam across the cathode with fine steps. To simplify the mapping procedure, and to reduce the time required to take measurements, we propose a new method that requires only a single scan of the solenoid current to simultaneously obtain thermal emittance and QE distribution by using a pattern beam with multiple beamlets. In this paper, its feasibility has been confirmed by both beam dynamics simulation and theoretical analysis. The method has been successfully demonstrated in a proof-of-principle experiment using an L-band radiofrequency photoinjector with a cesium telluride cathode. In the experiment, seven beamlets were generated from a microlens array system and their corresponding thermal emittance and QE varied from 0.93 to 1.14 $\mu$m/mm and from 4.6 to 8.7%, respectively. We also discuss the limitations and future improvements of the method in this paper.

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Lianmin Zheng, Jiahang Shao, Eric E. Wisniewski, John G. Power, Yingchao Du, Wanming Liu, Charles E. Whiteford, Manoel Conde, Scott Doran, Chunguang Jing, Chuanxiang Tang. 2019-06-19. Rapid thermal emittance and quantum efficiency mapping of a cesium telluride cathode in an rf photoinjector using multiple laser beamlets. https://doi.org/10.1103/physrevaccelbeams.23.052801

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