Li Xinmeng, Sun Jitao, Yu Yong, Shao Jiahang, Yang Jiayue, Zhou Quan, Ding Hongli, Shi Lei, Tao Kai, Guo Chenglin, He Zhigang, Chen Zhichao, Chen Zhen, Peng Shaohua, Wang Hongfei, Zhang Guoqing, Zhang Baichao, Li Zongbin, Zhao Feng, Wei Wei, Huang Maomao, Wang Wei, Liu Ming, He Chaofeng, Hu Liangbing, Wang Yaqiong, Li Han, Yue Weiming, Wang Xilong, Wu Guorong, Dai Dongxu, Zhang Weiqing, Yang Xueming
University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
Institute of Advanced Light Source Facilities, Shenzhen, Shenzhen 518107, People's Republic of China.
J Synchrotron Radiat. 2025 Jul 1;32(Pt 4):838-848. doi: 10.1107/S160057752500311X. Epub 2025 May 13.
The continuous-wave free-electron laser (CW-FEL), based on superconducting radiofrequency (SRF) technology with an electron bunch repetition rate of up to MHz levels, is one of the most advanced light sources, providing exceptionally high average and peak-brightness FEL pulses. Among the new CW-FEL facilities worldwide, the recently proposed Dalian Advanced Light Source (DALS) occupies a unique position as an extreme ultraviolet (EUV) facility primarily designed for chemical physics research. Since the beam emittance requirement for DALS is not as stringent as that for X-ray CW-FEL facilities, a direct current (DC) gun is considered as the primary electron source, with a very high frequency (VHF) gun also planned. To demonstrate key technologies and characterize the electron beam performance, a superconducting CW injector testbed, named the Electron Source Test Facility (ESTF), has been designed and is currently under construction. The testbed is uniquely designed to accommodate both guns with minimal switching effort, where the rest of the beamline layout remains unchanged except for the swapped guns. The two-gun switching scheme for the testbed is shown to be a feasible and cost-effective approach. Furthermore, the injector performance with both guns has been evaluated through a start-to-end simulation based on the DALS configuration, including the production of electron beam in the ESTF injector, the following beam acceleration and compression in a superconducting linear accelerator, and finally the beam lasing performance in the undulator section. The evaluation confirms that the DC gun is a promising electron source for CW-FEL facilities, especially for EUV applications, even though all currently constructed CW facilities have employed the VHF gun. This paper provides a comprehensive description of the injector design and the corresponding performance evaluation.
基于超导射频（SRF）技术的连续波自由电子激光（CW-FEL），其电子束重复频率高达兆赫兹级别，是最先进的光源之一，可提供极高的平均和峰值亮度的自由电子激光脉冲。在全球新的连续波自由电子激光设施中，最近提出的大连光源（DALS）作为主要用于化学物理研究的极紫外（EUV）设施，占据着独特的地位。由于大连光源对束流发射度的要求不像X射线连续波自由电子激光设施那样严格，因此直流（DC）电子枪被视为主要电子源，同时也计划采用甚高频（VHF）电子枪。为了演示关键技术并表征电子束性能，设计了一个名为电子源测试设施（ESTF）的超导连续波注入器试验台，目前正在建设中。该试验台经过独特设计，能够以最小的切换工作量容纳两种电子枪，除了交换电子枪外，其余束线布局保持不变。试验台的双电子枪切换方案被证明是一种可行且具有成本效益的方法。此外，通过基于大连光源配置的从头到尾的模拟，对两种电子枪的注入器性能进行了评估，包括在ESTF注入器中产生电子束、随后在超导直线加速器中的束流加速和压缩，以及最后在波荡器段的束流激光性能。评估证实，直流电子枪是连续波自由电子激光设施，特别是极紫外应用的有前途的电子源，尽管目前所有已建成的连续波设施都采用了甚高频电子枪。本文对注入器设计和相应的性能评估进行了全面描述。
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