An ultrafast electron diffraction (UED) facility is located at Shanghai Jiao Tong University. The layout of the UED is divided into two modules. The accelerating module has one S-band photocathode RF gun, one C-band harmonic buncher, and one C-band deflector. The power-generating module has one S-band klystron and one C-band klystron. To meet the high-precision requirements, a MicroTCA.4-based low level radio frequency (LLRF) system is used to provide a stable RF field in the cavities. In this paper, we introduce the RF distributions, LLRF system, firmware and software of the feedback controller, and field stability of the RF gun; and present an analysis of the measurement results for UED.

超快电子衍射 (UED) 设施位于上海交通大学。UED的布局分为两个模块。加速模块有1个S波段光电阴极射频枪、1个C波段谐波聚束器和1个C波段偏转器。发电模块有一个S波段速调管和一个C波段速调管。为满足高精度要求，基于 MicroTCA.4 的低电平射频 (LLRF) 系统用于在腔体中提供稳定的射频场。在本文中，我们介绍了射频枪的射频分布、LLRF 系统、反馈控制器的固件和软件以及射频枪的场稳定性；并对 UED 的测量结果进行分析。