Liu, Z.P. Deng, H.X. Jiang, Z.G. Li, X.D. Qian, H.J. Shu, G. JACoW Publishing Geneva, Switzerland 2673-7035 978-3-95450-224-0 10.18429/JACoW-FLS2023-TU4P05 English 80-82 electron vacuum gun cathode emittance Contribution to a conference proceedings 2024 2024-01 https://doi.org/10.18429/JACoW-FLS2023-TU4P05 http://jacow.org/fls2023/papers/tu4p05.pdf A high-average-current VHF electron gun operating in the CW mode is under construction at Shanghai Advanced Research Institute, which is the key component of a kW-power-order free electron laser facility. The average current and the frequency of this electron gun is 1-10 mA and 217 MHz, respectively. To validate the performance of this instrument, a test platform has been designed. The R&D of its vacuum and diagnostics are presented in this work.