[2] [2] CAI Jun,FENG Jinjun,WU Xianping,et al. Analysis and test preparation of attenuator for W-band folded waveguide TWT[C]// 2007 IEEE International Vacuum Electronics Conference. Kitakyushu, Japan: IEEE, 2007: 1-2. doi: 10.1109/IVELEC. 2007. 4283213.

[6] [6] DING Minghui,LIU Yanqing,LU Xinru,et al. Boron doped diamond films: a microwave attenuation material with high thermal conductivity[J]. Applied Physics Letters, 2019,114(16):162901. doi:10.1063/1.5083079.

[7] [7] HUA Chenyi,ZHANG Xiaoqing,CAI Jun,et al. The new application of Boron-doped diamond film: attenuator for high frequency and high power vacuum electronic devices[J]. Diamond and Related Materials, 2022(124):108944. doi:10.1016/j.diamond.2022. 108944.

[10] [10] POLYAKOV V I, RUKOVISHNIKOV A I, GARIN B M, et al. Electrically active defects, conductivity, and millimeter wave dielectric loss in CVD diamonds[J]. Diamond and Related Materials, 2005, 14(3/7): 604-607. doi: 10.1016/j. diamond. 2004. 10.001.

[11] [11] LI Y F,SU J J,LIU Y Q,et al. Design of a new TM021 mode cavity type MPCVD reactor for diamond film deposition[J]. Diamond and Related Materials, 2014(44):88-94. doi:10.1016/j.diamond.2014.02.010.

[12] [12] LIU Y K, TSO P L, LIN I N, et al. Comparative study of nucleation processes for the growth of nanocrystalline diamond[J]. Diamond and Related Materials, 2006,15(2/3):234-238. doi:10.1016/j.diamond.2005.06.020.

[13] [13] SEO J H, WU H, MIKAEL S, et al. Thermal diffusion Boron doping of single-crystal natural diamond[J]. Journal of Applied Physics, 2016,119(20):205703. doi:10.1063/1.4949327.

[15] [15] CALAME J P, ABE D K. Application of advanced materials technologies to vacuum electronic devices[J]. Proceedings of the IEEE, 1999,87(5):840-864. doi:10.1109/5.757257.