A flexi electron gun consists of multiple electrodes and can be used to maintain uniform beam current over the life of a traveling-wave tube (TWT). The flexi electron gun consists of dispenser cathode, anode1, anode2 and anode3 in addition to a beam focusing electrode (BFE). In an optimized electron gun, anode1 potential plays an important role in increasing beam current within the same biased condition of electronic power conditioner (EPC) and can be used as a critical parameter to increase current with time when cathode performance (beam current) degrades with time. Geometry, position and bias of these electrodes with respect to cathode provide low perveance electron beam optics to the interaction structure of a TWT. The flexi gun has been modelled in EGUN, developed and integrated with TWT, and simulated results are compared with experiment. This paper presents a detailed investigation of the effect of anode1 on beam current and also presents the cause of large variation of simulated and measured beam currents through back simulation in EGUN.
2. Chong, C. K. and W. L. Menninger, "Latest advancements in high-power millimeter-wave helix TWTs ," IEEE Transactions on Plasma Science, Vol. 38, No. 6, 1227-1238, Jun. 2010, doi: 10.1109/TPS.2010.2041940.
3. Wilson, J. D., E. G. Wintucky, K. R. Vaden, D. A. Force, I. L. Krainsky, R. N. Simons, N. R. Robbins, W. L. Menninger, D. R. Dibb, and D. E. Lewis, "Advances in space traveling-wave tubes for NASA missions," Proceedings of IEEE, Vol. 95, No. 10, 1958-1967, Oct. 2007, doi: 10.1109/JPROC.2007.905062.
4. Rodney, J. and M. Vaughan, "Synthesis of the Pierce gun," IEEE Trans. on Electron Devices, Vol. 28, No. 1, 37-41, Jan. 1981, doi: 10.1109/TED.1981.20279.
5. Zhao, D., G. Liu, W. Gu, T. Ma, Q. Xue, and Z. Zhang, "Design of a large compression ratio electron gun and uniform field focusing system for Ka band extended interaction klystron," IEEE International Vacuum Electronics Conference, 418-419, Aug. 2019 , doi: 10.1109/IVELEC.2009.5193587.
6. Vorobyov, G. S., I. V. Barsuk, and A. A. Drozdenko, "Optimization of operating regimes of TWT three-electrode electron gun," 21st International Crimean Conference Microwave & Telecommunication Technology , 316-317, Nov. 2011.
7. Menninger, W. L., R. T. Benton, M. S. Choi, J. R. Feicht, U. R. Hallsten, H. C. Limburg, W. L. McGeary, and X. Zhai, "70% efficient Ku-band and C band TWTs for satellite downlinks," IEEE Trans. on Electron Devices, Vol. 52, No. 5, 673-678, May 2005, doi: 10.1109/TED.2005.845840.
8. Komm, D. S., R. T. Benton, H. C. Limburg, W. L. Menninger, and X. Zhai, "Advances in space TWT efficiencies," IEEE Trans. on Electron Devices, Vol. 48, No. 1, 174-176, Jan. 2001, doi: 10.1109/16.892186.
9. Thaler, Y., E. Bosch, and J. Puech, "220 W Ku band space TWT upgrade," IEEE International Vacuum Electronics Conference, 1-2, Jul. 2007, doi: 10.1109/IVELEC.2007.4283204.
10. Li, J. Y., Z. Yu, W. Shao, K. Zhang, Y. Gao, H. Yuan, J. Jiang, K. Huang, H. Wang, Q. Chen, and S. Yan, "High current density M-type cathodes for VEDs," The 5th International Vacuum Electron Sources Conference Proceedings, 147-148, Apr. 2005, doi: 10.1109/IVESC.2004.1414168.
11. Sharma, R. K., A. R. Choudhury, S. Arya, S. K. Ghosh, and V. Srivastava, "Design and experimental evaluation of dual-anode electron gun and PPM focusing of helix TWT," IEEE Trans. on Electron Devices, Vol. 62, 3419-3425, Oct. 2015, doi: 10.1109/TED.2015.2470118.
12. Xiang, D., X. Li, M. Huang, and J. Cui, "Measurement and analysis of dual anode electron gun for Ka-band space TWT," IEEE International Vacuum Electronics Conference, 1-2, Monterey, CA, Sep. 2016, doi: 10.1109/IVEC.2016.7561918.
13. Sawicki, M. R., "Analytical determination of the thermal/mechanical performance of traveling wave tube electron guns," International Electron Devices Meeting, 160-163, Aug. 2005, doi: 10.1109/IEDM.1978.189377.
14. Herrmannsfeldt, W. B., EGUN: An Electron Optics and Gun Design Program, SLAC, Stanford, CA, USA, 1988.