Plasma and Fusion Research

Volume 14, 2405052 (2019)

Regular Articles

Code Development for Calculating Electron Beams in the Cavities of the Future High-Power Gyrotrons
Tomoharu NUMAKURA, Tsuyoshi KARIYA, Ryutaro MINAMI, Maki OKADA, Toshitaka HOJO, Fumiya MOTOYOSHI and Tsuyoshi IMAI
Plasma Research Center, University of Tsukuba, Tsukuba 305-8577, Japan
(Received 16 September 2018 / Accepted 4 February 2019 / Published 19 March 2019)


This study develops a computational code for evaluating the operations of high-power gyrotrons with high-current electron beams. The analytical model describes the electromagnetic fields and electrons by the Maxwell equations and cold-fluid equations, respectively. Specifically, it estimates the output power of the gyrotron with electron-beam fluctuations, which occur under high beam currents. The effects of fluctuations of the intense electron flows in nonuniform magnetic fields are studied in a 1MW gyrotron for electron cyclotron resonance plasma heating and current drive in large devices, such as the tandem mirror plasma device GAMMA10/PDX and the Large Helical Device (LHD). The rate of fluctuation growth of the electron beam and the output power of the high-power gyrotron with a fluctuated beam are calculated. In gyrotrons with a higher operating frequency (e.g., 154 GHz), significant deterioration of the electron beam and gyrotron operation is expected at beam currents exceeding 120 A.


gyrotron, computational code, high current, beam fluctuation, output power

DOI: 10.1585/pfr.14.2405052


  • [1] G.S. Nusinovich, Introduction to the Physics of Gyrotrons (Johns Hopkins University Press, 2004).
  • [2] M.V. Kartikeyan et al., Gyrotrons (Springer, Berlin, 2003).
  • [3] T. Kariya et al., Nucl. Fusion 57, 066001 (2017).
  • [4] R. Schuldt and E. Borie, Int. J. Infrared Millim. Waves 16, 1675 (1995).
  • [5] O.I. Louksha et al., Tech. Phys. 58, 751 (2013).
  • [6] O. Dumbrajs and G.S. Nusinovich, Phys. Plasmas 20, 073105 (2013).
  • [7] R. Yan et al., Phys. Plasmas 15, 103102 (2008).
  • [8] T. Numakura et al., Trans. Fusion Sci. Technol. 63, 295 (2013).
  • [9] T. Numakura et al., AIP Conf. Proc. 1771, 030023 (2016).
  • [10] W.B. Herrmannsfeldt, SLAC-331-UC28, Stanford Linear Accelerator Center (1988).
  • [11] A.R. Choudhury et al., IEEE Trans. Electron Devices 62, 192 (2015).
  • [12] Y. Nakashima et al., Nucl. Fusion 57, 116033 (2017).
  • [13] T. Kariya et al., Int. J. Infrared Millim. Waves 32, 295 (2011).
  • [14] T. Imai et al., J. Plasma Fusion Res. 85, 378 (2017).