Reflections in Gyrotrons with Radial Output: Consequences for the ITER Coaxial Gyrotron


O. Dumbrajs,1,2 G. S. Nusinovich,3 and B. Piosczyk1


1Forschungszentrum Karlsruhe, Institut für Hochleistungsimpuls-und Mikrowellentechnik,

Association Euratom – FZK, Hermann –von - Helmholtz-Platz 1, D-76344 Eggenstein - Leopoldshafen, Germany. E-mail:

2Department of Engineering Physics and Mathematics, Helsinki University of Technology, Association Euratom - Tekes, P.O.Box 2200, FIN-02015 HUT, Finland. E-mail:

3Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742-3511, USA. E-mail:




A theory describing the influence of reflections on operation of gyrotrons with radial output is presented. The theory is used for evaluating the effect of reflections on the operation of the 170 GHz ITER coaxial cavity gyrotron. It is shown that for optimally chosen external magnetic field value and electron beam radius, possible reflections do not change the final steady-state operation, which corresponds to generation of a 2.2 MW power.