High purity mode operation of a gyrotron

I. Ogawa 1 , T. Idehara 2 , S.Maeda 1 , R. Pavlichenko 2 , S.Mitsudo 2 ,

D.Wagner 3 and M.Thumm 4

1 Faculty of Engineering, Fukui University,

Fukui 910-8507, Japan 2 Research Center for Development of Far-Infrared Region,

Fukui University, Fukui 910-8507, Japan

3 Institut für Plasmaforschung, Universität Stuttgart,

Pfaffenwaldring 31, D-70569 Stuttgart, Germany

4 Institut für Hochleistungsimpuls- und Mikrowellentechnik

P.O. Box 3640, D-76021 Karlsruhe, Germany

High frequency gyrotrons are characterized by their capacity to deliver high powers and their frequency step-tunability due to the alternation of the operating mode. Very often the gyrotron output needs to be converted into a Gaussian-like beam because the gyrotron generates radiation with TEmn mode structure. High output mode purity is necessary for an effective conversion. In order to improve mode purity, a nonlinear cavity which was designed using a scattering matrix code and exquisitely fabricated is installed in the Gyrotron FU VA.