Development of a large orbit gyrotron with a permanent magnet system

The development of a high harmonic gyrotron using a permanent magnet system is presented. On the basis of the design for a high harmonic gyrotron, using an encircling large-orbit electron beam and a permanent magnet system (large orbit gyrotron, LOG), a gyrotron tube has been constructed. The construction of a permanent magnet system has been also completed. The maximum field intensity is a little bit higher than 1 T. This work is being carried out as a collaboration with the Shin-etsu Kagaku Company, Institute of Applied Physics, Russian Academy of Science (IAP-RAS) and Institute of Electronics, and Bulgarian Academy of Science (IE-BAS). The gyrotron has already achieved 3rd, 4th and 5th harmonic operations with relatively high efficiency. Corresponding frequencies are 89 GHz, 113 GHz and 138 GHz, respectively. The output power at the 3rd harmonic operation was 2.5 kW and the efficiency 6.3%.