Cavity for 8 mm second-harmonic gyroklystron amplifier

This paper presents how to design cavities for 8 mm second-harmonic gyroklystron amplifier based on the theory of gyroklystron amplifier. A lot of factors, such as the radius, length of cavity, modes competing, beam-wave coupling coefficient and the character of coated medium which can restrain the unwanted modes are discussed. Two high frequency structures composed of five designed cavities are tested, one has obtained an output power of about 251 kW with an efficiency of 23.9%, a gain of 27.2 dB and the 3 dB bandwidth is over 0.4%. The other has obtained an output power of about 246 kW and the other parameters are to be tested.