94-GHZ 25-KW CW LOW-VOLTAGE HARMONIC GYROTRON

A low-voltage second-harmonic gyrotron intended as a compact lightweig ht source has been designed and evaluated with a particle-tracing code and the particle-in-cell code MAGIC. The two codes are shown to be in good agreement when applied to a conventional fundamental-frequency g yrotron and also to the novel second-harmonic gyrotron, The 25-kW cont inuous wave (CW) 94-GHz gyrotron with a predicted conversion efficienc y of 32% and device efficiency of 22.5% is driven by a 25-kV 4.5-A (nu (perpendicular to)/nu(z), = 1.5, Delta nu(z)/nu(z) = 7%) electron beam from a magnetron injection gun and employs a low loss TE021/TE031 com plex cavity for mode control. Although the 17-kG CW gyrotron will use a cryogen-free high-T-c superconducting magnet, a 94-GHz prototype wil l be tested at low duty with a conventional low-T-c superconducting ma gnet.