Design of a 10 MW, 35 GHz phase-locked gyrotron oscillator driven by a pulseline accelerator

An experiment designed to address the issues involved in phase-locking a high-peak-power gyrotron device driven by a pulseline accelerator is described. The 10-MW, 35-GHz experimental design is based on a multicavity approach, using a solid 1-MeV, 100-A, 55-ns electron beam. A helix-gun approach is being used in which a cold, 100-A electron beam with a low initial value of transverse momentum is produced by beam aperturing in a plasma-induced field-emission diode immersed in a strong axial magnetic field. The aximuthal phase bunching of the beam, and thus the bandwidth for phase-locked operation, will be enhanced by means of a passive bunching cavity of identical design to the driven cavity. The slot and aperture Q values will each be approximately 400, requiring a full slot angle of 44° in the prebunching cavities. The prebunched beam will drive the slotted TE₁₂₁ output cavity with a Q of approx. 400, which is designed to self-oscillate with or without beam prebunching. The output cavity is designed to produce output powers in the range of 1-10 MW and to have a locking bandwidth of 0.1%.