Prebunched high harmonic gyrotron-Magnicon

Summary form only given. The output power of a high-harmonic gyrotron, which dramatically reduces the gyrotron´s requisite magnetic field, has been significantly enhanced by prebunching the electron beam. Both the prebunched and the nonprebunched high-harmonic gyrotrons are based on the resonant interaction of a large-orbit axis-encircling electron beam with a high-order azimuthal TE_n-- mode. A pencil electron beam is accelerated to an energy of up to 0.5 MeV in a TE₁₁₁ cavity, becoming an axis-encircling helical beam. The resultant electron beam behaves like a rigid corkscrew rotating about the axis. A novel interaction has been successfully developed to exploit the bunched nature of the helical beam. If the frequency of the gyrotron cavity´s TE_n-- mode is equal to the nth harmonic of accelerator´s frequency, then all electrons on this helix will enter the cavity at the same phase, i.e., the helix and wave will rotate together. The experiment was performed at the third harmonic with a TE₃₁₂ mode at 27.7 GHz. The conversion power was 6.7 kW, which was an order of magnitude greater than that of the nonprebunched comparison experiment