High-power free-electron maser operated in a two-mode frequency-multiplying regime

Abstract

The frequency multiplication effects in high-power free-electron masers (FEM) with Bragg cavities were studied to provide the advance of the oscillators into short-wavelength bands. Theoretical analysis of frequency-multiplying FEMs was carried out within the framework of the averaged coupled-wave approach. Proof-of-principle experiments were performed based on a moderately relativistic induction linac LIU-3000 (JINR). As a result, an FEM multiplier operated with a megawatt power level in the 6-mm and 4-mm wavelength bands at the second and third harmonics, respectively, was realized. The possibility of using two-mode bichromatic FEMs for powering a double-frequency accelerating structure was discussed.

Second harmonic in FELs: Generation, amplification and suppression

“…In waveguide FEL schemes, differently from single pass FELs, which we consider, it is possible to excite transverse modes with a complex structure, and there is no actual division into even and odd harmonics. Relevant studies were done, for example, in [9][10][11][12]. Analytical description of the harmonic generation and evolution in a single pass FEL with account for angular effects was proposed in [5,6], developing first models in [13,14], where the angular effects were ignored.…”