Coupled-resonator gyrotrons with mode conversion

Design of a Second Harmonic Double-Beam Continuous Wave Gyrotron with Operating Frequency of 0.79 THz

“…Such choice provides the highest coupling of the generating beam with the operating mode and a zero energy transfer of this beam to the parasitic mode TE 62 . For the absorbing beam, the coupling to the operating mode is zero while the coupling coefficients to the co-and counter-rotating modes TE 14 are equal and big enough in order to ensure that the beam withdraws energy from the spurious modes and thus suppresses the competing modes without influencing the operating mode. The estimates derived from the adiabatic theory show that the most simple scheme with a cut at the outer emitter (see Table 1) and an inner emitter with a radius of 3.7 mm (from which the generating beam originates) is not feasible because in this case, the radius of the emitter of the absorbing beam is only 1.6 mm and is located extremely close to the emitter of the generating beam.…”

“…In the designed EOS, the electron trajectories are far enough from the cavity wall in order to avoid an intersection of the beam by the entrance cone of the cavity in the case of a small misalignment. For the chosen radii, the most dangerous modes are TE 14 and TE 62 at the fundamental cyclotron resonance.…”

Axisymmetric multistage cavity resonators

“…In the studies of coupled cavities with mode conversion, quasiantisymmetric modes were mainly considered [5]. These modes in gyrotrons have a comparatively narrow range of magnetic fields and accelerating voltages, in which the starting current is less than the starting current of the quasisymmetric mode.…”

“…High-efficiency gyrotrons with CCMC-type cavities were studied for comparatively low modes (kR ≈ 10, where k = 2π/λ is the wave number and R is the cavity radius) [5]. The efficiency of gyrotrons with echelette and CCMC cavities at high modes was fairly small [3,6,7].…”

“…1 The present paper is devoted to a theoretical study of gyrotrons with such multistage cavities. Earlier variants and particular types of such cavities are, on the one hand, coupled cavities with mode conversion (CCMC) [3,5] and, on the other hand, cavities of echelette type [6][7][8]. The profiles of these cavities * vlasov@hydro.appl.sci-nnov.ru 1 Of course, this notion can be extended to a more general class of similar electrodynamic structures.…”