Competition of modes resonant with arbitrary cyclotron harmonics ina gyrotron with nonfixed axial structure of the high-frequencyfield

A general theory is developed for self-consistent calculations of mode competition in a gyrotron with nonfixed axial structure of the RF field for arbitrary cyclotron harmonics. The theory is applied to the gyrotron operating at the Kernforschungszentrum Karlsruhe with a frequency of 150 GHz. The formalism presented allows a self-consistent calculation of mode competition for the operating and parasitic modes at the cyclotron resonance at arbitrary harmonics. Specific calculations are carried out for the cases n₀=1, n₁ =2 and n₀=2, n₁=1. It is emphasized that the formalism considered applies only to the case in which the azimuthal orthogonality condition is satisfied: n₀m₁≠n₁ m₀. There are circumstances when this condition is not satisfied     

High efficiency, phase-locked operation of the harmonic-multiplyinginverted gyrotwystron oscillator

The inverted gyrotwystron (phigtron) is a millimeter wave frequency-doubling amplifier that has been demonstrated to produce over 300 kW peak power at twice the input frequency (centered at f_in =16.85 GHz and f_out=33.7 GHz) over a 0.5% bandwidth with a saturated gain of 30 dB and efficiency greater than 35%. The device has also been studied both theoretically and experimentally in a different operating regime where frequency-doubled, phase-locked oscillation is possible. A signal, injected via a fundamental gyro-traveling wave tube input section, modulated a 55 kV, 10 A electron beam. After transit through a drift section, the prebunched electron beam produced phase-locked, second harmonic oscillations in a TE₀₃ mode output cavity. RF output centered at either of two frequencies, 34.42 and 34.62 GHz, with a maximum output power of 180 kW, an efficiency of 32% and a locked signal gain of 35 dB was measured. A theoretical prediction of locking bandwidth, a design overview, and the experimental results are presented followed by a summary and discussion of the results     

Interaction of modes in gyrotrons with a high-frequency field whose longitudinal structure is variable

Institute of Applied Physics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 7, pp. 847–853, July, 1990.     

Theory of step-tunable gyrotrons operating at two cyclotronharmonics

The scaling of operating parameters and the tendencies in the efficiency of the step-tunable gyrotron operating in a set of modes in a cavity of a given length are considered. Results of calculations are reported for the design of a ~1-kW, step-tunable gyrotron oscillator operating from 150 to 600 GHz in steps of about 15 GHz. Detailed results are presented for the efficiency, power losses in the cavity, and the starting conditions. Designs of the electron gun electrodes and of an output mode transducer are also presented. Full modulation of the radiation via the modulating anode of a magnetron injection gun is considered. The gyrotron would be of use for plasma diagnostics and spectroscopy, including electron paramagnetic resonance spectroscopy (EPR)     

Nonlinear theory of gyrotwystrons with stagger-tuned cavities

A nonlinear theory is developed to study the effects of stagger tuning on the gain and the bandwidth of stagger-tuned gyrotwystrons operating in the large-signal regime. The assumption that prebunching cavities are short and therefore the electron bunching proceeds mainly in the drift regions allows us to use a simple point-gap model of the prebunching section to study this problem. Studies of gyrotwystrons with one- and two-prebunching stagger-tuned cavities have been carried out in the large-signal, saturation regime and show that two-cavity gyrotwystrons are preferred over one-cavity gyrotwystrons for significantly larger gain, bandwidth and gain-bandwidth product. The comparison of our results with a previous gyrotwystron design shows good agreement and validates our model     

On the need to allow for variability of RF-field longitudinal structure in calculation of gyrotron efficiency

In high-power gyrotrons with open resonators that have nearly minimal diffraction Q, the longitudinal structure of the RF field can be affected by the electron beam. The need to allow for this effect in determination of the efficiencies of gyrotrons with resonators of conventional shape is investigated. It is shown that over wide ranges of gyrotron-parameter values of greatest practical interest, this effect is fairly small and, therefore, efficiency can be determined assuming a fixed RF-field longitudinal structure.Institute of Applied Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 9, pp. 1020–1026, September, 1991.