N. A. Zavolsky

Numerical simulation of mode interaction in 170 GHz/1 MW gyrotrons for iter

The paper presents an advanced method for and results of calculating main parameters of CW 170 GHz/1 MW gyrotrons operating at the TE28.7 and TE31.8 modes for ITER. Parameters are optimized to achieve maximum efficiency of the gyrotron with an acceptable Ohmic load on the cavity. Numerical modeling of starting up a gyrotron with an optimized cavity and processes of mode interaction are discussed.

Energy spectra of electrons and depressed potential collector in gyrotrons

Energy distributions of electrons after their interaction with RF field in the gyrotron with the output power 1 MW and frequency 140 GHz are calculated. The energy spectra evolution is studied for the cases when velocity spread, pitch-factor, beam current and cyclotron frequency change. The efficiency of one- and two stage energy recovery systems are investigated.

Development of 260 GHZ second harmonic CW gyrotron with high stability of output parameters for dnp spectroscopy

Development of continuous-wave 258.6 GHz gyrotron with output power about 20 W with high stability of output parameters is presented. This paper includes results of calculation, design, technical requirements and experimental tests for main subsystems of gyrotron and auxiliaries. The gyrotron setup shall be a part of a complex experimental system for NDP spectroscopy.Results of elaboration of continuous-wave 258.6 GHz gyrotron with output power about 100 W with high stability of output parameters is presented. This paper includes results of calculation, design, experiments and technical requirements for main subsystems of gyrotron and auxiliaries. The gyrotron setup is a main part of a complex experimental system for NDP spectroscopy.

Experimental investigation of technological gyrotrons

Powerful gyrotrons for technological applications, including material processing, are presented. 30 GHz gyrotrons at the second cyclotron harmonic TE/sub 02/ mode with oil-cooled solenoid were tested. On CW regime with output power 10 kW obtained efficiency 42% and output power 30 kW with efficiency 35%. The highest for the second harmonic gyrotrons efficiency 50% with 13 kW output power level was observed after modification of the tube. Experimental dependencies of output power and gyrotron efficiency before and after modification magnetic field profile are given. Conditions of high efficiency operation taking into account space-charge effects, velocity spread, RF field and static magnetic field profiles are discussed. Results of quality testing of cathodes and dependencies of the gyrotron efficiency on cathode emission inhomogeneity are presented.

Technological gyrotrons with permanent magnet system

The fulfillment of the new project of creation of the industrial prototype of a technological gyrotron on permanent magnets are discussed. The permanent magnet system was designed, constructed and successfully tested for a gyrotron. A 30 GHz gyrotron (n=2) with rf-output power of 10 kW is under development with the TE/sub 12/ operating mode. An output power of 12 kW was obtained (efficiency 24%).

Numerical Study of Processes in the Cavity of the 170 GHz Gyrotron for ITER Operating at the TE25.10 Mode

The opportunity of use of a TE25.10 operating mode for CW 170 GHz/1 MW gyrotron for ITER is estimated. Parameters are optimized to achieve maximum efficiency of the gyrotron with an acceptable Ohmic load on the cavity. The influence of unwanted mode conversion at the output of the resonator, mode competition, electron beam potential depression, ion compensation of the space charge and beam energy recovery is investigated.

Smooth Wideband Frequency Tuning in Low-Voltage Gyrotron With Cathode-End Power Output

The possibility of a smooth electronic frequency tuning for medium-power gyrotrons operated at the fundamental cyclotron resonance has been demonstrated in the numerical simulations. The use of a low operating voltage allows a drastic increase in the gyrotron operation efficiency at the higher axial modes and, hence, in the bandwidth of continuous frequency tuning. A gyrotron cavity with power output in the direction of the cathode end can provide a smoother power versus frequency dependence in the gyro-backward wave oscillator regime than a cavity with the conventional output in the direction of the collector. Simulations for a 2-kV gyrotron with a frequency of about 264-GHz demonstrate 3-GHz full-width at half-maximum frequency tuning with a power level of 15 to 30 W, which are attractive parameters for spectroscopic applications.

10 MW, X- and Ka-band gyrotrons

Summary form only given, as follows. The results of the development of moderately relativistic X and Ka-band gyrotrons are presented. For the first time the high efficiency (about 50%) single-mode generation at the power level of about 5-10 MW was realized without recuperation at the beam energy of about 300 keV. The microwave pulse duration at the X-band gyrotron achieved 7 mcs, and at the Ka-band it was varied from 200 to 600 ns. Operation of the relativistic gyrotron was simulated by the method based on the stationary model with the selfconsistent, not-fixed structure of the field. It was found that additional optimization of the cavity profile and parameters of magnetron injection gun might increase relativistic gyrotron efficiency up to 50 %.

High-harmonic sectioned-cavity THz gyrotrons

A third-harmonic large-orbit THz gyrotron with a sectioned cavity, which combines a long electron-wave interaction region and a relatively low diffraction Q-factor, is described. A similar scheme can be used to realize a self-exciting two-wave gyrotron with frequency multiplication.

Investigation of subterahertz gyrotron for DNP NMR spectroscopy at IAP RAS

The present paper concerns the state of the art of the development and experimental investigations of subterahertz gyrotrons for spectroscopy applications at IAP RAS. The gyrotron with frequency of 258 GHz and power of 100 watts is successfully used for spectroscopy experiments and 80-time rising of sensitivity has been obtained. The fundamental harmonic gyrotron with an internal mode converter is under development now. The predicted efficiency is 20% at power about 100 W and frequency of 263 GHz. The same helium-free 10-T magnet and electron optics will be used for design of a second harmonic tube with operating frequency of 520 GHz.