V. I. Malygin

Mirror synthesis for gyrotron quasi-optical mode converters

A new approach for the design of a quasi-optical gyrotron mode converter is proposed. It is based on the synthesis of quasi-optical mirrors using diffraction (Helmholtz-Kirchhoff) integrals. First application of such a method we already described in [1, 2]. Now a more powerful technic is used to provide optimal distributions of the wave beam field. It is shown that by means of specially shaped mirrors parameters of the main converter are enhanced strongly. In this paper we review the search for the optimal scheme of the converter, present and compare results of calculations and measurements of the gyrotron wave beam.

Determination of the Mode Content in Spurious Microwave Radiation of the Gyrotron with a Straight Axisymmetric Output

The method for determination of the mode content of a spurious microwave radiation of the gyrotron with a straight circular axisymmetrical output is discussed. As demonstrated, in the test task accuracy of this method is several percents. The experimental results on the determination of the mode content at the output of the coaxial gyrotron, operating on the mode TE14.8are in a good agreement with the theoretical calculations.

Multifrequency gyrotron with high-efficiency synthesized waveguide converter

The results of numerical simulation and experimental investigation of a prototype of a megawatt multifrequency gyrotron for controlled thermonuclear fusion facilities are presented. In experiments, the gyrotron has operated at six frequencies in the range 105–152 GHz with small diffraction losses in the internal quasi-optical system and a high Gaussian mode content in the output beam.

Recent results of development in Russia of 170 GHz gyrotron for ITER

The industrial production prototype of the ITER gyrotron was tested at the new test stand in Kurchatov institute with power 1.02 MW in 240 second pulses, and 0.8MW in 800 second pulses. Simultaneously at IAP a short pulse gyrotron with an increased size cavity was tested at power 1.5–2 MW.

Development in Russia of high power gyrotrons for plasma fusion installations

Electron cyclotron systems of fusion installations are based on powerful millimeter wave sources - gyrotrons, which are capable to produce now microwave power up to 1 MW in very long (hundreds seconds) pulses. The paper presents the latest achievements in development at IAP/GYCOM of MW power level gyrotrons for fusion installations (compare to [G.G. Denisov et al., 2007]). Main development efforts were spent for development 170GHz/lMW/50%/CW gyrotron for ITER and multi-frequency gyrotrons.

New results in development of MW output power gyrotrons for fusion systems

Gyrotrons are widely used in electron-cyclotron-wave systems of fusion installations. Modern and future installations require microwave sources with power at least 1 MW. CVD diamond windows are implemented into the gyrotrons with frequencies 140 GHz and 170 GHz. The goal of these near-time tests is to demonstrate 0.8-1 MW power in microwave pulse of 10 seconds at least at two frequencies 105 GHz and 140 GHz, corresponding to pass bands of the single diamond disc.

MEASUREMENT OF NEAR-MEGAWATT MILLIMETER-WAVE BEAMS

To measure parameters of microwave beams produced by modern gyrotrons, a number of special devices have been developed: quasi-optical filters, bi- directional couplers, calorimetric loads, etc. The wave beam pattern is studied by measuring intensity distributions at several cross-sections, which is used to reconstruct the beam phase distribution and design proper matching mirrors.

Multi-frequency gyrotron for ASDEX Upgrade

Recent few years a multi-frequency gyrotron for modernization of ASDEX Upgrade ECRH system is under development in GYCOM/IAP by contract with IPP. Following contract specifications the gyrotron must produce 10-s pulses with 1MW output power at 140GHz and over 800-kW power at 3 additional frequencies within 105–140GHz frequency range. The gyrotron output window is to be transparent for radiation in the whole frequency range or at least in a vicinity of each operating point.

New test results of 170 GHz/1MW/50%/CW gyrotron for ITER

The development of 170 GHz/1 MW/ 50%/CW gyrotron for ITER has been in progress in Russia. Recent test results of the last gyrotron version are presented. Stable output power of 0.5-0.6 MW was obtained for 300-s pulse duration limited by capability of the main power supply of that time. For output power of 0.9-0.95 MW the maximal pulse duration of 102 s was mainly limited by instability of gyrotron protection system and imperfection of power transmission line. Total gyrotron efficiency was about 50%. Stray radiation near 5% of radiated power was measured. After testing facility improvement and gyrotron opening and reassembling gyrotron test will be continued.

Multi-frequency gyrotrons for plasma fusion installations

During last years several new gyrotrons were designed and tested at IAP/GYCOM. Main development efforts were spent for development 170GHz/1MW/50%/CW gyrotron for ITER and multi-frequency gyrotrons. The paper presents new results in development of gyrotrons capable to operate at several frequencies.