V. I. Belousov

Multi-Frequency Gyrotron with BN Brewster Window

A multi-frequency gyrotron equipped with a circular Brewster window made on the base of high-temperature-brazed ceramic disc was tested. Efficient gyrotron operation at 11 modes (frequencies) in the range of 105 GHz -143 GHz was demonstrated. Gyrotron output power (0.8 MW/0.1 sec) was limited by the used power supply. The gyrotron scheme and the test results are used in the design of long-pulse gyrotron with a CVD diamond window.

Quasi-optical multiplexer based on reflecting diffraction grating

The article presents results of theoretical and experimental investigation of quasioptical multiplexer based on reflecting diffraction grating. Diffraction losses caused by reflection into mirror harmonic, and by angle divergence of wave beams are calculated. In an experimental multiplexer, wave beams with the frequencies 70 GHz and 79 GHz were mixed with power losses less than 1%.

Methods of Calculation and Parameter Control of the Eigenmodes of a Simple Two-Mirror Cavity

Methods of spectrum calculation and parameter control of open-cavity eigenmodes are presented. The potential of the proposed software and hardware is demonstrated on the basis of an orotron cavity model designed and examined for millimeter wavelengths. The numerical and experimental results are in good agreement. The developed methods and software can be used for designing open cavities in various frequency ranges.

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.

42-GHz/500-kW Electron Cyclotron Resonance Heating System on Tokamak SST-1

The 42-GHz electron cyclotron resonance heating (ECRH) system on SST-1 is used to carry out ECRH-assisted preionization, breakdown, start-up, and heating experiments at 0.75-T (second harmonic) and 1.5-T (fundamental harmonic) operation. The gyrotron delivers 500-kW power at 42-GHz frequency at -50-kV beam voltage, 20-A beam current, and 19-kV anode voltage. The gyrotron has been commissioned successfully on dummy load for full parameters (500 kW/500 ms). The transmission line consists of matching optic unit, circular corrugated waveguide, miter bend with bidirectional coupler, waveguide switches, polarizer, bellows, dc breaks, and an uptaper. Approximately 20-m-long transmission line is used to launch the power from gyrotron to tokamak, and the burn pattern at the exit of line near the tokamak ensures a good Gaussian beam. A composite launcher [consisting of four mirrors (two profiled and two plane), two gate valves, and two vacuum barrier windows] is used to connect two ECRH systems (42 and 82.6 GHz). The 82.6-GHz/200-kW ECRH system is also planned for SST-1 to carry out experiments at 3-T magnetic field. The 42-GHz ECRH system has been commissioned with tokamak SST-1, ECRH power has been launched in tokamak, and successful ECRH-assisted breakdown is achieved at second harmonic.

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.

Transmission line for 258 GHz gyrotron DNP spectroscopy

We report the design and test of the transmission line for DNP spectrometer with 258GHz gyrotron. The 16 meter line includes mode converter, HE11 waveguides, 5 mitre bends, variable attenuator, directional couplers, calorimeter and switch. Transmission is 70 ± 15% with 15Watt in the pure HE11 mode.

A five-channel quasi-optical multiplexer of 12- to 90-GHz frequency range

An effective five-channel quasi-optical multiplexer, which distributes microwave signals of the frequency range of 12–90 GHz on five frequency channels, Ku, K, Ka, U, and E (frequency ranges of standard single-mode waveguides), or combines these channels into a single wave stream, has been developed for the first time. A relatively homogeneous characteristic with a total loss level of about 1.5 dB is achieved in 90% of each range band. A detailed analysis of diffraction and ohmic losses in the frequency channels of the multiplexer has been carried out.