Millimeter-wave graphite antennas for diagnostics of plasmas in large fusion devices

The investigate plasmas in large reactor-type fusion devices, e.g., ITER, various microwave diagnostics such as reflectometry, interferometry, radiometry in the frequency range between 20 and 200 GHz, the at ordinary and extraordinary waves are being developed [1]. Their antennas and reflectors, facing the plasma, must retain their operating characteristics unchanged over a long period of service under exposure of plasma fluxes and different radiations of a thermonuclear plasma: fluxes of neutrons, gammas and electromagnetic radiation. These factors can bring about the deterioration of heat conductivity, the change in the material structure, a heating up to 1000 °C with the result that the mechanical and radiotechnical propertiesof antennas change. To avoid changes in antenna performance (radiation pattern (RP), wave polarization, absolute wave amplitude) and to preclude the ingress of heavy impurities into the plasma due to erosion of metal microwave components we have proposed to use carbon-graphite (CG) antennas, reflectors, waveguide sections as an alternative to metallic ones [2].We have investigated horn, spherical antennas, and also plane and shaped reflectors in the 20 to 105 GHz band. Since pyramidal horns are in most common use, their sizes were optimized in the basic parameters, i.e., antenna beam half-width, amplitude near the principal axis, level of signal depolarization

Carbon graphite reflector antennas for submm-wave diagnostics of plasmas in fusion facilities

The advancement of research in controlled fusion calls for continuous improvement in the methods of high-temperature plasma diagnostics. Among most modern techniques we should mention contactless methods of diagnostics in mm-wave, submm-wave and optical bands that provide a possibility of choosing the narrow electromagnetic wave spectrum needed for the purposes of experiment. SubMM-wave interferometry, polarimetry, scattering and also electron cyclotron radiation detection are successfully applied in all magnetic plasma confinement devices.The antenna material must be sufficiently resistant to heat, plasma and hard radiation flows which may cause degradation of not only physic-mechanical properties of antennas but plasma parameters, too, due to impurity ejection into the confinement volume. In view of this, we have considered a possibility of applying in any large fusion facility the reflector antennas manufactured of the same carbon-graphite materials (CGM) that are generally employed to protect the first wall, as an alternative to metallic antennas

RF heating below ion-cyclotron frequencies in uragan torsatrons

The experiments on Uragan-3M torsatron (stellarator) on Alfvén resonance heating are presented. Usage of the three-halfturn antenna provides plasma density increase and heating of the electron plasma component.Представлены результаты экспериментов на торсатроне (стеллараторе) Ураган-3М по альфвеновскому нагреву плазмы. Использование трехполувитковой антенны позволило повысить плотность плазмы и нагреть ее электронный компонент.Надано результати експериментів на торсатроні (стеллараторі) Ураган-3М з альфвенівського нагріву плазми. Використання трьохнапіввиткової антени дозволило підвисити густину плазми й нагріти її електронний компонент