Serviceability of using the carbon–graphite materials for inner elements of microwave diagnostic for large fusion devices

Abstract

As an alternative to metal-made inner elements of MM and subMM diagnostics (antennae, reflectors, waveguides) we propose the elements fabricated of carbon–graphite materials (CGM). A comparative study of antennae and reflectors made of CGM and metal for 30–150 GHz in MM and for subMM ranges was carried out under the influence of pulsed plasma streams and heating up to 1000 °C. The effect of neutron irradiation on reflectivity at 337 μm was studied as well. The obtained data demonstrated that CGM can be used as material for fabricating the above mentioned inner diagnostic components in those large-scale fusion devices where similar materials are in use for the first wall protection. The Fabry–Perot type resonator with spherical CGM-made mirrors showed rather good characteristics, and can be used for measuring plasma properties in a divertor flow.

Graphite as a structural material for the in-vessel components for plasma diagnostics in the millimeter and sub-millimeter ranges

“…To study the properties of CGM-made resonators, a transmitting resonator was fabricated with graphite mirrors of diameter 70mm, curvature radius 100mm and connection holes 1.5mm in diameter [38]. The distance between mirrors, L, was varied in the range between 10 and 100mm.…”

“…After the test there was not found any noticeable change of radiotechnical characteristics of the antenna and its surface [lo]. The temperature of antenna body was not controlled during the discharges, and therefore special study was carried out when this conical antenna was repeatedly dc heated in vacuum up to 1000°C [37,38]. After 20 cycles there was not found any irreversible changes of the inner surface of antenna.…”