Two plasma diagnostics in ITER will use cube-corner reflectors (CCR): poloidal polarimetry and toroidal interferometry/polarimetry. The multichannel poloidal polarimetry system is planned to operate at a wavelength of 118.8μm. The multichannel toroidal interferometry/polarimetry system is based on a CO2 laser operating at wavelengths of 10.6 and 9.27μm. The long term sputtering by charge exchange atoms and/or deposition of carbon-based (or beryllium-based) contaminant layers can affect the optical properties of the CCR. The role of both these potentially deleterious effects on the CCR operation is analyzed in this article, taking into account the probing beam wavelength and the CCR locations. The conclusion is that for the intended use of a CCR in the poloidal polarimetry at 118μm neither erosion nor deposition should pose a problem. On the other hand, in the toroidal interferometry/polarimetry system operating at 10μm, care must be taken to reduce the charge exchange atom flux and it is likely that deposition will occur and could have deleterious effects especially on the polarization properties of the reflected radiation.
In the IPP-Kharkiv there are two torsatrons (stellarators) in operation, and in both of them Alfvén resonance heating under high-k
∥ conditions is used. This method of heating is advantageous for small-size devices, since in contrast to the minority and second-harmonic heating it can be realized at lower plasma densities. A series of experiments has been performed at the Uragan-3M torsatron with an aim to investigate the features of the discharge with a three-half-turn antenna. Electron temperatures in the
range are achieved at plasma densities
. The plasma energy content has increased by a factor of 2 with respect to the plasma produced with the frame antenna. A new four-strap shielded antenna has been manufactured and installed in the Uragan-2M. A high-frequency discharge for wall conditioning is introduced in the Uragan-2M torsatron. The discharge is sustained by a specially designed small frame antenna, and efficient hydrogen dissociation is achieved. A self-consistent model has been developed for simulation of plasma production in ICRF. The model includes a set of particle and energy-balance equations for the electrons, and the boundary problem for the Maxwell equations. The first calculation results on RF plasma production in the Uragan-2M stellarator with the frame-type antenna are presented.
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.
The possibility to use the carbon-graphite materials (CGM) instead of metals for fabrication of the in-vessel components for plasma diagnostics in the mm and sub-mm ranges on large-scale fusion devices was investigated. The reflectivity of different kinds of CGMs (more than 20) was measured in the wavelength range of 10 pm-30mm and was found to be only little below the values for metal analogues. The effects of surface roughness, pulsed plasma impact, heating and neutron irradiation on the retlectivity of CGM-made reflectors were analyzed. The role of graphite protection of the first wall in the energy balance in a fusion reactor was evaluated using the reflectivity data obtained. The working characteristics of antennae, waveguides and resonator fabricated of CGMs are presented as measured before and after pulsed plasma impact and/or heating up to 1 oooc.The CGM-made diagnostic components demonstrated much stronger resistance to pulsed power plasma impact than metal-made ones and at the same time reasonable working characteristics. Therefore they can successfully replace the metallic components in cases when similar (h., CGM) materials are used for the first wall protection.
A modified method of dual polarization single line microwave backscattering is proposed for correlation and spectral studies of density fluctuations in plasma with known geometry of magnetic field (stellarator with low β plasma, reflex discharge). Simultaneous launching of microwaves of both ordinary (O) and extraordinary (X) polarization via the same antenna has an advantage for correlation measurements of fluctuations in adjacent plasma layers because a procedure of separation of reflected waves is simplified.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.