IShTAR: A test facility to study the interaction between RF wave and edge plasmas.

Existence of high electric fields near an RF antenna launcher causes a number of parasitic phenomena, such as arcing and impurity release, which seriously deteriorate the performance of an Ion Cyclotron Range of Frequencies (ICRF) heating scheme in fusion devices. Limited accessibility of the near antenna region in large-scale fusion experiments significantly complicates the associated experimental studies. The IShTAR test facility has been developed with the requirement to provide a better accessibility and diagnosability of plasmas in the direct vicinity of an ICRF antenna. The purpose of this work is to give a detailed description on the experimental setup and the available diagnostics. Furthermore, the paper will demonstrate the capability of the experiment to study phenomena near an ICRF antenna launcher which are relevant for large-scale fusion ion cyclotron resonance heating systems.

Polarization Stark spectroscopy for spatially resolved measurements of electric fields in the sheaths of ICRF antenna.

A multichannel spectroscopic diagnostic based on the Stark effect on helium lines was developed and implemented in IShTAR (Ion Cyclotron Sheath Test ARrangement) to measure the spatial distribution of electric fields across the radio frequency sheaths of the ion cyclotron antenna. Direct measurements of the DC electric fields in the antenna sheaths are an important missing component in understanding the antenna-plasma edge interactions in magnetically confined fusion plasmas since they will be used to benchmark theoretical models against real antenna operation. Along with the high-resolution Czerny-Turner monochromator and a detector with an intensifier, the hardware relies on the 2 chained set of linear-to-linear fiber bundles that provide seven optical channels capable of resolving an 8.4 mm region in the vicinity of the antenna's box. The diagnostic is supported with local helium gas puff, enabling it to operate in nonhelium plasmas. Spatially resolved electric field was measured for two discharge configurations, one with and one without the ICRF antenna. The results show a clear difference in the shape of the DC electric field's spatial profile for the two cases studied, with the elevated values when the ICRF antenna was operating. This demonstrates the ability of the diagnostic to measure even small relative changes in the intensity of the electric field.

Development of a spectroscopic diagnostic tool for electric field measurements in IShTAR (Ion cyclotron Sheath Test ARrangement).

IShTAR, Ion cyclotron Sheath Test ARrangement, is a linear device dedicated to the investigation of the edge plasma-ICRF (Ion Cyclotron Range of Frequencies) antenna interactions in tokamak edge-like conditions and serves as a platform for a diagnostic development for measuring the electric fields in the vicinity of ICRF antennas. We present here our progress in the development of an optical emission spectroscopy method for measuring the electric fields which concentrates on the changes in the helium spectral line profiles introduced by the external electrical field, i.e., the Stark effect. To be able to fully control the operating parameters, at the first stage of the study, the measurements are conducted on a planar electrode installed in the centre of the plasma column in IShTAR's helicon plasma source. At the second stage, the measurements are performed in the vicinity of IShTAR's ICRF antenna.

Isotope effect and multiscale physics in fusion plasmas.

The mechanism governing the impact of the mass isotope on plasma confinement is still one of the main scientific conundrums facing the magnetic fusion community after more than thirty years of intense research. We have investigated the properties of local turbulence and long-range correlations in hydrogen and deuterium plasmas in the TEXTOR tokamak. Experimental findings have shown a systematic increasing in the amplitude of long-range correlations during the transition from hydrogen to deuterium dominated plasmas. These results provide the first direct experimental evidence of the importance of multiscale physics for unraveling the physics of the isotope effect in fusion plasmas.

Development of the gas-puff imaging diagnostic in the TEXTOR tokamak.

Gas puff imaging (GPI) [S. J. Zweben, D. P. Stotler et al., Phys. Plasmas 9, 1981 (2002); R. J. Maqueda, G. A. Wurden et al., Rev. Sci. Instrum. 74, 2020 (2003)] is a powerful diagnostic that permits a two-dimensional measurement of turbulence in the edge region of a fusion plasma and is based on the observation of the local emission of a neutral gas, actively puffed into the periphery of the plasma. The developed in-vessel GPI telescope observes the emission from the puffed gas along local (at the puff) magnetic field lines. The GPI telescope is specially designed to operate in severe TEXTOR conditions and can be treated as a prototype for the GPI systems on next generation machines. Also, the gas puff nozzle is designed to have a lower divergence of the gas flow than previous GPI diagnostics. The resulting images show poloidally and radially propagating structures, which are associated with plasma blobs. We demonstrate that the local gas puff does not disturb plasma properties. Our results indicate also that the neutral gas emission intensity is more sensitive to the electron density than the electron temperature. Here, we present implementation details of the GPI system on TEXTOR and discuss some design and diagnostic issues related to the development of GPI systems in general.

[Hemorheological disorders in patients with critical ischemia of the lower limbs of atherosclerotic genesis]. / Gemoreologicheskie rasstroistva u bol'nykh s kriticheskoi ishemiei nizhnikh konechnostei ateroskleroticheskogo geneza.

A comparative analysis of hemorheological indices was carried out in 105 patients with different variants of the course of critical ischemia of extremities and in 35 patients with intermittent claudication (as a reference group). Disturbances of the rheological properties of blood were revealed in the extremity muscles and in 62.4-68.8% of patients with a low functional reserve of the extremity muscles. All the examined patients had a low level of total cholesterol against the background of dyslipoproteinemia characterized by a decreased level of cholesterol of high density lipoprotein with a mild elevation of the concentration of cholesterol of low and very low density lipoproteins.

[Mechanisms of the positive clinical effect of plasmapheresis for arteriosclerosis obliterans in the lower extremities]. / Mekhanizmy polozhitel'nogo klinicheskogo éffekta plazmafereza pri obliteriruiushchem ateroskleroze sosudov nizhnikh konechnostei.

Some mechanisms of clinical improvement of peripheral atherosclerosis were studied on the basis of changes occurred in hemorheological parameters and lipid spectrum in 107 patients with atherosclerosis obliterans of the lower extremity vessels who had undergone 166 courses (468 sessions) of therapeutical plasmapheresis. In addition to improved lower extremity blood flow in 94.8% of patients with Stage II ischemia and 78.2% with Stage III, clinically improved cerebral circulation was seen in 87.6% and clinically better coronary circulation in 85.2%. This suggests definite unique hemodynamic effects of plasmapheresis. The paper also indicates that there are at least three mechanisms providing a positive clinical effect of plasmapheresis in peripheral atherosclerosis: (1) peripheral macro- and microhemodynamic improvement due to decreased levels of plasma and perimembrane fibrinogen and increased erythrocyte deformability; (2) a decrease in thrombus risk due to lower fibrinogen levels and fibrinolytic activation; (3) monitoring risk factors of atherosclerosis due to lower levels of atherogenic lipoproteins, triglycerides, and cholesterol.