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Spectroscopic Measurement to Study Two-Fluid Relaxation in an Internal Coil Device Mini-RT

Mahajan-Yoshida has developed a new relaxation theory, by taking two-fluid effect into account. This theory indicates that the plasma flow confines high beta plasma. We have constructed an internal coil device Mini-RT with high temperature superconductor (HTS) coil, and are expecting the high beta plasma with the fast toroidal plasma flow by inducing the radial electric field. In order to measure the radial profile of the plasma flow we introduced a spectroscopy. By setting up two cylindrical lenses between a monochromator and a charge-coupled device (CCD) detector, we could not only correct astigmatism of the monochromator but also increase the resolution of wavelength up to 2.55 pm/pixel which is equal to the measurement of the plasma flow up to 1.6 × 103 m/s. Additionally we are setting up an opposed fiber array for an accurate measurement. In the Mini-RT device the plasma was produced by 2.45 GHz ECH (Electron Cyclotron Heating) system with the power of 2.6 kW. Typical electron density and temperature are more than 10 m and 10–20 eV, respectively. The ion temperature measured by this spectroscopy system was 1.0 ± 0.3 eV and the plasma flow velocity was comparable to the resolution of this spectroscopic system. Although the plasma should flow to the toroidal direction by the ∇B/curvature drift in the internal coil device, the drift velocity of 1.3 × 103 m/s is not detectable with this spectroscopy. If the radial electric field of 160 V/m or more is induced in the plasma, the plasma flow due to the E × B drift could be measured with this system.