Plasma confinement in the GAMMA 10 tandem mirror

The central cell density and the diamagnetic signal were doubled as a resul t of plug potential formation by ECRH in hot ion mode experiments on the GA MMA 10 tandem mirror. In order to obtain these remarkable results, the axis ymmetrized heating patterns of ECRH and ICRF heating were optimized. Furthe rmore, conducting plates were installed adjacent to the surface of the plas ma along the flat shaped magnetic flux tube located in the anchor transitio n regions; the plates may contribute to the reduction of some irregular ele ctric fields produced possibly with ECRH in these thin flux tube regions. T he conducting plates contributed to reducing the radial loss rate to less t han 3% of the total particle losses, along with improvements in the reprodu cibility of the experiments and the controllability of the potential confin ement. The increases in central cell density and diamagnetism in associatio n with the increase in plug potentials scaled well with increasing ECRH pow er. A plug potential of 0.6 kV and a density increase of 100% were achieved using an ECRH power of 140 kW injected into both plug regions. The plasma confinement was improved by an order of magnitude over a simple mirror conf inement owing to the tandem mirror potential formation.