Plasma Confinement and Behavior of Plasmas in the Minimum-B Region of the GAMMA 10 Tandem Mirror.

Recent results of the plasma confinement and the behavior of the edge plasma in the minimum-B regions of the GAMMA 10 tandem mirror are described. In this experiment conducting plates are newly installed in the anchor-cells in order to improve the performance of plasma confinement. The conducting plates are fixed closely to the plasma surface where the cross-section of the plasma is flatly e]elongated in the anchor transition region. After conditioning the conducting plates, basic characteristics on the conducting plates are investigated. A fairly good symmetry between the two plates facing each other is found in the drain current and in the floating potential. The axial profiles of these measured data also show a symmetry with respect to the central-cell mid plane. The dependence of the resistance connecting the plates to the machine ground shows that the floating condition of the plates provides the better property of particle confinement. As the result of optimization of the heating and gas puffing systems a s significant improvement of the plasma parameters is observed during potential formation. According to the increase of plug ECRH power, the central-cell line density and the diamagnetism increase and both parameters are nearly doubled at the ECRH power of 140kW under the floating condition of the conducting plates.