First Results and Future Research Plan of Divertor Simulation Experiments Using D-Module in the End-Cell of the GAMMA 10/PDX Tandem Mirror

Abstract

In the new research plan of Plasma Research Center of the University of Tsukuba, a high heat-flux divertor simulator (E-Divertor) was proposed by using an end-mirror exit of a large tandem mirror GAMMA 10/PDX device. Experiments for characterization of end-loss plasma flux have been extensively performed at the end-mirror region of GAMMA 10/PDX and detailed behavior of end-loss particles has been investigated. In standard hot-ion mode plasmas (n_e0 ~ 2×10¹⁸ m^-3, T_i0 ~ 5 keV), the energy analysis of ion flux was performed by using end-loss ion energy analyzer (ELIEA). It was found that the high ion temperature (100 - 400 eV) is generated and has a liner relationship between diamagnetism in the central-cell. The ion temperature determined from the probe and calorimetric measurements gives a good agreement with the ELIEA measurement. Additional ICRF heating in the anchor-cell showed a significant increase of particle flux, which indicated an effectiveness of additional plasma heating in adjacent cells. Superimposing the ECH pulse of 380 kW, 5 ms induces a remarkable enhancement of heat flux and a peak value in the net heat-flux density more than 10 MW/m² was attained during the ECH injection, which comes up to the heat-load level of the divertor plate of ITER. Recently a large-scale divertor simulation experimental module (D-module) was installed in the west end-cell and the first plasma irradiation experiments onto a new tungsten V-shaped target were successfully performed. A number of interesting results such as neutral compression, enhancement of recycling and impurity radiation during noble gas injection, have been observed.