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Study of the Axial Ion Confinement Time for High Particle Flux Operations of GAMMA 10/PDX

Kazuya ICHIMURA, Yousuke NAKASHIMA, Md. Maidul ISLAM, Md. Shahinul ISLAM, Keita SHIMIZU, Kazuma FUKUI, Masato OHUCHI, Mafumi HIRATA, Ryuya IKEZOE, Shuhei SUMIDA, Masayuki YOSHIKAWA, Naomichi EZUMI, Mizuki SAKAMOTO, Makoto ICHIMURA and Tsuyoshi IMAI

Plasma Research center, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577, Japan

(Received 30 November 2015 / Accepted 18 February 2016 / Published 15 April 2016)

Abstract

Characteristics of axial plasma confinement in recent high-density mode of GAMMA 10/PDX tandem mirror is reported in this paper. The parameter of the end-loss ion flux is an important issue in the divertor simulation studies in GAMMA 10/PDX. With an ICRF heating in the anchor-cells of the machine, large increase in the electron line-density in the central-cell (NLCC) and the end-loss particle flux were observed. The behavior of the electron line density, plasma temperature and the amount of end-loss ion flux during the experiments suggested that the mechanism of the axial ion loss was changed due to the increase of ion collision frequency. In contrast with the standard operations of GAMMA 10/PDX, plasma parameters in recent high-density operations stays in the range of high collision frequency. In such collisional plasma, the end-loss ion particle flux show linear dependence on the plasma density instead of the parabolic dependence expected in plasmas of low collision-frequency. In the high collision frequency plasma, it is notable that plasma potential φ largely changes the dependence of the particle flux on the plasma density.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

tandem mirror, GAMMA 10/PDX, mirror confinement, divertor simulation, particle flux

DOI: 10.1585/pfr.11.2405045

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