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Collisional Merging Process of Field-Reversed Configuration Plasmas in the FAT-CM Device

Fumiyuki TANAKA, Tomohiko ASAI, Junichi SEKIGUCHI, Tsutomu TAKAHASHI, Junpei ISHIWATA, Takahiro EDO, Naoto ONO, Keisuke MATSUI, Shintarou WATANABE, Daiki HISHIDA, Daichi KOBAYASHI, Yousuke HIROSE, Akiyoshi HOSOZAWA, Yung MOK¹⁾, Sean DETTRICK¹⁾, Thomas ROCHE¹⁾, Hiroshi GOTA¹⁾, Michl W. BINDERBAUER¹⁾ and Toshiki TAJIMA^1,2)

College of Science and Technology, Nihon University, Tokyo 101-8308, Japan

1)

TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610, USA

2)

Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA

(Received 28 December 2017 / Accepted 8 July 2018 / Published 10 August 2018)

Abstract

In order to investigate the collisional merging process of field-reversed configurations (FRCs), the FAT device has recently been upgraded to FAT-CM, consisting of two field-reversed theta-pinch (FRTP) formation sections and the confinement section. Collisional merging of the two FRCs causes a conversion of the kinetic energy to mostly thermal ion energy, resulting in an increase of the ion pressure that greatly expands the FRC size/volume. This increase of the FRC size is observed by magnetic diagnostics in the confinement region, leading to an increase in the excluded flux; on a side note, these characteristics/phenomena have also been observed in C-2/C-2U experiments at TAE Technologies. The process of FRC formation, translation and collisional merging in FAT-CM has been simulated by Lamy Ridge, 2D resistive magnetohydrodynamics code, in which the same phenomenon of the excluded-flux increase via FRC collisional merging has been observed. Simulation results also indicate that there is an importance of the external magnetic field structure/profile in the confinement region, clearly affecting the FRC merging. Steeper magnetic field gradient by a strong mirror field appears to suppress the axial expansion of collided FRCs and lead a merged FRC to higher temperature.

Copyright (c) 2018 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

magnetically confined plasma, field-reversed configuration, high beta plasma, FRC merging, 2D resistive MHD simulation

DOI: 10.1585/pfr.13.3402098

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