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Experimental study on the formation and evolution of unconfined counter-helicity spheromaks merging using magnetized coaxial plasma gun

Part of: Open Magnetic Systems for Plasma Confinement

Published online by Cambridge University Press:  25 October 2024

Liangwen Qi Open the ORCID record for Liangwen Qi [Opens in a new window] ,
Jian Song ,
Fantao Zhao ,
Siqi Yu ,
Chongxiao Zhao ,
Huijie Yan  and
Dezhen Wang
Liangwen Qi*
Affiliation:
School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070, Gansu, PR China Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, PR China
Jian Song
Affiliation:
Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, PR China
Fantao Zhao
Affiliation:
Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, PR China
Siqi Yu
Affiliation:
Department of Physik und Astronomie, Ruhr-University Bochum, Bochum, D-44780, Germany
Chongxiao Zhao
Affiliation:
State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, PR China
Huijie Yan
Affiliation:
Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, PR China
Dezhen Wang
Affiliation:
Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, PR China
*
†Email address for correspondence: [email protected]
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Abstract

The formation and evolution of unconfined counter-helicity spheromaks merging have been experimentally investigated by using a magnetized coaxial plasma gun. By comparing the time-dependent photodiode signals and plasma radiation images of counter-helicity spheromaks merging and plasma jets merging, it is found that the field-reversed configuration (FRC) plasma formed by counter-helicity spheromaks merging has a distinct contour and a long maintenance time. For plasma jets merging, the resulting plasma has no discernible contours and a shorter lifetime. In addition, it is inferred from these data that stagnation heating and magnetic reconnection events occur during the counter-helicity spheromaks merging, causing a rapid rise in plasma pressure at the merging midplane and sharp kinks in the field lines near the merger region. By changing different operating parameters and observing the impact on the merger characteristics, it is suggested that the qualitative dynamics of the FRC plasma depends on the balance between the plasma pressure and the magnetic pressure. The high discharge voltage breaks the equilibrium in the merged body, while the large gas-puffed mass just weakens the compression effect of the merged body. These results give us an intuitive understanding of the counter-helicity spheromak merger process and its dependence on discharge parameters, and also provide a distinct perspective for the optimal design of FRC.

Keywords

coaxial gunspheromakplasma jetcollisional mergingfield-reversed configuration
Type
Research Article
Information
Journal of Plasma Physics , Volume 90 , Issue 5 , October 2024 , 975900501
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Copyright
Copyright © The Author(s), 2024. Published by Cambridge University Press

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