Magnetic Reconnection in the Spheromak: Physics and Consequences
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2007-01-11
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Citation of Original Publication
Hooper, E.B., Cohen, B.I., Hill, D.N. et al. Magnetic Reconnection in the Spheromak: Physics and Consequences. J Fusion Energ 26, 71–75 (2007). https://doi.org/10.1007/s10894-006-9065-y
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
Magnetic reconnection in the spheromak changes magnetic topology by conversion of injected toroidal flux into poloidal flux and by magnetic surface closure (or opening) in a slowly decaying spheromak. Results from the Sustained Spheromak Physics Experiment, SSPX, are compared with resistive MHD simulations using the NIMROD code. Voltage spikes on the SSPX gun during spheromak formation are interpreted as reconnection across a negative-current layer close to the mean-field x-point. Field lines are chaotic during these events, resulting in rapid electron energy loss to the walls and the low Tₑ < 50 eV seen in experiment and simulation during strong helicity injection. Closure of flux sufaces (and high Tₑ ) can occur between voltage spikes if they are sufficiently far apart in time; these topology changes are not reflected in the impedance of the axisymmetric gun. Possible future experimental scenarios in SSPX are examined in the presence of the constraints imposed by reconnection physics.