The Formation of a Tokamak-like Plasma in Initial Experiments Using an Outboard Plasma Gun Current Source
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Solenoid-free tokamak startup via point-source DC helicity injection is demonstrated on the Pegasus Toroidal Experiment using a high current density, low impurity plasma gun mounted near the outboard midplane. A threshold in the vacuum vertical magnetic field strength that allows the injected current filament to relax into a tokamak-like topology is observed. A simple 2-D model of the vacuum magnetic field suggests this threshold is the maximum field strength that allows a toroidally connected field null to form. Discharges with Ip ≈ 17 kA are produced using less than 2 kA of injected current and no inductive drive. The tokamak-like discharges exhibit current decay times about five times longer than the injected current decay, expansion of the plasma into the vacuum region and a significant increase in the line-integrated density.
KeywordsDC helicity injection Solenoid-free startup Plasma guns
- 12.A.J. Redd et al., will be published in this issue (2008)Google Scholar
- 13.C.R. Sovinec et al., Phys. Rev. Lett. 94, (2005)Google Scholar
- 14.N.W. Eidietis, Ph.D. Dissertation (University of Wisconsin – Madison, 2007)Google Scholar
- 15.I.H. Hutchinson, Principles of Plasma Diagnostics, 2nd edn. (Cambridge University Press, Cambridge, UK, 2002)Google Scholar