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Imposed Dynamo Current Drive

Author: Thomas R jarboe
Requested Type: Consider for Invited
Submitted: 2012-12-06 21:41:49

Co-authors: B. S. Victor, B. A. Nelson, C. J. Hansen, C. Akcay, A. C. Hossack, G. J. Marklin

Contact Info:
University of Washington
Box 352250
Seattle, WA   98195
USA

Abstract Text:
A mechanism for Steady Inductive Helicity Injection current drive has been discovered where the current driving fluctuations are not generated by the plasma but rather are imposed by the injectors.[T. R. Jarboe et al., Nucl. Fusion 51, 063029 (2011).] Sheared flow of the electron fluid distorts the imposed fluctuations to drive current. The model accurately predicts the time dependent toroidal current, the injector impedance scaling, and the profile produced in the HIT-SI experiment. These results show that a stable equilibrium, which is not undergoing relaxation, can be efficiently sustained with imposed fluctuations. In addition, the current profile can, in principle, be controlled. Both are large steps for controlled fusion. Some of the effects of the fluctuations on the confinement of tokamak and spheromak reactors are assessed and the degradation may be tolerable. An experiment to demonstrate profile control is described as well as one to test the confinement of an equilibrium sustained by Imposed Dynamo Current Drive.

Conventional RF and neutral beam current drive are very power-inefficient leading to an unacceptably high recirculating power fraction in a fusion reactor. [Zohm H., Fusion Sci. Technol. 58, 613 (2010)] Lack of profile control can causes disruptions, a major weakness of the tokamak configuration. Thus efficient current drive and profile control are important goals of fusion research.

Characterization: 1.0

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