|sieck_icc2006.pdf||2006-02-23 14:03:16||Paul Sieck|
Spheromak Formation Observed in HIT-SI
Author: Paul E Sieck
Submitted: 2005-12-21 19:31:35
Co-authors: W. T. Hamp, T. R. Jarboe, G. J. Marklin, B. A. Nelson, R. G. O'Neill, A. J. Redd, R. J. Smith, G. L. Sutphin, J. S. Wrobel
University of Washington
Box 352250, University of Wash
Seattle, WA 98195-2
HIT-SI is an experiment in which spheromaks are generated and sustained by
Steady Inductive Helicity Injection (SIHI)[1,2]. Helicity injection is
provided at a constant rate by means of two AC RFP-like half-torus
"helicity injectors", phased in quadrature and connected to the
main chamber so as to drive a rotating n=1 mode at about 5 kHz.
Recent experiments with the HIT-SI device have produced toroidal plasma
currents in the spheromak confinement region, with an n=0 axisymmetric
component (up to 10 kA) in excess of the oscillating n=1 poloidal injector
component. Internal magnetic probe measurements demonstrate the formation
of a magnetic axis, and the internal field fluctuations due to the 5 kHz
injector oscillations are relatively suppressed near this magnetic axis.
These results indicate the formation of an axisymmetric spheromak equilibrium,
with only 3 MW of applied power.
Numerical superpositions of 3-D Taylor equilibria will also be presented,
to illustrate the relationship between the oscillating injector flux and
an axisymmetric closed-flux spheromak equilibrium in the limit of full
magnetic relaxation. These calculations show that a closed-flux spheromak core
may exist in the experiment, even with a toroidal plasma current that is as
small as 92% of the maximum poloidal current through the oscillating injector.
 P.E.Sieck et al., "Initial Studies of Steady Inductive Helicity
Injection on the HIT-SI Experiment", IEEE Trans. Plasma Sci., vol. 33,
no. 2, pp. 723-728 (2005).
 P.E.Sieck et al., "Demonstration of Steady Inductive Helicity Injection",
Nuc. Fusion, in press (2006).
If not selected for oral, please place among the HIT-SI posters, after the poster by Redd et al.