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(ICP/04) Sustained Spheromak Physics Experiment

(This paper was rapporteured in lecture EX4/1)

E. B. Hooper, R. H. Bulmer, B. I. Cohen, D. N. Hill, L. D. Pearlstein, K. I. Thomassen, R. D. Wood

Lawrence Livermore National Laboratory Livermore, CA 94551 USA

A. D. Turnbull, R. Gatto*

General Atomics San Diego CA 92121 USA
* Present address: Department of Physics, University of Wisconsin Madison, WI 53706, USA

T. Jarboe

University of Washington Seattle, WA 98195 USA

C. W. Domier

University of California at Davis Davis, CA 95616 USA

Abstract.  The Sustained Spheromak Physics Experiment, SSPX, will study spheromak physics with particular attention to energy confinement and magnetic fluctuations in a spheromak sustained by electrostatic helicity injection. In order to operate in a low collisionality mode, requiring Te > 100 eV, vacuum techniques developed for tokamaks will be applied, and a divertor will be used for the first time in a spheromak. The discharge will operate for pulse lengths of several milliseconds, long compared to the time to establish a steady-state equilibrium but short compared to the L/R time of the flux conserver. The spheromak and helicity injector (``gun'') are closely coupled, as shown by an ideal MHD model with force-free injector and edge plasmas. The current from the gun passes along the symmetry axis of the spheromak, and the resulting toroidal magnetic field causes the safety factor, q, to diverge on the separatrix. The q-profile depends on the ratio of the injector current to spheromak current and on the magnetic flux coupling the injector to the spheromak. New diagnostics include magnetic field measurements by a reflectometer operating in combined O- and X-modes and by a transient internal probe (TIP).

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IAEA 2001