INJECTION AND SUSTAINMENT OF PLASMA IN A PREEXISTING TOROIDAL FIELD USING A COAXIAL HELICITY SOURCE

The spheromak device SPHEX has been modified by adding a current-carrying rod along the geometric axis, providing a preexisting toroidal field. We show that plasma can be successfully injected into such a field from a helicity source; the field assists plasma ejection from the gun and improves the coupling between gun and plasma, so that T(e), T(i), and the toroidal current all increase with rod current. The mechanism or plasma sustainment appears to be the same as that of the spheromak. These results represent a step towards the achievement of steady-state tokamak operation.