Experimental results from the Sustained Spheromak Physics Experiment, SSPX, are reviewed and applied to published reactor configurations. The results include several important features, including low fluctuation levels, (apparent) good magnetic flux surfaces, and moderate beta. Additional features needed for an attractive reactor but not yet demonstrated experimentally are identified by comparison with the reactor designs, and possible alternatives to a fully steady-state device are discussed.

A new 5kV, 1.5MJ modular capacitor bank has been designed for the Sustained Spheromak Physics Experiment (SSPX) at LLNL. The new bank consists of thirty 4mF capacitors that are independently controlled by light-triggered thyristors. By closing all switches simultaneously, the bank will provide a mega-ampere discharge. The new bank will also allow additional capabilities to SSPX, including higher peak gun current, longer current pulses, and multi-pulse plasma buildup. Experiment results for a single stage prototype will be presented, deliver a single large current spike, or, switches can be triggered in sequence to deliver a longer lower current pulse. Multiple pulses can be created by triggering sections of the modular bank in intervals.

The neutral beam current required to sustain the MX plasma is calculated for the plasma modeled by (a) a flat-top radial density profile and (b) a diffuse radial profile. Estimates of the plasma length are obtained from Fokker-Planck calculations and a three-dimensional guiding-center equilibrium code. Beam trapping efficiency is calculated from a model taking into account the spatial dimensions of the beam and plasma. The sensitivity to variations of magnetic field and plasma beta is calculated for the plasma parameters n tau, beam current, and axial scale length.