On current driven in low-s FRCs by prompt fusion-product losses

Certain plasma devices, e.g., tokamaks and field-reversed configurations (FRC), require strong electrical currents in the plasma to form their magnetic fields. Tokamaks, especially those with low aspect ratio, benefit from the naturally occurring bootstrap current generated by diffusive plasma cross-field transport which transfers momentum from trapped to passing particles. This reduces the needed size for an external current-drive power source, improving the energy balance for tokamaks considered for fusion reactors. FRCs differs from the tokamaks in many ways, including characteristics of their trapped particle populations and the current direction with respect to the magnetic field, conditions under which a bootstrap current should not occur. Here we describe parameters of a low-s kinetic FRC reacters, caused by flux-surface-normal electric fields generated by prompt fusion-product particle losses, which may occur and reach such a level that large beneficial azimuthal currents, comparable in size to that needed to sustain the FRC, would be generated and sustained. These same FRC-specific conditions would also allow direct energy conversion.