Flexible helical-axis stellarator

In a helical-axis stellarator of the type including a planar circular central winding, a planar toroidal magnetic field generating coils disposed about the central winding whose centers are located on a helical axis twisting about and spaced from the central winding to form a toroidal helix having M toroidal periods in which a helical axis plasma is magnetically confined, the improvement is described comprising: an 1=1 helical winding, where 1 is the toroidal winding multiplicity, disposed to spiral about and encompass the planar circular central winding one revolution for each period of the toroidal helix in close proximity to the central winding and in phase with the helical axis of the plurality of toroidal magnetic field generating coils so that currents in the helical winding and the central winding may be separately varied to contain the rotational transform, tau, of closed magnetic flux surfaces which confine the helical axis plasma for stably confining the plasma at finite beta values. The helical winding include separate winding layers disposed radially outward from the central winding so that separate currents may be applied to the separate layers of the 1=1 helical winding to effectively vary the radial space relationship of the effective center of the 1-1 helical winding relative to the central winding thereby varying the shear of the magnetic flux surfaces