Results from helical axis stellarators

Helical axis stellarators produce magnetic surfaces of high rotational transform and moderate shear solely by means of external currents, with the promise of high β. Several machines with quite different toroidal, helical, and “bumpy” Fourier components of magnetic field are now producing results, including high quality magnetic surfaces, confinement mode transitions, configuration studies, and confinement consistent with International Stellarator Scaling (ISS95) scaling up to Te∼2 keV. These devices permit concept evaluation over an unprecedented configuration space, and allow basic comparisons with those designed by established and alternative optimization strategies.