Recent progress in the design of stellarator experiments

Abstract

To evaluate stellarators as power plants, a helias configuration was developed by running high performance computer codes written at New York University. A modular coil set was found that had ample spacing for a reactor and took advantage of the concept of quasihelical symmetry. Since that time, the design has been further optimized and a similar stellarator has been discovered that has just two field periods and a plasma with the low aspect ratio 3.5. Its principal advantage is that in a flux coordinate system its magnetic-field structure comes close to having axial symmetry, so transport is predicted to be almost as good as that in a tokamak at high temperatures. Only 16 moderately twisted coils are required to produce the external magnetic field, and the configuration might well be viewed as a steady-state tokamak rather than an alternate concept.