Assessment of a Compact Torsatron Reactor, ATFSR

Confinement and engineering issues of a small (average minor radius ā ≃ 1 m) moderate-aspect-ratio torsatron reactor are evaluated. The Advanced Toroidal Facility design is used as a starting point because of its relatively low aspect ratio and high beta capabilities. The major limitation of the compact size is the lack of space under the helical coils for the blanket and shield. Some combination of lower aspect ratio coils, higher coil current density, thinner coils, and more effective shielding material under the coils should be incorporated into future designs to improve the feasibility of small torsatron reactor concepts. Current neoclassical confinement models for helically trapped particles show that a large radial electric field (in terms of the electric potential, eφ/T ≥ 3) is necessary to achieve ignition in a device of this size.