Conventional stellarators utilize low-multipole-order helical windings, ℓ = 2 or 3, because a high-multipole-order helical winding results in localization of the rotational transform near the plasma surface. If, however, a carefully chosen axisymmetric poloidal magnetic field is added, high-shear, high-multipole-order (ℓ ≈ 6–9) stellarator configurations become possible without a vanishing rotational transform in the plasma interior. Because of the well-known potential advantage of non-circular cross-section plasmas, such as the Doublet configuration over the circular cross-section tokamak, the Doublestar was chosen for a numerical study. Included in this study was the question of the sensitivity of the Doublestar configuration to error fields. As expected, it was found that the size of islands produced by error fields is relatively small because of the large shear of the Doublestar.
Magnetic systems of the stellarator type in the presence of a solenoid with a helical magnetic axis