The torsatron without toroidal field coils as a solution of the divertor problem

The torsatron without toroidal field coils is a configuration of the stellarator type which is obtained with a particularly simple set of conductors (ℓ helical windings and a vertical field). Here the case ℓ=3 is studied by numerical calculation. It is found that good magnetic surfaces exist. High values of rotational transform (ι/2π≃3) and shear (θ ≃ 0.5) can be obtained simultaneously with a relatively low mirror ratio along the field lines (B max /B min ≃ 1.2). The absence of separate toroidal field coils allows the design of an efficient divertor.