Journal article Open Access
Harris, J. H.; Cantrell, J. L.; Hender, T. C.; Carreras, B. A.; Morris, R. N.
The addition of an ℓ = 1 helical winding to the heliac central conductor adds a significant degree of flexibility to the configuration by making it possible to control the rotational transform and shear. Such control is essential for an experiment because the presence of low-order resonances in the rotational transform profile can cause breakup of the equilibrium magnetic surfaces. The use of the additional winding also permits a reduction of the total central conductor current and can deepen the magnetic well.