Current distribution in a single-ply coil with conducting “insulation”

A coil made of a continuous rectangular conductor in the form of a single-layer cylindrical helix is analyzed to identify methods of improving the mechanical strength and energy efficiency of resistive systems for producing high magnetic fields with quasi-force-free windings. A characteristic feature of this helix is that the interturn insulation is replaced by a conductor of higher resistivity. An analysis is made of the direction of the resultant current density vector as a function of the ratio of the resistivities of the conductors and the winding angle. It is shown that in principle, the direction of this vector may be arbitrarily defined, by suitably selecting the resistivities of the conductors. In this case, the winding angle may be arbitrarily small. It is demonstrated that these helices will have a high mechanical strength, and when used in quasi-force-free windings they can appreciably reduce the axial current density, which helps to minimize the mechanical stresses and thereby improve the energy efficiency. Zh. Tekh. Fiz. 67, 96–100 (November 1997)