Analytical electromagnetic calculations for practical superconductors

The current distributions of twisted long filamentary composites are studied during the current sweep and under the transverse and longitudinal external field, using the inductance matrix among superconducting helical filaments and the inductive voltage between filaments and the external coil in the circuit equation. The self- and mutual inductances of helical conductors with a uniform helical current density are approximately calculated from the analytical expressions of long helical thin conductors. In addition, the magnetic field and the vector potential distributions of a twisted superconducting composite are also obtained by the numerical integral calculation over the cross section of the analytical expressions for the magnetic field and vector potential due to an infinitely long helical conductor