Force-free coil principles applied to high-temperature superconducting materials

A brief outline is given of force-free magnetic-field configurations, in which the current flows parallel to the magnetic field vector, that have the potential to raise the critical magnetic field and current-density limits. The advantages of force-free cables and coils are enumerated. The resulting improved levels of critical current density are noted. The authors describe the parameters governing cable and coil designs giving large values of central magnetic-field strengths, relative to a supporting coil, to produce maximum magnetic-field strengths in small experimental volumes.