High Tc superconducting quick response nonlinear inductances and magnetic modulators

Remarkable nonlinear inductances due to the soft magnetic BH hysteresis characteristics are obtained for YBa₂Cu₃O_7-x disk-shaped cores at 77 K which are tightly wound with polyester-coated copper coils. The inductance changes from nearly zero due to the Meissner effect to that of an equivalent coreless coil as a result of the flux penetration effect due to increasing the exciting current or the applied external magnetic field. Values of inductances are almost constant from low frequency to at least 20 MHz, indicating that the high-T_c superconductor is a fast-response nonlinear inductor material. Fast-response magnetic modulators use one toroidal core or one pair of disk cores with a carrier frequency of more than 10 MHz and a signal frequency of 0 to 500 kHz