Measurement of critical current in superconducting rings

An experimental technique has been developed for the measurement of the critical current in superconducting rings. It is based on the detection of a voltage in a secondary coil when the current induced in the superconductor by a primary coil exceeds the critical value. The coils and superconductor are assembled on a ferromagnetic core to create a transformer. The technique uses a primary circuit containing a control coil with an iron core, and the primary coil of the transformer. This circuit is connected to a constant-voltage AC power supply, and the current is modified by changing the impedance of the control coil using a DC power supply.