Fast digital method of critical current measurement of superconducting tunnel junction

This article describes a new computerized method of the fast measurement of the critical current I-C of superconducting weak links. The method is based on the electronic transformation of the current to the time measurement. Sinusoidal current is also supplied which simplifies the filtration of the mains noise as well as helps to suppress a common mode voltage and inductive voltages. The instrument allows for the measurement of the critical current with a 1 muV voltage criterion. As one period of sinusoidal current is sufficient to determine I-C, the measurement time is of the order of milliseconds for the current supply at a frequency range of 300-1000 Hz. The instrument has been tested by the measurement of the critical current of Josephson junctions as functions of magnetic field or temperature. (C) 2000 American Institute of Physics. [S0034-6748(00)04711-0].