The Digital Algorithm of Precision Estimation of the SIS-type Josephson Junction Critical Current

The problem of the automatic algorithm developing for estimating the critical current of the SIS-type Josephson junctions is considered. This problem is relevant for a physical experiment automation and for the junction parameters control during production. The algorithm proposed is based on statistical processing of the results of synchronous measurements of current and voltage samples at the Josephson junction excited by a sequence of the current pulses with a slow rising edge and fixed pulse ratio. We use a model of a composition of useful signal and white Gaussian noise with zero mean and unknown variance for test and measurement signals. We employ the contrast method to solve the problem of the a priori uncertainty of the noise variance. For this method, the difference in signals during the pulses of the current and during the pause between them is used. The relative total error of estimating the critical current in automatic mode is less than 0.2% for typical characteristics of measuring equipment.