The Effect of Current Magnitude upon the Behavior of a Superconducting Bolometer in Its Transition Region

A simple theoretical analysis of the superconducting bolometer in transition is shown to be useful in predicting phenomena such as the shape of the transition curve and the dependence of the bolometer time constant upon the current magnitude. The analysis holds for bolometer currents smaller than a critical value which is equal to the square root of the ratio of the bolometer cooling constant to the bolometer dR/dT. For bolometers constructed in this laboratory this critical current value falls between 15 and 30 ma. Qualitative extension of the theory to the case of large bolometer currents is made by considering the presence of regions at different temperatures within the bolometer and by summarizing the possible effects of the magnetic field due to the bolometer current upon the transition. Experimentally obtained transition curves are given for both small and large bolometer currents.