Thin film superconducting switches

Although thin superconducting films have been suggested for use in switching electrical power, virtually no experimental work has been reported. Our present research investigates thin films switched by applying a fast pulse of magnetic field perpendicular to the plane of the film. Short sections of niobium films, carrying approximately half of their critical current, were switched completely into the normal state upon application of pulsed fields as low as 0.02 T (200 gauss). The field pulse has a rise time and length of order 10 μsec, but switching was more rapid. It is shown that the magnitude of the field, and not its rise time, cause the switching. Recovery times, upon removing the current source, were also of order 10 μsec.