Abstract: A superconducting magnet arrangement having a sealed cryogenic environment utilizing liquid helium, a superconducting coil immersed in the liquid helium, a constant current power supply exterior of the cryogenic environment and connected to the coil by leads cooled by varying helium boil off and an electrical shunt connect across the magnet. Variations in the helium boil off are compensated by exposing the shunt to and cooling it by the same helium boil off or by exposing negative temperature coefficient device to such flow or by a combination of such methods.

Abstract: A current-limiting device for an alternating current system has at least two iron-cored saturable reactors for each phase, each reactor core being of double-window configuration with an alternating current winding on the central limb, and a superconducting bias winding screened alternating magnetic flux is in the form of a loop with two parallel sides which pass through the two windows of at least two of the reactor cores. For a three phase system the three pairs of reactors may be on a single bias winding loop or each pair may have its own bias winding. In a preferred construction two bias winding loops each link three reactor cores and each phase includes one reactor from each of the bias windings.