Evolution of Normal Zones and Temperature in a Superconductor Cooled Internally with Helium-II
In an effort to understand the stability mechanisms of internally cooled superconductors in the He II regime, measurements are made on a hollow composite superconductor open at both ends to a bath of subcooled He II. The vacuum insulated conductor, 3 meters long and 1.1 millimeters internal diameter, carries a transport current in a transverse background field of up to 11 Tesla. Heaters mounted on the conductor at its center are used to initiate local disturbances. The propagation or collapse of these disturbances is then observed using a series of temperature sensors and voltage taps attached symmetrically about the heater. The stability margin of the conductor is mapped out, and, using a simple theory, the pressure rise and thermal expulsion velocity are derived from the voltage and temperature profiles.
KeywordsConvection Enthalpy Helium Epoxy Brittle
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