Superfluid helium for stabilizing superconductors against local disturbances

Heat can be easily removed from a solid conductor immersed in a superfluid helium bath at atmospheric pressure, because of its very large thermal conductivity and a noticeable heat capacity, similar to that of saturated helium I. As a result, superconducting composites can withstand large thermal disturbances without a generalized quench. A series of non-inductive coils cooled by superfluid helium channels have been tested to determine if a normal zone created by a small heater recovers. After the energy is introduced in a few milliseconds, the development of the normal zone versus time is measured as a function of different important parameters including: transport current, external field, initial energy, thickness of helium channels, size of the spacers. Curves of critical energies, maximum energies for which a recovery to the superconducting state is possible, are given. Our results show the great value of superfluid helium for stabilizing superconductors submitted to local thermal disturbances.