Characterization of Gaseous Helium Flow Cryogen in a Flexible Cryostat for Naval Applications of High Temperature Superconductors

A fifty meter proof of concept demonstrator was developed utilizing gaseous helium as a cryogen for the use in a high temperature superconductor (HTS) based degaussing system for use on Navy ships. Increased signature requirements as Navy future missions move into littoral waters have resulted in a new copper degaussing system. This system has an increased weight and installation cost because of the additional copper cable required. High temperature superconductors have been suggested as a replacement to the copper based cable to reduce system weight while maintaining the desired ship´s magnetic signature. A feasibility study was conducted in 2004 that showed that a superconductive system provided the same performance at a lower cost and at a lower system weight. Many terrestrial superconducting cable projects use liquid nitrogen as the cryogen to keep the cable cold. However, an inert, gaseous cryogen would be preferred for naval applications, but such a cooling system has never been demonstrated in a power cable. This paper describes the experimental setup and preliminary results of testing a helium cooled loop for use in a HTS based degaussing system.