Cycle Design for a Cryogenic Refrigeration System for FED with Forced-Flow Superfluid Helium Through Internally Cooled Conductors

摘要

A cryogenic refrigeration system has been designed for the specifications of the magnet system of the Fusion Engineering Device (FED). The unusual specification of an internally cooled cabled niobium titanium superconductor at a maximum field of 10 tesla, coupled with high ac losses and high neutron and gamma heating in the toroidal field coils led to the selection of a cooling system with superfluid helium at the inlet to the toroidal field coils. While highly unusual as a coil-cooling concept, the implications for the refrigeration system were not unfavorable and showed several features of interest. Among the favorable comparisons with conventional supercritical flow systems were reduced entropy generation in the coil due to pressure drops. However, the low inlet temperature and the high losses combined to require 63 MW of room temperature work on the helium, about 4 times that of the Isabelle refrigeration system, which the FED system resembles. (ERA citation 06:035734)