  Cable-in-Conduit Conductors (CICCs) are used in the fabrication of
superconducting fusion grade magnets. It acts as a narrow cryostat to provide
cryo-stability with direct contact of coolant fluid to conductor. The
superconducting magnets are cooled using forced flow (FF), supercritical helium
or two phase (TP) cooling through void space in the CICC. Thermo-hydraulics
using supercritical helium single phase flow is well-known and established.
Research topic of behavior of forced flow, two phase (TP) helium cooling in
CICC involves perceived risks of the CICC running into flow chocking and
possible thermo-acoustic oscillations leading to flow instabilities. This
research work involves study of forced flow two phase helium cooling in CICC
wound superconducting magnets. The TP flow provides cryo-stability by the
latent heat of helium not by enthalpy as in case of CICC being cooled with
supercritical helium. Study reveals some attractive regimes in the case of TP
cooling, at a given mass flow rate of single phase helium at the inlet and a
heat flux acting on the CICC. Analysis carried out predicts significant gains
with TP cooling on a prototype CICC, which is circular in cross section and
appropriate for fusion devices for high magnetic field applications. These
general formalisms may be extended to specific magnets wound with CICC. This
paper describes analysis of TP cooling of a CICC.

Fluid Dynamics