Cable-In-Conduit Superconductors for Fusion and Other
Applications
The Plasma Science and Fusion Center has been active for more than
a decade in the development of high-performance internally cooled superconductors.
The most recent project completed is a 1 m inner diameter coil which operates
at 10 tesla, at an overall current density of 5,000 A/cm2. The coil must
function under high rates of field change, and has been tested at 5 tesla/second.
The coil uses 40 kA Nb3Sn conductors which are wound in place before heat
treatment, allowing small radius bends in the winding which would not be
possible with conventional Nb3Sn technology. This type of conductor comprises
a multi-strand cable of superconducting wires within a tube-like conduit,
with single-phase supercritical helium filling the cable voids within the
conduit. With this geometry, all the helium in the system is contained
within the conductor conduit, eliminating the need for a helium cryostat,
and effectively mitigating many of the operational problems associated
with the more common two-phase helium systems.
This conductor design has been accepted as the baseline for the International
Thermonuclear Experimental Reactor ( ITER)
magnet designs. The Incoloy 908 conduit material, developed at MIT jointly
by the Plasma Science and Fusion Center, the Department of Materials Science
and Engineering, and industry, has been accepted as the conduit material
of choice for this project. This conductor design has also been adopted
for the TPX
device to be built at PPPL (Princeton Plasma Physics Laboratory.) Other
cable-in-conduit conductors have been developed for large-scale DC applications
such as MHD and particle detector magnets.
In mid-1996, the Technology Division commissioned a new facility for use in
testing full-scale cable-in-conduit superconductors and joints. The Pulse
Test Facility includes a high-intensity background field magnet system,
a cryogenic system for circulating supercritical helium through test samples,
and a remote data acquisition and computer control system.
Return to the Technology & Engineering Division home page
