(FT/2-4) Engineering Aspects of Compact Stellarators

**Abstract.** Compact stellarators could combine the good confinement and high
beta of a tokamak with the inherently steady-state, disruption-free
characteristics of a stellarator. Two U.S. compact stellarator facilities
are now in the conceptual design phase: the National Compact Stellarator
Experiment, NCSX, and the Quasi-Poloidal Stellarator, QPS. NCSX has a major
radius of 1.4 m and a toroidal field up to 2 T. The primary feature of NCSX
is the set of modular coils that provide the basic magnetic configuration.
These coils represent a major engineering challenge due to the complex
shape, precise geometric accuracy and high current density of the windings.
The winding geometry is too complex for conventional hollow copper conductor
construction. Instead, the NCSX coils will be wound with flexible,
multi-strand cable conductor that has been compacted to a 75% copper
packing fraction. Inside the coil set and surrounding the plasma is a
highly contoured vacuum vessel. The QPS device has a major radius of 0.9 m,
a toroidal field of 1 T, and an aspect ratio of only 2.7. Instead of an
internal vacuum vessel, the QPS modular coils will operate in a bell jar.

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*IAEA 2003*