21st IEEE/NPSS Symposium on Fusion Engineering (SOFE) September 26-30, 2005 Knoxville, TN U.S. Department of Energy Contract DE-AC02-76-CHO-3073.

1
NCSX TOROIDAL FIELD COIL DESIGN
M. KALISH, L. MYATT, J. RUSHINSKI, A. BROOKS, F.
DAHLGREN, J. CHRZANOWSKI, W. REIERSEN AND
K.FREUDENBERG

• Coil with composite properties provides results
  which determine the worst case operating
  conditions

• Electromagnetic-Structural model includes all
  field sources and structures. Used to evaluate
  coarse reaction of TF Coils to various operating
  scenarios

TF Coils react radial loads by wedging with
adjacent coils. Radial studs at the top and
bottom of the stainless steel wedge castings lock
the TF Coils in place and react any outward
forces.

• A more detailed model which meshes the individual
  conductors and insulation as well as the wedge
  casting provides final results.

Original design used continuous conductor bent
away from winding pack for leads. Finite element
analysis revealed that design was inadequate for
reacting the opposing electromagnetic loads
experienced by the leads.
The final design uses lead blocks cut from copper
plate. The increased cross section reduces
bending stresses substantially. Note that the use
of a Kapton slip plane results in the requirement
that the leads be restrained by some other means
than just the shear strength of the glass epoxy.
Analysis
Design and Analysis (Lead Spur)
The lead blocks are locked in place by G11
fillers designed to carry opposing shear loads
from lead to lead. To make assembly possible
multiple interlocked and pinned blocks are
required
Wedge Castings Assembled to TF Coil
TF Coil Assembly
Analysis verifies that coil stiffness is adequate
after releasing insulation from conductors.
Prototype bar fabricated to verify analysis and
test for endurance
Lead Spur
½ lap layer of Kapton applied directly to
conductor added as a release plane resolves
thermal contraction issues
Analysis of all glass insulation scheme showed
risk of insulation cracking due to thermal
stresses
Coils are constrained vertically both top and
bottom by cross beams. Outward radial growth is
unrestrained
Coils are constrained toroidally by purple
castings. Jack screws provide adjustment.
Insulation Development
Cross section of winding pack with wedge casting.
Consists of LN2 cooled solid copper conductors
arranged 3x4. Groundwrap is .12 thick at front
and .38 thick elsewhere.
Three coil assembly shown wedged forward reacting
radial loads
Prototype bar with design insulation scheme and
winding pack analyzed to predict performance
during testing
Prototype bar installed in test fixture at Oak
Ridge Nat. Lab.
Test fixture cycles prototype at LN2 temperatures
for fatigue testing
Plot of load versus deflection before and after
cycling the prototype bar shows negligible change
to the mechanical characteristics. Subsequent
electrical testing showed no degradation to the
dielectric strength of the insulation. Elastic
modulus of the bar is verified to be within the
predicted range.
Testing Verifies Analysis and Reliability
Coil vacuum impregnated in mold and cured in
autoclave shown above
TF coil to be fabricated at Princeton Plasma
Physics Lab
Fabrication
Three Coil TF Assembly With Support Structure
Three Coil Assembly Rotated over Modular Coils
and Vacuum Vessel
21st IEEE/NPSS Symposium on Fusion Engineering
(SOFE) September 26-30, 2005 Knoxville, TN
U.S. Department of Energy Contract
DE-AC02-76-CHO-3073.