BEPC-II magnet
project
Production Winding
Initial design and production testing finished, the magnet was started.
Figure 13 is the start of the first main quad layer. Note the Kapton
insulation tube over-wrap. This provides a 5 kilovolt dielectric
isolation between all the coils and the ground of the support tube. This
isolation is required for protection from voltage breakdown during a
quench. Figure 14 shows the completed layer 1. Figure 15 shows the
finished second layer.
Figure
13
Figure
14
Figure
15
Note the patterns for each layer. To expedite fabrication, the first
layer of each coil pair was designed only for transfer function, no
spacers were put into the pattern, and the wire to wire spacing was set
to the minimum allowed. All harmonic correction was done on the second
layer of the coilsets. By following this procedure, it reduced the
amount of effort required to fill the interstitial spaces on the first
layer. The second layer g-10 work could be done after the tube was
removed from the winding machine, allowing the second magnet to be wound
while the first was offline.
Figure 16 shows the completed 8 layer main quadrupole coilset with the
leads being stabilized. Figure 17 shows the 8 layer quad coldmass being
prepared for initial cold tests of the quad. The Direct Wire design
includes s-glass precompression wraps, so it is trivial to power the
individual quad package prior to completion of the entire magnet
structure, the quad is capable of withstanding cryogenic full power
operation as a standalone magnet. Testing of the 8 layer quad to beyond
full power operation proved the magnet as capable of meeting design
goals.
Figure
16
Figure
17
Figure 18 is a closeup of the first of three anti-solenoids being wound.
This is a 6 layer construct using standard MRI superconductor, a
rectangular cross section wire insulated with kapton. Figure 19 shows
the relative location of the first solenoid on the cold mass, it is
located on the non lead end. A second 6 layer anti-solenoid is located
on the tube at the lead end. After both solenoids are completed, they
are over-wrapped to bring the outer surface to that of the main quad
coils. This provides the surface for the next set of coils.
Figure
18
Figure
19
Figure 20 is the completed two layer horizontal dipole coil, shown here
after the completion of epoxy filling and curing. It was constructed
using the 6 around 1 cable.
Figure
20
Figure
21
Figure 21 is the completed vertical dipole coilset. It is shown here
just after completion of the second layer of the coilset, but prior to
the installation of the nomex filler pieces and matched epoxy.
Figure 22 is the completed skew quad coilset, this coil composed of
single strand wire. Note the varying harmonic spacers and pattern
variations which can be designed into the wiring pattern.
Figure
22
Figure
23
Figure 23 shows the final anti-solenoid being wound. Of interest here is
the four section design. By simple programming, it is possible to create
independently each block and spacer. After all blocks on one layer are
complete, the layer is filled with G-10 spacers and matched epoxy,
allowed to room temp cure, and prepped for the next layer.
After all coil winding, wrapping, and curing, the cold mass was
connected to a vertical top hat and put through all it’s operational
tests. Figure 24 is the cold mass hanging from the top hat and being
wired.
Figure
24
Test results to date show all coils exceed operational currents, in all
powered configurations required.
For more information contact
John Escallier
