R&D Of Polyimide Insulated Jet ELM Control Coils For Operation At 350 C
Authors: I.J. Zatz, G.H. Neilson, S. Jurczynski, M. Mardenfeld and C. Lowry
Abstract:
A study has confirmed the feasibility of designing,
fabricating and installing resonant magnetic field perturbation
(RMP) coils in JET with the objective of controlling edge
localized modes (ELM). These coils present several engineering
challenges. Conditions in JET necessitate the installation of these
coils via remote handling, which will impose weight, dimensional
and logistical limitations. And while the encased coils are
designed to be conventionally wound and bonded, they will not
have the usual benefit of active cooling. Accordingly, coil
temperatures are expected to reach 350C during bakeout as well
as during plasma operations from resistive heating. These
elevated temperatures are beyond the safe operating limits of
conventional OFHC copper and the epoxies that bond and
insulate the turns of typical coils. This has necessitated the use of
an alternative copper alloy conductor C18150 (CuCrZr). More
importantly, an alternative to epoxy had to be found. An R&D
program was initiated to find the best available insulating and
bonding material. The search included polyimides and ceramic
polymers. Ultimately, these ELM coils must be able to withstand
the elevated thermal conditions as well as the structural stresses
resulting from electromagnetic loads, which include eddy current
and halo current effects. Not only do these loads affect the
performance of the coils and cases, but also impact the design of
joints, leads, jumpers, and the mounting of the coils to the
interior of the vacuum vessel wall. In order to qualify the
proposed insulating and bonding materials, prototypical coil
samples were built to the design specifications of the proposed
JET ELM coils. These samples were impregnated with polyimide
then cured. This paper will detail the R&D program, including
the results of testing to determine mechanical properties of the
polyimide bonded coil samples.
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Submitted to: 38th International Conference on Plasma Science & 24th Symposium on Fusion Engineering/ICOPS 2011 SOFE, Chicago, IL, June 26-30, 2011
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