Synopsis:The manufacturing process for ITER toroidal field (TF) coils must be demonstrated as effective in order to meet the criteria for qualification. Since impregnation of the insulation system is one criterion for qualification in this study, we performed impregnation tests using a cyanate-ester/epoxy blended resin, chosen for its excellent resistance to radiation. To establish the insulation and impregnation procedure in the TF coil manufacturing process, three types of trials were performed: 1) impregnation tests using an acrylic model to fix the impregnation conditions; 2) an impregnation test using a metallic model to confirm that no void remains in the insulation layer after curing in the D-shaped configuration; and 3) insulation and impregnation trials using a 1/3-scale double-pancake (DP) model. The results of these trials were used to determine the insulation and impregnation procedures for manufacturing ITER TF coils.
This paper reports improvement of the coercivity of Nd-Fe-B powder by Nd-Cu sputtering. The total rare earth element content of the Nd-Fe-B powder increased by 0.8 mass% after Nd-Cu sputtering, and the sputtered Nd-Cu was observed at the surface of Nd-Fe-B powder by microstructural observation. The coercivity (H c ) of the Nd-Cu-sputtered Nd-Fe-B powder improved after annealing at temperatures above 600 C, and H c of the sputtered powder reached a maximum value of 1312 kA m −1 after annealing at 900 C. This H c value was 470 kA m higher than that of the compact prepared from powder without sputtering after annealing at 900 C. Microstructure observation showed that the improvement of H c was due to an increase in the Nd-rich phase in the compact by Nd-Cu sputtering.
The authors performed one-third scale trials of the conductor winding, the heat treatment and the insulation/impregnation to demonstrate and optimize fabrication procedure of TF coil. In this trial, accuracy of conductor length measurement system was confirmed in the winding trial. The conductor elongation and winding deformation due to the heat treatment were evaluated in the heat treatment trial. And the procedure of insulation and impregnation was established through the insulation/impregnation trial, and the insulation condition was fixed.
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