Series production of ITER toroidal field coil double pancakes in Japan

National Institutes for Quantum and Radiological Science and Technology, (QST), as Japan Domestic Agency, has responsibility to procure 9 ITER Toroidal Field (TF) coils. QST completed proto double-pancake (DP) trials aiming at qualification and optimization of manufacturing procedure of TF coil in 2015. Series production of DPs then started and winding of 17 DPs, heat treatment of 16 DPs, fabrication of 15 radial plates (RP), transfer of 11 DPs and cover plate (CP) welding of 9 DPs were completed by end of Sep. 2016. Challenging tight tolerances in conductor length, ±0.01%, was achieved to enable transfer of heat-treated conductor into RP groove. 1 mm flatness was achieved in RP, whose height and width are 13 m and 9 m. In addition, about 2.5 mm flatness was achieved after CP welding by optimizing welding sequence. The DP insulation and impregnation were successfully completed on 5 DPs. The flatness of 2 mm could be achieved for all DPs completed so far and this makes DP stacking easier. These results justify that series production of TF coil DP in Japan is going well.