Katsuhiko Tsuchiya

Development of Central Solenoid for JT-60SA

Several components for central solenoid (CS) of JT-60 Super Advanced (JT-60SA) were newly developed and tested. The butt-type joint, the electrical resistance of which is about 2 nΩ, was developed to increase the winding diameter. The insulation system, which consists of Glass/Kapton/Glass tape and Bisphenol A diglycidyl ether (DGEBA) epoxy, showed sufficient tensile strength after the irradiation of 100 kGy. Insulation characteristics of 4 × 4 winding stack sample after the compression of 705 kN 36 000 times was able to withstand voltages larger than 21 kV. The heat treatment and transfer of the CS model coil with superconductor were conducted. The pancake temperature during flat top was maintained at 923 ± 4 K. The maximum temperature difference in the pancake was 30 K. All manufacturing processes were confirmed so that the mass production of CS will be started in 2013.

Manufacture of the Winding Pack and Development of Key Parts for the JT-60SA Poloidal Field Coils

Manufacture of poloidal field (PF) coil system in JT-60SA is progressing. Recently, fabrication of the winding machines for equilibrium field (EF) coils and central solenoid (CS) were completed and the winding with the superconducting conductor was started for an EF coil (EF4). A few double pancake (DP) coils for EF4 were fabricated, and it was realized that the error of circularity for DP coils became less than the designed value. Design of the conductor end structure was also progressed. This part had the role of restraining the conductor end to prevent its separation from the winding pack. It was confirmed by the structural analysis that the conductor end structure for CS, which receives the large electromagnetic (EM) force, had sufficient mechanical strength. It was also checked by the cold test that this structure satisfied the designed performance for the electrical isolation in addition to the mechanical performance. Regarding the design of the inlet for CS, mechanical reinforcement was considered for its structure. Final design of CS inlet was determined by structural analysis to confirm the sufficient mechanical strength against the vertical compression induced by EM forces.

Design of the Precompression Mechanism and Gravity Support for the Central Solenoid Assembly in the JT-60SA Tokamak

The precompression mechanism is a key issue for central solenoid (CS) support structure. The support structure of CS assembly should act a role of withstanding the strong electromagnetic forces. The gap is not allowed between CS modules and the support structure due to the difference of their thermal expansion coefficients after cool down. The support structure should also have the precompression mechanism to cancel this gap. The support structure for CS assembly is designed considering the real procedure to set the precompression mechanism and load the required compression.

Progress of Manufacturing CS and EF Coils for the JT-60SA Tokamak

Manufacturing of the superconducting poloidal field (PF) coils in the JT-60SA tokamak is in progress. Recently, three equilibrium field (EF) coils, i.e., EF4, EF5, and EF6, intended for installation beneath the TF coils, were already completed with precision and temporarily installed on the cryostat base in the torus hall. The remaining three coils, i.e., EF1, EF2, and EF3, are being manufactured. The winding of EF1 and EF2 is completed, and stacking and connecting joints work is progressing. The pancake coil for EF3 coil will be continued to be wound until the end of this year. For the central solenoid (CS), the first module (CS1) is almost completed.