The magnet structures of the KSTAR device consist of a sixteensegment Toroidal Field (TF) coil structure, a Central Solenoid (CS) structure, modular Poloidal Field (PF) coil structures, and a gravity support. The function of the structures is to protect superconducting coils from mechanical, electrical and thermal loads. Since most of the magnet structures are cooled by supercritical helium at 4.5 K, strengthened stainless steel is chosen as the basic material.

The TF coil structure is divided into sixteen segments in order to reduce the eddy current heating. Each section consists of a case enclosing a D-shaped TF coil, intercoil structures, a joint box and basements of PF coils. These substructures are firmly connected to resist huge magnetic force using keystone- shaped cases, shear keys and bolts. The CS coil structure consists of the preload structures that apply compression to the CS coils and interface structures that support the CS magnet on the TF structure. The PF coil structures and gravity supports are designed with flexible plates and hinged pin connections to allow flexibility in the radial direction.

For the engineering design of the magnet structures, the structural and thermo-hydraulic analyses were conducted by the Hyundai Electro-Mechanical Research Institute, the Maritime Research Institute and the Industrial Research Institute. The Industrial Plant & Engineering Division produced fabrication drawings, technical specifications, and fabrication and assembly procedures.

To verify the engineering design and to develop the manufacturing technologies, one segment of the TF structure has been successfully manufactured as a prototype. HHI has already finished the design of the main components of the tokamak for the KSTAR, and plans to complete the production of the vacuum vessel and the cryostat by April 2004.