Superstructure for a super tokamak: Alcator C-MOD

The ALCATOR C-MOD, a compact, high-performance tokamak presently being constructed by the Massachusetts Institute of Technology under contract to the US Department of Energy, is described. The purpose of the program is to study the production, confinement, heating, and control of strongly shaped, fully diverted, high-density plasmas. The high-toroidal magnetic field produces extremely large forces on the magnet conductors. Those loads are reacted by an external superstructure. The machine will be operated in a pulsed mode, with a design life of 50,000 cycles. That combination places exceptional requirements on the design, materials processing, and fabrication of the superstructure components. The superstructure consists of a large forged AISI 316LN pressure vessel that is assembled with alloy 718 fasteners. The chemistries and thermomechanical processing techniques were selected to provide the necessary mechanical properties at both room temperature and at the 77 K operating temperature. The superstructure design, stress analysis, materials processing, static and fatigue properties, components fabrication, and inspection are addressed.