The tokamak physics experiment: tokamak improvement through advanced steady state control

The achievement of a long-pulse ignited discharge with over 1000 MW of fusion power in the International Thermonuclear Experimental Reactor will be an important goal for the next phase of the world magnetic fusion program. However, improvements in the physics are needed to design a more economically attractive tokamak power reactor than the present data base would support. Advanced, steady state plasma controls are the key to realizing these improvements. The Tokamak Physics Experiment has a flexible heating and current drive system for profile control; a flexible poloidal field system that supports a strongly shaped double-null poloidal divertor plasma configuration over a wide range of profiles; and a divertor designed for dispersive operation, flexibility, and remote handling. The machine performance in deuterium is sufficient to produce a reactor-like bootstrap current profile and to confine fast electrons for localized current profile control. A conducting structure, plasma rotation, field error compensation coils, and profile control are used to provide stable plasma configurations with β up to twice the Troyon limit and bootstrap current fraction approaching unity. The facility will be designed for 1000 s pulses initially to minimize the influence of initial transients on system behavior, but the pulse length can be extended through upgrades of external systems if necessary.