The mission of the Tokamak Physics Experiment (TPX) [Nevins et al., Plasma Physics and Controlled Nuclear Fusion, Würzburg (International Atomic Energy Agency, Vienna, 1992), Vol. 3, p. 279] is to develop the scientific basis for an economically competitive and continuously operating tokamak fusion power source. This complements the primary mission of the International Thermonuclear Experimental Reactor (ITER) [ITER Document Ser. No. 18 (International Atomic Energy Agency, Vienna, 1991)], the demonstration of ignition and long-pulse burn, and the integration of nuclear technologies. The TPX program is focused on making the demonstration power plant that follows ITER as compact and attractive as possible, and on permitting ITER to achieve its ultimate goal of steady-state operation. This mission of TPX requires the development of steady-state regimes with high beta, good confinement, and a high fraction of a self-driven bootstrap current. These regimes must be compatible with plasma stability, strong heat-flux dispersion in the divertor region, and effective particle control.