Fusion Science and Technology / Volume 50 / Number 1 / July 2006 / Pages 84-88
Steady-state advanced tokamak (AT) scenarios rely on optimized density and pressure profiles to maximize the bootstrap current fraction. Under this mode of operation, the fueling system must deposit small amounts of fuel where it is needed and as often as needed, so as to compensate for fuel losses, but not to adversely alter the established density and pressure profiles. Conventional fueling methods have not demonstrated successful fueling of AT-type discharges and may be incapable of deep fueling long-pulse edge-localized-mode-free discharges in ITER. The capability to deposit fuel at any desired radial location within the tokamak would provide burn control capability through alteration of the density profile. The ability to peak the density profile would ease ignition requirements, while operating ITER with density profiles that are peaked would increase the fusion power output. An advanced fueling system should also be capable of fueling well past internal transport barriers. Compact toroid (CT) fueling has the potential to meet these needs, while simultaneously providing a source of toroidal momentum input. Experimental data needed for the design of a CT fueler for ITER could be obtained on NSTX using an existing CT injector.