Simplifying the ST and AT Concepts

As stated in a IEA Burning Plasma Workshop Review (Donne et al. in Fusion Sci Technol 49:79, 2006) “…there is not much flexibility in the fueling of ITER”. High-performance tokamak and ST plasmas greatly benefit from plasma rotation and rotation shear to increase energy confinement time and sustain high beta, made possible due to toroidal momentum injection from neutral beams. Advanced ST and AT scenarios rely on optimized density and pressure profiles that must be maintained for efficient device performance. In addition these discharges require the capability for off-axis current drive. Controlled variable-depth deep fueling that also injects toroidal momentum, in combination with the capability for off-axis current drive, would allow the AT/ST concepts to operate at close to projected performance levels. Advanced fuelling based on compact toroid injection and Electron Bernstein Wave off-axis current drive in conjunction with solenoid-free plasma start-up are proposed as methods to improve FNSF device performance and simplify the ST/AT Demo.