Plasma elongation studies for iter-like tokamaks

Trade studies are performed to determine the optimum plasma elongation for a next-step tokamak such as the International Thermonuclear Experiment Reactor. Degradations of the plasma beta limit for high elongations and poloidal field coil scaling with elongation are included in the analysis. When plasma ignition is required using confinement scalings that include direct plasma current or power degradation terms, the optimum elongation is between 2.5 and 2.9, but generally the minimum-cost curve is relatively flat for elongations over 2.3. When confinement scalings that depend only on size are used or when only current drive performance is required, the optimum elongation is near 2.3. Also, when only a plasma current and neutron wall load are used as plasma performance limits, the optimum elongation is between 2.6 and 2.8, but with small cost benefits above elongations of 2.3.