The Influence of Physics Parameters on Tokamak Reactor Design

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Abstract
Twelve important tokamak reactor parameters were surveyed, and the results of sensitivity studies serve as a guide for reactor design. Numerous magnetohydrodynamic equilibria are studied to determine influences of geometry, pressure profile, safety factor, and beta on the plasma current. A steady-state transport model, which averages particle and power balances in flux space, reveals the effects of temperature and density profiles, impurities, and temperature on power density and n̄i τ. The blanket/shield thickness, major radius, and magnetic field are likewise shown to influence reactor performance. For a fixed beta and reactor power, the design is quite insensitive to the relative contributions of density and temperature profiles to the total pressure over a wide range of profile widths, whereas the current generally increases for more D-shaped plasmas. If beta increases significantly at low aspect ratio or high elongation, reactor size can decrease; for the scaling laws βt = 0.21 A−1 and βt = 0.05 k, the plasma current may increase prohibitively for A ≲ 3.0 and k ≳ 2.0. Significant improvements occur at large power levels; typically, power output doubles with 15 to 20% increases in major radius and current.