Abstract
Small steady-state tokamaks for testing divertors and fusion nuclear technologies are considered. Based on present physics and technology data and extrapolation to reduced R0/a, H-D-fueled tokamaks with R0 approximately 0.6-0.75 m, R0/a approximately 1.8-2.5, and B(t0) approximately 1.4-2.2 T can be driven with P(tot) approximately 4.5 MW to maintain I(p) approximately 0.5 MA and produce the ITER-level plasma edge and divertor conditions. Given an adequate steady-state divertor solution and Q approximately 1 operation based on fusion through the suprathermal component, D-T-fueled tokamaks with R0 approximately 0.8 m, R0/a approximately 2, and B(t0) approximately 4 T can be driven with P(tot) approximately 15 MW to maintain I(p) approximately 4.6 MA and produce a peak neutron wall load W(L) approximately 1 MW/m2. Such devices appear possible if the plasma properties at the lower R0/a remain tokamak-like and, for the D-T case, an unshielded center core is feasible. The use of a single conductor as the inboard leg of the toroidal field coils for this purpose is discussed. The physics issues and the design features are identified for such tokamaks with a testing duty factor goal of 10-20%.
