The Advanced Tokamak

Abstract

We disagree with Alexander J. Glass's assertion (Letters, 19 June, p. [1817][1]) that the tokamak must be as large as the International Thermonuclear Experimental Reactor (ITER) to achieve sustained thermonuclear burn and that this does not bode well for the tokamak as a potential power-plant concept. In fact, recent advances worldwide indicate that smaller tokamak power plants should be feasible. In current, few-second experiments, heat transport within the plasma has been reduced by suppressing turbulence, plasma pressure limits have been increased, the potential for steady-state operation by naturally driven currents has been demonstrated, and concerns about handling exhaust heat have been mitigated. Integrating and extending these advances toward steady state is now a focus of international tokamak research. With such advanced tokamak physics, a smaller ITER, now being pursued internationally, would likely produce sustained plasma burn, and the tokamak power plant of the future becomes much more attractive. After several decades of intensively competitive research on a broad range of magnetic fusion concepts, the tokamak emerged and matured into the only concept that is ready to produce the plasma conditions required to explore the next fusion science frontier, the physics of sustained burning plasmas. This is not to say that other concepts should not be investigated. On the contrary, they should be pursued to further optimize fusion power systems; physics understanding is transferable both ways. Our conclusion is that a strong experimental and computational tokamak research program with a healthy alternative concept program is the optimum fusion research strategy. We strongly support the international construction of a tokamak burning plasma experiment as soon as possible. Fusion research is ready to enter the burning plasma era. [1]: /lookup/doi/10.1126/science.280.5371.1815d