tokamak

It is called a tokamak—old Soviet shorthand for a more precise and geometrical name, toroidalnaya kamera s aksialnym magnitnym polem, or “toroidal chamber with an axial magnetic field.” Sakharov’s rough sketch depicted a doughnut-shaped vacuum chamber, or torus, ringed with electromagnets, and that is how iter’s core will look, too, once it is completed. In myriad ways, the project is a fragment of the Cold War stranded in the present day. Sakharov had predicted that a reactor base...