Tokamak
A toroidal magnetic confinement fusion device that utilizes external magnetic coils and an internal driven plasma current to create a helical magnetic field.
Governing formula
q = (r B_toroidal) / (R B_poloidal)
SI unit
Dimensionless Safety Factor q
In depth
Pioneered in USSR by Igor Tamm and Andrei Sakharov. Toroidal field coils supply the strong circumferential magnetic field, while a central transformer induces an internal toroidal plasma current, generating a poloidal magnetic field to create stable twisted magnetic surfaces.
Examples in the real world
The ITER experimental fusion reactor under construction in France, designed to achieve Q ≥ 10 energy gain.