Experimental evidence for the bootstrap current in a tokamak

The bootstrap current is a plasma current associated with trapped particles in a toroidal plasma. Magnetic measurements, such as the surface voltage, the internal inductance, and the Faraday rotation, are consistent with the existence of the neoclassical bootstrap current in tokamaks. The neoclassical trapped-particle correction to the electrical conductivity is also systematically validated against experiments. These results support the assertion that the generalized Ohm's law dong the magnetic field is valid, as predicted by the neoclassical transport theory, while the perpendicular transport deviates from the neoclassical transport theory.