Electron transport fluxes valid in the region close to magnetic axis in tokamaks are derived from the moment equation approach. It is found that bootstrap current does not vanish on the axis, electrical conductivity is reduced from its classical value, and particle and heat fluxes are enhanced over those in the conventional neoclassical theory. The reason for the deviation from the conventional theory is because the fraction of the trapped particles is finite in the region close to the magnetic axis. The existence of the bootstrap current on the magnetic axis may reduce or eliminate the need of the seed current.
All Science Journal Classification (ASJC) codes