Neoclassical kernel for electron cyclotron wave driven current in tokamaks

When electron cyclotron wave propagation can be treated by geometric optics, the local current drive efficiency can be expressed as an integral. A kernel for the integral that takes into account important neoclassical effects such as particle trapping and orbit modification is derived using a momentum-conserving collision operator. For absorption at the low field side of a tokamak, trapping effects reduce the efficiency significantly, while for absorption at the high field side, modification of passing particle orbits also diminishes the driven current, although to a lesser extent.