The effects of finite beta and radial electric fields on neoclassical transport in LHD are investigated with the Drift Kinetic Equation Solver (DKES) code. In the finite- beta configuration, even orbits of deeply trapped particles deviate significantly from magnetic flux surfaces. Thus, neoclassical ripple transport coefficients in the finite- beta configuration are several times larger than those in the vacuum configuration under the same conditions of temperatures and radial electric fields. When the plasma temperature is several kiloelectronvolts, a bifurcation of the electric fields appears under the ambipolarity condition. The E*B drift due to the resultant sufficiently large radial electric fields causes the orbits to curve so that they more closely follow the pressure surfaces and improves significantly the transport coefficients in the finite- beta configuration
A variational principle and its implications for radial electric field and rotation in tokamaks