Effects of Finite-beta and Radial Electric Fields on Neoclassical Transport in the Large Helical Device

"Effects of finite-beta and radial electric fields on the neoclassical transport in the Large Helical Device are investigated with the DKES (Drift, Kinetic Equation Solver) 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 condition of temperatures and radial electric fields. When the plasma temperature is several keV, a bifurcation of the electric fields appears under the ambipolarity condition, and sufficient large radial electric fields can be generated. As a result, the E x B drift rectifies orbits of particles and improves significantly the transport coefficients in the finite-beta configuration.