EXTENDED NEOCLASSICAL TRANSPORT-THEORY FOR INCOMPRESSIBLE TOKAMAK PLASMAS

Conventional neoclassical transport theory is extended to include the effects of orbit squeezing, and to allow the effective poloidal Mach n umber U-pM = [(V parallel to/u(t)) + (VEB/u(t)B(p))] of the order of u nity for incompressible tokamak plasmas. Here, V parallel to is the pa rallel mass flow, u(t) is the ion thermal speed, V-E is the poloidal E xB drift speed, B is the magnetic field strength, and B-p is the poloi dal magnetic field strength. It is found that ion thermal conductivity is reduced from its conventional neoclassical value in both banana an d plateau regimes if U-pM>1 and S>1. Here, S=[1+cI(2) Phi ''/(Omega(0) B(0))] is the orbit squeezing factor with c the speed of light, I=RBt, R the major radius, Phi the electrostatic potential, B-0 the magnetic field strength on the axis, Omega(0)=eB(0)/Mc, M the ion mass, e the ion charge, Omega ''=d(2) Phi/d psi(2), and psi the poloidal flux func tion. However, there is an irreducible minimum for the ion thermal con ductivity in the banana-plateau regime set by the conventional Pfirsch -Schluter transport. (C) 1997 American Institute of Physics.