Development of a Non-Local Neoclassical Transport Code for Helical Configurations

Abstract

The progress in a 3-dimensional, non-local neoclassical transport simulation code "FORTEC-3D" is described. The main purpose of the code is to solve the drift-kinetic equation in general a 3-dimensional configuration using the δ f Monte Carlo method, and to calculate neoclassical fluxes and the time evolution of the ambipolar radial electric field simultaneously. This article explains new numerical schemes adopted in FORTEC-3D in order to overcome numerical problems, which happen especially in the cases where the bifurcation of radial electric field occurs. Examples of test simulation for an LHD magnetic field configuration with a bifurcated electric field are also shown. With improved numerical schemes, FORTEC-3D can calculate neoclassical fluxes and trace the time evolution stably for several ion collision times, which is sufficiently long to observe GAM damping and formation of the ambipolar electric field.

Formation of Electron-Root Radial Electric Field and its Effect on Thermal Transport in LHD High <i>T</i>_ePlasma

“…Transport Code with Finite Orbit Width Effect, FORTEC-3D FORTEC-3D solves the drift kinetic equation based on the two-weight δ f Monte Carlo method [9][10][11]. It determines the neoclassical particle and energy fluxes by following the motion of a large number of marker particles in an arbitrary magnetic field.…”

“…In FORTEC-3D, the electron-electron collision operator satisfies the conservation laws for the particle number, momentum, and the total energy (see Ref. [11]), while the electron-ion one only involves the pitch angle scattering. The assumption that the ion distribution function is a stationary Maxwellian and its mean flow U i is negligibly small compared with the electron thermal speed, v th,e v th,i U i 0, enables FORTEC-3D to use such simplified collision operator for the electron-ion collision, where v th,e and v th,i are the electron and ion thermal velocities, respectively.…”

Benchmark test of drift-kinetic and gyrokinetic codes through neoclassical transport simulations

“…In the present paper, we report a new benchmark results of GT5D with a δ f neoclassical transport simulation code FORTEC-3D [13,14], which has been developed to solve the drift-kinetic equation including the finite-aspectratio and FOW effects both in axisymmetric tokamak and helical plasmas. Neoclassical heat transport and parallel momentum balance are checked in the same way as shown in Ref.…”

A New Simulation Method of Geodesic Acoustic Mode in Toroidal Plasmas by Using Band-Limited White Noise in a δf Neoclassical Transport Code

“…The accuracy of the conservation property has improved recently by introducing new numerical scheme for Pf M operator. 6) The time evolution of the radial electric field on each flux surface is given from the time derivative of Poisson's equation in Boozer coordinates as follows:…”

“…Recent progress in computation environment enables us to solve DKE directly and to evaluate transport coefficients more correctly. We have developed FORTEC-3D code [4][5][6][7] which is applicable to general 3-dimensional magnetic field like helical configurations of Large Helical Device (LHD) in NIFS. 8) It treats self-consistent evolution of radial electric field and the finiteorbit-width (FOW) effect of guiding-center motion, which are usually neglected in conventional methods.…”