Particle and energy transport simulations of reversed field pinch plasmas

Abstract

A one dimensional (1-D) computer simulation of core particle and energy transport in the reversed field pinch (RFP) is described, which models transport driven by stochastic magnetic fluctuations along with a self-consistent calculation of the neutral atom profile. Experimental plasma parameters are reproduced using fluctuation levels in the experimental range. The positive ambipolar potential, which reduces the electron particle flux to the ion rate, provides an important additional ion heating mechanism: energy is transferred from electrons to ions as they move radially along the electric field. This, combined with classical electron-ion friction and comparatively good ion energy confinement, leads to ion temperatures matching experimental values in some cases. A simple anomalous heating model is applied, however, for simulation of high Ti values in low collisionality cases. The widely observed experimental scaling βpe ∝ (I/N)-2/3 is consistent with energy loss dominated by electron heat conduction with χe ∝ Te1/2, demonstrating the universality of magnetic fluctuation induced transport in RFPs