Effect of the Pfirsch-Schluter flow on the inboard/outboard asymmetry of the toroidal flow in LHD

Abstract

Inboard/outboard asymmetry of the toroidal flow has been observed in the large helical device (LHD), especially when the radial electric field is large. We investigate the effect of the Pfirsch-Schluter flow on the toroidal flow in LHD plasma. As a result, we find that the Pfirsch-Schluter flow can be significantly large when the electron root solution of the neoclassical ambipolarity condition is achieved with a large radial electric field. We show that the Pfirsch-Schluter flow can explain the asymmetry of toroidal flow in the electron cyclotron heating plasma and the perpendicular neutral beam injection plasma of LHD. Furthermore, we estimate the electrostatic potential from the flow asymmetry and obtain a relatively good agreement with experimental results by charge exchange recombination spectroscopy.