Plasma rotation from momentum transport by neutrals in tokamaks

TL;DR

This paper develops a framework to analyze how neutral atoms influence plasma rotation and electric fields in tokamaks, highlighting the importance of neutral localization and plasma collisionality.

Contribution

It introduces a new kinetic model to study neutral-driven momentum transport in tokamaks, enabling exploration of parameter effects on plasma rotation.

Findings

Neutral localization significantly affects toroidal rotation.

Plasma collisionality impacts the electric field and rotation.

Adjusting neutral position can control plasma rotation.

Abstract

Neutral atoms can strongly influence the intrinsic rotation and radial electric field at the tokamak edge. Here, we present a framework to investigate these effects when the neutrals dominate the momentum transport. We explore the parameter space numerically, using highly flexible model geometries and a state of the art kinetic solver. We find that the most important parameters controlling the toroidal rotation and electric field are the major radius where the neutrals are localized and the plasma collisionality. This offers a means to influence the rotation and electric field by, for example, varying the radial position of the X-point to change the major radius of the neutral peak.