Momentum injection in tokamak plasmas and transitions to reduced transport

TL;DR

This paper investigates how momentum injection influences temperature gradients in tokamak plasmas, proposing a scenario where optimal momentum input induces transitions to reduced transport regimes by suppressing turbulence, especially in low magnetic shear regions.

Contribution

It introduces a plausible scenario for transitions to reduced transport regimes driven by momentum injection and identifies the optimal level of momentum input for turbulence suppression.

Findings

Optimal momentum injection reduces turbulence and transport.

Reduced transport is maximized in low or zero magnetic shear regions.

Excessive velocity shear can rekindle turbulence.

Abstract

The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.