A fast low-to-high mode bifurcation dynamics in a tokamak edge plasma gyrokinetic simulation

TL;DR

This paper reports the first gyrokinetic simulation of edge transport barrier formation in a tokamak, showing how sheared flows and orbit loss suppress turbulence to create a barrier near the plasma edge.

Contribution

It introduces a realistic gyrokinetic simulation demonstrating the dynamics of low-to-high mode bifurcation and transport barrier formation in tokamak edge plasmas.

Findings

Transport barrier forms just inside the last closed flux surface.

Sheared ExB flows and neoclassical orbit loss suppress turbulence.

Simulation captures the bifurcation dynamics of edge plasma.

Abstract

Transport barrier formation and its relation to sheared flows in fluids and plasmas are of fundamental interest in various natural and laboratory observations and of critical importance in achieving an economical energy production in a magnetic fusion device. Here we report the first observation of an edge transport barrier formation event in a gyrokinetic simulation carried out in a realistic tokamak edge geometry. The results show that turbulent Reynolds stress driven sheared ExB flows act in concert with neoclassical orbit loss to quench turbulent transport and form a transport barrier just inside the last closed magnetic flux surface.