Full-$f$ gyrokinetic simulation of turbulence in a helical open-field-line plasma

TL;DR

This paper uses advanced gyrokinetic simulations to study turbulence and plasma blob behavior in a helical open-field-line plasma, revealing higher-than-expected transport levels and effects of magnetic field adjustments.

Contribution

It presents the first detailed gyrokinetic simulation of turbulence in a helical open-field-line plasma with realistic parameters from a spherical torus experiment.

Findings

Plasma blobs form and convect radially, increasing transport.

Radial particle transport exceeds Bohm estimates.

Reducing poloidal magnetic field broadens heat flux profile.

Abstract

Curvature-driven turbulence in a helical open-field-line plasma is investigated using electrostatic five-dimensional gyrokinetic continuum simulations in an all-bad-curvature helical-slab geometry. Parameters for a National Spherical Torus Experiment scrape-off-layer plasma are used in the model. The formation and convective radial transport of plasma blobs is observed, and it is shown that the radial particle-transport levels are several times higher than diffusive Bohm-transport estimates. By reducing the strength of the poloidal magnetic field, the profile of the heat flux to the divertor plate is observed to broaden.