A walk in the parameter space of L-H transitions without stepping on or through the cracks

TL;DR

This paper introduces a mathematically rigorous three-degree-of-freedom dynamical model for L-H transitions in plasma physics, revealing complex bifurcation structures that inform control strategies for confinement regimes.

Contribution

It develops a novel, physically consistent model based on singularity theory, identifying key bifurcations and organizing centers that explain observed L-H transition behaviors.

Findings

Identification of two codimension 2 organizing centers.

Discovery of two Hopf bifurcations influencing L-H transitions.

Provision of qualitative guidelines for controlling plasma confinement regimes.

Abstract

A mathematically and physically sound three-degree-of-freedom dynamical model that emulates low- to high-confinement mode (L--H) transitions is elicited from a singularity theory critique of earlier fragile models. We construct a smooth map of the parameter space that is consistent both with the requirements of singularity theory and with the physics of the process. The model is found to contain two codimension 2 organizing centers and two Hopf bifurcations, which underlie dynamical behavior that has been observed around L-H transitions but not mirrored in previous models. The smooth traversal of parameter space provided by this analysis gives qualitative guidelines for controlling access to H-mode and oscillatory regimes.