Experimental Observation of Magnetic Island Heteroclinic Bifurcation in Tokamaks
L. Bardóczi, T.E. Evans
Abstract
We report empirical observations of magnetic island heteroclinic bifurcation for the first time. This behavior is observed in interacting coupled 2/1 tearing modes in the core of a DIII-D tokamak plasma. Poincaré maps constrained by measured magnetic amplitudes and phasing show bifurcation from heteroclinic to homoclinic topology in the 2/1 island as the 4/2 relative amplitude (R_{4/2}) decreases. Initially, the local electron temperature peak in the 2/1 island splits, consistent with two O points. As R_{4/2} decreases a single peak forms, consistent with one O point. These call for developing tearing stability theory and control solutions for heteroclinic islands in tokamaks.
Topics & Concepts
Homoclinic orbitHeteroclinic bifurcationHeteroclinic cycleTokamakTearingPhysicsBifurcationAmplitudeHomoclinic bifurcationBifurcation theoryHeteroclinic orbitPlasmaQuantum mechanicsThermodynamicsNonlinear systemMagnetic confinement fusion researchPhysics of Superconductivity and MagnetismIonosphere and magnetosphere dynamics