Credit: Image courtesy of Dylan P. Brennan, Princeton University
A simulation shows (a) a disruptive instability in the DIII-D tokamak, a cross-section (b) of orbits of trapped energetic ions (black) interacting with the magnetic instability (colors), and the dependence of the critical stability threshold (c) in the ratio of thermal to magnetic energy, βc, as a function of the magnetic shear (the normalized gradient of the field’s helical pitch) in the core of the device. The critical threshold (c) is from a theoretical model that explains the simulation results and experimental observations of the mode onset.