First Results From Simulations of Rapid Shutdown With Neon Deposition in J-TEXT Rotating Plasmas

Abstract

Encapsulated payload pellet injection (EPPI) has been demonstrated to be an effective method of disruption mitigation system (DMS) through a number of experiments and simulations in DIII-D and JET. This article investigates the effects of plasma rotation on impurity spreading under neon EPPI. Our analysis of simulations shows that the magnetic surface stochastization has a decisive influence on the core-oriented spread of impurity. The MHD instabilities increase with impurity ionization, especially of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n = 1$ </tex-math></inline-formula> component, leading to the enhancement of the local transport of impurities along the stochastic field lines. In the rotating plasma, the toroidal rotation can suppress the magnetic perturbation, and then, the boundary-oriented spreading of impurities is reduced. When the pellet source is toroidally localized at the magnetic axis, the rotation can quickly flatten the toroidal distribution of impurities, resulting in a smaller maximum radiated power and a lower toroidal peek factor (TPF).