Electrothermal Dynamics of Cold Front in Impure Tokamak Plasmas

TL;DR

This paper investigates how radiative collapse affects current density perturbations in impure tokamak plasmas, revealing localized increases and decreases near cold fronts through reaction-diffusion modeling and simulations.

Contribution

It introduces a reaction-diffusion model to analyze current density disturbances caused by radiative collapse in impure tokamak plasmas, highlighting the role of temperature gradients and curvature.

Findings

Current density increases sharply at steep temperature gradients.

Current density decreases behind the cold front with concave-down curvature.

Electrothermal dynamics are influenced by the interplay of Ohmic heating and impurity radiation.

Abstract

Current density perturbations induced by radiative collapse, which is a possible mechanism governing tokamak plasma disruptions, have been investigated using a reaction-diffusion model. The reaction term of the current diffusion equation, which depends on the first and second radial derivatives of the electrical resistivity profile, produces a strong disturbance in the current density profile in a narrow layer of the cold front. While the current density locally increases in the region where the electron temperature gradient is steep, it decreases behind the cold front in the region where the electron temperature profile exhibits a pronounced concave-down curvature. The electrothermal dynamics driven by such a shape of the current density perturbation and the competition between Ohmic heating and impurity radiation are simulated by the tokamak transport code INDEX.