Reduction of the chaotic transport of impurities in turbulent magnetized plasmas

TL;DR

This paper explores how small modifications to the Hamiltonian can create barriers in phase space, significantly reducing impurity transport in turbulent magnetized plasmas, which is crucial for improving plasma confinement.

Contribution

It introduces a Hamiltonian-based method to reduce chaotic impurity transport by constructing phase space barriers through minimal Hamiltonian modifications.

Findings

Numerical simulations show drastic reduction in impurity diffusion.

Small Hamiltonian perturbations effectively create transport barriers.

The method demonstrates robustness under various conditions.

Abstract

The chaotic transport of charged particles in a turbulent electrostatic potential sets the conditions of a severe limitation to the plasma confinement in devices such as tokamaks. In this chapter, we consider the motion of impurities driven by the ExB velocity where a strong magnetic field B (which allows for the guiding center approximation) is uniform and constant, and a turbulent electric field is obtained from models or from numerical fluid codes. Hamiltonian dynamics rule the transport properties of these impurities. Therefore a technique to reduce chaotic diffusion in Hamiltonian systems is able to address the issue of reducing the radial transport of impurities under some approximations. The general idea is to build barriers in phase space by a small and apt modification of the Hamiltonian. We show numerically that such perturbations are able to drastically reduce the diffusion of test-particles, and we discuss the robustness of such additional modifications.