One dimensional reduced model for ITER relevant energetic particle transport

TL;DR

This paper develops a one-dimensional model to simulate energetic particle transport in ITER, capturing non-linear effects like avalanches and improving upon traditional diffusive models.

Contribution

A novel mapping technique translating 3D fast ion dynamics into a 1D bump-on-tail system, enabling accurate non-linear predictions relevant for ITER.

Findings

The 1D model reproduces key features of non-linear hybrid simulations.

Deviations from quasi-linear models are attributed to avalanche processes.

The approach highlights critical aspects for predicting fluxes in tokamaks.

Abstract

We set up a mapping procedure able to translate the evolution of the radial profile of fast ions, interacting with Toroidal Alfv\'en Eigenmodes, into the dynamics of an equivalent one dimensional bump-on-tail system. We apply this mapping technique to reproduce ITER relevant simulations, which clearly outlined deviations from the diffusive quasi-linear (QL) model. Our analysis demonstrates the capability of the one-dimensional beam-plasma dynamics to predict the relevant features of the non-linear hybrid LIGKA/HAGIS simulations. In particular, we clearly identify how the deviation from the QL evolutive profiles is due to the presence of avalanche processes. A detailed analysis regarding the reduced dimensionality is also addressed, by means of phase-space slicing based on constants of motion. In the conclusions, we outline the main criticalities and outcomes of the procedure, which must be satisfactorily addressed to make quantitative prediction on the observed outgoing fluxes in a Tokamak device.