Global linear and nonlinear gyrokinetic modelling of Alfv\'en eigenmodes in ITER

TL;DR

This paper presents comprehensive linear and nonlinear gyrokinetic simulations of Alfvén eigenmodes in ITER, revealing mode behaviors, damping, and potential energetic particle redistribution at high EP densities.

Contribution

It introduces a global nonlinear electromagnetic gyrokinetic model for ITER Alfvén eigenmodes, highlighting mode excitation, damping, and nonlinear saturation effects.

Findings

Low damping of elliptic and odd-parity TAEs

Global nature of low mode number TAEs

Potential for significant EP redistribution at high EP densities

Abstract

Linear and nonlinear modelling of Alfv\'enic instabilities, most notably toroidal Alfv\'en eigenmodes (TAEs), obtained by using the global nonlinear electromagnetic gyrokinetic model of the code ORB5 are presented for the 15 MA scenario of the ITER tokamak. Linear simulations show that elliptic Alfv\'en eigenmodes and odd-parity TAEs are only weakly damped but not excited by alpha particles, whose drive favours even-parity TAEs. Low mode number TAEs are found to be global, requiring global treatment. Nonlinearly, even with double the nominal EP density, single mode simulations lead to saturation with negligible EP transport however multi-mode simulations predict that with double the nominal EP density, enhanced saturation and significant EP redistribution will occur.