Ion cyclotron emission from fusion-born ions in large tokamak plasmas: a brief review from JET and TFTR to ITER

TL;DR

This review discusses ion cyclotron emission (ICE) driven by fusion-born ions in large tokamaks, highlighting its diagnostic potential, underlying mechanisms, and recent advances from JET and TFTR to ITER.

Contribution

It provides a comprehensive overview of ICE phenomena, mechanisms, and recent progress in understanding and modeling, emphasizing its importance for future fusion diagnostics.

Findings

ICE intensity scales linearly with fusion reactivity in JET.

ICE serves as an indicator of fast ion physics in large tokamaks.

Recent computational advances have improved understanding of the magnetoacoustic cyclotron instability.

Abstract

Ion cyclotron emission (ICE) was the first collective radiative instability, driven by confined fusion-born ions, observed from deuterium-tritium plasmas in JET and TFTR. ICE comprises strongly suprathermal emission, which has spectral peaks at multiple ion cyclotron harmonic frequencies as evaluated at the outer mid-plane edge of tokamak plasmas. The measured intensity of ICE spectral peaks scaled linearly with measured fusion reactivity in JET. In other large tokamak plasmas, ICE is currently used as an indicator of fast ions physics. The excitation mechanism for ICE is the magnetoacoustic cyclotron instability (MCI); in the case of JET and TFTR, the MCI is driven by a set of centrally born fusion products, lying just inside the trapped-passing boundary in velocity space, whose drift orbits make large radial excursions to the outer mid-plane edge. Diagnostic exploitation of ICE in future experiments therefore rests in part on deep understanding of the MCI, and recent advances in computational plasma physics have led to substantial recent progress, reviewed here.