Scenario development for the observation of alpha-driven instabilities in JET DT plasmas

Abstract

In DT plasmas, Toroidal Alfvén Eigenmodes (TAEs) can be made unstable by the alpha particles resulting from fusion reactions, and may induce a significant redistribution of fast ions. Recent experiments have been conducted in JET deuterium plasmas in order to prepare scenarios aimed at observing alpha-driven TAEs in a future JET DT campaign. Discharges at low density, large core temperatures associated with the presence of Internal Transport Barriers and characterised by good energetic ion confinement have been performed. ICRH has been used in the hydrogen minority heating regime to probe the TAE stability. The consequent presence of MeV ions has resulted in the observation of TAEs in many instances. The impact of several ‡ See the author list of "X. Litaudon et al 2017 Nucl. Fusion 57 102001" Scenario development for the observation of alpha-driven instabilities in JET DT plasmas2 key parameters on TAE stability could therefore be studied experimentally. Modeling taking into account NBI and ICRH fast ions shows good agreement with the measured neutron rates, and has allowed predictions for DT plasmas to be performed.

Experimental studies of plasma-antenna coupling with the JET Alfvén Eigenmode Active Diagnostic

“…This could have been avoided by increasing the plasma elongation; however, that could have affected PA coupling (and general plasma performance) in turn. This presents an interesting optimization problem, the solution to which will be pursued in upcoming JET EP experiments [41] in preparation for the DT campaign.…”

Generation and observation of fast deuterium ions and fusion-born alpha particles in JET $\mathrm{D-^3He}$ plasmas with the 3-ion radio-frequency heating scenario

“…Although a number of aspects of alpha particle physics can only be studied in burning plasmas, some can be anticipated in present machines. To this end, the Joint European Torus (JET) has established an ambitious scientific program in preparation of its future deuterium-tritium (DTE2) campaign, aiming, among others, at developing dedicated scenarios where the effects of alpha particles from the fusion reactions can be studied [1,2]. One possibility is offered by the 3-ion radio-frequency (RF) heating scenario [3,4] in D-T plasmas, by accelerating tritons or deuterons from neutral beam injection (NBI) to high enough energies that maximize the D-T reactivity [5] at moderate input auxiliary heating power.…”

Gyrokinetic simulations of toroidal Alfvén eigenmodes excited by energetic ions and external antennas on the Joint European Torus

“…In order to explore and quantify the phenomenon of TAEs at JET since the installation of the fully-metal ITER-like wall, discharges have been tailored to their observation 8 . In particular, deuterium composition experiments were undertaken with the aim of developing a scenario for clear observation of α-driven TAEs in future DT experiments.…”