Excitation of Alfvén eigenmodes by fusion-born alpha-particles in D-3He plasmas on JET

Excitation of Alfvén eigenmodes by fusion-born alpha-particles in D-3He plasmas on JET

Excitation of Alfvén eigenmodes by fusion-born alpha-particles in D-3He plasmas on JET 150 150 Mathew
UKAEA-CCFE-PR(21)78

Excitation of Alfvén eigenmodes by fusion-born alpha-particles in D-3He plasmas on JET

Alfvén eigenmode (AE) instabilities driven by alpha-particles have been observed in D-3He fusion experiments on the Joint European Torus (JET) with the ITER-like wall (ILW). For the efficient generation of fusion alpha-particles from D-3He fusion reaction, the 3‑ion radio frequency (RF) scenario was used to accelerate the neutral beam injection 100-keV deuterons to higher energies in the core of mixed D-3He plasmas at high concentrations of 3He. A large variety of fast-ion driven magnetohydrodynamic (MHD) modes were observed, including the elliptical Alfvén eigenmodes (EAEs) with mode numbers n=-1 and axisymmetric modes with n=0 in the frequency range of EAEs. The simultaneous observation of these modes indicates the presence of rather strong alpha-particle population in the plasma with a “bump-on-tail” shaped velocity distribution. Linear stability analysis and Fokker-Plank calculations support the observations. Experimental evidence of the AEs excitation by fusion-born alpha-particles in the D-3He plasma is provided by neutron and gamma-ray diagnostics as well as fast-ion loss measurements. We discuss an experimental proposal for the planned full-scale D-T plasma experiments on JET based on the physics insights gained from these experiments.

Collection:
Journals
Journal:
Nuclear Fusion
Publisher:
IOP (Institute of Physics)
Published date:
10/12/2021