Speaker
Description
Authors: V.G.Kiptily, Ye.Kazakov, M.Nocente, M.Fitzgerald, S.E.Sharapov, A.E.Shevelev, and JET Contributors
Excitation of Elliptical AEs (EAEs) and TAEs has been observed in hydrogen-rich (nH/nH+nD ~70-90%) JET discharges of so-called “three-ion scenario”, i.e.D-(3He)-H three ion ICRH scenario [1]. This scenario is characterized by a strong absorption of radio frequency waves at very low concentrations of the resonant 3He-ions. In the experiments, core localized TAEs with frequency f_TAE≈ 280 kHz were observed. Following the phase with the TAE excitation, EAEs at higher frequencies, f_EAE≈ 550-580 kHz, and with mode numbers n=±1, ±3, ±5 were seen. These high frequency modes indicate that a MeV range population of trapped energetic ions was present in the plasma interacting with the modes via the trapped particle resonances. The experimental evidence of the existence of the MeV-energy 3He-ions able to excite the AEs is provided by neutron and gamma-ray diagnostics as well as fast ion loss (FILD) measurements. It was found that the anomalous DD neutron rate in the ICRF-only heated plasma is provided by population of energetic deuterons formed via elastic head-on scattering of the MeV 3He-ions on deuterium (the knock-on effect): D(3He,3He)D knock-on=> D(D_knock-on,n)3He. Gamma-ray diagnostics [2] show that some neutrons are also generated in the nuclear reaction 9Be(3He,n)11C, which takes place with 3He-ions in the MeV-range. The fast ion loss detector [3] indicates that the MeV-range 3He-ion losses related to the core localized TAEs ended with a spike associated with a monster sawtooth, after which the losses correlated to the EAE modes were observed. Analysis of FILD data indicates that the lost 3He-ion energies exceed 2 MeV. The back-in-time orbit analysis of the FILD data shows that the TAE-induced losses of 3He-ions are localised in the plasma centre (R≈3.0 m). However, the losses of 3He-ions associated with the EAEs are coming from R≈3.2-3.4 m. Results of MHD analysis are consistent with the experimental data showing that the MeV 3He ions are resonant when interacting with TAEs and EAEs.
References
[1] Ye.O. Kazakov, D. Van Eester, R. Dumont and J. Ongena, Nucl. Fusion 55 (2015) 032001;
[2] V.G. Kiptily, F.E. Cecil and S.S. Medley, Plasma Phys. Control. Fusion 48 (2006) R59;
[3] D. Darrow et al. Rev. Sci. Instrum. 77 (2006) 10E701.
| Country or International Organization | United Kingdom |
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