| 1. |
- Mantsinen, M. J, et al.
(författare)
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Controlling the profile of ion-cyclotron-resonant ions in JET with the wave-induced pinch effect
- 2002
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 89:11, s. 5004-
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Tidskriftsartikel (refereegranskat)abstract
- Experiments on the JET tokamak show that the wave-induced pinch in the presence of toroidally asymmetric waves can provide a tool for controlling the profile of ion-cyclotron-resonant He-3 ions. Direct evidence for the wave-induced pinch has been obtained from the measured gamma-ray emission profiles. Concurrent differences in the excitation of Alfven eigenmodes (AEs), sawtooth stabilization, electron temperatures, and fast-ion stored energies are observed. The measured location of the AEs and gamma-ray emission profiles are consistent with the fast-ion radial gradient providing the drive for AEs.
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| 2. |
- Girardo, Jean-Baptiste, et al.
(författare)
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Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas
- 2016
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Ingår i: Physics of Plasmas. - : AMER INST PHYSICS. - 1070-664X .- 1089-7674. ; 23:1
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Tidskriftsartikel (refereegranskat)abstract
- Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfven Eigenmodes inside the q = 1 surface (also called "tornado" modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.
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| 3. |
- Hellesen, Carl, et al.
(författare)
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Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy
- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 58:5
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Tidskriftsartikel (refereegranskat)abstract
- ICRF heating at the fundamental cyclotron frequency of a hydrogen minority ion species also gives rise to a partial power absorption by deuterium ions at their second harmonic resonance. This paper studies the deuterium distributions resulting from such 2nd harmonic heating at JET using neutron emission spectroscopy data from the time of flight spectrometer TOFOR. The fast deuterium distributions are obtained over the energy range 100 keV to 2 MeV. Specifically, we study how the fast deuterium distributions vary as ICRF heating is used alone as well as in combination with NBI heating. When comparing the different heating scenarios, we observed both a difference in the shapes of the distributions as well as in their absolute level. The differences are most pronounced below 0.5 MeV. Comparisons are made with corresponding distributions calculated with the code PION. We find a good agreement between the measured distributions and those calculated with PION, both in terms of their shapes as well as their amplitudes. However, we also identified a period with signs of an inverted fast ion distribution, which showed large disagreements between the modeled and measured results. Resonant interactions with tornado modes, i.e. core localized toroidal alfven eigenmodes (TAEs), are put forward as a possible explanation for the inverted distribution.
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