Caractérisation des coulées de magma à travers des débris lors d'une transitoire accidentel (Thèse 2019-2022)
Activités
Publications scientifiques au M2P2
2017
W.A. Gracias, P. Tamain, Eric Serre, R.A. Pitts, L. Garcia. The impact of magnetic shear on the dynamics of a seeded 3D filament in slab geometry. Nuclear Materials and Energy, 2017, 12, pp.798 - 807. ⟨10.1016/j.nme.2017.02.022⟩. ⟨hal-01702187⟩ Plus de détails...
Seeded filament simulations are used to study blob dynamics with the state-of-the-art TOKAM3X fluid code in the scrape-off layer (SOL) using a slab geometry. The filamentary dynamics recovered with the code are compared with previously predicted analytical blob velocity scalings while also studying the effect of field line pitch angle on these dynamics and are found to be similar. The effect of changing magnetic topology on filamentary motion is also investigated. Magnetic shear is introduced in the model by the sudden and localised variation of field line pitch angle for a narrow radially located region constituting effectively a shearing zone. Three such shear zones are tested to see how they affect filament motion. Filaments are initialised radially upstream from the shear zone and recorded as they convect towards the far-SOL side. The lowest intensity shear zone allows many of the higher amplitude filaments to pass through after dampening them. On the other hand, the highest intensity shear zones prevent all filaments from progressing to the wall beyond the shear zone and, in certain cases for high density amplitude filaments, is able to generate a new filament downstream from the shear zone.
W.A. Gracias, P. Tamain, Eric Serre, R.A. Pitts, L. Garcia. The impact of magnetic shear on the dynamics of a seeded 3D filament in slab geometry. Nuclear Materials and Energy, 2017, 12, pp.798 - 807. ⟨10.1016/j.nme.2017.02.022⟩. ⟨hal-01702187⟩
O. Kazakov, J. Ongena, E. Lerche, M. Mantsinen, D. Van eester, et al.. Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating. Nature Physics, 2017, 13 (10), pp.973-978. ⟨10.1038/NPHYS4167⟩. ⟨cea-01898634⟩ Plus de détails...
We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of $^3$He ions to high energies in dedicated hydrogen–deuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast $^3$He ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, $^3$He-rich solar flares.
O. Kazakov, J. Ongena, E. Lerche, M. Mantsinen, D. Van eester, et al.. Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating. Nature Physics, 2017, 13 (10), pp.973-978. ⟨10.1038/NPHYS4167⟩. ⟨cea-01898634⟩
B. Saoutic, N. Dumas, Rémi Dumont, A. Durocher, F. X. Duthoit, et al.. Contribution of Tore Supra in preparation of ITER. Nuclear Fusion, IOP Publishing, 2011, 51 (9, SI), ⟨10.1088/0029-5515/51/9/094014⟩. ⟨hal-01460107⟩ Plus de détails...
Tore Supra routinely addresses the physics and technology of very long-duration plasma discharges, thus bringing precious information on critical issues of long pulse operation of ITER. A new ITER relevant lower hybrid current drive (LHCD) launcher has allowed coupling to the plasma a power level of 2.7 MW for 78 s, corresponding to a power density close to the design value foreseen for an ITER LHCD system. In accordance with the expectations, long distance (10 cm) power coupling has been obtained. Successive stationary states of the plasma current pro le have been controlled in real-time featuring (i) control of sawteeth with varying plasma parameters, (ii) obtaining and sustaining a `hot core' plasma regime, (iii) recovery from a voluntarily triggered deleterious magnetohydrodynamic regime. The scrape-off layer (SOL) parameters and power deposition have been documented during L-mode ramp-up phase, a crucial point for ITER before the X-point formation. Disruption mitigation studies have been conducted with massive gas injection, evidencing the difference between He and Ar and the possible role of the q = 2 surface in limiting the gas penetration. ICRF assisted wall conditioning in the presence of magnetic eld has been investigated, culminating in the demonstration that this conditioning scheme allows one to recover normal operation after disruptions. The effect of the magnetic eld ripple on the intrinsic plasma rotation has been studied, showing the competition between turbulent transport processes and ripple toroidal friction. During dedicated dimensionless experiments, the effect of varying the collisionality on turbulence wavenumber spectra has been documented, giving new insight into the turbulence mechanism. Turbulence measurements have also allowed quantitatively comparing experimental results with predictions by 5D gyrokinetic codes: numerical results simultaneously match the magnitude of effective heat diffusivity, rms values of density uctuations and wavenumber spectra. A clear correlation between electron temperature gradient and impurity transport in the very core of the plasma has been observed, strongly suggesting the existence of a threshold above which transport is dominated by turbulent electron modes. Dynamics of edge turbulent uctuations has been studied by correlating data from fast imaging cameras and Langmuir probes, yielding a coherent picture of transport processes involved in the SOL.
B. Saoutic, N. Dumas, Rémi Dumont, A. Durocher, F. X. Duthoit, et al.. Contribution of Tore Supra in preparation of ITER. Nuclear Fusion, IOP Publishing, 2011, 51 (9, SI), ⟨10.1088/0029-5515/51/9/094014⟩. ⟨hal-01460107⟩
