| 1. |
- Meyer, H., et al.
(författare)
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Overview of physics results from MAST towards ITER/DEMO and the MAST Upgrade
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 53:10, s. 104008-
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Tidskriftsartikel (refereegranskat)abstract
- New diagnostic, modelling and plant capability on the Mega Ampere Spherical Tokamak (MAST) have delivered important results in key areas for ITER/DEMO and the upcoming MAST Upgrade, a step towards future ST devices on the path to fusion currently under procurement. Micro-stability analysis of the pedestal highlights the potential roles of micro-tearing modes and kinetic ballooning modes for the pedestal formation. Mitigation of edge localized modes (ELM) using resonant magnetic perturbation has been demonstrated for toroidal mode numbers n = 3, 4, 6 with an ELM frequency increase by up to a factor of 9, compatible with pellet fuelling. The peak heat flux of mitigated and natural ELMs follows the same linear trend with ELM energy loss and the first ELM-resolved T-i measurements in the divertor region are shown. Measurements of flow shear and turbulence dynamics during L-H transitions show filaments erupting from the plasma edge whilst the full flow shear is still present. Off-axis neutral beam injection helps to strongly reduce the redistribution of fast-ions due to fishbone modes when compared to on-axis injection. Low-k ion-scale turbulence has been measured in L-mode and compared to global gyro-kinetic simulations. A statistical analysis of principal turbulence time scales shows them to be of comparable magnitude and reasonably correlated with turbulence decorrelation time. T-e inside the island of a neoclassical tearing mode allow the analysis of the island evolution without assuming specific models for the heat flux. Other results include the discrepancy of the current profile evolution during the current ramp-up with solutions of the poloidal field diffusion equation, studies of the anomalous Doppler resonance compressional Alfven eigenmodes, disruption mitigation studies and modelling of the new divertor design for MAST Upgrade. The novel 3D electron Bernstein synthetic imaging shows promising first data sensitive to the edge current profile and flows.
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| 2. |
- Rozhansky, V., et al.
(författare)
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Modelling of the edge plasma of MAST in the presence of resonant magnetic perturbations
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 51:8, s. 083009-
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Tidskriftsartikel (refereegranskat)abstract
- The transport code B2SOLPS5.2 is used to simulate L- and H-mode discharges on MAST with and without resonant magnetic perturbations (RMP). The simulated variation of the radial electric field (less negative for RMP) and toroidal rotation (spin-up in the co-current direction for RMP) is in agreement with the experiment. The pump-out effect in the L-modes with high and medium plasma density and in the H-mode is caused by the additional neoclassical radial plasma flow in the electric field modified due to the electron loss along the stochastic field lines. The pump-out in the low-density L-mode can be reproduced only by a significant rise in the turbulent transport coefficients. The modelling suggests strong RMP screening. An analytical model for RMP screening is proposed.
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| 3. |
- Kaveeva, E., et al.
(författare)
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Interpretation of the observed radial electric field inversion in the TUMAN-3M tokamak during MHD activity
- 2008
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 48:7
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model for the toroidal rotation spin-up and generation of a positive radial electric field during the stochastization of plasma edge is put forward. Equations for the toroidal velocity and for modification of the core radial electric field have been derived. A detailed comparison of the model results with the radial electric field and plasma potential measurements during MHD activity in the TUMAN-3M tokamak is presented.
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| 7. |
- Rozhansky, V., et al.
(författare)
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Stochastization and pump-out in edge plasma caused by edge localized modes
- 2015
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Ingår i: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 57:11
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms of current generation in edge localized mode (ELM) filaments are discussed. It is shown that dipole type currents should flow in the filaments and that these currents are short-circuited through the ambient plasma of the scrape-off layer. The steady-state monopole currents in the filaments cannot be closed through the ambient plasma and oscillatory currents with Alfven frequency should emerge instead. The dipole type currents in the filaments are sufficient to produce magnetic field perturbations which create a stochastic layer inside the edge transport barrier (ETB) region. The dynamic of penetration of the magnetic field perturbations is analyzed and it is shown that the corresponding time is comparable with the life time of the filaments. At the stage when the ETB region is stochastized by the currents of the filaments the radial electric field becomes less negative or even positive inside the ETB and the onset of outward convective flux takes place. It is shown that this outward flux could lead to the significant pump-out effect - the density decrease in the pedestal region.
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