Showing 991 - 1000 of 1620 Journals Results
2011
IT Chapman MP Gryaznevich DF Howell YQ Liu The Mast Team
Resistive wall mode stability limits have been probed by MHD spectroscopy and numerical modelling. MAST plasmas have operated up to βN = 5.7, well above the predicted ideal kink no-wall limit or measured resonant field amplification limits due to a combination of rotation and kinetic damping. By varying the density, both the rotation and the fast …
Published2011
M. Yu. Lavrentiev R. Soulairol Chu-Chun Fu D. Nguyen-Manh S. L. Dudarev
Noncollinear configurations of local magnetic moments at Fe/Cr interfaces in Fe-Cr alloys are explored using a combination of density functional theory (DFT) and magnetic cluster expansion (MCE) simulations. We show that magnetic frustration at Fe/Cr interfaces can be partially resolved through the formation of noncollinear magnetic structures, whi…
Published2011
F.I. Parra M. Barnes E.G. Highcock A.A. Schekochihin S.C. Cowley
The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity…
Published2011
M Valovic L Garzotti C Gurl R Akers J Harrison C Michael G Naylor R Scannell The Mast Team
Access into H-mode is studied in the MAST tokamak when plasma is fuelled by cryogenic pellets. It is shown that pellet fuelling from the high field side allows access to Hmode in plasmas heated by neutral beams. Simple and two-stage L-H transitions are identified. The results of comparison of the L-H transitions with pellet injection with transitio…
Published2011
E. Lerche D. Van Eester J. Ongena M.L. Mayoral T. Johnson et al.
The non-active operation phase of ITER will be done in H|4 He plasmas at half the nominal magnetic field, B 0 =2.65T. At this field|for the given frequency range of the ICRF system (f=40-55MHz), three ICRF heating scenarios are available a priori : (i) Fundamental ICRH of majority H plasmas at f?40MHz, (ii) second harmonic (N=2) 3 He ICRH in H plas…
Published2011
D. Yadykin Y.Q. Liu R. Paccagnella
The kinetic effects, due to the mode resonance with thermal particle drift motions in the reversed field pinch (RFP) plasmas, are numerically investigated for the stability of the resistive wall mode, using a non-perturbative MHD-kinetic hybrid formulation. The kinetic effects are generally found too weak to substantially change the mode growth rat…
Published2011
W A Cooper J P Graves O Sauter S P Hirshman I T Chapman M Gobbin L Marrelli P Martin I Predebon D Terranova
Magnetohydrodynamic equilibrium states with a three-dimensional helical core are computed to model the MAST spherical tokamak and the RFX-mod reversed field pinch. The boundary is fixed as axisymmetric. The MAST equilibrium state has the appearance of an internal kink mode and is obtained under conditions of weak reversed central shear. The RFX-mod…
Published2011
M. R. Gilbert S. Queyreau J. Marian
The low-temperature plastic yield of a -Fe single crystals is known to display a strong temperature dependence and to be controlled by the thermally activated motion of screw dislocations. In this paper, we present molecular dynamics simulations of 1 2 111{112} screw dislocation motion as a function of temperature and stress in order to extract mob…
Published2011
M. Barnes F.I. Parra E.G. Highcock A.A. Schekochihin S.C. Cowley C.M. Roach
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, ind…
Published2011