E. G. Highcock M. Barnes A. A. Schekochihin F. I. Parra C. M. Roach S.C. Cowley
The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all nonzero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases …
PublishedG. Hommen M. De Baar P. Nuij G. Mcardle R. Akers M. Steinbuch
A new diagnostic is developed to reconstruct the plasma boundary using visible wavelength images. Exploiting the plasma’s edge localized and toroidally symmetric emission profile, a new coordinate transform is presented to reconstruct the plasma boundary from a poloidal view image. The plasma boundary reconstruction is implemented in MATLAB and a…
PublishedYueqiang Liu M.S.Chu Y.In M.Okabayashi
The stability and resonant field response of current driven resistive wall modes are numerically studied for DIII-D [J. L. Luxon, Nucl. Fusion 42 , 614 (2002)] low pressure plasmas. The resonant field response of the feedback-stabilized resistive wall mode is investigated both analytically and numerically, and compared with the response from intrin…
PublishedI. T. Chapman R. Scannell W. A. Cooper J. P. Graves R. J. Hastie G. Naylor A. Zocco
Thomson scattering measurements with subcentimeter spatial resolution have been made during a sawtooth crash in a Mega Ampere Spherical Tokamak fusion plasma. The unparalleled resolution of the temperature profile has shed new light on the mechanisms that underlie the sawtooth. As magnetic reconnection occurs, the temperature gradient at the island…
PublishedT. O’Gorman P. J. Mc Carthy S. Prunty M. J. Walsh M. R. Dunstan R. B. Huxford G. Naylor Emmanuel Maguet R. Scannell S. Shibaev
A major upgrade to the ruby Thomson scattering (TS) system has been designed and implemented on the Mega-ampere spherical tokamak (MAST). MAST is equipped with two TS systems, a Nd:YAG laser system and a ruby laser system. Apart from common collection optics each system provides independent measurements of the electron temperature and density profi…
PublishedV.Rozhansky E.Kaveeva P. Molchanov I.Veselova S.Voskoboynikov D.Coster A.Kirk S.Lisgo E.Nardon
The impact of resonance magnetic perturbations (RMP) on the structure of the edge transport barrier has been studied. A new model for the density pump-out mechanism during the stochastization of the plasma edge is proposed. The observed phenomena are explained as a result of the impact of the ambipolar electric field, which is modified during RMP, …
PublishedK. G. McClements M. J. Hole
The effects of poloidal and toroidal flows on tokamak plasma equilibria are examined in the magnetohydrodynamic limit. “Transonic” poloidal flows of the order of the sound speed multiplied by the ratio of poloidal magnetic field to total field can cause the normally elliptic Grad– Shafranov GS equation to become hyperbolic in part of the solu…
PublishedJ.W.S. Cook S.C. Chapman
We present first principles simulations of the direct collisionless coupling of the free energy of fusionborn ions into electron current in a magnetically confined fusion plasma. These simulations demonstrate, for the first time, a key building block of some ‘‘alpha channeling’’ scenarios for tokamak experiments. Spontaneously excited obliq…
Published