R. J. Akers G. F. Counsell A. Sykes L. C. Appel E. R. Arends C. Byrom P. G. Carolan N. J. Conway G. Cunningham A. Dnestrovskij Yu.N. Dnestrovskij A. R. Field S. J. Fielding M. Gryaznevich P. Helander A. Kirk S. Korsholm R. Martin H. Meye
H -mode plasmas have been achieved on the MAST spherical tokamak at input power considerably higher than predicted by conventional threshold scalings. Following L - H transition, a clear improvement in energy confinement is obtained, exceeding recent international scalings even at densities approaching the Greenwald density limit. Transition is acc…
PublishedR. J. Buttery O. Sauter R. Akers M. Gryaznevich R. Martin C. D. Warrick H. R. Wilson The Mast Team
Results from MAST provide a first test of neoclassical tearing mode physics in the spherical tokamak (ST). The mode accounts for the main performance limit in conventional tokamaks. Its behavior in the ST is remarkably well described by existing theoretical models, although it is more readily seeded by sawtooth events in these scenarios. Modeling c…
PublishedM. J. Mantsinen L.C. Ingesson T. Johnson V.G. Kiptily M.-L. Mayoral S. E. Sharapov B. Alper L. Bertalot S. Conroy L.-G. Eriksson T. Hellsten J.-M. Noterdaeme S. Popovichev E. Righi A. A. Tuccillo
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 3 He ions. Direct evidence for the wave-induced pinch has been obtained from the measured -ray emission profiles. Concurrent differences in the excitation of Alfve?n …
PublishedS. L. Dudarev
Thermally activated mobility of clusters of interstitial atoms is an important factor driving microstructural evolution of materials under irradiation. Molecular dynamics simulations show that the statistics of onedimensional Brownian motion of clusters is characterized by unusual correlated jumps spanning many interatomic distances. We use the Fre…
PublishedT. Fülöp P. Helander Peter J. Catto
Neutral atoms in the tokamak edge affect the electric field and plasma flow through charge exchange. Here, it is shown that these effects depend sensitively on the poloidal location of the atoms. It is found that the radial electric field and toroidal flow velocity in a collisional edge plasma are largest if the atoms are concentrated on the inboar…
PublishedP. Helander L.-G. Eriksson R. J. Akers C. Byrom C.G. Gimblett M. R. Tournianski
Spontaneous acceleration of ions to suprathermal energies is observed during magnetic reconnection in the Mega-Ampere Spherical Tokamak (MAST). A high-energy tail is observed in the iondistribution function following each internal reconnection event in Ohmic discharges. This phenomenon is explained in terms of runaway ion acceleration in the electr…
PublishedF. Andersson P. Helander D. Anderson H. Smith M. Lisak
In this paper, a general and systematic scheme is formulated for finding approximate solutions of two-way diffusion equations. This expansion scheme is valid for arbitrary mean-free path and can be carried out to any desired accuracy. Its potential is demonstrated by constructing approximate solutions for two problems concerning the kinetics of an …
PublishedV. Shevchenko Y. Baranov M. O’Brien A. Saveliev
Electron-Bernstein waves (EBW) were excited in the plasma by mode converted extraordinary ( X ) waves launched from the high field side of the COMPASS-D tokamak at different toroidal angles. It has been found experimentally that X -mode injection perpendicular to the magnetic field provides maximum heating efficiency. Noninductive currents of up to…
PublishedA. Thyagaraja N.L Oureiro P.J. Knight
Advection–diffusion equations occur in a wide variety of fields in many contexts of active and passive transport in fluids and plasmas. The effects of sheared advective flows in the presence of irreversible processes such as diffusion and viscosity are of considerable current interest in tokamak and astrophysical contexts, where they are thought …
PublishedJ. M. A. Ashbourn I. M. Melnick N. J. Peacock
We present a comparison of measured and theoretically modeled Lyman- a intensity ratios of hydrogenlike Al XIII impurity ions in a deuterium base plasma in the COMPASS-D tokamak. The time evolution of the intensity ratios is computed from a collisional-radiative model using measured plasma parameters and compared with line-of-sight integral values …
Published