A. J. Webster D. J. Szwer H. R. Wilson
Modern tokamaks can produce transport barriers TBs—localized regions with an increased energy confinement. Previous studies have been unable to examine the stability of internal TBs to radially extended short-wavelength magnetohydrodynamic instabilities “ballooning modes”, for the usual case with a sheared plasma flow and a magnetic shear tha…
PublishedC. Silva B. Gonçalves C. Hidalgo M. A. Pedrosa K. Erents G. Matthews R. A. Pitts
A multi-probe system has been developed to investigate the importance of electron temperature fluctuations turbulent transport in the Joint European Torus boundary plasma. The compact five-pin triple probe has been designed to reduce the phase delay of fluctuations due to the finite pin separation in the standard triple probe technique, while still…
PublishedK.J.H. Phillips J.A. Rainnie L. K. Harra J. Dubau F.P. Keenan N.J. Peacock
The inclusion of collisional rates for He-like Fe and Ca ions is discussed with reference to the analysis of solar flare Fe XXV and Ca XIX line emission, particularly from the Yohkoh Bragg Crystal Spectrometer (BCS). The new data are a slight improvement on calculations presently used in the BCS analysis software in that the discrepancy in the Fe X…
PublishedS. E. Sharapov B. Alper H. L. Berk D. N. Borba B. N. Breizman et al.
Experiments designed for generating internal transport barriers in the plasmas of the Joint European Torus [JET, P. H. Rebut et al. , Proceedings of the 10th International Conference, Plasma Physics and Controlled Nuclear Fusion, London ~ International Atomic Energy Agency, Vienna, (1985), Vol. I, p. 11 ] reveal cascades of Alfven perturbations wit…
PublishedH. R. Wilson P. B. Snyder G. T. A. Huysmans R. L. Miller
A new computational tool, edge localized instabilities in tokamaks equilibria (ELITE), has been developed to help our understanding of short wavelength instabilities close to the edge of tokamak plasmas. Such instabilities may be responsible for the edge localized modes observed in high confinement H-mode regimes, which are a serious concern for ne…
PublishedT. Edlington R. Martin T. Pinfold
The mega-ampere spherical tokamak (MAST) experiment is a new, large, low aspect ratio device operating its first experimental physics campaign. Designed to study a wide variety of plasma shapes with up to 2 MA of plasma current with an aspect ratio down to 1.3, the poloidal field (PF) coils used for plasma formation, equilibrium and shaping are ins…
PublishedS. C. Chapman R.O. Dendy B. Hnat
Confinement phenomenology characteristic of magnetically confined plasmas emerges naturally from a simple sandpile algorithm when the parameter controlling redistribution scale length is varied. Close analogs are found for enhanced confinement, edge pedestals, and edge localized modes (ELMs), and for the qualitative correlations between them. These…
PublishedR. A. Cairns C. N. Lashmore-Davies
Electron Bernstein waves are analyzed as possible candidates for heating spherical tokamaks. An inhomogeneous plane slab model of the plasma with a sheared magnetic field is used to calculate the linear conversion of the ordinary mode (O-mode) to the extraordinary mode (X-mode). A formula for the fraction of the incident O-mode energy which is conv…
PublishedP. Helander L.-G. Eriksson F. Andersson
The kinetic theory of runaway electron avalanches caused by close Coulomb collisions is extended to account for radial diffusion. This is found to slow down the growth of avalanches. An approximate analytical formula for the growth rate is derived and is verified by a three-dimensional Monte Carlo code constructed for this purpose. As the poloidal …
PublishedD. A. Gates R. Akers L. Appel P. G. Carolan N. Conway et al.
The Small Tight Aspect Ratio Tokamak (START) [A. Sykes et al., Nucl. Fusion 32, 769 (1994)] spherical tokamak has recently achieved the record value of toroidal beta~30% in a tokamak-like configuration. The improvements that have made these results possible are presented along with a description of the global equilibrium parameters of the discharge…
Published