M. J. Walsh E. R. Arends P. G. Carolan M. R. Dunstan M. J. Forrest et al.
A dual laser Thomson scattering system is implemented in the Mega Amp Spherical Tokamak (MAST). The complementary features of each approach are exploited. One system is ideally suited to measuring detailed profile behavior across the plasma while the other is ideally suited though not exclusively to studying fast changing events and general charact…
PublishedD. A. Mossessian P. Snyder A. Hubbard J. W. Hughes M. Greenwald et al.
For steady state high-confinement-mode (H-mode) operation, a relaxation mechanism is required to limit build-up of the edge gradient and impurity content. Alcator C-Mod [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] sees two such mechanisms—EDA (enhanced D-alpha H mode) and grassy ELMs (edge localized modes) , but not large type I ELMs. In EDA…
PublishedG. Manfredi C. M. Roach
The generation of zonal flows and their interplay with drift wave turbulence is studied numerically using a model based on the Hasegawa–Mima equation, with an electron response depending only on the fluctuating part of the electrostatic potential. In regimes dominated by the diamagnetic velocity, large-amplitude nonlinear oscillations are observe…
PublishedR. Barnsley N. J. Peacock J. Dunn I. M. Melnick I. H. Coffey et al.
A family of Johann configuration curved crystal spectrometers has been designed to share the basic engineering features of compactness, modularity, facility of alignment and focus, and incorporation of solid-state charge coupled device detector arrays. These detectors have intrinsically low noise, useful energy resolution, two-dimensional position …
PublishedB. N. Breizman H. L. Berk M. S. Pekker S. D. Pinches S. E. Sharapov
Plasma configurations with shear reversal are prone to the excitation of unusual Alfven eigenmodes by energetic particles. These modes exhibit a quasiperiodic pattern of predominantly upward frequency sweeping ( Alfven cascades ) as the safety factor q changes in time. This work presents a theory that employs two complementary mechanisms for establ…
PublishedElizabeth Surrey
The effect of a rotation of the electrode used to accelerate a positive ion beam is treated analytically for the Joint European Torus (JET) Positive Ion Neutral Injector ~PINI! tetrode accelerator. The rotation is taken to be about an axis in the plane of the electrode and perpendicular to the beam axis, so the effect is that of a tilt in the align…
PublishedGhassan Y. Antar Glenn Counsell Yang Yu Brian Labombard Pascal Devynck
The nature of intermittency, long observed in magnetic fusion devices, was revisited lately [G. Antar et al. , Phys. Rev. Lett. 87 , 065001 (2001)]. It was shown that intermittency is caused by large-scale events with high radial velocity reaching about 1/10th of the sound speed. These type of structures were named ‘‘avaloids.’’ In the pres…
PublishedP. Helander T. Fülöp Peter J. Catto
The transport of angular momentum due to neutral atoms in the tokamak edge is calculated and shown to be sensitive to the poloidal location of the neutrals. In the absence of external momentum sources, the edge plasma is predicted to rotate spontaneously in the opposite direction to the plasma current, at a speed proportional to the radial ion temp…
PublishedR. J. Hastie J. J. Ramos F. Porcelli
The linear stability of high-toroidal-number drift-ballooning modes in tokamaks is investigated with a model that includes resistive and viscous dissipation, and assumes the mode frequency to be comparable to both the sound and diamagnetic frequencies. The coupled effect of ion drift waves and electron drift-acoustic waves is shown to be important,…
Published