Elizabeth 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…
PublishedS. L. Dudarev A. A. Semenov C. H. Woo
We found that by assuming that the density of dislocations in an irradiated material varies as a function of the distance to grain boundaries and that mobile interstitial defect clusters perform three-dimensional diffusional motion it is possible to achieve significantly better agreement with experimental observations of profiles of heterogeneous v…
PublishedD. Hughes M. Paczuski R.O. Dendy P. Helander K.G. McClements
A model for the solar coronal magnetic field is proposed where multiple directed loops evolve in space and time. Loops injected at small scales are anchored by footpoints of opposite polarity moving randomly on a surface. Nearby footpoints of the same polarity aggregate, and loops can reconnect when they collide. This may trigger a cascade of furth…
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…
PublishedP. Helander D. J.Ward
It is shown that electron-positron pair production is expected to occur in post-disruption plasmas in large tokamaks, including JET and JT-60U, where up to about 10 14 positrons may be created in collisions between multi-MeV runaway electrons and thermal particles. If the loop voltage is large enough, they are accelerated and form a beam of long-li…
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…
PublishedX. Garbet L. Garzotti P. Mantica H. Nordman M. Valovic H.Weisen C. Angioni
Particle transport in magnetized plasmas is investigated with a fluid model of drift wave turbulence. An analytical calculation shows that magnetic field curvature and thermodiffusion drive an anomalous pinch. The curvature driven pinch velocity is consistent with the prediction of turbulence equipartition theory. The thermodiffusion flux is found …
PublishedValeria T. G. Riccardo Philip L. Andrew Alan Sandford Kaye Peter Noll
In view of the modification to the Joint European Torus (JET) plasma facing components foreseen for the 2004 shutdown, the disruption design criteria for invessel components have been updated building on the operational experience with divertor plasmas gained since the early 1990s. In fast disruptions the largest contribution to the electromechanic…
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…
PublishedC. Hidalgo B. Goncálves C. Silva M. A. Pedrosa K. Erents M. Hron G. F. Matthews
The dynamical coupling between turbulent transport and parallel flows has been investigated in the plasma boundary region of the Joint European Torus tokamak. Experimental results show that there is a dynamical relationship between transport and parallel flows. As the size of transport events increases, parallel flows also increase. These results s…
Published