T. Tatsuno W. Dorland A. A. Schekochihin G. G. Plunk M. Barnes S. C. Cowley G. G. Howes
Electrostatic turbulence in weakly collisional, magnetized plasma can be interpreted as a cascade of entropy in phase space, which is proposed as a universal mechanism for dissipation of energy in magnetized plasma turbulence. When the nonlinear decorrelation time at the scale of the thermal Larmor radius is shorter than the collision time, a broad…
PublishedH Meyer R J Akers F Alladio L C Appel K B Axon N Ben Ayed P Boerner R J Buttery P G Carolan D Ciric C D Challis I T Chapman Et Al
Several improvements to the MAST plant and diagnostics have facilitated new studies advancing the physics basis for ITER and DEMO, as well as for future spherical tokamaks. Using the increased heating capabilities PNBI ≤ 3.8 MWH-mode at Ip = 1.2 MA was accessed showing that the energy confinement on MAST scales more weakly with Ip and more strong…
PublishedI. G. Abel M. Barnes S. C. Cowley W. Dorland A. A. Schekochihin
A new analytically and numerically manageable model collision operator is developed specifically for turbulence simulations. The like-particle collision operator includes both pitch-angle scattering and energy diffusion and satisfies the physical constraints required for collision operators: it conserves particles, momentum, and energy, obeys Boltz…
PublishedR. J. Buttery T. C. Hender
JET has made a strong contribution to the understanding of stability issues for the tokamak. An overview of its main achievements is presented, with emphasis on the latest progress in resolving the key issues for ITER. In particular, we conclude that control or avoidance strategies for neoclassical tearing modes (NTMs) will be necessary for good pe…
PublishedO. E. Garcia N. H. Bian W. Fundamenski
Radial convection of isolated filamentary structures due to interchange motions in magnetized plasmas is investigated. Following a basic discussion of vorticity generation, ballooning, and the role of sheaths, a two-field interchange model is studied by means of numerical simulations on a biperiodic domain perpendicular to the magnetic field. It is…
PublishedLBC Worth RJH Pearce J Bruce J Banks S Scales
The accuracy of process measurements of tritium with conventional ion chambers is often affected by surface tritium contamination. The measurement of tritium in the exhaust of the JET torus is particularly difficult due to surface contamination with highly tritiated hydrocarbons. JET’s first unsuccessful attempt to overcome the contamination prob…
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…
PublishedR. J. Akers J. W. Ahn L. C. Appel E. R. Arends K. B. Axon et al.
Spontaneous transitions from the low ‘‘L-mode’’ to high ‘‘H-mode’’ of tokamak plasma confinement, first observed during neutral beam heating experiments on ASDEX, are now routinely achieved in many tokamak experiments. The H-mode regime is attractive as it offers the possibility of enhanced confinement, and thus a route towards a mo…
PublishedS. C. Chapman R. O. Dendy G. Rowlands
There is increasing evidence that the Earth’s magnetosphere, like other macroscopic confined plasma systems (magnetic fusion plasmas, astrophysical accretion discs), displays sandpile-type phenomenology so that energy dissipation is by means of avalanches which do not have an intrinsic scale. This may in turn imply that these systems evolve via s…
PublishedA. Thyagaraja F. A. Haas D. J. Harvey
Tokamaks exhibit several types of relaxation oscillations such as sawteeth, fishbones and Edge Localized Modes (ELMs) under appropriate conditions. Several authors have introduced model nonlinear dynamic systems with a small number of degrees of freedom which can illustrate the generic characteristics of such oscillations. In these models, one focu…
Published