E. G. Highcock M. Barnes A. A. Schekochihin F. I. Parra C. M. Roach S.C. Cowley
The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all nonzero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases …
PublishedT. 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…
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…
PublishedI. G. Abel M. Barnes S. C. Cowley W. Dorland G. W. Hammett A. A. Schekochihin T. Tatsuno
We motivate the need to include collisional dissipation in gyrokinetic turbulence simulations, and constract criteria for a physically vaUd model of such dissipation. A new analytically manageable operator satisfying those criteria is presented and transformed into gyrokinetic variables. The form of conservation laws for collision operators in gyro…
PublishedM. K. Lilley S. E. Sharapov
A discrete spectrum of compressional Alfvén eigenmodes and ion-ion hybrid eigenmodes is found to exist above the tritium ion cyclotron frequency in the deuterium-tritium D-T plasma of a spherical tokamak power plant STPP [H. R. Wilson and et al. , 19th IAEA Fusion Energy Conference IAEA, Lyon, France, (2002), No. FT/1-4]. An equilibrium magnetic w…
PublishedA. Kirk H. R.Wilson G. F. Counsell R. Akers E. Arends S. C. Cowley J. Dowling B. Lloyd M. Price M.Walsh Mast Team
This Letter provides information on the spatial and temporal structure of periodic eruptions observed in magnetically confined laboratory fusion plasmas, called edge-localized modes (ELMs), and highlights similarities with solar eruptions. Taken together, the observations presented in this Letter provide strong evidence for ELMs being associated wi…
PublishedH. R.Wilson S. C. Cowley
Flux tubes confined in tokamaks are observed to erupt explosively in some plasma disruptions and edge localized modes. Similar eruptions occur in astrophysical plasmas, for example, in solar flares and magnetospheric substorms. A single unifying nonlinear evolution equation describing such behavior in both astrophysical and tokamak plasmas is deriv…
PublishedD.J. Applegate C.M. Roach S.C. Cowley W.D. Dorland N. Joiner R.J. Akers N.J. Conway A.R. Field A. Patel M. Valovic M.J. Walsh
Gyrokinetic microstability analyses, with and without electromagnetic effects, are presented for a spherical tokamak plasma equilibrium closely resembling that from a high confinement mode ( H mode ) discharge in the mega-ampere spherical tokamak ( MAST ) [ A. Sykes et al. , Nucl. Fusion 41 , 1423 ( 2001 )] . Electrostatic ion temperature gradient …
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