Publications (45)
Critically balanced ion temperature gradient turbulence in fusion plasmas
M. Barnes, F. I. Parra, A. A. Schekochihin
Scaling laws for ion temperature gradient driven turbulence in magnetized toroidal plasmas are derived and compared with direct numerical simulations. Predicted dependences of turb…
Electrostatic gyrokinetic simulations in Wendelstein 7-X geometry: benchmark between the codes stella and GENE
A. González-Jerez, P. Xanthopoulos, J. M. GarcÃa-Regaña +6
The first experimental campaigns have proven that, due to the optimization of the magnetic configuration with respect to neoclassical transport, the contribution of turbulence is e…
Energy partition between Alfvénic and compressive fluctuations in magnetorotational turbulence with near-azimuthal mean magnetic field
Y. Kawazura, A. A. Schekochihin, M. Barnes +2
The theory of magnetohydrodynamic (MHD) turbulence predicts that Alfvénic and slow-mode-like compressive fluctuations are energetically decoupled at small scales in the inertial r…
Asymptotic scaling theory of electrostatic turbulent transport in magnetised fusion plasmas
T. Adkins, I. G. Abel, M. Barnes +7
Turbulent transport remains one of the principal obstacles to achieving efficient magnetic confinement in fusion devices. Two of the dominant drivers of the turbulence are microsca…
Ion versus electron heating in compressively driven astrophysical gyrokinetic turbulence
Y. Kawazura, A. A. Schekochihin, M. Barnes +4
The partition of irreversible heating between ions and electrons in compressively driven (but subsonic) collisionless turbulence is investigated by means of nonlinear hybrid gyroki…
Injection and dump considerations for a 16.5 TeV HE-LHC
B. Goddard, M. Barnes, W. Bartmann +8
Injection and beam dumping is considered for a 16.5 TeV hadron accelerator in the current LHC tunnel, with an injection energy in the range 1 - 1.3 TeV. The present systems are des…
Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons
M. R. Hardman, F. I. Parra, C. Chong +6
Ion-gyroradius-scale microinstabilities typically have a frequency comparable to the ion transit frequency. Due to the small electron-to-ion mass ratio and the large electron trans…
Nonlinear phase mixing and phase-space cascade of entropy in gyrokinetic plasma turbulence
T. Tatsuno, W. Dorland, A. A. Schekochihin +4
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 dissipat…
Three-Dimensional Inhomogeneity of Electron-Temperature-Gradient Turbulence in the Edge of Tokamak Plasmas
J. F. Parisi, F. I. Parra, C. M. Roach +15
Nonlinear multiscale gyrokinetic simulations of a Joint European Torus edge pedestal are used to show that electron-temperature-gradient (ETG) turbulence has a rich three-dimension…
Linearized model Fokker-Planck collision operators for gyrokinetic simulations. I. Theory
I. G. Abel, M. Barnes, S. C. Cowley +2
A new analytically and numerically manageable model collision operator is developed specifically for turbulence simulations. The like-particle collision operator includes both pitc…
Experimental Signatures of Critically Balanced Turbulence in MAST
Y. -c. Ghim, A. A. Schekochihin, A. R. Field +8
Beam Emission Spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated…
A Scale-Separated Approach for Studying Coupled Ion and Electron Scale Turbulence
M. R. Hardman, M. Barnes, C. M. Roach +1
Multiple space and time scales arise in plasma turbulence in magnetic confinement fusion devices because of the smallness of the square root of the electron-to-ion mass ratio $(m_e…
New linear stability parameter to describe low- electromagnetic microinstabilities driven by passing electrons in axisymmetric toroidal geometry
M. R. Hardman, F. I. Parra, B. S. Patel +8
In magnetic confinement fusion devices, the ratio of the plasma pressure to the magnetic field energy, , can become sufficiently large that electromagnetic microinstabilities b…
Dependence of intrinsic rotation reversals on collisionality in MAST
J. C. Hillesheim, F. I. Parra, M. Barnes +6
Tokamak plasmas rotate even without external injection of momentum. A Doppler backscattering system installed at MAST has allowed this intrinsic rotation to be studied in Ohmic L-m…
Interpreting Radial Correlation Doppler Reflectometry using Gyrokinetic Simulations
J. Ruiz Ruiz, F. I. Parra, V. H. Hall-Chen +12
A linear response, local model for the DBS amplitude applied to gyrokinetic simulations shows that radial correlation Doppler reflectometry measurements (RCDR, Schirmer et al., Pla…
A Hybrid Gyrokinetic Ion and Isothermal Electron Fluid Code for Astrophysical Plasma
Y. Kawazura, M. Barnes
This paper describes a new code for simulating astrophysical plasmas that solves a hybrid model composed of gyrokinetic ions (GKI) and an isothermal electron fluid (ITEF) [A. Schek…
Direct multiscale coupling of a transport code to gyrokinetic turbulence codes
M. Barnes, I. G. Abel, W. Dorland +3
Direct coupling between a transport solver and local, nonlinear gyrokinetic calculations using the multiscale gyrokinetic code TRINITY [M. Barnes, Ph.D. thesis, arxiv:0901.2868] is…
Electrostatic microturbulence in W7-X: comparison of local gyrokinetic simulations with Doppler reflectometry measurements
A. González-Jerez, J. M. GarcÃa-Regaña, I. Calvo +5
The first experimental campaigns of Wendelstein 7-X (W7-X) have shown that turbulence plays a decisive role in the performance of neoclassically optimized stellarators. This stress…
Optimisation of confinement in a fusion reactor using a nonlinear turbulence model
E. G. Highcock, N. R. Mandell, M. Barnes +1
The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat…
Linearized model Fokker-Planck collision operators for gyrokinetic simulations. II. Numerical implementation and tests
M. Barnes, I. G. Abel, W. Dorland +6
A set of key properties for an ideal dissipation scheme in gyrokinetic simulations is proposed, and implementation of a model collision operator satisfying these properties is desc…
Freely decaying turbulence in two-dimensional electrostatic gyrokinetics
T. Tatsuno, G. G. Plunk, M. Barnes +3
In magnetized plasmas, a turbulent cascade occurs in phase space at scales smaller than the thermal Larmor radius ("sub-Larmor scales") [Phys. Rev. Lett. 103, 015003 (2009)]. When…
High-beta runaway transitions in a fluid model of electromagnetic ion-temperature-gradient turbulence
Y. Zhang, M. Barnes, A. A. Schekochihin +2
Gyrokinetic simulations of tokamak turbulence indicate that fluctuation levels increase abruptly and dramatically when the plasma beta exceeds a certain critical value. This increa…
Transport Bifurcation Induced by Sheared Toroidal Flow in Tokamak Plasmas
E. G. Highcock, M. Barnes, F. I. Parra +3
First-principles numerical simulations are used to describe a transport bifurcation in a differentially rotating tokamak plasma. Such a bifurcation is more probable in a region of…
High-m Kink/Tearing Modes in Cylindrical Geometry
J. W. Connor, R. J. Hastie, I. Pusztai +2
The global ideal kink equation, for cylindrical geometry and zero beta, is simplified in the high poloidal mode number limit and used to determine the tearing stability parameter,…
Turbulent heating in an inhomogeneous, magnetised plasma slab
M. Barnes, P. Abiuso, W. Dorland
Observational evidence in space and astrophysical plasmas with long collisional mean free path suggests that more massive charged particles may be preferentially heated. One possib…
Turbulent transport and heating of trace heavy ions in hot, magnetized plasmas
M. Barnes, F. I. Parra, W. Dorland
Scaling laws for the transport and heating of trace heavy ions in low-frequency, magnetized plasma turbulence are derived and compared with direct numerical simulations. The predic…
Intrinsic rotation driven by non-Maxwellian equilibria in tokamak plasmas
M. Barnes, F. I. Parra, J. P. Lee +3
The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising from diamagnet…
Zero-Turbulence Manifold in a Toroidal Plasma
E. G. Highcock, A. A. Schekochihin, S. C. Cowley +4
Sheared toroidal flows can cause bifurcations to zero-turbulent-transport states in tokamak plasmas. The maximum temperature gradients that can be reached are limited by subcritica…
Zonal-flow generation and saturation of electromagnetic ion-scale turbulence in tokamaks
Y. Zhang, T. Adkins, M. Barnes +5
The paper uses local gyrokinetic simulations to study how electromagnetic ion‑scale turbulence in tokamaks generates zonal flows, finding that a combined parameter β_eff = q²β_e co…
Scaling laws for the cutoff wavenumber of the short-wavelength ion-temperature-gradient mode in a Z-pinch
O. Gupta, M. Barnes, F. I. Parra +4
We use a heuristic fluid model to predict the dependence of the cutoff wave number for the short-wavelength ion temperature gradient (SWITG) mode on ion density gradient, ion tempe…
Momentum injection in tokamak plasmas and transitions to reduced transport
F. I. Parra, M. Barnes, E. G. Highcock +2
The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The trans…
Transport Bifurcation in a Rotating Tokamak Plasma
E. G. Highcock, M. Barnes, A. A. Schekochihin +3
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 linea…
Turbulent transport in tokamak plasmas with rotational shear
M. Barnes, F. I. Parra, E. G. Highcock +3
Nonlinear gyrokinetic simulations have been conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabi…
Gyrokinetic simulation of entropy cascade in two-dimensional electrostatic turbulence
T. Tatsuno, M. Barnes, S. C. Cowley +5
Two-dimensional electrostatic turbulence in magnetized weakly-collisional plasmas exhibits a cascade of entropy in phase space [Phys. Rev. Lett. 103, 015003 (2009)]. At scales smal…
Stabilisation of short-wavelength instabilities by parallel-to-the-field shear in long-wavelength flows
M. R. Hardman, M. Barnes, C. M. Roach
Magnetised plasma turbulence can have a multiscale character: instabilities driven by mean temperature gradients drive turbulence at the disparate scales of the ion and the electro…
Ion temperature and density gradient driven instabilities and turbulence in Wendelstein 7-X close to the stability threshold
L. Podavini, A. Zocco, J. M. GarcÃa-Regaña +4
Electrostatic gyrokinetic instabilities and turbulence in the Wendelstein 7-X stellarator are studied. Particular attention is paid to the ion-temperature-gradient (ITG) instabilit…
Prevention of core particle depletion in stellarators by turbulence
H. Thienpondt, J. M. GarcÃa-Regaña, I. Calvo +11
In reactor-relevant plasmas, neoclassical transport drives an outward particle flux in the core of large stellarators and predicts strongly hollow density profiles. However, this t…
Gyrokinetic simulations in stellarators using different computational domains
E. Sánchez, J. M. GarcÃa-Regaña, A. Bañón Navarro +9
In this work, we compare gyrokinetic simulations in stellarators using different computational domains, namely, flux tube, full-flux-surface, and radially global domains. Two probl…
Turbulent transport of impurities in 3D devices
J. M. GarcÃa-Regaña, M. Barnes, I. Calvo +5
A large diffusive turbulent contribution to the radial impurity transport in Wendelstein 7-X (W7-X) plasmas has been experimentally inferred during the first campaigns and numerica…
Impact of plasma shaping on tokamak microstability
O. Beeke, M. Barnes, M. Romanelli +2
We have used the local- gyrokinetic code GS2 to perform studies of the effect of flux-surface shaping on two highly-shaped, low- and high- JT-60SA-relevant equilibria, i…
A phase-shift-periodic parallel boundary condition for low-magnetic-shear scenarios
D. A. St-Onge, M. Barnes, F. I. Parra
We formulate a generalized periodic boundary condition as a limit of the standard twist-and-shift parallel boundary condition that is suitable for simulations of plasmas with low m…
Turbulent impurity transport simulations in Wendelstein 7-X plasmas
J. M. GarcÃa-Regaña, M. Barnes, I. Calvo +8
A study of turbulent impurity transport by means of quasilinear and nonlinear gyrokinetic simulations is presented for Wendelstein 7-X (W7-X). The calculations have been carried ou…
A novel approach to radially global gyrokinetic simulation using the flux-tube code
D. A. St-Onge, M. Barnes, F. I. Parra
A novel approach to global gyrokinetic simulation is implemented in the flux-tube code . This is done by using a subsidiary expansion of the gyrokinetic equation i…
Multiscale Gyrokinetics for Rotating Tokamak Plasmas: Fluctuations, Transport and Energy Flows
I. G. Abel, G. G. Plunk, E. Wang +4
This paper presents a complete theoretical framework for plasma turbulence and transport in tokamak plasmas. The fundamental scale separations present in plasma turbulence are codi…
Suppression of temperature-gradient-driven turbulence by sheared flows in fusion plasmas
P. G. Ivanov, T. Adkins, D. Kennedy +3
Starting from the assumption that saturation of plasma turbulence driven by temperature-gradient instabilities in fusion plasmas is achieved by a local energy cascade between a lon…