
UKAEACCFEPR(22)012021
Electromagnetic instabilities and turbulence driven by the electrontemperature gradient are considered in a local slab model of a tokamaklike plasma, with constant equilibrium gradients (including magnetic drifts but no magnetic shear). The model describes perturbations at scales both larger and smaller than the electron inertial scale de…

UKAEACCFEPR(20)202020
The saturated state of turbulence driven by the iontemperaturegradient instability is investigated using a twodimensional longwavelength fluid model that describes the perturbed electrostatic potential and perturbed ion temperature in a magnetic field with constant curvature (a Zpinch) and an equilibrium temperature gradient. Numerical simulat…

CCFEPR(16)482016
In electrostatic simulations of MAST plasma at electrongyroradius scales, using the local fluxtube gyrokinetic code GS2 with adiabatic ions, we find that the longtime saturated electron heat flux (the level most relevant to energy transport) decreases as the electron collisionality decreases. At early simulation times, the heat flux quasisatura…

2014
Observations of ionscale density turbulence of relative amplitude are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging Beam Emission Spectroscopy (BES) diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation …

2013
Magnetic reconnection in strongly magnetized (lowbeta), weakly collisional plasmas is investigated by using a novel fluidkinetic model [Zocco and Schekochihin, Phys. Plasmas 18, 102309 (2011)] which retains nonisothermal electron kinetics. It is shown that electron heating via Landau damping (linear phase mixing) is the dominant dissipation mecha…

2013
Beam emission spectroscopy (BES) measurements of ionscale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with iontemperature or density gradients, the particle (ion) streaming time along the magnetic field, and the magnetic drift time are consistently comparable, suggesting…

2012
Sheared toroidal flows can cause bifurcations to zeroturbulenttransport states in tokamak plasmas. The maximum temperature gradients that can be reached are limited by subcritical turbulence driven by the parallel velocity gradient. Here it is shown that magnetic field pitch/inverse aspect ratio is a critical control parameter for sheared tokamak…

2012
Using theoretical arguments, a simple scaling law for the size of the intrinsic rotation observed in tokamaks in the absence of a momentum injection is found: The velocity generated in the core of a tokamak must be proportional to the ion temperature difference in the core divided by the plasma current, independent of the size of the device. The co…

2011
Scaling laws for ion temperature gradient driven turbulence in magnetized toroidal plasmas are derived and compared with direct numerical simulations. Predicted dependences of turbulence fluctuation amplitudes, spatial scales, and resulting heat fluxes on temperature gradient and magnetic field line pitch are found to agree with numerical results i…

2011
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, ind…
Showing 1  10 of 19 UKAEA Paper Results