Patrick Diamond

Understanding LOC/SOC phenomenology in tokamaks

Nuclear Fusion · 2020-08-04 · 39 citations

Phenomenology of Ohmic energy confinement saturation in tokamaks is reviewed. Characteristics of the linear Ohmic confinement (LOC) and saturated Ohmic confinement (SOC) regimes are documented and transformations in all transport channels across the LOC/SOC transition are described, including rotation reversals, 'non-local' cut-off and density peaking, in addition to dramatic changes in fluctuation intensity. Unification of results from nearly 20 devices indicates that the LOC/…

Anisotropic E <b>×</b> B shearing rate in a magnetic island

Physics of Plasmas · 2021-02-01 · 30 citations

We derive the E × B shearing rate associated with vortex flow inside a macroscopic magnetic island (MI) in axisymmetric toroidal geometry. Due to the elongation of the MI and incompressibility of the E × B flow, the shearing rate near X-points is much lower than that near the mid-plane (x-axis of the local Cartesian coordinate) of the MI on the same flux surface. Furthermore, the rate formally vanishes at the X-points where the local poloidal magnetic field associated with the MI stagnates. This…

A unified theory of zonal flow shears and density corrugations in drift wave turbulence

Plasma Physics and Controlled Fusion · 2020-12-22 · 23 citations

Abstract A unified theory of zonal flow shears and density corrugations in drift wave turbulence is presented. Polarization and density advection beat excitation are studied in combination with modulational response. Noise is driven by two-time flux correlation. While the effective zonal flow eddy viscosity can go negative, the zonal diffusivity is positive definite. There is no inverse cascade of density corrugation. The connection between avalanches and corrugations is discussed. The zonal cro…

How fast ions mitigate turbulence and enhance confinement in tokamak fusion plasmas

Nature Reviews Physics · 2025-03-26 · 16 citations

On how structures convey non-diffusive turbulence spreading

Nuclear Fusion · 2024-04-19 · 15 citations

Abstract We report on comprehensive experimental studies of turbulence spreading in edge plasmas. These studies demonstrate the relation of turbulence spreading and entrainment to intermittent convective density fluctuation events or bursts (i.e. blobs and holes). The non-diffusive character of turbulence spreading is thus elucidated. The turbulence spreading velocity (or mean jet velocity) manifests a linear correlation with the skewness of density fluctuations, and increases with the auto-corr…