UKAEA Journals

Showing 1 - 9 of 9 Journals Results
2019
UKAEA-CCFE-PR(19)28

We study the amplitude modulation of the radial electric field constructed from the  Langmuir probe plasma potential measurements at the edge of MAST. The Empirical Mode Decomposition technique is applied, which allows us to construct fluctuations on temporal scales of plasma turbulence, the Geodesic Acoustic Mode and these associated with the res…

Preprint Published
2017
CCFE-PR(17)60

Reciprocating Mach probe data is used to estimate the radial wave number of oscillatory zonal flows in Ohmic MAST plasma. An intermittent 10kHz mode is detected in the wavelet decomposition and windowed spectra of plasma potential fluctuations of the MAST tokamak edge plasma. Previously, this mode has been identified as a Geodesic Acoustic Mode (GA…

Preprint Published
2013

Following recent observations suggesting the presence of the geodesic acoustic mode (GAM) in ohmically heated discharges in the Mega Amp Spherical Tokamak (MAST) [J. R. Robinson et al., Plasma Phys. Controlled Fusion 54, 105007 (2012)], the behaviour of the GAM is studied numerically using the two fluid, global code CENTORI [P. J. Knight et al. Com…

Published
2010

The impact of Resonant Magnetic Perturbations (RMPs) on the edge of MAST L-mode plasmas is studied using a mid-plane reciprocating probe equipped with a Gundestrup probe head. A strong impact on the characteristics of the ion saturation current fluctuations is observed just inside the separatrix, with a broadening of the power spectrum and an asymm…

Published
2010

The effect of finite Larmor radius on the transport of passive charged test particles moving in turbulent electrostatic fields is investigated. The turbulent field is governed by a flexible model which is able to produce turbulence where zonal flows are damped or free to self-generate. A subtle interplay between trapping in small scale vortices and…

Published
2004

Previous observations that suggest a substantial role for nondiffusive energy transport in tokamaks subjected to off-axis electron cyclotron heating (ECH) are compared to the output from a sandpile model. The observations considered include local and global aspects of temperature profile evolution in the DIII-D [for example, C. C. Petty and T. C. L…

Published
2001

Confinement phenomenology characteristic of magnetically confined plasmas emerges naturally from a simple sandpile algorithm when the parameter controlling redistribution scale length is varied. Close analogs are found for enhanced confinement, edge pedestals, and edge localized modes (ELMs), and for the qualitative correlations between them. These…

Published
2001

An avalanche or ‘‘sandpile’’ model is discussed that generalizes the original self-organized criticality avalanche model of Bak, Tang, and Wiesenfeld [Phys. Rev. Lett. 59 , 381 (1987)] to include spatially extended local redistribution. A single control parameter specifies the spatial extent of local redistribution when the critical gradien…

Published