UKAEA Journals

Showing 1 - 10 of 48 Journals Results
2018
UKAEA-CCFE-PR(19)09

Kinetic treatments of drift tearing modes that match an inner, resonant layer solution to an external MHD solution, can fail to match the ideal MHD boundary condition on the parallel electric field. In this paper we demonstrate how consideration of ion sound and ion Landau damping effects achieves this, placing the theory on a firm footing. The …

Preprint Published
2018
UKAEA-CCFE-PR(18)41

A new drift-kinetic theory of the ion response to magnetic islands in tokamak plasmas is presented. Small islands are considered, with widths w much smaller than the plasma radius r, but comparable to the trapped ion orbit width ρ_bi. An expansion in w/r reduces the system dimensions from five down to four. In the absence of an electrostatic poten…

Preprint Published
2018
UKAEA-CCFE-PR(18)20

Starting from expressions in Connor et al. (1988), we derive a one-dimensional tearing equation similar to the approximate equation obtained by Hegna & Callen (1994); Nishimura et al. (1998), but for more realistic toroidal equilibria. The intention is to use this approximation to explore the role of steep H-mode pedestals, bootstrap currents a…

Preprint Published
2017
CCFE-PR(17)51

A set of layer equations for determining the stability of semi-collisional tearing modes in an axisymmetric torus, incorporating neoclassical physics, in the small ion Larmor radius limit is provided. These can be used as an inner layer module for inclusion in numerical codes that asymptotically match the layer to toroidal calculations of the teari…

Preprint Published
2016
CCFE-PR(17)19

An explanation of the observed improvement in H-mode pedestal characteristics with increasing core plasma pressure or poloidal beta, pol b , as observed in MAST and JET, is sought in terms of the impact of the Shafranov shift, D¢ , on ideal ballooning MHD stability. To illustrate this succinctly, a self-consistent treatment of the low magnetic she…

Preprint Published
2015
CCFE-PR(15)45

The role of anisotropic thermal diffusivity on tearing mode stability is analysed in general toroidal geometry following similar techniques to Glasser et al [A H Glasser, et al, Phys. Fluids 18 (1975) 875], although a stronger ordering of the plasma compressibility is required. Resistive layer equations are obtained for a resistive MHD model with a…

Preprint Published
2014

We investigate the linear theory of the ion-temperature-gradient (ITG) mode, with the goal of developing a general understanding that may be applied to stellarators. We highlight the Wendelstein 7X (W7-X) device. Simple fluid and kinetic models that follow closely from existing literature are reviewed and two new first-principle models are presente…

Published
2014

We have extended our study of the competition between the drive and stabilization of plasma microinstabilities by sheared flow to include electromagnetic effects at low plasma ß (the ratio of plasma to magnetic pressure). The extended system of characteristic equations is formulated, for a dissipative fluid model developed from the gyrokinetic equ…

Published