S. Saarelma J.W. Connor P. Bilkova P. Bohm A.R. Field L. Frassinetti R. Fridstrom A. Kirk JET Contributors*
The neutral ionisation model proposed by R J Groebner et al. (Phys Plasmas 9 2134 (2002)) to determine the plasma density profile in the H-mode pedestal, extended to include charge exchange processes in the pedestal stimulated by the ideas of Mahdavi et al. ((Phys Plasmas 10 3984 (2003)). The model is then tested a…
PreprintS.M. Kaye J.W. Connor C.M. Roach
In this paper, we review the confinement and transport properties observed and predicted in low aspect ratio tokamaks, or spherical tokamaks (STs), which can depart significantly from those observed at higher aspect ratio. In particular, thermal energy confinement scalings show a strong, near linear dependence of energy confinement time on toroidal…
Preprint PublishedD. Brunetti C. J. Ham S. Saarelma J. P. Graves J. W. Connor A. Kleiner
The impact of plasma shaping through magnetic well modifications on the stability of resistive ballooning modes in tokamaks is analysed, also including finite diamagnetic flows. Various limiting cases of the dispersion relation, obtained by matching the averaged ballooning equation across the ideal and resistive layers, are analysed. It is found th…
Preprint PublishedC J Ham A Bokshi D Brunetti G Bustos Ramirez B Chapman J W Connor D Dickinson A R Field J P Graves T Kiviniemi S Leerink B McMillan S Newton S Pamela C M Roach S Saarelma J Simpson S F Smith P Strand A Virtanen the JET Contributors*
The pedestal plays an important role in determining the confinement in tokamak H-mode plasmas. However, the steep pressure gradients in this transport barrier also lead to edge localized modes (ELMs) [1]. There is good understanding of the pedestal in type I ELM regimes [2], however, type I ELMs are known to damage plasma facing components and f…
Preprint PublishedJ W Connor C J Ham R J Hastie A Zocco
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 PublishedK. Imada H. R. Wilson J. W. Connor A. Dudkovskaia P. Hill
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 PublishedJW Connor RJ Hastie C Marchetto CM Roach
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 PublishedJ. W. Connor R. J. Hastie P. Helander
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 PublishedJ.W. Connor C.J. Ham R.J. Hastie
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