ELFT HÍRADÓ

[Sandor Zoletnik <zoletnik AT rmki.kfki.hu>]

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*              A KFKI-RMKI rendkivuli szeminariuma                  *
*                                                                   *
*        A. Field UKAEA, Mega Amp Spherical Tokamak (MAST) team     *
*    Transport and turbulence studies on the MAST spherical tokamak *
*                                                                   *
*                2005 oktober 13 (csutortok)  9:30                  *
*           KFKI-RMKI  2. epulet 1. emelet mediaterem               *
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Kivonat:

The spherical tokamak (ST), pioneered at Culham with the START device, has
good confinement at high-beta (ratio of plasma pressure to magnetic
pressure)  and hence offers the potential for a compact burning plasma
device. This approach to magnetic confinement is being pursued at Culham,
both in support of the conventional tokamak programme, which is focussed
towards realisation of the International Tokamak Experimental Reactor
(ITER), and to investigate the potential role of the ST in a 'fast track'
approach to fusion power.

The MAST device, with up to 2 MA plasma current, now operating at Culham
is being used to develop this concept as well as allowing physical models
to be tested under the extreme parameters of the ST. The device is
equipped with a range of diagnostics providing measurements of the plasma
parameters required for detailed investigation of the plasma transport. As
an example, results from experiments will be presented in which turbulent
energy losses are suppressed almost to the irreducible level due to
collisions.

A physical understanding of the processes that give rise to anomalous
transport would strengthen confidence in performance predictions for
future devices which are currently based on empirical scalings. With this
aim both gyro-kinetic models (GS2) of micro-turbulence at scales of the
ion or electron gyro-radius and two-fluid models of meso-scale MHD
turbulence (CUTIE) are being used to predict levels of transport in
MAST-like equilibria for comparison with experiment. More stringent tests
of these simulations against experiment are envisaged through comparison
with both the empirical scaling transport coefficients with dimensionless
parameters (beta, rho-star, nu-star, Mach number, etc) and with measured
turbulence characteristics. With the latter aim in mind, the various
techniques for turbulence diagnostics have been reviewed and are currently
being assessed for their suitability for implementaion on the MAST device.

This work was funded jointly by the UK Engineering and Physical Sciences 
Research Council and by EURATOM.