Plasma rotation and transport in MAST spherical tokamak

, , , , , , , , and

Published 28 April 2011 2011 IAEA, Vienna
, , Citation A.R. Field et al 2011 Nucl. Fusion 51 063006 DOI 10.1088/0029-5515/51/6/063006

0029-5515/51/6/063006

Abstract

The formation of internal transport barriers (ITBs) is investigated in MAST spherical tokamak plasmas. The relative importance of equilibrium flow shear and magnetic shear in their formation and evolution is investigated using data from high-resolution kinetic- and q-profile diagnostics. In L-mode plasmas, with co-current directed NBI heating, ITBs in the momentum and ion thermal channels form in the negative shear region just inside qmin. In the ITB region the anomalous ion thermal transport is suppressed, with ion thermal transport close to the neo-classical level, although the electron transport remains anomalous. Linear stability analysis with the gyro-kinetic code GS2 shows that all electrostatic micro-instabilities are stable in the negative magnetic shear region in the core, both with and without flow shear. Outside the ITB, in the region of positive magnetic shear and relatively weak flow shear, electrostatic micro-instabilities become unstable over a wide range of wave numbers. Flow shear reduces the linear growth rates of low-k modes but suppression of ITG modes is incomplete, which is consistent with the observed anomalous ion transport in this region; however, flow shear has little impact on growth rates of high-k, electron-scale modes. With counter-NBI ITBs of greater radial extent form outside qmin due to the broader profile of E × B flow shear produced by the greater prompt fast-ion loss torque.

Export citation and abstract BibTeX RIS

Access this article

The computer you are using is not registered by an institution with a subscription to this article. Please choose one of the options below.

Login

IOPscience login

Find out more about journal subscriptions at your site.

Purchase from

Article Galaxy
CCC RightFind

Purchase this article from our trusted document delivery partners.

Make a recommendation

To gain access to this content, please complete the Recommendation Form and we will follow up with your librarian or Institution on your behalf.

For corporate researchers we can also follow up directly with your R&D manager, or the information management contact at your company. Institutional subscribers have access to the current volume, plus a 10-year back file (where available).

10.1088/0029-5515/51/6/063006