title: L-H transition in the mega-amp spherical tokamak.
abstract: H-mode plasmas have been achieved on the MAST spherical tokamak at input power considerably higher than predicted by conventional threshold scalings. Following L- H transition, a clear improvement in energy confinement is obtained, exceeding recent international scalings even at densities approaching the Greenwald density limit. Transition is accompanied by an order-of-magnitude increase in edge-density gradient, a marked decrease in turbulence, the efficient conversion of internal electron Bernstein waves into free space waves, and the onset and saturation of edge poloidal rotation.
authors.affiliation: EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, OXON, OX14 3DB, United Kingdom.
authors.forename: R J
authors.initials: RJ
authors.lastname: Akers
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authors.lastname: Counsell
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authors.lastname: Cunningham
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authors.lastname: Dnestrovskij
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authors.initials: AR
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authors.lastname: Kirk
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authors.lastname: Korsholm
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authors.lastname: Martin
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authors.lastname: Meyer
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authors.lastname: Nightingale
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authors.lastname: Tournianski
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authors.lastname: Warrick