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The transition from L-mode to H-mode confinement is accompanied by formation of a narrow region of reduced energy and particle transport near the plasma edge. In the H-mode regime, the operation space of a tokamak is limited to a finite edge pressure gradient by the ballooning mode stability. Experimental verification of the scaling behaviour of the barrier, the pedestal density and temperature, as well as the pressure gradient limits achieved before onset of loss of confinement require measurement of edge gradients with high spatial resolution and accuracy. Edge gradient, pedestal value and barrier width delta were parameterized using a bi-linear fit of core and edge gradient, a non-linear fit of edge deviations from core gradient and a composite fit of the core and edge profile based on a tanh function.

Additional information

Authors: BREGER P ET AL, JET Joint Undertaking, Abingdon, Oxon (GB);FLEWIN C, University College London (GB);HAWKES N C, AEA Fusion, Culham Laboratory, Abingdon, Oxon (GB);PIETRZYK Z A, École Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CH)
Bibliographic Reference: Article: Proceedings of 24th EPS Conference on Controlled Fusion and Plasma Physics, Berchtesgaden 9-13 June 1997, pp. 69-72
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