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The near separatrix region in tokamaks provides a new length scale parameter x(0) = (-d ln p(0)/dx)(-1) being of the order of several Larmor radii. Modified drift and interchange instabilities occur in this region due to longitudinal losses. The related turbulence gives rise to perpendicular transport and regulates the width x(0). The H-mode is set up when the shear flow stabilises these instabilities. The L-H power threshold depends strongly on the longitudinal loss mechanism. Classical thermal conduction provides a threshold scaling similar to the experimentally observed scaling, but the free-streaming loss yields a cubic dependence on B(0).

Additional information

Authors: CORDEY G, JET Joint Undertaking, Abingdon, Oxon. (GB);KERNER W, JET Joint Undertaking, Abingdon, Oxon. (GB);POGUTSE O, JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(94)66 EN (1994) 16 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199510457 / Last updated on: 1995-04-11
Original language: en
Available languages: en