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The VH-mode regime of high confinement has been observed in both DIII-D and JET. VH-mode is characterised by thermal confinement twice that seen in H-mode, with the edge transport barrier penetrating deeper into the plasma. Two mechanisms have been identified as important in achieving this high level of confinement. Expansion of the velocity shear turbulence suppression zone is important in allowing reductions in local transport, while access to the second ballooning stability regime in the edge allows avoidance or elimination of ELMs which impede the confinement improvement. The high performance phase of these discharges is usually terminated by an MHD event which removes energy from a large portion of the plasma cross-section, and is followed by an H-mode phase.

Additional information

Authors: GREENFIELD C M ET AL., General Atomics, San Diego, California (US);BALET B ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB);DOYLE E J, University of California at Los Angeles (US);RETTIG C L, University of California at Los Angeles (US);KONOSHIMA S, Japan Atomic Energy Research Institute (JP)
Bibliographic Reference: Report: JET-P(93)75 EN (1993) 14 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199311462 / Last updated on: 1994-11-28
Original language: en
Available languages: en