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During the H-mode experiments with ICRF heating on JET it was observed that the influxes of deuterium and impurities can modify the quality of both the energy and particle confinement substantially. In particular a Low Particle Confinement (LPC) H-mode was triggered either by deuterium input into the X-point region or as a result of a moderate impurity influx into the plasma boundary. In the LPCH-mode the particle confinement is at least 3 times less than in a normal H-mode. The energy, on the other hand, only decreases by approximately 20%. The electron density, the deuterium density and the radiated power are also less than in a normal H-mode. However the deuterium dilution reaches a steady-state. The H-mode duration is extended by the LPC-phase to 2.8 s and is limited only by the length of the heating pulse. The LPCH-mode particle confinement is linked to L-mode like particle diffusion within values of the radius ratio between 0.5 and 0.8, and the H-mode like barrier, due to large V/D values in the plasma boundary. This mode has the potential for substantially extending the H-mode phase to make it more reactor relevant.

Additional information

Authors: BURES M ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB);MATTIOLI M, CEA, CEN Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Report: JET-P(91)61 EN (1991) 30 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199210397 / Last updated on: 1994-12-02
Original language: en
Available languages: en