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A correlation has been established between the improvement of the energy confinement time observed in some plasma regimes on the DIII-D tokamak (VH modes and shear reversed discharges) and a geometrical characteristic of the plasma column which multiplies the moment of inertia of the magnetic configuration.
Such a quantity is generated by the compression that the flux tubes suffer going from the external to the internal part of the torus. Therefore the configurations in which the module of the total magnetic field is more constant upon the magnetic surfaces (near omnigeneous configurations) show a lower value of the moment of inertia.
The radial electric field, or, at least, his radial derivative, is invoked by many authors as a principal factor in reducing the turbulence (and so the anomalous transport) in magnetically confined plasmas. In particular, on the DIII-D machine, the highly elongated and trianglular plasma discharges that evolve toward the VH-mode show a lower value of the geometric characterised quantity and a higher level of the radial electric field; also the shear reversed profiles tend to lower the geometric value in the central region of the plasma column, driving towards very high values of the electric field within the reversal region. .

Additional information

Authors: ALLANDIO F, ENEA, Centro Ricerche Energia Frascati, Roma (IT);MICOZZI P, ENEA, Centro Ricerche Energia Frascati, Roma (IT)
Bibliographic Reference: Report: RT/ERG/FUS/95/21 (1995) 21pp.
Availability: Available from Servizio Edizioni Scientifiche, ENEA Centro Ricerche Frascati, CP 65, 00044 Frascati, Roma (IT)
ISBN: ISSN 1120 5563
Record Number: 199610993 / Last updated on: 1996-09-30
Original language: en
Available languages: en