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The existence of unstable beta-induced temperature-gradient driven (BTG) eigenmodes in tokamaks is shown. The BTG eigenmodes can exist when the ion temperature gradient is positive and when the ratio of the ion pressure to the magnetic field pressure, beta(i), is larger than a critical value of the order of S(2)L(2)/q(2)R(2), provided the magnetic shear S is not too small (here L is the characteristic scale length of the ion temperature gradient, q is the safety factor and R is the major radius of tokamak). The eigenfrequency and the growth rate of the BTG eigenmodes are of the order of the ion transit frequency V(Tau i)/q, where V(Tau i) is the thermal velocity of ions.

Additional information

Authors: MIKHAILOVSKII A B, RSC Kurchatov Institute, Institute of Nuclear Fusion, Moscow (RU);SHARAPOV S E, JET Joint Undertaking, Abingdon, Oxon (GB)
Bibliographic Reference: Report: JET-P(98)18 EN (1998) 22pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (GB)
Record Number: 199811102 / Last updated on: 1998-09-28
Original language: en
Available languages: en