LIMITING-B INVESTIGATIONS AT LOW COLLISIONALITY
Electron cyclotron heating has been employed at high power densities on TOSCA (R/a greater or equal 3.5, R = 0.3m) and CLEO (R/a = 7, R = 0.9 m) to investigate the limiting beta value in Tokamaks of differing aspect ratios. The influence of both q and a helical field were studied. The studies have been principally conducted at the second harmonic at 28 GHz and 60 GHz and with power levels of up to 200 kW. During the heating on both devices the ratio of absorbed radiofrequency (RF) power to Ohmic heating power can be larger than 10, the electron temperature can be above 3 keV and the collisionality such that nu***-e <= 0.01. As the power is increased, beta saturates indicating a decrease in confinement which is accompanied by an increase in the magnetic fluctuation level. Average beta values of 0.2% have been achieved in an l = 3 helical configuration in CLEO. Profile modification experiments show the suppression or enhancement of sawtooth activity and produce m = 2 activity, which may lead to a disruption.
Bibliographic Reference: 10TH INTERNATIONAL CONFERENCE ON PLASMA PHYSICS AND CONTROLLED NUCLEAR FUSION RESEARCH, LONDON (UK), SEPT. 12- 19, 1984 PUBLISHED BY IAEA (WIEN) AUSTRIA, 1985, VOL. 1, PP. 205-215
Record Number: 1989124026600 / Last updated on: 1987-01-01
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