ECE MEASUREMENTS AND POWER MODULATION IN WENDELSTEIN VII-A
A fast multichannel heterodyne radiometer system has been installed at W VII-A which enables the simultaneous measurement of electron temperature at 8 different radii of the plasma column. While good agreement is found with Thomson Scattering and SX temperature measurements during NBI heated plasma discharges, characteristic deviations are found in those heated by ECR. The deviations are caused by suprathermal electrons homogeneously distributed between the limiter radii with density of about 1 % of the peak density of the thermalized electron bulk and averaged energy of about 6 keV as derived from detailed numerical simulation. Modulation experiments demonstrate a clear correlation between the transient development of the ECE signals caused by the suprathermal population and the observed plasma current, indicating that the current may be indeed carried by suprathermal electrons. In addition correlation with the appearance of a fast ion tail as observed by CX diagnostic and a signal identified to be a relict of parametric wave decay of the ECR heating 28 GHz line has been found. The correlation confirms the assumption that the fast ion tail is produced by wave decay of the X-mode of the heating wave into an ion heating lower hybrid wave and an electron Bernstein wave.
Bibliographic Reference: 5TH INTERNATIONAL WORKSHOP ON STELLARATORS, SCHLOSS RINGBERG, BAVARIA (GERMANY), SEPT. 24-28, 1984 VOL. II, PP. 449-462, EUR 9618 EN (1985) FS, VOL. I AND VOL. II, 787 P., BFR 3500 (BOTH VOLUMES), EUROFFICE, LUXEMBOURG, POB 1003
Record Number: 1989124113500 / Last updated on: 1987-01-01
Available languages: en