MEASURING DELTA' FROM ELECTRON-TEMPERATURE FLUCTUATIONS IN THE TOKAMAK FUSION TEST REACTOR

A method is developed for determining directly from experimental data the classical tearing mode stability parameter Delta'. Specifically, a n analytical fit function is derived for the electron temperature fluc tuations (<(T)over tilde (e)>) in the vicinity of a magnetic island. V alues of Delta' determined from the fit function parameters for m/n = 2/1, 3/2 and 4/3 modes (m and n are poloidal and toroidal mode numbers ) are obtained using the high resolution <(T)over tilde (e)> profile d ata from major radius shift (''jog'') experiments on the Tokamak Fusio n Test Reactor (TFTR) [D. Meade er al., Proceedings of the Internation al Conference on Plasma Physics and Controlled Nuclear Fusion. Washing ton, District of Columbia, 1990 (International Atomic Energy Agency, V ienna, 1991), Vol. I, pp. 9-24]. It is found that the n greater than o r equal to 2 modes have Delta' < 0. (C) 1998 American Institute of Phy sics.