EXPERIMENTAL INTERPRETATION OF IDEAL MHD BETA LIMITS
It is often assumed that the non-linear effects of ballooning modes will cause initially arbitrary plasma profiles to become asymptotically optimum as beta is raised, leading to some form of soft saturation in experimentally observed beta values. A similar type of saturation might be expected with resistive pressure driven modes, for which the ideal MHD analyses may provide the underlying trends. In either case it seems reasonable to look for a beta scaling which implies progressive saturation to an ideal limit rather than simplistic power law scaling. Using a slightly modified version of the GA beta limit formula (accounting for profile effects) such a law has been fitted to DIII MHD equilibrium data, resulting in 1/beta-c appears in the exponent since the physics should not be aware of the ideal limit as beta O, and the 2/3 & 3/2 indices arise from the technique chosen to reproduce the observed power dependence of beta. DIII did not address size scaling but matching to ISX-B data suggests a**2, Ra or R**2. Inclusion of DITE data leads to the choice or Ra. The predictions of this first attempt at such a law are compared with experimental data in Figs 2, 3 and 4, with encouraging results.
Bibliographic Reference: 2ND WORKSHOP EUROPEAN TOKAMAK PROGRAMME, SAULX-LES-CHARTREUX (FRANCE), NOV. 30-DEC. 2, 1983 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32872 ORA
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Record Number: 1989125008200 / Last updated on: 1987-01-01
Available languages: en