Analysis of Ballooning Instability for Ultra High Beta Spherical Tokamaks in TS-3 Merging Experiment
Abstract
We have been investigating ultra-high beta characteristics of spherical tokamaks (ST) produced by merging and reconnection techniques of TS-3 ST/CT experiment[1]. Ballooning mode was found the most dangerous instability for the STs with volume-averaged beta value over 50formation, they were observed to stay stably or to collapse due to high-n mode activities, depending on their pressure and current profiles. The BALOO code[2] analyses of the experimentally obtained high-beta ST equilibria, clarified the conditions to reach the second stable region and to attain higher beta value. Their critical beta value was found to increase with localizing the pressure gradient and the poloidai current at the edge. When the plasma parameters reached at the second stable region, the critical beta value increased sharply. Using the BALOO code and experimentally obtained current/ pressure profiles, we are now studying effect of aspect ratio on the ballooning instability to conclude whether we can make realistic reactor design of second-stable STs. [1] Y. Ono et al., Phys. Plasmas 7, 1863 (2000), [2]R. L. Miller et al. Phys. Plasma 4, 1092 (1997).
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 2002
- Bibcode:
- 2002APS..DPPKP1100K