Comparative Study of FRC and High-β ST in TS-3/4 Merging Experiments
Abstract
The novel merging formation of FRC has been developed at Univ. Tokyo by use of counterhelicity merging of two spheromaks (Y. Ono et al., Phys. Plas. 4), 1953, (1997).. This unique method has various advantages over conventional θ-pinch formation: (1) slow formation, (2) stable and highly-efficient formation (3) large ion heating power of merging (4) current drive of FRC by an ohmic heating coil and by continuous merging, triggering construction of SPIRIT in PPPL and TS-4 in Univ. Tokyo. This paper addresses two important issues extended from this technique: (1) how the produced FRCs are related to high-β STs (spherical tokamak) in 2nd stability, (2) how different equilibrium and stability of the FRCs are from those of low-β spheromaks and STs. An important finding is that the produced FRC is transformed stably into high-β STs in 2nd stability by applying external toroidal field B_t,ext. The toroidal field was observed to vanish around magnetic axis after the B_t,ext application, indicating formation of diamagnetic ST. The hollow current profile of FRC was maintained during the equilibrium transition, eliminating a need for difficult hollow-current-formation process during conventional start-up discharge for high-β ST. Stability limit against the ballooning modes will be studied using this high-β ST formation technique.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1998
- Bibcode:
- 1998APS..DPP.G4S49O