Profile Study of Oblate FRC in TS-3 Merging Experiment
Abstract
Novel merging formation of FRC has been developed in the TS-3 merging experiment. When two spheromaks with opposing magnetic helicities (and toroidal field) are axially collided, their counterhelicity reconnection accelerates and heats selectively plasma ions from 10eV up to 200eV, forming an oblate FRC with plasma β as high as 0.7-1. Recently, we placed two sets of 2-D magnetic probe arrays on the r-z and r-θ planes , 1-D electrostatic probe array and 1-D polichrometer in the radial and axial directions. These measurements lead us to detailed profile study of the produced FRC equilibrium and induced global instabilities. During the equilibrium transition from spheromak to FRC, the magnetic axis was observed to shift outward, in agreement with increase in plasma β. Toroidal current density of the produced FRC tends to peak outside of the magnetic axis and its ion temperature and electron density also peak strongly and weakly around the magnetic axis. These results were consistent with our recent equilibrium calculations of the oblate FRCs, revealing their unique equilibria with high h factor (=(j_t/r)_r=R/<j_t/r>) and high X_s. Detailed evolutions of magnetic field, current density, plasma pressure profiles will be presented during the FRC equilibrium transition and also during its OH current drive. To investigate relationship between our oblate FRCs and conventional FRCs, the plasma elongation and current profile were actively varied by use of the OH current amplification up to factor 2-3.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1997
- Bibcode:
- 1997APS..DPPhTP129U