Influence of beam orbit loss on radial electric field in NBI heated heliotron/torsatrons
- National Institute for Fusion Science, Nagoya (Japan)
Experiments with tangental NBI heating in the CHS (l = 2, m = 8 heliotron device, NIFS) have shown the strong negative radial electric field and significant reduction of thermal diffusivity in the plasma periphery. In non-axisymmetric configurations the radial electric field could be determined by the ambipolarity condition and the large positive ion radial flux or negative electron flux is considered to enhance the observed negative radial electric field. Recently, we have shown the large drift orbit deviation of tangentially injected NBI particle from the original magnetic surface to occur the prompt orbit loss in the CHS. This loss flux would enhance the negative radial electric field. In this paper we study the beam orbit loss effects on the radial electric field in heliotron/torsatrons numerically solving the time development of radial electric field with the neoclassical radial particle fluxes and the beam orbit loss flux calculated by the Monte-Carlo simulation code. We find an enhancement of the strong negative radial electric field at the periphery due to the radial flux of escaping beam ions in the weak magnetic field. Thus we have shown that the large negative electric field observed in the CHS would be enhanced by loss of beam ions.
- OSTI ID:
- 489523
- Report Number(s):
- CONF-960354--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Dynamic Behavior of Potential in the Plasma Core of the CHS Heliotron/Torsatron
Electric field profile of a Compact Helical System Heliotron/Torsatron plasma with tangential neutral beam injection