COAXIAL HELICITY INJECTION CURRENT DRIVE ON THE NSTX AND HIT II SPHERICAL TORII
Conference
·
OSTI ID:1022034
- University of Washington, Seattle
- ORNL
The favorable properties of the ST arise from its very small aspect ratio. However, small aspect ratio devices have very restricted space for a substantial solenoid, which restricts the inductive pulse duration. This makes sustained non-inductive operation necessary for the success of the ST concept. Furthermore, entirely removing the central solenoid would simplify the ST design and allow access to the lowest possible aspect ratio. This requires the demonstration of plasma creation without the use of the central solenoid. Coaxial helicity injection (CHI) is a promising candidate for initial plasma generation and for edge current drive during the sustained phase. CHI can produce and sustain non-inductive discharges with up to 360 kA toroidal current in the National Spherical Torus Experiment (NSTX, R = 0.85 m, a = 0. 67 m, B{sub 0} = 0.3 T) at the Princeton Plasma Physics Laboratory and up to 250 kA in the Helicity Injected Torus experiment (HIT-II, R = 0.3 m, a = 0.2 m, B{sub 0} = 0.5 T) at the University of Washington. Both experiments have two toroidal insulators, located at the top (absorber) and bottom (injector) of the central column. (The insulators are outboard on NSTX, inboard on HIT-II.) This allows a voltage to be applied to the central column, while external coils provide a magnetic flux 'footprint' to span the two electrodes. Current flowing along this flux expands the flux into the vessel volume. Such edge driven current can redistribute itself throughout the volume via non-axisymmetric relaxation mechanisms.
- Research Organization:
- Oak Ridge National Laboratory (ORNL)
- Sponsoring Organization:
- SC USDOE - Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1022034
- Country of Publication:
- United States
- Language:
- English
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