Coaxial helicity injection current drive in a low-aspect ratio tokamak
- Univ. of Washington, Seattle, WA (United States)
Economical steady-state tokamak reactors require both an efficient method of current drive and high beta operation. Proposed tokamak current-drive methods (neutral beam, electron cyclotron, and lower hybrid) drive tail particles and have reactor power efficiencies of approximately 10{sup {minus}3}. The NSTX ultra-low aspect ratio tokamak shows global betas up to 44%. Coaxial helicity injection (CHI) current drive uses plasma relaxation processes to drive current carried by the bulk population, allowing the reactor efficiency to remain near ohmic. No transformer is required, thus CHI-driven tokamaks can be constructed with a low aspect ratio. The Helicity Injected Tokamak (HIT) produces a steady-state toroidal current by driving an edge current and allowing relaxation to drive current throughout the plasma. To allow longer operation times and poloidal flux control, the 1 cm thick copper shell is being replaced with 3--6 mm thick stainless steel shells. The poloidal flux shape is programmable, and can be operated to provide transformer current drive with up to 50 mWb flux swing. This unique configuration, HIT-II, allows comparison of CHI and inductive current drive in the same device, while studying the effects of current profile and relaxation on confinement.
- OSTI ID:
- 427995
- Report Number(s):
- CONF-960634--
- Country of Publication:
- United States
- Language:
- English
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