Formation and sustainment of a 250 kA tokamak by coaxial helicity injection
- Univ. of Washington, Seattle, WA (United States). Aeronautics and Energetics Research Program
Steady-state tokamak fusion reactors require an efficient method of current drive. 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}. Coaxial helicity injection (CHI) current drive utilizes plasma relaxation processes to drive current carried by the bulk population, allowing the reactor efficiency to remain near ohmic. 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. Magnetic helicity is proportional to the product of linked flux, which in a tokamak is the toroidal flux times the poloidal flux. Relaxation occurs on reconnection time scales where helicity is approximately constant. Helicity decays on resistive time scales, and is replenished by CHI. CHI is used to produce low-aspect-ratio tokamaks with toroidal currents reaching 250 kA and sustained over 140 kA for many resistive diffusion times. To allow longer operation times and poloidal flux control, the 1 cm thick copper shell is being replaced with a 3 mm thick stainless steel shell. Poloidal field coils will be mounted on the shells, and will use poloidal flux loops to feedback control the equilibrium. The poloidal flux shape is programmable, and can be operated to provide transformer inductive current drive with up to 50 mWb flux swing.
- DOE Contract Number:
- FG06-90ER54095
- OSTI ID:
- 178192
- Report Number(s):
- CONF-950612--; ISBN 0-7803-2669-5
- Country of Publication:
- United States
- Language:
- English
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