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Oscillating-field current-drive experiments in a reversed field pinch.
K J McCollam1, A P Blair, S C Prager
1University of Wisconsin, Madison, Wisconsin 53706, USA.
Physical Review Letters
|February 21, 2006
Summary
Oscillating-field current drive (OFCD) drives plasma current using oscillating voltages. Maximum current generation was not found at peak helicity injection rates, indicating complex plasma dynamics.
Area of Science:
- Plasma physics
- Fusion energy research
- Magnetohydrodynamics
Background:
- Steady-state plasma current sustainment is crucial for fusion energy.
- Magnetic helicity injection offers a method for non-inductive current drive.
- Oscillating-field current drive (OFCD) is an advanced technique for injecting magnetic helicity.
Purpose of the Study:
- To investigate the effectiveness of OFCD in driving toroidal plasma current.
- To determine the optimal phase relationship between applied voltages for maximum current drive.
- To analyze the impact of OFCD on plasma stability and energy dissipation.
Main Methods:
- Implementing OFCD in conjunction with standard toroidal induction on the Madison Symmetric Torus.
- Varying the phase between oscillating poloidal and toroidal loop voltages.
- Measuring the resulting toroidal current, magnetic fluctuations, and dissipated power.
Main Results:
- OFCD contributed approximately 10% to the total toroidal current.
- The maximum added current did not align with the phase of maximum helicity injection rate.
- Observed effects of OFCD on magnetic fluctuations and power dissipation were quantified.
Conclusions:
- OFCD is a viable method for supplementing toroidal current in plasmas.
- The phase dependence of OFCD suggests complex interactions beyond simple helicity injection rates.
- Further research is needed to optimize OFCD for fusion applications.