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Relaxation in MFE Experiments
| Author: | Jarboe T. R. |
| Coauthor: | |
| Institution : | University of Washington |
| Abstract text: | It was first observed in ZETA (a large RFP) that a turbulent discharge would evolve to produce a stable configuration for periods of time. J. B. Taylor was able to explain this phenomenon as the equilibrium evolving to a state of minimum energy while conserving magnetic helicity. Helicity conservation is a powerful tool for understanding, controlling, and sustaining plasma. For example, it tells us the effects of plasma dynamics on plasma equilibrium evolution, the efficiency of formation and sustainment by helicity injection, and the likelihood that a formation method will be effective. It does not tell us details of the relaxations process, relaxation effects on energy transport, the impedance of helicity injectors, or how close to the minimum energy state relaxation will take the plasma. Detailed plasma physics understanding is required for this important additional information.
Properly shaped dynamo mode structures can give a net time-averaged Lorentz force on the electron fluid to cause current drive parallel to the mean fields in regions of low lambda (= moj/B) and anti-current drive in high lambda regions. The scaling of the required fluctuation amplitudes with plasma conditions will be discussed as well as the open question of the effects of relaxation on energy transport. Experimental results from RFPs, Spheromaks, and STs as well as computational results will be presented.
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