Dynamo-free plasma in the reversed-field pinch: Advances in understanding the reversed-field pinch improved confinement mode

J. K. Anderson, J. Adney, A. Almagri, A. Blair, D. L. Brower, M. Cengher, B. E. Chapman, S. Choi, D. Craig, D. R. Demers, D. J.Den Hartog, B. Deng, W. X. Ding, F. Ebrahimi, D. Ennis, G. Fiksel, C. B. Forest, P. Franz, J. Goetz, R. W. HarveyD. Holly, B. Hudson, M. Kaufman, T. Lovell, L. Marrelli, P. Martin, K. McCollam, V. V. Mirnov, P. Nonn, R. O'Connell, S. Oliva, P. Piovesan, S. C. Prager, I. Predebon, J. S. Sarff, G. Spizzo, V. Svidzinski, M. Thomas, M. D. Wyman

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Generation and sustainment of the reversed field pinch (RFP) magnetic configuration normally relies on dynamo activity. The externally applied electric field tends to drive the equilibrium away from the relaxed, minimum energy state which is roughly described by a flat normalized parallel current density profile and is at marginal stability to tearing modes. Correlated fluctuations of magnetic field and velocity create a dynamo electric field which broadens the parallel current density profile, supplying the necessary edge current drive. These pervasive magnetic fluctuations are also responsible for destruction of flux surfaces, relegating the standard RFP to a stochastic-magnetic transport-limited device. Application of a tailored electric field profile (which matches the relaxed current density profile) allows sustainment of the RFP configuration without dynamo-driven edge current. The method used to ascertain that a dynamo-free RFP plasma has been created is reported here in detail. Several confinement improvements during the accompanying periods of low magnetic fluctuations are observed. Namely, the magnetic fluctuation level is reduced to the point where stochastic-magnetic transport is no longer the dominant process in the core and nested flux surfaces are restored in the core of the dynamo-free RFP.

Original languageEnglish (US)
Article number056118
Pages (from-to)1-7
Number of pages7
JournalPhysics of Plasmas
Volume12
Issue number5
DOIs
StatePublished - May 2005

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

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