Plasma behaviour at high β and high density in the Madison Symmetric Torus RFP

M.D. Wyman, B.E. Chapman, J.W. Ahn, A.F. Almagri, J.K. Anderson, F. Bonomo, D.L. Brower, S.K. Combs, D. Craig, D.J. Den Hartog, B.H. Deng, W.X. Ding, F. Ebrahimi, D.A. Ennis, G. Fiksel, C.R. Foust, P. Franz, S. Gangadhara, J.A. Goetz, R. O'ConnellS.P. Oliva, S.C. Prager, J.A. Reusch, J.S. Sarff, H.D. Stephens, T. Yates

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Abstract

Pellet fuelling of improved confinement Madison Symmetric Torus (MST) plasmas has resulted in high density and high plasma beta. The density in improved confinement discharges has been increased fourfold, and a record plasma beta (βtot= 26%) for the improved confinement reversed-field pinch (RFP) has been achieved. At higher β, a new regime for instabilities is accessed in which local interchange and global tearing instabilities are calculated to be linearly unstable, but experimentally, no severe effect, e.g., a disruption, is observed. The tearing instability, normally driven by the current gradient, is driven by the pressure gradient in this case, and there are indications of increased energy transport (as compared with low-density improved confinement). Pellet fuelling is also compared with enhanced edge fuelling of standard confinement RFP discharges for the purpose of searching for a density limit in MST. In standard-confinement discharges, pellet fuelling peaks the density profile where edge fuelling cannot, but transport appears unchanged. For a limited range of plasma current, MST discharges with edge fuelling are constrained to a maximum density corresponding to the Greenwald limit. This limit is surpassed in pellet-fuelled improved confinement discharges. © 2009 IAEA.
Original languageEnglish
Article number015003
Pages (from-to)-
JournalNuclear Fusion
Volume49
Issue number1
DOIs
Publication statusPublished - 1 Jan 2009
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Wyman, M. D., Chapman, B. E., Ahn, J. W., Almagri, A. F., Anderson, J. K., Bonomo, F., ... Yates, T. (2009). Plasma behaviour at high β and high density in the Madison Symmetric Torus RFP. Nuclear Fusion, 49(1), -. [015003]. https://doi.org/10.1088/0029-5515/49/1/015003