Global Confinement and Discrete Dynamo Activity in the MST Reversed-field Pinch

S. Hokin, A. Almagri, S. Assadi, J. Beckstead, G. Chartas, N. Crocker, M. Cudzinovic, D. Den Hartog, R. Dexter, D. Holly, S. Prager, T. Rempel, J. Sarff, E. Scime, W. Shen, C. Spragins, C. Sprott, G. Starr, M. Stoneking, and C. Watts
Department of Physics, University of Wisconsin, Madison, Wisconsin 53706
R. Nebel
Los Alamos National Laboratory, Los Alamos, New Mexico 87545
(Received 10 December 1990; accepted 1 April 1991)

ABSTRACT

Results obtained on the Madison Symmetric Torus (MST) reversed-field pinch [Fusion Technol. 19, 131 (1991)] after installation of the design poloidal field winding are presented. Values of beta_te0 = 2mu₀n_e0T_e0/B_p(a) ~ 12% are achieved in low-current (I = 220 kA) operation; here n_e0 and T_e0 are central electron density and temperature, and B_p(a) is the poloidal magnetic field at the plasma edge. An observed decrease in beta_te0 with increasing plasma current may be due to inadequate fueling, enhanced wall interaction, and growth of a radial field error at the vertical cut in the shell at high current. Energy confinement time varies little with plasma current, lying in the range of 0.5-1.0 msec. Strong discrete dynamo activity is present, characterized by the coupling of m = 1, n = 5-7 modes leading to an m = 0, n = 0 crash (m and n are poloidal and toroidal mode numbers). The m = 0 crash generates toroidal flux and produces a small (2.5%) increase in plasma current.

Ref: S. Hokin, A. Almagri, S. Assadi, J. Beckstead, G. Chartas, N. Crocker, M. Cudzinovic, D. Den Hartog, R. Dexter, D. Holly, S. Prager, T. Rempel, J. Sarff, E. Scime, W. Shen, C. Spragins, C. Sprott, G. Starr, M. Stoneking, C. Watts and R. Nebel, Phys. Fluids B 3, 2241-2246 (1991)

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