Magnetohydrodynamic simulations of direct current helicity injection for current drive in tokamaks

C. R. Sovinec; S. C. Prager

doi:10.1063/1.871759

Magnetohydrodynamic simulations of direct current helicity injection for current drive in tokamaks

C. R. Sovinec, S. C. Prager

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Abstract

Magnetohydrodynamic (MHD) computations of direct current (DC) helicity injection for tokamak-like configurations show current drive with no "loop voltage" in a resistive, pressureless plasma. Self-consistently induced, hollow current profiles are unstable to resistive modes that partially relax the profile through the MHD dynamo mechanism. The resulting current profiles remain quite hollow, however, and tokamaks are not generated. The current driven by the fluctuations leads to closed contours of average poloidal flux, but the 1% fluctuation level is large enough to produce a region of stochastic magnetic field. A limited Lundquist number (S) scan from 2.5×10³ to 2×10⁴ indicates that both the fluctuation level and current profile relaxation increase with S. A simple quasilinear power scaling is consistent with these results at low S and suggests that at larger S. the fluctuation level decreases.

Original language	English (US)
Pages (from-to)	1038-1046
Number of pages	9
Journal	Physics of Plasmas
Volume	3
Issue number	3
DOIs	https://doi.org/10.1063/1.871759
State	Published - Mar 1996

All Science Journal Classification (ASJC) codes

Condensed Matter Physics

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10.1063/1.871759

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title = "Magnetohydrodynamic simulations of direct current helicity injection for current drive in tokamaks",

abstract = "Magnetohydrodynamic (MHD) computations of direct current (DC) helicity injection for tokamak-like configurations show current drive with no {"}loop voltage{"} in a resistive, pressureless plasma. Self-consistently induced, hollow current profiles are unstable to resistive modes that partially relax the profile through the MHD dynamo mechanism. The resulting current profiles remain quite hollow, however, and tokamaks are not generated. The current driven by the fluctuations leads to closed contours of average poloidal flux, but the 1% fluctuation level is large enough to produce a region of stochastic magnetic field. A limited Lundquist number (S) scan from 2.5×103 to 2×104 indicates that both the fluctuation level and current profile relaxation increase with S. A simple quasilinear power scaling is consistent with these results at low S and suggests that at larger S. the fluctuation level decreases.",

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AU - Sovinec, C. R.

AU - Prager, S. C.

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N2 - Magnetohydrodynamic (MHD) computations of direct current (DC) helicity injection for tokamak-like configurations show current drive with no "loop voltage" in a resistive, pressureless plasma. Self-consistently induced, hollow current profiles are unstable to resistive modes that partially relax the profile through the MHD dynamo mechanism. The resulting current profiles remain quite hollow, however, and tokamaks are not generated. The current driven by the fluctuations leads to closed contours of average poloidal flux, but the 1% fluctuation level is large enough to produce a region of stochastic magnetic field. A limited Lundquist number (S) scan from 2.5×103 to 2×104 indicates that both the fluctuation level and current profile relaxation increase with S. A simple quasilinear power scaling is consistent with these results at low S and suggests that at larger S. the fluctuation level decreases.

AB - Magnetohydrodynamic (MHD) computations of direct current (DC) helicity injection for tokamak-like configurations show current drive with no "loop voltage" in a resistive, pressureless plasma. Self-consistently induced, hollow current profiles are unstable to resistive modes that partially relax the profile through the MHD dynamo mechanism. The resulting current profiles remain quite hollow, however, and tokamaks are not generated. The current driven by the fluctuations leads to closed contours of average poloidal flux, but the 1% fluctuation level is large enough to produce a region of stochastic magnetic field. A limited Lundquist number (S) scan from 2.5×103 to 2×104 indicates that both the fluctuation level and current profile relaxation increase with S. A simple quasilinear power scaling is consistent with these results at low S and suggests that at larger S. the fluctuation level decreases.

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Magnetohydrodynamic simulations of direct current helicity injection for current drive in tokamaks

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