Steady-state tokamak discharge via dc helicity injection

Ono, M.; Greene, G. J.; Darrow, D. S.; Forest, C.B.; Park, H.; Stix, Thomas H.

doi:10.1103/physrevlett.59.2165

Cited by 89 publications

(48 citation statements)

References 14 publications

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“…And last, in all computations we have set j = 0 at the plasma outer boundary. Thanks to turbulent diffusion, however, a nonzero current at the plasma edge could potentially sustain a significant fraction of the plasma current [51].…”

Section: Discussionmentioning

confidence: 99%

Turbulent contributions to Ohm's law in axisymmetric magnetized plasmas

Chavdarovski

Gatto

2017

Physics of Plasmas

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Abstract.The effect of magnetic turbulence in shaping the current density in axisymmetric magnetized plasma is analyzed using a turbulent extension of Ohm's law derived from the self-consistent action-angle transport theory. Besides the well-known hyperresistive (helicity-conserving) contribution, the generalized Ohm's law contains an anomalous resistivity term, and a turbulent bootstrap-like term proportional to the current density derivative. The numerical solution of the equation for equilibrium and turbulence profiles characteristic of conventional and advanced scenarios shows that, trough "turbulent bootstrap" effect and anomalous resistivity turbulence can generate power and parallel current which are a sizable portion (about 20 − 25 %) of the corresponding effects associated with the neoclassical bootstrap effect. The degree of alignment of the turbulence peak and the pressure gradient plays an important role in defining the steady-state regime. In fully bootstrapped tokamak, the hyper-resistivity is essential in overcoming the intrinsic limitation of the hollow current profile.

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Section: Discussionmentioning

confidence: 99%

Turbulent contributions to Ohm's law in axisymmetric magnetized plasmas

Chavdarovski

Gatto

2017

Physics of Plasmas

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“…We have investigated the resistivity dependence of the fluctuation level and relaxation by performing computations over a limited range of S ͑2.5ϫ10 3 -2ϫ10 4 ͒. This range is close to contemporary experiments ͑e.g., in HIT, Sϳ10 5 ͒.…”

Section: Lundquist Number Scalingmentioning

confidence: 99%

“…͑2͒ is eliminated. The simulations have S ranging from 5ϫ10 3 to 2ϫ10 4 , and other parameters are the same as those used for the nonlinear S scan. The results in Table III show that the trends of increasing fluctuation level and current profile flattening are similar to those produced by the full nonlinear simulations.…”

Section: B Quasilinear Computationsmentioning

confidence: 99%

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

Sovinec

Prager

1996

Physics of Plasmas

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Magnetohydrodynamic ͑MHD͒ computations of direct current ͑DC͒ 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 2.5ϫ10 3 to 2ϫ10 4 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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“…[13][14][15][16] The ability to stir the MPDX plasma through LaB 6 cusp biasing is possible because LaB 6 can withstand high bias voltages (V d < 500 V).…”

Section: Lab 6 Stirring Electrodesmentioning

confidence: 99%

The Madison plasma dynamo experiment: A facility for studying laboratory plasma astrophysics

et al. 2014

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The Madison plasma dynamo experiment (MPDX) is a novel, versatile, basic plasma research device designed to investigate flow driven magnetohydrodynamic instabilities and other high-b phenomena with astrophysically relevant parameters. A 3 m diameter vacuum vessel is lined with 36 rings of alternately oriented 4000 G samarium cobalt magnets, which create an axisymmetric multicusp that contains $14 m 3 of nearly magnetic field free plasma that is well confined and highly ionized (>50%). At present, 8 lanthanum hexaboride (LaB 6 ) cathodes and 10 molybdenum anodes are inserted into the vessel and biased up to 500 V, drawing 40 A each cathode, ionizing a low pressure Ar or He fill gas and heating it. Up to 100 kW of electron cyclotron heating power is planned for additional electron heating. The LaB 6 cathodes are positioned in the magnetized edge to drive toroidal rotation through J Â B torques that propagate into the unmagnetized core plasma. Dynamo studies on MPDX require a high magnetic Reynolds number Rm > 1000, and an adjustable fluid Reynolds number 10 < Re < 1000, in the regime where the kinetic energy of the flow exceeds the magnetic energy (M 2 A ¼ ðv=v A Þ 2 > 1). Initial results from MPDX are presented along with a 0-dimensional power and particle balance model to predict the viscosity and resistivity to achieve dynamo action. V C 2014 AIP Publishing LLC.

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Steady-state tokamak discharge via dc helicity injection

Cited by 89 publications

References 14 publications

Turbulent contributions to Ohm's law in axisymmetric magnetized plasmas

Turbulent contributions to Ohm's law in axisymmetric magnetized plasmas

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

The Madison plasma dynamo experiment: A facility for studying laboratory plasma astrophysics

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