Magnetic reconnection during flux conversion in a driven spheromak

Hooper, E. B.; Kopriva, T. A.; Cohen, B. I.; Hill, D. N.; McLean, H. S.; Wood, R. D.; Woodruff, S.; Sovinec, C. R.

doi:10.1063/1.2040207

Cited by 24 publications

(33 citation statements)

References 32 publications

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“…A detailed examination of reconnection during spheromak formation is presented elsewhere. 10 In Fig. 5 we compare time histories for the gun current, the poloidal magnetic field measured at an edge probe near the flux-conserver midplane, and peak electron temperatures from NIMROD simulation lam06 ͑ Ќ =21 m 2 /s͒ and SSPX shot 12 560.…”

Section: -3mentioning

confidence: 99%

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Simulation of spheromak evolution and energy confinement

et al. 2005

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Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and model the plasma energy confinement. The physics of magnetic reconnection during formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code ͓C. R. The simulation results are tracking SSPX with increasing fidelity ͑e.g., improved agreement with measured magnetic fields, fluctuation amplitudes, and electron temperature͒ as the simulation has been improved in its representations of the experimental geometry, the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations confirm that controlling the magnetic fluctuations is influenced by the current drive history and by matching the gun current in sustainment approximately to the value corresponding to the eigenvalue in the flux-conserver for the parallel current in a force-free equilibrium.

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Section: -3mentioning

confidence: 99%

“…Pulsations in the voltage are correlated with oscillations in the poloidal magnetic field history and reconnection events. 10 With detailed field-line tracing using NIMROD …”

Section: Simulations Of Formation and Sustainment Pulses In Sspxmentioning

confidence: 99%

Simulation of spheromak evolution and energy confinement

et al. 2005

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“…There are some indirect indications that the rotation may be present. In particular, in order to make magnetic fluctuation spectra consistent with experimental spectra, a rotation with a frequency f=20 kHz was imposed in the numerical simulations of SSPX [5]. As we shall see, this frequency is consistent with our model, although there is no way for a more detailed comparison at present.…”

Section: The Modelmentioning

confidence: 76%

“…#s " 0.71n #T e #s + en #$ #s (5) and, because of a small electron mass, the inertial term in the left-hand side (LHS) can be neglected (compared to, say, pressure term in the RHS) for not-too-large connection lengths. Indeed, relating the change of the plasma parameters along the flux tubes to the time ! "…”

Section: The Modelmentioning

confidence: 99%

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A model of plasma rotation in the Livermore spheromak for the regimes of large connection lengths

Ryutov

2007

Physics of Plasmas

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A model is suggested that predicts the velocity and geometrical characteristics of the plasma rotation in the Livermore spheromak. The model addresses the "good confinement" regimes in this device, where the typical length of magnetic field lines before their intersection with the wall (this length is called "connection length" below) becomes large enough to make the parallel heat loss insignificant. In such regimes, the heat flux is determined by the transport across toroidally-averaged flux surfaces. The model is based on the assumption that, entering the good confinement regime, does not automatically mean that the connection length becomes infinite, and perfect flux surfaces are established. It is hypothesized that connection length remains finite, albeit large in regard to the parallel heat loss. The field lines are threading the whole plasma volume, although it takes a long distance for them to get from one toroidally-averaged flux surface to another. The parallel electron momentum balance then uniquely determines the distribution of the electrostatic potential between these surfaces. An analysis of viscous stresses shows that the toroidal flow is much faster than the poloidal flow. It is shown that the rotation shear usually exceeds by a factor of a few the characteristic growth rate of drift waves, meaning that suppression of the transport caused by the drift turbulence may occur, and a transport barrier with respect to this transport mechanism may be formed. The model may be useful for assessing the plasma rotation in other spheromaks and, possibly, reversed-field pinches and field-reversed configurations, provided a certain set of applicability conditions (Sec. II) is fulfilled.

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