NIMROD resistive magnetohydrodynamic simulations of spheromak physics

Hooper, E. B.; Cohen, B. I.; McLean, H. S.; Wood, R. D.; Romero-Talamás, C.A.; Sovinec, C. R.

doi:10.1063/1.2890772

Cited by 20 publications

(26 citation statements)

References 22 publications

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“…Simulation studies of OFCD on MST, 14 Sustained spheromax physics experiment (SSPX), 15,16 rotating magnetic field current drive (RMF) on field-reverse configurations (FRCs), 17 and very recently Pegasus Compact Torus 18 focused on demonstration of the key characteristics of the experiments and qualitative agreement. The paper by Gray et al 19 on the MHD simulations of 3D magnetic reconnection and merging in the Swarthmore Spheromak Experiment presents a side-by-side comparison of the measured and simulated magnetic fields at the probe locations, but only at a single instant during fast relaxation.…”

Section: Introductionmentioning

confidence: 99%

Validation of single-fluid and two-fluid magnetohydrodynamic models of the helicity injected torus spheromak experiment with the NIMROD code

Akçay

Kim²,

Victor

et al. 2013

Physics of Plasmas

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We present a comparison study of 3-D pressureless resistive MHD (rMHD) and 3-D presureless two-fluid MHD models of the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI). HIT-SI is a current drive experiment that uses two geometrically asymmetric helicity injectors to generate and sustain toroidal plasmas. The comparable size of the collisionless ion skin depth d i to the resistive skin depth predicates the importance of the Hall term for HIT-SI. The simulations are run with NIMROD, an initial-value, 3-D extended MHD code. The modeled plasma density and temperature are assumed uniform and constant. The helicity injectors are modeled as oscillating normal magnetic and parallel electric field boundary conditions. The simulations use parameters that closely match those of the experiment. The simulation output is compared to the formation time, plasma current, and internal and surface magnetic fields. Results of the study indicate 2fl-MHD shows quantitative agreement with the experiment while rMHD only captures the qualitative features. The validity of each model is assessed based on how accurately it reproduces the global quantities as well as the temporal and spatial dependence of the measured magnetic fields. 2fl-MHD produces the current amplification I tor I inj and formation time s f demonstrated by HIT-SI with similar internal magnetic fields. rMHD underestimates I tor I inj and exhibits much a longer s f . Biorthogonal decomposition (BD), a powerful mathematical tool for reducing large data sets, is employed to quantify how well the simulations reproduce the measured surface magnetic fields without resorting to a probe-by-probe comparison. BD shows that 2fl-MHD captures the dominant surface magnetic structures and the temporal behavior of these features better than rMHD. V C 2013 AIP Publishing LLC. [http://dx.

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Section: Introductionmentioning

confidence: 99%

Validation of single-fluid and two-fluid magnetohydrodynamic models of the helicity injected torus spheromak experiment with the NIMROD code

Akçay

Kim²,

Victor

et al. 2013

Physics of Plasmas

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“…In an effort to describe more slowly growing modes, such as the internal kink, tearing modes, and resistive edge-localized modes~ELM!, several linear [6][7][8] and nonlinear [9][10][11][12][13] codes solving the resistive MHD equations have been developed. These codes have enjoyed some successes in modeling the results of experiments with comparatively high collision frequency, [14][15][16][17] but they have been largely unable to predict quantitatively the occurrence or evolution of long-wavelength, sub-Alfvénic instabilities in low-collisionality experiments. 18,19 In particular, existing MHD codes are unable to predict the period of sawtooth oscillations, the repetition frequency of the ELM, and either the onset threshold or the saturation amplitude for the neoclassical tearing mode~NTM!.…”

Section: Introductionmentioning

confidence: 99%

Models for Sub-Alfvénic Magnetodynamics of Fusion Plasmas

Waelbroeck

2011

Fusion Science and Technology

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“…This finding may be relevant to the apparent ideal-MHD -limit observed in SSPX discharges during periods when the safety-factor profile lies above 1/2. 25 A tendency for symmetry-breaking modes and reduced confinement in nonlinear resistive-MHD simulations of the quiescent phase of SSPX discharges has been noted in previous work, 33 and it is possible that consistent twotemperature extended MHD modeling would yield results that better represent the experiment's confinement properties.…”

Section: Discussionmentioning

confidence: 70%

Parameter-space survey of linear G-mode and interchange in extended magnetohydrodynamics

Howell

Sovinec

2017

Physics of Plasmas

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The extended magnetohydrodynamic stability of interchange modes is studied in two configurations. In slab geometry, a local dispersion relation for the gravitational interchange mode (g-mode) with three di↵erent extensions of the MHD model [P. Zhu, et al., Phys. Rev. Lett. 101, 085005 (2008)] is analyzed. Our results delineate where drifts stablize the g-mode with gyroviscosity alone and with a two-fluid Ohm's law alone. Including the two-fluid Ohm's law produces an ion drift wave that interacts with the g-mode. This interaction gives rise to a second instability at finite k y. A second instability is also observed in numerical extended MHD computations of linear interchange in cylindrical screw-pinch equilibria, the second configuration. Particularly with incomplete models, this mode limits the regions of stability for physically realistic conditions. However, applying a consistent two-temperature extended MHD model that includes the diamagnetic heat flux density (q ⇤) makes the onset of the second mode occur at larger Hall parameter. For conditions relevant to the SSPX experiment [E.B. Hooper, Plasma Phys. Controlled Fusion 54, 113001 (2012)], significant stabilization is observed for Suydam parameters as large as unity (D s. 1).

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NIMROD resistive magnetohydrodynamic simulations of spheromak physics

Abstract: The physics of spheromak plasmas is addressed by time-dependent, three-dimensional,

Cited by 20 publications

References 22 publications

Validation of single-fluid and two-fluid magnetohydrodynamic models of the helicity injected torus spheromak experiment with the NIMROD code

Validation of single-fluid and two-fluid magnetohydrodynamic models of the helicity injected torus spheromak experiment with the NIMROD code

Models for Sub-Alfvénic Magnetodynamics of Fusion Plasmas

Parameter-space survey of linear G-mode and interchange in extended magnetohydrodynamics

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