Three-dimensional plasmoid-mediated reconnection and the effect of toroidal guide field in simulations of coaxial helicity injection

Ebrahimi, F.

doi:10.1063/1.5098482

Cited by 7 publications

(4 citation statements)

References 32 publications

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“…Lastly, the experimental NSTX camera images during helicity injection plasma start-up in Ebrahimi & Raman (2015) (and the supplementary movie there), which show distinct plasmoids leaving the device with velocities of about , have inspired this thruster concept and could in fact provide a proof of principle. The first qualitative experimental evidence of plasmoid formation demonstrated there was first predicted by global MHD simulations (Ebrahimi & Raman 2015), later expanded for plasmoid-driven start-up in spherical tokamaks (Ebrahimi & Raman 2016; Ebrahimi 2019). The extended MHD simulations presented here have been instrumental for exploring the fundamental physics of this new concept.…”

Section: Discussionmentioning

confidence: 96%

An Alfvenic reconnecting plasmoid thruster

Ebrahimi

2020

J. Plasma Phys.

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A new concept for the generation of thrust for space propulsion is introduced. Energetic thrust is generated in the form of plasmoids (confined plasma in closed magnetic loops) when magnetic helicity (linked magnetic field lines) is injected into an annular channel. Using a novel configuration of static electric and magnetic fields, the concept utilizes a current-sheet instability to spontaneously and continuously create plasmoids via magnetic reconnection. The generated low-temperature plasma is simulated in a global annular geometry using the extended magnetohydrodynamic model. Because the system-size plasmoid is an Alfvenic outflow from the reconnection site, its thrust is proportional to the square of the magnetic field strength and does not ideally depend on the mass of the ion species of the plasma. Exhaust velocities in the range of 20 to $500\ \textrm {km}\ \textrm {s}^{-1}$ , controllable by the coil currents, are observed in the simulations.

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Section: Discussionmentioning

confidence: 96%

An Alfvenic reconnecting plasmoid thruster

Ebrahimi

2020

J. Plasma Phys.

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“…According to a recent MHD numerical simulation on T-CHI [22], the reconnection rate based on the plasmoid instability is much faster than that by the Sweet-Parker (S-P) model even in the high Lundquist number S regime. Understanding the mechanism of fast plasmoid reconnection for flux closure and related ion heating is the primary objective of the T-CHI experiment on the HIST device [23].…”

Section: Transient Coaxial Helicity Injectionmentioning

confidence: 99%

Overview of coordinated spherical tokamak research in Japan

et al. 2022

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Spherical tokamak (ST) research in Japan has produced many innovative results: (i) plasma start-up to I p > 70 kA was achieved by electron cyclotron wave (ECW) with N ∥ = 0.75, while electron heating to T e > 500 eV was achieved with N ∥ = 0.26 on QUEST. (ii) The radiofrequency (RF)-induced transport model was combined with the x-ray emission model, and extended magnetohydrodynamics equilibrium with kinetic electrons was developed to interpret fast-electron-dominated lower hybrid wave sustained plasmas on TST-2. (iii) Density as high as 30 times the cutoff density was achieved by electron Berstein wave current drive combined with electron beam injection on LATE. (iv) Multiple plasmoids formed by tearing instability in the elongated current sheet were observed, and flux closure and ion heating by plasmoid-mediated fast magnetic reconnection were observed on HIST. (v) Optimization of ECW-assisted inductive start-up with a vertical field with positive decay index was performed on TST-2. (vi) Stabilization of the vertical displacement event by a set of upper and lower helical field coils was demonstrated on TOKASTAR-2. (vii) A 6 h discharge was achieved by cool-down of the center stack cover on QUEST, where the plasma duration limit was consistent with the wall saturation time estimated by modeling. (viii) Extension of ion heating by plasma merging was achieved on TS-3U, TS-4U, UTST, MAST, and ST40.

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“…The model has recently been used to help MAST-U achieve first plasma [154]. 3D resistive MHD simulations (NIMROD [155]) of coaxial helicity injection based on NSTX experiments predict non-inductive current generation from plasmoid-mediated reconnection scales favorably to higher B T [156]. While there are no current plans for CHI in NSTX-U, the favorable scaling implies that it may still be an effective approach for non-inductive startup in future devices operating at higher field.…”

Section: Scenario Optimization and Controlmentioning

confidence: 99%

NSTX-U theory, modeling and analysis results

Guttenfelder¹,

Battaglia²,

Белова³

et al. 2022

Nucl. Fusion

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The mission of the low aspect ratio spherical tokamak NSTX-U is to advance the physics basis and technical solutions required for optimizing the configuration of next-step steady-state tokamak fusion devices. NSTX-U will ultimately operate at up to 2 MA of plasma current and 1 T toroidal field on axis for 5 seconds, and has available up to 15 MW of Neutral Beam Injection (NBI) power at different tangency radii and 6 MW of High Harmonic Fast Wave (HHFW) heating. With these capabilities NSTX-U will develop the physics understanding and control tools to ramp-up and sustain high performance fully non-inductive plasmas with large bootstrap fraction and enhanced confinement enabled via the low aspect ratio, high beta configuration. With its unique capabilities, NSTX-U research also supports ITER and other critical fusion development needs. Super-Alfvénic ions in beam-heated NSTX-U plasmas access energetic particle parameter space that is relevant for both -heated conventional and low aspect ratio burning plasmas. NSTX-U can also generate very large target heat fluxes to test conventional and innovative plasma exhaust and plasma facing component (PFC) solutions. This paper summarizes recent analysis, theory and modelling progress to advance the tokamak physics basis in the areas of macrostability and 3D fields, energetic particle stability and fast ion transport, thermal transport and pedestal structure, boundary and plasma material interaction, RF heating, scenario optimization and real-time control.

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Three-dimensional plasmoid-mediated reconnection and the effect of toroidal guide field in simulations of coaxial helicity injection

Cited by 7 publications

References 32 publications

An Alfvenic reconnecting plasmoid thruster

An Alfvenic reconnecting plasmoid thruster

Overview of coordinated spherical tokamak research in Japan

NSTX-U theory, modeling and analysis results

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