Nonlinear instability dynamics in a high-density, high-beta plasma

Corr, Cormac; Boswell, Rod

doi:10.1063/1.3074790

Cited by 7 publications

(7 citation statements)

References 23 publications

(24 reference statements)

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“…For the present high density plasma discharge in the thin sheath regime (the probe sheath is much less than the probe radius), the effect brought by RF fluctuations on the floating potential and the I(V ) characteristics was found to be negligible. 35 Radial translation of the probe was set using a computer controlled stepper motor arrangement that allowed the probe tip position to be selected with an accuracy of a few micrometers. To determine the plasma I(V ) characteristics, the bias voltage on the Langmuir probe was swept between − 50 V and + 30 V using a Labview program.…”

Section: Fig 1 a Schematic Of The Wombat (Waves On Magnetisedmentioning

confidence: 99%

“…15 Overlaid are best fits to the profile using a Gaussian profile (n i0 = n i (0)e −(r/R) 2 ): these show reasonable agreement over the range of the data. The stronger field produces better confinement with a smaller characteristic radius R. Figure 2(b) shows the radial variation of the space potential in WOMBAT for a slightly different field strength, B z = 0.0068 T. 35 Overlaid is a best fit to the data using the parabolic potential profile in Eq. (5), with the arbitrary reference potential (χ c ) and gradient (G = Ωi0 2ψZ ( + Ω i0 ) + λ Z ) free parameters.…”

Section: Steady-state Solutionmentioning

confidence: 99%

“…15 Overlaid are best fits to the profile using a Gaussian profile (n i0 = n i (0)e −(r/R) 2 ): these show reasonable agreement over the range of the data. The stronger field 15 (b) the radial variation of the normalised space potential from the fit procedure (solid line), the model (dashed) and the data (dots), 35 which was taken under the conditions of Bz = 0.0068 T, 0.6 mTorr and 1708 W in the experiment; (c) the radial profile of the electron temperature at two field strengths: Bz = 0.0185 T and Bz = 0.0034 T. 15 The dashed vertical line in (c) corresponds to the radial location of fluctuation measurements.…”

Section: Steady-state Solutionmentioning

confidence: 99%

“…Figure 2(b) shows the radial variation of the space potential in WOMBAT for a slightly different field strength, B z = 0.0068 T. 35 Overlaid is a best fit to the data using the parabolic potential profile in Eq. ( 5), with the arbitrary reference potential (χ c ) and gradient (G = Ωi0 2ψZ ( + Ω i0 ) + λ Z free parameters.…”

Section: Steady-state Solutionmentioning

confidence: 99%

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A flowing plasma model to describe drift waves in a cylindrical helicon discharge

2011

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A two-fluid model developed originally to describe wave oscillations in the vacuum arc centrifuge, a cylindrical, rapidly rotating, low temperature and confined plasma column, is applied to interpret plasma oscillations in a RF generated linear magnetised plasma (WOMBAT), with similar density and field strength. Compared to typical centrifuge plasmas, WOMBAT plasmas have slower normalised rotation frequency, lower temperature and lower axial velocity. Despite these differences, the two-fluid model provides a consistent description of the WOMBAT plasma configuration and yields qualitative agreement between measured and predicted wave oscillation frequencies with axial field strength. In addition, the radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. To our knowledge, this is the first detailed physics model of flowing plasmas in the diffusion region away from the RF source. Possible extensions to the model, including temperature non-uniformity and magnetic field oscillations, are also discussed.

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Section: Fig 1 a Schematic Of The Wombat (Waves On Magnetisedmentioning

confidence: 99%

Section: Steady-state Solutionmentioning

confidence: 99%

Section: Steady-state Solutionmentioning

confidence: 99%

Section: Steady-state Solutionmentioning

confidence: 99%

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A flowing plasma model to describe drift waves in a cylindrical helicon discharge

2011

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“…[7][8][9][10][11][12] Due to the nonuniform configurations of equilibrium magnetic field, discharge area and plume, plasma rotation driven by Lorentz force commonly occurs in various electric thrusters. [13][14][15][16] A few analytical models have been developed or/and applied to describe this flowing phenomenon, [17][18][19][20][21] but little attention was given to the resulted plasma instability which, however, can effect the propulsion efficiency, precise control, durable reliability and life time significantly. 22,23 This paper considers an emerging plasma propulsion technology, namely magnetically enhanced vacuum a) Electronic mail: leichang@scu.edu.cn arc thruster (MEVAT), [24][25][26][27][28] as an example and studies the instability evolution caused by plasma rotation and axial flow in detail.…”

Section: Introductionmentioning

confidence: 99%

Plasma instability of magnetically enhanced vacuum arc thruster

Chang

Zhang²,

et al. 2019

AIP Advances

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A two-fluid flowing plasma model is applied to describe the plasma rotation and resulted instability evolution in magnetically enhanced vacuum arc thruster (MEVAT). Typical experimental parameters are employed, including plasma density, equilibrium magnetic field, ion and electron temperatures, cathode materials, axial streaming velocity, and azimuthal rotation frequency. It is found that the growth rate of plasma instability increases with growing rotation frequency and field strength, and with descending electron temperature and atomic weight, for which the underlying physics are explained. The radial structure of density fluctuation is compared with that of equilibrium density gradient, and the radial locations of their peak magnitudes are very close, showing an evidence of resistive drift mode driven by density gradient. Temporal evolution of perturbed mass flow in the cross section of plasma column is also presented, which behaves in form of clockwise rotation (direction of electron diamagnetic drift) at edge and anti-clockwise rotation (direction of ion diamagnetic drift) in the core, separated by a mode transition layer from n = 0 to n = 1. This work, to our best knowledge, is the first treatment of plasma instability caused by rotation and axial flow in MEVAT, and is also of great practical interest for other electric thrusters where rotating plasma is concerned for long-time stable operation and propulsion efficiency optimization.

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