Suppression of drift waves in a linear magnetized plasma column

DuBois, Ami M.; Eadon, Ashley; Thomas, E.

doi:10.1063/1.4731711

Cited by 7 publications

(2 citation statements)

References 26 publications

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“…Linear devices such as LAPD, which are very long with relatively low magnetic field, observe saturated turbulence as expected [13]. Experimental evidence has shown that drift-waves can be suppressed in the presence of an external potential bias imposing a radial electric field on the plasma [14]; however, a comprehensive scan of magnetic field and device length has not to our knowledge been conducted. This work therefore serves as a theoretical prediction of the plasma behaviour in regards to resistive drift-wave turbulence stability in linear devices.…”

Section: Discussionmentioning

confidence: 94%

Intrinsic suppression of turbulence in linear plasma devices

Leddy

Dudson

2017

Plasma Phys. Control. Fusion

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Plasma turbulence is the dominant transport mechanism for heat and particles in magnetized plasmas in linear devices and tokamaks, so the study of turbulence is important in limiting and controlling this transport. Linear devices provide an axial magnetic field that serves to confine a plasma in cylindrical geometry as it travels along the magnetic field from the source to the strike point. Due to perpendicular transport, the plasma density and temperature have a roughly Gaussian radial profile with gradients that drive instabilities, such as resistive drift-waves and Kelvin-Helmholtz. If unstable, these instabilities cause perturbations to grow resulting in saturated turbulence, increasing the cross-field transport of heat and particles. When the plasma emerges from the source, there is a time, τ , that describes the lifetime of the plasma based on parallel velocity and length of the device. As the plasma moves down the device, it also moves azimuthally according to E × B and diamagnetic velocities. There is a balance point in these parallel and perpendicular times that sets the stabilisation threshold. We simulate plasmas with a variety of parallel lengths and magnetic fields to vary the parallel and perpendicular lifetimes, respectively, and find that there is a clear correlation between the saturated RMS density perturbation level and the balance between these lifetimes. The threshold of marginal stability is seen to exist where τ ≈ 11τ ⊥ . This is also associated with the product τ γ * , where γ * is the drift-wave linear growth rate, indicating that the instability must exist for roughly 100 times the growth time for the instability to enter the non-linear growth phase. We explore the root of this correlation and the implications for linear device design.

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Section: Discussionmentioning

confidence: 94%

Intrinsic suppression of turbulence in linear plasma devices

Leddy

Dudson

2017

Plasma Phys. Control. Fusion

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“…The density gradient is negligible compared to the electric field, ruling out the possibility that the low‐frequency mode is a drift wave. In addition, drift waves are stabilized by velocity shear [ Gavrishchaka et al ., ; DuBois et al ., ].…”

Section: Resultsmentioning

confidence: 99%

Experimental characterization of broadband electrostatic noise due to plasma compression

et al. 2014

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For a wide variety of laboratory and space plasma environments, theoretical predictions state that plasmas are unstable to inhomogeneous flows over a very broad frequency range. Such sheared flows are generated in the Earth's magnetosphere and intensify during active periods. Specifically, for a velocity shear oriented perpendicular to a uniform background magnetic field, the shear scale length (L E ) compared to the ion gyroradius ( ρ i ) determines the character of the shear-driven instability that may prevail. An interpenetrating plasma configuration is used to create a transverse velocity shear profile in a magnetized plasma column, a condition similar to that found in the natural boundary layers. The continuous variation of ρ i /L E and the associated transition of the instability regimes driven by the shear flow mechanism are demonstrated in a single laboratory experiment. Broadband wave emission correlated to increasing/decreasing stress (i.e., ρ i /L E ), a characteristic signature of a boundary layer crossing, is found under controlled and repeatable conditions. This result holds out the promise for understanding the cause and effect of the in situ observation of broadband electrostatic noise.

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Fast wave stabilization/destabilization of drift waves in a plasma

Kumar

Tripathi

2013

Physics of Plasmas

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Four wave-nonlinear coupling of a large amplitude whistler with low frequency drift wave and whistler wave sidebands is examined. The pump and whistler sidebands exert a low frequency ponderomotive force on electrons introducing a frequency shift in the drift wave. For whistler pump propagating along the ambient magnetic field Bsẑ with wave number k→0, drift waves of wave number k→=k→⊥+k||ẑ see an upward frequency shift when k⊥2/k02>4k||/k0 and are stabilized once the whistler power exceeds a threshold value. The drift waves of low transverse wavelength tend to be destabilized by the nonlinear coupling. Oblique propagating whistler pump with transverse wave vector parallel to k→⊥ is also effective but with reduced effectiveness.

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Suppression of drift waves in a linear magnetized plasma column

Cited by 7 publications

References 26 publications

Intrinsic suppression of turbulence in linear plasma devices

Intrinsic suppression of turbulence in linear plasma devices

Experimental characterization of broadband electrostatic noise due to plasma compression

Fast wave stabilization/destabilization of drift waves in a plasma

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