First Test of Long-Range Collisional Drag via Plasma Wave Damping

Affolter, M.; Anderegg, F.; Dubin, D. H. E.; Driscoll, C. F.

doi:10.1103/physrevlett.117.155001

Cited by 11 publications

(16 citation statements)

References 36 publications

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“…We show that this drag damping is proportional to the parallel collisional slowing rate, and therefore provides a test of this new long-range collision theory. 17 Measurements are in quantitative agreement with a collisional drag damping theory only when long-range collisions are included, 20 exceeding classical short-range collision predictions by as much as an order of magnitude.…”

Section: Introductionmentioning

confidence: 58%

“…By changing the strength of the laser cooling, the damping rate of these plasma waves is measured over four decades in the plasma temperature 10 À4 Շ T Շ 1 eV. At high temperatures T տ 0:2 eV, thermal particles are near the wave phase velocity, and collisionless Landau damping dominates 20 with linear Landau rates 50 Շ c L Շ 8000 s À1 . In the temperature range 0:02 Շ T Շ 0:2 eV, prior experiments suggest that the wave damping is dominated by bounce harmonic Landau damping introduced through finite-length effects.…”

Section: Figmentioning

confidence: 99%

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Measurements of long-range enhanced collisional velocity drag through plasma wave damping

et al. 2018

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We present damping measurements of axial plasma waves in magnetized, multispecies ion plasmas. At high temperatures T տ 10 À2 eV, collisionless Landau damping dominates, whereas, at lower temperatures T Շ 10 À2 eV, the damping arises from interspecies collisional drag, which is dependent on the plasma composition and scales roughly as T À3=2. This drag damping is proportional to the rate of parallel collisional slowing, and is found to exceed classical predictions of collisional drag damping by as much as an order of magnitude, but agrees with a new collision theory that includes long-range collisions. Centrifugal mass separation and collisional locking of the species occur at ultra-low temperatures T Շ 10 À3 eV, which reduce the drag damping from the T À3=2 collisional scaling. These mechanisms are investigated by measuring the damping of higher frequency axial modes, and by measuring the damping in plasmas with a non-equilibrium species profile.

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Section: Introductionmentioning

confidence: 58%

Section: Figmentioning

confidence: 99%

Measurements of long-range enhanced collisional velocity drag through plasma wave damping

et al. 2018

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“…, the direction of energy exchange reverses, and the pump and daughter wave amplitudes proceed to oscillate as the waves exchange energy back and forth. At this low temperature T ∼ 10 −2 eV, the wave energy eventually is dissipated by interspecies collisional drag [36] at a rate γ ∼ 50 s −1 .…”

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confidence: 99%

“…Although this trapped particle fraction is below the sensitivity for direct laser diagnostics, they are indirectly observed through nonlinear Landau damping. Small amplitude waves (|A m | < ∼ 0.1%) damp at the linear Landau rate 8000 > ∼ γ L > ∼ 50 s −1 [36]. Whereas, at larger wave amplitudes, these resonant particles are trapped in the wave potential resulting in trapping oscillations at a frequency ω 2 T ∼ |A m |ω 2 , and diminishing the damping rate as the trapped particles phase mix [40].…”

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confidence: 99%

Trapped Particle Effects in the Parametric Instability of Near-Acoustic Plasma Waves

et al. 2018

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Quantitative experiments on the parametric decay instability of near-acoustic plasma waves provide strong evidence that trapped particles reduce the instability threshold below fluid models. At low temperatures, the broad characteristics of the parametric instability are determined by the frequency detuning of the pump and daughter wave, and the wave-wave coupling strength, surprisingly consistent with cold fluid, three-wave theories. However, at higher temperatures, trapped particle effects dominate, and the pump wave becomes unstable at half the threshold pump wave amplitude with similar exponential growth rates as for a cold plasma.

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“…5 verifies the formula in Eq. (11). Also, the predictions made by classical slowing down theory are usually only guaranteed to order ln Λ −1 ; however, the slowing-down times in Fig.…”

Section: Discussionmentioning

confidence: 96%

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

2018

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We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρ e , is comparable to or less than the Debye length, λ De , and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρ e and λ De , and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τ s , versus fast-ion charge are in agreement with unmagnetized slowing-down theory; with an applied magnetic field, no consistent anisotropy between τ s in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. The implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.

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First Test of Long-Range Collisional Drag via Plasma Wave Damping

Cited by 11 publications

References 36 publications

Measurements of long-range enhanced collisional velocity drag through plasma wave damping

Measurements of long-range enhanced collisional velocity drag through plasma wave damping

Trapped Particle Effects in the Parametric Instability of Near-Acoustic Plasma Waves

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

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