Emergence of kinetic behavior in streaming ultracold neutral plasmas

McQuillen, Patrick; Castro, Jose; Bradshaw, S. J.; Killian, T. C.

doi:10.1063/1.4918705

Cited by 7 publications

(6 citation statements)

References 54 publications

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“…This trend is more evident if one fits the data sets for each initial condition individually independent values of β . This suggests a small influence of kinetic effects, 47 such as free-streaming, which enhances density at the expanding fronts and broadens the width of the fitted curve at each scaled time.…”

Section: B Expansion Of An Ucnp With An Exponentially Decaying Densit...mentioning

confidence: 97%

“…Figure 7 shows that for low T e (0), ions equilibrate with T /T DIH ∼ 1. Subsequent moderate heating on a longer timescale reflects dissipation of ion acoustic waves and 47,50 and electron-ion energy exchange. Temperatures are scaled by the disorder-induced-heating temperature T DIH and time is scaled by the ion oscillation period 2π/ω pi .…”

Section: Temperature Evolutionmentioning

confidence: 99%

“…Such systems have shed light on equilibration [26][27][28][29][30][31][32][33][34][35][36][37][38][39] and transport 40 in strongly coupled plasmas, 41 which has connections to laser-produced plasmas 32,42 extending into the warm-dense-matter and highenergy-density regimes. 43,44 With excellent control over the initial conditions and precise diagnostics, they have been used to benchmark theories and numerical techniques for quantum, 45 molecular-dynamic, 38,40 kinetic, 34 and hydrodynamic descriptions, 46,47 and to observe and characterize collective modes and instabilities. 16,[48][49][50] UCNPs are also being developed for applications in bright ion and electron beams.…”

Section: Ucnpsmentioning

confidence: 99%

“…Hydrodynamic models accurately describe the evolution of plasma density in collisional systems, for which the length scales of plasma inhomogeneities are much larger than the particle mean free path and the particles are close to local thermal equilibrium. 46,47 Assuming quasineutrality 22 (n e ≈ n i ≡ n for electron and ion densities n e and n i ) and the absence of any magnetic forces, this implies the following equation for the rate of change of the local hydrodynamic velocity u in the limit of…”

Section: Plasma Expansionmentioning

confidence: 99%

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Expansion of Ultracold Neutral Plasmas with Exponentially Decaying Density Distributions

Warrens¹,

Gorman²,

Bradshaw³

et al. 2020

Preprint

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We present a study of the expansion of an ultracold neutral plasma (UCNP) with an initial density distribution that decays exponentially in space, created by photoionizing atoms shortly after their release from a quadrupole (or biconic cusp) magnetic trap. A characteristic ion acoustic timescale is evident in the evolution of the plasma size and velocity, indicating the dynamics are reasonably well described by a model of hydrodynamic expansion of a quasi-neutral plasma. However, for low plasma density and high initial electron temperature, excess ion kinetic energy in the vicinity of the central density peak suggests significant local non-neutrality at early times. Observations are compared to the wellunderstood self-similar expansion of an UCNP with an initial Gaussian density distribution, and a similar scaling law describes the evolution of plasma size for both cases.

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Section: B Expansion Of An Ucnp With An Exponentially Decaying Densit...mentioning

confidence: 97%

Section: Temperature Evolutionmentioning

confidence: 99%

Section: Ucnpsmentioning

confidence: 99%

Section: Plasma Expansionmentioning

confidence: 99%

See 2 more Smart Citations

Expansion of Ultracold Neutral Plasmas with Exponentially Decaying Density Distributions

Warrens¹,

Gorman²,

Bradshaw³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…The evolution of a freely expanding UNP comprises three different stages, namely electron equilibration [11], ion equilibration [12], and plasma expansion [13]. During the latter, * hugo.tercas@tecnico.ulisboa.pt † titomend@ist.utl.pt free electrons are able to escape the cloud, producing a electron depletion and thus a net positive charge in the core.…”

Section: Introductionmentioning

confidence: 99%

Electron trapping in freely expanding ultracold neutral plasmas

2019

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We report on the self-induced electron trapping occurring in a ultracold neutral plasma that is set to expand freely. At the early stages of the plasma, the ions are not thermalized follow a Gaussian spatial profile, providing the trapping to the coldest electrons. In the present work, we provide a theoretical model describing the electrostatic potential and perform molecular dynamics simulations to validate our findings. We show that in the strong confinement regime, the plasma potential is of a Thomas-Fermi type, similar to the case of heavy atomic species. The numerically simulated spatial profiles of the particles corroborate this claim. We also extract the electron temperature and coupling parameter from the simulation, so the duration of the transient Thomas-Fermi is obtained.

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Ion-kinetic simulations of D-3He gas-filled inertial confinement fusion target implosions with moderate to large Knudsen number

et al. 2016

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Experiments designed to investigate the transition to non-collisional behavior in D3He-gas inertial confinement fusion target implosions display increasingly large discrepancies with respect to simulations by standard hydrodynamics codes as the expected ion mean-free-paths λc increase with respect to the target radius R (i.e., when the Knudsen number NK=λc/R grows). To take properly into account large NK's, multi-ion-species Vlasov-Fokker-Planck computations of the inner gas in the capsules have been performed, for two different values of NK, one moderate and one large. The results, including nuclear yield, reactivity-weighted ion temperatures, nuclear emissivities, and surface brightness, have been compared with the experimental data and with the results of hydrodynamical simulations, some of which include an ad hoc modeling of kinetic effects. The experimental results are quite accurately rendered by the kinetic calculations in the smaller-NK case, much better than by the hydrodynamical calculations. The kinetic effects at play in this case are thus correctly understood. However, in the higher-NK case, the agreement is much worse. The remaining discrepancies are shown to arise from kinetic phenomena (e.g., inter-species diffusion) occurring at the gas-pusher interface, which should be investigated in the future work.

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Emergence of kinetic behavior in streaming ultracold neutral plasmas

Cited by 7 publications

References 54 publications

Expansion of Ultracold Neutral Plasmas with Exponentially Decaying Density Distributions

Expansion of Ultracold Neutral Plasmas with Exponentially Decaying Density Distributions

Electron trapping in freely expanding ultracold neutral plasmas

Ion-kinetic simulations of D-3He gas-filled inertial confinement fusion target implosions with moderate to large Knudsen number

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