Progress on observations of interspecies ion separation in inertial-confinement-fusion implosions via imaging x-ray spectroscopy

Joshi, T. R.; Hsu, S. C.; Hakel, P.; Hoffman, N. M.; Sio, H.; Mancini, Roberto

doi:10.1063/1.5092998

Cited by 11 publications

(2 citation statements)

References 48 publications

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“…Keenan et al employed an ion-kinetic code to study collisional planar shocks in two-ion plasmas [20]. Comparatively few experiments have been performed that have been able to study the structure inside a collisional multi-ion-species plasma shock [16,[21][22][23][24].…”

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confidence: 99%

Ion Diffusion Velocity Measurements in a Multi-Ion-Species Plasma Shock

Chu¹,

LaJoie²,

Keenan³

et al. 2022

Preprint

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Collisional plasma shocks generated from supersonic flows are an important feature in many astrophysical and laboratory high-energy-density plasmas. Compared to single-ion-species plasma shocks, plasma shock fronts with multiple ion species contain additional structure, including interspecies ion separation driven by gradients in species concentration, temperature, pressure, and electric potential. We present time-resolved density and temperature measurements of two ion species in collisional plasma shocks produced by head-on merging of supersonic plasma jets, allowing determination of the diffusion velocity of the ion species. Our results demonstrate that the lighter ion species diffuse faster than the heavier species within a shock front, consistent with predictions from the interion-species transport theory. Results from the experiment approach quantitative agreement with theoretical prediction and 1D ion-Fokker-Planck kinetic simulation.

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confidence: 99%

Ion Diffusion Velocity Measurements in a Multi-Ion-Species Plasma Shock

Chu¹,

LaJoie²,

Keenan³

et al. 2022

Preprint

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“…Prior experiments, simulations, and theoretical work explored multiion-species effects in the context of inertial confinement fusion (ICF), for which species separation in the fusion fuel potentially leads to neutron yield degradation [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Interspecies ion separation and velocity separation were experimentally observed [19][20][21][22][23]. Additional simulation and theoretical research on multi-ion-species plasmas examined how ion species diffusion causes species separation [24][25][26][27][28][29][30].…”

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confidence: 99%

Observation of shock-front separation in multi-ion-species collisional plasma shocks

et al. 2020

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We observe shock-front separation and species-dependent shock widths in multi-ion-species collisional plasma shocks, which are produced by obliquely merging plasma jets of a He/Ar mixture (97% He and 3% Ar by initial number density) on the Plasma Liner Experiment [S. C. Hsu et al., IEEE Trans. Plasma Sci. 46, 1951]. Visible plasma emission near the He-I 587.6-nm and Ar-II 476.5-514.5-nm lines are simultaneously recorded by splitting a single visible image of the shock into two different fast-framing cameras with different narrow bandpass filters (589 ± 5 nm for observing the He-I line and 500 ± 25 nm for the Ar-II lines). For conditions in these experiments (pre-shock ion and electron densities ≈ 5 × 10 14 cm −3 , ion and electron temperatures of ≈ 2.2 eV, and relative plasma-merging speed of 22 km/s), the observationally inferred magnitude of He/Ar shock-front separation and the shock widths themselves are < 1 cm, which correspond to ∼ 50 post-shock thermal ion-ion mean free paths. The experiments are in reasonable qualitative and quantitative agreement with results from 1D multi-fluid simulations using the chicago code. Moreover, the experiment and simulation results are consistent with first-principles theoretical predictions that the lighter He ions diffuse farther ahead within the overall shock front than the heavier Ar ions.

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First observation of increased DT yield over prediction due to addition of hydrogen

et al. 2021

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In a number of reported instances, implosions utilizing fuel mixtures have resulted in anomalously low fusion yields below those predicted by radiation-hydrodynamics simulations. Inter-species ion diffusion has been suggested as a possible cause of the observed yield degradation in fuel mixture implosions. An experimental platform utilizing hydro-equivalent deuterium–tritium (DT), deuterium–tritium–hydrogen (DTH), and deuterium-tritium-helium3 (DT3He) capsule implosions was developed to determine whether the inter-species ion diffusion theory may describe the resulting fuel mixture implosion behavior. The implosion experiments were performed at the Omega laser facility. X-ray images and shell areal density diagnostics results show that the hydro-equivalent three capsules (DT, DTH, and DT3He) have similar compression behavior. However, nuclear yield deviation was observed from the scaling determined using a fusion yield formula. In the DT3He mixture, a reduced yield of a factor of 0.65 ± 0.13 was observed, which is similar to a yield reduction observed in D3He mixture by Rygg et al. (i.e., Rygg effect). In contrast, in the DTH mixture, a factor of 1.17 ± 0.15 yield increase was observed, which we named the inverse Rygg effect. The yield increase observed in the DTH mixture is consistent with the inter-species ion diffusion theory where lighter H diffuses away from the core and concentrated DT in the core produces higher yield. An inter-species ion diffusion model, the Zimmerman–Paquette–Kagan–Zhdanov model, implemented in a Lagrangian radiation-hydrodynamics fluid code, was also used to analyze the present data, without the need to assume hydrodynamic equivalence of the capsules, but it does not completely explain the DTH or DT3He capsules although its effects are in the correct direction. Simulation-based Bayesian inference was used in the latter analysis to quantify the uncertainty in the numerical simulations. The simulation-based analysis resulted in an inferred Rygg-effect yield decrease factor of 0.91 ± 0.02 for the DT3He mixture, and an inferred inverse-Rygg yield increase factor of 1.21 ± 0.04 for the DTH mixture, based on simulations ignoring ion diffusion.

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Progress on observations of interspecies ion separation in inertial-confinement-fusion implosions via imaging x-ray spectroscopy

Cited by 11 publications

References 48 publications

Ion Diffusion Velocity Measurements in a Multi-Ion-Species Plasma Shock

Ion Diffusion Velocity Measurements in a Multi-Ion-Species Plasma Shock

Observation of shock-front separation in multi-ion-species collisional plasma shocks

First observation of increased DT yield over prediction due to addition of hydrogen

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