Dynamics of Laser Ablation in Superfluid $$^4\hbox {He}$$

Buelna, Xavier; Popov, Evgeny; Eloranta, Jussi

doi:10.1007/s10909-016-1668-8

Cited by 9 publications

(7 citation statements)

References 42 publications

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“…On the microsecond time scale, the hot ablation spot vaporizes the surrounding liquid and produces a slowly expanding cavitation bubble (“ablation bubble”; see, e.g., the top panel of Figure ). The breathing dynamics of the ablation bubble appears to be overdamped, with a pronounced instability appearing toward the end of its trajectory . During this period ( t > 1 ms), unusual “explosive” events are observed, as demonstrated in the bottom panel of Figure .…”

Section: Resultsmentioning

confidence: 88%

“…The breathing dynamics of the ablation bubble appears to be overdamped, with a pronounced instability appearing toward the end of its trajectory. 33 During this period (t > 1 ms), unusual "explosive" events are observed, as demonstrated in the bottom panel of Figure 2.…”

Section: ■ Experimental Sectionmentioning

confidence: 82%

“…Once the expanding ablation bubble has reached its maximum radius, it becomes unstable and exhibits strong fluctuations in both geometry and volume . With the typical laser powers applied in this study, this regime is reached a couple of milliseconds after the ablation laser pulse.…”

Section: Discussionmentioning

confidence: 93%

“…Once the expanding ablation bubble has reached its maximum radius, it becomes unstable and exhibits strong fluctuations in both geometry and volume. 33 With the typical laser powers applied in this study, this regime is reached a couple of milliseconds after the ablation laser pulse. The observed violent explosive events near the target (see the bottom panel of Figure 2) can contribute to this previously reported ablation bubble instability during its contraction phase.…”

Section: ■ Discussionmentioning

confidence: 94%

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Ejection of Metal Particles into Superfluid⁴He by Laser Ablation

et al. 2016

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The dynamics following laser ablation of a metal target immersed in superfluid $^4$He is studied by time-resolved shadowgraph photography. The delayed ejection of hot micrometer-sized particles from the target surface into the liquid was indirectly observed by monitoring the formation and growth of gaseous bubbles around the particles. The experimentally determined particle average velocity distribution appears similar as previously measured in vacuum but exhibits a sharp cutoff at the speed of sound of the liquid. The propagation of the subsonic particles terminates in slightly elongated non-spherical gas bubbles residing near the target whereas faster particles reveal an unusual hydrodynamic response of the liquid. Based on the previously established semi-empirical model developed for macroscopic objects, the ejected transonic particles exhibit supercavitating flow to reduce their hydrodynamic drag. Supersonic particles appear to follow a completely different propagation mechanism as they leave discrete and semi-continuous bubble trails in the liquid. The relatively low number density of the observed non-spherical gas bubbles indicates that only large micron-sized particles are visualized in the experiments. Although the unique properties of superfluid helium allow a detailed characterization of these processes, the developed technique can be used to study the hydrodynamic response of any liquid to fast propagating objects on the micrometer-scale.

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Section: Resultsmentioning

confidence: 88%

Section: ■ Experimental Sectionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 93%

Section: ■ Discussionmentioning

confidence: 94%

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Ejection of Metal Particles into Superfluid⁴He by Laser Ablation

et al. 2016

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“…1. The initial radial plasma expansion [38][39][40] leads to non-linear excitation of the surrounding liquid, which was visualized by time-resolved shadowgraph photography using a monochrome charge-coupled device (CCD; Imaging Source DMK23U445) equipped with 180X zoom lens (working dist. 95 mm; max.…”

Section: Solitons In Thinmentioning

confidence: 99%

First Observation of Bright Solitons in Bulk Superfluid He4

et al. 2018

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The existence of bright solitons in bulk superfluid 4 He is demonstrated by time-resolved shadowgraph imaging experiments and density functional theory (DFT) calculations. The initial liquid compression that leads to the creation of non-linear waves is produced by rapidly expanding plasma from laser ablation. After the leading dissipative period, these waves transform into bright solitons, which exhibit three characteristic features: dispersionless propagation, negligible interaction in twowave collision, and direct dependence between soliton amplitude and the propagation velocity. The experimental observations are supported by DFT calculations, which show rapid evolution of the initially compressed liquid into bright solitons. At high amplitudes, solitons become unstable and break down into dispersive shock waves.PACS numbers: 67.25. D-,67.25.bf, 67.85.dt Solitons are localized non-linear waves in a medium, which do not disperse as a function of time and exhibit no interaction during a two-wave collision. After their discovery in the early eighteen hundreds, solitons have been observed in many different media, which exhibit pronounced non-linear response. In recent years, solitons have become an intense field of research due to their important applications in areas such as plasma physics, electronics, biology, and optics [1]. Mathematical description of solitons can be formulated in terms of model dependent non-linear partial differential equations (e.g., the non-linear Schrödinger equation). In general, it has been established that non-linear excitations (i.e., shock waves and solitons) exhibit distinct dependency between their amplitude and propagation velocity [1]. Solitons in thin4 He films adsorbed on solid substrates have been studied extensively by both experiments [2][3][4][5] and theory [6][7][8][9]. The film thickness is typically only a few atomic layers, which supports the propagation of third sound [10]. When the film is driven by a sufficiently large amplitude excitation, the response of the system becomes non-linear and typically follows the Kortewegde Vries (KdV) equation [4,7]. The KdV equation is known to support solitonic solutions, which has been confirmed experimentally for helium films in the previously mentioned references. Solitons have also been observed experimentally in related systems such as Bose-Einstein condensates (BEC) and 3 He (magnetic solitons) [11][12][13][14][15][16][17][18][19][20]. In the former case, experimental observations have been successfully modeled by the Gross-Pitaevskii (GP) equation [21][22][23]. However, bright solitons have not been observed in bulk superfluid 4 He up to date. Such observation would not only provide important details of the underlying non-linear response of this quantum liquid, but it would also allow for the study of soliton dynamics (including dissipation) over much longer propagation distances and times than currently possible in BECs.Studies of non-linear excitations in bulk superfluid helium are scarce. Most experiments have concentr...

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