Gas-Dynamical Theory of the Effect of Laser Radiation on Condensed Substances

Afanas'ev, Yu. V.; Крохин, О. Н.

doi:10.1007/978-1-4757-6339-3_2

Cited by 5 publications

(7 citation statements)

References 7 publications

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“…(9) change in opposite directions (see Tables I and II). Clearly, it is the second exponent α = 0.724 (14) that should be compared with the known analytic scalings for p a (I lh ). A noticeably larger statistical uncertainty in this exponent (±0.014 versus ±0.005, thus comparable to the experimental error), related to the goodness of fit, is apparently caused by using the integral values of φ r and f la , which "feel" the 2D ablation geometry of a spherical droplet.…”

Section: A Laser Absorption and Radiative Lossesmentioning

confidence: 99%

“…If the pulse length is large compared to the hydrodynamic time scale of the ablation flow, a quasi-stationary regime sets in, where the structure of the ablation front only slowly varies in time. The structure of such quasistationary ablation fronts has been extensively studied under various simplifying assumptions for more than 40 years 1, [13][14][15][16][17][18][19] . However, none of these theoretical works is directly applicable to our system.…”

Section: Introductionmentioning

confidence: 99%

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Power-law scaling of plasma pressure on laser-ablated tin microdroplets

et al. 2018

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The measurement of the propulsion of metallic microdroplets exposed to nanosecond laser pulses provides an elegant method for probing the ablation pressure in dense laser-produced plasma. We present the measurements of the propulsion velocity over three decades in the driving Nd:YAG laser pulse energy, and observe a near-perfect power law dependence. Simulations performed with the RALEF-2D radiation-hydrodynamic code are shown to be in good agreement with the power law above a specific threshold energy. The simulations highlight the importance of radiative losses which significantly modify the power of the pressure scaling. Having found a good agreement between the experiment and the simulations, we investigate the analytic origins of the obtained power law and conclude that none of the available analytic theories is directly applicable for explaining our power exponent.

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Section: A Laser Absorption and Radiative Lossesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

et al. 2018

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“…When the counterpressure is high, the vapor velocity is lower than the speed of sound and is related to the pressure jump at the shock-wave front by the equation [16,21] …”

Section: It -Io = H H = Hst -(C~to -Cpsttst )mentioning

confidence: 99%

Dynamics of explosive boiling of drops at the superheat limit

Avksentyuk¹,

Ovchinnikov²

1999

J Appl Mech Tech Phys

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A physical model for explosive boiling of drops is presented. Loss of stability of the liquid-vapor interface results in occurrence of evaporation fronts. Their propagation in a metastable liquid is determined by the vapor recoil momentum. Detachment of drops from the interface is due to thermocapillary forces. The validity of the model is supported by comparison of calculations with experimental data.In a liquid with no centers of evaporation, nearly limiting superheat temperatures can be attained. In this case, boiling occurs spontaneously and vapor bubbles form by fluctuations. At high superheat temperatures, the rate of evaporation of the liquid is so high that the boiling has an explosive nature. This process is called a vapor explosion. Under industrial conditions, vapor explosions can be extremely destructive. Vapor explosion hazards determine the practical importance of studies of physical processes involved in explosive boiling.In experimental studies of the boiling dynamics for butane drops, Shepherd and Sturtevant [1] found that the explosive character of boiling is due to the loss of stability of the liquid-vapor interface. A series of single photographs of bubbles taken at various delay times gives a comprehensive idea of the development of evaporation. At the beginning of boiling, just one bubble always formed. It arose at the boundary of the drop, and Shepherd and Sturtevant [1] explained this by the nonuniformity of the temperature field in the drop. Instability of the interface developed at the early stage of bubble growth. The surface of the vapor formation growing in the drop has small-scale roughness with a large amplitude of irregularities. The volume occupied by the vapor formation was measured from the photographs. The measured volume was then set equal to the volume of a sphere, and the effective radius of the vapor formation was determined. The roughness of the interface was ignored therewith. It turned out that the growth rate of the effective radius of the vapor formation was constant in time. For butane at atmospheric pressure and a temperature of 105~ it is 14.3 m/sec, which is much lower than the rate calculated from the Rayleigh formulawhere Ap is the pressure difference for the vapor and liquid phase and pr is the liquid density. This formula describes the stage of bubble growth at very small times when the liquid inertia is a determining factor.

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“…In both cases the vapours of ablated material are transparent to the incident radiation [2][3][4][5][6]. When the excitation energy exceeds the binding energy of a target material, bond breaking may happen and the target ablation takes place.…”

Section: Laser Light Absorptionmentioning

confidence: 99%

“…For the rough estimates one can present the vapour density in the Arrenius-like form similar to that for the saturated vapours [2][3][4][5][6][7]: nl = $no1&1 exp--&1 ; (16) Cl) kBTJ here c0 is the speed of sound in a cold target material, and /3 is numerical constant which should be determined from experiment [6]. There is no satisfactory analytical relationship between the absorbed laser intensity and the target temperature at the low intensities to our knowledge.…”

Section: ) CMmentioning

confidence: 99%

<title>Ultrafast ablation with high-pulse-repetition-rate lasers: I. Theoretical considerations</title>

Gamaly¹,

Rode

1998

SPIE Proceedings

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The novel technique for deposition of a high quality thin films of different materials by the use of picosecond laser pulses delivered on a target with the repetition rate of several tens of megahertz is proposed. The differences of the proposed method from the conventional pulse laserdeposition is due to shorter laser pulses (picosecond instead of nanosecond) and higher repetition rate which is tens of megahertz (MHz) instead of tens of hertz (Hz). The method allows us to significantly improve the quality of a film due to a decrease by nine orders of magnitude in a number of particles evaporating during a single laser pulse in comparison to that produced by nanosecond, 30 Hz lasers, thus removing a major disadvantage of laser deposition method which is the formation of particulates on the film.The use of a very high repetition rate laser also leads to a qualitatively new mode of vapour-substrate interaction. Due to the short time (107_108 sec) between the laser pulses a quasi-continuous laser plume is formed. The particles evaporated by the previous laser pulse and just deposited on the substrate do not cool down significantly by the time when the particles from the following laser pulse arrive, and therefore their chemical bonds are still reactive. As a result, the high repetition rate regime of evaporation allows for formation of structures on the substrate such as, for example, carbon nanotubes, polymer chains, etc. Another advantage is the opportunity of scanning the laser focal spot over different targets of different materials which allows for a deposition of multilayered films containing mono-atomic layers of different atoms.The results on ultrafast laser ablation and deposition are presented in two joint papers. In this paper (Part I) we present the theoretical justification of the ultrafast laser deposition method, calculating the vapour characteristics, evaporation and deposition rates for the optimal evaporation regime for different modes of laser-target interaction. In the second paper (Part II) the experimental results on evaporation of a graphite target, deposition of high quality diamond-like (DLC) films and the comparison of the laser plume characteristics to theory are presented. I.

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Gas-Dynamical Theory of the Effect of Laser Radiation on Condensed Substances

Cited by 5 publications

References 7 publications

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

Dynamics of explosive boiling of drops at the superheat limit

<title>Ultrafast ablation with high-pulse-repetition-rate lasers: I. Theoretical considerations</title>

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