On the role of the ablated mass on the propagation of a laser-generated plasma in an ambient gas

Ablation depths of stainless steel targets irradiated by 80-fs laser pulses at a flux F ≤ 40 J/cm2 (intensity ≤ 5 × 1014 W/cm2) in the presence of air at atmospheric pressure are experimentally measured. These values are lower than the theoretical predictions for metal targets in vacuum. Results are analyzed on the basis of the role of the ambient gas and of crater formation on the behavior of the ablated material.

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Experimental Investigation of the Effect of the Ambient Gas on Evaporating Sessile Drops

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.258-260.461 ◽

2006 ◽

Vol 258-260 ◽

pp. 461-468

Author(s):

S. David ◽

Khellil Sefiane ◽

Lounes Tadrist

Keyword(s):

Evaporation Rate ◽

Controlled Environment ◽

Experimental Setup ◽

Reduced Pressure ◽

Interfacial Conditions ◽

Ambient Gases ◽

Ambient Gas ◽

Different Gases ◽

Sessile Drops

This paper presents the results of an experimental study of evaporating sessile drops in a controlled environment. The experimental setup allowed the investigation of the evaporation rate of sessile drops under reduced pressure (40 to 1000 mbar) and various ambient gases. Sessile drops of initial volume 2.5μL are deposited on substrates and left to evaporate in a controlled atmosphere. The effect of reducing pressure on the evaporation rate as well as changing the ambient gas is studied. Three different gases are used; namely Helium, Nitrogen and Carbon Dioxide. The role of vapour diffusion as a limiting mechanism for evaporation is studied. It is found that in all cases the evaporation rate is limited by the mass diffusion in the ambient gas provided that interfacial conditions are properly accounted for. This includes important evaporative cooling observed at higher evaporation rates and lower substrate thermal conductivity.

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Role of shell diffusion area in incubating eggs at simulated high altitude

Journal of Applied Physiology ◽

10.1152/jappl.1978.45.4.551 ◽

1978 ◽

Vol 45 (4) ◽

pp. 551-556 ◽

Cited By ~ 5

Author(s):

H. S. Weiss

Keyword(s):

Weight Loss ◽

Gas Exchange ◽

Embryonic Development ◽

Ambient Pressure ◽

Enskog Equation ◽

Egg Weight ◽

Excess Loss ◽

Simulated High Altitude ◽

Ambient Gas

Embryonic development is inhibited when eggs are incubated at 9,100 m (0.3 atm) despite a normoxic environment. The problem apparently relates to respiratory gas exchange occurring by diffusion through gas-filled pores in the shell. Gaseous flux is therefore inversely proportional to ambient pressure and is affected by the physical characteristics of the ambient gas (Chapman-Enskog equation). Excess loss of H2O and CO2 occurs in eggs incubating at altitude and could be detrimental. Such increased loss should be correctable by decreasing diffusion area. This was tested by progressively increasing coverage of the shell with paraffin and incubating at simulated 0.3 ATA (225 Torr) in 100% O2. Uncoated eggs failed to hatch, but numbers of chicks increased with increased coverage. Maximum hatch was an extrapolated 90% of controls at 69% shell coverage. With further coverage, hatch size decreased. Egg weight loss, and estimate of H2O diffusion, was around three times controls in uncoated eggs but decreased linearly with paraffin coverage, reaching near normal at maximum hatch. Reduction of diffusion area to 0.3 normal at maximum hatch generally balanced the increased flux predicted for 0.3 ATA.

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