Atmospheric Influences on Q-Switched Laser Sampling and Resulting Plumes

1971 ◽  
Vol 25 (6) ◽  
pp. 642-652 ◽  
Author(s):  
E. H. Piepmeier ◽  
D. E. Osten
Keyword(s):  
Laser Energy ◽  
Ambient Pressure ◽  
Large Fraction ◽  
Wave Model ◽  
Sample Surface ◽  
Copper Sample ◽  
Atmospheric Plasma ◽  
Limited Region ◽  
Single Spike ◽  
Shock Wave Model

When a 10–100-mJ single-spike Q-switched Nd laser pulse is focused on a copper sample, the presence of an atmosphere affects the spectra, the crater size, and the amount of sample vaporized. At 760 Torr the crater diameter (90 µ) and amount of sample vaporized (35 ng) remain relatively constant while at 1 Torr they both increase with increasing laser energy. Spatial changes in the spectra occur with changes in ambient pressure. The continuum intensity of the limited region just above the sample surface appears to be a better measure of the energy reaching the sample than does the energy of the laser beam. The experimental results appear to be caused by absorption of a large fraction of the laser energy in an atmospheric plasma. A radiation-supported shock-wave model is evaluated in detail and compared briefly with similar models as possible mechanisms for production of the atmospheric plasma. The analytical chemical implications of the experimental and theoretical results are discussed.

DIAGNOSTICS OF LASER INDUCED GRAPHITE PLASMA UNDER VARIOUS PRESSURES OF AIR, HELIUM AND ARGON

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Zuhaib Haider ◽  
Kashif Chaudhary ◽  
Sufi Roslan ◽  
Jalil Ali ◽  
Yusof Munajat
Keyword(s):  
Electron Density ◽  
Laser Energy ◽  
Ambient Pressure ◽  
Plasma Temperature ◽  
Sample Surface ◽  
Ambient Atmosphere ◽  
Plasma Parameters ◽  
Saha Equation ◽  
Laser Induced Plasma ◽  
Spectroscopic Information

Laser induced plasma provides information about the elemental composition of sample surface and through spectroscopy vital information about plasma dynamics can be obtained. In this paper we present the diagnostics of laser induced plasma at various pressures of Air, Helium and Argon gases. Graphite sample was ablated with Q-smart 850 laser while spectra were captured  Plasma parameters have been calculated by using well known methods based on Saha and Boltzmann equations. Plasma temperature was calculated relative intensity of ionic carbon lines CII 251.21 nm and CII 426.73 nm while the electron density was determined by using spectroscopic information of CI 247.85 nm and CII 426.73 nm emission lines in Saha equation. Plasma temperature and electron density were found to be dependent upon nature and pressure of the ambient atmosphere. Higher temperatures and electron densities were obtained in the presence of Air as ambient environment that is attributed to electrical and physical properties of the Air. Keeping into consideration the plasma expansion in various environments the selection of a suitable ambient pressure can be made on the basis of spectral diagnostics of plasma for a particular laser energy to obtain desirable plasma temperature and electron density suited for certain applications.

A shock wave model of unstable rocket combustors

AIAA Journal ◽  
1964 ◽  
Vol 2 (7) ◽  
pp. 1285-1296 ◽  
Author(s):  
L. CROCCO ◽  
W. A. SIRIGNANO
Keyword(s):  
Shock Wave ◽  
Wave Model ◽  
Shock Wave Model

Acoustic energy radiated by nonlinear spherical oscillations of strongly driven bubbles

2010 ◽  
Vol 466 (2118) ◽  
pp. 1829-1847 ◽  
Author(s):  
Joachim Holzfuss
Keyword(s):  
Wave Model ◽  
High Amplitude ◽  
Compressible Liquid ◽  
Acoustic Energy ◽  
Compressible Medium ◽  
Relevant Parameter ◽  
Wafer Cleaning ◽  
Viscous Compressible Liquid ◽  
Shock Wave Model ◽  
Polytropic Exponent

Based on the theory of F. Gilmore ( Gilmore 1952 The growth or collapse of a spherical bubble in a viscous compressible liquid ) for radial oscillations of a bubble in a compressible medium, the sound emission of bubbles in water driven by high-amplitude ultrasound is calculated. The model is augmented to include expressions for a variable polytropic exponent, hardcore and water vapour. Radiated acoustic energies are calculated within a quasi-acoustic approximation and also a shock wave model. Isoenergy lines are shown for driving frequencies of 23.5 kHz and 1 MHz. Together with calculations of stability against surface wave oscillations leading to fragmentation, the physically relevant parameter space for the bubble radii is found. Its upper limit is around 6 μm for the lower frequency driving and 1–3 μm for the higher. The radiated acoustic energy of a single bubble driven in the kilohertz range is calculated to be of the order of 100 nJ per driving period; a bubble driven in the megahertz range reaches two orders of magnitude less. The results for the first have applications in sonoluminescence research. Megahertz frequencies are widely used in wafer cleaning, where radiated sound may be implicated as responsible for the damage of nanometre-sized structures.

scholarly journals Shock-wave model of the earthquake and Poincaré quantum theorem give an insight into the aftershock physics.

2018 ◽  
Vol 62 ◽  
pp. 03006
Author(s):  
Vladimir Kuznetsov
Keyword(s):  
Shock Wave ◽  
Wave Model ◽  
Particle Systems ◽  
Many Body ◽  
Initial State ◽  
Recurrence Theorem ◽  
Shock Wave Model ◽  
Quantum Phenomena ◽  
First Time ◽  
Insight Into

A fundamentally new model of aftershocks evident from the shock-wave model of the earthquake and Poincaré Recurrence Theorem [H. Poincare, Acta Mathematica 13, 1 (1890)] is proposed here. The authors (Recurrences in an isolated quantum many-body system, Science 2018) argue that the theorem should be formulated as “Complex systems return almost exactly into their initial state”. For the first time, this recurrence theorem has been demonstrated with complex quantum multi-particle systems. Our shock-wave model of an earthquake proceeds from the quantum entanglement of protons in hydrogen bonds of lithosphere material. Clearly aftershocks are quantum phenomena which mechanism follows the recurrence theorem.

A periodic shock wave model for Mira variable atmospheres

1985 ◽  
Vol 299 ◽  
pp. 167 ◽  
Author(s):  
E. Bertschinger ◽  
R. A. Chevalier
Keyword(s):  
Shock Wave ◽  
Wave Model ◽  
Mira Variable ◽  
Periodic Shock ◽  
Shock Wave Model ◽  
Periodic Shock Wave

The Ladell Diffractometer: Geometry and Applications

1992 ◽  
Vol 36 ◽  
pp. 631-640
Author(s):  
Berton Greenberg
Keyword(s):  
Large Fraction ◽  
Sample Surface ◽  
Peak Position ◽  
Reciprocal Space ◽  
Quantitative Phase Analysis ◽  
Polycrystalline Materials ◽  
Integrated Intensity ◽  
Geometrical Factors ◽  
Sampling Statistics ◽  
Or Applications

AbstractThe Ladell x-ray diffractometer (LD) is designed to study “practical” polycrystalline materials. These are materials which exhibit some combination of texture, strain, and large grain size, or are inhomogeneous or anisotropic in other ways. LD features which make this possible are: the ability to study crystal planes inclined to the sample surface; a versatile reflection geometry; high 2θ resolution via a focusing geometry; a large irradiated sample area (up to 1.5 cm2) for improved intensity and sampling statistics; the ability to examine different sample areas to test for homogeneity; and the use of one sample with no instrument reconfiguration. Scans and/or applications are described that measure texture, strain, twinning, improve quantitative phase analysis, and eliminate substrate scattering.The LD makes use of five independent computer controlled motions. These enable one to study a large fraction of that part of reciprocal space which is accessible by reflection. Instrument geometry and scans are described in terms of α, θ and reciprocal space diagrams. The effect of specimen displacement on peak position is described as are the effects of a number of geometrical factors on integrated intensity.

scholarly journals A Study on the Plasma Plume Expansion Dynamics of Nanosecond Laser Ablating Al/PTFE

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3321
Author(s):  
Sheng Tan ◽  
Moge Wang ◽  
Jianjun Wu ◽  
Yu Zhang ◽  
Jian Li
Keyword(s):  
Plasma Plume ◽  
Laser Energy ◽  
Short Pulse ◽  
Ambient Pressure ◽  
Rapid Expansion ◽  
Nanosecond Laser ◽  
Expansion Process ◽  
Plume Expansion ◽  
Plume Front ◽  
Short Pulse Laser

To study the plasma plume expansion dynamics of nanosecond laser ablating Al/PTFE, the Al/PTFE propellant was prepared by a molding sintering method and the rapid expansion process of the plasma plume was photographed using fast photography technology. The effects of the proportion of Al, laser energy and ambient pressure on plasma plume expansion dynamics are analyzed. The results show that the plume expansion process of laser ablating Al/PTFE plasma can be divided into three stages and this phenomenon has not been reported in the literature. The Al powder doped in PTFE will block part of the laser transmission into the propellant, thus reducing the laser absorption depth of the propellant. In the case of short pulse laser ablation, the reaction rate between Al and PTFE is optimal when the reductant is slightly higher than the oxidant. As the laser energy increases, the light intensity of the plasma becomes stronger, the plasma size becomes larger and the existence time of plasma becomes longer. In the first stage plume, the plume expands freely at the ambient pressure of 0.005 Pa and the plume expansion distance is linearly related to time, while the shock wave formed at the interface between the plume front and the ambient gas at the ambient pressure of 5 Pa and the expansion can be described by S-T theory.

Surface Modification Induced by Femtosecond Laser Pulses in Lithium Niobate

2011 ◽  
Vol 142 ◽  
pp. 134-137
Author(s):  
Hong Yun Chen ◽  
Zhen Zhu Wan ◽  
Yan Ling Han
Keyword(s):  
Surface Modification ◽  
Lithium Niobate ◽  
Femtosecond Laser ◽  
Laser Energy ◽  
Laser Pulses ◽  
Sample Surface ◽  
Femtosecond Laser Pulses ◽  
Two Dimensional ◽  
Damage Depth ◽  
Transparent Materials

The interaction between femtoseocnd laser and transparent materials has been studied intensively in recent years. When the femtosecond laser was focused onto the surface of the transparent materials, if the laser fluence applied to the sample exceeds the material’s fluence threshold, ablation occurs. In this paper, we study the surface ablation of lithium niobate by femtosecond laser. We produced a two-dimensional array of voids in the sample surface by varying the number of shots and laser energy, and analyze of the damage depth with the relation to the pulse energy and the number of the pulse. It has important reference on the microfabrication in such materials by femtosecond laser.

The Formation of Chondrules: Petrologic Tests of the Shock Wave Model

Science ◽  
1998 ◽  
Vol 280 (5360) ◽  
pp. 62-67 ◽  
Author(s):  
H. C. Connolly Jr.
Keyword(s):  
Shock Wave ◽  
Wave Model ◽  
Shock Wave Model
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