Effect of Focusing Plane on Laser Blow-off Shock Waves from Confined Aluminum and Copper Foils

2021 ◽  
Author(s):  
Nagaraju Guthikonda ◽  
Sai Shiva S ◽  
E. Manikanta ◽  
Kameswari P S L D ◽  
V. R. Ikkurthi ◽  
...  
Keyword(s):  
Laser Energy ◽  
Plasma Temperature ◽  
Laser Pulses ◽  
Ambient Air ◽  
Rear Side ◽  
Hydrodynamic Simulations ◽  
Enhanced Absorption ◽  
532 Nm ◽  
Lower Plasma Density ◽  
Good Agreement

Abstract We present results on the dynamics of laser-induced blow-off shockwave generation from the rear side of 20 µm thick aluminum and copper foil confined with a glass (BK7) substrate. These foils are irradiated by 10 ns, 532 nm laser pulses of energy 25 – 200 mJ corresponding to the intensity range 0.2 – 10 GW/cm2. The plasma temperature at the glass-foil interface is observed to play an important role in the coupling of laser energy to the foil. From our experiments and 1D hydrodynamic simulations, we confirm that moving the glass-foil interface away from the focal plane led to (a) enhanced absorption of the laser beam by the foil resulting in ~ 30 % higher blow-off shock velocities (b) significant changes in the material ejection in terms of increased blow-off mass of the foil (c) lower plasma density and temperatures. The material ejection as well as blow-off shock velocity is higher for Al compared to Cu. The simulated shock evolution in ambient air shows a reasonably good agreement with the experimental results.

scholarly journals Theoretical study of soft X-ray emission and dynamics of laser-induced plasma of double stream gas puff

2021 ◽  
Vol 75 (11) ◽  
Author(s):  
Vassily S Zakharov ◽  
Sergey V Zakharov
Keyword(s):  
Laser Beam ◽  
Compression Wave ◽  
Laser Energy ◽  
Spectral Characteristics ◽  
Plasma Temperature ◽  
Laser Pulses ◽  
Plasma Radiation ◽  
Nanosecond Laser ◽  
Transient Effects ◽  
X Ray

AbstractThe double stream gas puff-based laser-produced plasma is studied as a source of soft X-ray radiation in nm wavelength spectral range. Dynamics of plasma induced by Nd:YAG laser beam and its emission is simulated with radiation-magnetohydrodynamic code Zstar. The modeling results for krypton gas stream in an annular helium jet as a circumferential gas for various picosecond and nanosecond laser pulses corresponding to the experiments are presented. The spatial–spectral features and temporal behavior of the soft X-ray and EUV emission are investigated. Under ps pulse, the gas is rapidly ionized in the laser beam channel, but it does not have enough time to shift sensibly during the pulse, and the plasma electron density grows against the background of almost constant ion density during the ionization in the laser radiation field. There is ionization instability only capable to be developed in ps range. At ns pulse, the gas ionization and heating leads to gas pushing out of the channel, and the formation of a divergent compression wave transforming into the shock wave. Behind the compression wave front, conditions arise for the development of Rayleigh–Taylor-type instability. The instability leads to the redistribution of plasma temperature and density, and to the formation of increased soft X-ray emission spots. Time evolution of spatial distributions and spectral characteristics of emitted SXR radiation is analyzed for different laser pulses. Transient effects in multicharged ion plasma are discussed, fundamental understanding of those is required for optimization of plasma radiation source. A conversion efficiency of laser energy into soft X-ray wavebands from krypton plasma is scanned by laser parameters and analyzed.

Emission of Charged Particles from Laser Irradiated Silicon

1981 ◽  
Vol 4 ◽  
Author(s):  
J.M. Liu ◽  
R. Yen ◽  
H. Kurz ◽  
N. Bloembergen
Keyword(s):  
Crystalline Silicon ◽  
Laser Energy ◽  
Charged Particles ◽  
Laser Pulses ◽  
Silicon Surfaces ◽  
Molten Silicon ◽  
Surface Layers ◽  
Upper Limits ◽  
532 Nm ◽  
Pulsed Laser Irradiation

ABSTRACTEmission of charged particles from (111) and (100) crystalline silicon surfaces during and following picosecond pulsed laser irradiation in vacuo has been investigated.No thermionic electron emission is observable, setting an upper limit of 5000°K on the electron temperature during the laser pulses at 532 nm and at 266 nm. Equal number of positive and negative particles are emitted when the laser energy fluence is sufficient to cause vaporization of a few surface layers. Significantly larger amount of electrons than that of positive particles are emitted under irradiation with UV pulses at low energy fluences. This phenomenon can be tentatively explained by thermally enhanced photoelectric emission from a molten silicon surface.The presence or absence of the emission of charged particles sets important lower or upper limits on the temperature of the electrons and of the lattice. Our data are fully consistent with a model of complete thermalization between carriers and lattice on a time scale of 10–11 sec.

Harmonic Emission from the Rear Side of Thin Overdense Foils Irradiated with Intense Ultrashort Laser Pulses

2004 ◽  
Vol 92 (18) ◽  
Author(s):  
U. Teubner ◽  
K. Eidmann ◽  
U. Wagner ◽  
U. Andiel ◽  
F. Pisani ◽  
...  
Keyword(s):  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
Rear Side ◽  
Harmonic Emission ◽  
Ultrashort Laser

Emission of molecular nitrogen at tight focusing of femtosecond laser pulses in air

2021 ◽  
pp. 42-48
Author(s):  
A.A. Ilyin ◽  
◽  
K.A. Shmirko ◽  
S.S. Golik ◽  
D.Yu. Proschenko ◽  
...  
Keyword(s):  
Particle Density ◽  
Molecular Nitrogen ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Plasma Particle ◽  
Sharp Drop ◽  
Radiation Level ◽  
Femtosecond Radiation ◽  
Tight Focusing ◽  
Good Agreement

A numerical model describing the dynamics of plasma particle density upon filamentation of femtosecond radiation in the air is presented. The simulation results are in good agreement with the experimental data. The pumping processes of the N2 and N2+ radiative levels are investigated. The model predicts a sharp drop in electron temperature and density within 1 ns. For the first positive nitrogen system, an excess of the population of the upper radiation level over the population of the lower one is observed for 550 ps.

The transient start of supersonic jets

2007 ◽  
Vol 578 ◽  
pp. 331-369 ◽  
Author(s):  
MATEI I. RADULESCU ◽  
CHUNG K. LAW
Keyword(s):  
Numerical Simulations ◽  
Ambient Air ◽  
Hydrogen Gas ◽  
Shock Interactions ◽  
Round Jets ◽  
Reactive Gases ◽  
Acoustic Instabilities ◽  
Diffusive Fluxes ◽  
Experimental Findings ◽  
Good Agreement

This study investigates the initial transient hydrodynamic evolution of highly under-expanded slit and round jets. A closed-form analytic similarity solution is derived for the temporal evolution of temperature, pressure and density at the jet head for vanishing diffusive fluxes, generalizing a previous model of Chekmarev using Chernyi's boundary-layer method for hypersonic flows. Two-dimensional numerical simulations were also performed to investigate the flow field during the initial stages over distances of ~ 1000 orifice radii. The parameters used in the simulations correspond to the release of pressurized hydrogen gas into ambient air, with pressure ratios varying between approximately 100 and 1000. The simulations confirm the similarity laws derived theoretically and indicate that the head of the jet is laminar at early stages, while complex acoustic instabilities are established at the sides of the jet, involving shock interactions within the vortex rings, in good agreement with previous experimental findings. Very good agreement is found between the present model, the numerical simulations and previous experimental results obtained for both slit and round jets during the transient establishment of the jet. Criteria for Rayleigh–Taylor instability of the decelerating density gradients at the jet head are also derived, as well as the formulation of a model addressing the ignition of unsteady expanding diffusive layers formed during the sudden release of reactive gases.

scholarly journals A Personal Reflection of Greenlight 532 nm Laser for BPH Treatment

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Bilal Chughtai ◽  
Claire Dunphy ◽  
Alexis Te
Keyword(s):  
Surgical Therapy ◽  
Laser Energy ◽  
Laser System ◽  
Prostatic Hyperplasia ◽  
First Line ◽  
Technological Advances ◽  
Urinary Tract Symptoms ◽  
Bothersome Symptom ◽  
532 Nm ◽  
Lower Urinary

Lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia are a bothersome symptom set that affect approximately one in every four males above the age of 50. First line treatment is typically medication, but when medications fail surgical therapy is the next option. Technological advances have made surgical therapy safer and more effective. One area that our group has particular interest and focus in is the application of the 532 nm laser in surgical therapy. The high power 532 nm laser is used to remove obstructive prostatic tissue and the laser energy is selectively absorbed by hemoglobin in the prostate tissue, resulting in effective tissue vaporization and removal. We review our experience with Greenlight laser system and its evolution from the original 60-watt laser to the most recent 180-watt Greenlight system with MoXy fiber.

scholarly journals Preparation and Characterization of Lead Oxide Nanoparticles by Laser Ablation as Antibacterial Agent

2017 ◽  
Vol 14 (4) ◽  
pp. 801-807
Author(s):  
Baghdad Science Journal
Keyword(s):  
Laser Ablation ◽  
Lead Oxide ◽  
Laser Energy ◽  
Laser Pulses ◽  
Diffusion Method ◽  
Lead Target ◽  
Oxide Nanoparticles ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

In this work, lead oxide nanoparticles were prepared by laser ablation of lead target immersed in deionized water by using pulsed Nd:YAG laser with laser energy 400 mJ/pulse and different laser pulses. The chemical bonding of lead oxide nps was investigated by Fourier Transform Infrared (FTIR); surface morphology and optical properties were investigated by Scanning Electron Microscope (SEM) and UV-Visible spectroscopy respectively, and the size effect of lead oxide nanoparticles was studied on its antibacterial action against two types of bacteria Gram-negitive (Escherichia coli) and Gram-positive (Staphylococcusaurus) by diffusion method. The antibacterial property results show that the antibacterial activity of the Lead oxide NPs was inversely proportional to the size of the nanoparticles in both Gram-negative and Gram-positive, and also it has been found that Gram-positive bacteria possess have greater sensitivity and less resistance to the lead oxide nanoparticles compared with Gram-negative bacteria.

scholarly journals Edge Cooling of a Fuel Cell during Aerial Missions by Ambient Air

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1432
Author(s):  
Lev Zakhvatkin ◽  
Alex Schechter ◽  
Eilam Buri ◽  
Idit Avrahami
Keyword(s):  
Fuel Cell ◽  
Numerical Model ◽  
Wind Tunnel ◽  
Boundary Conditions ◽  
Air Temperature ◽  
Numerical Models ◽  
Heat Removal ◽  
Ambient Air ◽  
Experimental Setup ◽  
Good Agreement

During aerial missions of fuel-cell (FC) powered drones, the option of FC edge cooling may improve FC performance and durability. Here we describe an edge cooling approach for fixed-wing FC-powered drones by removing FC heat using the ambient air during flight. A set of experiments in a wind tunnel and numerical simulations were performed to examine the efficiency of FC edge cooling at various flight altitudes and cruise speeds. The experiments were used to validate the numerical model and prove the feasibility of the proposed method. The first simulation duplicated the geometry of the experimental setup and boundary conditions. The calculated temperatures of the stack were in good agreement with those of the experiments (within ±2 °C error). After validation, numerical models of a drone’s fuselage in ambient air with different radiator locations and at different flight speeds (10–30 m/s) and altitudes (up to 5 km) were examined. It was concluded that onboard FC edge cooling by ambient air may be applicable for velocities higher than 10 m/s. Despite the low pressure, density, and Cp of air at high altitudes, heat removal is significantly increased with altitude at all power and velocity conditions due to lower air temperature.

Study of ambient air ionization with femtosecond laser pulses

2005 ◽  
Author(s):  
Yi Wang ◽  
Xiaolei Wang ◽  
Nan Zhang ◽  
Hongchen Zhai ◽  
Xiaonong Zhu
Keyword(s):  
Femtosecond Laser ◽  
Laser Pulses ◽  
Ambient Air ◽  
Femtosecond Laser Pulses ◽  
Air Ionization

Laser-Triggered Surface Flashover Characteristics of Al2O3 in Pulsed Voltage

2011 ◽  
Vol 354-355 ◽  
pp. 1224-1227
Author(s):  
Ru Zheng Pan ◽  
You Hua Wang ◽  
Min Tang Li ◽  
Ling Ling Pang ◽  
Jue Wang ◽  
...  
Keyword(s):  
Energy Density ◽  
Nd:Yag Laser ◽  
Delay Time ◽  
Laser Energy ◽  
Test System ◽  
Vacuum Condition ◽  
Surface Flashover ◽  
532 Nm ◽  
Time Decrease ◽  
Pulsed Voltage

Based on the platform of laser-triggered surface flashover in pulsed voltage, experiment of laser-triggered surface flashover is carried out in air and vacuum condition with pulsed voltage. A single/double harmonic, with wavelength of 1064/532 nm, Q-switched Nd:YAG laser is applied to trigger the surface flashover. The test system consists of flat electrodes and columned insulator. The material of electrode is copper and the material of insulator is Al2O3. Laser pulse’s wavelengths are 532nm and 1064nm, and laser is focused with rectangle. The results of experiment show that flashover delay time and jitter time decrease with increase of pulsed voltage or laser energy density, the delay time of 1064nm laser trigger is larger than that of 532nm laser trigger, and the delay time and jitter time in vacuum condition are less than the delay time and jitter time in air condition.

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