A two-stage two-dimensional (2D) gas-dynamic model of laser ablation in an ambient gas atmosphere is proposed. The initial one-dimensional stage of the process is related to the ablation plume formation under the action of a laser pulse (duration of the order of 10 ns; fluence about several J/cm2; laser spot diameter about 1 mm) and ...

Femtosecond pulse laser ablation of aluminum under different ambient air pressures between 1 atm and 4 � 10-4 Pa is investigated using a femtosecond time-resolved shadowgraphic method. It is observed that as the ambient air pressure decreases, the contact front becomes more and more distinct ...

The role of cavitation in bulk ultrasound ablation has been evaluated in a series of in vitro experiments. Fresh bovine liver tissue was ablated with a 3.1 MHz ultrasound image-ablate probe at 31 W/cm2 for 20 minutes under normal and elevated ambient pressures. A 1 MHz passive cavitation ...

12 A 2D gas-dynamic model of laser ablation an ambient gas atmosphere is proposed. To obtain the boundary conditions at the evaporated target surface, a nonlinear heat transfer problem in the target including the dynamics of the melt and evaporation fronts is considered. Back condensation of the vapor at the target is taken into account. At later stages, ...

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

The effect of ambient air pressure on the redeposition of debris, ablated from the zinc borosilicate glass target using 6 ns, 266 nm laser pulses, has been studied for incident fluences of 3-18 J/cm{sup 2}. Measurements were carried out in air at pressures ranging from 10-750 Torr. Scanning electron microscopy and ...

Ferroelectric thin films of barium strontium titanate (BSTO) have been deposited on bare and metallized substrates by the pulsed laser ablation method under different oxygen ambients (150 mT and 50 mT). Under an oxygen pressure of 150 mT, the film composi...

To study the phase transformation mechanism and gas dynamic process for the laser-ablated plume, direct and indirect evidences of potential laser ablation mechanisms were sought experimentally and analytically. Two phase transformation mechanisms, normal vaporization and phase explosion, were introduced as the laser ablation mechanisms ...

... 0 HIGH-PRESSURE ARC-JET ABLATION CHARACTERISTICS OF TEFLON ... HIGH-PRESSURE ARC-JET ABLATION CHARACTERISTICS ...

... Accession Number : ADD412368. Title : DESIGN AND TESTING OF ABLATION MODELS WITH CONTROLLED PRESSURE GRADIENTS. ...

... Accession Number : AD0693559. Title : DESIGN AND TESTING OF ABLATION MODELS WITH CONTROLLED PRESSURE GRADIENTS. ...

... Title : Experimental Scaling Laws for Mass-Ablation Rate, Ablation Pressure in Planar Laser-Produced Plasmas With Laser Intensity, Laser ...

... Title : Ablative Materials. 3. Molding Compounds. Report on Ablative Properties of Materials Molded at Autoclave Pressures,. Corporate Author : ...

... Descriptors : *THRUSTERS, ABLATION, REPRINTS, HIGH PRESSURE, RADIATION ABSORPTION, PLASMA ENGINES, BOUNDARY LAYER ...

Polyoxymethylene (POM) has been widely studied as a laser propulsion propellant paired to CO{sub 2} laser radiation. POM is a good test case for studying ablation properties of polymer materials, and within limits, for study of general trends in laser ablation-induced impulse. Despite many studies, there is no general understanding of POM ...

A cerium oxide sample was ablated by 2nd harmonic radiation of Nd:YAG laser at a power density of 0.1 GW/cm2. Time evolution of the ablation plume was investigated by laser absorption time-of-flight (TOF) measurement. It was found that the ablated ionic plume in vacuum consisted of two components having different velocities whereas the ...

The dynamic behaviors and optical properties of a ZnO plasma plume produced by pulsed laser ablation using a Nd:YAG laser (wavelength: 532 nm, pulse width: 3 ns) were studied by fast photography using a commercial gated charge coupled device (CCD) camera linked with a delay circuit and by optical emission spectroscopy at various ambient oxygen ...

A pulsed ion-beam evaporation (IBE) technique is used to ablate Si species from bulk Si target onto quartz substrates. Large round-shaped droplets up to a few ?m are predominantly formed in vacuum, whereas introduction of He gas could result in formation of particles with decreased size up to a few hundreds nm. A slight oxidation of Si particles is found even in vacuum ...

The size distributions of Si and ZnTe nanoparticles produced by low energy density ArF (193 nm) pulsed laser ablation into ambient gases were measured as a function of the gas pressure, {ital P}, and target-substrate separation, D{sub ts}. For both Si and ZnTe, the largest nanoparticles were found closest to the ...

... of the ambient gases and ablation of the heat ... PLASMA PHYSICS AND MAGNETOHYDRODYNAMICS RADIOFREQUENCY WAVE PROPAGATION ...

By considering the ablatant to be a 4-species (H2, H, H+ and e?) reacting gas and assuming the validity of local thermodynamic equilibrium, the ablatant state of a hydrogen pellet during its passage in a tokamak is studied. Results of analysis showed that the pellet ablation rate is sensitive neither to the specific assumption ...

Pulsed laser ablation of molecular solids is important for identification and quantification in (bio-)organic mass spectrometry, for example using matrix-assisted laser desorption/ionization (MALDI). Recently, there has been a major shift to using MALDI and related laser ablation/post-ionization methods at atmospheric pressure. ...

... SEXPERIMENTAL PRESSURE, TEMPERATURE, AND STRAIN MEASUREMENTS ON ABLATING HEMISPHERICAL NOSE CONES IN ...

Laser ablation and the subsequent development of a high energy dense plasma are receiving increased attention for spectrochemical analysis of solid materials. Observation of the plasma using atomic emission spectroscopy is the most direct method for analysis and offers the possibility of simultaneous multielement analysis. The use of a powerful UV excimer laser for ...

... the ablation front using a discontinuity model identical ... corresponds to the ablative pressure slowly decreasing from ... absorption in the plasma corona ...

... Pyrolysis gas pressure inside the TPS of Formfted: Endnote Reference Pioneer ... ablation. eleted:__ J_Formatted: Endnote Reference ...

The results of an experimental evaluation of ablative materials suitable for the production of light

The results of an experimental evaluation of ablative materials suitable for the production of light

Pressure time variations and associated flows induced by pulsed laser ablation were experimentally studied using the Velocity Interferometer System for Any Reflector (VISAR) and framing Schlieren visualization. The combination of either aluminum or polyacetal target and TEA CO{sub 2} laser pulse were examined. The VISAR measurement resolved that the ...

... apparatus and experiments to explore the relationship between the response of animals to air blast and the ambient pressure existing at the time of ...

... OF HIGH CONCENTRATIONS OF OXYGEN AT AMBIENT PRESSURE AND TEMPERATURE ... AMBIENT PRESSURE AND TEMPERATURE ...

We report time-resolved imaging of a laser-ablated carbon plasma plume to investigate the expansion dynamics of C2 and CN in an ambient atmosphere of nitrogen gas at various pressures. An attempt is made to locate C2 and CN species in the carbon plasma plume and correlate them with the results of spectroscopic observations. The ...

Supernovae launch spherical shocks into the circumstellar medium (CSM). These shocks have high Mach numbers and may be radiative. We have created similar shocks in the laboratory by focusing laser pulses onto the tip of a solid pin surrounded by ambient gas; ablated material from the pin rapidly expands and launches a shock through the surrounding gas. ...

We have developed a simple model to simulate the clusters formation in laser-ablated plume in an ambient atmosphere of inert gas. The model uses the reaction-rate theory as applied to quantum oscillators in conjunction with transition state theory to synthesize and optimize the nanoparticles in the ablated plume. The evolution of ...

Analysis of biochemicals in single cells is important for understanding cell metabolism, cell cycle, adaptation, disease states, etc. Even the same cell types exhibit heterogeneous biochemical makeup depending on their physiological conditions and interactions with the environment. Conventional methods of mass spectrometry (MS) used for the analysis of biomolecules in single cells rely on ...

Removal rate, air shock, and ablative recoil pressure parameters were measured as a function of laser intensity I(peak) during nanosecond laser ablation of graphite. Surface vaporization of molten graphite at low intensities I(peak)<0.15 GW/cm(2) was observed to transform into its near-critical phase explosion (intense homogeneous ...

Removal rate, air shock, and ablative recoil pressure parameters were measured as a function of laser intensity Ipeak during nanosecond laser ablation of graphite. Surface vaporization of molten graphite at low intensities Ipeak<0.15GW/cm2 was observed to transform into its near-critical phase explosion (intense homogeneous ...

Lasers represent an efficient and versatile tool to produce and to arrange in organized dispositions nanometer-sized particles, obtaining extended nanostructures with increasing degrees of complexity. In the first part of the chapter, the basic mechanisms of nanoparticle formation for nanosecond laser ablation in an ambient gas atmosphere and femtosecond ...

This paper presents an overview of pulsed-laser ablation for film deposition and surface microstructure formation. By changing the ambient gas pressure from high vacuum to several Torr (several hundred Pa) and by selecting the pulsed-laser wavelength, the kinetic energy of ablated atoms/ions can be varied from ...

We have used time and space-resolved optical emission spectroscopy to study the expansion dynamics of the plasma generated by pulsed laser ablation of solid targets of the recently discovered superconducting MgB2 into a background Ar gas at different pressures. Our analysis clearly indicates that, above a fixed pressure, plasma ...

... Zero Dimensional Model of High-Pressure Ablative Capillary Discharge with Capillary Wall Thermal Conduction and Radiation Absorption 5b. ...

... Title : Zero Dimensional Model of High-Pressure Ablative Capillary Discharge with Capillary Wall Thermal Conduction and Radiation Absorption. ...

... Title : SANDIA HIGH-PRESSURE ABLATION TEST IN THE AEDC 5-MEGAWATT ARC HEATER TEST UNIT SERIES III. ...

... Title : SANDIA HIGH PRESSURE ABLATION TEST IN THE AEDC 5-MEGAWATT ARC HEATER TEST UNIT, SERIES II. ...

... AD0648322. Title : HIGH-PRESSURE ARC-JET ABLATION CHARACTERISTICS OF TEFLON. Descriptive Note : Technical memo. ...

The contribution deals with ZnO thin layers doped by nitrogen which were prepared by pulsed laser deposition in N2O ambient atmosphere. Our approach is based on ablation of undoped ZnO target in active atmosphere containing N2O gas without any supporting excitation equipment in parallel. Ablation of ZnO target was performed at ...

We have investigated the influence of the laser fluence, ambient nitrogen and target material on the synthesis of aluminum nitride nanosized powders by reactive laser ablation. Pure aluminum and aluminum nitride were used as targets. The study revealed that were pure nanosized AlN powders (3-25 nm in diameter) can be synthesized for laser fluences higher ...

The author's theory of dynamic viscous pressure interaction has been extended to cases with surface ablation by sublimation. It has been shown that the two very large and opposite effects of aftbody ablation and forebody ablation on pitch damping of a sle...

We have used an infrared laser to ablate materials under ambient conditions that were captured in solvent droplets. The droplets were either deposited on a MALDI target for off-line analysis by MALDI time-of-flight mass spectrometry or flow-injected into a nanoelectrospray source of an ion trap mass spectrometer. An infrared optical parametric oscillator ...

The ablation pressure and the mass ablation rate for 10 mu m laser were measured using two methods of a target pendulum and shifted X-ray emission images which was equivalent to X-ray back-lighting. The measured ablation pressure was 10 Mbar and the mass ...

Y2SiO5:Ce phosphor thin films were grown onto Si(100) substrates with pulsed laser deposition (PLD) using a 248-nm KrF excimer laser. Process parameters were varied during the growth process and the effect on the surface morphology and cathodoluminescence (CL) was analysed. The process parameters that were changed included the following: gas pressure (vacuum (5�10-6 Torr), ...

Laser ablation and the subsequent development of a high energy dense plasma are receiving increased attention for spectrochemical analysis of solid materials. Observation of the plasma using atomic emission spectroscopy is the most direct method for analysis and offers the possibility of simultaneous multielement analysis. The use of a powerful UV excimer laser for ...

Laser ablation and the subsequent development of a high energy dense plasma are receiving increased attention for spectrochemical analysis of solid materials. Observation of the plasma using atomic emission spectroscopy is the most direct method for analysis and offers the possibility of simultaneous multielement analysis. The use of a powerful UV excimer laser for ...

We report on a type of surface structuring after short pulse laser ablation of a binary alloy. We observe the emergence of a concentric ring structure with changing elemental composition. The composition changes are interpreted by condensation of the ambient ablation vapor due to stress wave excitations in the ...

N-type CdSe films with thicknesses of 470--630 nm were grown on (001) and 2{degree}-miscut GaAs wafers by ArF (193 nm) pulsed laser ablation of stoichiometric CdSe targets at platen temperatures (T{sub p}) of 250--425 C in vacuum and ambient Ar gas. Film-substrate interdiffusion was studied with Auger depth profiling, as well as energy dispersive x-ray ...

The deposition of carbon nanotubes and carbon nano-onions at room temperature using excimer laser radiation to ablate mixed graphite metal targets is described. Our deposition conditions are in contrast to other investigations on the pulsed laser deposition of carbon nanotubes that have employed high temperatures and high pressures. We find that the ...

To the present day, literature efforts at modeling laser propulsion impulse often used empirical models. Recently, a simple physical approach was demonstrated to be effective for predicting many practical properties of laser ablative impulse generation under vacuum. The model used photochemical mass removal and energy conservation to predict parameters such as the peak ...

A study of the effect of initial sample temperature on laser ablation of a copper sample at ambient air pressure by a 1064 nm, 10 ns laser pulse with energies of 11 and 15 mJ (2.7-3.2 GW/cm2) is carried out. The sample is uniformly heated by a heating element up to 600 K. Spectral emission of plasma is measured at different initial ...

A study of the gas dynamics of the vapor plume generatedduring laser ablation was conducted including a counterpropagatinginternal shock wave. The density, pressure, and temperature distributionsbetween the external shock wave front and the sample surface weredetermined by solving the integrated conservation equations of mass,momentum, and energy. The ...

A study of the gas dynamics of the vapor plume generated during laser ablation was conducted including a counterpropagating internal shock wave. The density, pressure, and temperature distributions between the external shock wave front and the sample surface were determined by solving the integrated conservation equations of mass, momentum, and energy. The ...

The expansion dynamics of Sm{sub 1-x}Nd{sub x}NiO{sub 3} excimer laser ablation plume in background oxygen atmosphere has been investigated using a fast ICCD imaging. The laser fluence was fixed at 2 J{center_dot}cm{sup -2} and the surrounding ambient gas pressure was varied from vacuum to 50 mbars. The imaging data is used to create ...

... Accession Number : ADD254681. Title : Influence of Laser Irradiation and Ambient Gas in Preparation of PZT Films by Laser Ablation. ...

The structural performance of several candidate ablatives for the uptake section of the Navy's Vertical Launching System is investigated. The uptake is modeled using a fixed-fixed beam-loaded by a uniform pressure. Beam displacement field equations are solved, assuming that the ablatives exhibit bimodular behavior in tension and ...

Epitaxial thin films of nitrogen-doped p-ZnTe were grown on single-crystal, semi-insulating Ga-As substrates via pulsed laser ablation of a stoichiometric ZnTe target. Both low pressure nitrogen ambients and high vacuum were used. Results of in situ reflection high energy electron diffraction (RHEED) and time-resolved ion probe ...

Formation of carbon nanoclusters in a single-laser-pulse created ablation plume was studied both in vacuum and in a noble gas environment at various pressures. The developed theory provides cluster radius dependence on combination of laser parameters, properties of ablated material, and type and pressure of an ...

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron ...

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron ...

The interaction of 180 femtosecond (fs), 775 nm laser pulses with the surface of aluminum under controlled gas atmospheres at ambient pressure has been investigated to study material redeposition, residual surface roughness, and ablation rate. The effect of using various gases to protect the surface of the material appears to interfere ...

Atmospheric pressure imaging mass spectrometry is a rapidly expanding field that offers advantages in the ability to study biological systems in their native condition, simplified sample preparation, and high-throughput experiments. In laser ablation electrospray ionization (LAESI), the native water molecules in biological tissues facilitate sampling by a ...

When we irradiate targets with lasers, a variety of laser and target conditions can be realized. This is because we can use window materials to separate ambient pressure differences between the laser and the targets. When targets are irradiated with intense pulsed ion beams, such a window separation is not possible. Often, high vacuum ...

Atmospheric pressure imaging mass spectrometry is a rapidly expanding field that offers advantages in the ability to study biological systems in their native condition, simplified sample preparation, and high-throughput experiments. In laser ablation electrospray ionization (LAE-SI), the native water molecules in biological tissues facilitate sampling by a ...

Barium and barium oxide targets were irradiated at 248 nm with fluences ranging from 300 - 600 mJ/cm^2 in vacuum and 25 mTorr atmospheres of O_2, N_2, microwave discharged O_2. Time-integrated optical emission from the resulting plume was examined and compared to determine the fate of the Ba^+ ions produced as a result of the ablation process and/or reactions between plume ...

Optical measurements of the cadmium plasma produced by the fundamental, second, and third harmonics of a Nd:YAG laser are reported. The excitation temperature and ionic temperature have been determined from the Boltzmann plot and Saha equation, whereas the number density is estimated from the Stark broadened profile of the spectral lines. The variations in the excitation temperature and number ...

... TITANATES, *FERROELECTRIC MATERIALS, ABLATION, EXCIMERS, LASERS, MASS, PARAMETERS, PEROVSKITES, PRESSURE, RATES ...

... of the first rarefaction wave to the ablation surface after shock breakout. ... and the ablation surface is important for smoothing laser nonuniformities. ...

Ablation performance of glasslike carbons, pyrolytic graphite, and artificial graphite in stagnation

We examine the scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency with the wavelength of the laser, using a recent theoretical analysis of ablative laser driven implosions as a tool. Symmetrization by a hot atmosphere is most effective for long wavelength lasers, whereas ablation ...

An experimental study was conducted on the spatial distributions of hydrogen emission intensities from low-pressure plasmas generated by laser ablation of zircaloy-4 and black stone targets in nitrogen and helium ambient gases. In addition to confirming the previously observed intensity enhancement effect in ...

An experimental study was conducted on the spatial distributions of hydrogen emission intensities from low-pressure plasmas generated by laser ablation of zircaloy-4 and black stone targets in nitrogen and helium ambient gases. In addition to confirming the previously observed intensity enhancement effect in ...

Size distributions of Si and ZnTe nanoparticles produced by low energy density ArF (193 nm) pulsed laser ablation into ambient gases were measured as a function of the gas pressure and target-substrate separation, D{sub ts}, using atomic force microscopy (AFM) and high resolution scanning electron microscopy (HRSEM). For low energy ...

Interaction between impact-induced vapor clouds and the ambient atmosphere may play an important role in planetary evolution. In the companion study, Sugita and Schultz [2003] conducted a series of impact experiments detailing observation of this interaction process. The laboratory experiments using diatomic molecular spectroscopy provide several well-defined observational ...

An ambient pressure lockout system includes a pressure tube wherein one end of the tube is adapted to open into a low pressure environment, and the other end of the tube is adapted to open into an ambient high pressure environment. A pair of spaced apart ...

Radiation hydrodynamics simulations were used to study the effect of plastic ablators in laser-driven shock experiments. The sensitivity to composition and equation of state was found to be 5-10% in ablation pressure. As was found for metals, a laser pulse of constant irradiance gave a pressure history which ...

The 1D Lagrangian fluid code MEDUSA has been used to study the process of laser driven ablation for a variety of irradiances and laser wavelengths. Values are given for physically important parameters such as ablation pressure and coronal temperature as a...

The irradiation of a steel surface in atmospheric pressure ambient was performed to study the surface nanostructuring resulting from the formation of a backward-deposited layer. The dynamics of the plume expansion and of the nanoparticle deposition process were investigated by in situ time-resolved optical analysis. Scanning electron microscopy and atomic ...

We report on picosecond UV-laser processing of hexagonal boron nitride (BN) at moderately high pressures above 500 bar. The main effect is specific to the ambient gas and laser pulse duration in the ablation regime: when samples are irradiated by 5 or 0.45 ps laser pulses in nitrogen gas environment, multiple nucleation of a new ...

A mobility spectrometer was used to characterize gas-phase ions produced from laser ablation of solids in air at 100 degrees C and at ambient pressure with a beam focused to a diameter of

We report on the deposition of carbon nanotubes and nano-onions at room temperature using excimer laser radiation at 248 nm to ablate mixed graphite-nickel/cobalt targets in the presence of O2 gas. The carbon nanotubes are frequently seen to connect individual onions and have a wall thickness on the order of 20-25 nm, with an overall external tube diameter of 100-200 nm. These ...

Pulsed laser generated Fe plasma plumes have been studied near the target surface using time-resolved imaging. A fast gated intensified CCD camera is used to capture the images with a gate width of 2 ns. The plasma plumes were generated using a Q-switched Nd-YAG laser at 1064 nm with a fluence of �2 kJ/cm2. The expansion studies were done up to a distance of about 5 mm from the target surface. ...

For remote isotope analysis of low-decontaminated trans-uranium (TRU) fuel, absorption spectroscopy has been applied to a laser-ablated plume of lanthanide elements. To improve isotopic selectivity and detection sensitivity of the ablated species, various experimental conditions were optimized. Isotope-selective absorption spectra were measured by ...

For remote isotope analysis of low-decontaminated trans-uranium (TRU) fuel, absorption spectroscopy has been applied to a laser-ablated plume of lanthanide elements. To improve isotopic selectivity and detection sensitivity of the ablated species, various experimental conditions were optimized. Isotope-selective absorption spectra were measured by ...

In order to get a better inside in the reactive Pulsed Laser Deposition of nitride thin films, we performed time- and space-resolved plasma diagnostics during ablation of Ti, Al and C targets in low pressure nitrogen containing atmospheres using pulsed nanosecond UV lasers. In the case of carbon, thin films of CxNy were deposited on silicon substrates and ...

Semiconducting tin oxide can be successfully deposited by means of the laser ablation technique. In particular by ablating metallic tin in a controlled oxygen atmosphere, thin films of SnOx have been deposited. The partial oxygen pressure at which the films are deposited strongly influences both the stoichiometry and the structural ...

A novel breathing sphere model was developed in order to make microscopic molecular dynamics simulations tractable for laser ablation. The results of the simulations have allowed us to distinguish between desorption and ablation, predict velocity distributions of ablated particles, predict the fluence dependence of the ...

This letter describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection method for surface sampling and ionization with subsequent mass spectral analysis. A commercially available autosampler was adapted to produce a liquid droplet at the end of the syringe injection needle ...