... of the propellant ablation under plasma effect based on ... Knudsen layer and the hydrodynamic layer. ... indicate that the ablated mass increases with ...
DTIC Science & Technology
... an electrothermal chemical gun model include ... into the plasma-propellant interaction ... ELECTROTHERMAL CHEMICAL GUNS, ABLATION, MODELS ...
Optical near-field ablation-induced plasma characteristics David J. Hwang and Costas P December 2006 The physics of optical near-field based laser ablation plasmas is studied. A Cr thin metal film is ablated using visible nanosecond laser pulses coupled through an optical near-field fiber probe
E-print Network
The ablation-induced plasma physics at reduced ablation crater dimensions is experimentally investigated. Frequency doubled femtosecond laser pulses are tightly focused through objective lenses onto a Cr thin film coated on quartz wafer in order to obtain ablation craters of submicron lateral dimensions. Side-view ...
Energy Citations Database
The propagation of laser-induced shockwaves from ablation inside of cavities was determined from time-resolved shadowgraph images. The temperature and electron number density of the laser-induced plasma was determined from spectroscopic measurements. These properties were compared to those for laser ...
Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times ...
The influence of pulsed laser ablation of an aluminum target on the nitrogen plasma produced by electron cyclotron resonance (ECR) microwave discharge has been studied by optical emission spectroscopy (OES) with time and space resolution. The continuous wave (CW) feature of the optical emissions from the ECR nitrogen plasma turns to ...
PubMed
In the nanosecond laser ablation regime, absorption of laser energy by the plasma during its early stage expansion critically influences the properties of the plasma and thus its interaction with ambient air. These influences can significantly alter spect...
National Technical Information Service (NTIS)
Develop a fiber-optic imaging probe for microanalysis of solid samples. Design a time-resolved plasma imaging system to measure the development of the LIBS signal. Setup a laboratory system capable of timing two lasers independently, for optimizing and characterizing dual-pulse LIBS. Compare the development of laser-induced plasmas ...
Develop a fiber-optic imaging probe for microanalysis of solid samples; Design a time-resolved plasma imaging system to measure the development of the LIBS signal; Setup a laboratory system capable of timing two lasers independently, for optimizing and characterizing dual-pulse LIBS; Compare the development of laser-induced plasmas ...
DOE Information Bridge
We investigate the mechanism of laser-induced plasma-assisted ablation (LIPAA), by which high-quality and high-efficiency ablation of transparent materials, such as glass, can be performed with a single conventional pulsed laser. The laser-induced plasma ...
We report the effect of 'plasma pipe' formation on pulsed laser ablation of organic polymers in air under normal conditions. Ablation of polymers (PMMA, polyimide) is carried out in a wide range of CO2 laser fluences with special attention to plasma formation in the ablation products. Evolution ...
NASA Astrophysics Data System (ADS)
The aim of this work is to elucidate the ablation-induced plasma physics for chemical species analysis by laser-induced breakdown spectroscopy at higher spatial resolution. To accomplish this, the effect of the laser spot size on the laser ablation-induced plasma characteristics is ...
We report on the results of analysis of parameters of a laser-induced plasma, which were obtained using emission diagnostics of a laser torch plasma from a CuInSe2 polycrystalline target. The density and temperature of electrons in a laser torch with a complex composition are determined. The laser-induced ...
The structure and evolution of the laser-induced vapor plume and shockwave were measured from femtosecond time resolved shadowgraph images. By changing the wavelength of the probe beam (400 and 800 nm), differences in the opacity of the vapor plume were measured as a function of delay time from the ablation laser pulse. The evolution of the temperature and ...
Nanosecond laser ablation of tungsten (W) exposed to helium plasma is investigated using optical emission spectroscopy. Submicrometer-sized holes/bubbles are formed on the surface of W when it was exposed to the helium plasma at a sufficiently high temperature (>~1500-1600 K). The emissions from a virgin W (before the helium ...
Laser ablation has become a dominant technology for directsolid sampling chemical analysis. Commonly used detection modalitiesinclude LIBS (laser induced breakdown spectroscopy) for directspectroscopic analysis from the laser-induced plasma at the samplesurface,and ICPMS (inductively coupled ...
... Descriptors : *ABLATION, *ATMOSPHERE ENTRY, *PLASMA ... AND MAGNETOHYDRODYNAMICS RADIOFREQUENCY WAVE PROPAGATION. ...
... Title : Experimental Scaling Laws for Mass-Ablation Rate, Ablation Pressure in Planar Laser-Produced Plasmas With Laser Intensity, Laser ...
... LASER BEAMS, *NUCLEAR FUSION, ABLATION, PLASMAS ... LASERS, MOMENTUM TRANSFER, PLASMA DIAGNOSTICS, FOILS(MATERIALS ...
... Accession Number : ADA306854. Title : Comparative Evaluation of Ablating Materials in ARC Plasma Jets. Corporate Author ...
An interesting physical phenomenon of laser-induced plasma backward growth has been found for long nanosecond (ns) laser pulse ablation, which has been rarely reported. Time-resolved observation shows that the plasma bottom appears to be detached from the ablated target surface shortly after ...
Although femtosecond laser cell surgery is widely used for fundamental research in cell biology, the mechanisms in the so-called low-density plasma regime are largely unknown. To date, it is still unclear on which time scales free electron and free radical-induced chemical effects take place leading to intracellular ablation. In this ...
Mechanisms of the deposition of carbon thin films by the laser ablation of graphite were investigated by monitoring the plasma emission. Parameters such as electron density, ionization temperature, and vibrational temperature during plasma growth were evaluated as a function of the laser power density and the surrounding atmosphere. ...
Many laser ablation applications such as laser drilling and micromachining generate cavity structures. The study of laser ablation inside a cavity is of both fundamental and practical significance. In this dissertation, cavities with different aspect ratios (depth/diameter) were fabricated in fused silica by laser micromachining. Pulsed laser ...
We developed a model of early-stage plasma induced by intense femtosecond laser ablation of metals in an ambient gas. We consider a 100 fs FWHM, 800 nm wavelength laser pulse irradiating a copper target in 1 atm nitrogen environment. Electron and lattice temperature of laser-irradiated target were calculated based on a two-temperature ...
A new concept of pulse laser ablation target were proposed. The idea is two-fold; that is, the target material to be ablated is a very thin layer deposited on a surface of some substrate material. As the substrate material, we will choose a transparent material like polymer or glass. Through the transparent material, a pulse laser beam is focused onto the ...
of the Lawrence Berkeley National Laboratory. (1) Laser pulse is applied; (2) Induced plasma plume expands into the anbient gas; (3) particle formation occurs from solid-sample...
Science.gov Websites
... are pointed out. electrothermal guns, plasma discharge, plasma devices, plasma jets. Descriptors : *PLASMA DEVICES ...
Laser-induced plasma spectroscopy (LIPS) is a new analytical method for materials characterization that uses the laser as the sampling and the excitation source. In LIPS, a short-pulsed laser is tightly focused onto a sample surface. During the pulse of the laser, the surface is heated beyond the latent heat of vaporization and material is ...
Details of the increase of the plasma density following a pellet injection have been measured with high temporal resolution (16 {mu}s) and the parallel expansion of ablated matter modeled with a four-fluid hydrodynamic code. The driving force of the expansion is the parallel pressure gradient, progressively balanced by the compression of the background ...
Reproducible and sensitive elemental analysis of solid samples is a crucial task in areas of geology (e.g. microanalysis of fluid inclusions), material sciences, industrial quality control as well as in environmental, forensic and biological studies. To date the most versatile detection method is mass-spectroscopic multi-element analysis. In order to obtain reproducible results, this requires ...
Time-resolved ultrasonic studies revealed a second, delayed ablative pressure pulse after the first primary plasma pressure pulse in a silicon wafer irradiated by a UV nanosecond laser. The intensity-dependent delay time for the second pulse indicates the existence of a corresponding intensity-dependent homogeneous vapor bubble nucleation time in the ...
A combined theoretical and experimental effort to model various physical processes during laser ablation of solids (silicon) using a variety of computational techniques is described. Currently the focus of the modeling is on the following areas: (a) rapid transformations through the liquid and vapor phases under possibly nonequilibrium thermodynamic conditions ...
Thin films of La0.6Ca0.4CoO3 were grown by pulsed laser ablation with nanosecond and femtosecond pulses. The films deposited with femtosecond pulses (248 nm, 500 fs pulse duration) exhibit a higher surface roughness and deficiency in the cobalt content compared to the films deposited with nanosecond pulses (248 nm, 20 ns pulse duration). The origin of these pronounced ...
The finite resistivity code Frontier-MHD [1] is used to simulate the ablation rate of refueling pellets, including the effect of electrostatically induced ExB rotation of the ablation cloud about its symmetry axis parallel to the magnetic field [2]. The radial electric field E is set up as a consequence of charge and current ...
The effect of an artificially deposited liquid film on a laser-ablated metal surface at near-threshold laser fluences is presented. Experiments utilizing a Q-switched Nd:YAG laser (wavelength=1064 nm, full width at half maximum=6 ns) reveal that deposition of a liquid film results in substantial reduction of ablation threshold and enhancement of ...
Laser-induced breakdown spectroscopy (LIBS) technique based on the analysis of typical for different materials integral relations calculated from broadband spectra of plasma is developed. The broadband spectrum (250-800 nm) is captured in real-time with fast spectrometer during the laser ablation process. By this way real-time ...
The possibilities of the use of autodyne detection of backscattered radiation for studies of nonstationary mass transfer upon ablation of biotissues by pulses from a CO{sub 2} laser are demonstrated. It is shown that the differences in the character of the laser-induced mass removal are caused by structural features of biotissues. (interaction of laser ...
Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear ...
We have performed Pulsed Laser Ablation (PLA) of ceramic materials at laser wavelength {lambda}L=308 nm and fluence IL=2.2 J/cm{sup 2}. Using fluorescence diagnostics we have measured both the electron density ne and plasma temperature Te. We have interpreted the experimental results within the frame of a model accounting for the most relevant ionization ...
... Accession Number : ADD852990. Title : Excimer Laser Induced Ablation of Polyetheretherketone, Polyimide, and Polytetrafluoroethylene. ...
Using picosecond time-resolved shadowgrams and interferograms, we measured the lateral expansion of an early stage ablation plasma induced by a 1064 nm, 35 ps laser pulse on a copper target. The plasma was found to have an electron density on the order of 10{sup 20} cm{sup -3} near the target surface. Prior to the ...
The experimental study of absorption in silicon in infrared and visible spectral ranges, where the photon energy is less or more than the bandgap width, is performed by means of the ultrafast interferometry technique. The exactly solvable model in the electromagnetic of heterogeneous lossy plasma layer was developed. The density of carriers, their frequency of collisions, ...
... Accession Number : ADA536231. Title : Spectroscopy Measurements on Ablation Testing in High Enthalpy Plasma Flows. ...
... ABLATIVE MATERIALS, *SPACE PROPULSION, SYMPOSIA, VACUUM, KNUDSEN NUMBER, MICROPULSATIONS, PLASMA ENGINES ...
... Descriptors : *ABLATION, *ACCELERATION, *LASER BEAMS, *FUSION( MELTING), HEAT TRANSFER, PLASMAS(PHYSICS), HIGH VELOCITY ...
... levels of radio frequency and microwave ... Descriptors : *ABLATION, *CARBON, *EMISSION ... PRODUCTION, PULSES, RADIOFREQUENCY, SIDES ...
... follows: The Grantee will investigate A.) Ablation of viscous polymers-- Liquid fuels ... measurements on the ablation of viscous polymer solutions will ...
... Descriptors : *THRUSTERS, ABLATION, REPRINTS, HIGH PRESSURE, RADIATION ABSORPTION, PLASMA ENGINES, BOUNDARY LAYER ...
... the ablation front using a discontinuity model identical ... corresponds to the ablative pressure slowly decreasing from ... absorption in the plasma corona ...
A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate ...
Single pulse laser ablation sampling with inductively coupled plasma mass spectrometry (ICP-MS) was assessed for accurate chemical analysis. Elemental fractionation (e.g. Pb/U), the quantity of ablated mass (crater volume), ICP-MS intensity and the particle contribution (spike signal) during single pulse ablation ...
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 ...
Combined laser ablation and pulse modulated radio-frequency (RF) discharge for deposition of CNalpha films was studied by the use of optical emission spectroscopy. Chemically active nitrogen was produced by RF discharge, concentrated between two small electrodes. Influence of RF power, nitrogen pressure, modulation frequency and pulse rate on nitrogen species production was ...
In ICF implosions, a laser irradiation induces a shock wave propagating through the target. During the shock transit time, the ablation front travels at a constant velocity, and any surface perturbations (caused by nonuniform laser irradiation and a finite surface roughness) could grow due to the Richtmyer-Meshkov (RM)-type instability. Later, when a ...
We study the basic mechanisms leading to ablation by femtosecond laser pulses using a simple two-dimensional molecular-dynamics model. For moderate fluences (under the threshold for plasma formation) we show that four different mechanisms can induce ablation. Two of these are photo-mechanical (front side spallation ...
... Single- and Double-Pulse Laser Ablation ... Optical emission characteristics of carbon plasma produced by single- and double-pulse laser ablation ...
... Title : Nonuniformities in Laser-Ablated Plasma. ... Calculations indicate that this may be due to thermal self-focusing of hot spots in the laser. ...
... 4. TITLE AND SUBTITLE ABLATION AND PLASMA FORMATION DURING DIRECTED ENERGY TESTING 5a. CONTRACT NUMBER 5b. ...
... Accession Number : ADA498298. Title : Ablation and Plasma Formation During Directed Energy Testing. Descriptive Note : Final technical rept. ...
To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved ...
A simple plasma-energy-balance model, along with its derivation, is presented for calculating the impulse from targets in a vacuum exposed to single-pulse, optical lasers. Figures demonstrate that throughout most of the range of interest, results from the model agree well with experimental data and LASNEX radiation-hydrodynamic computer code calculations. The model assumes ...
It is argued that phase explosion plays an important role during high-power laser ablation. A theoretical model which includes the effect of an expanding mass plasma has been developed to describe the process of phase explosion during the interactions of a high-power nanosecond laser pulse on an aluminum target. For a laser with a 3-ns pulse duration, if ...
We have investigated the temporal and spatial evolution of the ablation process induced in fused silica upon irradiation with single 120 fs laser pulses at 800 nm. Time-resolved microscopy images of the surface reflectivity at 400 nm reveal the existence of a transient plasma distribution with annular shape surrounding the visible ...
Laser-induced Plasma Spectroscopy was performed during the spines ablation of Opuntia by using Nd:YAG microsecond laser pulses. The results show strong absorption in Glochids that causes the intense electronic noise on the spectra. This process is consider suitable for practical elimination of spines in alimentary products like ...
We present a simple theoretical model for the emission from double pulse laser-induced plasmas that was developed to better understand the processes and factors involved in enhancement of plasma emission. In this model, the plasma emission is directly proportional to the square of plasma ...
Deuterium pellet injection has been used in experiments on DIII-D to investigate several aspects of plasma confinement and density control. The measured fueling efficiency and deposition profiles from pellets injected from the low field side horizontal midplane show a large discrepancy with pellet ablation theory, while the penetration depth compares ...
Laser materials processing has been used in the industry for drilling, cutting, welding, scribing, and etc. In most of the scientific papers, the authors assume that the laser energy imparted to the material is transformed into heat. This induces phase transformation as melting, fusion, sublimation, or vaporization. It is known that the atoms and ions are produced in high ...
Most of the previous studies on nanosecond (ns) laser-induced plasma typically use relatively short ns laser pulses (pulse duration less than ~30 to 50 ns). In this paper, relatively long ns laser pulses with 200 ns duration have been used, and the produced plasma during metal ablation in air at atmospheric ...
Photoluminescence (PL) is observed from ZnO nanoclusters formed in ZnO plasma due to cooling of plasma species by passing a collimated beam of fourth harmonic (266 nm) of Nd:YAG (yttrium aluminum garnet) laser through ZnO plasma formed by third harmonic (355 nm) of Nd:YAG laser. A shift of 42 meV in peak position of PL profile of ZnO ...
An Nd-YAG laser (1064 nm, 120 mJ, 8 ns) was focused on various types of solid organic samples such as a black acrylic plate, a black polyvinyl chloride plastic sheet, and a methoxy polyaniline film coated on the surface of a glass substrate, under a surrounding air pressure of 2 Torr. A modulated plasma technique was used to study the mechanism of excitation of the emission of ...
Theories published on pellet ablation phenomena are reviewed. Some inconsistencies are shown to exist in some of the studies available. Models are developed and estimates are given for pellet ablation rates in hot plasmas with and without magnetic fields ...
An improved model for CO{sub 2} laser ablation impulse in polyoxymethylene and similar polymers is presented that describes the transition effects from the onset of vaporization to the plasma regime in a continuous fashion. Several predictions are made for ablation behavior.
The effect of laser energy on formation of a plasma inside a cavity was investigated. The temperature and electron number density of laser-induced plasmas in a fused silica cavity were determined using spectroscopic methods, and compared with laser ablation on a flat surface. Plasma temperature ...
Plasmas induced by UV laser ablation have been studied and analysed using time-of-flight measurements. A KrF laser beam of 23 ns FWHM time duration was focused into Si and Nb targets with a moderate laser fluence of 2 J/cm2. A suitable theoretical expressions were derived for fitting the recorded ion current under the assumption of a ...
The state-of-the-art and trends of development in atomic spectrometry with microwave-induced plasmas (MIPs) since the 1998s are presented and discussed. This includes developments in devices for producing microwave plasma discharges, with reference also to miniaturized systems as well as to progress in sample introduction for ...
Temporally resolved emission spectra (360-630 nm) of carbon ablation plasmas produced during laser hole boring by a 25-ns duration 1-J ruby laser pulse are presented. The emitted line radiation originates from C/sup +++/ to C/sup +/ depending upon the time relative to the laser pulse. Plasma temperatures of 12-14 eV during the laser ...
A dramatic change in plasma characteristics, as well as a significant increase in the quantity of ablated mass were observed at a laser power density threshold of 20 GW/cm{sup 2}. The electron number density and temperature of the laser-induced plasma show dramatic changes in their nonlinear behavior in the range ...
Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. ...
In this paper, we report a survey of two of the large number of possible practical applications of the laser ablation performed by an ultra-short pulse laser, namely pulsed laser deposition (PLD) and fs/ns dual-pulse laser-induced breakdown spectroscopy (DP-LIBS). These applications differ from those using just longer pulsed lasers as a consequence of the ...
... COMPUTER PROGRAMMING, RADIOFREQUENCY PULSES, INSTRUMENTATION, ABLATION, MICROWAVES, ELECTROMAGNETIC ...
... Title : EFFECTS OF POROSITY AND STRUCTURE OF GRAPHITE MATERIALS ON ABLATION IN ARC GENERATED PLASMAS,. ...
... of the ambient gases and ablation of the heat ... PLASMA PHYSICS AND MAGNETOHYDRODYNAMICS RADIOFREQUENCY WAVE PROPAGATION ...
... MICROWAVE COMMUNICATIONS, HALOGENS, ABLATION, ELECTRICAL IMPEDANCE ... ELECTRONIC EQUIPMENT RADIOFREQUENCY WAVE ...
Thermal plasmas and lasers have been widely used in medicine to cut, ablate and cauterize tissues through heating; in contrast, non-thermal plasma produces no heat, so its effects can be selective. In order to exploit the potential for clinical applications, including wound healing, sterilization, blood coagulation, and cancer ...
PubMed Central
... power dissipation in the plasma. ... Descriptors : *GUNS, VELOCITY, ABLATION, MAGNETIC ... RESISTANCE, INJECTORS, GUN MUZZLES, BORES ...
... Descriptors : *INTERACTIONS, *LASER BEAMS, *FOILS(MATERIALS ... Subject Categories : LASERS AND MASERS PLASMA PHYSICS AND ...
The use of fluorescence spectroscopy to discriminate atherosclerotic from normal tissue is limited by a lower sensitivity for calcified than noncalcified atherosclerotic plaque (65% vs. 93%, respectively). To evaluate plasma emission as a means to detect calcified plaque, 325 normal and atherosclerotic cadaveric aortic sites were irradiated through a 100-micron silica fiber in ...
The one-dimensional expansion into vacuum of ion-electron plasma produced by laser ablation is investigated. The ions considered as an ideal fluid are governed by a fluid model where charge quasineutrality is assumed to prevail, while electron density follows a non-Maxwellian distribution. Showing that the expansion can be described by a self-similar ...
Pellet material deposited in a tokamak plasma experiences a drift towards the low field side of the torus induced by the magnetic field gradient. Plasma fuelling in ITER relies on the beneficial effect of this drift to increase the pellet deposition depth and fuelling efficiency. It is therefore important to analyse this phenomenon in ...
The influence of distances between the lens and a pure lead target on the breakdown spectroscopy of plasmas induced by a Nd:YAG laser ablation was studied at atmospheric pressure. The electron density, the electron temperature and the self-absorption were analysed when the distances were less than the focal length (6.5 cm). The maximal ...
The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m(2). States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the ...
The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m2. States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the ...
The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10(sup 13) W/cm(sup ...
Polydimethylsiloxane (PDMS) is fundamental materials in the field of biotechnology. Because of its biocompatibility, microfabricated PDMS sheets are applied to micro-reactors and microchips for cell culture. Conventionally, the microstructures were fabricated by means of cast or imprint using molds, however it is difficult to fabricate the structures at high aspect ratios such as ...
This work focuses on the study of the plumes obtained in the double pulse orthogonal Laser Induced Breakdown Spectroscopy (LIBS) in the pre-ablation configuration using both spectroscopic and shadowgraphic approaches. Single and double pulse LIBS experiments were carried out on a brass sample in air. Both the distance of the air plasma ...
In the present paper, the effect of lens-to-sample distance (LTSD) on the radiative properties from the plasma induced by a high-energy neodymium glass laser (approximately 25J) in the argon ambient gas at a pressure of 0.43 x 10(5) Pa was studied. The experimental results showed that when the focus point of the focusing lens (f = 130 mm) shifts above and ...
In this work we report on the properties of the ablation plume and the characteristics of the films produced by ultra-fast pulsed laser deposition (PLD) of TiO2 in vacuum. Ablation was induced by using pulses with a duration of ?300 fs at 527 nm. We discuss both the composition and the expansion dynamics of the TiO2 ...
Nonlinear light scattering appearing upon air breakdown induced by high-power ultrashort pulses (110 � 5200 fs) from a Ti:Al2O3 laser is studied. As a result of forward scattering, the beam profile is severely deformed, which is accompanied by spectral conversion of the incident radiation to a series of shorter-wavelength peaks extending into the visible spectral range. ...
Surface ablation with nanosecond laser pulses was applied to preservation, cleaning and compositional identification of objects of cultural value. On one hand, treatments of fabrics, coins, bones, and other archeological objects are shown, as well as applications to the preservation of covers, front of books and old manuscripts made in rag paper. Damage fluence thresholds for ...
Pellet ablation rates computed with the help of different ablation models are compared. For investigating the response of the plasma to the injected pellet, the ablation models are combined with a multiregime tokamak transport code. The results indicate that the ionization dynamics of the ...
The particle size distribution and composition of nanosecond laser-generated aerosols from brass samples in atmospheric argon has been measured by low-pressure impaction and subsequent quantitative analysis of the aerosols by total reflection X-ray fluorescence. Ablation was performed applying a Nd:YAG laser at 1.06 microm both without and with a prepulse ...
Plasma-mediated ablation (PMA) removes tissue by developing an electrically induced plasma layer between the instrument and target tissue. Charged particles within the plasma field then accelerate toward the tissue, breaking the molecular bonds within the top layer of tissue. Thermal damage to ...
... AD-A232 046 MODELING OF THE LASER-INDUCED THERMAL RESPONSE, ABLATION, AND FRAGMENTATION OF BIOLOGICAL TISSUE ...
... Accession Number : ADA117697. Title : A Semi-Analytical Model for Laser-Induced Ablation of Fibre-Resin Composites,. ...
... Award Number: W81XWH-06-0461 TITLE: A Novel Combination of Thermal Ablation and Heat-Inducible Gene therapy for Breast Cancer Treatment ...
... 0461 TITLE: A Novel Combination of Thermal Ablation and Heat-Inducible Gene Therapy for Breast Cancer Treatment ...
... Abstract : High intensity focused ultrasound (HIFU) has been developed as an ... thermal ablation and HIFU-induced gene therapy is interpretedboth ...
Single pulses exported from high-energy neodymium glass laser were used to act on the same position of soil sample surface repeatedly, and the plasma emission spectra generated from sequential laser pulse action were collected by spectral recording system. The experimental results show that the laser-induced soil plasma radiation was ...
We have investigated high-frequency ultrasound generated by single laser pulses in thin (50 {mu}m) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80 fs and 270 ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ...
Heat-flow-induced dynamic overpressure at the perturbed ablation front of an inertial confinement fusion target can stabilize the ablative Richtmyer-Meshkov-like instability and mitigate the subsequent ablative Rayleigh-Taylor (RT) instability. A series of experiments was performed on the OMEGA laser to quantify ...
Here we report on the recent developments and upgrades of our Laser-Induced Breakdown Spectroscopy setups and their different modification for high-resolution mapping. Mapping capabilities of Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry are compared. ...
Numerous atomic analytes in plumes produced by pulsed-laser ablation fluoresced upon ArF laser irradiation. The likely mechanism was photoexcitation to levels near the ionization limit. These levels were dense and were probably broadened by the extreme plume density to allow efficient absorption of 193 nm photons. The excited atoms relaxed to intermediate states as the plume ...
Co67Cr7Fe4Si8B14 magnetic alloy and Cd25Mn25Te50 semimagnetic semiconductor targets were ablated in vacuum with a XeCl excimer laser at different fluences. The ejected material was collected onto unheated silicon substrates at different angles with respect to the target normal. Compositional investigations were performed on the deposited films. In addition, during ...
We compared the analytical performance of ultraviolet femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The benefit of ultrafast lasers was evaluated regarding thermal-induced chemical fractionation, that is otherwise well known to limit LA-ICPMS. Both lasers had a Gaussian beam energy ...
A model, formerly proposed and utilized to understand the formation of laser induced breakdown spectroscopy (LIBS) plasma upon irradiation with nanosecond laser pulses at different fluences and wavelengths, has been extended to the irradiation with femtosecond laser pulses in order to control the fractionation mechanisms which heavily affect the ...
... I. ablated materials consisting of ions and excited species ir- ... tween different figures. The wavelength indicator on the ialned from such profiles. ...
... MODELS, *STEADY STATE, *LASER TARGET INTERACTIONS, VELOCITY, ABLATION ... PLASMAS(PHYSICS), LASERS, LASER BEAMS, MASS ...
... Ablation losses of aluminum, polyethylene, phenolic, and grease, caused by impacting high-speed neon from a coaxial plasma gun were measured ...
The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec,
... Accession Number : ADD460302. Title : Adequacy Of Metal Ablation Process With Laser Radiation And A Shock-Compressed Plasma. ...
Ablative overlays were evaluated via a plasma-arc simulation of the ascent pulse on the leading edge
NASA Technical Reports Server (NTRS)
Experimental evidence supporting the importance of ablation in plasma armature railguns is presented. Experiments conducted using the HYVAX and MIDI-2 railguns are described. Several indirect effects of ablation are identified from the experimental results. An improved ablation model of plasma ...
The purpose of this paper is to present a model for ablation due to a plasma flash in cylindrical symmetry. The model of ablation speed of the coaxial material is based on the integral method of the heat equation which basically involves the idea of a thermal layer. It is first shown that an important step in the process is the heating ...
The experiment of Bauer, et al. (1982) is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat ...
Experimental evidence of the appearance of a proper periodic dynamics in a plasma plume created by pulsed laser ablation is considered as a hint for the presence of a self-organization scenario that explains similar phenomena observed in plasma diodes.
The effect of additional laser irradiation on the optical emission of laser ablated carbon plasma have been examined to define plasma conditions for the controlled synthesis of carbon structures.
... 29 22 Plasma Arc Tests 31 23 Plasma Arc Ablation Rutes at 50 Btu/ft 2-sec 33 23 Plasma Arc Ablation Rates at 50 Btu/ft2-sec 33 ...
Spectral atomic emission intensity from laser-induced plasmas (LIPs) exhibits excellent correlation with atomic emission intensity in the inductively coupled plasma (ICP) for a wide variety of materials and laser powers. Laser ablation sampling with introduction into an lCP for chemical analysis has, among other ...
The temperature response to laser radiation varying in intensity over time was studied. Ablation of the fusion material due to laser beam induced pressure effects is considered. Thermal effects are studied in the case of plasma enhanced coupling and for v...
Optical diagnostics of laser ablation plasma has provided the opportunity to realize quantitative calibration-free analyses of solid, liquid and gaseous materials. The results presented confirm the suitability of the approach for routine practical applications of our laser instrumentation and calibration free algorithm, while at the same time simplifying ...
A variety of plasma treatments of polymer surfaces for improved adhesion are reviewed: noble and reactive gas treatment of fluoropolymers; noble and reactive treatment of polyolefins, and plasma-induced amination of polymer fibers. The plasma induced surface chemical and morphological changes are discussed, as are ...
We explore the evolution of metal plasma generated by high laser irradiances and its effect on the surrounding air by using shadowgraph images after laser pulse termination; hence the formation of laser supported detonation and combustion processes has been investigated. The essence of the paper is in observing initiation of chemical reaction between ...
Pulsed laser ablation is a process in which an intense laser pulse interacts with the matter producing plasma. The present work describes the theoretical work being conducted in the past for the pulsed laser ablation phenomenon. It incorporates the theoretical models being proposed by various researchers around the globe for pulsed ...
... Descriptors : *PLASMAS(PHYSICS), *LASER BEAMS, ABLATION ... Subject Categories : LASERS AND MASERS PLASMA PHYSICS AND ...
Magnetic fields in laser produced plasmas can be self-generated by the so-called ?nx?T effect and resistive electric fields associated with a neutralizing return current. The ?nx?T fields can be induced by the fluid vorticity originating at the ablation front and amplified by the Rayleigh-Taylor (RT) instability. They can also be ...
The physical mechanisms that enable short pulses of high-intensity ultraviolet laser radiation to remove tissue, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed laser irradiation was investigated by measuring and subsequently analyzing the stress transients generated by pulsed argon fluorine (ArF, lambda = 193 nm) ...
A laser nanodissection system for in vivo and in situ biological tissues is presented. A pulsed laser beam operating at a wavelength of 355 nm enables diffraction limited dissection, providing an optimal tool for intracellular nanosurgery. Coupled into a conventional inverted microscope and scanned across a field of up to 100�100 ?m2, this optical nanoscalpel performs in vivo photoablation and ...
The dynamics of the interaction between two plasmas induced by cross-beam pulsed-laser ablation was analyzed by time resolved optical emission spectroscopy and fast photography. The plasmas were created in vacuum by irradiating two perpendicular graphite targets with an excimer (248 nm) and a ...
