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1

Ionization Dynamics of Laser Ablation and a Laser Ablation-Assisted Ion Source  

Microsoft Academic Search

A new type of ion source has been developed which combines KrF excimer laser ablation and a pulsed power discharge. The ionization dynamics produced in the laser ablation of aluminum and iron, along with the laser-ablation -assisted-plasma-discharge (LAAPD) ion source have been characterized by numerous plasma diagnostics including a newly developed resonant ultraviolet interferometry (RUVI) diagnostic. Focusing a KrF excimer

Joel Staton Lash

1996-01-01

2

Ionization Dynamics of Laser Ablation and a Laser Ablation-Assisted Ion Source.  

NASA Astrophysics Data System (ADS)

A new type of ion source has been developed which combines KrF excimer laser ablation and a pulsed power discharge. The ionization dynamics produced in the laser ablation of aluminum and iron, along with the laser-ablation -assisted-plasma-discharge (LAAPD) ion source have been characterized by numerous plasma diagnostics including a newly developed resonant ultraviolet interferometry (RUVI) diagnostic. Focusing a KrF excimer laser (248 nm, 1 J, 4-10 J/cm^2, 40 ns) onto a solid iron or aluminum target generates the ablated material. The LAAPD ion source configuration employs an annular electrode in front of the grounded target. Simultaneous to the excimer laser striking the target, a pulse-forming network is discharged across the electrode-target gap. Peak discharge parameters of 3600 V and 680 A yield a peak discharge power of 1.3 MW through the laser-ablation plume. Both time-integrated and time-resolved optical emission spectroscopy show the laser ablation plume spectra dominated by neutral atom transitions with ion emission only occurring at early times (<100 ns). Discharge electron temperatures are inferred in the range of 1-3 eV while the laser ablation plume electron temperature is approximately 0.5 eV. With application of the discharge, ion optical emission is detected with significant contribution from Al III and Fe II transitions. The optical emission evolution closely follows the magnitude of the discharge plasma current, indicative of ohmic heating. Absorption photography shows decreased neutral atom absorption and enhanced ion absorption over that from only laser ablation when the discharge is applied. Resonant photographs also show the iron plume is very forward directed, while the aluminum plume expands more strongly in the radial direction. Iron neutral atom line-densities are measured with the RUVI diagnostic by tuning the dye laser near the 271.903 nm ground-state and 273.358 nm excited-state transitions, while iron singly-ionized line-densities are measured using the 273.955 and 263.105 nm excited-state transitions. The line-density, expansion velocity, temperature, and number of each species has been characterized as a function of time for laser ablation and the LAAPD. Data analysis, assuming a Boltzmann distribution, yields the ionization ratio rm(n_{i}/n_ {n}) and indicates substantial laser ablation plume ionization. With application of the discharge, the plume ionization ratio increases by a factor of ~5 to rm n_{i }/n_{n} of approximately 20. Ion line-densities in excess of 1 times 10^ {15} cm^{-2} have been measured implying peak ion densities of {~}1times 10^ {15} cm^{-3} consistent with values obtained from a Langmuir probe measurement.

Lash, Joel Staton

3

Targets on superhydrophobic surfaces for laser ablation ion sources  

NASA Astrophysics Data System (ADS)

Target preparation techniques for a laser ablation ion source at the Penning-trap mass spectrometer TRIGA-TRAP have been investigated with regard to future experiments with actinides. To be able to perform mass measurements on these nuclides considering their limited availability, an efficient target preparation technique is mandatory. Here, we report on a new approach for target production using backings, which are pretreated in a way that a superhydrophobic surface is formed. This resulted in improved targets with a more homogeneous distribution of the target material compared to standard techniques with unmodified backings. It was demonstrated that the use of these new targets in a laser ablation ion source improved the ion production significantly.

Renisch, D.; Beyer, T.; Blaum, K.; Block, M.; Düllmann, Ch. E.; Eberhardt, K.; Eibach, M.; Nagy, Sz.; Neidherr, D.; Nörtershäuser, W.; Smorra, C.

2012-06-01

4

Hafnium Oxide Film Synthesis via Laser Ablation Plasma Ion Deposition  

NASA Astrophysics Data System (ADS)

This research investigates the feasibility of synthesizing thin films of hafnium oxide via laser ablation plasma ion deposition (LAPID). HfO2 is of great interest as a high dielectric constant material in the semiconductor fabrication industry. Experiments are underway to deposit and implant films of hafnium and hafnium-oxide on silicon substrates. A KrF laser (400 mJ @ 248 nm) ablates solid Hf foils in an oxygen environment or sintered pellets of hafnium-oxide in vacuum. Silicon substrates can be biased (+ or -, either pulsed or DC) by voltages up to 10 kV for ion implantation and deposition. Experiments study correlations among parameters such as laser energy, film thickness, background gas pressure, film composition, and ion energy. Ablation plasma plumes are characterized by optical emission spectroscopy. Composition and morphology of deposited films are analyzed by SEM, TEM, X-ray Energy Dispersive Spectroscopy, X-ray Photoelectron Spectroscopy, X-ray diffraction and Atomic Force Microscopy. Film deposition rates are estimated to be on the order of 0.055 nm/pulse at a laser repetition rate of 15 pulses/s, equating to 8 nm/s.

Jordan, N. M.; Gilgenbach, R. M.; Wang, L. M.; Zhu, S.; Atzmon, M.; Lau, Y. Y.; Jones, M. C.

2006-10-01

5

Production and acceleration of ion beams by laser ablation  

SciTech Connect

In this work, we present a new pulsed laser ablation technique to obtain energetic ion beams. The accelerator we made is a compact device able to extract and accelerate the ionic components of plasma up to 160 keV per charge state. It is composed by a generating chamber containing an expansion chamber used like first electrode. Next, a second electrode connected to ground and a third electrode connected to negative voltage are used. The third electrode is used also as Faraday cup. By the analysis of the ion signals we studied the plume parameters such as TOF accelerated signals, charge state, and divergence.

Velardi, L.; Siciliano, M. V.; Delle Side, D.; Nassisi, V. [Department of Physics and I.N.F.N., LEAS Laboratory, University of Salento, Via Provinciale Lecce-Monteroni, 73100 Lecce (Italy)

2012-02-15

6

Mapping neutral, ion, and electron number densities within laser-ablated plasma plumes  

Microsoft Academic Search

Spatially and temporally varying neutral, ion and electron number densities have been mapped out within laser ablated plasma plumes expanding into vacuum. Ablation of a magnesium target was performed using a KrF laser, 30 ns pulse duration and 248 nm wavelength. During the initial stage of plasma expansion (t

I. Weaver; L. A. Doyle; G. W. Martin; D. Riley; M. J. Lamb; William G. Graham; T. Morrow; Ciaran L. Lewis

1998-01-01

7

A high-power laser ablation ion source for Penning trap studies of nuclear reaction products  

NASA Astrophysics Data System (ADS)

A state of the art Penning trap is being developed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University to make precision mass measurements of rare isotopes. The system relies on thermalizing nuclear reaction products in a helium-filled cell and then extracting them from the gas through ion-manipulation and differential pumping. Atomic ions and clusters are needed to calibrate various aspects of the entire system such as transport efficiency and the main magnetic field. High-power laser ablation has proven to be a successful method for producing a wide range of ions under various conditions, including atmospheric pressure. We have developed a laser ablation system to explore the production of test beams using a variety of targets. Laser ablation studies of C, Al, Au, Ag, Cu, Fe, and Zn were carried out in a test chamber with the second harmonic, 532 nm, from a Q-switched Nd:YAG laser. Many studies were carried out under vacuum using an ion-drift system and mass analysis in a quadrupole mass filter. The ablation target and laser optics were moved to the gas cell used to collect the nuclear reaction products and several ablation studies were performed. An overview of the laser-ablation system as well as some of the results of this work will be presented.

Davies, D. A.; Morrissey, D. J.; Bollen, G.; Lofy, P. A.; Ottarson, J.; Schwarz, S. C.

2007-04-01

8

Eclipse laser photodetachment method for avoiding probe surface ablation in negative ion measurement  

NASA Astrophysics Data System (ADS)

Direct laser irradiation to an electrostatic probe disturbs the negative ion signals of laser photodetachment (LPD) in helium-hydrogen plasmas, particularly when the electron density is considerably high. In order to analyse the characteristics and production mechanism of ablation signals, laser irradiation experiments were performed on a tungsten surface using helium plasmas. To prevent direct laser irradiation to the electrostatic probe tip, a thin wire is installed in the laser channel to form a laser shadow for the probe tip. The ablation signal disappears when the probe tip is fully eclipsed by the laser shadow. The influence of a screening object on the signal intensity of LPD is investigated by experiments and model calculations. It is confirmed that the LPD signal intensity is accurately estimated when some conditions are satisfied, even when a part of the collection region of photodetached electrons is overlapped by the shadow. It is an ablation-free LPD method that can be used to evaluate the negative ion density at a sufficient laser power, even when the ablation disturbs the LPD signals in the conventional LPD technique.

Kajita, Shin; Kado, Shinichiro; Tanaka, Satoru

2005-08-01

9

Extension of cutoff in high harmonic by using doubly charged ions in a laser-ablation plume  

Microsoft Academic Search

We report high-order harmonic generation from doubly charged ions in laser-ablation plasma produced by different prepulse intensities. At the prepulse intensity of 3.5x10¹° W cm², harmonics up to the 63rd order (12.62 nm wavelength, 98.3 eV photon energy) were obtained by using a laser-ablation titanium plume. From analysis of the harmonics and visible radiation from the laser-ablation titanium plume at

Masayuki Suzuki; Rashid A. Ganeev; Luc Bertrand Elouga Bom; Motoyoshi Baba; Tsuneyuki Ozaki; Hiroto Kuroda

2007-01-01

10

Excimer laser ablation mass spectrometry of inorganic solids: Chemical, matrix, and sampling effects on polyatomic ion yields  

Microsoft Academic Search

Positive ions formed directly by excimer laser ablation in vacuum of several lanthanide (Ln) and transition metal solid materials---including LnâOâ, LnâSâ, LnFâ, TaâOâ, ZrOâ, TiO, and TiOâ---were identified by time-of-flight mass spectrometry. Variations in ion yields were investigated as a function of the composition of the precursor material, laser irradiance, and ion sampling delay after ablation. The compositions of the

John K. Gibson

1995-01-01

11

Mapping neutral, ion, and electron number densities within laser-ablated plasma plumes  

NASA Astrophysics Data System (ADS)

Spatially and temporally varying neutral, ion and electron number densities have been mapped out within laser ablated plasma plumes expanding into vacuum. Ablation of a magnesium target was performed using a KrF laser, 30 ns pulse duration and 248 nm wavelength. During the initial stage of plasma expansion (t laser power densities on target in the range 1.3 - 3.0 X 108 W/cm2. Later in the plasma expansion (t equals 1 microsecond(s) ) simultaneous absorption and laser induced fluorescence spectroscopy has been used to determine 3D neutral and ion number densities, for a power density equal to 6.7 X 107 W/cm2. Two distinct regions within the plume were identified. One is a fast component (approximately 106 cm-1) consisting of ions and neutrals with maximum number densities observed to be approximately 30 and 4 X 1012 cm-3 respectively, and the second consists of slow moving neutral material at a number density of up to 1015 cm-3. Additionally a Langmuir probe has been used to obtain ion and electron number densities at very late times in the plasma expansion (1 microsecond(s) ablated using a Nd:YAG laser, 7.5 ns duration and 532 nm (2 (omega) ) wavelength, with a power density on target equal to 6 X 108 W/cm2. Two regions within the plume with different velocities were observed. Within a fast component (approximately 3 X 106 cms-1) electron and ion number densities of the order 5 X 1012 cm-3 were observed and within the second slower component (approximately 106 cms-1) electron and ion number densities of the order 1 - 2 X 1013 cm-3 were determined.

Weaver, I.; Doyle, L. A.; Martin, G. W.; Riley, D.; Lamb, M. J.; Graham, William G.; Morrow, T.; Lewis, Ciaran L.

1998-05-01

12

Real-time monitoring of laser ablation deposition of superconductors by fluorescence and secondary-ion spectra  

SciTech Connect

Fluorescence spectra and secondary-ion spectra for laser ablation of high-temperature metal-oxide superconductors are reported. These processes can be used to monitor a thin-film deposition process. The fluorescence spectra are more suitable for Y, Ba, and Ca ions. However, ion spectra can be used to monitor and identify Tl and Ca ions easier than by fluorescence spectra.

Chen, C.H.; McCann, M.P.; Phillips, R.C.

1988-12-26

13

Laser ablation of blepharopigmentation  

SciTech Connect

This article discusses laser ablation of blepharopigmentation in four stages: first, experimentally, where pigment vaporization is readily achieved with the argon blue-green laser; second, in the rabbit animal model, where eyelid blepharopigmentation markings are ablated with the laser; third, in human subjects, where the argon blue-green laser is effective in the ablation of implanted eyelid pigment; and fourth, in a case report, where, in a patient with improper pigment placement in the eyelid, the laser is used to safely and effectively ablate the undesired pigment markings. This article describes in detail the new technique of laser ablation of blepharopigmentation. Potential complications associated with the technique are discussed.

Tanenbaum, M.; Karas, S.; McCord, C.D. Jr. (Univ. of Miami School of Medicine, FL (USA))

1988-01-01

14

Theory of electron-ion energy transfer applied to laser ablation  

NASA Astrophysics Data System (ADS)

Electron-ion temperature equilibration will be considered for states of matter typically occurring during laser ablation that is for strongly heated electrons and densities similar and lower than the one in the solid. The focus will be on fluid systems after the melt of the lattice as these dominate the hydrodynamic phase of the ablation process. It is shown that simple expressions derived for dilute gases and plasmas become highly questionable for solid-density fluids whereas the electron-phonon picture is inapplicable as well. Instead, one has to consider the collective behavior of electrons and ions in the strongly coupled fluid. The strong inter-ionic forces also strongly affect the heat capacities applied in a two-temperature model. The results presented here are based on a quantum-statistical approach applying nonequilibrium Green's functions.

Vorberger, J.; Gericke, D. O.

2012-07-01

15

Ablation plasma ion implantation  

NASA Astrophysics Data System (ADS)

The novel hybrid technique, Ablation Plasma Ion Implantation (APII), has been characterized and optimized for ion implantation and/or thin film deposition. In APII, a solid target is ablated by a laser; the resulting plasma plume is the source of ions, which are accelerated to high energy by a negative bias voltage imposed on the substrate. The ions are implanted into the substrate, and the neutral atoms in the ablation plume deposit on the substrate in the form of a thin film. Two configurations of APII are characterized and compared. The parallel target-substrate configuration yields ion-beam-assisted deposition and/or ion implantation, and the perpendicular target-substrate configuration yields pure ion implantation mode. A novel theory of the ion matrix sheath has been developed for APII. The ion current predicted by the Child-Langmuir sheath theory matches well with the experimental ion current. Two different target-substrate orientations have been compared for APII. Parallel target-substrate orientation yields ion-beam-assisted-deposition and ion implantation; to prevent arcing, a laser-voltage delay of several microseconds is required for this mode. For the optimized perpendicular target-substrate orientation, the laser can be fired during the voltage pulse, thereby accelerating ions to full energy. Furthermore, the ion dose is higher than that of the parallel target-substrate orientation by a factor of two. The parameters of plasma plumes have been thoroughly characterized by numerous diagnostics, which include electrical characteristics, optical emission spectroscopy, dye laser resonance absorption photography, resonant/non-resonant interferometry, and Langmuir probe. The total number of ions measured by Langmuir probe, and resonant interferometry, is in the range of 1014 ions per laser pulse. Ion dose measured by plasma diagnostics, has been correlated to the ion dose obtained from material analysis, including sputtering yield calculation, X-ray Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy. The retained and delivered ion doses are in the range of 10 12/cm2 per pulse, which is favorable compared to the ion dose obtained from conventional Plasma Immersion Ion Implantation (PHI). The APII ion implantation efficiency is estimated to be about 2%. Ion acceleration and implantation was demonstrated for both of the APB configurations. The feasibility of APII was verified by Cross-Sectional Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. For parallel target-substrate configuration, the average deposition rate is 0.0075 nm/shot for the Ti -10 kV APII film. Atomic Force Microscopy implemented at Timken Research Lab indicates that the -4 kV APII film has the smoothest surface. Scratch tests performed at Timken Research lab also prove that APR produces excellent film adhesion.

Qi, Bo

16

Chemical characterization of microparticles by laser ablation in an ion trap mass spectrometer  

SciTech Connect

We are developing a new technique for the chemical characterization of microparticles based upon the use of electrodynamic traps. The electrodynamic trap has achieved widespread use in the mass spectrometry community in the form of the ion trap mass spectrometer or quadrupole ion trap. Small macroscopic particles can be confined or leviated within the electrode structure of a three-dimensional quadrupole electrodynamic trap in the same way as fundamental charges or molecular ions by using a combination of ac and dc potentials. Our concept is to use the same electrode structure to perform both microparticle levitation and ion trapping/mass analysis. The microparticle will first be trapped and spatially stabilized within the trap for characterization by optical probes, i.e., absorption, fluorescence, or Raman spectroscopy. After the particle has been optically characterized, it is further characterized using mass spectrometry. Ions are generated from the particle surface using laser ablation or desorption. The characteristics of the applied voltages are changed to trap the ions formed by the laser with the ions subsequently mass analyzed. The work described in this paper focuses on the ability to perform laser desorption experiments on microparticles contained within the ion trap. Laser desorption has previously been demonstrated in ion trap devices by applying the sample to a probe which is inserted so as to place the sample at the surface of the ring electrode. Our technique requires the placement of a microparticle in the center of the trap. Our initial experiments have been performed on falling microparticles rather than levitated particles to eliminate voltage switching requirements when changing from particle to ion trapping modes.

Dale, J.M.; Whitten, W.B.; Ramsey, J.M.

1991-01-01

17

Dynamics of ions produced by laser ablation of several metals at 193 nm  

SciTech Connect

This work reports the study of ion dynamics produced by ablation of Al, Cu, Ag, Au, and Bi targets using nanosecond laser pulses at 193 nm as a function of the laser fluence from threshold up to 15 J cm{sup -2}. An electrical (Langmuir) probe has been used for determining the ion yield as well as kinetic energy distributions. The results clearly evidence that ablation of Al shows unique features when compared to other metals. The ion yield both at threshold (except for Al, which shows a two-threshold-like behavior) and for a fixed fluence above threshold scale approximately with melting temperature of the metal. Comparison of the magnitude of the yield reported in literature using other wavelengths allows us to conclude its dependence with wavelength is not significant. The evolution of the ion yield with fluence becomes slower for fluences above 4-5 J cm{sup -2} with no indication of saturation suggesting that ionization processes in the plasma are still active up to 15 J cm{sup -2} and production of multiple-charged ions are promoted. This dependence is mirrored in the proportion of ions with kinetic energies higher than 200 eV. This proportion is not significant around threshold fluence for all metals except for Al, which is already 20%. The unique features of Al are discussed in terms of the energy of laser photons (6.4 eV) that is enough to induce direct photoionization from the ground state only in the case of this metal.

Baraldi, G.; Perea, A.; Afonso, C. N.

2011-02-15

18

Laser ablation ion-storage time-of-flight mass spectrometry  

NASA Astrophysics Data System (ADS)

A new mass spectrometer system was developed for studying laser ablation and performing analytical chemistry. The system is based on an ion trap geometry used in ion-storage (IS) mode, coupled with a reflectron time-of-flight mass spectrometer (TOFMS). The LA-IS/TOF-MS can be used for MALDI or direct ionization of samples on a probe tip. The system configuration and related operating principles for accurately measuring low concentrations of isotopes will be described. Preliminary measurements identified ultra-trace contaminants of Ag, Sn, and Sb in a Pb target with single laser-shot experiments. Survey analyses of uranyl acetate, hair samples, and mushrooms demonstrated that this technology can be applied to a wide range of sample materials.

Russo, R. E.; Klunder, G. L.; Grant, P.; Andresen, B. D.

19

Laser-ablation processes.  

National Technical Information Service (NTIS)

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 ...

R. S. Dingus

1992-01-01

20

Laser-ablation processes  

SciTech Connect

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 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, R.S.

1992-05-01

21

Laser-ablation processes  

SciTech Connect

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 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, R.S.

1992-01-01

22

Laser ablation and static secondary ion mass spectrometry capabilities in the characterization of inorganic materials  

NASA Astrophysics Data System (ADS)

Recently, mass spectrometry techniques such as laser ablation and static secondary ion mass spectrometry (LA-MS and s-SIMS, respectively) have been successfully applied to the characterization of inorganic compounds in solid state phase: s-SIMS is known as a surface analytical technique whereas LA-MS involves atoms in a greater thickness (bulk). In the case of s-SIMS, the direct ejection of ions from the surface upon primary ion sputtering for ion fluence down to 10 13 ions/cm 2, leads to a simple and direct diagnostic by comparing the spectra to databases. On the opposite, characterization of inorganic compounds by means of LA-MS is not immediate due to the most detected ions are issued from complex gas phase reactions. This feature can be successfully applied to investigate matter transfer processes occurring during pulsed-laser deposition (PLD) experiments. By the mean of a systematic and comparative study of LA-MS and s-SIMS spectra for binary (Cu-O) or ternary (Fe-Cr-O) oxide systems, we demonstrate that both techniques are complementary to each other in the field of material science.

Aubriet, Frédéric; Poleunis, Claude; Chaoui, Nouari; Maunit, Beno??t; Millon, Eric; Muller, Jean-François; Bertrand, Patrick

2002-01-01

23

Secondary ion and laser ablation mass spectrometry for the quantitative characterization of styrene-butadiene copolymers.  

PubMed

Styrene-butadiene copolymers were analyzed by static secondary ion mass spectrometry (S-SIMS) and laser ablation Fourier transform ion cyclotron resonance mass spectrometry (LA-FTICRMS) to obtain quantitative information based on specific ions. Silver deposition was performed on polystyrene, butadiene rubber and styrene-butadiene rubber. Under these experimental conditions, new secondary ions were detected, in particular silver-cationized butadiene [M(butadiene) - Ag](+) and styrene [M(styrene) - Ag](+) monomers. In contrast, LA-FTICRMS experiments did not require pretreatment. At high laser power density, UV photons (193, 266 and 355 nm) allowed the detection of styrene and butadiene monomers at m/z 104 and 54, respectively. The use of the observed ions by SIMS or LA-FTICRMS ensures that quantitative information on the relative distribution of each monomer is obtained. However, the silver coating thickness in the SIMS experiment seems to have an important influence on the quantitative information obtained. For LA-FTICRMS experiments, the best results are obtained at a wavelength of 355 nm. PMID:12526006

Ruch, D; Muller, J F; Migeon, H N; Boes, C; Zimmer, R

2003-01-01

24

Laser ablation sampling  

Microsoft Academic Search

Laser ablation sampling provides significant benefits and capabilities for chemical analysis. It represents one of the most promising technologies for direct solid sample introduction. Despite the advantages, there are a number of issues that should be addressed to better understand and utilize this technology. Laser ablation itself is a complex process and is poorly understood, fundamentally. In this paper, we

Richard E Russo; Xianglei Mao; Oleg V Borisov

1998-01-01

25

Direct observation of aluminium ions produced via pulsed laser ablation in liquid: a 'turn-on' fluorescence study.  

PubMed

An Al metal plate was ablated by a pulsed Nd-YAG laser to produce nano-structured Al and gamma-Al(2)O(3) in deionized water without any surfactants or catalysts. In this study, direct evidence for the production of Al(3+) ions from the plasma plume is presented for the first time by characterizing the absorption and emission spectra of their [Al(salophen)](+) complex. Very interestingly, a remarkable increase in the fluorescence intensity was observed when the Al(3+) ions, produced via the pulsed laser ablation, complexed with the salophen ligand. This fluorescence 'turn-on' behaviour of [Al(salophen)](+) was investigated by DFT/TD-DFT calculations. Based on these results, mechanisms for the production of aluminium and alumina nanoparticles in the pulsed laser ablation in liquid (PLAL) process are proposed. PMID:23086109

Lee, Seulki; Ahn, Ahreum; Choi, Myong Yong

2012-10-19

26

Parametric evaluation of laser ablation and ionization time-of-flight mass spectrometry with ion guide cooling cell  

Microsoft Academic Search

A novel laser ablation and ionization time-of-flight mass spectrometer has been used for direct elemental analysis of alloys. The system was incorporated with an ion guide cooling cell to reduce the kinetic energy distribution for the purpose of better resolution. Parametric studies have been conducted on the system with respect to the buffer gas pressure and the distance from sample

Ding Peng; Jian He; Quan Yu; Lizhi Chen; Wei Hang; Benli Huang

2008-01-01

27

Chemical characterization of single particles by laser ablation/desorption in a quadrupole ion trap mass spectrometer  

SciTech Connect

Particles are introduced into the center of the space surrounded by the hyperbolic electrode surfaces of a quadrupole ion trap mass spectrometer. Ions are desorbed or ablated from the surfaces of the particles with laser pulses from a Nd:YAG laser as the particles fall through the trap. The ions are trapped and subsequently mass analyzed using the mass-selective instability mode of operation of the ion trap. Desorption experiments were performed with approximately 100 [mu]m silicon carbide particles with an average of a few nanograms of adsorbed trimethylphenyl-ammonium chloride, tetraphenylphosphonium bromide, or 2,4,6-trinitrotoluene per particle. A conservative detection limit of 0.7 fm per particle was determined for tetraphenylphosphonium bromide. Ablation experiments were performed with approximately 50 [mu]m nickel particles for isotope ratio measurements with good agreement between accepted and average experimental values. 22 refs., 5 figs., 1 tab.

Dale, J.M.; Yang, M.; Whitten, W.B.; Ramsey, J.M. (Oak Ridge National Lab., TN (United States))

1994-10-15

28

Mechanisms of ablation and ion formation in infrared laser mass spectrometry  

NASA Astrophysics Data System (ADS)

The studies described in this work take advantage of a unique infrared light source that allowed the exploration of previously uninvestigated vibrational modes and excitation densities, plus other laser systems that allowed us to compare the importance of pulse duration and electronic excitation in the ultraviolet. Results from several experiments were compared to current models of ion formation, allowing us to observe their applicability to our systems. One experiment assembled the most extensive range of excitation conditions to date to challenge the contribution of primary excitation events to the final ion yield. Despite the vastly different charged species and densities necessarily created, the results showed qualitatively similar spectra in all cases. We therefore concluded that the similarity of mass spectra alone offers a poor or incomplete picture from which to determine the operative mechanisms for ion formation, and that the observed ions are likely formed in the expanding plume. A second set of experiments utilized vibrational excitation of an intrinsic mode of a sample, eliminating the need for addition of an exogenous matrix. From a practical point of view, this represents a promising new approach to the analysis of complex mixtures. From a mechanistic point of view, the optical and thermal properties of the material, which control the degree of vibrational or electronic excitation upon irradiation, were found to determine the ablation pathways, which subsequently determines the ion formation process. This degree of excitation density, which determines whether ion formation occurs under conditions of thermodynamic equilibrium or kinetic control, may or may not determine the efficiency of ion production, depending on the particular vibrational mode under consideration.

Papantonakis, Michael Robert

29

The laser ablation ion funnel: Sampling for in situ mass spectrometry on Mars  

NASA Astrophysics Data System (ADS)

A considerable investment has been made by NASA and other space agencies to develop instrumentation suitable for in situ analytical investigation of extra terrestrial bodies including various mass spectrometers (time-of-flight, quadrupole ion trap, quadrupole mass filters, etc.). However, the front-end sample handling that is needed to collect and prepare samples for interrogation by such instrumentation remains underdeveloped. Here we describe a novel approach tailored to the exploration of Mars where ions are created in the ambient atmosphere via laser ablation and then efficiently transported into a mass spectrometer for in situ analysis using an electrodynamic ion funnel. This concept would enable elemental and isotopic analysis of geological samples with the analysis of desorbed organic material a possibility as well. Such an instrument would be suitable for inclusion on all potential missions currently being considered such as the Mid-Range Rover, the Astrobiology Field Laboratory, and Mars Sample Return (i.e., as a sample pre-selection triage instrument), among others.

Johnson, Paul V.; Hodyss, Robert; Tang, Keqi; Brinckerhoff, William B.; Smith, Richard D.

2011-04-01

30

Nanoparticles by Laser Ablation  

Microsoft Academic Search

This review concerns nanoparticles collected in the form of nanopowder or a colloidal solution by laser ablating a solid target that lies in a gaseous or a liquid environment. The paper discusses the advantages of the method as compared with other methods for nanoparticle synthesis, outlines the factors on which the properties of the produced nanoparticles depend, explains the mechanisms

N. G. Semaltianos

2010-01-01

31

Laser-ablation treatment of short-pulse laser targets: Toward an experimental program on energetic-ion interactions with dense plasmas  

NASA Astrophysics Data System (ADS)

This new project relies on the capabilities collocated at Los Alamos in the Trident laser facility of long-pulse laser drive, for laser-plasma formation, and high-intensity short-pulse laser drive, for relativistic laser-matter interaction experiments. Specifically, we are working to understand quantitatively the physics that underlie the generation of laser-driven MeV/nucleon ion beams, in order to extend these capabilities over a range of ion species, to optimize beam generation, and to control those beams. Furthermore, we intend to study the interaction of these novel laser-driven ion beams with dense plasmas, which are relevant to important topics such as the fast-ignition method of inertial confinement fusion (ICF), weapons physics, and planetary physics. We are interested in irradiating metallic foils with the Trident short-pulse laser to generate medium to heavy ion beams (Z = 20 45) with high efficiency. At present, target-surface impurities seem to be the main obstacle to reliable and efficient acceleration of metallic ions in the foil substrate. In order to quantify the problem, measurements of surface impurities on typical metallic-foil laser targets were made. To eliminate these impurities, we resorted to novel target-treatment techniques such as Joule-heating and laser-ablation, using a long-pulse laser intensity of [similar] 1010 W/cm2. Our progress on this promising effort is presented in this paper, along with a summary of the overall project.

Fernández, Juan C.; Hegelich, B. Manuel; Cobble, James A.; Flippo, Kirk A.; Letzring, Samuel A.; Johnson, Randall P.; Cort Gautier, D.; Shimada, Tsutomu; Kyrala, George A.; Wang, Yongqiang; Wetteland, Chris J.; Schreiber, Jörg

2005-09-01

32

Dynamics of laser driven, ablatively accelerated targets  

Microsoft Academic Search

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, - 10 to the 14th power w\\/sq cm), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic

J. Grun

1981-01-01

33

Direct Chemical Analysis of Solids by Laser Ablation in an Ion-Storage Time-of-Flight Mass Spectrometer  

SciTech Connect

A laser ablation/ionization mass spectrometer system is described for the direct analysis of solids, particles, and fibers. The system uses a quadrupole ion trap operated in an ion-storage (IS) mode, coupled with a reflectron time-of-flight mass spectrometer (TOF-MS). The sample is inserted radially into the ring electrode and an imaging system allows direct viewing and selected analysis of the sample. Measurements identified trace contaminants of Ag, Sn, and Sb in a Pb target with single laser-shot experiments. Resolution (m/{micro}m) of 1500 and detection limits of approximately 10 pg have been achieved with a single laser pulse. The system configuration and related operating principles for accurately measuring low concentrations of isotopes are described.

Klunder, G L; Grant, P M; Andresen, B D; Russo, R E

2003-09-29

34

Non-ablative lasers.  

PubMed

Non-ablative laser devices exert their effects by inducing dermal collagen remodeling while sparing the epidermis. The remodeling process is achieved by producing thermal energy in a controlled and precise fashion, which recruits fibroblasts and stimulates collagen production. Although these devices do not produce the same degree of improvement as traditional CO(2) or er:YAG resurfacing techniques, they are an excellent alternative for people seeking gradual aesthetic improvement with minimal downtime. They are also extremely well suited to patients with darker skin types. In this chapter, we review the various non-ablative devices currently available on the market, with an emphasis on safety profiles and efficacy. PMID:21865798

Ciocon, David H; Doshi, Daven; Goldberg, David J

2011-08-16

35

LASER ABLATION STUDIES OF CONCRETE  

EPA Science Inventory

Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-s...

36

Laser-ablation-plume thermalization dynamics in background gases studied by time-resolved imaging, spectroscopic, and ion probe diagnostics  

NASA Astrophysics Data System (ADS)

A combination of fast plasma diagnostics are utilized to probe the propagation of laser ablation plumes in vacuum and low-pressure background gases in order to understand key gas dynamic processes relevant to film growth by pulsed laser deposition. During expansion into low-pressure background gases, the ion flux in the plasma plume splits into fast and slow components over a limited range of distances and times. This general effect is presented here for the case of yttrium ablation into argon, a single-element target into an inert gas. Time- resolved optical absorption spectroscopy and optical emission spectroscopy are employed to simultaneously view the populations of both excited and ground states of Y and Y+ for comparison with intensified-CCD photography of the visible plume luminescence and ion flux measurements made with fast ion probes during this phenomenon. These measurements indicate that plume-splitting in background gases is consistent with momentum transfer from an initial, vacuum velocity distribution into a second, slowed velocity distribution initiated by scattering collisions between plume and background gas atoms. The fast distribution is exponentially attenuated in accordance with Beer's law, and the second, slowed distribution coalesces into a stable, propagating shock structure.

Geohegan, David B.; Puretzky, Alexander A.

1995-04-01

37

Laser ablation plume thermalization dynamics in background gases: Combined imaging, optical absorption and emission spectroscopy, and ion probe measurements  

SciTech Connect

Combined diagnostic measurements are employed to characterize the penetration of energetic ablation plumes through background gases during a key transitional regime in which the ion flux is observed to split into distinct fast and slowed components. This apparently general phenomenon occurs over a limited range of distances at ambient pressures typically used for PLD (pulsed laser deposition) and may be important to film growth by PLD because a ``fast`` component of ions can arrive at the probe (or substrate) with little or no delay compared to propagation in vacuum. At longer distances, this ``fast`` component is completely attenuated, and only slowed distributions of ions are observed. Interestingly, this ``fast`` component is easily overlooked in imaging studies because the bright plume luminescence occurs in the slowed distribution. Time- and spatially-resolved optical absorption and emission spectroscopy are applied to experimentally determine the composition of the ``fast`` and ``slow`` propagating plume components for a single-component target ablation (yttrium) into an inert gas (argon) for correlation with quantitative imaging and ion probe measurements. The yttrium/argon system was chosen because optical absorption spectroscopy of both Y and Y+ was simultaneously possible and the inert nature of argon. Experimental results for several other systems, including Si/Ar, Si/He, YBCO/O{sub 2} are presented to illustrate variations in scattering mechanisms.

Geohegan, D.B. [Oak Ridge National Lab., TN (United States). Solid State Div.; Puretzky, A.A. [Oak Ridge National Lab., TN (United States). Solid State Div.]|[Russian Academy of Sciences, Troitsk (Russian Federation). Inst. of Spectroscopy

1995-02-01

38

Ultrasonic characterization of laser ablation.  

National Technical Information Service (NTIS)

When a pulsed laser beam strikes the surface of an absorbing material, ultrasonic waves are generated due to thermoelectric expansion and, at higher laser power densities, ablation of the material. These sound generation mechanisms have been the subject o...

J. A. Smith K. L. Telschow

1991-01-01

39

A time-of-flight quadrupole mass spectrometric study of Cn)+(n=1-24 ions produced by laser ablation of a graphite target  

NASA Astrophysics Data System (ADS)

Mass spectral distributions and time-of-flight spectra of Cn+ (n=1-24) ions escaping from a carbon plasma plume generated by laser (lambda=1064 nm) ablation of a graphite target are analyzed to shed light on their formation mechanisms, expansion dynamics, and laser-plume interaction. In particular, by shining the whole or a slice of the plume with a photodissociation laser (lambda=266 nm) delayed with respect to the ablation laser, we examine the effects of the laser-plume interaction on the mass distribution as well as photodissociation channels of carbon-cluster cations. Also, we present experimental data that show a clear linear dependence of the velocities of Cn+ ions on 1/RADICAL:[[RADICAND:[M

Bae, Chang Hyun; Park, Seung Min

2002-09-01

40

Multiple target laser ablation system  

DOEpatents

A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film. 3 figs.

Mashburn, D.N.

1996-01-09

41

Laser ablation: LIBS and ICPMS  

SciTech Connect

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 plasma mass spectroscopy) in whichthe ablated aerosol is transported and excited in a secondary source.Each measurement approach dictates the laser parameters required foroptimum performance. Fundamental and experimental research studies haveled to significant improvements in performance metrics for laser ablationsolid sampling chemical analysis using both LIBS and ICPMS.

Russo, Richard E.; Gonzalez, Jhanis; Liu, Chunyi

2006-08-29

42

Characterization of surface modifications by white light interferometry: applications in ion sputtering, laser ablation, and tribology experiments.  

PubMed

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed. In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens. Specifically, we will discuss: i. Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion. ii. Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions. iii. Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests. Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained. PMID:23486006

Baryshev, Sergey V; Erck, Robert A; Moore, Jerry F; Zinovev, Alexander V; Tripa, C Emil; Veryovkin, Igor V

2013-02-27

43

Laser ablation in analytical chemistry - A review  

Microsoft Academic Search

Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution,

Richard E. Russo; Xianglei Mao; Haichen Liu; Jhanis Gonzalez; Samuel S. Mao

2001-01-01

44

Laser ablation based fuel ignition  

DOEpatents

There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition. 3 figs.

Early, J.W.; Lester, C.S.

1998-06-23

45

Laser ablation based fuel ignition  

DOEpatents

There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition.

Early, James W. (Los Alamos, NM); Lester, Charles S. (San Juan Pueblo, NM)

1998-01-01

46

Laser Ablation and Thin Film Deposition  

NASA Astrophysics Data System (ADS)

One of the most versatile deposition techniques in solid-state physics and analytical chemistry is the vaporization of condensed matter using photons. A short-pulsed high-power laser beam is focused onto a sample surface thereby converting a finite volume of a solid instantaneously into its vapor phase constituents such as ions and neutrals. Subsequently, the vapor moves away from the target at a high velocity and can be sampled either to grow a film or being analyzed by various spectroscopic techniques. In this chapter, the focus is on general properties of pulsed laser ablation relevant for solid-state physics like the initial ablation processes, plume formation, and plume properties. Next, oxide thin film growth will be discussed and the growth of LaAlO3/SrTiO3 heterostructures is presented as one example of tailoring oxide interfaces with surprising properties. The final discussion is on the topic of polymer ablation.

Schneider, Christof W.; Lippert, Thomas

47

Study of Cluster Anions Generated by Laser Ablation of Titanium Oxides: A High Resolution Approach Based on Fourier Transform Ion Cyclotron Resonance Mass Spectrometry  

Microsoft Academic Search

Laser ablation of titanium oxides at 355 nm and ion–molecule reactions between [(TiO2)x]–• cluster anions and H2O or O2 were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source.\\u000a The detected anions correspond to [(TiO2)x(H2O)yOH]– and [(TiO2)x(H2O)yO2]–• oxy-hydroxide species with x?=?1 to 25 and y?=?1, 2, or 3 and were formed by a two

Nicolas Barthen; Eric Millon; Frédéric Aubriet

2011-01-01

48

Ablation of metals by ultrashort laser pulses  

Microsoft Academic Search

Ablation of Fe, Al, Ni, and Cu by laser pulses at durations of 0.1, 1, and 5 ps is investigated experimentally. The laser fluence used vaires from below the ablation threshold up to 100 J\\/cm2. The ablation rate depends on the laser pulse duration at laser fluences above several J\\/cm2 as the shorter pulse produces higher ablation rate. A change

Nikolay N. Nedialkov; Petar A. Atanasov; Detlef Breitling; G. Heusel; Friedrich Dausinger

2005-01-01

49

Dynamics of laser driven, ablatively accelerated targets  

NASA Astrophysics Data System (ADS)

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, - 10 to the 14th power w/sq cm), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic pendula have been tested and calibrated in the experimental environment. A novel double-foil technique has been developed and used to study the velocity of the accelerated target. Using measurements of plasma energy, velocity, and momentum, we determined the scaling with irradiance and the absolute magnitudes of the ablation pressure, velocity and ablation depth (or mass ablation rate). These results are insensitive to laser spot-size effects that may introduce error under some experimental conditions. They imply that the hydrodynamic efficiency and initial thickness of targets accelerated to fusion velocities are weak and strong functions of absorbed irradiance respectively. Thus, target thickness and irradiance may be varied as necessary to alter the pellet-aspect-ratio or to increase laser nonuniformity smoothing with only small changes in hydrodynamic efficiency. We have determined that the accelerated target is composed of a high pressure, high density region preceeded by a low pressure, low density plasma. We have measured the velocity of the high density region and found that it agrees with target velocities predicted from the ablation parameters using a simple rocket model. We accelerated targets over distances many times their own thickness to velocities of 100 km/sec with no apparent breakup.

Grun, J.

1981-05-01

50

Picosecond laser ablation for silicon micro fuel cell fabrication  

NASA Astrophysics Data System (ADS)

We have investigated laser ablation as a microfabrication approach to produce micro fuel cells (MFCs) in silicon. Picosecond pulses (15 ps) at a wavelength of 355 nm are used to make all of the MFC structures. To assess the benefits and drawbacks of laser ablation, reference cells have been produced by deep reactive ion etching (DRIE) using matching geometries. Ablated and etched cells have been evaluated and compared side by side. Our conclusion is that picosecond laser ablation is very well suited for MFC fabrication. The ablated cells match or excel DRIE-microfabricated cells in terms of current and power densities. Ablated MFCs achieved 47.6 mW cm-2 of power density and 121 mA cm-2 current density.

Scotti, Gianmario; Trusheim, Daniel; Kanninen, Petri; Naumenko, Denys; Shulz-Ruhtenberg, Malte; Snitka, Valentinas; Kallio, Tanja; Franssila, Sami

2013-05-01

51

Solid material evaporation into an ECR source by laser ablation.  

National Technical Information Service (NTIS)

In an effort to explore new methods of producing ion beams from solid materials, we are attempting to develop a laser-ablation technique for evaporating materials directly into an ECR ion source plasma. A pulsed NdYAG laser with approximately 25 watts ave...

R. Harkewicz J. Stacy J. Greene R. C. Pardo

1993-01-01

52

Simulation of Double-Pulse Laser Ablation  

SciTech Connect

We investigate the physical reasons of a strange decrease in the ablation depth observed in femtosecond double-pulse experiments with increasing delay between the pulses. Two ultrashort pulses of the same energy produce the crater which is less than that created by a single pulse. Hydrodynamic simulation shows that the ablation mechanism is suppressed when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The modeling of the double-pulse ablation for different delays between pulses confirms this explanation.

Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R. [Joint Institute for High Temperatures of RAS, Izhorskaya 13 Bldg 2, Moscow, 125412 (Russian Federation); Itina, Tatian E. [Laboratoire Hubert Curien, UMR CNRS 5516, 18 rue Benoit Lauras, Bat. F, 42000, St-Etienne (France)

2010-10-08

53

Dynamics of Laser-Driven Ablatively Accelerated Targets  

Microsoft Academic Search

The characteristics of ablation plasma from planar targets, driven by long Nd: glass laser pulses (4 nsec, < 10('14) W\\/cm('2)), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic pendula have been tested

Jacob Grun

1981-01-01

54

Dynamics of laser driven, ablatively accelerated targets. Memorandum report  

Microsoft Academic Search

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, < 10 to the 14th power w\\/sq cm), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic

Grun

1981-01-01

55

Plume dynamics in femtosecond laser ablation of metals  

SciTech Connect

In femtosecond laser ablation the plume has two components: a faster-moving plasma part and a slower nanoparticle plume which contains most of the ablated material. This paper describes the results of experiments to comprehensively characterize the plume in laser ablation of Ni with {approx_equal}300 fs pulses at 527 nm. Both single-pulse and double-pulse irradiation was used. The laser ablation depth was measured using white light interferometry. The dynamics of the plasma part of the ablation plume was measured using Langmuir ion probes. The shape of the overall ablation plume was recorded by depositing a thin film on a transparent substrate and measuring the thickness distribution. The expansion of the plasma plume is well described by the Anismov isentropic model of plume expansion. Just above the ablation threshold, the nanoparticle plume is also well described by the Anisimov expansion model. However, at higher fluence a wider plume is formed, perhaps due to the pressure exerted by plasma. For double-pulse ablation it is observed that as the second pulse is delayed beyond {approx_equal}20 ps the ablation depth is reduced and the ion yield is increased. This behaviour is due to reheating of the nascent plasma plume produced by the first pulse. This generates a pressure pulse that acts as a tamper which impedes the fragmentation and ablation of deeper layers of material.

Donnelly, T.; Lunney, J. G. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Amoruso, S.; Bruzzese, R.; Wang, X. [Coherentia CNR-INFM and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Fedrico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126, Napoli (Italy)

2010-10-08

56

Basic ablation phenomena during laser thrombolysis  

Microsoft Academic Search

This paper presents studies of microsecond ablation phenomena that take place during laser thrombolysis. The main goals were to optimize laser parameters for efficient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate for

Ujwal S. Sathyam; Alan Shearin; Scott A. Prahl

1997-01-01

57

Laser ablation at the hydrodynamic regime  

NASA Astrophysics Data System (ADS)

Laser ablation of several metals and PVC polymer by high energy nanosecond laser pulses is investigated experimentaly. Visualization by shadowgraphy revealed the dynamics of the discontinuities in ambient air and ablation plume above the target surface, while surface profiling allowed for determination of the ablated mass.

Gojani, Ardian B.

2013-04-01

58

Study of cluster anions generated by laser ablation of titanium oxides: a high resolution approach based on Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

Laser ablation of titanium oxides at 355 nm and ion-molecule reactions between [(TiO(2))(x)](-•) cluster anions and H(2)O or O(2) were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO(2))(x)(H(2)O)(y)OH](-) and [(TiO(2))(x)(H(2)O)(y)O(2)](-•) oxy-hydroxide species with x=1 to 25 and y=1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO(2))(x)](-•) cluster anions as was previously reported, and (2) ion-molecule reactions during ion storage. Reactions of some [(TiO(2))(x)](-•) cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O(2) loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data. PMID:21472569

Barthen, Nicolas; Millon, Eric; Aubriet, Frédéric

2011-02-08

59

Ionization in vacuum ultraviolet F2 laser ablated polymer plumes  

NASA Astrophysics Data System (ADS)

An experimental investigation of ion generation in the 157-nm vacuum ultraviolet (VUV) F2 laser ablation of three selected polymers glycidyl azide polymer (GAP), a triazene polymer (TP6) and polyimide is described. An ion collector probe is used to determine the relative ion yield and white-light interferometry of ablated surfaces to ascertain mass-removal levels. The findings indicate that ions are generated under the action of the VUV laser pulse at fluences down to at least as low as the threshold for material removal. A two-photon photoionization model is proposed that provides a good description of the results.

Dyer, P. E.; Pervolaraki, M.; Walton, C. D.; Lippert, T.; Kuhnke, M.; Wokaun, A.

2008-03-01

60

Picosecond laser ablation of thin copper films  

Microsoft Academic Search

The ablation process of thin copper films on fused silica by picosecond laser pulses is investigated. The ablation area is characterized using optical and scanning electron microscopy. The single-shot ablation threshold fluence for 40 ps laser pulses at 1053rnm has been determinated to Fthres=172rmJ\\/cm2. The ablation rate per pulse is measured as a function of intensity in the range of

J. Jandeleit; G. Urbasch; H. D. Hoffmann; H.-G. Treusch; E. W. Kreutz

1996-01-01

61

Analyte response in laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

The dependence of analyte sensitivity and vaporization efficiency on the operating parameters of an inductively coupled plasma\\u000a mass spectrometer (ICPMS) was investigated for a wide range of elements in aerosols, produced by laser ablation of silicate\\u000a glass. The ion signals were recorded for different carrier gas flow rates at different plasma power for two different laser\\u000a ablation systems and carrier

Zhongke Wang; Bodo Hattendorf; Detlef Günther

2006-01-01

62

SIMS study of plumes generated from laser ablation of polymers  

Microsoft Academic Search

Plumes generated by ablation of polymer targets using a third-harmonic Nd:YAG laser under different atmospheres (air, N 2 and He) were deposited on a H-terminated silicon substrate. The chemical composition and distribution of deposited ablation debris were measured using time-of-flight secondary-ion mass spectrometry. Mass-resolved images show that the size and shape of the plume is dependent on the laser pulse

Z. L. Li; S. Z. Yow; L. Lui; N. L. Yakovlev; Y. Sun; E. J. Swenson; P. M. Moran

2004-01-01

63

Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP–MS with multiple ion counters  

Microsoft Academic Search

This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC–ICP–MS)—a Nu Plasma\\u000a HR—equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination\\u000a of the 235U\\/238U, 236U\\/238U, 145Nd\\/143Nd, 146Nd\\/143Nd, 101Ru\\/(99Ru+99Tc) and 102Ru\\/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a

Sergei F. Boulyga; Thomas Prohaska

2008-01-01

64

Ablation of metals by ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

Ablation of Fe, Al, Ni, and Cu by laser pulses at durations of 0.1, 1, and 5 ps is investigated experimentally. The laser fluence used vaires from below the ablation threshold up to 100 J/cm2. The ablation rate depends on the laser pulse duration at laser fluences above several J/cm2 as the shorter pulse produces higher ablation rate. A change of the ablation regime with the laser fluence increase is also observed. The presence of molten material is clearly expressed at fluences above 10 J/cm2 for all pulse durations used. These effects can be referred to the contribution of the electron heat diffusion in the distribution of the absorbed energy. The traces of solidified molten material suggest for realizations of melt ejection mechanism of ablation.

Nedialkov, Nikolay N.; Atanasov, Petar A.; Breitling, Detlef; Heusel, G.; Dausinger, Friedrich

2005-04-01

65

Dynamics of Laser Driven, Ablatively Accelerated Targets.  

National Technical Information Service (NTIS)

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, < 10 to the 14th power w/sq cm), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics inclu...

J. Grun

1981-01-01

66

Laser mass spectrometric studies of high temperature superconductor ablation  

SciTech Connect

Laser ablation of bulk High Temperature Superconductor (HTS) material promises to provide a useful means of producing high quality HTS thin films. Mass spectrometric probes of the ablation plume provide a microscopic understanding of the ablation event and plume development as well as providing a process monitor for the thin film production. Detection of the nascent ions in the plume provides real time analytical information, e.g., identification of impurities, major and minor ablation species, etc. The common contaminants sodium and strontium have been easily detected by this technique in a variety of different HTS bulk materials. In contrast, detection of the ablated neutral species by Resonance Ionization Mass Spectrometry (RIMS) provides physical information about the ablation process. Time-of-flight/RIMS detection of Cu, Y, and BaO ablated from YBa{sub 2}Cu{sub 3}O{sub x} indicates the ablation involves post-desorption gas phase collisions, thereby influencing the ablation chemistry and dynamics (e.g., angular and velocity distributions). Approximately equal velocities are observed for all neutral species at constant ablation laser fluence. 17 refs., 4 figs.

Estler, R.C.; Nogar, N.S.

1990-01-01

67

Pulsed infrared laser ablation and clinical applications  

NASA Astrophysics Data System (ADS)

Sufficient light energy deposited in tissue can result in ablation and excessive thermal and mechanical damage to adjacent tissues. The goals of this research are to investigate the mechanisms of pulsed infrared laser ablation of tissue, to optimize laser parameters for minimizing unnecessary damage to healthy tissue, and to explore the potential of using pulsed infrared lasers for clinical applications, especially laser lithotripsy. A dual-channel optical low coherence reflectometer was implemented to measure the expansion and collapse velocities of a Q-switched Ho:YAG (? = 2.12 ?m) laser-induced cavitation in water. Cavitation wall velocities up to 11 m/s were measured with this technique, and the results were in fair agreement with those calculated from fast-flash photographic images. The dependence of ablation threshold fluence on calculus absorption was examined. Preliminary results indicated that the product of optical absorption and ablation threshold fluence, which is the heat of ablation, remained constant for a given urinary calculus type and laser pulse duration. An extended study examined the influence of optical absorption on pulsed infrared laser ablation. An analytical photothermal ablation model was applied and compared to experimental ablation results using an infrared free-electron laser at selected wavelengths between 2.12 ?m and 6.45 ?m Results were in good agreement with the model, and the ablation depths of urinary calculi were highly dependent upon the calculus optical absorption as well as light attenuation within the intrapulse ablation plume. An efficient wavelength for ablation corresponded to the wavelength of the Er:YAG laser (? = 2.94 ?m) suggested this laser should be examined for laser lithotripsy. Schlieren flash photography, acoustic transient measurements with a piezoelectric polyvinylidene-fluoride needle-hydrophone, mass loss measurements, and chemical analyses were employed to study the ablation mechanisms of the free-running pulsed Ho:YAG laser in lithotripsy. Results indicated that a photothermal ablative process with concomitant chemical decomposition of calculus components occurred. This discovery dispelled the hypothesis that laser lithotripsy fragments calculus by means of shockwaves. Finally, the Er:YAG laser was explored for use in laser lithotripsy. Preliminary mass loss measurements suggested that the Er:YAG laser was more efficient than the Ho:YAG laser for lithotripsy.

Chan, Kin Foong

68

PULSED LASER ABLATION OF CEMENT AND CONCRETE  

EPA Science Inventory

Laser ablation was investigated as a means of removing radioactive contaminants from the surface and near-surface regions of concrete from nuclear facilities. We present the results of ablation tests on cement and concrete samples using a pulsed Nd:YAG laser with fiber optic beam...

69

Direct coupling of a laser ablation cell to an AMS  

NASA Astrophysics Data System (ADS)

In rare cases, cleaned samples can be directly inserted into a negative ion source of an AMS and still meet the requirements for long-term and stable measurements. We present the coupling of a laser ablation system to the gas ion source of an AMS system (MICADAS, ETH Zurich) for direct and continuous CO2 introduction. Solid carbonate samples like stalagmites or corals are suitable sample materials, which can be ablated and decomposed continuously using a pulsed laser focused onto the surface of a solid sample, which is placed in an airtight ablation cell. CO2 formed during the ablation of a CaCO3 sample is continually flushed with He into the gas ion source. The production rate of CO2 can be adjusted via the laser pulse repetition rate (1–20 Hz), the crater diameter (1–150 ?m) and the energy density applied (0.2–3 mJ/pulse) of the laser (frequency quintupled Nd:YAG at 213 nm with 5 ns pulse duration). In our first test, measurements of one sample with known age were replicated within one sigma. Blanks showed 5% contamination of modern carbon of yet unknown origin. In order to develop LA-AMS into a routine sampling tool the ablation cell geometry and settings of the gas ion source have to be further optimized.

Wacker, L.; Münsterer, C.; Hattendorf, B.; Christl, M.; Günther, D.; Synal, H.-A.

2013-01-01

70

Laser ablation-inductively coupled plasma-mass spectrometry: Examinations of the origins of polyatomic ions and advances in the sampling of particulates  

SciTech Connect

This dissertation provides a general introduction to Inductively coupled plasma-mass spectrometry (ICP-MS) and laser ablation (LA) sampling, with an examination of analytical challenges in the employment of this technique. It discusses the origin of metal oxide ions (MO+) in LA-ICP-MS, as well as the effect of introducing helium and nitrogen to the aerosol gas flow on the formation of these polyatomic interferences. It extends the study of polyatomic ions in LA-ICP-MS to metal argide (MAr+) species, an additional source of possible significant interferences in the spectrum. It describes the application of fs-LA-ICP-MS to the determination of uranium isotope ratios in particulate samples.

Witte, Travis

2011-11-30

71

Electron beam ablation versus laser ablation: plasma plume diagnostic studies  

Microsoft Academic Search

Experiments have been performed to compare XeCl laser ablation plume characteristics to those produced by electron beam ablation. Potential advantages of electron beams include higher electrical efficiency (?30%), and the ability to process materials with high optical reflectivity or transparency. The electron beam is generated by a channelspark with parameters: peak voltage of 15–20 kV, current of 1.5–1.7 kA, and

S. D. Kovaleski; R. M. Gilgenbach; L. K. Ang; Y. Y. Lau; J. S. Lash

1998-01-01

72

Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion  

SciTech Connect

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 deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

2004-03-23

73

Feasibility of characterizing laser-ablated carbon plasmas via planar laser induced fluorescence  

SciTech Connect

Planar laser induced fluorescence (PLIF) imaging can potentially assess ion distributions and coupling in the context of super-Alfvenic ablation plasma expansions into magnetized background plasmas. In this feasibility study, we consider the application of PLIF to rapidly expanding carbon plasmas generated via energetic laser ablation of graphite. By utilizing hydrodynamic and collisional-radiative simulations, we identify schemes accessible to commercially available tunable lasers for the C I atom, the C II ion, and the C V ion. We then estimate the signal-to-noise ratios yielded by the schemes under reasonable experimental configurations.

Bondarenko, A. S.; Schaeffer, D. B.; Everson, E. T.; Constantin, C. G.; Clark, S. E.; Niemann, C. [Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, California 90095 (United States)

2012-10-15

74

Velocity and metastable state population distributions of laser-ablated neodymium  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectroscopy has been employed to characterize a plume produced in nanosecond laser ablation of metallic neodymium. Kinetic energy distributions of ions and neutrals in the plume were investigated as functions of processing parameters such as laser fluence and ambient gas pressure. Population distributions of metastable levels in the ablated atoms were also measured. These investigations provide preliminary data for the design of a new type of resonance photo-ionization laser ion source.

Wang, Haiming; Miyatake, Hiroari; Ohba, Hironori; Saeki, Morihisa; Miyabe, Masabumi; Shibata, Takemasa; Iimura, Hideki

2004-10-01

75

Femtosecond laser ablation ICP-MS  

SciTech Connect

Femtosecond laser ablation was investigated for direct solid sample chemical analysis. The phonon relaxation time in a solid is of the order of 100 fs, which is the same as the laser pulse duration. For such excitation, there should be little time for the matrix to experience a ''temperature'' during the laser pulse. If the surface explodes before the photon energy is dissipated as heat in the lattice, the ablation process should produce stoichiometric vapor (elemental fractionation should be negligible). Based on this hypothesis, NIST glasses were ablated using 100 fs laser pulses at 800 nm, with subsequent elemental analysis using the ICP-MS. Pb and U intensities, and Pb/U ratios in the ICP, were measured during repetitively femtosecond-pulsed ablation. These data show that fluence (laser energy/spot area) has a significant influence on the amount of mass ablated and on the degree of fractionation. An optimal fluence was found at which the fractionation index approached unity; negligible fractionation. Infrared femtosecond laser ablation produced similar characteristics to UV nanosecond laser ablation.

Russo, Richard E.; Mao, Xianglei; Gonzalez, Jhanis J.; Mao,Samuel S.

2002-02-15

76

CO2 Laser Ablation Propulsion Tractor Beams  

NASA Astrophysics Data System (ADS)

Manipulation of objects at a distance has already been achieved with no small measure of success in the realm of microscopic objects on the scale size of nanometers to micrometers in applications including laser trapping and laser tweezers. However, there has been relatively little effort to apply such remote control to macroscopic systems. A space tractor beam could be applied to a wide range of applications, including removal of orbital debris, facilitation of spacecraft docking, adjustment of satellite attitude or orbital position, etc. In this paper, an ablative laser propulsion tractor beam is demonstrated based on radiation from a CO2 laser. Cooperative, layered polymer targets were used for remote impulse generation using a CO2 laser. The use of a structured ablatant enabling switching between thrust directional parity (i.e., forward or reverse) and imparting torque to a remote target. Fluence-dependent results are presented in the context of polymer ablation modeling work and with consideration of confined ablation effects.

Sinko, John E.; Schlecht, Clifford A.

2010-05-01

77

Laser ablation in analytical chemistry - A review  

SciTech Connect

Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

2001-10-10

78

Laser ablation of hymenal fissures.  

PubMed

Four patients presented with linear ulcers (hymenal fissures) that had not responded to conventional local therapy or oral antibiotics. These sexually active women had experienced dyspareunia for 8-24 months. Cultures for venereal agents were negative. One patient had two linear ulcers, and the others had only one; all the ulcers were restricted to the hymenal ring at either the 4 or 8 o'clock position. The lesions usually were obscured when the hymen was collapsed, but they were obvious when the ring was expanded. The lesions varied in length from 0.5 to 2 cm and were very shallow, generally 1 mm deep. The ulcers were linear streaks that could be stretched to 3-4 mm wide. Laser ablation of the lesions to a depth of at least 5 mm resulted in complete resolution of the ulcer in two cases. A third patient had almost complete resolution of the lesion after two laser treatments. The fourth patient failed treatment and refused additional treatment. The underlying nature of this recalcitrant condition may be as much an enigma as that of the anal fissure. Laser treatment seems the best approach at present. PMID:3950886

Michlewitz, H

1986-01-01

79

KrF-laser ablation of polyurethane  

Microsoft Academic Search

Polyurethane can be effectively and cleanly ablated with 248 nm excimer-laser radiation. For fluences above 200 mJ\\/cm2, very little post-ablation debris is observed — a fact indicative of a polymer that decomposes readily into volatile, small molecular-weight compounds. Ablation-rate data have been obtained both by stylus profilometry and the quartz-crystal microbalance (QCM) technique, and the results of both methods are

S. Küper; J. Brannon

1993-01-01

80

KrF laser ablation of polyurethane  

Microsoft Academic Search

248 nm excimer laser ablation of a polyurethane polymer is shown to proceed efficiently and with a surprising lack of post-ablation surface debris. The absorption spectrum of this material displays a strong increase in absorbance beginning at 260 nm and extending to shorter wavelengths, whereas a relatively weak absorption for longer wavelengths accounts for the inability of 308 nm excimer

Stephan Kueper; James H. Brannon

1991-01-01

81

Hydrodynamic simulations of metal ablation by femtosecond laser irradiation  

SciTech Connect

Ablation of Cu and Al targets has been performed with 170 fs laser pulses in the intensity range of 10{sup 12}-10{sup 14} W cm{sup -2}. We compare the measured removal depth with 1D hydrodynamic simulations. The electron-ion temperature decoupling is taken into account using the standard two-temperature model. The influence of the early heat transfer by electronic thermal conduction on hydrodynamic material expansion and mechanical behavior is investigated. A good agreement between experimental and numerical matter ablation rates shows the importance of including solid-to-vapor evolution of the metal in the current modeling of the laser matter interaction.

Colombier, J.P. [CEA/DAM Ile de France, Dept. de Physique Theorique et Appliquee, B.P. 12, 91680 Bruyeres-le-Chatel, (France); Laboratoire Traitement du Signal et Instrumentation (TSI), Universite Jean Monnet, UMR CNRS 5516, 42000 Saint-Etienne (France); Combis, P.; Bonneau, F. [CEA/DAM Ile de France, Dept. de Physique Theorique et Appliquee, B.P. 12, 91680 Bruyeres-le-Chatel (France); Le Harzic, R.; Audouard, E. [Laboratoire Traitement du Signal et Instrumentation (TSI), Universite Jean Monnet, UMR CNRS 5516, 42000 Saint-Etienne (France)

2005-04-15

82

Innovative Laser Ablation Technology for Surface Decontamination  

SciTech Connect

The objective of this project is to develop a novel laser ablation in liquid technology for surface decontamination. It aims to achieve more efficient surface decontamination without secondary contamination.

Chen, Winston C. H.

2002-06-01

83

Laser Ablation of Alumina in Water  

SciTech Connect

Bulk {alpha}-alumina immersed in distilled water was ablated by pulsed UV laser radiation. The resulting colloidal solution contained micron and submicron size particles. X-ray diffraction and Raman spectra of the ablated and original material are similar. Hence, most of the ablated material is {alpha}-alumina. From transmission electron microscope images, most of the submicron and all of the micron-sized particles have sharp edges and do not have spherical shapes, indicating that the dominant ablation mechanism is due to crack propagation. Some spherical particles of diameter less than 100 nm are observed, indicating that they were formed from the liquid state.

Musaev, O.; Midgley, A; Wrobel, J; Kruger, M

2010-01-01

84

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

A new laser ablation technique combined with a chemical evaporation reaction has been developed for elemental ratio analysis of solid samples using an inductively coupled plasma mass spectrometer (ICPMS). Using a chemically assisted laser ablation (CIA) technique developed in this study, analytical repeatability of the elemental ratio measurement was successively improved. To evaluate the reliability of the CLA-ICPMS technique, Pb/U isotopic ratios were determined for zircon samples that have previously been analyzed by other techniques. Conventional laser ablation for Pb/U shows a serious elemental fractionation during ablation mainly due to the large difference in elemental volatility between Pb and U. In the case of Pb/U ratio measurement, a Freon R-134a gas (1,1,1,2-tetrafluoroethane) was introduced into the laser cell as a fluorination reactant. The Freon gas introduced into the laser cell reacts with the ablated sample U, and refractory U compounds are converted to a volatile U fluoride compound (UF6) under the high-temperature condition at the ablation site. This avoids the redeposition of U around the ablation pits. Although not all the U is reacted with Freon, formation of volatile UF compounds improves the transmission efficiency of U. Typical precision of the 206Pb/238U ratio measurement is 3-5% (2sigma) for NIST SRM 610 and Nancy 91500 zircon standard, and the U-Pb age data obtained here show good agreement within analytical uncertainties with the previously reported values. Since the observed Pb/U ratio for solid samples is relatively insensitive to laser power and ablation time, optimization of ablation conditions or acquisition parameters no longer needs to be performed on a sample-to-sample basis. PMID:12553756

Hirata, Takafumi

2003-01-15

85

Laser ablation of solids for elemental analysis by inductively coupled plasma mass spectrometry  

Microsoft Academic Search

A technique for direct elemental analysis of solids is described. A focused Nd:YAG laser efficiently ablates many materials, including ceramics and polymers, that are difficult to prepare for solution analysis. Ablated particulate material is transported by gas flow into an inductively coupled plasma (ICP) and the resulting ions are detected by mass spectrometry. The laser may be used either in

Peter. Arrowsmith

1987-01-01

86

Nanosecond laser ablation of gold nanoparticle films  

SciTech Connect

Ablation of self-assembled monolayer protected gold nanoparticle films on polyimide was explored using a nanosecond laser. When the nanoparticle film was ablated and subsequently thermally sintered to a continuous film, the elevated rim structure by the expulsion of molten pool could be avoided and the ablation threshold fluence was reduced to a value at least ten times lower than the reported threshold for the gold film. This could be explained by the unusual properties of nanoparticle film such as low melting temperature, weak bonding between nanoparticles, efficient laser energy deposition, and reduced heat loss. Finally, submicron lines were demonstrated.

Ko, Seung H.; Choi, Yeonho; Hwang, David J.; Grigoropoulos, Costas P.; Chung, Jaewon; Poulikakos, Dimos [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Department of Mechanical Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich (Switzerland)

2006-10-02

87

Subpicosecond laser ablation of dental enamel  

NASA Astrophysics Data System (ADS)

Laser ablation of dental enamel with subpicosecond laser pulses has been studied over the intensity range of (0.1-1.4) x1014 W/cm2 using 95 and 150 fs pulses at a pulse repetition rate of 1 kHz. The experimentally determined ablation threshold of 2.2plus-or-minus0.1 J/cm2 was in good agreement with theoretical predictions based on an electrostatic ablation model. The ablation rate increased linearly with the laser fluence for up to 15 times the ablation threshold. The absence of collateral damage was observed using optical and scanning electron microscopy. Pulpal temperature measurements showed an increase of about 10 degC during the 200 s course of ablation. However, air cooling at a rate of 5 l/min resulted in the intrapulpal temperature being maintained below the pulpal damage threshhold of 5.5 degC. The material removal rates for subpicosecond precision laser ablation of dental enamel are compared with other techniques.

Rode, A. V.; Gamaly, E. G.; Luther-Davies, B.; Taylor, B. T.; Dawes, J.; Chan, A.; Lowe, R. M.; Hannaford, P.

2002-08-01

88

Analysis of infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

The mechanisms involved in infrared laser tissue ablation are studied using a free electron laser (FELIX) in order to clarify whether the increased ablation efficiency reported in literature for certain infrared wavelengths is due to a wavelength effect or to the specific pulse structure of the lasers that are generally used in these studies. Investigations are presented of ablation of vitreous from pigs" eyes using several techniques including protein gel electrophoresis and ablation plume visualization. The ablation effects of three different infrared wavelengths are compared: 3 mm, which is currently in clinical surgical use, and the wavelengths associated with the amide I and amide II bands, i.e. 6.2 mm and 6.45mm, respectively. The results suggest a different ablation mechanism to be in operation for each studied wavelength, thus indicating that the generally reported increased ablation efficiency in the 6-6.5 micron range is due to the wavelength rather than the typical free electron laser pulse structure.

McKenzie, Gordon P.; Timmerman, Brenda H.; Bryanston-Cross, Peter J.

2005-04-01

89

Ultrashort-pulse laser ablation of nanocrystalline aluminum  

SciTech Connect

Molecular-dynamics simulations of the ablation of nanocrystalline Al films by ultrashort laser pulses in the low-fluence (no-ionization) regime (0-2.5 times the ablation threshold, F{sub th}) are reported. The simulations employ an embedded-atom method potential for the dynamics of the ions and a realistic two-temperature model for the electron gas (and its interactions with the ion gas), which confers different electronic properties to the monocrystalline solid, nanocrystalline solid, and liquid regions of the targets. The ablation dynamics in three nanocrystalline structures is studied: two dense targets with different crystallite sizes (d=3.1 and 6.2 nm on average) and a d=6.2 nm porous sample. The results are compared to the ablation of monocrystalline Al. Significant differences are observed, the nanocrystalline targets showing, in particular, a lower ablation threshold and a larger melting depth, and yielding pressure waves of higher amplitude than the monocrystalline targets. Furthermore, it is shown that nanocrystalline targets experience no residual stress associated with thermal expansion and lateral constraints, and that little crystal growth occurs in the solid during and after ablation. Laser-induced spallation of the back surface of the films is also investigated; we find, in particular, that the high-strain fracture resistance of nanocrystalline samples is significantly reduced in comparison to the crystalline material.

Gill-Comeau, Maxime; Lewis, Laurent J. [Departement de Physique et Regroupement Quebecois sur les Materiaux de Pointe (RQMP), Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, Quebec, H3C 3J7 (Canada)

2011-12-01

90

Trace Element Microanalysis in Iron Meteorites by Laser Ablation ICPMS.  

PubMed

A laser ablation microanalysis system has been developed that can analyze trace elements with a sensitivity in the ppb range, using a CETAC LSX-200 laser ablation system with a Finnigan Element. This capability has been applied to a set of iron meteorites to demonstrate the laser microprobe's analytical capability for the determination of platinum group elements (PGEs) with a spatial resolution of ?20 ?m, comparable to that of dynamic secondary ion mass spectrometry (SIMS). The laser is shown to provide an accurate means of solid sampling for magnetic sector inductively coupled plasma mass spectrometry (ICPMS), allowing the determination of bulk metal composition, chemical zoning within the sample, and depth profiling. Recovery of the chemical zoning in taenite lamellae was achieved for Ru, Rh, and Pd, which was not previously possible using SIMS. The methods presented here show that magnetic sector ICPMS can be successfully coupled to a laser ablation system, providing the advantages of higher sensitivity of the sector instrument, low background count rates (<0.1 counts/s), and flat-topped spectral peaks, while minimizing tradeoff against the speed of data acquisition required to handle the transient signals from the laser ablation system. PMID:21662764

Campbell, A J; Humayun, M

1999-03-01

91

Optical modeling of laser ablated microstructures  

NASA Astrophysics Data System (ADS)

From only an a priori knowledge of the optical parameters of a laser beam, the delivery system together with a substrate's material properties, a ray-tracing model capable of predicting the 3-D topology of micro/nanostructures machined by pulsed laser ablation has been developed. The model includes secondary illumination effects produced by the microstructure created by successive pulses (wall reflections, refraction, wave guiding, shadowing, etc.) as well as the complete optical properties of the beam delivery system. We have used material ablation by pulsed excimer lasers and associated beam delivery systems to demonstrate some of the capabilities of the model. Good agreement is obtained between computations and experimental results in terms of the predicted ablation depth per pulse and the wall taper angle of channels and holes. The model can predict ablated profiles of holes and indicate the most efficient drilling strategy in terms of material removal rates. The model also shows diffraction effects are not required to explain the tapering vertical walls observed when ablating microstructures. Finally, the model has been used to demonstrate aberrations in an optical imaging system limiting the creation of submicron features in an ablated microstructure. Provided photons are absorbed linearly in a substrate according to Beer's law with negligible thermal diffusion effects, the model is equally applicable to using other types of pulsed laser sources and systems with imaged or focused beams.

Gower, M. C.; Davies, E.; Holmes, A. S.

2012-11-01

92

Experimental investigation of ablation efficiency and plasma expansion during femtosecond and nanosecond laser ablation of silicon  

Microsoft Academic Search

Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) 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 deeper than the

X. Zeng; X. L. Mao; R. Greif; R. E. Russo

2005-01-01

93

Experimental investigation of ablation efficiency and plasma expansion during femtosecond and nanosecond laser ablation of silicon  

Microsoft Academic Search

Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) 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 deeper than the ns-crater. The temperature

X. Zeng; X. L. Mao; R. Greif; R. E. Russo

2005-01-01

94

Nanosecond laser ablation of silver nanoparticle film  

NASA Astrophysics Data System (ADS)

Nanosecond laser ablation of polyvinylpyrrolidone (PVP) protected silver nanoparticle (20 nm diameter) film is studied using a frequency doubled Nd:YAG nanosecond laser (532 nm wavelength, 6 ns full width half maximum pulse width). In the sintered silver nanoparticle film, absorbed light energy conducts well through the sintered porous structure, resulting in ablation craters of a porous dome shape or crown shape depending on the irradiation fluence due to the sudden vaporization of the PVP. In the unsintered silver nanoparticle film, the ablation crater with a clean edge profile is formed and many coalesced nanoparticles of 50 to 100 nm in size are observed inside the ablation crater. These results and an order of magnitude analysis indicate that the absorbed thermal energy is confined within the nanoparticles, causing melting of nanoparticles and their coalescence to larger agglomerates, which are removed following melting and subsequent partial vaporization.

Chung, Jaewon; Han, Sewoon; Lee, Daeho; Ahn, Sanghoon; Grigoropoulos, Costas P.; Moon, Jooho; Ko, Seung H.

2013-02-01

95

Rapid tooling using controlled laser ablation  

NASA Astrophysics Data System (ADS)

Laser based rapid tooling techniques enable the completion of tools within a minimized period of time. Especially the controlled laser ablation process of metals or ceramics allows precise manufacturing along with a high surface accuracy of the parts. The reactive ablation mechanism of ferrous materials in oxygen atmosphere -- the chip removal - is described, as well as the optimization of the process parameters by systematical procedures. The processing results are limited with given radius of the interaction zone between the laser beam and the workpiece surface. Essential process-parameter is therefore the focus radius. This parameter, effectively being controlled by an adaptive optical mirror, strongly influences the process and thus the workpiece result. The laser ablation process characteristically offers a high flexibility concerning workpiece materials and geometries. In combination with the ability of processing even hardened steels without any tool wear laser ablation is predestined for the rapid tooling of metal forming tools like hot forging dies. Obtaining high workpiece accuracy along with short manufacturing times recommends the optimized ablation process not only for prototyping but for serial manufacturing as well.

Geiger, Manfred; Schubart, Doris; Kauf, Michael

1996-08-01

96

UV laser ablation patterns in intraocular lenses  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate the effect of UV solid state laser radiation on intraocular lens (IOL) polymer surfaces as an alternative method to conventional surface shaping techniques for IOLs customization. Laser ablation experiments were performed on PMMA plates and commercially available hydrophobic and hydrophilic acrylic IOLs with the 5th harmonic of a Q-switched Nd:YAG laser (?=213 nm). Circular arrays of holes were drilled on the polymer surface, covering the centre and the peripheries of the IOL. The morphology of the ablated IOL surface was examined with a conventional optical microscope (Leitz GMBH Wetzlar) and with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements of ablation rates were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variationsF in surface height. Laser interaction with IOLs depends on optical and mechanical material properties, in addition to laser radiation parameters. The exact ablation mechanism is discussed. Some polymer materials, depending on their properties, are more susceptible to the photothermal mechanism than the photochemical one or vice versa. In summary, every IOL polymer exhibits specific attributes in its interaction with the 5th harmonic of Nd:YAG laser.

Lagiou, D. P.; Evangelatos, Ch.; Apostolopoulos, A.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

2013-03-01

97

Resonant laser ablation: mechanisms and applications  

SciTech Connect

We report on aspects of resonant laser ablation (RLA) behavior for a number of sample types: metals, alloys, thin films, zeolites and soil. The versatility of RLA is demonstrated, with results on a variety of samples and in several mass spectrometers. In addition, the application to depth profiling of thin films is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation is presented.

Anderson, J.E. [Los Alamos National Lab., NM (United States); Allen, T.M. [California Univ., Davis, CA (United States). Dept. of Chemistry; Garrett, A.W.; Gill, C.G.; Hemberger, P.H. [Los Alamos National Lab., NM (United States); Kelly, P.B. [California Univ., Davis, CA (United States). Dept. of Chemistry; Nogar, N.S. [Los Alamos National Lab., NM (United States)

1996-10-01

98

Infrared Laser Ablation Sample Transfer for MALDI and Electrospray  

NASA Astrophysics Data System (ADS)

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 (OPO) laser system at 2.94 ?m wavelength and approximately 1 mJ pulse energy was focused onto samples for ablation at atmospheric pressure. The ablated material was captured in a solvent droplet 1-2 mm in diameter that was suspended from a silica capillary a few millimeters above the sample target. Once the sample was transferred to the droplet by ablation, the droplet was deposited on a MALDI target. A saturated matrix solution was added to the deposited sample, or in some cases, the suspended capture droplet contained the matrix. Peptide and protein standards were used to assess the effects of the number of IR laser ablation shots, sample to droplet distance, capture droplet size, droplet solvent, and laser pulse energy. Droplet collected samples were also injected into a nanoelectrospray source of an ion trap mass spectrometer with a 500 nL injection loop. It is estimated that pmol quantities of material were transferred to the droplet with an efficiency of approximately 1%. The direct analysis of biological fluids for off-line MALDI and electrospray was demonstrated with blood, milk, and egg. The implications of this IR ablation sample transfer approach for ambient imaging are discussed.

Park, Sung-Gun; Murray, Kermit King

2011-08-01

99

Sympathetic cooling of laser-produced doubly charged ions in a few-ion crystal  

Microsoft Academic Search

We present experimental results in which single Ca{sup +} ions in a chain of laser cooled Ca{sup +} ions are further ionized by means of an intense short pulse laser. The ions are trapped in a linear Paul trap, which is instantaneously loaded by ions from a laser-produced ablation plasma. Due to sympathetic cooling the doubly charged ions are held

T. Kwapien; U. Eichmann; W. Sandner

2007-01-01

100

Sympathetic cooling of laser-produced doubly charged ions in a few-ion crystal  

Microsoft Academic Search

We present experimental results in which single Ca+ ions in a chain of laser cooled Ca+ ions are further ionized by means of an intense short pulse laser. The ions are trapped in a linear Paul trap, which is instantaneously loaded by ions from a laser-produced ablation plasma. Due to sympathetic cooling the doubly charged ions are held in place.

T. Kwapien; U. Eichmann; W. Sandner

2007-01-01

101

Tumour ablation by laser in general surgery  

Microsoft Academic Search

Conclusions More surgeons are becoming interested in laser surgery, but, in laser tumour ablation the real improvement in open surgery can only be provided by:1.The use of the right parameters and lasers in every discipline. The recent outcome of combined CO2 and Nd-YAG delivery in the same beam (Combolaser, Lasermatic OY), and the velocity to obtain a suitable blend of

R. A. Sultan

1990-01-01

102

Ultrashort Pulse Laser Ablation for Depth Profiling of Bacterial Biofilms  

PubMed Central

Sample ablation by pulsed lasers is one option for removing material from a sample surface for in situ depth profiling during imaging mass spectrometry, but ablation is often limited by laser-induced damage of the remaining material. A preliminary evaluation was performed of sub-100 fs, 800 nm pulsed laser ablation for depth profiling of bacterial biofilms grown on glass by the drip flow method. Electron and optical microscopy were combined with laser desorption vacuum ultraviolet postionization mass spectrometry to analyze biofilms before and after ablation. Ultrashort laser pulses can ablate 10 – 100 µm thick sections of bacterial biofilms, leaving behind a layer of lysed cells. However, mass spectra from intact and ablated biofilms doped with antibiotic are almost identical, indicating little chemical degradation by ablation. These results are consistent with prior observations from laser surgery and support the use of ultrashort pulse laser ablation for minimally disruptive depth profiling of bacterial biofilms and intact biological samples.

Milasinovic, Slobodan; Liu, Yaoming; Gasper, Gerald L.; Zhao, Youbo; Johnston, Joanna L.; Gordon, Robert J.; Hanley, Luke

2010-01-01

103

Dynamics of Laser-Driven Ablatively Accelerated Targets.  

NASA Astrophysics Data System (ADS)

The characteristics of ablation plasma from planar targets, driven by long Nd: glass laser pulses (4 nsec, < 10('14) W/cm('2)), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic pendula have been tested and calibrated in the experimental environment. A novel double-foil technique has been developed and used to study the velocity of the accelerated target. Using measurements of plasma energy, velocity, and momentum, we determine the scaling with irradiance and the absolute magnitudes of the ablation pressure, velocity and ablation depth (or mass ablation rate). These results are insensitive to laser spot-size effects that may introduce error under some experimental conditions. They imply that the hydrodynamic efficiency and initial thickness of targets acclerated to fusion velocities are weak and strong functions of absorbed irradiance respectively. Thus, target thickness and irradiance may be varied as necessary to alter the pellet-aspect-ratio or to increase laser nonuniformity smoothing with only small changes in hydrodynamic efficiency. We have determined that the accelerated target is composed of a high pressure, high density region preceeded by a low pressure, low desnity plasma. We have measured the velocity of the high density region and found that it agrees with target velocities predicted from the ablation parameters using a simple rocket model. We accelerated targets over a distances many times their own thickness to velocities of 100 km/sec with no apparent breakup. These dense target velocities are close to the implosion velocities required of hollow fusion-pellet shells.

Grun, Jacob

104

Dynamics of laser driven, ablatively accelerated targets. Memorandum report  

SciTech Connect

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, < 10 to the 14th power w/sq cm), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic pendula have been tested and calibrated in the experimental environment. A novel double-foil technique has been developed and used to study the velocity of the accelerated target. Using measurements of plasma energy, velocity, and momentum, we determined the scaling with irradiance and the absolute magnitudes of the ablation pressure, velocity and ablation depth (or mass ablation rate). These results are insensitive to laser spot-size effects that may introduce error under some experimental conditions. They imply that the hydrodynamic efficiency and initial thickness of targets accelerated to fusion velocities are weak and strong functions of absorbed irradiance respectively. Thus, target thickness and irradiance may be varied as necessary to alter the pellet-aspect-ratio or to increase laser nonuniformity smoothing with only small changes in hydrodynamic efficiency. We have determined that the accelerated target is composed of a high pressure, high density region preceeded by a low pressure, low density plasma. We have measured the velocity of the high density region and found that it agrees with target velocities predicted from the ablation parameters using a simple rocket model. We accelerated targets over distances many times their own thickness to velocities of 100 km/sec with no apparent breakup.

Grun, J.

1981-05-08

105

Dynamics of laser ablation plume penetration through low pressure background gases  

Microsoft Academic Search

The dynamics of laser-ablated yttrium plume propagation through background argon have been investigated with fast time- and spatially-resolved plasma diagnostics in order to characterize a general phenomenon believed to be important to film growth by pulsed laser deposition (PLD). During expansion into low-pressure background gases, the ion flux in the laser ablation plasma plume is observed to split into fast

David B. Geohegan; Alexander A. Puretzky

1995-01-01

106

Influence of optical absorption on urinary calculus threshold fluence and ablation efficiency during infrared laser ablation  

NASA Astrophysics Data System (ADS)

The objectives of this study were to determine if the optical absorption properties of urinary calculi affect the threshold fluence for ablation or fragmentation and the ablation efficiency due to laser irradiation. The Vanderbilt free electron laser was tuned to selected wavelengths based on the absorption spectrum of various types of urinary calculi. The threshold fluences for ablation of the calculi were measured at different wavelengths. A preliminary study of the ablation efficiency (ablation depth per unit incidence fluence) was performed. The results were fond to be in agreement with a thermal ablation model for which the threshold fluences were proportional to l/(mu) a. The ablation efficiencies were higher in regions of the infrared spectra in which absorption was higher. For a fixed laser irradiation, the lower threshold fluences within regions of high optical absorption allowed more energy to enhance calculus ablation. This study provided insight into determining the optimum wavelengths for ablation and laser lithotripsy.

Chan, Kin Foong; Hammer, Daniel X.; Choi, Bernard; Vargas, Gracie; Sorg, Brian S.; Pfefer, Thomas Joshua; Teichman, Joel M.; McGuff, H. Stan; Pratisto, Hans S.; Jansen, E. Duco; Welch, Ashley J.

2000-04-01

107

Laser Ablation for Small Hepatocellular Carcinoma  

PubMed Central

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is increasingly detected at small size (<5?cm) owing to surveillance programmes in high-risk patients. For these cases, curative therapies such as resection, liver transplantation, or percutaneous ablation have been proposed. When surgical options are precluded, image-guided tumor ablation is recommended as the most appropriate therapeutic choice in terms of tumor local control, safety, and improvement in survival. Laser ablation (LA) represents one of currently available loco-ablative techniques: light is delivered via flexible quartz fibers of diameter from 300 to 600??m inserted into tumor lesion through either fine needles (21g Chiba needles) or large-bore catheters. The thermal destruction of tissue is achieved through conversion of absorbed light (usually infrared) into heat. A range of different imaging modalities have been used to guide percutaneous laser ablation, but ultrasound and magnetic resonance imaging are most widely employed, according to local experience and resource availability. Available clinical data suggest that LA is highly effective in terms of tumoricidal capability with an excellent safety profile; the best results in terms of long-term survival are obtained in early HCC so that LA can be proposed not only in unresectable cases but, not differently from radiofrequency ablation, also as the first-line treatment.

Pacella, Claudio Maurizio; Francica, Giampiero; Di Costanzo, Giovanni Giuseppe

2011-01-01

108

Femtosecond laser ablation of bovine cortical bone  

NASA Astrophysics Data System (ADS)

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

Cangueiro, Liliana T.; Vilar, Rui; Botelho do Rego, Ana M.; Muralha, Vania S. F.

2012-12-01

109

KrF-laser ablation of polyurethane  

NASA Astrophysics Data System (ADS)

Polyurethane can be effectively and cleanly ablated with 248 nm excimer-laser radiation. For fluences above 200 mJ/cm2, very little post-ablation debris is observed — a fact indicative of a polymer that decomposes readily into volatile, small molecular-weight compounds. Ablation-rate data have been obtained both by stylus profilometry and the quartz-crystal microbalance (QCM) technique, and the results of both methods are in good agreement. The more sensitive QCM technique first detects material removal near 20 mJ/cm2, which is likely due to outgassing, surface chemistry, or low quantum-yield processes. At 37 mJ/cm2, an ablation “threshold” with a sharp increase of the ablation rate is observed and marks the onset of efficient, explosive ablation. The densely sampled rate curve provided by the QCM permits the conclusion that an Arrhenius-like exponential does not give a satisfactory fit to the data. This demonstrates that the ablation process is not solely governed by thermal processes. Applying a Beer's-law analysis of rate versus the natural logarithm of the fluence yields excellent agreement with the data up to 300 mJ/cm2. The absorption coefficent derived from this analysis agrees well (within 4%) with the value obtained from the low-intensity absorption spectrum.

Küper, S.; Brannon, J.

1993-09-01

110

F2 laser ablation of silicone rubber  

NASA Astrophysics Data System (ADS)

The ablation of silicone rubber (polydimethysiloxane, [SiO(CH3)2]n) by 157-nm F2 laser irradiation has been studied. The ablation threshold fluence (Fth) was approximately 140 mJ/cm2. The irradiated surface swelled and was modified to SiO2 for laser fluences below Fth. No carbon contamination was observed in the SiO2. Above Fth, the surface of etched silicone rubber was structurally well defined and precisely patterned. The chemical composition of the etched surface demonstrated little change. When the silicone rubber was irradiated at laser fluences of nearly Fth, conical structures were formed on the surface. It is supposed that residual carbon photodissociated by laser irradiation initiated cone formation by locally shifting Fth to a higher value. In situ mass spectrometric analysis of gaseous products evolved during F2 laser irradiation of silicone rubber showed that CH3 and CH4 components dominated for laser fluences below Fth, and CO component dominated for laser fluences above Fth. The high photon energy (7.9 eV) of an F2 laser could photodissociate preferentially weak bonds (Si-C) of silicone for lower laser fluence and almost all bonds (Si-C, C-H, Si-O) of silicone for higher laser fluence.

Takao, Hiromitsu; Okoshi, Masayuki; Inoue, Narumi

2004-10-01

111

Innovative Laser Ablation Technology for Surface Decontamination  

SciTech Connect

The objective of this project is to develop a novel laser ablation in liquid for surface decontamination. It aims to achieve more efficient surface decontamination without secondary contamination. Another aim is to make this surface decontamination technology becomes economically feasible for large scale decontamination.

Chen, Winston C. H.

2003-06-01

112

Pulsed holmium laser ablation of cardiac valves  

Microsoft Academic Search

Ablation efficiency and residual thermal damage produced by pulsed holmium laser radiation were investigated in vitro for bovine mitral valves and human calcified and noncalcified cardiac valves. Low-OH quartz fibers (200 and 600 microns core diameter) were used in direct contact perpendicular to the specimen under saline or blood. Etch rate was measured with a linear motion transducer. Radiant exposure

Lothar Lilge; Wolfgang Radtke; Norman S. Nishioka

1989-01-01

113

Free electron laser ablation of urinary calculi: an experimental study  

Microsoft Academic Search

Infrared laser ablation of urinary calculi was investigated as a function of wavelength to determine the relation of ablation threshold fluences, ablation depths, and optical absorption. A simple photothermal ablation model was employed to examine this relationship. Human urinary calculi composed of >95% uric acid, >95% cystine, >95% calcium oxalate monohydrate (COM), and >90% magnesium ammonium phosphate hexahydrate (MAPH) were

Kin Foong Chan; Bernard Choi; Gracie Vargas; Daniel X. Hammer; Brian Sorg; T. Joshua Pfefer; Joel M. H. Teichman; Ashley J. Welch; E. Duco Jansen

2001-01-01

114

Infrared laser ablation atmospheric pressure photoionization mass spectrometry.  

PubMed

In this paper we introduce laser ablation atmospheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 ?m wavelength. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ~300 ?m lateral resolution comparable to, e.g., matrix-assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves. PMID:22242626

Vaikkinen, Anu; Shrestha, Bindesh; Kauppila, Tiina J; Vertes, Akos; Kostiainen, Risto

2012-01-19

115

Double-pulse laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

This paper describes the use of double-pulse laser ablation to improve ICP-MS internal (temporal relative standard deviation, %TRSD) and external (%RSD) precision. The first laser pulse is used to ablate a large quantity of mass from the sample surface. The second pulse is applied with a variable time delay after the first pulse to break the ablated mass into a

Jhanis González; Chunyi Liu; Jong Yoo; Xianglei Mao; Richard E. Russo

2005-01-01

116

Investigations of Basic Ablation Phenomena During Laser Thrombolysis  

Microsoft Academic Search

This paper presents studies of microsecond ablation phenomena that take place during during laser thrombolysis. The main goals were to optimize laser parameters for e-cient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate

Ujwal S. Sathyam; Alan Shearin; Scott A. Prahl

117

Surface Characterization of Laser-Ablated Polymers Used for Microfluidics  

Microsoft Academic Search

Fabrication of microfluidic devices by excimer laser ablation under different atmospheres may provide varia- tions in polymer microchannel surface characteristics. The surface chemistry and electroosmotic (EO) mobility of polymer microchannels laser ablated under different atmospheres were studied by X-ray photoelectron spec- troscopy and current monitoring mobility measurements, respectively. The ablated surfaces of PMMA were very similar to the native material,

D. L. Pugmire; E. A. Waddell; R. Haasch; M. J. Tarlov; L. E. Locascio

2002-01-01

118

Desorption spectra of laser ablation of Tl-Ca-Ba-Cu-O superconductors  

SciTech Connect

Quantitative measurements of desorbed ions and neutral molecules by a quadruple mass spectrometer from laser ablation of Tl-Ca-Ba-Cu-O were obtained. The results indicate that more neutral atoms and molecules desorbed than the corresponding ions. More elementary ions desorbed than the corresponding oxide compounds.

Chen, C.H.; Phillips, R.C.; McCann, M.P. (Chemical Physics Section, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6378 (United States))

1993-01-15

119

Modeling CO{sub 2} Laser Ablative Impulse with Polymers  

SciTech Connect

Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO{sub 2} laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO{sub 2} laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

Sinko, John E. [Micro-Nano Global Center of Excellence (GCOE), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan 464-8603 (Japan); Phipps, Claude R. [Photonic Associates, LLC, 200A Ojo de la Vaca Rd., Santa Fe, NM 87508 (United States); Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan, 464-8603 (Japan)

2010-10-08

120

Custom-contoured ablation pattern method for the treatment of decentered laser ablations  

Microsoft Academic Search

Purpose: To evaluate the custom-contoured ablation pattern (C-CAP) method as a tool for providing customized laser ablations for decentered ablations based on corneal topography data.Setting: Department of Ophthalmology, Stanford University, Stanford, California, USA.Methods: In a prospective noncomparative interventional case series, 8 eyes from 7 post-laser in situ keratomileusis (LASIK) patients and 1 post-photorefractive keratectomy (PRK) patient with symptomatic laser decentration

Danny Y Lin; Edward E Manche

2004-01-01

121

KrF laser ablation of polyurethane  

NASA Astrophysics Data System (ADS)

248 nm excimer laser ablation of a polyurethane polymer is shown to proceed efficiently and with a surprising lack of post-ablation surface debris. The absorption spectrum of this material displays a strong increase in absorbance beginning at 260 nm and extending to shorter wavelengths, whereas a relatively weak absorption for longer wavelengths accounts for the inability of 308 nm excimer radiation to cause efficient ablation. Ablation rate versus incident fluence data were obtained by both conventional stylus profilometry and the higher precision quartz-crystal microbalance (QCM) method. The data from both methods were in agreement, although the QCM technique provided far more detail of the threshold region. Interestingly, near 35 mJ/cm2 incident fluence, a pronounced increase in the slope of the rate versus fluence curve appears. This is suggestive of a mechanistic change from a lower to higher efficiency ablation regime. Applying a conventional Beer's Law analysis of rate versus In(fluence) yields a straight line that agrees well with the data up to 300 mJ/cm2. In face, the absorption coefficient derived from the slope of this curve is within 4% of the experimentally determined low-level value.

Kueper, Stephan; Brannon, James H.

1991-12-01

122

Fabrication of freestanding LiNbO{sub 3} thin films via He implantation and femtosecond laser ablation  

SciTech Connect

The authors report using a combination of ion-implantation exfoliation and femtosecond laser ablation to fabricate thin (micrometers-thick) single-crystal films of a complex oxide, LiNbO{sub 3}. The process physics for the method is bounded by the threshold for ablation and the onset of laser thermal outdiffusion of the implanted He used in exfoliation selective etching.

Gaathon, Ophir; Ofan, Avishai; Dadap, Jerry I.; Vanamurthy, Lakshmanan; Bakhru, Sasha; Bakhru, Hassaram; Osgood, Richard M. Jr. [Microelectronic Sciences Laboratory, Columbia University, New York, New York 10027 (United States); College of Nanoscale Science and Engineering, State University of New York at Albany, Albany, New York 12203 (United States); Microelectronic Sciences Laboratory, Columbia University, New York, New York 10027 (United States)

2010-05-15

123

Inertial effects in laser-driven ablation  

SciTech Connect

The gasdynamic partial differential equations (PDE's) governing the motion of an ablatively accelerated target (rocket) contain an inertial force term that arises mathematically from acceleration of the reference frame in which the PDE's are written, and more physically from the requirement that part of the ablated mass (the deflagration wave zone) needs to be accelerated along with the unablated mass (payload). We give a simple, intuitive description of this effect, and estimate its magnitude and parametric dependences by means of approximate analytical formulas inferred from our computer hydrocode calculations. Often this inertial term is negligible, but for problems in the areas of laser fusion and laser equation of state studies we find that it can reduce the attainable hydrodynamic efficiency of acceleration and implosion by up to 25% for typical conditions.

Harrach, R. J.; Szoeke, A.; Howard, W. M.

1983-08-18

124

Laser ablation of multilayer polymer films  

SciTech Connect

We study the efficiency of using multilayer structures as an etch-stop mechanism in the ablation of polyimide films by ultraviolet lasers. The study is done using a photothermal model that includes the light absorption by the decomposed fragments, which shield the polymer from the laser beam, an intermediate zone in which the polymer is suffering a phase transition and the underlying unburned material. The layers are differentiated from each other through their optical properties. Variation in the optical properties of polyimide has been achieved by a proper selection of impurities. From our modeling work, we conclude that optically thin foils may be used as etch stop in the ablation process when the penetration depth of the middle layer is around three times larger than the penetration depth of the surrounding layers, this for fluences below 200 mJ/cm[sup 2]. We also present some experimental results.

Reyna, L.G. (T. J. Watson Research Center, IBM Research Division, Yorktown Heights, New York 10598 (United States)); Sobehart, J.R. (Center For Nonlinear Studies (B258), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1994-10-01

125

Pressure impulses during microsecond laser ablation.  

PubMed

The collapse of laser-induced cavitation bubbles creates acoustic transients within the surrounding medium and also pressure impulses to the ablation target and light-delivery fiber during microsecond laser ablation. The impulses are investigated here with time-resolved flash photography, and they are found to occur whether or not the light-delivery fiber is in contact with the target. We demonstrate that the impulses depend primarily on the energy stored in the cavitation bubble. They are not directly dependent on the mode of light delivery (contact versus noncontact), and they are also not directly correlated to the other acoustic transients. The pressure impulses do seem to be associated with the bubble-driven jet formation caused by the bubble collapse. PMID:18264462

Shangguan, H; Casperson, L W; Prahl, S A

1997-12-01

126

Magnetic Colloids By Pulsed Laser Ablation  

NASA Astrophysics Data System (ADS)

Colloidal magnetic nanoparticles have been successfully synthesized by nano second pules laser ablation of a cobalt slice immersed in liquid (distilled water) medium. The focused output of 1064 nm wavelength of pulsed Nd: YAG laser operating at 40 mJ/pulse is used for ablation. The liquid enviorment allows formation of colloids with nanoparticles in uniform particle diameter. Synchrotron X-ray powder diffraction (XRD) is used for the study of structural property of synthesized nanoparticles. The magnetic properties of cobalt nanoparticles are also investigated. The coercivity of is found to be 73 Oe. The optical properties have been determined by UV-visible absorption spectroscopy and band gap found to be 2.16 and 3.60 eV.

Pandey, B. K.; Singh, M. K.; Agarwal, A.; Gopal, R.

2011-06-01

127

Laser ablation studies using RIS  

SciTech Connect

Here we describe a Resonance Ionization Mass Spectroscopy system which includes a Nd:YAG laser microprobe, multiphoton resonance ionization, a time-of-flight mass spectrometer, and a novel data acquisition system. With this system we have measured the relative population of thermally populated energy levels and the velocity distribution of samarium atoms vaporized by the laser microprobe to determine the excitation and kinetic temperatures, respectively.

Beekman, D.W.; Callcott, T.A.

1984-01-01

128

In Situ UPb Zircon Dating Using Laser Ablation-Multi Ion Counting-ICP-MS (LA-MIC-ICP-MS)  

Microsoft Academic Search

In-situ analysis of zircons The systematics of U and Pb in zircons serve as one of the most important dating tools available in the geosciences. Until now, most zircon analyses are performed by second- ary ion mass spectrometry (SIMS) or thermal ionization mass spectrometry (TIMS). SIMS offers the possibility of in-situ analysis of single crystals at high spatial resolution. TIMS

Finnigan NEPTUNE

129

Reactive laser ablation deposition of CN films  

Microsoft Academic Search

We report a study of the characteristics of thin films deposited at room temperature on Si and KBr substrates by XeCl laser ablation of graphite in low pressure (0.25-2.5 mbar) nitrogen and ammonia atmospheres. Very hard films, with a very high electrical resistivity were obtained. The deposition rates decrease with increasing ambient pressure. N\\/C atomic ratios up to 0.6 were

Gilberto Leggieri; Armando Luches; A. Perrone; S. Acquaviva; Rodica Alexandrescu; Ion N. Mihailescu; Joseph Zemek; Paolo Mengucci

1996-01-01

130

Investigating Age Resolution in Laser Ablation Geochronology  

NASA Astrophysics Data System (ADS)

Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; Vancouver, British Columbia, Canada, 12-13 July 2008; Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) uranium-thorium-lead (U-Th-Pb) dating is an increasingly popular approach for determining the age of mineral grains and the timing of geological events. The spatial resolution offered by this technique allows detailed investigations of complex igneous and metamorphic processes, and the speed of data capture allows vast amounts of information to be gathered rapidly. Laser ablation U-Th-Pb dating is therefore becoming an increasingly influential technique to the geochronology community, providing cost-effective and ready access to age data for laboratories and end users worldwide. However, complications in acquiring, processing, and interpreting data can lead to inaccurate age information entering the literature. With the numbers of practitioners expanding rapidly, the need to standardize approaches and resolve difficulties (particularly involving the subjectivity in processing laser ablation U-Th-Pb data) is becoming important.

Horstwood, Matt; Kosler, Jan; Jackson, Simon; Pearson, Norman; Sylvester, Paul

2009-02-01

131

Inertial effects in laser-drive ablation  

NASA Astrophysics Data System (ADS)

The gas dynamic partial differential equations (PDE's) which govern the motion of an ablatively accelerated target (rocket) contain an inertial force term that arises from acceleration of the reference frame in which the PDE's are written are described. The effect and its magnitude and parametric dependences are estimated by approximate analytical formulas inferred from computer hydrocode calculations. It is found that often this inertial term is negligible but for problems in the areas of laser fusion and laser equation of state studies. It is found that it can substantially reduce the attainable hydrodynamic efficiency of acceleration and implosion.

Harrach, R. J.; Szoeke, A.; Howard, W. M.

1983-07-01

132

Inertial effects in laser-driven ablation  

SciTech Connect

The gasdynamic partial differential equations (PDE's) governing the motion of an ablatively accelerated target (rocket) contain an inertial force term that arises from acceleration of the reference frame in which the PDE's are written. We give a simple, intuitive description of this effect, and estimate its magnitude and parametric dependences by means of approximate analytical formulas inferred from our computer hydrocode calculations. Often this inertial term is negligible, but for problems in the areas of laser fusion and laser equation of state studies we find that it can substantially reduce the attainable hydrodynamic efficiency of acceleration and implosion.

Harrach, R.J.; Szeoke, A.; Howard, W.M.

1983-07-15

133

Influence of nonuniform laser intensities on ablatively accelerated targets  

Microsoft Academic Search

The effect of a nonuniform laser beam on the ablative acceleration of thin foils is investigated by using the FAST2D laser-shell simulation code. The results show that laser nonuniformities with scale lengths greater than the distance from the ablation surface to the critical surface would have a severe impact on drive pressure symmetry and hence on pellet gain.

Mark Emery; Joseph Orens; John Gardner; Jay Boris

1982-01-01

134

Measurement of Er:YAG laser ablation plume dynamics  

Microsoft Academic Search

The dynamics of tissue ablation using an Er:YAG laser were studied using flash photography and optical pump-probe techniques. Both normal-spiking-mode and Q-switched Er:YAG laser radiation were used to study the ablation of skin and bone. Time-resolved photographs of the ablation plume were obtained using a microscope-mounted camera together with pulsed illumination from an excimer-pumped dye laser. The velocity of the

J. T. Walsh; T. F. Deutsch

1991-01-01

135

Influence of the ablation threshold fluence on laser-driven acceleration  

NASA Astrophysics Data System (ADS)

Laser ablation threshold measurements has been carried out by the nanosecond-class Nd:YAG laser at LNS-INFN in Catania. Advanced targets, such as hydrogen-enriched silicon slabs and sub-micro structured polymeric samples, have been investigated. The estimated ablation fluences are correlated to recent experimental and theoretical results on high intensity laser driven ion acceleration. Characteristics of H-atoms/protons and heavier atoms/ions coming out from the bulk of the irradiated target or from surface contaminants have been determined by optical and time-of-flight spectroscopy as well as mass quadrupole spectrometry.

Margarone, D.; Velyhan, A.; Torrisi, L.; Cutroneo, M.; Giuffrida, L.; Picciotto, A.; Krasa, J.; Cavallaro, S.; Limpouch, J.; Klimo, O.; Psikal, J.; Proska, J.; Novotny, F.

2013-05-01

136

Spectroscopic characterization of laser ablation brass plasma  

SciTech Connect

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 number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated.

Shaikh, Nek M. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Institute of Physics, University of Sindh, 76080 Jamshoro (Pakistan); Hafeez, Sarwat; Kalyar, M. A.; Ali, R.; Baig, M. A. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan)

2008-11-15

137

Nanosecond laser ablation for pulsed laser deposition of yttria  

NASA Astrophysics Data System (ADS)

A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

Sinha, Sucharita

2013-09-01

138

Nanosecond laser ablation for pulsed laser deposition of yttria  

NASA Astrophysics Data System (ADS)

A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

Sinha, Sucharita

2013-04-01

139

Dense strongly coupled plasma in double laser pulse ablation of lithium: Experiment and simulation  

NASA Astrophysics Data System (ADS)

In a simple method of low power nano-second double pulsed laser ablation experiment in collinear geometry, formation of high density strongly coupled plasma is demonstrated. Using time-resolved measurements of the Stark broadened line width and line intensity ratio of the emission lines, the density and temperature of the plasma were estimated respectively. In this experiment, it is shown that ions are strongly coupled (ion-ion coupling parameter comes out to be >4). For comparison, both single and double pulsed laser ablations are presented. For the estimated experimental plasma parameters, first principle Langevin dynamics simulation corroborates the existence of a strongly coupled regime.

Kumar, Ajai; Sivakumaran, V.; Ashwin, J.; Ganesh, R.; Joshi, H. C.

2013-08-01

140

F2 excimer laser (157 nm) ablation of polymers: relation of neutral and ionic fragment detection and absorption  

NASA Astrophysics Data System (ADS)

The ablation products of various polymers (triazene polymers, polyimides and glycidyl azide polymer) with 157 nm F2 laser irradiation were studied with time-of-flight mass spectroscopy, ion probe and white-light interferometry. In contrast to the ablation with longer UV wavelengths, 157 nm irradiation results in non-preferential bond-breaking and a much more pronounced fragmentation into fragments with masses <50 amu. This result suggests a photochemical ablation process that occurs at any bond in the molecule. In addition, ions have been detected at very low fluence similar to the threshold of neutral detection, which is below 30 mJcm-2 for the triazene polymers and Kapton. The observation of ions from the onset of ablation suggests a 2-photon ablation mechanism and possibly involves an excited neutral as an intermediate step. The low thresholds were verified by ion probe measurements of the ablation plume and white-light interferometry of the ablated target surface.

Kuhnke, M.; Cramer, L.; Dyer, P. E.; Dickinson, J. T.; Lippert, T.; Niino, H.; Pervolaraki, M.; Walton, C. D.; Wokaun, A.

2007-04-01

141

Calcified lesion modeling for excimer laser ablation  

NASA Astrophysics Data System (ADS)

Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

2009-06-01

142

Pulsed holmium laser ablation of cardiac valves  

SciTech Connect

Ablation efficiency and residual thermal damage produced by pulsed holmium laser radiation were investigated in vitro for bovine mitral valves and human calcified and noncalcified cardiac valves. Low-OH quartz fibers (200 and 600 microns core diameter) were used in direct contact perpendicular to the specimen under saline or blood. Etch rate was measured with a linear motion transducer. Radiant exposure was varied from 0 to 3 kJ/cm{sup 2}. For 200-microns fibers, the energy of ablation was approximately 5 kJ/cm{sup 3} in noncalcified and 15 kJ/cm{sup 3} in calcified valves. Etch rates were dependent on mechanical tissue properties. Maximum etch rate at 1,000 J/cm{sup 2} was 1-2 mm/pulse at 3 Hz repetition rate. Microscopic examination revealed a zone of thermal damage extending 300 microns lateral into adjacent tissue. Thermal damage was independent of radiant exposure beyond twice threshold.

Lilge, L.; Radtke, W.; Nishioka, N.S. (Massachusetts General Hospital, Boston (USA))

1989-01-01

143

Dynamics of laser ablation of biological tissues  

NASA Astrophysics Data System (ADS)

We have developed a subnanosecond time resolution ultrafast photographic setup that can be used both as shadowgraph and Schlieren apparatus. With this setup a detailed study of the time history of the plume ejection and shock wave propagation have been preformed. We have shown that the shock wave fronts follow the behaviour predicted by shock wave theories, and that the planar shock wave fronts travel always perpendicular to the ablated surface. In addition to the earlier known hemispherical shock wave a new, head-wave type wave front was found that is presumably caused by a bunch of very fast particles preceding the formation of the main ablation plume. We have shown that the dynamics of short pulse Nd laser induced cavitation bubbles is considerably different in water and bovine cornea.

Bor, Z.; Szabó, G.; Hopp, B.; Márton, Zs.; Juhász, T.

1993-10-01

144

Laser Ablation Plume Expansion In The Presence Of Charged Impurities  

SciTech Connect

The expansion of plasma created by laser ablation is investigated using the fluid model. At the first stage of the expansion, electrons are considered in thermal equilibrium. The presence of highly charged impurities is considered through Poisson's equation. The set of nonlinear differential equations is solved using a moving boundary and taken into account the charge separation effect. The uniformly distributed impurities can accelerate or decelerate the ion motion depending on their charge and concentration. It is also found that the separation of the charge is valid for a specific time which depends on the impurities parameters.

Djebli, M. [Centre de Developpement des Technologies Avancees. Baba Hassen 16303 Algiers (Algeria); Theoretical Physics Laboratory, Faculty of Physics-USTHB-, B. P. 32 Bab Ezzouar 16079, Algiers (Algeria)

2008-09-23

145

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser  

PubMed Central

Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation.

Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

2011-01-01

146

Ablation plasma ion implantation using a dc power supply  

NASA Astrophysics Data System (ADS)

Experiments are reported in which ablation plasma ion implantation (APII) has been demonstrated using a dc power supply. The ability to use a dc power supply for APII has been accomplished by using a perpendicular orientation between the target and the substrate. This perpendicular orientation significantly reduces the arcing between the target and the substrate, in contrast to previous experiments using a parallel target-substrate orientation. With this new technique a KrF laser may be fired during the dc high voltage, accelerating full-energy ions. Initial experiments using dc APII have shown that Ti is deposited and implanted onto the Si substrate, with the highest concentration of Ti located beneath the surface of the film. The deposition/implantation of Ti ions onto Si was verified by X-ray photoelectron spectroscopy.

Jones, M. C.; Gilgenbach, R. M.; Qi, B.; Lau, Y. Y.; Doll, G. L.

147

Internal Explosion in Laser Ablation of Superconducting Targets.  

National Technical Information Service (NTIS)

The temperature profile inside a superconducting target in laser ablation is calculated for laser pulses of various shapes. The calculation is based on the equation of heat conduction. All parameters characterizing the target material are assumed to be te...

D. L. Lin X. Li Z. D. Liu T. F. George

1992-01-01

148

Study of Particle Generation During Laser Ablation with Applications.  

National Technical Information Service (NTIS)

A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained i...

C. Liu

2005-01-01

149

Rayleigh-Taylor instability in ion beam driven ablation fronts  

NASA Astrophysics Data System (ADS)

A physical model for the linear stage of Rayleigh-Taylor instability in ablation fronts is presented. The model allows for direct physical interpretation and for retrieving the well known results for the instability growth rate in ablation fronts driven by thermal diffusion. The model is applied to ablation fronts directly driven by intense ion beams and the instability growth rate is found. We show that ablation by itself still provides a mechanism for growth rate reduction but the cutoff wave number above which the front becomes stable, does no exist in ion beam driven ablation fronts.

Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

2009-08-01

150

Experimental scaling law for mass ablation rate from a Sn plasma generated by a 1064 nm laser  

SciTech Connect

The ablation depth in planar Sn targets irradiated with a pulsed 1064 nm laser was investigated over laser intensities from 3x10{sup 11} to 2x10{sup 12} W/cm{sup 2}. The ablation depth was measured by irradiating a thin layer of Sn evaporated onto a Si wafer, and looking for signatures of Si ions in the expanding plasma with spectroscopic and particle diagnostics. It was found that ablation depth scales with laser intensity to the (5/9)th power, which is consistent with analytical models of steady-state laser ablation, as well as empirical formulae from previous studies of mass ablation rate in overlapping parameter space. In addition, the scaling of mass ablation rate with atomic number of the target as given by empirical formulae in previous studies using targets such as C and Al, are shown to remain valid for the higher atomic number of the target (Z=50) used in these experiments.

Burdt, Russell A.; Yuspeh, Sam; Najmabadi, Farrokh [Center for Energy Research, University of California San Diego, La Jolla, California 92093-0417 (United States); Electrical and Computer Engineering, University of California San Diego, La Jolla, California 92093-0407 (United States); Sequoia, Kevin L.; Tao Yezheng; Tillack, Mark S. [Center for Energy Research, University of California San Diego, La Jolla, California 92093-0417 (United States)

2009-08-01

151

Critical-Point Phase Separation in Laser Ablation of Conductors  

NASA Astrophysics Data System (ADS)

Laser ablation due to an ultrashort laser pulse on a massive aluminum target was investigated by means of a one-dimensional fluid code. Clear separation between the ablated matter and the unablated target is seen to occur through spinodal decomposition involving thermodynamic instabilities near the critical point of aluminum. The code also shows that the end of the ablation process is preceded by the ejection of droplets, which form about 15% of the total ejected mass.

Vidal, F.; Johnston, T. W.; Laville, S.; Barthélemy, O.; Chaker, M.; Le Drogoff, B.; Margot, J.; Sabsabi, M.

2001-03-01

152

Mechanistic studies of resonant infrared laser ablation of polystyrene  

Microsoft Academic Search

We investigate the phenomenon of resonant-infrared laser ablation of polymers using polystyrene as a model material. Ablation is initiated by a picosecond free-electron laser tuned to various infrared wavelengths that are resonant with vibrational modes of a polystyrene target. Time-resolved plume imaging, coupled with etch-depth measurements and finite-element calculations of the temperature rise indicate that ablation begins after a superheated

S. L. Johnson; R. F. Haglund; D. M. Bubb

2009-01-01

153

Antibacterial effects of laser ablated Ni nanoparticles  

NASA Astrophysics Data System (ADS)

The interaction of nickel nanoparticles with Escherichia coli (E. coli) bacteria has been studied. The nickel nanoparticles have been fabricated by continuous wave laser ablation of nickel target and their properties are studied using different characterization techniques. The antibacterial activity of nickel nanoparticles was checked against E. coli bacteria. Escherichia coli were cultured in nutrients broth and different concentrations of nickel nanoparticles were added to bacterial culture solution to investigate the interaction of nickel nanoparticles with bacteria and to check toxicity of the nickel nanoparticles against E. coli. The fabricated Ni nanoparticles have exhibited considerable antimicrobial activity against E. coli.

Shamaila, S.; Wali, H.; Sharif, R.; Nazir, J.; Zafar, N.; Rafique, M. S.

2013-10-01

154

Diagnostics Techniques of Plasmas Produced by Laser Ablation  

NASA Astrophysics Data System (ADS)

Laser ablation in addition for thin film growing is also used for analytical techniques as Laser Induced Breakdown Spectroscopy and for applications as simulation of natural lightning. In this work we present several diagnostic techniques such as probe beam deflection, shadowgraphy, interferometry, pulsed laser photoacoustic and the electrical perturbation induced by laser ablation plasmas that's gives essential information of the plasma, hot core air and shock wave expansion.

Villagrán Muniz, M.; Sobral, H.; Sánchez Aké, C.; Sanginés de Castro, R.; Sterling, E.; Bredice, F.

2005-04-01

155

Characterization of water contribution to excimer laser ablation of collagen  

Microsoft Academic Search

In order to gain an obvious insight into the role of water in the mechanism of the excimer laser ablation of the cornea, we have macroscopically investigated the ablation behavior of collagen gel in the swelled state by direct photoetching using an ArF excimer laser with time-resolved photography, and furthermore, the thermal effects on the microscopic structures of the collagen

Katsunori Tsunoda; Masaru Sugiura; Masashi Sonoyama; Hirofumi Yajima; Tadahiro Ishii; Jiro Taniyama; Hiroshi Itoh

2001-01-01

156

Laser ablation of aluminum from normal evaporation to phase explosion  

SciTech Connect

A study of laser ablation of Aluminum sample by nanosecond laser pulses considering two simultaneous mechanisms of normal evaporation and phase explosion is theoretically carried out. The temperature distribution in the sample is calculated by a one dimensional heat conduction equation. Ablation depth due to the evaporation and explosion is calculated as a function of laser pulse energies. Variation in some effective sample parameters during the laser ablation and their effects on laser ablation mechanisms are taken into account. At low irradiance, ablation is mainly due to the evaporation, while after a threshold intensity, the phase explosion becomes the dominant mechanism. Theoretical results of transition from the normal evaporation to the phase explosion are in good agreement with the experimental results.

Gragossian, A.; Tavassoli, S. H.; Shokri, B. [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 1983963113 (Iran, Islamic Republic of)

2009-05-15

157

Ablation and analysis of small cell populations and single cells by consecutive laser pulses  

NASA Astrophysics Data System (ADS)

Laser ablation of single cells through a sharpened optical fiber is used for the detection of metabolites by laser ablation electrospray ionization (LAESI) mass spectrometry (MS). Ablation of the same Allium cepa epidermal cell by consecutive pulses indicates the rupture of the cell wall by the second shot. Intracellular sucrose heterogeneity is detected by subsequent laser pulses pointing to rupturing the vacuolar membrane by the third exposure. Ion production by bursts of laser pulses shows that the drying of ruptured A. cepa cells occurs in ˜50 s at low pulse rates (10 pulses/s bursts) and significantly faster at high pulse rates (100 pulses/s bursts). These results point to the competing role of cytoplasm ejection and evaporative drying in diminishing the LAESI-MS signal in ˜50 s or 100 laser pulses, whichever occurs first.

Shrestha, Bindesh; Nemes, Peter; Vertes, Akos

2010-10-01

158

Determination of ablation threshold of copper alloy with orthogonal dual-pulse laser-ablation laser-induced breakdown spectroscopy.  

PubMed

Orthogonal dual-pulse laser-ablation laser-induced breakdown spectroscopy was first used to determine the laser-ablation threshold of samples. In this technique, the first laser pulse was used to ablate samples and the second time-delayed laser pulse was used to break down the ablated samples. Orthogonal geometric arrangement was adopted in this technique to ensure both high spatial resolution and high detection sensitivity. By monitoring the intensities of the atomic emission of the plasma under different pulse energies of the ablation laser and using an extrapolation method, the minimum pulse energy needed for the ablation of copper alloy under the tightly focused condition with a nanosecond 532 nm ablation laser was determined to be 1.9±0.1 ?J. After experimentally determining the beam spot size on the focal plan, the fluence threshold of the studied sample was determined to be 0.64±0.06 J/cm². This technique is able to realize direct and sensitive determination of a laser-ablation threshold of solid samples, and it is possible to find some important applications in different fields. PMID:23938407

Zhou, Qi; Chen, Yuqi; Peng, Feifei; Yang, Xuejiao; Li, Runhua

2013-08-10

159

Note: Laser ablation technique for electrically contacting a buried implant layer in single crystal diamond  

SciTech Connect

The creation of thin, buried, and electrically conducting layers within an otherwise insulating diamond by annealed ion implantation damage is well known. Establishing facile electrical contact to the shallow buried layer has been an unmet challenge. We demonstrate a new method, based on laser micro-machining (laser ablation), to make reliable electrical contact to a buried implant layer in diamond. Comparison is made to focused ion beam milling.

Ray, M. P.; Baldwin, J. W.; Butler, J. E.; Pate, B. B. [U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Feygelson, T. I. [SAIC, 1220 12th St. SE, Washington, DC 20003 (United States)

2011-05-15

160

Molecular dynamics simulation of ultrafast laser ablation of fused silica film  

NASA Astrophysics Data System (ADS)

Ultrafast laser ablation of fused silica is studied using molecular dynamics simulations. Ionization and generation of free electrons, absorption of the laser energy by free electrons and energy coupling between free electrons and ions are considered. The BKS potential is applied and modified to describe molecular interactions and the effect of free electrons. Smooth particle mesh of the Ewald method (SPME) is adopted to calculate the Coulomb force. It is found that the electrostatic Coulomb force, which is caused by the ionization, plays an important role in the laser ablation process.

Wang, Y.; Xu, X.; Zheng, L.

2008-09-01

161

Nanosecond pulsed laser ablation of silicon in liquids  

Microsoft Academic Search

Laser fluence and laser shot number are important parameters for pulse laser based micromachining of silicon in liquids. This\\u000a paper presents laser-induced ablation of silicon in liquids of the dimethyl sulfoxide (DMSO) and the water at different applied\\u000a laser fluence levels and laser shot numbers. The experimental results are conducted using 15 ns pulsed laser irradiation at\\u000a 532 nm. The

R. Karimzadeh; J. Zamir Anvari; N. Mansour

2009-01-01

162

Planning and simulation of microsurgical laser bone ablation  

Microsoft Academic Search

Purpose  Laser ablation of hard tissue is not completely understood until now and not modeled for computer-assisted microsurgery. A\\u000a precise planning and simulation is an essential step toward the usage of microsurgical laser bone ablation in the operating\\u000a room.\\u000a \\u000a \\u000a \\u000a Methods  Planning the volume for laser bone ablation is based on geometrical definitions. Shape and volume of the removed bone by single\\u000a laser

Lüder Alexander Kahrs; Jessica Burgner; Thomas Klenzner; Jörg Raczkowsky; Jörg Schipper; Heinz Wörn

2010-01-01

163

Metal particles produced by laser ablation for ICP-MSmeasurements  

SciTech Connect

Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm{sup -2}. Characterization of particles and correlation with Inductively Coupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of {approx} 50 and {approx} 12 for fs vs. ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the {sup 66}Zn transient signal by a factor of ten compared to nanosecond laser pulses.

Gonzalez, Jhanis J.; Liu, Chunyi; Wen, Sy-Bor; Mao, Xianglei; Russo, Richard E.

2007-06-01

164

Momentum coupling efficiency of laser ablation for space debris removal  

Microsoft Academic Search

This paper will discuss the laser conditions for producing efficient thrust on debris. In order to obtain high thrust for given laser energies, thermal energies dissipated into laser ablation and debris bulk have to be minimized. It was suggested that this minimization can be achieved by using ultrashort pulse interactions where laser pulse duration is too short for thermal conduction

Shigeaki Uchida; Xianglin Zhou; Kazuo Imasaki; Chiyoe Yamanaka; Tatsuhiko Yamanaka; Masayuki Niino; Tatsuo Kunagai; Wiliam Kmetic; Masatsugu Ishimoto; Nobuki Kawashima

2000-01-01

165

Pulse laser ablation at water–air interface  

Microsoft Academic Search

We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the\\u000a refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that\\u000a laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser

Yuji Utsunomiya; Takashi Kajiwara; Takashi Nishiyama; Kunihito Nagayama; Shiro Kubota

2010-01-01

166

Application of Laser Ablation Processing in Electric Power System Industries  

NASA Astrophysics Data System (ADS)

The present status of laser ablation processing applied in electric power system industries is reviewed. High average power LD-pumped Nd:YAG lasers with Q-switch have been developed and currently introduced into various applications. Optical fiber based laser beam delivery systems for Q-switched pulse laser are also being developed these years. Based on such laser and beam delivery technology, laser ablation processes are gradually introduced in maintenance of nuclear power plant, thermal power plant and electrical power distribution system. Cost effectiveness, robustness and reliability of the process is highly required for wide utilization in these fields.

Konagai, Chikara; Sano, Yuji; Nittoh, Koichi; Kuwako, Akira

167

Atomistic simulation of laser ablation of gold: Effect of pressure relaxation  

SciTech Connect

The process of ablation of a gold target by femto- and picosecond laser radiation pulses has been studied by numerical simulations using an atomistic model with allowance for the electron subsystem and the dependence of the ion-ion interaction potential on the electron temperature. Using this potential, it is possible to take into account the change in the physical properties of the ion subsystem as a result of heating of the electron subsystem. The results of simulations reveal a significant difference between the characteristics of metal ablation by laser pulses of various durations. For ablation with subpicosecond pulses, two mechanisms of metal fracture related to the evolution of electronic pressure in the system are established.

Norman, G. E.; Starikov, S. V., E-mail: starikov@ihed.ras.ru; Stegailov, V. V. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2012-05-15

168

Femtosecond Laser Ablation Regimes in a Single-Crystal Superalloy  

NASA Astrophysics Data System (ADS)

Femtosecond (fs, 10-15 second) laser ablation of single-crystal nickel-base superalloy CMSX-4 under laser fluences ranging from 0.1 to 160 J/cm2 has been investigated. For comparison, the ablation behaviors of Ni and Ni3Al as individual components of the superalloy have also been studied. Two distinct ablation regimes were observed, dependent on the incident laser fluence. The ablation threshold fluences for these two ablation regimes were determined to be ? _{{th1}} = 0.30 ± 0.03 and ? {}_{{th2}} = 5.3 ± 0.5 J/cm2 in the superalloy. Ablation thresholds for the single-phase Ni and Ni3Al alloys were close to those measured for two-phase superalloy. The two distinct surface morphologies produced by ablation in these regimes were characterized in detail by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The ablation rate equations for the two regimes are presented and the corresponding ablation mechanisms are discussed. The implications for application of fs pulsed lasers to machining of superalloys are also discussed.

Ma, S.; McDonald, J. P.; Tryon, B.; Yalisove, S. M.; Pollock, T. M.

2007-09-01

169

Investigations on laser hard tissue ablation under various environments.  

PubMed

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 microm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy. PMID:18523347

Kang, H W; Oh, J; Welch, A J

2008-06-03

170

Investigations on laser hard tissue ablation under various environments  

NASA Astrophysics Data System (ADS)

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 µm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

Kang, H. W.; Oh, J.; Welch, A. J.

2008-06-01

171

Laser ablation of UHMWPE-polyethylene by 438 nm high energy pulsed laser  

Microsoft Academic Search

Pulsed laser ablation of ultra-high-molecular-weight-polyethylene (UHMWPE) is investigated at Prague Asterix Laser System (PALS) Laboratory. The high ablation yield as a function of laser energy is presented at 438nm laser wavelength. The mechanisms of the polymer ablation are studied on the base of “in situ” analysis, such as mass quadrupole spectrometry and time-of-flight measurements, and “ex situ” analysis, such as

L. Torrisi; S. Gammino; A. M. Mezzasalma; A. M. Visco; J. Badziak; P. Parys; J. Wolowski; E. Woryna; J. Krasa; L. Laska; M. Pfeifer; K. Rohlena; F. P. Boody

2004-01-01

172

Influence of wavelength, irradiance, and the buffer gas pressure on high irradiance laser ablation and ionization source coupled with an orthogonal Time of Flight Mass Spectrometer  

Microsoft Academic Search

Influence of laser wavelength, laser irradiance and the buffer gas pressure were studied in high irradiance laser ablation and ionization source coupled with an orthogonal time-of-flight mass spectrometer. Collisional cooling effects of energetic plasma ions were proved to vary significantly with the elemental mass number. Effective dissociation of interferential polyatomic ions in the ion source, resulting from collision and from

Rongfu Huang; Quan Yu; Qingguo Tong; Wei Hang; Jian He; Benli Huang

2009-01-01

173

Amalgam ablation with the Er:YAG laser  

NASA Astrophysics Data System (ADS)

Any laser that will be used by dentist to replace the dental drill (handpiece) must remove dental hard tissues safely. These lasers must also have the ability to ablate the restorative dental materials which are present in the teeth being treated. Prior to any laser being used to treat humans a thorough knowledge of the effects of the laser treatment on dental materials must be understood. Cores of dental amalgam were created and sliced into thin wafers for this experiment. Ablation efficiency and thermal changes were evaluated with and without water. It appears as if the Er:YAG laser can effectively ablate amalgam dental material with and without water. The water prevents the temperature from increasing much above baseline and does not reduce efficiency of ablation.

Wigdor, Harvey A.; Visuri, Steven R.; Walsh, Joseph T.

1995-04-01

174

Picosecond laser ablation of nickel-based superalloy C263  

Microsoft Academic Search

Picosecond laser (10.4 ps, 1064 nm) ablation of the nickel-based superalloy C263 is investigated at different pulse repetition\\u000a rates (5, 10, 20, and 50 kHz). The two ablation regimes corresponding to ablation dominated by the optical penetration depth\\u000a at low fluences and of the electron thermal diffusion length at high fluences are clearly identified from the change of the\\u000a surface morphology of single

N. G. Semaltianos; W. Perrie; J. Cheng; M. Sharp; G. Dearden; K. G. Watkins

2010-01-01

175

Pulsed Tm:YAG laser ablation of knee joint tissues  

NASA Astrophysics Data System (ADS)

We investigated the effect of a free-running 2.01 micron pulsed Tm:YAG laser on bovine knee joint tissues. Ablation rates of fresh fibrocartilage, hyaline cartilage, and bone were measured in saline as a function of laser fluence (160 - 640 J/cm2) and fiber core size (400 and 600 microns). All tissues could be effectively ablated and the ablation rate increased linearly with the increasing fluence. Use of fibers of different core sizes, while maintaining constant energy fluence, did not result in significant difference in ablation rate. Histology analyses of the ablated tissue samples reveal average Tm:YAG radiation induced thermal damage (denatunalization) zones ranging between 130 and 540 microns, depending on the laser parameters and the tissue type.

Shi, Wei-Qiang; Vari, Sandor G.; Duffy, J. T.; Miller, J. M.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

1992-06-01

176

Simulation of cluster formation in laser-ablated silicon plumes  

Microsoft Academic Search

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 cluster size is obtained by incorporating diffusion of ambient

Sushmita R. Franklin; R. K. Thareja

2005-01-01

177

Direct Drive Beryllium Ablator Capsules for the Omega Laser  

Microsoft Academic Search

We are designing direct drive beryllium ablator capsules for the Omega laser as part of our effort to develop beryllium ablator ignition capsules for the National Ignition Facility (NIF). The main goals for this experimental campaign is to develop the fabrication expertise for roughly NIF size capsules and obtain experimental data on how the copper- brazed joint between the beryllium

P. A. Bradley; D. C. Wilson; J. A. Cobble; T. J. Murphy; J. C. Cooley; M. A. Salazar; G. Rivera Nobile Jr.

2001-01-01

178

Transient States of Matter during Short Pulse Laser Ablation  

Microsoft Academic Search

Short pulse laser ablation of semiconductors and metals is studied by means of ultrafast time-resolved microscopy. The characteristic stages of the conversion of solid material into hot fluid matter undergoing ablation are identified. Initially metallic material transforms during the expansion into a transparent state with a high index of refraction.

K. Sokolowski-Tinten; J. Bialkowski; A. Cavalleri; D. von der Linde; A. Oparin; J. Meyer-Ter-Vehn; S. I. Anisimov

1998-01-01

179

Damage/ablation morphology of laser conditioned sapphire under 1064 nm laser irradiation  

NASA Astrophysics Data System (ADS)

The damage/ablation morphologies and laser induced damage threshold (LIDT) of three different sapphire samples: original, 1064 nm laser conditioned and 10.6 ?m CO2 laser polished substrates are investigated with ns pulses laser irradiation. The results indicate that the damage resistance capability cannot be enhanced by 1064 nm laser conditioning or CO2 laser polishing. The damage/ablation morphology of 1064 nm-laser conditioned samples is same as that of the original sapphire. But it is different from the damage/ablation morphology of the CO2 laser polished sapphire. The “gentle and strong” ablation phases are observed in this work and several phenomena are observed in the two ablation phases. Ripple is observed in the “gentle” ablation processes, while convex spots and raised rims are observed in the “strong” ablation processes. Meanwhile, stripe damage and pin-points are observed in the CO2 laser conditioned sapphire after ns laser irradiation. The formation mechanisms of the phenomena are also discussed for the explanation of related damage/ablation morphology. The results may be helpful for the damage/ablation investigation of sapphire in high power laser systems.

Jiang, Y.; Xiang, X.; Wang, H. J.; Yuan, X. D.; He, S. B.; Lv, H. B.; Zheng, W. G.; Zu, X. T.

2012-06-01

180

Laser tattoo removal with preceding ablative fractional treatment  

NASA Astrophysics Data System (ADS)

A combined laser tattoo removal treatment, first the ablative fractional resurfacing (AFR) with an Er:YAG laser and then the q-switched (QSW) Nd:YAG laser treatment, was studied. Experiments show that significantly higher fluences can be used for the same tissue damage levels.

Cenci?, Boris; Možina, Janez; Jezeršek, Matija

2013-06-01

181

A Miniaturized Laser Ablation Mass Spectrometer for Space Research  

NASA Astrophysics Data System (ADS)

In this abstract we present current performance of our miniaturized Laser Ablation Time-of-Flight Mass Spectrometer (LMS) to be used for in-situ planetary missions and laboratory elemental and isotopic analyzes.

Riedo, A.; Fernandes, V. A. S. M.; Yakovleva, M.; Tulej, M.; Wurz, P.

2011-03-01

182

Growth of multilayered epitaxial films by pulsed excimer laser ablation  

SciTech Connect

The characteristics of pulsed laser ablation for epitaxial film growth are reviewed. New developments in the growth of heteroepitaxial multilayers, stabilization of metastable phases, and growth of semiconductor alloys with continuously variable composition, are described.

Lowndes, D.H.

1993-06-01

183

Laser ablation of iron: A comparison between femtosecond and picosecond laser pulses  

NASA Astrophysics Data System (ADS)

In this study, a comparison between femtosecond (fs) and picosecond (ps) laser ablation of electrolytic iron was carried out in ambient air. Experiments were conducted using a Ti:sapphire laser that emits radiation at 785 nm and at pulse widths of 110 ps and 130 fs, before and after pulse compression, respectively. Ablation rates were calculated from the depth of craters produced by multiple laser pulses incident normally to the target surface. Optical and scanning electron microscopy showed that picosecond laser pulses create craters that are deeper than those created by the same number of femtosecond laser pulses at the same fluence. Most of the ablated material was ejected from the ablation site in the form of large particles (few microns in size) in the case of picosecond laser ablation, while small particles (few hundred nanometers) were produced in femtosecond laser ablation. Thermal effects were apparent at high fluence in both femtosecond and picosecond laser ablation, but were less prevalent at low fluence, closer to the ablation threshold of the material. The quality of craters produced by femtosecond laser ablation at low fluence is better than those created at high fluence or using picosecond laser pulses.

Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

2013-08-01

184

Interaction of flows of laser ablation plasmas  

SciTech Connect

Our studies of laser pulsed deposition of thin films, using 20-ns second-harmonic Nd:YAG laser operated at a few GW/cm{sup 2}, show that introduction of an obstacle like a grid screen into ablation plume with typical density 10{sup 18}cm{sup {minus}3} and temperature 3 eV substantially affects dynamics of plasma expansion and results in dramatic changes of plasma parameters. In this work, we report the effects typical for the later stage of plasma-grid interaction{emdash}effects related to the interaction of multiple plasma flows. Model experiments, performed employing method of emission spectroscopy, time-of-flight technique, and plasma imaging with CCD camera, show significant variation of plasma composition and transformation of velocity distribution due to plasmas interaction. Two modes of such transformation have been observed: linear growth of density in the resulting flow, and formation of the additional slow peak in the velocity distribution. The effect is shown to be velocity-resonant. {copyright} {ital 1997 American Institute of Physics.}

Derkach, Ogel M.; Sebrant, Andrey Y. [Institute for Laser Physics, Sadovaya-Spasskaya 21-151, Moscow, 107078 (Russia); Grishina, Valeria G. [TRINITI, Troitsk, Moscow Reg., 142092 (Russia)] Baranov, Vladimir Y. [National Research Center---Kurchatov Institute, Kurchatov Square, Moscow, 123098 (Russia)] Stepanova, Maria A. [Resonetics, Inc., 4 Bud Way No. 21, Nashua, New Hampshire 03063 (United States)

1997-04-01

185

Interaction of flows of laser ablation plasmas  

SciTech Connect

Our studies of laser pulsed deposition of thin films, using 20-ns second-harmonic Nd:YAG laser operated at a few GW/cm{sup 2}, show that introduction of an obstacle like a grid screen into ablation plume with typical density 10{sup 18} cm{sup -3} and temperature 3 eV substantially affects dynamics of plasma expansion and results in dramatic changes of plasma parameters. In this work, we report the effects typical for the later stage of plasma-grid interaction--effects related to the interaction of multiple plasma flows. Model experiments, performed employing method of emission spectroscopy, time-of-flight technique, and plasma imaging with CCD camera, show significant variation of plasma composition and transformation of velocity distribution due to plasmas interaction. Two modes of such transformation have been observed: linear growth of density in the resulting flow, and formation of the additional slow peak in the velocity distribution. The effect is shown to be velocity-resonant.

Derkach, Oleg N.; Sebrant, Andrey Y. [Institute for Laser Physics, Sadovaya-Spasskaya 21-151, Moscow, 107078 (Russian Federation); Anisimov, Vladimir N.; Grishina, Valeria G. [TRINITI, Troitsk, Moscow Reg., 142092 (Russian Federation); Baranov, Vladimir Y. [National Research Center--Kurchatov Institute, Kurchatov Square, Moscow, 123098 (Russian Federation); Stepanova, Maria A. [Resonetics, Inc., 4 Bud Way 21, Nashua, New Hampshire 03063 (United States)

1997-04-15

186

Resonant holographic measurements of laser ablation plume expansion in vacuum and argon gas backgrounds  

Microsoft Academic Search

This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; the study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; the solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume

Roger Alan Lindley

1993-01-01

187

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

NASA Astrophysics Data System (ADS)

Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

Liedahl, Duane A.; Libby, Stephen B.; Rubenchik, Alexander

2010-10-01

188

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

SciTech Connect

Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

Liedahl, Duane A.; Libby, Stephen B.; Rubenchik, Alexander [Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550 (United States)

2010-10-08

189

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

SciTech Connect

Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

Liedahl, D A; Libby, S B; Rubenchik, A

2010-02-04

190

A review of Thulium fiber laser ablation of kidney stones  

Microsoft Academic Search

The clinical solid-state Holmium:YAG laser lithotripter (lambda=2120 nm) is capable of operating at high pulse energies, but its efficient operation is limited to low pulse rates during lithotripsy. The diode-pumped experimental Thulium Fiber Laser (lambda=1908 nm) is limited to low pulse energies, but can operate at high pulse rates. This review compares stone ablation threshold, ablation rate, and retropulsion effects

Nathaniel M. Fried; Richard L. Blackmon; Pierce B. Irby

2011-01-01

191

Two-Dimensional Effects in Laser Ablation of Carbon  

Microsoft Academic Search

This article studies the importance of two-dimensional effects in laser ablation of carbon. It describes the process by using the kinetic theory model of laser ablation based on the moment solution of the Boltzmann equation for arbitrary strong evaporation, and compares the predictions of the full two-dimensional model and of the two other models that use quasi-one-dimensional approximation in the

Michael Shusser

2009-01-01

192

Hyperthermal Pulsed-Laser Ablation Beams for Film Deposition and Surface Microstructural Engineering  

SciTech Connect

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 several hundred eV down to {approximately}0.1 eV and films ranging from superhard to nanocrystalline may be deposited. Furthermore, cumulative (multi-pulse) irradiation of a semiconductor surface (e.g. silicon) in an oxidizing gas (0{sub 2}, SF{sub 6}) et atmospheric pressure can produce dense, self-organized arrays of high-aspect-ratio microcolumns or microcones. Thus, a wide range of materials synthesis and processing opportunities result from the hyperthermal flux and reactive growth conditions provided by pulsed-laser ablation.

Lowndes, D.H.

1999-11-08

193

Time-resolved studies of particle effects in laser ablation inductively coupled plasma-mass spectrometry  

SciTech Connect

Time resolved signals in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are studied to determine the influence of experimental parameters on ICP-induced fractionation effects. Differences in sample composition and morphology, i.e., ablating brass, glass, or dust pellets, have a profound effect on the time resolved signal. Helium transport gas significantly decreases large positive signal spikes arising from large particles in the ICP. A binder for pellets also reduces the abundance and amplitude of spikes in the signal. MO{sup +} ions also yield signal spikes, but these MO{sup +} spikes generally occur at different times from their atomic ion counterparts.

Perdian, D.; Bajic, S.; Baldwin, D.; Houk, R.

2007-11-13

194

High Current Cathodes Fabricated by KrF Laser Ablation  

SciTech Connect

In this paper we review several high power laser ablation techniques that have been utilized to fabricate high current (1-80 kA) electron beam cathodes for accelerators and microwave sources: 1) Projection Ablation Lithography (PAL) cathodes, 2) Ablation Line Focus (ALF) cathodes, and 3) Metal-Oxide-Junction (MOJ) cathodes. Laser-ablative micromachining techniques (PAL and ALF) have been utilized to generate micron-scale features on metal substrates that provide electric field (beta) enhancement for Fowler-Nordheim emission and plasma cathodes. Since these laser-ablated patterns are directly, laser-written on the substrate metal they exhibit much higher thermal conductivity for higher current capability and increased damage thresholds. Metal-Oxide-Junction (MOJ) cathodes exploit the triple-point electron emission that occurs at the interface between metal, insulator and vacuum.The ablation laser is a KrF excimer laser with a pulse energy of 600 mJ and pulselength of 20 ns. Cathode experiments were performed on the MELBA-C accelerator: V = -300 kV, pulselength = 0.5 microsecond. Data will be presented for PAL, ALF and MOJ cathodes.

Gilgenbach, Ronald M.; Lau, Y. Y. [Plasma, Pulsed-Power and Microwave Laboratory Nuclear Engineering and Radiological Sciences Department University of Michigan, Ann Arbor, MI 48109 (United States); Jones, M. C.; Johnston, M. D. [Sandia National Labs, Albuquerque, NM (United States); Jordan, N. M. [Cybernet Systems, Ann Arbor, MI (United States); Hoff, B. W. [Air Force Research Labs, Kirtland AFB, NM (United States)

2010-10-08

195

Will nonablative rejuvenation replace ablative lasers? Facts and controversies.  

PubMed

Since the early 1980s, the field of skin rejuvenation has evolved rapidly. Traditional ablative resurfacing with carbon dioxide and Er:YAG lasers offered dramatic improvement of the skin tone and texture, but prolonged postoperative period and an increased risk for side effects and complications were unacceptable for the majority of patients. It prompted the development of nonablative lasers and non-laser systems, which stimulate dermal neocollagenesis without epidermal disruption, and therefore, produce less adverse effects with little or no healing time. Recently, fractional nonablative and ablative lasers have been introduced, employing a completely new concept of fractional photothermolysis, which ensures high efficacy and fewer risks. Ablative laser resurfacing still remains the gold standard for treating advanced and severe photoaging providing excellent results in experienced hands. Alternatively, ablative fractional resurfacing can be used, with the results, which are comparable to fully ablative lasers with better standard of safety. Nonablative resurfacing is ideal for patients under the age of 50 years with minimal facial sagging, and for those who are unwilling to undergo expensive and demanding ablative procedures. It can be concluded that the key of therapeutic success is in proper patient selection, setting appropriate expectations and combining different rejuvenation technologies with other therapeutic modalities, such as botulinum toxin and fillers. PMID:24160276

Lipozen?i?, Jasna; Mokos, Zrinka Bukvi?

196

Dynamics of the plumes produced by ultrafast laser ablation of metals  

SciTech Connect

We have analyzed ultrafast laser ablation of a metallic target (Nickel) in high vacuum addressing both expansion dynamics of the various plume components (ionic and nanoparticle) and basic properties of the ultrafast laser ablation process. While the ion temporal profile and ion angular distribution were analyzed by means of Langmuir ion probe technique, the angular distribution of the nanoparticulate component was characterized by measuring the thickness map of deposition on a transparent substrate. The amount of ablated material per pulse was found by applying scanning white light interferometry to craters produced on a stationary target. We have also compared the angular distribution of both the ionic and nanoparticle components with the Anisimov model. While the agreement for the ion angular distribution is very good at any laser fluence (from ablation threshold up to {approx_equal}1 J/cm{sup 2}), some discrepancies of nanoparticle plume angular distribution at fluencies above {approx_equal}0.4 J/cm{sup 2} are interpreted in terms of the influence of the pressure exerted by the nascent atomic plasma plume on the initial hydrodynamic evolution of the nanoparticle component. Finally, analyses of the fluence threshold and maximum ablation depth were also carried out, and compared to predictions of theoretical models. Our results indicate that the absorbed energy is spread over a length comparable with the electron diffusion depth L{sub c} ({approx_equal}30 nm) of Ni on the timescale of electron-phonon equilibration and that a logarithmic dependence is well-suited for the description of the variation in the ablation depth on laser fluence in the investigated range.

Donnelly, T.; Lunney, J. G. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Amoruso, S.; Bruzzese, R.; Wang, X. [Dipartimento di Scienze Fisiche and CNR-SPIN, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Ni, X. [Department of Electronic Engineering, Tianjin University of Technology and Education, Tianjin 300222 (China)

2010-08-15

197

Porcine cortical bone ablation by ultrashort pulsed laser irradiation  

NASA Astrophysics Data System (ADS)

Ultrashort pulsed lasers in bone ablation show promise for many orthopedic applications. To minimize collateral tissue damage and control the ablation process, the ablation threshold fluence must be well characterized. Using an amplified femtosecond laser (170 fs, 800 nm, 1 kHz), the ablation threshold on unaltered porcine cortical bone was measured using the D2 method at multiple incident pulse numbers ranging from 25 to 1000 pulses per spot. The lowered threshold at greater pulse numbers indicated an incubation effect. Using a power law model, the incubation coefficient of unaltered porcine cortical bone was found to be 0.89 +/- 0.03. Through extrapolation, the single-pulse ablation threshold was found to be 3.29 +/- 0.14 J/cm2.

Emigh, Brent; An, Ran; Hsu, Eugene M.; Crawford, Travis H. R.; Haugen, Harold K.; Wohl, Gregory R.; Hayward, Joseph E.; Fang, Qiyin

2012-02-01

198

Laser ablation of a turbid medium: Modeling and experimental results  

SciTech Connect

Q-switched Nd:YAG laser ablation of a turbid medium (paint) is studied. The optical properties (absorption coefficient, scattering coefficient, and its anisotropy) of a paint are determined with a multiple scattering model (three-flux model), and from measurements of reflection-transmission of light through thin layers. The energy deposition profiles are calculated at wavelengths of 532 nm and 1.064 {mu}m. They are different from those described by a Lambert-Beer law. In particular, the energy deposition of the laser beam is not maximum on the surface but at some depth inside the medium. The ablated rate was measured for the two wavelengths and compared with the energy deposition profile predicted by the model. This allows us to understand the evolution of the ablated depth with the wavelength: the more the scattering coefficient is higher, the more the ablated depth and the threshold fluence of ablation decrease.

Brygo, F.; Semerok, A.; Weulersse, J.-M.; Thro, P.-Y.; Oltra, R. [Commissariat a l'Energie Atomique, DEN/DANS/DPC/SCP/LILM, Batiment 467, 91191 Gifs/Yvette (France); LRRS-UMR 5613 CNRS, Universite de Bourgogne 21078 Dijon (France)

2006-08-01

199

Polarization-resolved measurements of picosecond laser-ablated plumes  

SciTech Connect

We discuss the ablation of aluminum plasma using picosecond pulsed laser in vacuum and in ambient atmosphere of nitrogen. The plume dynamics of picosecond and nanosecond laser-ablated plumes in ambient atmosphere is discussed. The degree of polarization is measured using optical emission spectroscopy for the Al III transition 4s {sup 2}S{sub 1/2}-4p {sup 2}P{sub 3/2}{sup o} at 569.6 nm. Strong anisotropy is observed using picosecond laser pulse as compared to nanosecond laser pulse.

Sharma, A.K.; Thareja, R.K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

2005-08-01

200

Laser ablation of a platinum target in water. I. Ablation mechanisms  

SciTech Connect

This is the first in a series of three papers aimed at better understanding the processes that lead to nanomaterial formation during laser ablation of solid targets in liquids. Here we study the variation of the target surface morphology versus laser fluence and wavelength in order to suggest an ablation mechanism. A key finding is that an explosive ablation mechanism is prominent for a wide range of laser fluences for all wavelengths tested. Interestingly, however, ultraviolet (355 nm) and infrared (1064 nm) wavelengths show characteristically different explosive behaviors. In the infrared case, numerous large craters with diameters around 20 {mu}m form at localized points within the laser irradiated area. In contrast, ultraviolet ablation results in a striking transition to nanoscale surface roughness across the entire irradiated area. This texture is attributed to spinodal decomposition at the molten target surface. We propose that the wavelength and fluence dependence of the ablation craters can be explained by the amount of energy absorbed in the target. The consequences of the ablation mechanism for nanomaterial synthesis are discussed.

Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto [Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

2006-12-01

201

Microporous polymer surfaces prepared by an excimer laser ablation technique.  

PubMed

This paper presents an excimer laser microprocessing method to prepare microporous polymer surfaces. The irradiation of a KrF excimer laser (248 nm) was applied to several polymer films by passing a laser pulse through an optical microscope, resulting in ablative photodecomposition. The control unit was designed to control the fluence of the laser, pulse number, size of irradiated areas, and irradiation micropositioning. The ablation depth linearly increased with an increase in the accumulation of pulses. The chemical composition of the ablated surfaces did not vary with the accumulation of pulses, confirmed by x-ray photoelectron spectroscopy measurements. Excellent structuring quality of ablated micropores was obtained for polyurethane, polyimide, and polycarbonate films. As an application of the ablation technique, polyurethane films were micropored by the excimer laser ablation technique in conjunction with open-cell structured, small diameter grafts under development. In vitro cell ingrowth and compliance on the micropored polyurethane films were examined. Rapid ingrowth was observed on pore sizes of a few microns to several tenths of a micron in diameter. Higher density micropores provided enhanced elastomeric properties. PMID:8555583

Nakayama, Y; Matsuda, T

202

Efficient space propulsion engines based on laser ablation  

SciTech Connect

Recent results have shown laser momentum transfer coefficients C{sub m} as large as 700 dynes/J from visible and near-infrared laser pulses with heterogeneous targets. Using inexpensive target materials, it is now possible to deliver a 1-tonne satellite from LEO to GEO in 21 days using a 10-kW onboard laser ablation engine, or to maintain several 1-tonne GEO satellites on station from Earth indefinitely using a laser with 100-W average power.

Phipps, C.R.

1993-08-01

203

Total energy loss to fast ablator-ions and target capacitance of direct-drive implosions on OMEGA  

NASA Astrophysics Data System (ADS)

Measurements of the total energy carried by fast ablator-ions in direct-drive implosions on OMEGA have been conducted using magnetic and Thomson Parabola spectrometers. It is shown that the total laser energy lost to fast ablator-ions for plastic and glass targets is comparable and that it is a modest fraction of the incident laser energy (<~1%). These measurements have been used to infer a non-linear, voltage-dependent target capacitance (~0.1 nF) associated with the space-charge that accelerates the fast-ions.

Sinenian, N.; Zylstra, A. B.; Manuel, M. J.-E.; Rinderknecht, H. G.; Frenje, J. A.; Séguin, F. H.; Li, C. K.; Petrasso, R. D.; Goncharov, V.; Delettrez, J.; Igumenshchev, I. V.; Froula, D. H.; Stoeckl, C.; Sangster, T. C.; Meyerhofer, D. D.; Cobble, J. A.; Hicks, D. G.

2012-09-01

204

Improving Consistency in Laser Ablation Geochronology  

NASA Astrophysics Data System (ADS)

Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; San Francisco, California, 12-13 December 2009; The use of uranium-thorium-lead (U-Th-Pb) laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) geochronology involves rapid analysis of U-and Th-rich accessory minerals. It routinely achieves 1-2% precision for U-Th-Pb dates constituting detrital mineral age spectra and for dating igneous and metamorphic events. The speed and low setup and analysis cost of LA-ICP-MS U-Th-Pb geochronology has led to a proliferation of active laboratories. Tens of thousands of analyses are produced per month, but there is little agreement on how to transform these data into accurate U-Th-Pb dates. Recent interlaboratory blind comparisons of zircon samples indicate that resolvable biases exist among laboratories and the sources of bias are not fully understood. Common protocols of data reduction and reporting are essential for scientists to be able to compare and interpret these data accurately.

Horstwood, Matt; Gehrels, George; Bowring, James

2010-07-01

205

Synthesis of gold nanoparticles by laser ablation of an Au foil inside and outside ionic liquids.  

PubMed

Stable gold nanoparticles (AuNPs) were prepared by simple laser ablation of an Au foil placed inside or outside four ionic liquids (ILs), without the addition of any external chemical reagent. Irregular spherical AuNPs with a diameter range of 5 to 20 nm were produced after laser ablation of an Au foil located inside or outside the ILs 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI·PF6) and 1-(3-cyanopropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BCN)MI·NTf2). Additionally, whereas laser ablation inside the IL 1-n-butyl-3-methylimidazolium dicyanamide BMI·N(CN)2 produced flower-like shaped nanoparticles of about 50 nm in size, ablation outside this IL presented similar results to the others ILs studied, as determined by TEM and UV-Vis. The size and shape of the prepared NPs were related to where NP nucleation and growth occurred, i.e., at the IL surface or within the IL. Indeed, the chemical composition of the IL/air interface and surface ion orientation played important roles in the stabilization of the AuNPs formed by laser ablation outside the ILs. PMID:21267499

Wender, Heberton; Andreazza, Marcos L; Correia, Ricardo R B; Teixeira, Sérgio R; Dupont, Jairton

2011-01-26

206

Synthesis of gold nanoparticles by laser ablation of an Au foil inside and outside ionic liquids  

NASA Astrophysics Data System (ADS)

Stable gold nanoparticles (AuNPs) were prepared by simple laser ablation of an Au foil placed inside or outside four ionic liquids (ILs), without the addition of any external chemical reagent. Irregular spherical AuNPs with a diameter range of 5 to 20 nm were produced after laser ablation of an Au foil located inside or outside the ILs 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF6) and 1-(3-cyanopropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BCN)MI.NTf2). Additionally, whereas laser ablation inside the IL 1-n-butyl-3-methylimidazolium dicyanamide BMI.N(CN)2 produced flower-like shaped nanoparticles of about 50 nm in size, ablation outside this IL presented similar results to the others ILs studied, as determined by TEM and UV-Vis. The size and shape of the prepared NPs were related to where NP nucleation and growth occurred, i.e., at the IL surface or within the IL. Indeed, the chemical composition of the IL/air interface and surface ion orientation played important roles in the stabilization of the AuNPs formed by laser ablation outside the ILs.

Wender, Heberton; Andreazza, Marcos L.; Correia, Ricardo R. B.; Teixeira, Sérgio R.; Dupont, Jairton

2011-03-01

207

Time progression of ultrashort laser ablation in a transparent material  

NASA Astrophysics Data System (ADS)

Laser ablation on the ultra-short-pulses regime (femtosecond), has an impact on materials processing and micromachining in a quite profound ways. The investigation of the time progression of the laser ablation process within the material can produce much information and it is not conventionally used. The implementation of such study is the main aim of this paper. The temporal dependence of the diameter and depth of micro-drilling in the sample was verified, beyond the simple understanding of the mechanism for plasma generated during the ablation. From the monitoring of the time progression of the ablation, the time dependence for the velocity of ablation had been determined. In most cases, fume attenuation of the incoming laser beam and fume escape paths, produce dominant influence the characteristics of the region ablated. The method here employed is simple and can be carried out in real time without interruption of the process. In the implemented method light scattered from an auxiliary source allow visualization and record of the ablated geometry as it progress.

Nicolodelli, G.; Lizarelli, R. F. Z.; Costa, M. M.; Bagnato, V. S.

2011-08-01

208

Characterization of laser ablation and ionization in helium and argon: A comparative study by time-of-flight mass spectrometry  

Microsoft Academic Search

Laser ablation and ionization in ambient helium and argon gases were studied by multiple-stage time-of-flight mass spectrometry. Measurements made at different gas pressures indicated that there exists an optimal pressure for adequately cooling energetic ions and reducing multiply charged ions that are higher for He than for Ar. The temporal distributions of ions were compared at various laser fluences and

Yiming Lin; Quan Yu; Rongfu Huang; Wei Hang; Jian He; Benli Huang

2009-01-01

209

Dependence of gold nanoparticle production on pulse duration by laser ablation in liquid media  

Microsoft Academic Search

The dependence on laser fluence and laser pulse duration of size, size distribution and concentration of gold nanoparticles synthesized by laser ablation in liquid media was investigated. It was demonstrated that increasing laser energy from 1 to 5 mJ\\/pulse enhances the ablation rate by a factor of 100. The behavior of the ablation rate, hence of the nanoparticle concentration, as

Daria Riabinina; Mohamed Chaker; Joëlle Margot

2012-01-01

210

Ablation Plasma Ion Implantation using a DC Power Supply  

NASA Astrophysics Data System (ADS)

Experiments are reported in which ablation plasma ion implantation (APII) has been demonstrated using a DC power supply. DC APII has been accomplished by using a perpendicular orientation between the target and the substrate^ 1. By ejecting electrons from the gap, the perpendicular orientation significantly reduces the arcing between the target and the substrate, in contrast to previous experiments using a parallel target-substrate orientation. With this new technique the KrF laser may be fired during the DC high voltage (negative 4-18 kV), accelerating full energy ions. Initial experiments using DC APII have shown that Ti is deposited and implanted onto the Si substrate, with the highest concentration of Ti located beneath the surface of the film. The deposition/implantation of Ti ions onto Si was verified by X-ray photoelectron spectroscopy. ^1 B. Qi, R.M. Gilgenbach, M.C. Jones, M.D. Johnston, Y.Y. Lau, L.M. Wang, J. Lian, G.L. Doll, and A. Lazarides, J. Appl. Phys., 93, 8876, (2003) Research Partially Supported by NSF

Jones, M. C.; Gilgenbach, R. M.; Qi, Bo; Lau, Y. Y.; Johnston, M. D.; Doll, G. L.

2003-10-01

211

Direct Laser Ablation and Ionization of Solids for Chemical Analysis by Mass Spectrometry  

SciTech Connect

A laser ablation/ionization mass spectrometer system is described for the direct chemical analysis of solids. An Nd:YAG laser is used for ablation and ionization of the sample in a quadrupole ion trap operated in an ion-storage (IS) mode that is coupled with a reflectron time-of-flight mass spectrometer (TOF-MS). Single pulse experiments have demonstrated simultaneous detection of up to 14 elements present in glasses in the ppm range. However, detection of the components has produced non-stoichiometric results due to difference in ionization potentials and fractionation effects. Time-of-flight secondary ionization mass spectrometry (TOF-SIMS) was used to spatially map elemental species on the surface and provide further evidence of fractionation effects. Resolution (m/Dm) of 1500 and detection limits of approximately 10 pg have been achieved with a single laser pulse. The system configuration and related operating principles for accurately measuring low concentrations of isotopes are described.

Holt, J K; Nelson, E J; Klunder, G L

2005-09-02

212

Metal ablation by picosecond laser pulses: A hybrid simulation  

Microsoft Academic Search

We investigate picosecond laser ablation of metals using a hybrid simulation scheme. Laser energy input into the electron system and heat conduction within it are modeled using a finite-difference scheme for solving the heat conduction equation. Atom motion in the near-surface part (72 nm) of the sample is modeled using molecular dynamics. Energy transfer between the electronic and atomic subsystems

Carsten Schäfer; Herbert M. Urbassek; Leonid V. Zhigilei

2002-01-01

213

UV Laser Ablation of Parylene Films from Gold Substrates.  

National Technical Information Service (NTIS)

Parylene films, coating gold substrates, were removed by laser ablation using 248 nm light from an excimer laser. Each sample was processed by a different number of pulses in one of three different environments: air at atmospheric pressure, nitrogen at at...

J. M. Wrobel M. B. Kruger O. R. Musaev P. Scott

2009-01-01

214

Laser ablation machining of metal\\/polymer composite materials  

Microsoft Academic Search

This paper reports on the laser machining of metallic materials by the ablation of a low temperature polymer binding material. Through initial compacting and infiltration of various blends of metal powders with a low temperature polymer binding material, it is possible to laser machine high surface quality three-dimensional parts. The machining mechanism has been found to be one of absorption

A. Slocombe; L Li

2000-01-01

215

UV solid state laser ablation of intraocular lenses  

NASA Astrophysics Data System (ADS)

Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (?=355 nm and ?=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at ?=213 nm reveal a smooth optical surface on the intraocular lens with no irregularities, observed with other wavelengths.

Apostolopoulos, A.; Lagiou, D. P.; Evangelatos, Ch.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

2013-06-01

216

Laser ablation and influence of Debye temperature and laser parameters on size and number of nanoparticles  

Microsoft Academic Search

Dependence of size and number of nanoparticles on kind of material, power of laser and pulse duration of laser in laser ablation is investigated by presenting a model based on Debye model for specific heat capacity. Simulations from the theory demonstrate that there is a critical power of laser which is very important for controlling size of nanoparticles in laser

Majid Vaezzadeh; Mohammadreza Saeidi; Mohsen Zarei

2010-01-01

217

Power dependence of size of laser ablated colloidal silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles have been produced by laser ablation of silver metal in nanopure water without any chemical additives. It has been observed that laser power has a control over the size of the nanoparticles. Increasing laser power shows a clear blue shift in the absorption peak of fabricated nanoparticles indicating that the average size of the particles decreases with increasing laser power. Ablation for longer period reduces the average size of nanoparticles which is attributed to the re-ablation of fabricated nanoparticles. A good correlation has been observed between the peak of the absorption spectrum measured by UV-VIS spectroscopy and the average particle size measured by scanning electron microscope imaging method. The value of the coefficient of correlation is determined to be 0.965.

Talukder, A. I.; Sultana, P.; Haider, A. F. M. Y.; Wahadoszamen, M.; Abedin, K. M.; Farhad, S. F. U.

2010-11-01

218

Femtosecond laser near-field ablation from gold nanoparticles  

NASA Astrophysics Data System (ADS)

Short-pulse laser ablation is promising owing to the low threshold for material removal from surfaces. In the laser-ablation process, solid material transforms into a volatile phase initiated by a rapid deposition of energy. Explosive boiling can be one of the mechanisms in which matter is heated close to the critical point. Other pathways of non-thermal excitation will be present for very short laser pulses. Here we observe a different channel of ablation from gold nanoparticles, which takes place below the particle melting point. This process is induced by the optical near-field, a subwavelength field enhancement close to curved surfaces, in particular. Using picosecond X-ray scattering, we can track the temporal and energetic structural dynamics during material ejection from the nanoparticles. This effect will limit any high-power laser manipulation of nanostructured surfaces, such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses.

Plech, Anton; Kotaidis, Vassilios; Lorenc, Maciej; Boneberg, Johannes

2006-01-01

219

Measurements of the ablator-ion energy-loss channel in direct-drive implosions on OMEGA  

NASA Astrophysics Data System (ADS)

Measurements of ablator-ion spectra produced in direct-drive experiments on the OMEGA laser facility are presented. These ablator-ions are accelerated by the presence of hot electrons generated by laser-plasma interactions. Extensive measurements have been made with two magnet-based charged-particle spectrometers and more recently, with a Thomson Parabola Ion Energy Analyzer. The maximum ion energy and total energy carried by the ions depend strongly on the laser intensity and that as much as 3-4% of the incident laser energy is lost to these ions. The ablator-ion energy spectra from warm (CH) and cryogenic (D2/DT) targets have been used to infer the temperature of the hot electrons, and the results are in good agreement with hard x-ray inferred temperatures. Using the ablator-ion method combined with modeling of the initial electron energy distribution function, the level of preheat has been estimated. This work was supported in part by DOE, LLE and LLNL.

Sinenian, N.; Frenje, J.; Li, C. K.; Seguin, F. H.; Petrasso, R.; Delettrez, J.; Stoeckl, C.; Goncharov, V.

2011-11-01

220

Mechanism of Resonant Mid-Infrared Laser Ablation of Polystyrene  

NASA Astrophysics Data System (ADS)

We investigated the mechanism of resonant-infrared laser ablation of polymers using polystyrene as a model material. The ablation laser was a picosecond mid-infrared free-electron laser tuned to mid-IR laser wavelengths that are resonant with specific vibrational modes of the polystyrene target. Time-resolved plume imaging combined with etch-depth measurements and finite-element calculations indicate that a blowoff model fits the experimentally measured etch depths and plume images, provided one accounts for moderate shielding of the surface by the ablation plume. The finite-element model includes the temperature-dependent absorption coefficient and specific heat that dramatically change the material properties above the glass-transition temperature. Ablation begins after a thin surface layer of the material is superheated to temperatures exceeding 1000 C and undergoes spinodal decomposition. The majority of the ablated material is then expelled by way of recoil-induced ejection as the pressure of the expanding vapor plume compresses a laser-melted area at the target surface.

Haglund, Richard; Johnson, Stephen; Bubb, Daniel

2009-03-01

221

Performance and Controllability of Pulsed Ion Beam Ablation Propulsion  

SciTech Connect

We propose novel propulsion driven by ablation plasma pressures produced by the irradiation of pulsed ion beams onto a propellant. The ion beam ablation propulsion demonstrates by a thin foil (50 {mu}mt), and the flyer velocity of 7.7 km/s at the ion beam energy density of 2 kJ/cm2 adopted by using the Time-of-flight method is observed numerically and experimentally. We estimate the performance of the ion beam ablation propulsion as specific impulse of 3600 s and impulse bit density of 1700 Ns/m2 obtained from the demonstration results. In the numerical analysis, a one-dimensional hydrodynamic model with ion beam energy depositions is used. The control of the ion beam kinetic energy is only improvement of the performance but also propellant consumption. The spacecraft driven by the ion beam ablation provides high performance efficiency with short-pulsed ion beam irradiation. The numerical results of the advanced model explained latent heat and real gas equation of state agreed well with experimental ones over a wide range of the incident ion beam energy density.

Yazawa, Masaru; Buttapeng, Chainarong; Harada, Nobuhiro [Nagaoka University of Technology, Department of Electrical Engineering, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Suematsu, Hisayuki; Jiang Weihua; Yatsui, Kiyoshi [Nagaoka University of Technology, Extreme Energy-Density Research Institute, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188 (Japan)

2006-05-02

222

Laser Ablation of Biological Tissue Using Pulsed CO{sub 2} Laser  

SciTech Connect

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO{sub 2} laser (wavelength: 10.6 {mu}m; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi [School of Science and Engineering, Electric and Electronics Engineering, Kinki University, 3-4-1 Kowakae, Higashi-Osaka City, Osaka, 577-8502 (Japan)

2010-10-13

223

Micro-optic fabrication using laser ablation process  

Microsoft Academic Search

The feasibility of laser ablation in micro-machining of 3D structure of MEMS (Micro Electro Mechanical Systems) parts, specifically micro optics was studied in this paper. The micro-machining characteristics of polymer such as etching rate vs. energy fluence, number of pulse are investigated experimentally. The threshold energy density of polyurethane is about 30 mJ\\/cm2 and ablated depth per pulse can be

Won-Seok Chang; Kyung-Ku Yoon; Jaegu Kim; Bosung Shin; Kyung-Hyun Whang

2002-01-01

224

Diagnostics of laser ablated plasmas using fast photography  

NASA Astrophysics Data System (ADS)

We report on dynamics of the laser ablated plumes in an ambient atmosphere using fast photography. The expanding plasma is studied at different delay times with respect to the ablating pulse. Dependence of plasma parameters such as velocity, temperature, density, and pressure on time and ambient atmosphere is presented. The images of the expanding plume are used to estimate the size of the particles in the plume.

Misra, A.; Mitra, A.; Thareja, R. K.

1999-02-01

225

Molecular dynamics simulations studies of laser ablation in metals  

SciTech Connect

An overview of several aspects of our recent molecular dynamics simulations of femtosecond laser ablation is presented. This includes the study of phase diagrams for suitable interactions, analysis of ablated material and bubble formation below threshold, study of two-pulse ablation and the classification of materials with respect to electron properties and electron-phonon coupling in the two-temperature model. A treatment of boundary conditions and of an extended twotemperature model is also included. Most of the results apply to aluminum, others also to copper and iron, and to metals in general.

Roth, Johannes; Sonntag, Steffen; Karlin, Johannes; Paredes, Carolina Trichet; Sartison, Marc; Krauss, Armin; Trebin, Hans-Rainer [Institute for Theoretical and Applied Physics, University Stuttgart, Pfaffenwaldring 57/IV, 70550 Stuttgart (Germany)

2012-07-30

226

The DCU laser ion source  

Microsoft Academic Search

Laser ion sources are used to generate and deliver highly charged ions of various masses and energies. We present details on the design and basic parameters of the DCU laser ion source (LIS). The theoretical aspects of a high voltage (HV) linear LIS are presented and the main issues surrounding laser-plasma formation, ion extraction and modeling of beam transport in

P. Yeates; J. T. Costello; E. T. Kennedy

2010-01-01

227

Modeling and computer simulation of pulsed-laser-induced ablation  

NASA Astrophysics Data System (ADS)

The paper introduces a 3D analytical model to calculate the ablation rate induced by a laser pulse on a semi-infinite slab of material of finite thickness. The model concerns first the thermal field induced by irradiation in order that the ablation process fulfils some prefixed boundary conditions, then the fluence of the laser pulse is calculated by consequence. Inputs of the problem are therefore the properties of the ablation process such as drilling width and depth, sputter rate, and so on. Some examples of computer simulation are carried out to show the outputs of the model, in particular as concerns the correlation between shape of the ablated zone and space and time profile of laser pulse. The influence of thickness on the aspect ratio (width/depth) of the hole is discussed by comparing the surface and in-depth propagation rates of the ablation boundary. The results show that the present model enables one to describe a wide variety of ablation processes with aspect ratios ranging from values of the order of some tens, typical for instance of surface cleaning, etching or deoxidation treatments, down to values of the order of 0.05, typical of hole drilling.

Tosto, S.

228

Novel CO2 laser system for hard tissue ablation  

Microsoft Academic Search

A line-tunable and variable pulselength CO2 laser system for ablation of dental and bone tissues has been tested. To avoid the undesirable effects of plasma formation, acoustic shock waves and collateral thermal damage to the tissues, we have found an optimum laser pulselength in the 10 - 20 microseconds range. At a fluence of 30 J\\/cm2 and laser wavelength of

Vladimir B. Krapchev; Christopher D. Rabii; James A. Harrington

1994-01-01

229

Mechanical stress power measurements during high-power laser ablation  

Microsoft Academic Search

Laser-induced stresses have been studied extensively to understand macroscopic phenomenon during high-power laser ablation of solids. Recently, a norm of stress times the rate of change in stress, similar to mechanical stress power, was monitored acoustically in the target and ambient medium during high-power laser-material interactions, and compared with stress measurements. This study investigates the relationship between stress and the

Mark A. Shannon; Boris Rubinsky; Richard E. Russo

1996-01-01

230

Laser ablation and influence of Debye temperature and laser parameters on size and number of nanoparticles  

NASA Astrophysics Data System (ADS)

Dependence of size and number of nanoparticles on kind of material, power of laser and pulse duration of laser in laser ablation is investigated by presenting a model based on Debye model for specific heat capacity. Simulations from the theory demonstrate that there is a critical power of laser which is very important for controlling size of nanoparticles in laser ablation method. The critical power of laser depends on material Debye temperature and pulse duration of laser. Finally difference between experimental diagrams of zinc and carbon is explained by using results of the theory.

Vaezzadeh, Majid; Saeidi, Mohammadreza; Zarei, Mohsen

2010-03-01

231

Fabrication of iron oxide nanoparticles using laser ablation in liquids  

NASA Astrophysics Data System (ADS)

Nanoparticles of iron oxides were synthesized through the ablation of the bulk-targets of Fe, Fe3O4, and Fe2O3 in water by the irradiation of a Nd:YAG laser. Our samples prepared via the laser ablation method displayed small (ca. 1 nm in diameter) and large (over 5 nm in diameter) particles. The small particles were well-dispersed, whereas large particles were agglomerated. The FeO and Fe3O4 phases were formed in the synthesized powders irrespective of the kind of targets. The formation of the other phases, Fe and Fe2O3, changed depending on the the kind of targets used in the laser ablation. Poly(N-vinyl-2-pyrrolidone) (PVP) as a protective reagent was employed to disperse large particles in our samples, and accordingly, their dispersibility was improved as mole concentration of PVP increased.

Iwamoto, T.; Ishigaki, T.

2013-06-01

232

Ultrafast laser ablation of gold thin film targets  

SciTech Connect

Ultrafast laser ablation of a gold thin film is studied and compared with that of a bulk target, with particular emphasis given to the process of nanoparticles generation. The process is carried out in a condition where a single laser shot removes all the irradiated film spot. The experimental results evidence interesting differences and, in particular, a reduction of the nanoparticles size, and a narrowing of a factor two of their size distribution in the case of ablation of a thin film target, a feature which we relate to a more uniform heating of the target material. We thus show that ultrashort laser ablation of thin films provides a promising way of controlling plume features and nanoparticles size.

Amoruso, S.; Ausanio, G.; Bruzzese, R. [Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Nedyalkov, N. N.; Atanasov, P. A. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsaridradsko shose Boulevard, Sofia 1784 (Bulgaria); Wang, X. [CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy)

2011-12-15

233

Glass particles produced by laser ablation for ICP-MSmeasurements  

SciTech Connect

Pulsed laser ablation (266nm) was used to generate glass particles from two sets of standard reference materials using femtosecond (150fs) and nanosecond (4ns) laser pulses with identical fluences of 50 J cm{sup -2}. Scanning electron microscopy (SEM) images of the collected particles revealed that there are more and larger agglomerations of particles produced by nanosecond laser ablation. In contrast to the earlier findings for metal alloy samples, no correlation between the concentration of major elements and the median particle size was found. When the current data on glass were compared with the metal alloy data, there were clear differences in terms of particle size, crater depth, heat affected zone, and ICP-MS response. For example, glass particles were larger than metal alloy particles, the craters in glass were less deep than craters in metal alloys, and damage to the sample was less pronounced in glass compared to metal alloys samples. The femtosecond laser generated more intense ICP-MS signals compared to nanosecond laser ablation for both types of samples, although glass sample behavior was more similar between ns and fs-laser ablation than for metals alloys.

Gonzalez, J.; Liu, C.; Wen, S.; Mao, X.; Russo, R.E.

2007-06-01

234

RODEO MRI guided laser ablation of breast cancer  

NASA Astrophysics Data System (ADS)

This study explores the feasibility of image directed laser ablation of breast tumors as an alternative to traditional surgery. A series of 22 treatments were performed in 12 patients. The cancers were targeted with pre- and post- gadolinium enhanced RODEO breast MRI. 18 g MRI compatible needles were stereotaxically placed with RODEO breast MRI guidance. Laser ablation was implemented with a diode laser at 3 watts of power for about 500 seconds. The treatment was performed interactively with dynamic RODEO MRI control. The treatment zone was manifested as a hypointense zone on the dynamic images. The needle or treatment duration can be adjusted during the course of the ablation depending upon the location of the tumor and hypointense zone. In all cases correlation with conventional surgical excision with serial sectioning of the specimen was performed. PCNA stains of the treatment zone was used to confirm effective ablation and correlate the treatment zone size with the hypointense zone demonstrated on MRI. This study demonstrates the potential for RODEO breast MRI as an effective method for coordinating the interactive deliver of laser ablation in the treatment of breast cancer.

Harms, Steven E.; Mumtaz, Hamid; Hyslop, Brian; Klimberg, Suzanne; Westbrook, Kent; Kourourian, Sohelia

1999-06-01

235

Ultraviolet metal ion laser  

SciTech Connect

A metal ion laser is described comprising: a cylindrical vacuum enclosure having a longitudinal axis that is coincident with an unobstructed longitudinal optical axis defined by a resonant optical cavity comprising two mirrors, one at each end thereof, one or both of which mirrors are employed to extract poser from the laser; a cylindrical magnetron sputtering source positioned coaxially with an adjacent to the cylindrical vacuum enclosure; two annular shaped cold cathodes each having diameter substantially equal to the diameter of the cylindrical vacuum enclosure and the two cylindrical anodes; power supply means electrically connected to the metal ion laser for causing the cylindrical magnetron sputtering source to sputter metal vapor from the cylindrical metal cathode tube and for creating rare gas ions.

Collins, G.J.; McNeil, J.R.

1988-03-08

236

Spatio-temporal mapping of ablated species in ultrafast laser-produced graphite plasmas  

SciTech Connect

We studied the spatial and temporal distributions of ionic, neutral, and molecular species generated by femtosecond laser produced plasma under varying ambient nitrogen gas pressures. Plasmas were generated by irradiating planar graphite targets using 40 fs pulses of 800 nm radiation from a Ti:Sapphire laser. The results show that in the presence of an ambient gas, the molecular species spatial extension and lifetime are directly correlated to the evolution of excited ions. The present studies also provide valuable insights into the evolution history of various species and their excitation during ultrafast laser ablation.

Al-Shboul, K. F.; Harilal, S. S.; Hassanein, A. [Center for Materials Under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2012-05-28

237

Accumulated IR-laser ablation of endothel at the inner wall of Schlemm's canal  

NASA Astrophysics Data System (ADS)

The typical approach for tissue ablation in laser microsurgery is to use a fiber tip in the contact-mode. An example is the laser trabecular ablation ab interno. The purpose of this paper is to describe the trabecular meshwork ablation with an Er:YAG laser in the none contact mode from inside Schlemm's canal using cavitations bubbles.

Specht, Holger; Voelcker, Hans E.; Burk, Reinhard O.

2001-06-01

238

Ablation characteristics of Au, Ag, and Cu metals using a femtosecond Ti:sapphire laser  

Microsoft Academic Search

Femtosecond laser ablation of metallic bulk crystals of Au, Ag and Cu was experimentally studied with laser pulse widths ranging from 120 fs through 800 fs at a center wavelength of 780 nm for micro-machining applications. Two different ablation regimes were found in terms of the laser fluence. The characteristic length of different ablation regimes was explained in terms of

K. Furusawa; K. Takahashi; H. Kumagai; K. Midorikawa; M. Obara

1999-01-01

239

Fundamental Mechanisms of Pulsed Laser Ablation of Biological Tissue  

NASA Astrophysics Data System (ADS)

The ability to cut and remove biological tissue with short pulsed laser light, a process called laser ablation, has the potential to revolutionize many surgical procedures. Ablation procedures using short pulsed lasers are currently being developed or used in many fields of medicine, including cardiology, ophthalmology, dermatology, dentistry, orthopedics, and urology. Despite this, the underlying physics of the ablation process is not well understood. In fact, there is wide disagreement over whether the fundamental mechanism is primarily photothermal, photomechanical, or photochemical. In this thesis, both experimental and theoretical techniques are developed to explore this issue. The photothermal model postulates that ablation proceeds through vaporization of the target material. The photomechanical model asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. I have developed a three dimensional model of the thermoelastic response of tissue to short pulsed laser irradiation which allows the time dependent stress distribution to be calculated given the optical, thermal and mechanical properties of the target. A complimentary experimental technique has been developed to verify this model, measure the needed physical properties of the tissue, and record the thermoelastic response of the tissue at the onset of ablation. The results of this work have been widely disseminated to the international research community and have led to significant findings which support the photomechanical model of ablation of tissue. First, the energy deposited in tissue is an order of magnitude less than that required for vaporization. Second, unlike the one-dimensional thermoelastic model of laser-induced stress generation that has appeared in the literature, the full three-dimensional model predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to occur. Third, although the laser-induced temperature rise is modest, the magnitude of the stresses is sufficient to initiate mechanically destructive phenomenon. In hard materials, including bone, a gradual weakening of material with each successive laser pulse is observed and correlated with the formation of permanent microcracks within the material. In meniscus, a representative soft tissue, the growth and collapse of mechanically destructive cavitation bubbles is observed. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Albagli, Douglas

240

Laser ablation-miniature mass spectrometer for elemental and isotopic analysis of rocks.  

PubMed

A laser ablation-miniature mass spectrometer (LA-MMS) for the chemical and isotopic measurement of rocks and minerals is described. In the LA-MMS method, neutral atoms ablated by a pulsed laser are led into an electron impact ionization source, where they are ionized by a 70 eV electron beam. This results in a secondary ion pulse typically 10-100 ?s wide, compared to the original 5-10 ns laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer (MMS) and measured in parallel by a modified CCD array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LA-MMS offers a more quantitative assessment of elemental composition than techniques that detect ions directly generated by the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the wavelength of the laser beam, and the not well characterized ionization efficiencies of the elements in the process. The above problems attendant to the direct ion analysis has been minimized in the LA-MMS by analyzing the ablated neutral species after their post-ionization by electron impaction. These neutral species are much more abundant than the directly ablated ions in the ablated vapor plume and are, therefore, expected to be characteristic of the chemical composition of the solid. Also, the electron impact ionization of elements is well studied and their ionization cross sections are known and easy to find in databases. Currently, the LA-MMS limit of detection is 0.4 wt.%. Here we describe LA-MMS elemental composition measurements of various minerals including microcline, lepidolite, anorthoclase, and USGS BCR-2G samples. The measurements of high precision isotopic ratios including (41)K/(39)K (0.077 ± 0.004) and (29)Si/(28)Si (0.052 ± 0.006) in these minerals by LA-MMS are also described. The LA-MMS has been developed as a prototype instrument system for space applications for geochemical and geochronological measurements on the surface of extraterrestrial bodies. PMID:21974601

Sinha, M P; Neidholdt, E L; Hurowitz, J; Sturhahn, W; Beard, B; Hecht, M H

2011-09-01

241

Laser ablation-miniature mass spectrometer for elemental and isotopic analysis of rocks  

NASA Astrophysics Data System (ADS)

A laser ablation-miniature mass spectrometer (LA-MMS) for the chemical and isotopic measurement of rocks and minerals is described. In the LA-MMS method, neutral atoms ablated by a pulsed laser are led into an electron impact ionization source, where they are ionized by a 70 eV electron beam. This results in a secondary ion pulse typically 10-100 ?s wide, compared to the original 5-10 ns laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer (MMS) and measured in parallel by a modified CCD array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LA-MMS offers a more quantitative assessment of elemental composition than techniques that detect ions directly generated by the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the wavelength of the laser beam, and the not well characterized ionization efficiencies of the elements in the process. The above problems attendant to the direct ion analysis has been minimized in the LA-MMS by analyzing the ablated neutral species after their post-ionization by electron impaction. These neutral species are much more abundant than the directly ablated ions in the ablated vapor plume and are, therefore, expected to be characteristic of the chemical composition of the solid. Also, the electron impact ionization of elements is well studied and their ionization cross sections are known and easy to find in databases. Currently, the LA-MMS limit of detection is 0.4 wt.%. Here we describe LA-MMS elemental composition measurements of various minerals including microcline, lepidolite, anorthoclase, and USGS BCR-2G samples. The measurements of high precision isotopic ratios including 41K/39K (0.077 +/- 0.004) and 29Si/28Si (0.052 +/- 0.006) in these minerals by LA-MMS are also described. The LA-MMS has been developed as a prototype instrument system for space applications for geochemical and geochronological measurements on the surface of extraterrestrial bodies.

Sinha, M. P.; Neidholdt, E. L.; Hurowitz, J.; Sturhahn, W.; Beard, B.; Hecht, M. H.

2011-09-01

242

Vibration testing based on impulse response excited by laser ablation  

NASA Astrophysics Data System (ADS)

This paper proposes an innovative vibration testing method based on impulse response excited by laser ablation. In conventional vibration testing using an impulse hammer, high-frequency elements of over tens of kilohertz are barely present in the excitation force. A pulsed high-power YAG laser is used in this study for producing an ideal impulse force on a structural surface. Illuminating a point on a metal with the well-focused YAG laser, laser ablation is caused by generation of plasma on the metal. As a result, an ideal impulse excitation force generated by laser ablation is applied to the point on the structure. Therefore, it is possible to measure high-frequency FRFs due to the laser excitation. A water droplet overlay on the metal is used to adjust the force magnitude of laser excitation. An aluminum block that has nine natural frequencies below 40 kHz is employed as a test piece. The validity of the proposed method is verified by comparing the FRFs of the block obtained by the laser excitation, impulse hammer, and finite element analysis. Furthermore, the relationship between accuracy of FRF measurements and sensitivity of sensors is investigated.

Kajiwara, Itsuro; Hosoya, Naoki

2011-10-01

243

CO{sub 2} Laser Ablation Propulsion Tractor Beams  

SciTech Connect

Manipulation of objects at a distance has already been achieved with no small measure of success in the realm of microscopic objects on the scale size of nanometers to micrometers in applications including laser trapping and laser tweezers. However, there has been relatively little effort to apply such remote control to macroscopic systems. A space tractor beam could be applied to a wide range of applications, including removal of orbital debris, facilitation of spacecraft docking, adjustment of satellite attitude or orbital position, etc. In this paper, an ablative laser propulsion tractor beam is demonstrated based on radiation from a CO{sub 2} laser. Cooperative, layered polymer targets were used for remote impulse generation using a CO{sub 2} laser. The use of a structured ablatant enabling switching between thrust directional parity (i.e., forward or reverse) and imparting torque to a remote target. Fluence-dependent results are presented in the context of polymer ablation modeling work and with consideration of confined ablation effects.

Sinko, John E. [Micro-Nano Global Center of Excellence, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan); Schlecht, Clifford A. [Institute for Materials and Complexity, Saint Louis, MO 63112 (United States)

2010-05-06

244

Laser trabecular ablation of human eyes with the erbium:YAG laser: a histopathologic study  

NASA Astrophysics Data System (ADS)

We postulated that ablation of trabecular meshwork can be accomplished without damage to Schlemm's canal and adjacent tissue. We performed Erbium:YAG laser trabecular ablation on human autopsy eyes and confirmed the results by histopathologic examination. We used an Erbium:YAG laser (2.94 micrometers ) equipped with a sapphire probe and a quartz tip (350 micrometers diameter). Energy levels of 5, 10, 15, 20, and 40 mJ per pulse were used. The probe was placed directly onto the trabecular meshwork viewed through an operating microscope and focal ablation was performed with single pulses. The tissue was then processed and examined under light and scanning microscopy. The histopathologic study of the trabecular meshwork revealed that a single pulse at an energy level of 15 mJ was optimal for ablating through the trabecular meshwork to Schlemm's canal with a minimal amount of coagulative damage to the surrounding tissue. The mean width of ablated tissue was 150 micrometers +/- 29 micrometers (n equals 18) and the mean depth of ablation was 133 +/- 48 micrometers (n equals 18) at this energy level. The mean width of coagulative damage to adjacent tissue was 16 +/- 8 micrometers (n equals 18). The ablation and coagulative damage increased with increasing energy levels. The Erbium:YAG laser equipped with a contact probe effectively ablates trabecular meshwork with little surrounding coagulative damage. This feature may minimize scarring and result in a high long-term patency rate of outflow channels created by laser trabecular ablation.

Kramer, Theresa R.; Noecker, Robert J.; Snyder, Robert W.; Ellsworth, Lansing G.; Yarborough, J. Michael

1994-06-01

245

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors  

SciTech Connect

A comparative experimental study of pulsed laser ablation in vacuum of two binary semiconductors, zinc oxide and indium phosphide, has been performed using IR- and visible laser pulses with particular attention to cluster generation. Neutral and cationic Zn{sub n}O{sub m} and In{sub n}P{sub m} particles of various stoichiometry have been produced and investigated by time-of-flight mass spectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters are mainly stoichiometric in the ablation plume. In contrast, indium phosphide clusters are strongly indium-rich with In{sub 4}P being a magic cluster. Analysis of the plume composition upon laser exposure has revealed congruent vaporization of ZnO and a disproportionate loss of phosphorus by the irradiated InP surface. Plume expansion conditions under ZnO ablation are shown to be favorable for stoichiometric cluster formation. A delayed vaporization of phosphorus under InP ablation has been observed that results in generation of off-stoichiometric clusters.

Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G. [Institute of Thermophysics SB RAS, Lavrentyev Ave. 1, 630090 Novosibirsk (Russian Federation); Ozerov, Igor; Marine, Wladimir [Universite de la Mediterranee, CINaM, UPR CNRS 3118, 13288 Marseille (France)

2010-10-08

246

Normal ferroelectric to relaxor behavior in laser ablated Ca-doped barium titanate thin films  

Microsoft Academic Search

Ba1-xCaxTiO3 thin films (x=0.05 to 0.17) were deposited on Pt-coated Si substrates using a pulsed excimer laser ablation technique. X-ray diffraction and scanning electron microscope studies of the Ba1-xCaxTiO3 targets exhibit a polycrystalline nature and thin films also show the same but with a significant orientation along the (111) direction. Secondary ion mass spectrometer analysis reveals the presence of a

P. Victor; R. Ranjith; S. B. Krupanidhi

2003-01-01

247

Study on the carbon fragment anions produced by femtosecond laser ablation of solid C60  

Microsoft Academic Search

Production of the anions (negative ions) has been observed by femtosecond laser ablation (fsLA) of solid C60 with a time-of-flight (TOF) mass spectrometer. In contrast to C60+, production of C60- due to an electron capture is found very limited because of the small electron affinity of the C60 molecule. Narrow TOF peaks of small carbon fragment anions Cn- (n <=

Tohru Kobayashi; Yukari Matsuo

2011-01-01

248

High resolution selective multilayer laser processing by nanosecond laser ablation of metal nanoparticle films  

SciTech Connect

Ablation of gold nanoparticle films on polymer was explored using a nanosecond pulsed laser, with the goal to achieve feature size reduction and functionality not amenable with inkjet printing. The ablation threshold fluence for the unsintered nanoparticle deposit was at least ten times lower than the reported threshold for the bulk film. This could be explained by the combined effects of melting temperature depression, lower conductive heat transfer loss, strong absorption of the incident laser beam, and the relatively weak bonding between nanoparticles. The ablation physics were verified by the nanoparticle sintering characterization, ablation threshold measurement, time resolved ablation plume shadowgraphs, analysis of ablation ejecta, and the measurement and calculation of optical properties. High resolution and clean feature fabrication with small energy and selective multilayer processing are demonstrated.

Ko, Seung H.; Pan Heng; Hwang, David J.; Chung, Jaewon; Ryu, Sangil; Grigoropoulos, Costas P.; Poulikakos, Dimos [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich (Switzerland)

2007-11-01

249

Dynamics of Femtosecond Laser Ablation Plume Studied With Ultrafast X-ray Absorption Fine Structure Imaging  

NASA Astrophysics Data System (ADS)

We investigated the dynamic process of an expanding femtosecond laser ablation plume of aluminum generated in an irradiation intensity range of 1013-1015 W/cm2 with the ultrafast x-ray absorption fine structure (XAFS) imaging technique. The XAFS spectra of the aluminum LII,III edge of the plume revealed that the plume consists of doubly and singly charged ions, neutral atoms, liquid particles, and possible atomic clusters. Scanning electron microscopy of deposited ablation particles confirmed that the liquid particles corresponds to the spherical nanoparticles with a size ranging from several tens nanometers to approximately 200 nm. The spatiotemporal evolution of the XAFS image of the plume shows the sequential appearance of each ablation particle from aluminum surface according to its ejection velocity. The result suggests that the photomechanical fragmentation process, which was theoretically proposed, is dominant mechanism for the nanoparticle ejection under the irradiation intensity far from the ablation threshold of aluminum. This study clearly demonstrates the potential of our technique for measuring the ultrafast dynamics of femtosecond laser ablation process.

Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

2010-10-01

250

CO2 Laser Ablation Propulsion Area Scaling With Polyoxymethylene Propellant  

NASA Astrophysics Data System (ADS)

The topic of area scaling is of great importance in the laser propulsion field, including applications to removal of space debris and to selection of size ranges for laser propulsion craft in air or vacuum conditions. To address this issue experimentally, a CO2 laser operating at up to 10 J was used to irradiate targets. Experiments were conducted in air and vacuum conditions over a range of areas from about 0.05-5 cm2 to ablate flat polyoxymethylene targets at several fluences. Theoretical effects affecting area scaling, such as rarefaction waves, thermal diffusion, and diffraction, are discussed in terms of the experimental results. Surface profilometry was used to characterize the ablation samples. A CFD model is used to facilitate analysis, and key results are compared between experimental and model considerations. The dependence of key laser propulsion parameters, including the momentum coupling coefficient and specific impulse, are calculated based on experimental data, and results are compared to existing literature data.

Sinko, John E.; Ichihashi, Katsuhiro; Tsukiyama, Yosuke; Ogita, Naoya; Sakai, Takeharu; Umehara, Noritsugu; Sasoh, Akihiro

2010-05-01

251

Pulsed CO2 laser ablation of graphite and polymers  

NASA Astrophysics Data System (ADS)

Spectroscopic analysis of the emission plumes of graphite, polyimide, polyethylene terepthalate, and polymethylmethacrylate that have been ablated by using a pulsed CO2 laser operating at 10.6 ?m shows the presence of CN and C2, species not previously reported for CO2 laser ablation. The gross dynamics of the luminous plume, which was studied by using a streak camera, compares favorably with predictions from the snowplow model, which also accurately forecasts the time history of the plume expansion for a wide range of background gas pressures and laser fluences. Framing shadowgraphy reveals the onset of laser-supported detonation waves at approximately 50 mbar Ar, thus somewhat limiting the validity of this model.

Wong, K. H.; Tou, T. Y.; Low, K. S.

1998-02-01

252

Ablative thresholds in laser cleaning of substrates from particulates  

NASA Astrophysics Data System (ADS)

`Laser cleaning' thresholds based on the local ablation of substrate material are studied theoretically. Results are compared with the experimental data on the cleaning of silicon wafers from spherical silica particles using laser wavelengths at 248, 532 and 1064 nm. Calculations take into account local enhancement in the laser-light intensity and are based on analytical solutions for the temperature distribution. Influence of vapor atmosphere on cleaning thresholds is studied experimentally and theoretically. Here cleaning is assisted by explosive vaporization of capillary condensed water. A possibility to increase the window for damage-free cleaning by varying the pulse duration and laser wavelength is also discussed.

Arnold, N.; Schrems, G.; Bäuerle, D.

253

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation  

NASA Astrophysics Data System (ADS)

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. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

Peña-Díaz, M.; Ponce, L.; Arronte, M.; Flores, T.

2007-04-01

254

Production of nanoparticles from natural hydroxylapatite by laser ablation  

PubMed Central

Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism.

2011-01-01

255

Comparative study on laser tissue ablation between PV and HPS lasers  

NASA Astrophysics Data System (ADS)

Laser therapy for obstructive benign prostatic hyperplasia (BPH) has gained broad adoption due to effective tissue removal, immediate hemostasis, and minor complications. The aim of this study is to quantitatively compare ablation characteristics of PV (Photoselective Vaporization) and the newly introduced HPS (High Performance System) 532 nm lasers. Bovine prostatic tissues were ablated in vitro, using a custom-made scanning system. Laser-induced volume produced by two lasers was quantified as a function of applied power, fiber working distance (WD), and treatment speed. Given the same power of 80 W and speed of 4 mm/s, HPS created up to 50 % higher tissue ablation volume than PV did. PV induced a rapid decrease of ablation volume when WD increased from 0.5 mm to 3 mm while HPS yielded almost constant tissue removal up to 3 mm for both 80 W and 120 W. As the treatment speed increased, both lasers reached saturation in tissue ablation volume. Lastly, both PV and HPS lasers exhibited approximately 1 mm thick heat affected zone (HAZ) in this study although HPS created twice deeper ablation channels with a depth of up to 4 mm. Due to a smaller beam size and a higher output power, HPS maximized tissue ablation rate with minimal thermal effects to the adjacent tissue. Furthermore, more collimated beam characteristics provides more spatial flexibility and may even help to decrease the rate of fiber degradation associated with thermal damage from debris reattachment to the tip.

Kang, Hyun Wook; Jebens, David; Mitchell, Gerald; Koullick, Ed

2008-03-01

256

Femtosecond laser ablation of aluminum in vacuum and air at high laser intensity  

NASA Astrophysics Data System (ADS)

In this study, the ablation of aluminum by a near-infrared femtosecond laser pulse (800 nm, 100 fs) at different intensity is investigated by a two-dimensional hydrodynamic model. The ablation rates are compared between the cases in vacuum and in air over a wide range of laser power density. It has been reported before that at low (<1013 W/cm2) and moderate laser intensity (1013-1014 W/cm2), two different ablation regimes exist, and the ablation depth per pulse is dependent on the optical penetration depth and electron heat penetration depth, respectively. By considering both collisional and collisionless absorptions, the model in this study predicts the third ablation regime with a much higher ablation rate increase with respect to laser intensity in the high intensity range (>1014 W/cm2) in vacuum, which shows good agreement with the experimental data. This phenomenon is attributed to the change of dominant absorption mechanism from collisional to collisionless absorption. For the case in air, the ablation depth increases slowly with the laser intensity in the high intensity regime, and is much smaller than that in vacuum. It is revealed that this is due to the strong early plasma-laser interaction in air.

Zhao, Xin; Shin, Yung C.

2013-10-01

257

Plasma diagnostics during laser ablation in a cavity  

Microsoft Academic Search

The formation of a laser-induced plasma in a cavity and the effects of a cavity on the ablation process were investigated. Cavities were fabricated in fused silica with equal depths and variable diameters to provide aspect ratios (depth\\/diameter) of 1, 3 and 6. The temperature and electron number density of the pulsed laser-induced plasma in the cavities were determined from

Xianzhong Zeng; Samuel S. Mao; Chunyi Liu; Xianglei Mao; Ralph Greif; Richard E. Russo

2003-01-01

258

Perfluorocarbon compounds: transmitting liquids for infrared laser tissue ablation  

Microsoft Academic Search

One concern during IR-laser ablation of tissue under water is the mechanical injury that may be induced in tissue due to rapid bubble expansion and collapse or due to strong laser-induced pressure waves. The objective of this study was to evaluate the feasibility of using a liquid which is transparent to the IR-region of the spectrum in order to minimize

Martin Frenz; Hans S. Pratisto; Cindy A. Toth; E. Duco Jansen; Hans J. Altermatt; Ashley J. Welch; Heinz P. Weber

1996-01-01

259

Parametric study of CN films deposited by reactive laser ablation  

Microsoft Academic Search

Thin amorphous C-N films were deposited on Si and KBr substrates at room temperature by XeCl laser ablation of graphite in low pressure (0.01 - 2.5 mbar) nitrogen atmosphere. Laser fluences were 3, 6, and 12 J\\/cm2. Scanning electron microscopy, energy dispersion spectroscopy, x-ray diffraction spectroscopy, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy were used to characterize the deposited films,

Armando Luches; A. P. Caricato; Emilia D'Anna; Gilberto Leggieri; Maurizio Martino; Alessio Perrone; G. Barucca; Guiseppe Majni; Paolo Mengucci; Rodica Alexandrescu; Ion N. Mihailescu; Joseph Zemek

1997-01-01

260

Controlled Ablation of Microtubules Using a Picosecond Laser  

Microsoft Academic Search

The use of focused high-intensity light sources for ablative perturbation has been an important technique for cell biological and developmental studies. In targeting subcellular structures many studies have to deal with the inability to target, with certainty, an organelle or large macromolecular complex. Here we demonstrate the ability to selectively target microtubule-based structures with a laser microbeam through the use

E. L. Botvinick; V. Venugopalan; J. V. Shah; L. H. Liaw; M. W. Berns

2004-01-01

261

Influence of deposition parameters on laser ablation deposited amorphous carbon  

Microsoft Academic Search

Thin amorphous carbon films were deposited by KrF laser ablation from graphite and glassy carbon targets at different substrate temperatures with beam power density on the target of 3 × 108 W cm?2. The films were characterized by electrical resistivity, spectroscopic ellipsometry, ultraviolet transmission, visible and infrared spectra and Raman spectroscopy. The influence on film properties of substrate temperature during

J. Bulí?; M. Jelínek; V. Vorlí?ek; D. Chvostová; L. Soukup

1995-01-01

262

Mössbauer Study of Iron Films Produced by Laser Ablation  

Microsoft Academic Search

Iron atoms evaporated by laser ablation were deposited on Al substrates and Si substrates. The iron and alloy (Fe-Al and Fe-Si) films thus formed were evaluated using Mössbauer spectroscopy in order to study their magnetic and chemical properties. Neat iron films (thicker than 50 nm) deposited on Al substrates at 10 K were found to have spin orientations parallel to

Kentarou Namiki; Daisuke Yokoyama; Yasuhiro Yamada

2005-01-01

263

Laser ablation assisted adhesive bonding of automotive structural composites  

SciTech Connect

Laser ablation has been evaluated as a surface pretreatment prior to adhesive bonding. In prior experimental work, it was observed that when adhesively bonded, composite, single lap shear samples fail, the fracture often occurs at either the adhesive/adherend interface or in the resin rich surface layer of the composite. These two areas represent the weakest portion of the joint. Laser ablation pretreatment generates areas where the resin on the composite surface is selectively removed leaving behind exposed reinforcing fibers which are the major load bearing members of the composite. In a subsequent adhesive bonding operation, this allows portions of the fibers to be encapsulated in the adhesive while other portions of the fiber remain in the composite resin. This type of pretreatment permits fibers to bridge and reinforce the interface between adhesive and adherend. A secondary benefit is the removal of surface contaminantes by pyrolysis. Microscopic observation of laser ablated surfaces indicates a prominent, fiber rich area. Results of the mechanical evaluation indicated that the lap shear strength for laser ablated samples was significantly higher than specimens with no pretreatment or with solvent cleaning only, but were slightly lower than specimens that were mechanically roughened and cleaned with solvents prior to bonding.

Boeman, R.G.; Paulauskas, F.L.; Warren, C.D.

1999-07-03

264

Perfluorocarbon compounds: transmitting liquids for infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

One concern during IR-laser ablation of tissue under water is the mechanical injury that may be induced in tissue due to rapid bubble expansion and collapse or due to strong laser-induced pressure waves. The objective of this study was to evaluate the feasibility of using a liquid which is transparent to the IR-region of the spectrum in order to minimize these undesired mechanical side-effects. As transmitting medium perfluorocarbon liquid was used. Free- running Er:YAG and Ho:YAG laser pulses were delivered into the liquid via a 400 micrometers fiber. Bubble formation during the ablation process was recorded with fast flash photography while pressure transients were measured with a needle hydrophone. The effect of the surrounding material (air, water, perfluorooctane) on the tissue response of chicken breast was evaluated in vitro using histology. It was observed that a large bubble (up to 6 mm in diameter) was formed under perfluorooctane driven by the ablation products. This bubble, however, does not generate a pressure wave when collapsing. Although perfluorooctane only shows a weak absorption for infrared radiation, laser-induced thermal lensing in the liquid strongly decreases the radiant exposure and therefore the ablation efficiency.

Frenz, Martin; Pratisto, Hans S.; Toth, Cindy A.; Jansen, E. Duco; Altermatt, Hans J.; Welch, Ashley J.; Weber, Heinz P.

1996-05-01

265

Thermal Simulation of UV Laser Ablation of Polyimide  

Microsoft Academic Search

Our aim is to provide a simulation tool for manufacturing processes that takes the influence of temperature distribution thus the underlying copper pattern and pulse repetition frequency into account. To establish such simulation software a finite element model was set up which is able to describe the thermal processes and ablation induced by laser irradiation of polymers. The etch rate

Peter Gordon; Balint Balogh; Balint Sinkovics

2005-01-01

266

Thermal simulation of UV laser ablation of polyimide  

Microsoft Academic Search

The aim of our research is to provide a simulation tool for manufacturing processes that takes the influence of temperature distribution thus the underlying copper pattern and pulse repetition frequency into account. To establish such simulation software, a finite element model was set up which is able to describe the thermal processes and ablation induced by laser irradiation of polymers.

Péter Gordon; Bálint Balogh; Bálint Sinkovics

2007-01-01

267

Femtosecond laser ablation from dielectric materials: Comparison to arc discharge erosion  

NASA Astrophysics Data System (ADS)

After explosive ablation from sapphire crystals by linearly polarised laser pulses, regular structures are observed on the bottom of the ablation pit. These structures do not comply with conventional ripple patterns. Instead, they more nearly resemble wickerwork, aligned perpendicular to the laser beam polarisation. A similar morphology is obtained by arc discharge erosion at AgCdO electrodes, suggesting that an explosive laser ablation may be characterised by high electric field effects and self organisation in the ablation craters.

Henyk, M.; Vogel, N.; Wolfframm, D.; Tempel, A.; Reif, J.

268

Laser-induced back ablation of aluminum thin films using picosecond laser pulses  

SciTech Connect

A study of laser-induced back ablation of aluminum thin film targets with picosecond laser pulses is reported. Ablated plume edge velocities are studied as a function of film thickness, laser pulse width, and incident laser fluence. Edge velocity results are compared to a model of total transmitted fluence incident at the substrate/film interface. A model including laser-induced avalanche ionization and multiphoton ionization mechanisms in the substrate shows a transmitted fluence limit which is consistent with observed edge velocity limits. {copyright} {ital 1999 American Institute of Physics.}

Bullock, A.B.; Bolton, P.R. [Physics and Space Technology, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)

1999-01-01

269

Near-infrared laser ablation of poly tetrafluoroethylene (Teflon) sensitized by nanoenergetic materials  

SciTech Connect

Laser ablation of Teflon doped with size-selected (30-250 nm) Al nanoparticles is studied. Unlike pure Teflon, which requires a vacuum-ultraviolet or femtosecond excimer laser for ablation, this sensitized Teflon can be ablated with a near-infrared laser. Using 100 ps duration pulses, near-infrared ablation thresholds are lower by about a factor of 10 from excimer ablation of pure Teflon. A mechanism is discussed that involves Teflon decomposition by spherical shock fronts originating at each irradiated nanoparticle. Studies of the distance dependence of this process as a function of particle diameter and oxide layer thickness suggest ways of optimizing the ablation process.

Yang Yanqiang; Wang Shufeng; Sun Zhaoyong; Dlott, Dana D. [School of Chemical Sciences, Box 01-6 CLSL, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States)

2004-08-30

270

Picosecond laser ablation of nickel-based superalloy C263  

NASA Astrophysics Data System (ADS)

Picosecond laser (10.4 ps, 1064 nm) ablation of the nickel-based superalloy C263 is investigated at different pulse repetition rates (5, 10, 20, and 50 kHz). The two ablation regimes corresponding to ablation dominated by the optical penetration depth at low fluences and of the electron thermal diffusion length at high fluences are clearly identified from the change of the surface morphology of single pulse ablated craters (dimples) with fluence. The two corresponding thresholds were measured as F {th(D1)/1}=0.68±0.02 J/cm2 and F {th(D2)/1}=2.64±0.27 J/cm2 from data of the crater diameters D 1,2 versus peak fluence. The surface morphology of macroscopic areas processed with a scanning laser beam at different fluences is characterised by ripples at low fluences. As the fluence increases, randomly distributed areas among the ripples are formed which appear featureless due to melting and joining of the ripples while at high fluences the whole irradiated surface becomes grainy due to melting, splashing of the melt and subsequent resolidification. The throughput of ablation becomes maximal when machining at high pulse repetition rates and with a relatively low fluence, while at the same time the surface roughness is kept low.

Semaltianos, N. G.; Perrie, W.; Cheng, J.; French, P.; Sharp, M.; Dearden, G.; Watkins, K. G.

2010-02-01

271

308-nm excimer laser ablation of human cartilage  

NASA Astrophysics Data System (ADS)

The XeCl excimer laser was investigated as an ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800 micrometers fiber with the laser delivering a range of fluences (40 to 190 mj/mm2) firing at a frequency of 5 Hz. To assess the effect of repetition rate on ablation rate, a set of measurements was made at a constant fluence of 60 mj/mm2, with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage at the maximum fluence tested. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10 - 70 micrometers ).

Prodoehl, John A.; Rhodes, Anthony L.; Meller, Menachem M.; Sherk, Henry H.

1993-07-01

272

Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold  

SciTech Connect

Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}/T{sub tr} of critical to triple-point temperature differs by more than a factor of 4--the values of the ablation threshold energy E{sub abl} normalized to the cohesion energy, {epsilon}{sub abl}=E{sub abl}/E{sub coh}, are surprisingly universal: all are near 0.3 with {+-}30% scattering. The difference in the ratio T{sub c}/T{sub tr} means that for metals the melting threshold {epsilon}{sub m} is low, {epsilon}{sub m}<{epsilon}{sub abl}, while for LJ it is high, {epsilon}{sub m}>{epsilon}{sub abl}. This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in {epsilon}{sub abl}, metals thermomechanically ablate always from the liquid state. This is opposite to LJ materials, which (near threshold) ablate from the solid state. Furthermore, we find that immediately below the ablation threshold, the formation of large voids (cavitation) in the irradiated material leads to a strong temporary expansion on a very slow time scale. This feature is easily distinguished from the acoustic oscillations governing the material response at smaller intensities, on the one hand, and the ablation occurring at larger intensities, on the other hand. This finding allows us to explain the puzzle of huge surface excursions found in experiments at near-threshold laser irradiation.

Upadhyay, Arun K. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Inogamov, Nail A. [Landau Institute for Theoretical Physics, Russian Academy of Science, Kosygina 2, 117940 Moscow (Russian Federation); Rethfeld, Baerbel; Urbassek, Herbert M. [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)

2008-07-15

273

In vitro bioactivity of laser ablation pseudowollastonite coating.  

PubMed

Pseudowollastonite (psW) coatings on titanium alloys substrates were prepared by laser ablation and immersed in simulated body fluid (SBF) for different periods in order to investigate the nucleation and growth of hydroxyapatite (HA)-like formation on their surface. The structure of the coatings before soaking was analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The interfacial reactions product was examined by thin-film XRD, SEM and transmission electron microscopy at low and high resolution level, both fitted with energy-dispersive X-ray spectroscopy. Additional changes in ionic concentration, using inductively couple plasma atomic emission spectroscopy, were determined as well as pH right at the psW-coatings/SBF interface using an ion-sensitive field effect transistor. The solution composition changes, increasing the Ca(2+) and Si(4+) concentration and pH as a function of the soaking time while HPO(4)(2-) decreased. The results obtained showed that the coating surfaces were covered by HA-like, which indicated that the psW-coating possesses good bioactivity and also suggested that the mechanism of HA-like layer formation in SBF was similar to that showed in in vitro test by other silica-based materials. PMID:14741612

De Aza, P N; Fernández-Pradas, J M; Serra, P

2004-05-01

274

A Monte Carlo simulation of laser ablation during the laser pulse: Cl2(s) ablation dynamics for neutral beam etching  

Microsoft Academic Search

Summary form only given. Two requirements for any neutral beam source for etching applications are that the beam be highly directed (that there be little spread to the beam) and that the directed flux of etching precursors be sufficiently high to achieve a reasonable etch rate. Laser ablation of a target material such as frozen Cl2 may meet these requirements.

M. Suzuki; H. Date; P. L. G. Ventzek; Y. Sakai; H. Tagashira; R. J. Faehl; K. Kitamori

1996-01-01

275

Ultraviolet laser ablation of polycarbonate and glass in air  

NASA Astrophysics Data System (ADS)

The fundamental physical processes that follow ultraviolet laser ablation of polycarbonate and borosilicate glass in air have been investigated using photodeflection as a function of the distance from the surface to probe laser. Four features were observed in the data sets for each material. Two of these features correlate well with gas dynamical predictions for the expansion of the shock wave and gas plume. The third feature is consistent with the propagation of the popping sound of the laser ablation event. The final feature, which occurs at very early times and does not shift significantly in time as the surface to probe distance is increased from 0 to greater than 6 mm, has been tentatively ascribed to the ejection of fast electrons. The final significant observation is complete blocking of the probe laser, only observed during borosilicate ablation, which is attributed to scattering of the probe laser light by macroscopic SiOx particles that grow in the final stages of plume expansion and cooling.

Bormotova, T. A.; Blumenthal, R.

2009-02-01

276

Laser ablation solid sampling: vertical spatial emission intensity profiles in inductively coupled plasma  

Microsoft Academic Search

Spectral emission intensity in the inductively coupled plasma (ICP) was measured versus height above the load coil during laser ablation solid-sample introduction. The laser-beam pulse width, power density, and wavelength, and the sample composition are know to effect the particle size distribution of the ablated mass. Ceramic and metal samples were ablated using nanosecond and picosecond pulses, and provided similar

Manuel Caetano; Xianglei Mao; Richard E. Russo

1996-01-01

277

Prediction of the ablation effect of ultrapulsed CO2 laser systems in clinical procedures  

Microsoft Academic Search

Despite the superficial penetration of the light, the continuous wave (cw) CO2 laser may induce a relatively large area of thermal damage in tissue next to the ablation crater. Ultra-pulsed laser systems, however, deliver pulse energies above the ablation threshold for tissue within a few hundred microsecond(s) , which instantly vaporize tissue. Since cw ablation models cannot be applied on

Matthijs C. Grimbergen; Rudolf M. Verdaasdonk; Christiaan F. van Swol

1997-01-01

278

Shadowgraphy of pulsed CO2 laser ablation of polymers  

NASA Astrophysics Data System (ADS)

Heavy plume expansions in air, helium and argon produced by pulsed CO2 laser ablations of poly(methyl methacrylate) (PMMA) and polyimide (PI) were imaged by shadowgraphy. The PMMA was melted at 1 2 mm depth beneath the surface followed by an outward expulsion of heavy plumes. A shock front was formed which detached from the first plume after several microseconds. A second, mushroom-shaped plume and a narrow ejection were also observed. In contrast, the mushroom-shaped plume structure was absent in PI ablation, but it was in the form of a single blob, which collapsed back to the target.

Siew, W. O.; Tou, T. Y.; Wong, K. H.

2005-07-01

279

Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments  

NASA Astrophysics Data System (ADS)

This paper describes a setup for thrust measurement in ablative laser propulsion experiments, based on a simple ballistic pendulum associated to an imaging system, which is being assembled at IEAv. A light aluminium pendulum holding samples is placed inside a 100 liters vacuum chamber with two optical windows: the first (in ZnSe) for the laser beam and the second (in fused quartz) for the pendulum visualization. A TEA-CO2 laser beam is focused to the samples providing ablation and transferring linear moment to the pendulum as a whole. A CCD video camera captures the oscillatory movement of the pendulum and the its trajectory is obtained by image processing. By fitting the trajectory of the pendulum to a dumped sinusoidal curve is possible to obtain the amplitude of the movement which is directly related to the momentum transfered to the sample.

Brazolin, H.; Rodrigues, N. A. S.; Minucci, M. A. S.

2008-04-01

280

Ablation of aluminum thin films by ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

In this study, various results are presented for laser ablation experiments on aluminum and silicon, made in ambient air by means of subpicosecond laser pulses. These results include threshold fluences for plasma formation and for the appearance of various spectral lines, and the single shot fluence required to remove aluminum layers of various specific thicknesses (ranging from 10 to 500 nm) deposited on a silicon substrate. The threshold fluence for plasma formation is of the order of 0.1 J/cm2. Threshold fluences for the appearance of the spectral lines considered vary from 0.1 to about 5 J/cm2. Finally, our results suggest that for high fluences, even for ultrashort laser pulses, the ablation depth is essentially determined by a long-range process, such as thermal conduction in the solid, rather than by the short range optical depth.

Le Drogoff, B.; Vidal, F.; von Kaenel, Y.; Chaker, M.; Johnston, T. W.; Laville, S.; Sabsabi, M.; Margot, J.

2001-06-01

281

Ablation of aluminum thin films by ultrashort laser pulses  

SciTech Connect

In this study, various results are presented for laser ablation experiments on aluminum and silicon, made in ambient air by means of subpicosecond laser pulses. These results include threshold fluences for plasma formation and for the appearance of various spectral lines, and the single shot fluence required to remove aluminum layers of various specific thicknesses (ranging from 10 to 500 nm) deposited on a silicon substrate. The threshold fluence for plasma formation is of the order of 0.1 J/cm2. Threshold fluences for the appearance of the spectral lines considered vary from 0.1 to about 5 J/cm2. Finally, our results suggest that for high fluences, even for ultrashort laser pulses, the ablation depth is essentially determined by a long-range process, such as thermal conduction in the solid, rather than by the short range optical depth. {copyright} 2001 American Institute of Physics.

Le Drogoff, B.; Vidal, F.; von Kaenel, Y.; Chaker, M.; Johnston, T. W.; Laville, S.; Sabsabi, M.; Margot, J.

2001-06-15

282

Ultrafast laser ablation of metal films on flexible substrates  

NASA Astrophysics Data System (ADS)

For the development of organic electronics on flexible substrates, we study the potentialities of direct laser patterning of conductive films deposited on plastic foils. The materials under study are silver and platinum films (100-nm thick) deposited on Kapton® substrates. The experiments are done using a laser source operating at 1030 nm, 500 fs, under different irradiation conditions: single and multiple pulses at various frequencies. The laser ablation thresholds are measured and the ablation morphologies are analyzed with scanning electron microscopy. The results of these investigations show that photomechanical effects lead to delamination of the film and that depending of the irradiation conditions, incubation or heat accumulation effects can occur. The experimental results are compared to simulations based on the two-temperature model. Particularly we study the heat accumulation effects that can occur in the case of multiple pulses and that are detrimental for plastic substrates.

Gallais, L.; Bergeret, E.; Wang, B.; Guerin, M.; Bènevent, E.

2013-08-01

283

Pillars formed by laser ablation and modified by wet etching  

NASA Astrophysics Data System (ADS)

Studies on surface texturing by chemically enhanced laser ablation in a variety of materials, particularly silicon and germanium are reported. The materials are exposed either to femtosecond or nanosecond laser irradiation in a variety of vacuum or gaseous environments including air, He, sulfur hexafluoride (SF6) or hydrogen chloride (HCl). The dynamics of pillar formation are elucidated and it is shown that the mechanisms are very different in these two pulse length regimes. Surface texturing responds to the combined effects of laser assisted chemical etching and laser ablation. Various processing steps either before or after laser irradiation allow us to modify the nature of the pillars that are formed. In this way we can make ordered arrays that extend over ?1 cm2 in just a few minutes of laser exposure. Post-laser processing wet etching can produce Si pillars that are over 50 ?m long with tips that are only 10 nm across as well as macroporous silicon with crystallographically defined pores. A process we call solidification driven extrusion creates nanoscale spikes atop the pillars under certain circumstances - a process that is more prevalent for Ge than Si. Pillar-covered surfaces of Si and Ge are black; that is, they exhibit very low reflectivity. For Si this low reflectivity extends to wavelengths far below the band gap raising the possibility that we may be able to make other transparent materials highly absorptive by laser texturing.

Kolasinski, Kurt W.; Dudley, Margaret E.; Nayak, Barada K.; Gupta, Mool C.

2007-05-01

284

Proton emission from a laser ion source  

NASA Astrophysics Data System (ADS)

At intensities of the order of 1010 W/cm2, ns pulsed lasers can be employed to ablate solid bulk targets in order to produce high emission of ions at different charge state and kinetic energy. A special interest is devoted to the production of protons with controllable energy and current from a roto-translating target irradiated in repetition rate at 1-10 Hz by a Nd:Yag pulsed laser beam. Different hydrogenated targets based on polymers and hydrates were irradiated in high vacuum. Special nanostrucutres can be embedded in the polymers in order to modify the laser absorption properties and the amount of protons to be accelerated in the plasma. For example, carbon nanotubes may increase the laser absorption and the hydrogen absorption to generate high proton yields from the plasma. Metallic nanostrucutres may increase the electron density of the plasma and the kinetic energy of the accelerated protons. Ion collectors, ion energy analyzer, and mass spectrometers, used in time-of-flight configuration, were employed to characterize the ion beam properties. A comparison with traditional proton ion source is presented and discussed.

Torrisi, L.; Cavallaro, S.; Cutroneo, M.; Margarone, D.; Gammino, S.

2012-02-01

285

Proton emission from a laser ion source  

SciTech Connect

At intensities of the order of 10{sup 10} W/cm{sup 2}, ns pulsed lasers can be employed to ablate solid bulk targets in order to produce high emission of ions at different charge state and kinetic energy. A special interest is devoted to the production of protons with controllable energy and current from a roto-translating target irradiated in repetition rate at 1-10 Hz by a Nd:Yag pulsed laser beam. Different hydrogenated targets based on polymers and hydrates were irradiated in high vacuum. Special nanostrucutres can be embedded in the polymers in order to modify the laser absorption properties and the amount of protons to be accelerated in the plasma. For example, carbon nanotubes may increase the laser absorption and the hydrogen absorption to generate high proton yields from the plasma. Metallic nanostrucutres may increase the electron density of the plasma and the kinetic energy of the accelerated protons. Ion collectors, ion energy analyzer, and mass spectrometers, used in time-of-flight configuration, were employed to characterize the ion beam properties. A comparison with traditional proton ion source is presented and discussed.

Torrisi, L. [INFN-LNS Via S. Sofia 44, 95123 Catania (Italy); Dip.to di Fisica, Universita di Messina, V.le F.S. D'Alcontres 31, 98166 S. Agata, Messina (Italy); Cavallaro, S.; Gammino, S. [INFN-LNS Via S. Sofia 44, 95123 Catania (Italy); Cutroneo, M. [Dip.to di Fisica, Universita di Messina, V.le F.S. D'Alcontres 31, 98166 S. Agata, Messina (Italy); Margarone, D. [Institute of Physics, ASCR, v.v.i., 182 21 Prague 8 (Czech Republic)

2012-02-15

286

A rare complication of endovenous laser ablation: intravascular laser catheter breakage.  

PubMed

During endovenous laser ablation, which is performed as an alternative to surgery for the treatment of superficial venous insufficiency of lower extremity and associated varicose veins, it was realised that the distal end of the catheter protecting the fibre sheared off; the retained catheter fragment in the saphenous vein was removed by a mini incision. Herein, we aim to present a rare complication of endovenous laser ablation. PMID:23513025

Bozoglan, Orhan; Mese, Bulent; Inci, Mehmet Fatih; Eroglu, Erdinc

2013-03-18

287

Microsecond laser ablation of thrombus and gelatin under clear liquids: Contact versus noncontact  

Microsoft Academic Search

Laser thrombolysis is a procedure for removing blood clots in occluded arteries using pulsed laser energy. The laser light is delivered through an optical fiber to the thrombus. The ablation process is profoundly affected by whether the optical fiber tip is inside a catheter or is in contact with the thrombus. This study measured ablation efficiency of 1-?s laser pulses

HanQun Shangguan; Lee W. Casperson; Scott A. Prahl

1996-01-01

288

Laser ablation of organic materials for discrimination of bacteria in an inorganic background  

Microsoft Academic Search

We demonstrate in this paper that laser ablation allows efficient analysis of organic and biological materials. Such analysis is based on laser-induced breakdown spectroscopy (LIBS) which consists in the detection of the optical emission from the plasma induced by a high intensity laser pulse focused on the sample surface. The optimization of the ablation regime in terms of laser parameters

Matthieu Baudelet; Myriam Boueri; Jin Yu; Xianglei Mao; Samuel S. Mao; Richard Russo

2009-01-01

289

Mechanism of dye-enhanced pulsed laser ablation of hard tissues: implications for dentistry  

Microsoft Academic Search

Alexandrite laser ablation of enamel enhanced by an indocyanine green dye was studied. A microjet system was employed to deliver precisely measured small amounts of absorbing dye solution to the site of irradiation. A sequence of physical phenomena involved in dye-enhanced laser ablation of dental enamel was revealed when laser pulse profiles were compared with the profiles of laser-induced pressure,

Rinat Esenaliev; Alexander Oraevsky; Sohi Rastegar; Chris Frederickson; Massoud Motamedi

1996-01-01

290

Saturation effects in femtosecond laser ablation of silicon-on-insulator  

NASA Astrophysics Data System (ADS)

We report a surface morphology study on single-shot submicron features fabricated on silicon on insulator by tightly focused femtosecond laser pulses. In the regime just below single-shot ablation threshold nano-tips are formed, whereas in the regime just above single-shot ablation threshold, a saturation in the ablation depth is found. We attribute this saturation by secondary laser absorption in the laser-induced plasma. In this regime, we find excellent agreement between the measured depths and a simple numerical model. When the laser fluence is further increased, a sharp increase in ablation depth is observed accompanied by a roughening of the ablated hole.

Zhang, Hao; van Oosten, D.; Krol, D. M.; Dijkhuis, J. I.

2011-12-01

291

Thermal-mechanical modeling of laser ablation hybrid machining  

NASA Astrophysics Data System (ADS)

Hard, brittle and wear-resistant materials like ceramics pose a problem when being machined using conventional machining processes. Machining ceramics even with a diamond cutting tool is very difficult and costly. Near net-shape processes, like laser evaporation, produce micro-cracks that require extra finishing. Thus it is anticipated that ceramic machining will have to continue to be explored with new-sprung techniques before ceramic materials become commonplace. This numerical investigation results from the numerical simulations of the thermal and mechanical modeling of simultaneous material removal from hard-to-machine materials using both laser ablation and conventional tool cutting utilizing the finite element method. The model is formulated using a two dimensional, planar, computational domain. The process simulation acronymed, LAHM (Laser Ablation Hybrid Machining), uses laser energy for two purposes. The first purpose is to remove the material by ablation. The second purpose is to heat the unremoved material that lies below the ablated material in order to ``soften'' it. The softened material is then simultaneously removed by conventional machining processes. The complete solution determines the temperature distribution and stress contours within the material and tracks the moving boundary that occurs due to material ablation. The temperature distribution is used to determine the distance below the phase change surface where sufficient ``softening'' has occurred, so that a cutting tool may be used to remove additional material. The model incorporated for tracking the ablative surface does not assume an isothermal melt phase (e.g. Stefan problem) for laser ablation. Both surface absorption and volume absorption of laser energy as function of depth have been considered in the models. LAHM, from the thermal and mechanical point of view is a complex machining process involving large deformations at high strain rates, thermal effects of the laser, removal of materials and contact between workpiece and tool. The theoretical formulation associated with LAHM for solving the thermal-mechanical problem using the finite element method is presented. The thermal formulation is incorporated in the user defined subroutines called by ABAQUS/Standard. The mechanical portion is modeled using ABAQUS/Explicit's general capabilities of modeling interactions involving contact and separation. The results obtained from the FEA simulations showed that the cutting force decrease considerably in both LAEM Surface Absorption (LARM-SA) and LAHM volume absorption (LAHM-VA) models relative to LAM model. It was observed that the HAZ can be expanded or narrowed depending on the laser speed and power. The cutting force is minimal at the last extent of the HAZ. In both the models the laser ablates material thus reducing material stiffness as well as relaxing the thermal stress. The stress values obtained showed compressive yield stress just below the ablated surface and chip. The failure occurs by conventional cutting where tensile stress exceeds the tensile strength of the material at that temperature. In this hybrid machining process the advantages of both the individual machining processes were realized.

Matin, Mohammad Kaiser

2001-08-01

292

Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold  

Microsoft Academic Search

Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials---e.g., for aluminum versus LJ the ratio Tc\\/Ttr of critical to triple-point temperature

Arun K. Upadhyay; Nail A. Inogamov; Bärbel Rethfeld; Herbert M. Urbassek

2008-01-01

293

Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold  

Microsoft Academic Search

Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}\\/T{sub tr} of critical to

Arun K. Upadhyay; Nail A. Inogamov; Baerbel Rethfeld; Herbert M. Urbassek

2008-01-01

294

Modeling of dynamical processes in laser ablation  

SciTech Connect

Various physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed-laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume, plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms, hydrodynamic and collisional descriptions of plume transport, and molecular dynamics models of the interaction of plume particles with the deposition substrate.

Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

1995-12-31

295

Noble metal nanoparticles produced by nanosecond laser ablation  

NASA Astrophysics Data System (ADS)

Silver and gold thin films were deposited by pulsed laser ablation in a controlled Ar atmosphere at pressures between 10 and 100 Pa. Different morphologies, ranging from isolated nanoparticle arrays up to nanostructured thin films were observed. Fast imaging of the plasma allowed deducing the expansion dynamics of the ablated plume. Plasma velocity and volume were used together with the measured average ablated mass per pulse as input parameters in a model to estimate the average size of nanoparticles grown in the plume. The nanoparticle size is expected to decrease from 4 nm down to 1 nm with decreasing Ar pressure between 100 and 10 Pa: this was confirmed by transmission electron micrographs which indicate a reduced dispersion of particle size over narrow size ranges. The production of substrates for surface enhanced Raman scattering whose performances critically depend on nanoparticle size, shape, and structure is discussed.

Ossi, P. M.; Neri, F.; Santo, N.; Trusso, S.

2011-09-01

296

An Electron Emission Effect on Dynamics of Laser Ablation  

SciTech Connect

The paper deals with the effect of electron emission on a heat transfer in the area of a plasma critical density (near plasma-solid surface boundary). As is known, experimental data show the limitation of electron thermal conductivity in the mentioned area. In the laser fusion research just the limitation of the heat transfer at target irradiation with long-wave lasers has made application of CO2-lasers unreasonable in spite of their high efficiency. On other hand, as to the applied tasks of laser ablation (e.g. in launching small-scale satellites) the aspect of the CO2-lasers application is being widely discussed. In the paper the mentioned limitation is explained on the basis of classical representations. It is marked, that the heat transfer limitations arise from the conditions of preserving plasma quasi-neutrality at the absorption area boundary where the electron density is close to critical one for the given laser wavelength. Possible mechanisms of the electron emission in the mode of the laser ablation are discussed.

Nastoyashchii, A. F. [RF SRC 'Troitsk Institute for Innovation and Fusion Research', TRINITI Troitsk 142190 (Russian Federation)

2004-03-30

297

A laser ablation electron impact ionization time-of-flight mass spectrometer for analysis of condensed materials  

NASA Astrophysics Data System (ADS)

Laser desorption/ionization (LDI) mass spectrometry suffers from poor reproducibility and a strong bias in representing the chemical composition of the sample in the mass spectra. In regard to develop laser mass spectrometry towards a quantitative analysis technique desorption and ionization processes should be separated. Here we describe a time-of-flight mass spectrometer (TOF-MS) with laser ablation and subsequent electron impact ionization (LA-EI-MS). Sample material is ablated by an Nd-YAG laser pulse (?=355 nm, E=0.5-35 mJ, ?=9 ns), which produces ions and neutrals in the ablation plume. After expansion, parts of the plume enter the EI ion source where neutrals are ionized by electron impact (Eel=70 eV). Ions are extracted from the ion source into the flight tube of the TOF-MS by applying a pulsed repeller potential. Depending on delay times between laser pulse and repeller pulse either neutrals or ions emitted from the sample were analyzed. Different mass spectra of the same sample are obtained in these two analyzing modes under the same irradiation conditions. With a relative standard deviation of 10% to 15%, reproducibility of mass spectra is significantly better in LA-EI-MS than in LDI-MS.

Drewnick, F.; Wieser, P. H.

2002-08-01

298

Excimer Laser Ablation Process of Different Metals  

Microsoft Academic Search

Excimer laser is able to irradiate ultraviolet rays with ultra short pulse width, and the peak power density is very high, i.e. ~109 W\\/cm2. In laser processing of polymers, photochemical reaction is occurred usually, and it is possible to remove the polymer without heat generation. The process is called as \\

M. Kutsuna; T. Ikeda; A. Tsuboi

299

Role of Optical Coherence Tomography on Corneal Surface Laser Ablation  

PubMed Central

This paper focuses on reviewing the roles of optical coherence tomography (OCT) on corneal surface laser ablation procedures. OCT is an optical imaging modality that uses low-coherence interferometry to provide noninvasive cross-sectional imaging of tissue microstructure in vivo. There are two types of OCTs, each with transverse and axial spatial resolutions of a few micrometers: the time-domain and the fourier-domain OCTs. Both have been increasingly used by refractive surgeons and have specific advantages. Which of the current imaging instruments is a better choice depends on the specific application. In laser in situ keratomileusis (LASIK) and in excimer laser phototherapeutic keratectomy (PTK), OCT can be used to assess corneal characteristics and guide treatment decisions. OCT accurately measures central corneal thickness, evaluates the regularity of LASIK flaps, and quantifies flap and residual stromal bed thickness. When evaluating the ablation depth accuracy by subtracting preoperative from postoperative measurements, OCT pachymetry correlates well with laser ablation settings. In addition, OCT can be used to provide precise information on the morphology and depth of corneal pathologic abnormalities, such as corneal degenerations, dystrophies, and opacities, correlating with histopathologic findings.

Ventura, Bruna V.; Moraes, Haroldo V.; Kara-Junior, Newton; Santhiago, Marcony R.

2012-01-01

300

Excimer laser surface ablation: a review of recent literature.  

PubMed

The aim was to review the recently published literature on excimer laser surface ablation procedures, including photorefractive keratectomy (PRK), laser sub-epithelial keratomileusis (LASEK), microkeratome-assisted PRK (epi-LASIK) and trans-epithelial (laser-assisted) PRK, to help elucidate where and how surface ablation may best fit into current refractive surgical practice. The emphasis was on publications within the last three years and included systemic reviews, meta-analyses and randomised controlled trials. Where such evidence did not exist, selective large series cohort studies, case-controlled studies and case series with follow-up preferably greater than six months were examined and included. Refractive and visual outcomes are excellent and comparable to those after LASIK even in complex cases after previous corneal surgery. Indeed, surface ablation combined with corneal collagen cross-linking may be used in selected eyes with biomechanical instability, where LASIK is contraindicated. In addition, there is evidence to suggest that there may be less induction of higher order aberrations with surface techniques. Long-term stability and safety appear to be extremely satisfactory. The literature supports the use of modern excimer laser surface treatments, with outcomes comparable to those after LASIK and evidence of less induction of higher-order aberrations. Follow-up studies at 10 to 20 years indicate excellent stability and safety. PMID:23656608

O'Brart, David Ps

2013-05-01

301

Ablation plasma ion implantation experiments: Measurement of Fe implantation into Si  

SciTech Connect

Experiments have been performed demonstrating the feasibility of direct implantation of laser-ablated metal ions into a substrate. Initial experiments implanted iron ions into silicon substrates at pulsed, bias voltages up to negative 10 kV. Implantation of Fe ions into Si was confirmed by cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy. The 7.6 nm depth of damage layers below the Si surface is slightly less than predicted by code calculations for a maximum, effective ion energy of about 8 keV. The ion depth of penetration is limited by the overlying Fe film as well as the slow rise and fall of the voltage. {copyright} 2001 American Institute of Physics.

Qi, B.; Gilgenbach, R. M.; Lau, Y. Y.; Johnston, M. D.; Lian, J.; Wang, L. M.; Doll, G. L.; Lazarides, A.

2001-06-11

302

Simulation of cluster formation in laser-ablated silicon plumes  

SciTech Connect

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 cluster size is obtained by incorporating diffusion of ambient gas into an adiabatically expanding plume. Various rate constants of clustering reactions are calculated using collision rate and transition state theory. We have used the model to simulate the spatial and temporal extents of silicon nanoparticle formation in laser-ablated silicon plume generated using 248- and 532-nm irradiation in ambient atmosphere of argon. The model predicts the onset time of 3 ms with 248 nm and 1.0 Torr of argon and 2.0, 1.2, and 0.6 ms with 532-nm irradiation and argon background at 2, 5, and 10 Torr, respectively, for 1-nm clusters of silicon. The concentration of clusters decreases with an increase in distance from the target surface. The onset time dependence on ambient pressure follows a simple relation of the form {l_brace}{tau}{sub onset}{proportional_to}(1/P{sub ambient}){sup 0.91}{r_brace}. The reasonable agreement of simulated results with experimental observations implies that the model is adequate to simulate Si cluster formation in the ablation plume.

Franklin, Sushmita R.; Thareja, R.K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 Uttar Pradesh (India)

2005-06-15

303

Optoacoustic monitoring of cutting and heating processes during laser ablation  

NASA Astrophysics Data System (ADS)

Laser-tissue interaction during laser surgery can be classified into two biophysical processes: tissue removal in the focal zone of the laser beam and heating in the surrounding tissue. In order to ensure a precise cut and minimal collateral thermal damage, the surgeon has to control several parameters, such as power, repetition rate and fiber movement velocity. In this study we propose utilizing optoacoustics for providing the necessary real-time feedback of cutting and heating processes. A single Q-switched Nd-YAG laser (532nm, 4 KHz, 18 W, pulse duration 7.6ns) was used for ablation and generation of optoacoustic signals in fresh bovine tissue samples. Both shockwaves, generated due to tissue removal, as well as normal optoacoustic responses from the surrounding tissue were detected using a single 10MHz piezoelectric transducer. It has been observed that rapid reduction in the shockwave amplitude occurs as more material is being removed from the focal zone, indicating decrease in cutting efficiency of the laser beam, whereas gradual decrease in the optoacoustic signal likely corresponds to coagulation around the ablation crater. Further heating of surrounding tissue leads to carbonization accompanied by a significant shift of spectral components of the optoacoustic signal. Our results hold promise for real-time monitoring of cutting efficiency and collateral thermal damage during laser surgery.

Bay, Erwin; Douplik, Alexandre; Razansky, Daniel

2013-03-01

304

Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite  

SciTech Connect

The optical emission from electronically excited C species in the ablation plume following the short (ns) and ultrashort (fs) UV pulsed laser ablation of graphite is studied. Wavelength, time and spatially resolved imaging of the plume, in background pressures of inert gases such as argon and helium, is performed. Analysis of images of optical emission from C{sup +}* ions and C{sub 2}* radicals, yielded estimates of the apparent velocity of emitting species, which appear to arise both from the initial ablation event and, in the presence of background gas, mainly from impact excitation. At elevated background pressures of argon (P{sub Ar}), the formation and propagation of a shock wave is observed for ns pulses, whereas for fs pulses, the propagation of two shock waves is observed. During fs ablation, the first shock wave we associate with an initial burst of highly energetic/electronically excited ablated components, indicative of an enhanced fraction of non-thermal ejection mechanisms when compared with ns ablation. The second shock wave we associate with subsequently ejected, slower moving, material. Concurrent with the plume dynamics investigations, nanostructured amorphous carbon materials were deposited by collecting the ablated material. By varying P{sub Ar} from 5 to 340 mTorr, the film morphology could be changed from mirror smooth, through a rough nanostructured phase and, at the highest background pressures for ns pulses, to a low density cluster-assembled material. The evident correlations between the film structure, the mean velocities of the emitting C species, and their respective dependences upon P{sub Ar} are discussed for both pulse durations. In addition, we comment on the effect of observed initial plume dynamics on the subsequent C cluster formation in the expanding plume.

Henley, S.J.; Carey, J.D.; Silva, S.R.P.; Fuge, G.M.; Ashfold, M.N.R.; Anglos, D. [Nano-Electronics Centre, Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, GU2 7XH (United Kingdom); School of Chemistry, University of Bristol, Bristol, BS8 1TS (United Kingdom); Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, P.O. Box 1527, GR-711 10 Heraklion (Greece)

2005-11-15

305

Tissue ablation via optical fibre delivery of UV laser radiation  

NASA Astrophysics Data System (ADS)

We report the use of an ultraviolet (UV) laser and optical fibre arrangement capable of precise and controllable tissue ablation. The 5th (213nm) and 4th (266nm) harmonics of a Nd:YAG laser were launched into optical fibres using a hollow glass taper to concentrate the beam. Standard and modified silica/silica optical fibres were used, all commercially available. The available energy and fluence, as a function of optical fibre length, were evaluated and maximised. Single 5ns pulses were used to ablate both fresh porcine retina and in vivo rat trabecular meshwork. Fluences of 0.4 to 4.0 J/cm2 of 266nm and 0.2 to 1.0 J/cm2 of 213nm were used respectively. Thus demonstrating the potential use of this system for intraocular surgical applications.

Miller, Joseph; Yu, Xiaobo; Yu, Paula K.; Cringle, Stephen J.; Yu, Dao-Yi

2008-06-01

306

Ablation laser femtoseconde pour le dépôt de DLC  

NASA Astrophysics Data System (ADS)

Des films de Diamond-Like Carbon (DLC) ont été déposés, sous vide poussé, par ablation d'une cible de graphite avec un laser Ti : saphir (durée d'impulsion 150 fs, fréquence de répétition 1 kHz, énergie par impulsion 1,5 mJ, longueur d'onde 800 nm) sur substrat standard. Les propriétés de ces couches (structure, adhérence, propriétés nanomécaniques) ont été caractérisées, en fonction des conditions d'élaboration. La caractérisation par spectroscopie Raman de la structure des dépôts obtenus a révélé la présence de diamant nanocristallin au sein d'une matrice amorphe. Le taux d'hybridation sp^3 des couches, déterminé à partir des spectres obtenus par XANES (X-ray Absorption Near Edge Speciroscopy), est voisin de 70 %. Ces différents résultats sont corrélés avec la caractérisation par imagerie résolue en temps du panache plasma créé par ablation laser femtoseconde.

Loir, A.-S.; Garrelie, F.; Donnet, C.; Goutaland, F.; Belin, M.; Subtil, J.-L.; Le Harzic, R.; Rogemond, F.; Ouerdane, Y.; Laporte, P.

2003-06-01

307

Laser-ablation-assisted microparticle acceleration for drug delivery  

NASA Astrophysics Data System (ADS)

Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected to laser ablation on its backface such that a shock wave propagates through the foil. Due to shock wave loading, the surface of the foil containing microparticles is accelerated to very high speeds, ejecting the deposited particles at hypersonic speeds. The ejected particles have sufficient momentum to penetrate soft body tissues, and the penetration depth observed is sufficient for most of the pharmacological treatments. We have tried delivering 1 ?m tungsten particles into gelatin models that represent soft tissues, and liver tissues of an experimental rat. Sufficient penetration depths have been observed in these experiments with minimum target damage.

Menezes, V.; Takayama, K.; Ohki, T.; Gopalan, J.

2005-10-01

308

Laser ablated coatings on ceramic fibers for ceramic matrix composites  

Microsoft Academic Search

The newly developed pulsed excimer laser ablation (PELA) thin film coating technique was applied to coating ceramic fibers for ceramic matrix composite applications. The feasibility of this application was demonstrated in the coating of two of the most popular monofilaments, SiC (SCS-0) and sapphire. Several materials, such as graphite, SiC and enstatite (MgSiO3) were used as coating targets. Single-layer or

Chao M. Huang; Youren Xu; Fulin Xiong; Avigdor Zangvil; Waltraud M. Kriven

1995-01-01

309

In vitro bioactivity of laser ablation pseudowollastonite coating  

Microsoft Academic Search

Pseudowollastonite (psW) coatings on titanium alloys substrates were prepared by laser ablation and immersed in simulated body fluid (SBF) for different periods in order to investigate the nucleation and growth of hydroxyapatite (HA)-like formation on their surface.The structure of the coatings before soaking was analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The interfacial reactions product was examined

P. N. De Aza; J. M. Fernández-Pradas; P. Serra

2004-01-01

310

Laser reactive ablation deposition of carbon nitride thin films  

Microsoft Academic Search

Thin amorphous C-N films were deposited on silicon substrates at room temperature by XeCl laser ablation of graphite in low pressure nitrogen and ammonia atmospheres. The deposition rates decrease with increasing ambient pressure. Films deposited in NH3 are thinner than films deposited in N2 at the same ambient pressure, their N\\/C atomic ratios are higher, but they present a lower

Armando Luches; A. P. Caricato; Gilberto Leggieri; Maurizio Martino; Alessio Perrone; G. Barucca; Paolo Mengucci; Joseph Zemek

1996-01-01

311

Update On CO{sub 2} Laser Ablation Of Polyoxymethylene At 101 kPa  

SciTech Connect

Recent work has brought about a renewed interest in CO{sub 2} laser ablation studies of polyoxymethylene, due to its potential as a test target for enhancing modern understanding of the laser ablation process. In this paper, new results taken in air at atmosphere pressure are reported, including data measured at institutions in Germany and Japan, which increase the body of literature data on CO{sub 2} laser ablation of polyoxymethylene. The results are discussed in terms of aerospace parameters such as the momentum coupling coefficient and specific impulse, and are compared to a previous literature study. The threshold fluence is specified for ablation of polyoxymethylene by CO{sub 2} laser radiation. Fluences higher (and lower) than previously tested for CO{sub 2} laser ablation were studied herein, and record specific impulse values for CO{sub 2} laser ablation of flat polyoxymethylene are also reported here.

Sinko, John E. [Micro-Nano Global Center of Excellence, Nagoya University, Nagoya, 464-8603 (Japan); Scharring, Stefan; Eckel, Hans-Albert [Studies and Concepts Group, German Aerospace Center (DLR), D-70569 Stuttgart, Pfaffenwaldring 38-40 (Germany); Ogita, Naoya; Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Nagoya, 464-8603 (Japan); Roeser, Hans-Peter [Institute of Space Systems, University of Stuttgart, D-70569 Stuttgart, Pfaffenwaldring 31 (Germany)

2010-10-08

312

Energy deposition and shock wave propagation during pulsed laser ablation in fused silica cavities  

Microsoft Academic Search

Propagation of the shock wave generated during pulsed laser ablation in cavities was measured using laser shadowgraph imaging and compared with laser ablation on a flat surface. The cavities were fabricated in fused silica with the same diameter and variable depths to provide aspect ratios (depth\\/diameter) of 3 and 6. It was found that outside the cavity, after ~30 ns

Xianzhong Zeng; Xianglei Mao; Sy-Bor Wen; Ralph Greif; Richard E. Russo

2004-01-01

313

Theoretical determination of the ablation rate of metals in multiple-nanosecond laser pulses irradiation regime  

Microsoft Academic Search

A detailed understanding of the physical determinants of the ablation rate in multiple nanosecond laser pulses regime is of key importance for technological applications such as patterning and pulsed-laser deposition. Here, theoretical modeling is employed to investigate the ablation of thick metallic plates by intense, multiple nanosecond laser pulses. A new photo-thermal model is proposed, in which the complex phenomena

Mihai Stafe; Constantin Negutu; Ion M. Popescu

2007-01-01

314

Experimental and theoretical investigations of femtosecond laser ablation of aluminum in vacuum  

SciTech Connect

We used time-gated optical emission spectroscopy to investigate the characteristics of aluminum plumes and their vacuum expansion after femtosecond laser ablation at different fluences. The prominent feature is the presence of two main classes of species in the plume: very fast Al atoms and ions preceding the plume bulk essentially constituted of much slower Al nanoparticles expanding with a ten times smaller average velocity. Atomic force microscopy of deposited Al nanoparticles evidenced an average size of about 10 nm with a pretty narrow size distribution. These results and the peculiar feature of nanoparticle formation during femtosecond laser irradiation of matter were very satisfactorily interpreted and reproduced by molecular-dynamics simulation of the process. Finally, the analysis of the dependence on laser fluence of the ablation process showed an initial logarithmic increase of ablation yield, up to about 500 mJ/cm{sup 2}, followed by a sudden and very steep increase at higher fluences. According to our numerical calculations, this latter feature can be ascribed to the increase of the overheated material volume due to electron heat diffusion.

Amoruso, S.; Bruzzese, R.; Vitiello, M.; Nedialkov, N.N.; Atanasov, P.A. [Coherentia-Istituto Nazionale per la Fisica della Materia (INFM) and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, I-80126 Naples (Italy); Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsaridradsko shose Boulevard, Sofia 1784 (Bulgaria)

2005-08-15

315

Micro-optic fabrication using laser ablation process  

NASA Astrophysics Data System (ADS)

The feasibility of laser ablation in micro-machining of 3D structure of MEMS (Micro Electro Mechanical Systems) parts, specifically micro optics was studied in this paper. The micro-machining characteristics of polymer such as etching rate vs. energy fluence, number of pulse are investigated experimentally. The threshold energy density of polyurethane is about 30 mJ/cm2 and ablated depth per pulse can be precisely controlled in the range of 0.1-0.8(mu) M by the attenuation of energy fluence. By mask moving technique, the micro prism, cylindrical lens and inclined surface were fabricated. These 3D structures can be used as master in electro-plating mold. This paper also summarized the work on the development of a simulation program for modeling the process of machining quasi-three dimensional shapes with the excimer laser beam on a constant moving polymer. Relatively simple masks of rectangle, triangle and half circle shape are considered. The etching depth is calculated by considering the number of laser pulses and the wavelength of laser beam irradiated on the various specimen surface such as PMMA, polyurethane and PI. It was found that similar shapes as experimental results, mask shape was designed to gain-lens surface which we want. As another method to manufacture micro lens the mask is made circular type and rotated during laser beam illumination. Opened mask area and scanning speed determine the surface shape of lens. Precise control of various parameters is admitted to fabricate micro optics.

Chang, Won-Seok; Yoon, Kyung-Ku; Kim, Jaegu; Shin, Bosung; Whang, Kyung-Hyun

2002-09-01

316

Laser ablation-induced spectral plasma characteristics in optical far- and near fields  

Microsoft Academic Search

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 experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of ~200 nm thickness

David J. Hwang; Hojeong Jeon; Costas P. Grigoropoulos; Jong Yoo; Richard E. Russo

2008-01-01

317

Effect of laser parameters on laser ablation and laser-induced plasma formation: A numerical modeling investigation  

Microsoft Academic Search

A comprehensive numerical model has recently been developed for nanosecond (ns) laser ablation of metallic targets, describing the processes of target heating, melting and vaporization, the resulting plume expansion in 1 atm helium gas, as well as plasma formation in the plume. In the present paper, we investigate the influence of laser parameters, i.e., laser irradiance, pulse duration and wavelength,

Annemie Bogaerts; Zhaoyang Chen

2005-01-01

318

Single droplet separations and surface partition coefficient measurements using laser ablation mass spectrometry  

PubMed Central

Surface activity of analytes plays a significant role in many chemical and physical phenomena. We present here a mass spectrometric method to characterize surface activity and solute partitioning between bulk liquid and the gas-liquid interface in droplets. The approach employs ablation by an IR laser from the surface of a microliter droplet deposited on a stainless steel post. The ablated material is ionized for mass spectrometric analysis by either droplet charging or by post-ionization in an electrospray plume. Three areas of application have been explored using this method; 1) separations in a single droplet: continuous ablation by a series of many successive laser pulses results in faster depletion of more surface active analytes, effectively comprising a surface activity-based separation. 2) Partition coefficient measurements: droplet volume is held constant during ablation by continually replenishing lost solvent. This leads to analyte-specific ion signal decay curves that may be fitted to a model based on Langmuir adsorption isotherms and simple analytical expressions, yielding quantitative values for the analyte surface partition coefficients. 3) Studies of the relationship between surface partitioning and HPLC phase partitioning: comparisons of surface activities measured by laser desorption with retention times in reversed phase HPLC reveal that the relationship between the two partitioning processes is very sensitive to chemical structure. Poor correlation between the retention time and surface activity is also observed within a subcategory of analytes (peptides). This effect is attributed to multi-modal solute-stationary phase interactions. The laser desorption approach presented here provides direct information on analyte surface activities free from the complications encountered in chromatographic methods due to chemical structure variations.

Jorabchi, Kaveh; Smith, Lloyd M.

2010-01-01

319

Ciliary White Light: Optical Aspect of Ultrashort Laser Ablation on Transparent Dielectrics  

NASA Astrophysics Data System (ADS)

We report on a novel nonlinear optical phenomenon, coined as ciliary white light, during laser ablation of transparent dielectrics. It is observed in 14 different transparent materials including glasses, crystals, and polymers. This phenomenon is also universal with respect to laser polarization, pulse duration, and focusing geometry. We interpret its formation in terms of the nonlinear diffraction of the laser generated white light by the ablation crater covered by nanostructures. It carries rich information on the damage profile and morphology dynamics of the ablated surface, providing a real time in situ observation of the laser ablation process.

Liu, Yi; Brelet, Yohann; He, Zhanbing; Yu, Linwei; Mitryukovskiy, Sergey; Houard, Aurélien; Forestier, Benjamin; Couairon, Arnaud; Mysyrowicz, André

2013-03-01

320

Ciliary white light: optical aspect of ultrashort laser ablation on transparent dielectrics.  

PubMed

We report on a novel nonlinear optical phenomenon, coined as ciliary white light, during laser ablation of transparent dielectrics. It is observed in 14 different transparent materials including glasses, crystals, and polymers. This phenomenon is also universal with respect to laser polarization, pulse duration, and focusing geometry. We interpret its formation in terms of the nonlinear diffraction of the laser generated white light by the ablation crater covered by nanostructures. It carries rich information on the damage profile and morphology dynamics of the ablated surface, providing a real time in situ observation of the laser ablation process. PMID:23496745

Liu, Yi; Brelet, Yohann; He, Zhanbing; Yu, Linwei; Mitryukovskiy, Sergey; Houard, Aurélien; Forestier, Benjamin; Couairon, Arnaud; Mysyrowicz, André

2013-03-01

321

Laser ablation of a platinum target in water. III. Laser-induced reactions  

NASA Astrophysics Data System (ADS)

This is the third paper in our series studying the laser-target-liquid interactions occurring in laser ablation in liquids (LAL). Here, laser ablation of a platinum target in pure water at 355 nm wavelength is studied as a function of laser energy. We describe three distinct reaction regimes between the ablated target species and water at different laser focusing conditions. At low laser fluence (<10 J/cm2), material removal is caused by laser heating of the platinum surface and the primary products are small clusters with a large percentage of platinum atoms in a nonzero oxidation state. At intermediate fluences (10-70 J/cm2), platinum nanoparticles are the primary products. Our previous studies demonstrated that in this fluence regime ablation occurs through both thermal vaporization and explosive ejection of molten droplets. In both cases reactivity is small due to the low reactivity of platinum with water. At high fluences (>70 J/cm2), we find large, faceted particles that are attributed to the drying of PtOx gels formed by reactive plasma etching of the target. Taken together these results demonstrate that significant tunability in the target-liquid interaction is possible during nanomaterial synthesis by LAL.

Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto

2006-12-01

322

Fabrication of microchannels by UV laser ablation  

NASA Astrophysics Data System (ADS)

This paper describes the fabrication of micro-channels in resin for micro-fluidic devices by a UV laser. Quartz wafers are coated with a 20?m thick BCB resin. Micro-grooves for micro-channels are fabricated into the BCB resin by a KrF excimer laser. The groove bottom is 100m wide at a pulse width of 20nsec, fluence of 1.3mJ/cm2/pulse, and overlap of 98.9%. The wafer surface serves as the bottom face of the groove. Moreover the side wall angle is 72°. Furthermore, the grooves are covered with laminate films to prevent leakage of the liquid samples. A thermoplastic film or a heat-hardening resin film is used as a laminate film. Laminating conditions are: roller temperatures of 120°C, pressure of 0.8MPa, and laminating speed of 0.2m/min. The thermoplastic film coats the groove perfectly. On the contrary, the heat-hardening film does not sag into the groove, resulting in an open-are cross-sectional ration of 80%. Furthermore, the open-area-ratio becomes 100% through a heat-curing process at a temperature of 120°C for 30min. The through holes are made in the laminate film by a KrF excimer laser. Inlet pipe for a micro-pump are inserted into the hole.

Takahashi, Satoshi; Suzuki, Yoshimasa; Yoshida, Yoshikazu

2003-02-01

323

A study of particle generation during laser ablation withapplications  

SciTech Connect

A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained in-line using a differential mobility analyzer (DMA) and a particle counter. The experimental results show that the particle size varies with laser energy, laser pulsewidth, ambient gas flow rate and sample properties. The results serve as a basis for controlling the size of nanoparticles generated by laser ablation. Laser shadowgraph imaging was used to study mass ejection processes and mechanisms. At higher laser irradiance, some particles were ejected in the liquid and even in the solid phase. Time-resolved images show the propagation of the shockwaves: external shockwaves propagate outward and decelerate, and internal shockwaves reflect back and forth between the gas contact surface and the sample surface. The internal shockwave is proposed to cause the ejection of liquid particles when the internal shockwave strikes the liquid molten layer. A simulation based on vapor plume expansion was carried out and provides satisfactory agreement with experimental results. Different material properties result in different particle ejection behavior:particle ejection for most materials including metals result in a conically shaped envelope for the ejected material while ejection for silicon resembles a liquid jet. The difference in density change when the materials melt was proposed to be an important factor in the different ejection behavior. The characteristics of particles generated by laser ablation have a strong influence on the chemical analysis of the irradiated sample. Large particles are more difficult to completely vaporize and ionize, and induced preferential vaporization causes fractionation (i.e. a detected chemical composition that differs from the sample material). Large particles also result in spikes in measurements using inductively coupled plasma mass spectrometry (ICP-MS) which result in errors. Three different methods were employed to study the effects of particle size on chemical analysis: generating smaller particles utilizing a fs laser, filtering out larger particles with a cascade impactor and altering the size distribution by using a second pulse to fracture particles generated from the first pulse. It was found that the chemical composition of the particles varies with particle size. The variation of the composition with respect to particle size was analyzed and it was proposed that it was related to the vapor formed particles condensing on larger ejected liquid droplets.

Liu, Chunyi

2005-08-12

324

Femtosecond and picosecond laser microablation: ablation efficiency and laser microplasma expansion  

Microsoft Academic Search

Laser ablation efficiency and plasma plume expansion were studied using the interaction of Ti-Al2O3 laser pulses (wavelength 800 nm; energy 20 7J; mode TEM00; waist diameter 11 7m; pulse durations 70 fs, 150 fs, 0.4 ps, 0.8 ps, 2 ps, and 10 ps) with copper in air. A moderate laser pulse energy of 20 7J was used to eliminate the

B. Sallé; O. Gobert; P. Meynadier; M. Perdrix; G. Petite; A. Semerok

1999-01-01

325

Recent developments in laser ablation ICP-MS with a 157nm excimer laser  

Microsoft Academic Search

A new laser system, a Lambda-Physiks excimer laser (LPF 202) at 157 nm, has been installed and coupled to the Plasma 54 MC-ICP-MS. Low wavelength laser such as 193nm (used in many LA-ICP-MS facilities) and very low wavelength such as 157nm have high absorption coefficients during ablation. In the case of 157nm, it results in a very good coupling between

E. F. Rose-Koga; P. Telouk; F. Albarede

2003-01-01

326

Femtosecond laser ablation of polymethyl-methacrylate with high focusing control  

NASA Astrophysics Data System (ADS)

Ablation of PMMA with femtosecond laser pulses was studied.A z-scan procedure is used for placing the surface in the beam waist.Ablation craters with 200 nm diameter can be produced.Ablation threshold of PMMA is 3.2 J/cm2.

Fernández-Pradas, J. M.; Florian, C.; Caballero-Lucas, F.; Morenza, J. L.; Serra, P.

2013-08-01

327

Onset of laser ablation in CaF2 crystal under excimer laser irradiation  

NASA Astrophysics Data System (ADS)

With the widespread application of excimer lasers for micro- processing, optically transparent materials in the UV region have become more important as optical components. The transparent materials currently available commercially are silica glass and fluoride crystals, CaF2 and MgF2. The resistance of these materials against cumulative irradiation of excimer lasers is required from the viewpoint of application, and it is important to clarify the mechanisms of the optical damage on these materials. In this paper, we report the onset of laser ablation, that is, the initiation of optical breakdown and plume formation, in CaF2 crystal under cumulative irradiation of an ArF excimer laser. When the laser fluence is below the ablation threshold, a blue luminescence due to self-trapped exciton is observed from the whole laser-irradiated region. When the fluence ins increased near the threshold, successive irradiation finally cause a bright, localized luminescence due to the initiation of laser ablation. SEM images of the laser-damaged region show two features: (1) a small bump with pits of the order of 0.1 micrometers formed by UV laser absorption and following local heating, (2) small cracks with triangular fragments caused by mechanisms stress under local heating.

Kawaguchi, Yoshizo; Narazaki, Aiko; Sato, Tadatake; Niino, Hiroyuki; Yabe, Akira

2002-06-01

328

Testing of concrete by laser ablation  

SciTech Connect

A method of testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed.

Flesher, Dann J. (Benton City, WA); Becker, David L. (Kennewick, WA); Beem, William L. (Kennewick, WA); Berry, Tommy C. (Kennewick, WA); Cannon, N. Scott (Kennewick, WA)

1997-01-01

329

Testing of concrete by laser ablation  

DOEpatents

A method is disclosed for testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed. 1 fig.

Flesher, D.J.; Becker, D.L.; Beem, W.L.; Berry, T.C.; Cannon, N.S.

1997-01-07

330

Angular emission of ions and mass deposition from femtosecond and nanosecond laser-produced plasmas  

NASA Astrophysics Data System (ADS)

We investigated the angular distribution of ions and atoms emanating from femto- and nanosecond laser-produced metal plasmas under similar laser fluence conditions. For producing plasmas, aluminum targets are ablated in vacuum employing pulses from a Ti:Sapphire ultrafast laser (40 fs, 800 nm) and an Nd:YAG laser (6 ns, 1064 nm). The angular distribution of ion emission as well as the kinetic energy distribution is characterized by a Faraday cup, while a quartz microbalance is used for evaluating deposited mass. The ion and deposited mass features showed that fs laser ablated plasmas produced higher kinetic energy and more mass per pulse than ns plumes over all angles. The ion flux and kinetic energy studies show fs laser plasmas produce narrower angular distribution while ns laser plasmas provide narrower energy distribution.

Verhoff, B.; Harilal, S. S.; Hassanein, A.

2012-06-01

331

Femtosecond laser ablation characteristics of nickel-based superalloy C263  

Microsoft Academic Search

Femtosecond laser (180 fs, 775 nm, 1 kHz) ablation characteristics of the nickel-based superalloy C263 are investigated. The\\u000a single pulse ablation threshold is measured to be 0.26±0.03 J\\/cm2 and the incubation parameter ?=0.72±0.03 by also measuring the dependence of ablation threshold on the number of laser pulses.\\u000a The ablation rate exhibits two logarithmic dependencies on fluence corresponding to ablation determined

N. G. Semaltianos; W. Perrie; M. Sharp; G. Dearden; S. Logothetidis; K. G. Watkins

2009-01-01

332

Laser ablation of polymer coatings allows for electromagnetic field enhancement mapping around nanostructures  

SciTech Connect

Subdiffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures. The accompanying field enhancement substantially lowers the ablation threshold of the polymer film and thus creates local ablation spots and corresponding topographic modifications of the polymer film. Such modifications are quantified straightforwardly via scanning electron microscopy and atomic force microscopy. Thickness variation in the polymer film enables the investigation of either the initial ablation phase or ablation induced by collective enhancement effects.

Fiutowski, J.; Maibohm, C.; Kjelstrup-Hansen, J.; Rubahn, H.-G. [Mads Clausen Institute, NanoSYD, University of Southern Denmark, Alsion 2, DK-6400, Soenderborg (Denmark)

2011-05-09

333

Controlled USP laser ablation strategies for shaping optics  

NASA Astrophysics Data System (ADS)

Non-linear absorption and athermal ablation effects are two of the most attractive benefits of ultrashort pulsed (USP) laser radiation for optics manufacturing. The conventional generation of complex shapes still is a challenging problem for engineers and constrains the outcome of new products and applications in combination with aspheric and freeform optical shapes. To create a process chain for these shapes based on USP is the definition of task. We accomplished experiments with a 18W lasersystem (<15ps) and analysed ablation strategies beginning from selective to three dimensional removal on different optical materials. Therefore dependent variables like roughness (RMS), irregularities (IRR) in terms of shape accuracy and sub-surface damages (SSD) give suggestions for parametrical improvements. The aim is to substitute grinding procedures by creating path-time-controlled removal functions to achieve polishable surface quality.

Schindler, Christian; Giesecke, Jan; Bliedtner, Jens; Mueller, Hartmut; Waechter, Sebastian; Giggel, Volkmar

2012-05-01

334

Laser ablation of polished and nanostructured titanium surfaces by nanosecond laser pulses  

NASA Astrophysics Data System (ADS)

A comparison of the IR nanosecond laser ablation parameters for polished and nanostructured titanium samples has been performed. The titanium foil was mechanically polished and pres-structured by multiple 744-nm femtosecond laser pulses producing large surface spots covered by ripples with periods in range of 400-500 nm. In order to evaluate the influence of such nanoripples, the nanosecond laser ablation and laser plasma properties were compared for polished surface, surface with nanoripples parallel and orthogonal to the laser beam polarization. A substantial decrease of the nanosecond ablation threshold was observed for the nanostructured in contrast to polished surface was detected while no influence of the ripple orientation vs. beam polarization was revealed. The comparison of plasma spectra for the ablation cases demonstrated that intensity of basic atomic lines and plasma emission duration were 2-5 times larger for the polished sample while spectra evolution was faster for the nanostructured sample. Plasma temperature and electron density were slightly lower for nanostructured sample while laser beam polarization has no effect on plasma properties.

Lednev, Vasily N.; Pershin, Sergey M.; Ionin, Andrey A.; Kudryashov, Sergey I.; Makarov, Sergey V.; Ligachev, Alexander E.; Rudenko, Andrey A.; Chmelnitsky, Roman A.; Bunkin, Alexey F.

2013-10-01

335

Thickness determination of subnanometer layers using laser ablation inductively coupled plasma mass spectrometry.  

PubMed

Laser ablation inductively coupled plasma mass spectrometry has been applied to determine the thickness of subnanometer (subnm) metallic layers. Metallic Nd was deposited onto Si wafers with 0.5, 1, 3, and 6 nm thickness and covered by a 10 nm Al coating. Integrated ion signals corresponded to the layer thickness, indicating that external calibration provides accurate data. Utilizing sensitivity ratios obtained from ablation of a glass standard reference material (SRM) and the Al layer as reference, the deviations between prepared and measured layer thickness were less than 10%. A further attempt was made to determine the layer thickness with the absolute sensitivity obtained from ablation of a glass SRM. The approach also yielded a linear correlation between determined and actual layer thickness, but bias and interday variability were significantly higher. This is assumed to result from imprecise determination of the crater size when ablating the glass SRM. This study shows that subnm layers of metals can be analyzed for their thickness either using reference materials of identical composition or using sensitivity ratios when one layer can be used as a reference. Absolute determination of the layer thickness is less accurate but can circumvent the lack of reference materials of similar composition. PMID:22978293

Hattendorf, Bodo; Pisonero, Jorge; Günther, Detlef; Bordel, Nerea

2012-10-02

336

Femtosecond laser ablation induced plasma characteristics from submicron craters in thin metal film  

SciTech Connect

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 time-resolved emission images and the corresponding spectra depict the detailed plasma evolution at the fluence range near the ablation threshold. Collected emission spectra at the laser fluence level of around two to three times of ablation threshold display characteristic atomic transition peaks of the ablated Cr material from submicron ablation craters. This finding confirms that improved spatial resolution for laser-induced breakdown spectroscopy can be achieved.

Hwang, David J.; Jeon, Hojeong; Grigoropoulos, Costas P.; Yoo, Jong; Russo, Richard E. [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California 94720-1740 (United States); Applied Spectra, 48834 Kato Rd, Suite 109A, Fremont, California 94538 (United States)

2007-12-17

337

Evaluation of Inductively Couple Plasma-time-of-Flight Mass Spectrometry for Laser Ablation Analyses  

SciTech Connect

The purpose of this trip to LECO Corporation was to test the non-matrix matched calibration method and the principal component analysis (PCA) method on a laser ablation-inductively coupled plasma-time of flight mass spectrometry (LA-ICP-TOFMS) system. An LA-ICP-TOFMS system allows for multielement single-shot analysis as well as spatial analysis on small samples, because the TOFMS acquires an entire mass spectrum for all ions extracted simultaneously from the ICP. The TOFMS system differs from the double-focusing mass spectrometer, on which the above methods were developed, by having lower sensitivity and lower mass resolution.

S.J. Bajic; D.B. Aeschliman; D.P. Baldwin; R.S. Houk

2003-09-30

338

Peak polarity overturn for charged particles in laser ablation process  

SciTech Connect

The charged particles emitted during laser ablation off a brass target are detected using a metal probe in air. A special phenomenon is found in the recorded signals: following a giant electromagnetic peak observed immediately after the emission of the pulsed laser, a minor peak occurs whose polarity merely depends on the distance between the probe and the laser focal spot on the target. Under the condition of our experiment, the overturn point is 1.47 mm, i.e., the minor peak remains negative when the probe distance is less than 1.47 mm; it becomes positive while the probe is set at a distance beyond 1.47 mm. A hypothesis is proposed to explain the overturn that takes the flight behavior of the charged particles both in plasma and propagating shock wave into consideration.

Zhang, P.; Ji, Y. J.; Lai, X. M.; Bian, B. M.; Li, Z. H. [Department of Information Physics and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

2006-07-01

339

Magnetic resonance-guided percutaneous laser ablation of uterine fibroids.  

PubMed

Laser ablation of uterine fibroids using a percutaneous approach under local anesthetic in an open magnetic resonance (MR) scanner was performed in 12 symptomatic women awaiting hysterectomy. Accurate laser fiber placement was assisted by the use of an MR needle tracking system, as well as laser heat dissipation monitored during treatment by a real-time imaging processor. This day case procedure was well tolerated by all women, with eight women subsequently declining their planned surgery. Follow-up measurements of treated fibroid volume by MRI demonstrated a mean decrease of 37.5% at 3 months. This novel minimally invasive approach offers an alternative to surgery for women with fibroids, but longer follow-up is required to ascertain maximal fibroid shrinkage and to compare outcome with traditional surgery. PMID:11042638

Law, P; Gedroyc, W M; Regan, L

2000-10-01

340

Evaluation of the analytical capability of NIR femtosecond laser ablation-inductively coupled plasma mass spectrometry.  

PubMed

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 the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of (57)Fe, obtained from iron sulfide (FeS(2)), demonstrated that the resulting signal intensity of (57)Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm(2)). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the (206)Pb/(238)U (f(Pb/U)) and (238)U/(232)Th (f(U/Th)) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of (56)Fe and the isotopic ratios ((57)Fe/(54)Fe and (56)Fe/(54)Fe) have been measured on a natural pyrite (FeS(2)) sample. Repeatability in signal intensity of (56)Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in (57)Fe/(54)Fe and (56)Fe/(54)Fe ratio measurements could be improved by the fs-laser ablation system. The data obtained here clearly demonstrate that, even with the fundamental wavelength (NIR operating at 780 nm), the fs-laser ablation system has the potential to become a significant tool for in-situ elemental and isotopic analysis of geochemical samples including heavy minerals and metallic materials. PMID:18332541

Hirata, Takafumi; Kon, Yoshiaki

2008-03-01

341

Biopolymer analysis by laser ablation and mass spectrometry  

SciTech Connect

Various matrix materials were used for laser desorption of biological molecules, which include proteins and oligonucleotides. Both matrix-assisted laser desorption ionization (MALDI) and matrix-assisted laser desorption with post-ionization (MALPI) have been tried. Detection sensitivity of a few hundred femtomoles has been achieved by MALDI for oligomers and proteins. Both positive and negative ions were observed with comparative sizes of signals. No significant fragmentation was observed.

Tang, K.; Allman, S.L.; Chen, C.H. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6378 (United States)

1993-10-10

342

Depth profiling and imaging capabilities of an ultrashort pulse laser ablation time of flight mass spectrometer.  

PubMed

An ultrafast laser ablation time-of-flight mass spectrometer (AToF-MS) and associated data acquisition software that permits imaging at micron-scale resolution and sub-micron-scale depth profiling are described. The ion funnel-based source of this instrument can be operated at pressures ranging from 10(-8) to ~0.3 mbar. Mass spectra may be collected and stored at a rate of 1 kHz by the data acquisition system, allowing the instrument to be coupled with standard commercial Ti:sapphire lasers. The capabilities of the AToF-MS instrument are demonstrated on metal foils and semiconductor wafers using a Ti:sapphire laser emitting 800 nm, ~75 fs pulses at 1 kHz. Results show that elemental quantification and depth profiling are feasible with this instrument. PMID:23020378

Cui, Yang; Moore, Jerry F; Milasinovic, Slobodan; Liu, Yaoming; Gordon, Robert J; Hanley, Luke

2012-09-01

343

Physics and diagnostics of laser ablation plume propagation for high- Tc superconductor film growth  

SciTech Connect

The formation, composition and propagatin of laser-produced plasmas used for pulsed laser deposition (PLD) of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} have been studied under film growth conditions. Four complementary spatially- and temporally-resolved in situ diagnostic techniques are applied to characterize the expansion of the laser plume into both vacuum and ambient gases: optical emission and absorption spectroscopy, fast ion probe measurements, and fast photography with a gated, image-intensified CCD array (ICCD) camera system. Transient optical absorption spectroscopy reveals large densities of ground state atoms, ions, and molecules in the plume as well as a slower component to the plume transport than is indicated by the plasma fluorescence and ion current. Ablation into background gases results in scattering attenuation of the laser plume. The exponential attenuation of the positive ion flux transmitted through 50--300 m Torr background oxygen is measured and used to define an overall ion-oxygen reaction cross section of {sigma}{sub {eta}-O{sub 2}} = 2.3 {times} 10{sup {minus}16} cm{sup 2} under the described film growth conditions. The slowing of the laser plasma and formation of shock structures due to collisions with the ambient gas are described using ion probe measurements and ICCD photographic comparisons of expansion into vacuum and background oxygen. At the pressures used for PLD, distance-time (R-t) plots derived from the photographs and ion probe waveforms indicate that the higher pressure plume initially expands through the ambient gas in accordance with a drag model experiencing little slowing until a visible shock structure forms. Following a transition period, in which the plume appears to have two components, a single component shock structure propagates in better agreement with a shock, or blast wave model.

Geohegan, D.B.

1992-03-01

344

Physics and diagnostics of laser ablation plume propagation for high-{Tc} superconductor film growth  

SciTech Connect

The formation, composition and propagatin of laser-produced plasmas used for pulsed laser deposition (PLD) of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} have been studied under film growth conditions. Four complementary spatially- and temporally-resolved in situ diagnostic techniques are applied to characterize the expansion of the laser plume into both vacuum and ambient gases: optical emission and absorption spectroscopy, fast ion probe measurements, and fast photography with a gated, image-intensified CCD array (ICCD) camera system. Transient optical absorption spectroscopy reveals large densities of ground state atoms, ions, and molecules in the plume as well as a slower component to the plume transport than is indicated by the plasma fluorescence and ion current. Ablation into background gases results in scattering attenuation of the laser plume. The exponential attenuation of the positive ion flux transmitted through 50--300 m Torr background oxygen is measured and used to define an overall ion-oxygen reaction cross section of {sigma}{sub {eta}-O{sub 2}} = 2.3 {times} 10{sup {minus}16} cm{sup 2} under the described film growth conditions. The slowing of the laser plasma and formation of shock structures due to collisions with the ambient gas are described using ion probe measurements and ICCD photographic comparisons of expansion into vacuum and background oxygen. At the pressures used for PLD, distance-time (R-t) plots derived from the photographs and ion probe waveforms indicate that the higher pressure plume initially expands through the ambient gas in accordance with a drag model experiencing little slowing until a visible shock structure forms. Following a transition period, in which the plume appears to have two components, a single component shock structure propagates in better agreement with a shock, or blast wave model.

Geohegan, D.B.

1992-03-01

345

Cavity Formation and Material Ablation for Single-Pulse Laser-Ablated Solids Immersed in Water at High Pressure  

NASA Astrophysics Data System (ADS)

The effects of hydrostatic pressure on cavity formation and material ablation have been investigated for a brass plate immersed in water irradiated by a single laser pulse of duration <10 ns. Shadowgraph imaging and volumetric measurements of the ablated material demonstrate that the density of the material inside the cavity does not vary significantly for hydrostatic pressures between 0.1 and 30 MPa (300 atm) during the early stages, <600 ns after laser irradiation, indicating that the pressures induced by focusing a high-power laser in the confined medium dominate the transient pressure regime over this period.

Thornton, Blair; Takahashi, Tomoko; Ura, Tamaki; Sakka, Tetsuo

2012-10-01

346

Ablation processing of biomedical materials by ultrashort laser pulse ranging from 50 fs through 2 ps  

NASA Astrophysics Data System (ADS)

In recent years, femtosecond laser processing of human hard/soft tissues has been studied. Here, we have demonstrated ablation etching of hydroxyapatite. Hydroxyapatite (Ca10(PO4)6(OH)2) is a key component of human tooth and human bone. The human bone is mainly made of hydroxyapatite oriented along the collagen. The micromachining of hydroxyapatite is highly required for orthopedics and dentistry. The important issue is to preserve the chemical property of the ablated surface. If chemical properties of hydroxyapatite change once, the human bone or tooth cannot grow again after laser processing. As for nanosecond laser ablation (for example excimer laser ablation), the relative content of calcium and phosphorus in (Ca10(PO4)6(OH)2) is found to change after laser ablation. We used here pulsewidth tunable output from 50 fs through 2 ps at 820 nm and 1 kpps. We measured calcium spectrum and phosphorus spectrum of the ablated surface of hydroxyapatite by XPS. As a result, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs - 2-ps laser ablation. We also demonstrated ablation processing of human tooth with Ti:sapphire laser, and precise ablation processing and microstructure fabrication are realized.

Ozono, Kazue; Obara, Minoru; Sakuma, Jun

2003-06-01

347

Pulsed laser ablation growth and doping of epitaxial compound semiconductor films  

SciTech Connect

Pulsed laser ablation (PLA) has several characteristics that are potentially attractive for the growth and doping of chemically complex compound semiconductors including (1) stoichiometric (congruent) transfer of composition from target to film, (2) the use of reactive gases to control film composition and/or doping via energetic-beam-induced reactions, and (3) low-temperature nonequilibrium phase formation in the laser-generated plasma ``plume.`` However, the electrical properties of compound semiconductors are far more sensitive to low concentrations of defects than are the oxide metals/ceramics for which PLA has been so successful. Only recently have doped epitaxial compound semiconductor films been grown by PLA. Fundamental studies are being carried out to relate film electrical and microstructural properties to the energy distribution of ablated species, to the temporal evolution of the ablation pulse in ambient gases, and to beam assisted surface and/or gas-phase reactions. In this paper the authors describe results of ex situ Hall effect, high-resolution x-ray diffraction, transmission electron microscopy, and Rutherford backscattering measurements that are being used in combination with in situ RHEED and time-resolved ion probe measurements to evaluate PLA for growth of doped epitaxial compound semiconductor films and heterostructures. Examples are presented and results analyzed for doped II-VI, I-III-VI, and column-III nitride materials grown recently in this and other laboratories.

Lowndes, D.H.; Rouleau, C.M.; Geohegan, D.B.; Budai, J.D.; Poker, D.B. [Oak Ridge National Lab., TN (United States). Solid State Div.; Puretzky, A.A. [Inst. of Spectroscopy, Troitsk (Russian Federation); Strauss, M.A.; Pedraza, A.J.; Park, J.W. [Univ. of Tennessee, Knoxville, TN (United States)

1995-12-01

348

Low work function surface layers produced by laser ablation using short-wavelength photons  

SciTech Connect

Short-wavelength photons are used to ablate material from a low work function target onto a suitable substrate. The short-wavelength photons are at or below visible wavelength. The elemental composition of the deposit is controlled by the composition of the target and the gaseous environment in which the ablation process is performed. The process is carried out in a deposition chamber to which a short-wavelength laser is mounted and which includes a substrate holder which can be rotated, tilted, heated, or cooled. The target material is mounted onto a holder that spins the target during laser ablation. In addition, the deposition chamber is provided with a vacuum pump, an external gas supply with atomizer and radical generator, a gas generator for producing a flow of molecules on the substrate, and a substrate cleaning device, such as an ion gun. The substrate can be rotated and tilted, for example, whereby only the tip of an emitter can be coated with a low work function material.

Balooch, Mehdi (Berkeley, CA); Dinh, Long N. (Concord, CA); Siekhaus, Wigbert J. (Berkeley, CA)

2000-01-01

349

Study on the carbon fragment anions produced by femtosecond laser ablation of solid C60  

NASA Astrophysics Data System (ADS)

Production of the anions (negative ions) has been observed by femtosecond laser ablation (fsLA) of solid C60 with a time-of-flight (TOF) mass spectrometer. In contrast to C60+, production of C60- due to an electron capture is found very limited because of the small electron affinity of the C60 molecule. Narrow TOF peaks of small carbon fragment anions Cn- (n <= 23) suggest instantaneous production of the fragment anions through dissociative ionization of C60. Production of the mono-hydrogenated carbon fragment anions CnH- has been observed and also the abrupt change in the yield of CnH- has been observed at n = 10, which is attributed to the structural change of the carbon fragments from a linear chain to a monocyclic ring. The results are found similar to those obtained for the carbon fragments produced by nanosecond laser ablation (nsLA) of solid C60, which demonstrates that the thermalization in an ablation plasma washes away any difference in the nature of carbon fragments produced by fsLA and nsLA.

Kobayashi, Tohru; Matsuo, Yukari

2011-02-01

350

Dynamics of femtosecond laser ablation studied with time-resolved x-ray absorption fine structure imaging  

NASA Astrophysics Data System (ADS)

We studied the dynamics of the femtosecond laser ablation of aluminum in an energy range well above the ablation threshold with the ultrafast time-resolved x-ray-absorption fine structure imaging technique. Analyzing the spectral structures near the L absorption edge that appeared in one-dimensional images of soft-x-ray absorbance, we successfully identified doubly and singly charged ions, neutral atoms, liquid nanoparticles, and possible atomic clusters in the expanding ablation plume. We also clarified that the ejected particles depend strongly on the laser irradiation intensity. The spatiotemporal evolution of the ablation particles allows us to estimate the spatial distribution of atomic density and the ejection velocity of each type of particle. In particular, we discuss the temporal sequence of the particle ejection in the early stages of plume expansion. Our experimental results strongly support the idea that photomechanical fragmentation and vaporization are dominant mechanisms for the production of liquid nanoparticles and neutral atoms, respectively, in femtosecond laser ablation induced in an irradiation intensity range of 1014-1015W/cm2 .

Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

2009-04-01

351

Endovenous Laser Ablation of Incompetent Perforator Veins: A New Technique in Treatment of Chronic Venous Disease  

SciTech Connect

The aim of this study was to assess the feasibility of endovenous laser ablation of incompetent perforator veins in a patient with incompetency of the small saphenous vein and multiple perforator veins. Two different methods were used to ablate seven perforator veins with a laser giving 50-60 J/cm energy. Total occlusion was observed in six perforators, and partial ablation in one perforator, at 1-month follow-up. To our knowledge, endovenous laser ablation of incompetent perforator veins is easy and a good therapeutic method.

Ozkan, Ugur, E-mail: radugur@yahoo.co [Baskent University, Faculty of Medicine, Department of Radiology (Turkey)

2009-09-15

352

Phase explosion and recoil-induced ejection in resonant-infrared laser ablation of polystyrene  

NASA Astrophysics Data System (ADS)

We investigate the phenomenon of resonant-infrared laser ablation of polymers using polystyrene as a model material. Ablation is carried out using various mid-IR laser wavelengths that are resonant with vibrational modes of a polystyrene target. Time-resolved plume imaging coupled with etch-depth measurements and thermal calculations indicate that ablation begins after a superheated surface layer reaches a temperature of ˜1000°C and undergoes spinodal decomposition. The majority of the ablated material is then expelled by way of recoil-induced ejection as the pressure of the expanding vapor plume compresses a laser-melted area.

Johnson, S. L.; Bubb, D. M.; Haglund, R. F.

2009-08-01

353

Towards redistribution laser cooling of molecular gases: production of candidtate molecules SrH by laser ablation  

NASA Astrophysics Data System (ADS)

Laser cooling by collisional redistribution of radiation has been successfully applied in the past for cooling dense atomic gases. Here we report on progress of work aiming at the demonstration of redistribution laser cooling in a molecular gas. The candidate molecule strontium monohydride is produced by laser ablation of strontium dihydride in a pressurized noble gas atmosphere. The composition of the ablation plasma plume is analyzed by measuring its emission spectrum. The dynamics of SrH molecular density following the ablation laser pulse is studied as a function of the buffer gas pressure and the laser intensity.

Simon, P.; Moroshkin, P.; Weller, L.; Saß, A.; Weitz, M.

2013-03-01

354

Myocardial tissue ablation by single high-energy laser pulses for ELR and TMR  

Microsoft Academic Search

The objective of this study is to compare the ablation sites induced by two different laser and application systems for myocardial laser revascularization. One system used was an 800 W CO2 laser, which is clinically established for transmyocardial laser revascularization (TMR). The second system was a self-designed Holmium laser emitting single high energy pulses for the minimal invasive approach of

Dirk Theisen; Ralf Brinkmann; Hans-Martin Stubbe; Reginald Birngruber

1999-01-01

355

Laser applications in nanotechnology: nanofabrication using laser ablation and laser nanolithography  

NASA Astrophysics Data System (ADS)

The fact that nanoparticles and nanomaterials have fundamental properties different both from their constituent atoms or molecules and from their bulk counterparts has stimulated great interest, both theoretical and practical, in nanoparticles and nanoparticle-based assemblies (functional materials), with the result that these structures have become the subject of explosive research over the last twenty years or so. A great deal of progress in this field has relied on the use of lasers. In this paper, the directions followed and results obtained in laser nanotechnology research are reviewed. The parameters, properties, and applications of nanoparticles are discussed, along with the physical and chemical methods for their fabrication and investigation. Nanofabrication applications of and fundamental physical principles behind laser ablation and laser nanolithography are discussed in detail. The applications of laser radiation are shown to range from fabricating, melting, and evaporating nanoparticles to changing their shape, structure, size, and size distribution, through studying their dynamics and forming them into periodic arrays and various structures and assemblies. The historical development of research on nanoparticles and nanomaterials and the application of laser nanotechnology in various fields are briefly reviewed.

Makarov, G. N.

2013-07-01

356

Laser fluence effects on ion emission from a laser-generated Cu plasma  

NASA Astrophysics Data System (ADS)

We present details of an experimental facility developed for the diagnostics of highly charged ions produced during pulsed laser ablation of solid targets. A range of laser fluences (2-10 J cm-2) from a Q-switched Nd : YAG laser (wavelength = 1064 nm, pulse duration ~10 ns) was used to generate a copper plasma. The ion diagnostics were based on the time-of-flight (TOF) methods; an ion collector and a 45° parallel plate electrostatic ion energy analyser were used. A channel electron multiplier located 1.31 m away from the Cu target was used to record the energy-resolved TOF ion spectrum. The effect of laser fluence on the total ion charge, average ion energy and charge state distribution was investigated. The estimated threshold fluence for the onset of the plasma was 2.5 J cm-2. About four times increase in both average ion energy and total ion charge was observed in the investigated laser fluence range. The maximum attainable charge state of the Cu ions increased from 1+ to 7+ with the increase in laser fluence. The correlation between relative abundance of the various ion charge states indicated that the formation of Cun+ occurred through ionization from Cu(n-1)+ by the impact of fast electrons or by multiphoton interactions.

Ilyas, B.; Dogar, A. H.; Ullah, S.; Qayyum, A.

2011-07-01

357

Laser ablative cutting of ceramics for electronics applications  

SciTech Connect

Pulsed, high-beam quality lasers offer unique materials processing characteristics. In processing metals, copper vapor and pulsed Nd:YAG lasers have produced micron-scale cuts and holes with submicron heat-affected zones. Since the cost of laser photons is high and average material removal rates can be slow with ablation, high value-added applications are necessary to justify processing costs. Ceramics present a special challenge for manufacturing because of their high hardness, relatively low thermal conductivity, and brittle nature. Surface damage typically limits the strength of a ceramic part to a small fraction of its bulk strength. This work investigates the use of copper vapor and pulsed diode-pumped Nd:YAG lasers to cut precision features in ceramic substrates. Variations in laser wavelength and power, processing speed, ceramic type, and assist gas were investigated with the goal of producing <100-{mu}m wide by 600-{mu}m deep cuts through silicon-carbide and alumina/titanium-carbide substrates for potential use in electronics. Silicon-carbide bars 250-{mu}m wide by 600-{mu}m high by 2.5-cm long were laser cut from substrates without fracture.

Warner, B. E., LLNL

1996-03-01

358

Heat transfer and phase change during picosecond laser ablation of nickel  

Microsoft Academic Search

This work investigates heat transfer and phase change during picosecond laser ablation of nickel. In this study, ablation of nickel is studied using a mode-locked 25 ps (FWHM) Nd:YAG laser. The threshold fluence for mass removal (ablation) is experimentally determined. Numerical calculations of the transient temperature distribution and kinetics of the solid–liquid and liquid–vapor phase change interfaces are performed. The

David A. Willis; Xianfan Xu

2002-01-01

359

Plume Dynamics in Tea CO2 Laser Ablation of Polymers and Graphite  

Microsoft Academic Search

Streak photography of TEA-CO2 laser ablation of graphite and polymers in helium and argon background gases showed two luminous fronts lifting off the ablation targets at delayed intervals. The first luminous front was driven by the plume from the immediate ablation of top surface layer of polymer, while the second front by the delayed ejection of laser-decomposed, heavy fragment of

T. Y. Tou; O. H. Chin

2008-01-01

360

Characterization of Individual Microneedles Formed on Alloy Surfaces by Femtosecond Laser Ablation  

NASA Astrophysics Data System (ADS)

Cross-sectional microstructural analyses of micron/nano-sized structures (termed microneedles) formed by low and high fluence pulse laser ablation of AISI 4340 steel, Ti6Al4V, and Al 5754 alloy specimens were performed. Dependence of length scale and orientation of microneedle microstructures on energy absorptance during laser irradiation, heat transfer direction, absorptivity, and thermal conductivity of the material was established. Microneedle nucleation and growth process were explained based on penetration depths, redeposition of ablated material, and ablation rates.

Bhattacharya, Sudip; Kam, Dong Hyuck; Song, Lijun; Mazumder, Jyotirmoy

2012-08-01

361

Phase explosion and recoil-induced ejection in resonant-infrared laser ablation of polystyrene  

Microsoft Academic Search

We investigate the phenomenon of resonant-infrared laser ablation of polymers using polystyrene as a model material. Ablation is carried out using various mid-IR laser wavelengths that are resonant with vibrational modes of a polystyrene target. Time-resolved plume imaging coupled with etch-depth measurements and thermal calculations indicate that ablation begins after a superheated surface layer reaches a temperature of ˜1000°C and

S. L. Johnson; D. M. Bubb; R. F. Haglund

2009-01-01

362

Phase explosion and recoil-induced ejection in resonant-infrared laser ablation of polystyrene  

Microsoft Academic Search

We investigate the phenomenon of resonant-infrared laser ablation of polymers using polystyrene as a model material. Ablation\\u000a is carried out using various mid-IR laser wavelengths that are resonant with vibrational modes of a polystyrene target. Time-resolved\\u000a plume imaging coupled with etch-depth measurements and thermal calculations indicate that ablation begins after a superheated\\u000a surface layer reaches a temperature of ?1000°C and

S. L. Johnson; D. M. Bubb; R. F. Haglund Jr

2009-01-01

363

Human cornea wound healing in organ culture after Er:YAG laser ablation  

Microsoft Academic Search

Purpose: To study the healing process in cultured human corneas after Er:YAG laser ablation. Methods: Human cadaver corneas within 24 hours post mortem were ablated with a Q- switched Er:YAG laser at 2.94 micrometer wavelength. The radiant exposure was 500 mJ\\/cm2. The cornea was cultured on a tissue supporting frame immediately after the ablation. Culture media consisted of 92% minimum

Jin-Hui Shen; Karen M. Joos; Richard D. Robinson; Debra J. Shetlar; Denis M. O'Day

1998-01-01

364

Stable carbon and oxygen isotope analysis of fossil tooth enamel using laser ablation  

Microsoft Academic Search

A technique is described whereby the ?13C and ?18O values of fossil tooth enamel can be measured in situ using laser ablation techniques. The laser heats the sample and forms CO2 from structural carbonate apatite. The ?18O values obtained with this method are equal to those of the phosphate oxygen due to the high temperature of reaction during ablation. Analytical

Thure E. Cerling; Zachary D. Sharp

1996-01-01

365

FINAL REPORT. WASTE VOLUME REDUCTION USING SURFACE CHARACTERIZATION AND DECONTAMINATION BY LASER ABLATION  

EPA Science Inventory

Laser ablation was studied as a method for removing contaminated surface layers from concrete. The objectives of this research were to determine the mechanism and efficacy of laser ablation, to understand the chemistry of contaminated concrete surfaces, and to chemically and phys...

366

High rate deep channel ablative formation by picosecond-nanosecond combined laser pulses  

Microsoft Academic Search

Temporally profiled pulsed radiation of the Nd:YAG laser was applied to drilling and micromachining of ceramics, steel, and CVD diamond, demonstrating one or two orders of magnitude enhancement of ablation rates compared to conventional pico- and nanosecond-pulsed ablation at the same energy density. The developed laser system delivered combined pulses consisting of a picosecond pulse train followed by a nanosecond

S. M. Klimentov; S. V. Garnov; T. V. Kononenko; V. I. Konov; P. A. Pivovarov; F. Dausinger

1999-01-01

367

Clinical outcomes following percutaneous magnetic resonance image guided laser ablation of symptomatic uterine fibroids  

Microsoft Academic Search

BACKGROUND: Fibroids are common benign tumours of the uterus. Percutaneous magnetic resonance (MR) image guided laser ablation provides a minimally invasive, day-case alternative to surgery for the treatment of symptomatic fibroids. METHODS: Women with symptomatic fibroids wishing to avoid surgery were treated with laser ablation. MR thermal mapping ensured that maximal safe energy was applied. Fibroid volume was measured at

J. T. Hindley; P. A. Law; M. Hickey; S. C. Smith; D. L. Lamping; W. M. W. Gedroyc; L. Regan

2002-01-01

368

Precision patterning of conductive polymer nanocomposite using a laser-ablated thin film  

Microsoft Academic Search

We introduce a simple, reliable and low-cost microfabrication technique utilizing laser ablation of a thin polymer film to pattern polymer nanocomposite at a high resolution. A conductive composite of poly(dimethylsiloxane) (PDMS) and carbon nanotubes (CNTs) was selected due to their wide use in microelectromechanical systems (MEMS) and unique properties including flexibility and piezoresistivity. To pattern nanocomposite, an excimer laser ablated

Chao-Xuan Liu; Jin-Woo Choi

2012-01-01

369

Laser ablation-induced spectral plasma characteristics in optical far- and near fields  

SciTech Connect

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 experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of {approx}200 nm thickness on quartz substrate as a target. The far-field ablation is affected under tight focusing conditions, wherein nanosecond laser pulses of 532 nm wavelength are focused to laser focal spot diameters of {approx}7 and 1.5 {mu}m. The measured results show that the ablation-induced plasma from sub-10 {mu}m ablation craters exhibits complex three-dimensional behavior, leading to greatly reduced laser-plasma interaction and an order of magnitude shorter plasma lifetime. Nanosecond laser pulses of 532 nm wavelength are also coupled to a pulled fiber based near-field scanning optical microscopy probe. Due to the sharp tip presence in close proximity of the ablation craters, entirely different plasma evolution behavior is observed, highlighted by orders of magnitude shorter plasma lifetime and strongly directional material ejection. The ablation-induced plasma from reduced lateral crater dimensions both in far- and near-field shows improved contrast of atomic transition signals with respect to the wide-spectrum background, hence confirming the potential for laser-induced breakdown spectroscopy with high spatial resolution.

Hwang, David J.; Jeon, Hojeong; Grigoropoulos, Costas P. [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Yoo, Jong; Russo, Richard E

2008-07-01

370

Characterization of high performance polymers transferred by resonant infrared laser ablation  

Microsoft Academic Search

A polyamide imide and a polymeric precursor to polyimide have both been successfully transferred using resonant infrared laser ablation. Additionally a random copolymer mixture, possessing structural features common to polyimide and polyamide imide, was readily transferred using resonant infrared laser ablation. The materials are transferred with local structure intact as evidenced by Fourier transform infrared spectroscopy studies. The deposition rates

Nicole L. Dygert; Richard F. Haglund Jr.

2008-01-01

371

Surface modification of biomaterials by pulsed laser ablation deposition and plasma\\/gamma polymerization  

Microsoft Academic Search

Surface modification of stainless-steel was carried out by two different methods: pulsed laser ablation deposition (PLAD) and a combined plasma\\/gamma process. A potential application was the surface modification of endovascular stents, to enhance biocompatibility. The pulsed laser ablation deposition process, had not been previously reported for modifying stents and represented a unique and potentially important method for surface modification of

Kaustubh R. Rau

2000-01-01

372

Ablation thresholds in ultrafast laser micro-machining of common metals in air  

Microsoft Academic Search

In the current work ablation of metal targets in air with femtosecond laser pulses is studied. The laser pulses used for the study were 775 nm in wavelength, 150 fs in pulse duration and the repetition rate was 100 Hz. Ablation thresholds have been measured for a number of metals including stainless steel (0.1600 J\\/cm

Paul Mannion; Jonathan Magee; Edward Coyne; Gerard M. O'Connor

2003-01-01

373

Improved Analytical Characterization of Solid Waste-Forms by Fundamental Development of Laser Ablation Technology  

Microsoft Academic Search

Laser ablation (LA) with inductively coupled plasma mass spectrometry (ICP-MS) has been demonstrated as a viable technology for sample characterization within the EM complex. Laser ablation systems have been set up at the Hanford Site, Savannah River Plant, the Pu immobilization program (MD), Los Alamos, and at numerous other DOE facilities. Characterization of elemental and isotopic chemical constituents is an

Richard E

2000-01-01

374

Mechanism of water augmentation during IR laser ablation of dental enamel  

Microsoft Academic Search

Background and Objectives: The mechanism of water augmentation during IR laser ablation of dental hard tissues is controversial and poorly understood. The in- fluence of an optically thick applied water layer on the laser ablation of enamel was investigated at wavelengths in which water is a primary absorber and the magnitude of absorption varies markedly. Study Design\\/Materials and Methods: Q-switched

Daniel Fried; Nahal Ashouri; Thomas Breunig; Ramesh Shori

2002-01-01

375

Theoretical determination of the ablation rate of metals in multiple-nanosecond laser pulses irradiation regime  

NASA Astrophysics Data System (ADS)

A detailed understanding of the physical determinants of the ablation rate in multiple nanosecond laser pulses regime is of key importance for technological applications such as patterning and pulsed-laser deposition. Here, theoretical modeling is employed to investigate the ablation of thick metallic plates by intense, multiple nanosecond laser pulses. A new photo-thermal model is proposed, in which the complex phenomena associated to the ablation process are accounted for as supplementary terms of the classical heat equation. The pulsed laser ablation in the nanosecond regime is considered as a competition between thermal vapourization and melt ejection under the action of the plasma recoil pressure. Computer simulations using the photo-thermal model presented here and the comparison of the theoretical results with experiment indicate two different mechanisms that contribute to the decrease of the ablation efficiency. First, during the ablation process the vapour/plasma plume expanding above the irradiated target attenuates the laser beam that reaches the sample, leading to a marked decrease of the ablation efficiency. Additional attenuation of the laser beam incident on the sample is produced due to the heating of the plasma by the absorption of the laser beam into the plasma plume. The second mechanism by which the ablation efficiency decreases consists of the reduction of the incident laser intensity with the lateral area, and of the melt ejection velocity with the depth of the hole.

Stafe, Mihai; Negutu, Constantin; Popescu, Ion M.

2007-05-01

376

Femtosecond laser ablation from dielectric materials: Comparison to arc discharge erosion  

Microsoft Academic Search

After explosive ablation from sapphire crystals by linearly polarised laser pulses, regular structures are observed on the bottom of the ablation pit. These structures do not comply with conventional ripple patterns. Instead, they more nearly resemble wickerwork, aligned perpendicular to the laser beam polarisation. A similar morphology is obtained by arc discharge erosion at AgCdO electrodes, suggesting that an explosive

M. Henyk; N. Vogel; D. Wolfframm; A. Tempel; J. Reif

1999-01-01

377

Ultra-fast movies of thin-film laser ablation  

NASA Astrophysics Data System (ADS)

Ultra-short-pulse laser irradiation of thin molybdenum films from the glass substrate side initiates an intact Mo disk lift off free from thermal effects. For the investigation of the underlying physical effects, ultra-fast pump-probe microscopy is used to produce stop-motion movies of the single-pulse ablation process, initiated by a 660-fs laser pulse. The ultra-fast dynamics in the femtosecond and picosecond ranges are captured by stroboscopic illumination of the sample with an optically delayed probe pulse of 510-fs duration. The nanosecond and microsecond delay ranges of the probe pulse are covered by an electronically triggered 600-ps laser. Thus, the setup enables an observation of general laser ablation processes from the femtosecond delay range up to the final state. A comparison of time- and space-resolved observations of film and glass substrate side irradiation of a 470-nm molybdenum layer reveals the driving mechanisms of the Mo disk lift off initiated by glass-side irradiation. Observations suggest that a phase explosion generates a liquid-gas mixture in the molybdenum/glass interface about 10 ps after the impact of the pump laser pulse. Then, a shock wave and gas expansion cause the molybdenum layer to bulge, while the enclosed liquid-gas mixture cools and condenses at delay times in the 100-ps range. The bulging continues for approximately 20 ns, when an intact Mo disk shears and lifts off at a velocity of above 70 m/s. As a result, the remaining hole is free from thermal effects.

Domke, Matthias; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2012-11-01

378

An observation of ablation effect of soft biotissue by pulsed Er:YAG laser  

NASA Astrophysics Data System (ADS)

Because of the unique properties with regard to the absorption in organic tissue, pulsed Er:YAG laser has found most interest for various application in medicine, such as dermatology, dentistry, and cosmetic surgery. However, consensus regarding the optimal parameters for clinical use of this tool has not been reached. In this paper, the laser ablation characteristics of soft tissue by Er:YAG laser irradiation was studied. Porcine skin tissue in vitro was used in the experiment. Laser fluences ranged from 25mJ/mm2 to 200mJ/mm2, repetition rates was 5Hz, spot sizes on the tissue surface was 2mm. The ablation effects were assessed by the means of optical microscope, ablation diameters and depths were measured with reading microscope. It was shown that the ablation of soft biotissue by pulsed Er:YAG laser was a threshold process. With appropriate choice of irradiation parameters, high quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam can be achieved. The curves of ablation crater diameter and depth versus laser fluence were obtained, then the ablation threshold and ablation yield were calculated subsequently, and the influence of the number of pulses fired into a crater on ablation crater depth was also discussed.

Zhang, Xianzeng; Xie, Shusen; Ye, Qing; Zhan, Zhenlin

2007-03-01

379

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Doppler diagnostics of nonstationary mass removal upon laser ablation of biotissues  

NASA Astrophysics Data System (ADS)

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 CO2 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.

Dmitriev, A. K.; Kortunov, V. N.; Ul'yanov, V. A.

2001-04-01

380

Hard tissue ablation with a spray-assisted mid-IR laser.  

PubMed

The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a spray (dry ablation). In order to identify dominant ablation mechanisms, transient acoustic waves were compared to ablation thresholds and the volume of material removed. The ablation profile and depth were measured using optical coherence tomography (OCT). Irregular surface modification, charring and peripheral cracks were associated with dry ablation, whereas craters for spray samples were relatively clean without thermal damage. In spite of a 60% higher ablation threshold for spray associated irradiations owing to water absorption, acoustic peak pressures were six times higher and ablation volume was up to a factor of 2 larger compared to dry ablation. The enhanced pressure and ablation performance of the spray-assisted process was the result of rapid water vaporization, material ejection with recoil stress, interstitial water explosion and possibly liquid-jet formation. With water cooling and abrasive/disruptive mechanical effects, the spray ablation can be a safe and efficient modality for dental treatment. PMID:18065837

Kang, H W; Rizoiu, I; Welch, A J

2007-11-23

381

Laser ablation of dental calculus at 400 nm using a Ti:sapphire laser  

NASA Astrophysics Data System (ADS)

A Nd:YAG laser-pumped, frequency-doubled Ti:sapphire laser is used for selective ablation of calculus. The laser provides <=25 mJ at 400 nm (60-ns pulse width, 10-Hz repetition rate). The laser is coupled into an optical multimode fiber coiled around a 4-in.-diam drum to generate a top-hat output intensity profile. With coaxial water cooling, this is ideal for efficient, selective calculus removal. This is in stark contrast with tightly focused Gaussian beams that are energetically inefficient and lead to irreproducible results. Calculus is well ablated at high fluences >=2J/cm2 stalling occurs below this fluence because of photobleaching. Healthy hard tissue is not removed at fluences <=3 J/cm2.

Schoenly, Joshua E.; Seka, Wolf; Rechmann, Peter

2009-02-01

382

Tracheal laceration after laser ablation of nodular goitre†  

PubMed Central

A tracheal perforation was discovered after Nd-YAG laser thermal ablation (LTA) of a thyroid nodule. The LTA is a relatively new method of treatment of thyroid nodules, which consists of delivering laser energy into the thyroid by means of two optical fibres. The patient presented with a multinodular goitre and initially refused surgery, then underwent an LTA of a thyroid nodule. Fifty days after the procedure she started to have symptoms related to a tracheal stenosis and, after tracheoscopy, a tracheal perforation was diagnosed and she underwent a total thyroidectomy plus tracheal repair. The results of the histological examination revealed a goitre with a focal area of papillary carcinoma. This particular complication is likely the first of its kind to be described after the LTA of a thyroid nodule.

Di Rienzo, Gaetano; Surrente, Corrado; Lopez, Camillo; Quercia, Rosatea

2012-01-01

383

Large area uniform nanostructures fabricated by direct femtosecond laser ablation.  

PubMed

An approach for fabricating large area uniform nanostructures by direct femtosecond (fs) laser ablation is presented. By the simple scanning technique with appropriate irradiation conditions, arbitrary size of uniform, complanate nano-grating, nano-particle, and nano-square structures can be produced on wide bandgap materials as well as graphite. The feature sizes of the formed nanostructures, which can be tuned in a wide range by varying the irradiation wavelength, is about 200 nm with 800 nm fs laser irradiation. The physical properties of the nano-structured surfaces are changed greatly, especially the optical property, which is demonstrated by the extraordinary enhancement of light transmission of the treated area. This technique is efficient, universal, and environmentally friendly, which exhibits great potential for applications in photoelectron devices. PMID:19582029

Huang, Min; Zhao, Fuli; Cheng, Ya; Xu, Ningsheng; Xu, Zhizhan

2008-11-10

384

Optical Thomson scatter from a laser-ablated magnesium plume  

SciTech Connect

We have carried out an optical Thomson scatter study of a KrF laser-ablated Mg plume. The evolution of the electron temperature and density at distances 2-5 mm from the target surface has been studied. We have observed that the electron density falls more rapidly than the atomic density and believe that this is a result of rapid dielectronic recombination. A comparison of the electron density profile and evolution with simple hydrodynamic modeling indicates that there is a strong absorption of the laser in the plasma vapor above the target, probably due to photoionization. We also conclude that an isothermal model of expansion better fits the data than an isentropic expansion model. Finally, we compared data obtained from Thomson scatter with those obtained by emission spectroscopy under similar conditions. The two sets of data have differences but are broadly consistent.

Delserieys, A.; Khattak, F. Y.; Lewis, C. L. S.; Riley, D. [School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom)

2009-10-15

385

Laser machining of specially designed photopolymers: photochemical ablation mechanism  

NASA Astrophysics Data System (ADS)

Photopolymers based on the triazeno chromophore group (-NequalsN-N<) have been developed. The absorption properties can be tailored for a specific irradiation wavelength (e.g. 308 cm XeCl laser). The photochemical exothermic decomposition yields high energetic gaseous products which are not contaminating the surface. The polymer can be structured with high resolution. No debris has been found around the etched corners. Maximum ablation rates of about 3 micrometers / pulse were achieved due to the dynamic absorption behavior (bleaching during the pulse). No physical or chemical modifications of the polymer surface could be detected after irradiation at the tailored absorption wavelength, whereas irradiation at different wavelengths resulted in modified (physical and chemical) surfaces. The etching of the polymer starts and ends with the laser pulse, shown by ns-interferometry, confirming that the acting mechanism is mainly photochemical. TOF-MS revealed fragments which are also totally compatible with a photochemical decomposition mechanism.

Lippert, Thomas K.; Dickinson, J. Thomas; Langford, Steve C.; Furutani, H.; Fukumura, H.; Masuhara, Hiroshi M.; Kunz, Thilo; Wokaun, Alexander J.

1998-05-01

386

Endometrial ablation using SideFire laser fiber  

NASA Astrophysics Data System (ADS)

The first successful report using the neodymium:yttrium-aluminum-garnet (Nd:YAG) Laser to control hypermenorrhea was reported in 1981. Variations on the treatment technique have been attempted to improve the amenorrhea rate. Reports using the Nd:YAG laser with the blanching or non-touch technique seem to result in a better outcome and higher rate of total amenorrhea than using the dragging technique. Due to the report of improved rates of amenorrhea when using the blanching technique and the Nd:YAG laser, a fiber was developed to direct the laser energy at right angles to the axis of the fiber, therefore allowing a total treatment of the entire uterus in a perpendicular fashion. The theoretic benefit of this would be a more complete and predictable destruction of the endometrial lining, avoiding fluid overload by coagulating and sealing of the vessels and lymphatic. After a follow-up of 12 to 36 months, 56 of the 60 patients (93%) who underwent complete endometrial ablation with the SideFireTM technique had excellent results. Total absolute amenorrhea resulted in 50 patients (83%). Contrary to earlier reports, using the rollerball electrode, this procedure technique resulted in no decrease in results in younger patients. In conclusion, this seems to be a reasonable alternative which offers improved results when compared to previously available methods using electrosurgery or the Nd:YAG laser without the use of the SideFireTM device.

Everett, Royice B.

1996-05-01

387

Laser Ion Source Project at IGISOL  

NASA Astrophysics Data System (ADS)

The application of laser ionisation is being developed for the IGISOL mass separator facility in Jyväskylä, Finland. The conceived laser ion source will have two independent pulsed laser systems based on all solid-state lasers and dye lasers for maximal coverage of ionisation schemes throughout the periodic table. A laser ion source trap, LIST, method will be pursued for optimal selectivity.

Nieminen, A.; Moore, I. D.; Billowes, J.; Campbell, P.; Flanagan, K. T.; Geppert, Ch.; Huikari, J.; Jokinen, A.; Kessler, T.; Marsh, B.; Penttilä, H.; Rinta-Antila, S.; Tordoff, B.; Wendt, K. D. A.; Äystö, J.

2005-04-01

388

Photonic Doppler velocimetry of laser-ablated ultrathin metals  

SciTech Connect

Obtaining velocity information from the interaction of a laser pulse on a metal layer provides insight into the rapid dynamics of material removal and plasma plume physics during ablation. A traditional approach involves using a velocity interferometer system for any reflector (VISAR) on a reflective metal surface. However, when the target is a thin metal layer, the cohesion of the surface is quickly lost resulting in a large spread of particle velocities that cannot be easily resolved by VISAR. This is due to material ejection 'confusing' the VISAR measurement surface, effectively washing out the spatial fringe visibility in the VISAR interferometer. A new heterodyne-based optical velocimeter method is the photonic Doppler velocimeter (PDV). Because PDV tracks motion in a frequency encoded temporal electro-optical signal, velocity information is preserved and allows for multiple velocity components to be recorded simultaneously. The challenge lies in extracting PDV velocity information at short (nanosecond) laser ablation time scales with rapidly varying heterodyne beats by using electronic, optical, and analytical techniques to recover the velocity information from a fleeting signal. Here we show how we have been able to obtain velocity information on the nanosecond time scale and are able to compare it to hydrodynamic simulations. Also, we examine refinements to our PDV system by increasing the bandwidth, utilizing different probes, and sampling different analysis techniques.

Valenzuela, A. R.; Rodriguez, G.; Clarke, S. A.; Thomas, K. A. [Material Physics and Applications Division, Los Alamos National Laboratory, MS K771, Los Alamos, New Mexico 87545 (United States); Weapons Systems Engineering Division, Los Alamos National Laboratory, MS P950, Los Alamos, New Mexico 87545 (United States)

2007-01-15

389

Ablation algorithms and corneal asphericity in myopic correction with excimer lasers  

NASA Astrophysics Data System (ADS)

The purpose of this work is studying a corneal asphericity change after a myopic refractive correction by mean of excimer lasers. As the ablation profile shape plays a key role in the post-op corneal asphericity, ablation profiles of recent lasers should be studied. The other task of this research was to analyze operation (LASIK) outcomes of one of the lasers with generic spherical ablation profile and to compare an asphericity change with theoretical predictions. The several correction methods, like custom generated aspherical profiles, may be utilized for mitigation of unwanted effects of asphericity change. Here we also present preliminary results of such correction for one of the excimer lasers.

Iroshnikov, Nikita G.; Larichev, Andrey V.; Yablokov, Michail G.

2007-08-01

390

Influence of sample surface condition on chemical analysis using laser ablation inductively coupled plasma atomic emission spectroscopy  

Microsoft Academic Search

The influence of sample surface condition on chemical analysis was investigated when using laser ablation sampling with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The ablated mass quantity and composition were found to be significantly different from original vs. pre-ablated surfaces. The ablated mass quantity from original surfaces was much greater than that from pre-ablated surfaces, and the ablation rate

Xianglei Mao; Richard E. Russo; Wing-Tat Chan

1997-01-01

391

Precision shaping of a diamond surface by using interferometrically controlled laser-ablation method  

NASA Astrophysics Data System (ADS)

A novel method for figuring and polishing diamond surfaces is described. It is a three step process, consisting of 1) a diffusion smoothing step using carbon reaction with certain materials at elevated temperatures, 2) a laser polishing and figuring step where UV laser ablation actively coupled with in situ interferometry provides the desired surface finish. The fist step of the process uses carbon diffusion into a hot iron surface to achieve an initial, relatively smooth surface of the as grown chemical vapor deposited (CVD) diamond surface. The technique can be used on any size CVD diamond and may be applied to curved surfaces. The second step, excimer laser ablation, is the backbone of the proposed method. By using an in situ, interferometric surface measuring and monitoring capability, diamond material may be removed from the surface in an accurately controlled manner, both in depth and width. The method is conceptually similar to single point diamond turning for figuring the optical surfaces of metal mirrors. The last step uses the properties of ion beam technology to change the top layer of the diamond surface into a soft and easily polishable amorphous carbon. The final surface finish of the accurately figured surface is obtained by conventional, high quality polishing techniques.

Holly, Sandor; Ralchenko, Victor G.; Pimenov, Sergej M.; Kononenko, Taras V.

1998-10-01

392

Myocardial tissue ablation by single high-energy laser pulses for ELR and TMR  

NASA Astrophysics Data System (ADS)

The objective of this study is to compare the ablation sites induced by two different laser and application systems for myocardial laser revascularization. One system used was an 800 W CO2 laser, which is clinically established for transmyocardial laser revascularization (TMR). The second system was a self-designed Holmium laser emitting single high energy pulses for the minimal invasive approach of endocardial laser revascularization (ELR), whereby the laser light is transmitted via optical fiber into the left ventricle to ablate the myocardial channels from the inside. The laser energy was applied to Polyacrylamide (PAA) as transparent tissue phantom and in water as blood phantom. The ablation dynamics were investigated by high speed flash photography recording a picture series of a single event. Reperfused ex- vivo porcine hearts were treated to quantify differences in the thermal-mechanical damage ranges by polarization light microscopy. Ablation dynamics in water revealed oscillatory changes of the axial length of the steam bubbles between 3 mm and 12 mm during the CO2 laser pulse. For the Holmium laser pulse a maximal axial and lateral length of 5 mm was observed. The lateral dimensions of the bubbles were maximal 1 mm with the CO2- and 3.5 mm with the Holmium laser system. In PAA bubbles also collapse during the laser pulse which affects the size of the ablated channels. Using 12 J Holmium laser pulses for ablation of PAA, channel depths around 7 mm were found. Single Holmium laser pulses demonstrate ablations comparable in size and thermal- mechanical collateral damage to those achieved with the standard CO2 laser. The results are very encouraging for single pulse ELR and demonstrate the potential of a catheter based minimal invasive procedure for laser heart reperfusion.

Theisen, Dirk; Brinkmann, Ralf; Stubbe, Hans-Martin; Birngruber, Reginald

1999-02-01

393

TOF MS studies concerning the synthesis of BN and B-C-N nanaostructured materials by laser ablation  

Microsoft Academic Search

Time-of-flight mass spectroscopy (TOF MS) spectra of ions ablated from BN-ceramic, amorphous carbon, graphite and fullerene-60 targets were recorded at different experimental conditions. It was found that the TOF MS spectra significantly simplify as the energy density of the laser radiation was increased, and show temporal evolution as the distance between the target surface and work area of TOF MS

Dachun Huang; Vladimir I. Makarov; Arturo Hidalgo; Brad R. Weiner; Gerardo Morell

2006-01-01

394

In situ petrographic thin section UPb dating of zircon, monazite, and titanite using laser ablation-MC-ICP-MS  

Microsoft Academic Search

A laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) analytical protocol is used to date accessory minerals (zircon, monazite, and titanite) at high spatial resolution (5-40 [mu]m) using standard petrographic thin sections. The MC-ICP-MS instrument is equipped with a modified collector array containing a combination of Faraday buckets and multiple ion counters, which produces accurate and precise geochronological data using

Antonio Simonetti; Larry M. Heaman; Thomas Chacko; Neil R. Banerjee

2006-01-01

395

Local thermal equilibrium plasma modeling for analyses of gas-phase reactions during reactive-laser ablation  

Microsoft Academic Search

Number densities of atoms, ions, and molecules in plasmas composed of two-element vapor-gas mixtures have been computed assuming local thermal equilibrium. The calculations include the formation of diatomic molecules by chemical reactions between both elements. Temperature range and total number densities of elements have been set to values characteristic for plasmas generated by pulsed-laser ablation of solid targets under low-pressure

J. Hermann; C. Dutouquet

2002-01-01

396

Isotopic fractionation effects under laser ablation of silicon from pure silicon and silicon oxide targets  

NASA Astrophysics Data System (ADS)

The isotopic and elemental composition of bodies in the solar system is of great interest due to the information it will yield as to the formation and evolution of the bodies and the solar system in general. One possible method to quickly measure isotopic ratios on airless bodies is to use laser ablation coupled with ion mass spectrometry at a stand off distance. Specifically a Nd:YAG laser operating at 1.064mum was used to ablate the target and the resulting plasma was measured with a time of flight mass spectrometer (TOFMS) placed >3m away from the target. The detector used was a Ceramic Channel Electron Multiplier (CCEM) with an Electro-Static Analyzer (ESA) for ion energy selection. This set up allowed the measurement of mass spectrums from a variety of targets with ion energies running from 25 eV to 1 KeV created by laser energy densities from 21 to 77 J/cm2. Because of a non-linear response of the CCEM, the relative amounts of the different isotopes could not be accurately compared, as the more abundant isotopes flux rate causes the CCEM to respond with a lower gain per particle then less abundant isotopes, yielding an apparent enhancement in the minor isotopes. This saturation effect was proven by comparing the ion flux measured by the CCEM to that measured by a faraday cup from an aluminum target. However, by making comparisons between the flux measured by the faraday cup and the changes in isotopic ratios observed in the CCEM data for silicon targets, a trend appears which is independent of ion energy or laser fluence, indicating that any fractionation is caused by a process which is independent of laser fluence and ion energy. Further, by making comparisons between the measured major isotope flux and the changes in isotopic ratios for both silicon and SiO2, another trend emerges, namely independence from materials. Finally, several changes must be made to the proposed instrument to make it viable for exploration purposes, most importantly a detector with a wider dynamic range in incident flux must be chosen to make accurate measurements of isotopic ratios.

Shappirio, Mark

397

Numerical Model of Laser Ablation and Plasma Expansion for Ultrashort Laser Pulses  

NASA Astrophysics Data System (ADS)

Laser induced plasma spectroscopy (LIPS) is a promising technique for the chemical analysis of materials, which receives presently much attention. The technique is based on the measurement of lines intensities of the different chemical elements heated by the surrounding plasma. We have developed a one-dimensional Lagrangian fluid model to improve our understanding of the various processes involved in LIPS, namely: of laser ablation, of the subsequent plasma expansion, and of the ambient gas shock wave dynamics, which is strongly coupled to the plasma. The calculated ablation depth and the ablation threshold fluence for simple metals are in agreement with experiments (i.e., less than 1 J/cm2 for the threshold fluence). The model also shows a stage of explosive boiling leading to the ejection of high-density fluid agglomerations. In the case of aluminum, for a fluence of the order of 10 J/cm_2, the model indicates that the expansion of the ablated plasma is generally limited to a few mm and has practically stopped after about 10 microseconds. At this time, the axial distribution of the ablated matter is not at all homogeneous. The temperature can vary from ~0.1 eV to ~1 eV while the gas particle density can vary from ~10^18 cm-3 to ~10^19 cm-3.

Laville, Stéphane; Vidal, Frangois; Chaker, Mohamed; Barthilemy, Olivier; Johnston, Tudor Wyatt; Le Drogoff, Boris; Margot, Jo'"Elle; Sabsabi, Mohamad

2000-10-01

398

Influence of the liquid environment on the products formed from the laser ablation of tin  

NASA Astrophysics Data System (ADS)

Tin targets immersed in ethanol and distilled water were ablated using a UV pulsed laser. The ablated products were investigated with transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. For ablation in both liquids, the size distribution of the produced particles was bimodal, with particles having diameters of ˜10 nm and ˜1 ?m. Formation mechanisms that caused the bimodal distribution are suggested. Ablation in ethanol resulted in nanoparticles that were found to be single crystals of tin coated with tin hydroxide (Sn(OH)2) while ablation in water yielded nanoparticles that were polycrystalline tin dioxide (SnO2) throughout.

Musaev, O. R.; Driver, M. S.; Sutter, E. A.; Caruso, A. N.; Wrobel, J. M.; Kruger, M. B.

2013-02-01

399

Influence of the liquid environment on the products formed from the laser ablation of tin  

NASA Astrophysics Data System (ADS)

Tin targets immersed in ethanol and distilled water were ablated using a UV pulsed laser. The ablated products were investigated with transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. For ablation in both liquids, the size distribution of the produced particles was bimodal, with particles having diameters of ˜10 nm and ˜1 ?m. Formation mechanisms that caused the bimodal distribution are suggested. Ablation in ethanol resulted in nanoparticles that were found to be single crystals of tin coated with tin hydroxide (Sn(OH)2) while ablation in water yielded nanoparticles that were polycrystalline tin dioxide (SnO2) throughout.

Musaev, O. R.; Driver, M. S.; Sutter, E. A.; Caruso, A. N.; Wrobel, J. M.; Kruger, M. B.

2013-11-01

400

Measurements of Ablation Pressure and Mass Ablation Rate Using a Target Pendulum and a Thin Foil Target at 10 mu M Laser Wavelength.  

National Technical Information Service (NTIS)

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 ...

H. Daido R. Tateyama K. Ogura A. Tsujimoto H. Fujita

1981-01-01

401

Bone Ablation at 2.94 mm Using the Free-Electron Laser and Er:YAG Laser  

NASA Astrophysics Data System (ADS)

Bone Ablation at 2.94 microns Using the Free-Electron Laser and Er:YAG Laser in Perfluorocarbon Compounds B. Ivanov^1, A. M. Hakimian^1, G. M. Peavy^2, R. F. Haglund, Jr.1 1Department of Physics and Astronomy, W. M. Keck Foundation Free-Electron Laser Center, Vanderbilt University, Nashville, TN 37235 2Beckman Laser Institute and Medical Clinic, College of Medicine, University of California, Irvine, CA 92612 We report studies on the efficiency of mid-IR laser ablation of cow cortical bone using the Vanderbilt free-electron laser (FEL), when irrigating the ablation zone with an inert and biocompatible perfluorocarbon compounds (PFC). At 2.94 microns, the bone matrix (mainly by water) absorbs the radiation while the PFCs transmit this wavelength, dissipate heat and acoustical stress, and prevent carbonization of the bone sample. The ablation rate, as a function of laser fluence, scanning speed and the type of PFC, was investigated. The laser fluence was estimated to be 5 J/cm^2 - 100 J/cm^2 with a laser focal spot diameter of 160 microns 500 microns and a scanning speed of 40 microns/s 2960 microns/s. The ablation rate was estimated from scanning electron microscopy to be 0.5 mm/s 2.4 mm/s. Comparisons of ablation rates with the FEL and a Er:YAG laser at 2.94 microns are being evaluated.

Ivanov, Borislav; Hakimian, Arman; Peavy, G. M.; Haglund, Richard

2002-03-01

402

Solids sampling using double-pulse laser ablation inductivelycoupled plasma mass spectrometry  

SciTech Connect

This paper describes the use of double-pulse laser ablation to improve ICP-MS internal precision (temporal relative standard deviation, %TRSD). Double pulse laser ablation offers reduced fractionation, increased sensitivity, and improved signal to noise ratios. The first pulse is used to ablate a large quantity of mass from the sample surface. The second pulse is applied with a variable time delay after the first pulse to break the ablated mass into a finer aerosol, which is more readily transported to and digested in the ICP-MS.

Gonzalez, Jhanis; Liu, Chunyi; Yoo, Jong; Mao, Xianglei; Russo,RickRick

2003-07-01

403

Volatilization of high molecular weight DNA by pulsed laser ablation of frozen aqueous solutions.  

PubMed

DNA has been volatilized by pulsed laser ablation of a thin film of a frozen aqueous DNA solution. The target film was irradiated in vacuum by a pulsed laser at power densities sufficient to ablate the ice matrix. The expanding ablated water vapor entrained embedded DNA molecules and expelled them into the gas phase. Ejection of DNA molecules as large as 410 kilodaltons was verified by collection of the ablation products and subsequent mass analysis by polyacrylamide gel electrophoresis with autoradiographic detection. PMID:2595370

Nelson, R W; Rainbow, M J; Lohr, D E; Williams, P

1989-12-22

404

Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes  

SciTech Connect

Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

Lopez-Arias, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Unidad Asociada Departamento de Quimica Fisica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid, and Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain); Oujja, M.; Sanz, M.; Castillejo, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T. [Institute of Electronics, Uzbekistan Academy of Sciences, Akademgorodok, 33, Dormon Yoli Street, Tashkent 100125 (Uzbekistan)

2012-02-15

405

The direct measurement of ablation pressure driven by 351-nm laser radiation  

SciTech Connect

The instantaneous scaling of ablation pressure to laser intensity is directly inferred for ramp compression of diamond targets irradiated by 351-nm light. Continuously increasing pressure profiles from 100 to 970 GPa are produced by direct-drive laser ablation at intensities up to 7 x 10{sup 13} W/cm{sup 2}. The free-surface velocity on the rear of the target is used to directly infer the instantaneous ablation-pressure profile at the front of the target. The laser intensity on target is determined by laser power measurements and fully characterized laser spots. The ablation pressure is found to depend on the laser intensity as P(GPa)=42({+-}3)[I(TW/cm{sup 2})]{sup 0.71({+-}0.01)}.

Fratanduono, D. E. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Mechanical Engineering, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Boehly, T. R. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Celliers, P. M.; Eggert, J. H.; Smith, R. F.; Hicks, D. G.; Collins, G. W. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Barrios, M. A. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Physics and Astronomy, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Meyerhofer, D. D. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Mechanical Engineering, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Physics and Astronomy, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States)

2011-10-01

406

Cation Engineering of Cu-ferrite Films Deposited by Alternating Target Laser Ablation Deposition  

SciTech Connect

Epitaxial copper ferrite thin films were deposited on MgO substrates by the alternating target laser ablation deposition method. A series of films was studied to explore the impact of oxygen operating pressure, substrate temperature, and the ratio of laser shots incident on each target upon the magnetic, structural, and atomic structural properties. The highest saturation magnetization, 2800?G, was achieved at a 90?mTorr oxygen pressure and at 650? C for the substrate temperature. This value is 65% higher than the room temperature magnetization for bulk equilibrium samples. The inversion parameter was measured by extended x-ray absorption fine structure analysis. The sample having the highest saturation magnetization had a corresponding inversion parameter (percentage of Cu ion octahedral site occupancy) of 51.5% compared with the bulk value of 85%.

Yang,A.; Chen, Z.; Islam, S.; Vittoria, C.; Harris, V.

2008-01-01

407

Laser ablation induced vapor plume expansion into a background gas. II. Experimental analysis  

Microsoft Academic Search

Laser ablation of copper with a 4 ns laser pulse at 1064 nm was studied with a series of synchronized shadowgraph (100 fs laser pulses at 400 nm) and emission images (spectral line at 515 nm). Data were obtained at two laser pulse energies (10 and 30 mJ) and in three background gases (He, Ne, and Ar) at atmospheric pressure.

Sy-Bor Wen; Xianglei Mao; Ralph Greif; Richard E. Russo

2007-01-01

408

Evolution and imaging of nanoparticles observed in laser ablated carbon plume  

Microsoft Academic Search

We report evidence of nanoparticles formation in laser ablated carbon plasma created by irradiating a graphite target with nanosecond neodymium doped yttrium aluminum garnet laser. The temporal evolution and spatial distribution of C2 molecules in the plasma is studied using optical emission spectroscopy, dynamic imaging and laser induced fluorescence techniques. The laser induced fluorescence spectrum and imaging of C2 fluorescence

Dheerendra Yadav; Varun Gupta; Raj K. Thareja

2009-01-01

409

Fabrication of gold nanoparticles in water by laser ablation technique and their characterization  

NASA Astrophysics Data System (ADS)

A colloidal solution of gold nanoparticles in deionized nanopure water was produced by laser ablation technique without the use of any chemical/surfactant. Spectral characterization and morphological studies of these nanoparticles were carried out by UV-Vis Spectroscopy and Scanning Electron Microscopy, respectively. A number of variables of the ablating laser pulse have been used to control the size of the fabricated nanoparticles. Excellent correlation between ablating laser pulse parameter and optical and morphological parameters of the gold colloids were obtained. The peak of the extinction spectra shows a monotonic blue shift for laser fluence of 410 J/cm2 and above. Below this the extinction peak remains fairly constant in wavelength. Blue shifts of the extinction spectra were also observed with increasing re-ablation time of previously ablated gold colloids. Possible explanations of all these observations are discussed.

Haider, A. F. M. Y.; Sengupta, S.; Abedin, K. M.; Talukder, Aminul I.

2011-11-01

410

Control of Plasma and Cavitation Bubble in Liquid-Phase Laser Ablation Using Supersonic Waves  

NASA Astrophysics Data System (ADS)

We examined the effects of a supersonic wave on laser-induced plasma and ablation-induced cavitation bubbles in liquid-phase laser ablation. The effect of the supersonic wave on laser-induced plasma was the change in the optical emission intensity. We observed an intense optical emission when the ablation target was irradiated with a laser pulse at a negative phase of the sound pressure of the supersonic wave. The effect of the supersonic wave on ablation-induced cavitation bubbles was the repetitive formation and collapse of the bubbles at the same frequency as the supersonic wave. The ablation-induced cavitation bubbles served as a ``seed'', and the repetitive formation and collapse of the cavitation bubbles were driven by the sound pressure of the supersonic wave.

Takada, Noriharu; Fujikawa, Akinori; Sasaki, Koichi

2011-12-01

411

Dependence of ablation depth on angle of incidence for hard tissue ablation using pulsed CO2 laser  

NASA Astrophysics Data System (ADS)

While using a laser to process hard tissue, it is difficult to guarantee, that the laser beam is always perpendicular to the tissue surface. Therefore, it is necessary to know the dependence of ablation depth on angle of incidence for preoperative planning. Considering the propagation of the ablation front, an Addition Model is developed in this work. It indicates that the shape of a crater ablated by a single pulse with non-zero angle of incidence can be regarded as the sum of the original tissue surface and a symmetric profile, which is corresponding to the shape of a crater ablated by perpendicularly incident beam. Meanwhile, the ablation depth at a point P is defined as the distance from P to the original tissue surface along the optical axis of the incident beam. In the context of this definition, the dependence is experimentally studied. The results of the experiments were unexpected: the ablation depth is independent of angle of incidence up to ca. 55°. Possible reasons for these results are discussed.

Zhang, Yaokun; Burgner, Jessica; Raczkowsky, Jörg; Wörn, Heinz

2011-06-01

412

Fabrication of SiC:Ge: waveguide wavelength selector using ion implantation and laser deposition techniques  

Microsoft Academic Search

A waveguid-wavelength selector was fabricated using ion implanted SiC substrate and Ga\\/Ge thin film using laser ablation techniques. The device was used as a CO2 laser lines selector. The theory of the operation is based on visibility of the CO2 laser to produce a thermal grating which drives the optical selector with maximum efficiency of 46 MHz of laser offset

Abdalla M. Darwish; Brent D. Koplitz; Nadia Majeed; Trivia Frazier; Robert Combs; Daryush Ila; Nikolai V. Kukhtarev

2004-01-01

413

Laser ablation of graphite in different buffer gases  

SciTech Connect

The KrF-laser ablation of graphite into 300 Torr of He, Ne, Ar, and Xe has been studied by fast imaging of the plasma emission and post-deposition analyses of collected film deposits. In each case, the soot which was redeposited on the irradiated rod following ablation was highly fullerene-deficient compared to the material collected on the sample disk 1.5 cm from the rod, as determined by laser desorption Fourier Transform Mass Spectrometry (FTMS) Investigation of the plasma plume propagation using fast ICCD photography reveals three main phases to the expansion: (1) forward motion, deceleration and stopping of the leading edge of the plume, (2) an apparent reflected shock within the plume which propagates backward and reflects from the rod surface, (3) coalescence of these two components, resulting in continued expansion and dissipation of the plasma and the appearance of glowing ultrafine particles. For the laser plume propagating in 300 Torr of Xe the characteristic time intervals for these three phases are 0-300 ns, 300-1000 ns, and 1-1000 {mu}s for phases (1), (2), and (3) respectively. The possible explanation of the observed difference in fullerene content is discussed on the basis of different plasma phases resulting in soot deposition on the rod and sample disk. The measurement of ro-vibrational spectra of electronically excited C{sub 2} has been performed. Rotational and vibrational temperatures, T{sub R} = 3000 {+-} 300K and T{sub V} = 6000 {+-} 500K have been obtained from the comparison of measured and calculated C{sub 2} -Swan band emission.

Puretzky, A.A. [Institute of Spectroscopy, Moscow (Russian Federation); Geohegan, D.B.; Haufler, R.E. [Oak Ridge National Lab., TN (United States)] [and others

1996-04-01

414

Glass particles produced by laser ablation for ICP-MS measurements  

Microsoft Academic Search

Pulsed laser ablation (266nm) was used to generate glass particles from two sets of standard reference materials using femtosecond (150fs) and nanosecond (4ns) laser pulses with identical fluences of 50Jcm?2. Scanning electron microscopy (SEM) images of the collected particles revealed that there are more and larger agglomerations of particles produced by nanosecond laser ablation.In contrast to the earlier findings for

Jhanis J. Gonzalez; Chunyi Liu; Sy-Bor Wen; Xianglei Mao; Richard E. Russo

2007-01-01

415

Metal particles produced by laser ablation for ICP–MS measurements  

Microsoft Academic Search

Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150fs) and nanosecond (4ns) laser pulses with identical fluences of 50Jcm?2. Characterization of particles and correlation with inductively coupled plasma mass spectrometer (ICP–MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without

Jhanis J. Gonzalez; Chunyi Liu; Sy-Bor Wen; Xianglei Mao; Richard E. Russo

2007-01-01

416

Hg(II) sensing based on functionalized carbon dots obtained by direct laser ablation  

Microsoft Academic Search

The synthesis of carbon nanoparticles obtained by direct laser ablation [UV pulsed laser irradiation (248nm, KrF)] of carbon targets immersed in water is described. Laser ablation features were optimized to produce carbon nanoparticles with dimensions up to about 100nm. After functionalization with NH2–polyethylene-glycol (PEG200) and N-acetyl-l-cysteine (NAC) the carbon nanoparticles become fluorescent with excitation and emission wavelengths at 340 and

Helena Gonçalves; Pedro A. S. Jorge; J. R. A. Fernandes

2010-01-01

417

Dynamics of excimer laser-ablated aluminum neutral atom plume measured by dye laser resonance absorption photography  

Microsoft Academic Search

We report the first dye laser resonance absorption photographs of a single species of aluminum ground-state neutral atoms in the plume ablated from solid aluminum by KrF excimer laser radiation. Aluminum ground-state neutral atoms were diagnosed by illuminating the ablated plume with a dye laser tuned to the 3²{ital P}ââ--4²{ital S}ââ transition at 394.4 nm. Measurements have been performed in

Ronald M. Gilgenbach; Peter L. G. Ventzek

1991-01-01

418

Dynamics of excimer laser-ablated aluminum neutral atom plume measured by dye laser resonance absorption photography  

Microsoft Academic Search

We report the first dye laser resonance absorption photographs of a single species of aluminum ground-state neutral atoms in the plume ablated from solid aluminum by KrF excimer laser radiation. Aluminum ground-state neutral atoms were diagnosed by illuminating the ablated plume with a dye laser tuned to the 32P1\\/2–42S1\\/2 transition at 394.4 nm. Measurements have been performed in vacuum as

Ronald M. Gilgenbach; Peter L. G. Ventzek

1991-01-01

419

Modification of polyimide wetting properties by laser ablated conical microstructures  

NASA Astrophysics Data System (ADS)

Laser texturing of Kapton® HN polyimide was performed by low-fluence ablation using a pulsed, frequency tripled (349 nm) Nd:YLF laser. The laser was scanned in two dimensions in order to generate texture over a large area. The laser overlap percentage and fluence were varied and the resulting texture was studied. The texture features were inspected by electron microscopy and energy dispersive X-Ray spectroscopy (EDS), while the static contact angle of de-ionized water was measured by a contact angle goniometer. Rounded bump features were formed at all fluences, which decreased in areal density with fluence and number of laser pulses. Conical microstructures or "cones" were also formed at most fluences. Cones were larger than the bumps and thus had lower areal density, which increased as a function of the number of laser pulses. The polyimide was hydrophilic before texturing, with a contact angle of approximately 76°. For most of the experimental conditions the contact angle increased as a result of texturing, with the contact angle exceeding 90° for some textured surfaces, and reaching values as high as 118°. In general, the surfaces with significant increases in contact angle had high density of texture features, either bumps or cones. The surfaces that experienced a decrease in contact angle generally had low density of texture features. The increase in contact angle from a wetting (? < 90°) to a nonwetting surface (? > 90°) cannot be explained by texturing alone. EDS measurements indicate that textured regions had higher carbon content than the untextured regions due to depletion of oxygen species. The increase in carbon content relative to the oxygen content increased the native contact angle of the surface, causing the transition from hydrophilic to hydrophobic behavior. The contact angle of a textured surface increased as the relative spacing of features (diameter to spacing) decreased.

Least, Brandon T.; Willis, David A.

2013-05-01

420

Optical Emission Analysis of Triple-Fold Plume Formed at Pulsed IR Laser Ablation of Graphite  

NASA Astrophysics Data System (ADS)

A sheet of sintered graphite was ablated by a pulsed Nd:YAG laser in He gas and air at 1 atm. Triple-fold plumes were produced in both gases. The time-resolved emission spectrograms of the plume were measured and the plume was analyzed as follows. The plume is generated near the target surface and expands while separating into three because of different expansion speeds of its components. The fastest component is gas plasma mainly composed of carbon ions in the He atmosphere, and nitrogen and oxygen ions in air. The second fastest component is very hot and compressed neutral molecules of the gas, that is, the shock wave. The slowest component is radical vapor of the graphite target.

Tasaka, Yoshiharu; Tanaka, Masatoshi; Usami, Seiji

1995-03-01

421

Measurements of erbium laser-ablation efficiency in hard dental tissues under different water cooling conditions.  

PubMed

ABSTRACT. Laser triangulation measurements of Er:YAG and Er,Cr:YSGG laser-ablated volumes in hard dental tissues are made, in order to verify the possible existence of a "hydrokinetic" effect that has been proposed as an alternative to the "subsurface water expansion" mechanism for hard-tissue laser ablation. No evidence of the hydrokinetic effect could be observed under a broad range of tested laser parameters and water cooling conditions. On the contrary, the application of water spray during laser exposure of hard dental material is observed to diminish the laser-ablation efficiency (AE) in comparison with laser exposure under the absence of water spray. Our findings are in agreement with the generally accepted principle of action for erbium laser ablation, which is based on fast subsurface expansion of laser-heated water trapped within the interstitial structure of hard dental tissues. Our measurements also show that the well-known phenomenon of ablation stalling, during a series of consecutive laser pulses, can primarily be attributed to the blocking of laser light by the loosely bound and recondensed desiccated minerals that collect on the tooth surface during and following laser ablation. In addition to the prevention of tooth bulk temperature buildup, a positive function of the water spray that is typically used with erbium dental lasers is to rehydrate these minerals, and thus sustaining the subsurface expansion ablation process. A negative side effect of using a continuous water spray is that the AE gets reduced due to the laser light being partially absorbed in the water-spray particles above the tooth and in the collected water pool on the tooth surface. Finally, no evidence of the influence of the water absorption shift on the hypothesized increase in the AE of the Er,Cr:YSGG wavelength is observed. PMID:24105399

Kuš?er, Lovro; Diaci, Janez

2013-10-01

422

Excimer laser ablation of thin gold films on a quartz crystal microbalance at various argon background pressures  

Microsoft Academic Search

Excimer laser ablation of gold films deposited on a quartz crystal microbalance is investigated. The ablation rate is directly obtained from the frequency shift of the microbalance. The measured single-shot ablation rate is found to be at least two orders of magnitude higher than the numerical predictions based on a surface vaporization model. Surface morphology studies indicate that hydrodynamic ablation

X. Zhang; S. S. Chu; J. R. Ho; C. P. Grigoropoulos

1997-01-01

423

Co:MgF2 laser ablation of tissue: effect of wavelength on ablation threshold and thermal damage.  

PubMed

The wavelength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical absorption length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 microns, a wavelength region in which the absorption length varies by a decade. For soft tissues the ablation threshold tracks the optical absorption length; for bone there is little wavelength dependence, consistent with the low water content of bone. Thermal damage vs. wavelength was also studied for cornea and bone. Thermal damage to cornea has a weak wavelength dependence, while that to bone shows little wavelength dependence. Framing-camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion. PMID:2034011

Schomacker, K T; Domankevitz, Y; Flotte, T J; Deutsch, T F

1991-01-01

424

Femtosecond laser ablation characteristics of nickel-based superalloy C263  

NASA Astrophysics Data System (ADS)

Femtosecond laser (180 fs, 775 nm, 1 kHz) ablation characteristics of the nickel-based superalloy C263 are investigated. The single pulse ablation threshold is measured to be 0.26±0.03 J/cm2 and the incubation parameter ?=0.72±0.03 by also measuring the dependence of ablation threshold on the number of laser pulses. The ablation rate exhibits two logarithmic dependencies on fluence corresponding to ablation determined by the optical penetration depth at fluences below ˜5 J/cm2 (for single pulse) and by the electron thermal diffusion length above that fluence. The central surface morphology of ablated craters (dimples) with laser fluence and number of laser pulses shows the development of several kinds of periodic structures (ripples) with different periodicities as well as the formation of resolidified material and holes at the centre of the ablated crater at high fluences. The debris produced during ablation consists of crystalline C263 oxidized nanoparticles with diameters of ˜2-20 nm (for F=9.6 J/cm2). The mechanisms involved in femtosecond laser microprocessing of the superalloy C263 as well as in the synthesis of C263 nanoparticles are elucidated and discussed in terms of the properties of the material.

Semaltianos, N. G.; Perrie, W.; French, P.; Sharp, M.; Dearden, G.; Logothetidis, S.; Watkins, K. G.

2009-03-01

425

Surface Engineering of Silicon and Carbon by Pulsed-Laser Ablation  

SciTech Connect

Experiments are described in which a focused pulsed-excimer laser beam is used either to ablate a graphite target and deposit hydrogen-free amorphous carbon films, or to directly texture a silicon surface and produce arrays of high-aspect-ratio silicon microcolumns. In the first case, diamond-like carbon (or tetrahedral amorphous carbon, ta-C) films were deposited with the experimental conditions selected so that the masses and kinetic energies of incident carbon species were reasonably well controlled. Striking systematic changes in ta-C film properties were found. The sp{sup 3}-bonded carbon fraction, the valence electron density, and the optical (Tauc) energy gap ail reach their maximum values in films deposited at a carbon ion kinetic energy of {approximately}90 eV. Tapping-mode atomic force microscope measurements also reveal that films deposited at 90 eV are extremely smooth (rms roughness {approximately}1 {angstrom} over several hundred nm) and relatively free of particulate, while the surface roughness increases in films deposited at significantly lower energies. In the second set of experiments, dense arrays of high-aspect-ratio silicon microcolumns {approximately}20-40 {micro}m tall and {approximately}2 {micro}m in diameter were formed by cumulative nanosecond pulsed excimer laser irradiation of silicon wafers in air and other oxygen-containing atmospheres. It is proposed that microcolumn growth occurs through a combination of pulsed-laser melting of the tips of the columns and preferential redeposition of silicon on the molten tips from the ablated flux of silicon-rich vapor. The common theme in this research is that a focused pulsed-laser beam can be used quite generally to create an energetic flux, either the energetic carbon ions needed to form sp{sup 3} (diamond-like) bonds or the overpressure of silicon-rich species needed for microcolumn growth. Thus, new materials synthesis opportunities result from the access to nonequilibrium growth conditions provided by pulsed-laser ablation.

Fowlkes, J.D.; Geohegan, D.B.; Jellison, G.E., Jr.; Lowndes, D.H.; Merkulov, V.I.; Pedraza, A.J.; Puretzky, A.A.

1999-02-28

426

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Laser ablation plume dynamics in nanoparticle synthesis  

NASA Astrophysics Data System (ADS)

The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO2 laser pulse with a duration of ~500 ?s (at the 0.03 level), energy of 1.0-1.3 J and peak power of 6-7 kW have been studied using high-speed photography of the plume luminescence and shadow. The targets were used to produce nanopowders by laser evaporation. About 200 ?s after termination of the pulse, shadowgraph images of the plumes above the YSZ and Nd:YAG targets showed dark straight tracks produced by large particles. The formation of large (~10 ?m) particles is tentatively attributed to cracking of the solidified melt at the bottom of the ablation crater. This is supported by the fact that no large particles are ejected from graphite, which sublimes without melting. Further support to this hypothesis is provided by numerical 3D modelling of melt cooling in craters produced by laser pulses of different shapes.

Osipov, V. V.; Platonov, V. V.; Lisenkov, V. V.

2009-06-01

427

Characterization of Laser-Ablated, Magnetized Carbon Plasmas Relevant to Magnetized Collisionless Shocks  

NASA Astrophysics Data System (ADS)

We present experiments on laser-ablated, magnetized carbon plasmas performed at the University of California, Los Angeles (UCLA). A graphite target placed inside a static magnetic field (1 kG) created by a 50 cm-diameter Helmholtz coil was ablated by laser pulses at 1053 nm with energies between 10-100 J. Magnetic flux probes measured the magnetic field compression and expulsion of the resulting blow-off plasma and diamagnetic bubble. A separate laser at 527 nm was used for Thomson scattering to characterize the electron temperature and density up to several cm from the target and several microseconds after the initial laser ablation. The carbon ionization states and blow-off velocities were further measured with emission spectroscopy. The data was used to inform 2D hybrid simulations of a laser-ablated plasma expanding into an ambient plasma, relevant to upcoming magnetized collisionless shock experiments on the Large Plasma Device at UCLA.

Schaeffer, D. B.; Bondarenko, A. S.; Everson, E. T.; Clark, E. S.; Constantin, C. G.; Niemann, C.; Winske, D.

2012-10-01

428

Survey Of CO{sub 2} Laser Ablation Propulsion With Polyoxymethylene Propellant  

SciTech Connect

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 ablation that takes into account the ambient pressure, spot area, fluence, and effects from confinement and combustion. This paper reviews and synthesizes CO{sub 2} laser ablation propulsion research using POM targets. Necessary directions for future study are indicated to address incomplete regions of the various parameter spaces. Literature data is compared in terms of propulsion parameters such as momentum coupling coefficient and specific impulse, within a range of fluences from about 1-500 J/cm{sup 2}, ambient pressures from about 10{sup -2}-10{sup 5} Pa, and laser spot areas from about 0.01-10 cm{sup 2}.

Sinko