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1

Laser ablation loading of a surface-electrode ion trap  

E-print Network

We demonstrate loading by laser ablation of $^{88}$Sr$^+$ ions into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful ($\\gtrsim$ 500 meV).

David R. Leibrandt; Robert J. Clark; Jaroslaw Labaziewicz; Paul Antohi; Waseem Bakr; Kenneth R. Brown; Isaac L. Chuang

2007-06-22

2

Ion implantation induced by Cu ablation at high laser fluence  

NASA Astrophysics Data System (ADS)

High energy laser plasma-produced Cu ions have been implanted in silicon substrates placed at different distances and angles with respect to the normal to the surface of the ablated target. The implanted samples have been produced using the iodine high power Prague Asterix Laser System (PALS) using 438 nm wavelength irradiating in vacuum a Cu target. The high laser pulse energy (up to 230 J) and the short pulse duration (400 ps) produced a non-equilibrium plasma expanding mainly along the normal to the Cu target surface. Time-of-flight (TOF) technique was employed, through an electrostatic ion energy analyzer (IEA) placed along the target normal, in order to measure the ion energy, the ion charge state, the energy distribution and the charge state distribution. Ions had a Boltzmann energy distributions with an energy increasing with the charge state. At a laser fluence of the order of 6 × 10 6 J/cm 2, the maximum ion energy was about 600 keV and the maximum charge state was about 27+. In order to investigate the implantation processes, Cu depth profiles have been performed with Rutherford backscattering spectrometry (RBS) of 1.5 MeV helium ions, Auger electron spectroscopy (AES) with 3 keV electron beam and 1 keV Ar sputtering ions in combination with scanning electron microscopy (SEM). Surface analysis results indicate that Cu ions are implanted within the first surface layers and that the ion penetration ranges are in agreement with the ion energy measured with IEA analysis.

Torrisi, L.; Mezzasalma, A. M.; Gammino, S.; Badziak, J.; Parys, P.; Wolowski, J.; Laska, L.; Franco, G.

2006-10-01

3

Laser ablation-molecular beam (LAMB) method: coordination (solvation) chemistry of monopositive metal ions in the gas phase  

Microsoft Academic Search

The coordination (solvation) chemistry of monopositive metal ions in the gas phase was studied using the laser ablation-molecular beam (LAMB) method. In this method, monopositive metal ions are prepared in the gas phase by laser ablation of metal substrate in vacuum, and allowed to react with molecules or clusters in a molecular beam injected nearby. From the distribution of complex

Hiroyasu Sato; Yasuhiro Horiki; Osamu Ito

1995-01-01

4

Time-of-flight spectroscopy of the energy distribution of laser-ablated atoms and ions  

SciTech Connect

The growth of ultrathin films, deposited by laser ablation, crucially depends on the energy of the ablated species. Therefore, a time-of-flight (TOF) spectrometer has been constructed and measurements have been carried out in order to determine the energy distribution of laser-ablated Fe and Pt atoms and ions in the plasma created by nanosecond pulses of a frequency-doubled neodymium doped yttrium aluminum garnet laser. The experiments have been performed in ultrahigh vacuum at relatively low laser power. For measuring the spectra of the neutrals, a cross-beam electron source for postionization and electric as well as magnetic fields for repelling the ions are employed. Nevertheless, measurements of neutral particles are restricted to low plasma densities due to electrostatic shielding within the plasma, leading to an inefficient deflection of charged particles by electrostatic and magnetic fields. Test measurements have been performed by utilizing the TOF spectrometer as a pressure gauge and also by chopping the electron beam, running the TOF spectrometer as a residual gas mass spectrometer. The spectra of the laser-ablated plasmas have shown plasma conditions with a Debye length of approximately 10{sup -4} m, densities of 10{sup 15}-10{sup 16} m{sup -3} and ion energies up to 150 eV. Neutral spectra have shown an unexpectedly low fraction of neutrals (10{sup -3}-10{sup -4}) and hyperthermal energies up to several 10 eV, possibly contributed by recombination of ions and electrons in the plasma. Even though gas spectra had demonstrated the expected sensitivity of the TOF spectrometer for low-energy neutrals, no thermally evaporated neutral atoms could be found.

Buchsbaum, A.; Rauchbauer, G.; Varga, P.; Schmid, M. [Institut fuer Allgemeine Physik, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien (Austria)

2008-04-15

5

Ion mobility spectrometry of gas-phase ions from laser ablation of solids in air at ambient pressure.  

PubMed

A mobility spectrometer was used to characterize gas-phase ions produced from laser ablation of solids in air at 100 degrees C and at ambient pressure with a beam focused to a diameter of Ion intensities increased initially and then decreased with repeated laser shots through drilling of the solid, and persistence of signal was proportional to hardness. A single comparatively narrow peak for negative ions was observed in mobility spectra for all materials and this was mass-identified as O(2)(-). These ions were formed in air from reactions of oxygen with electrons emitted from the ablation step. Positive ions ablated directly from the solid were masked in ion mobility spectrometry/mass spectrometry (IMS/MS) studies by ionization of moisture and impurities. Positive ions from solids were seen only in the IMS analyzer at elevated temperature and low moisture. Under such conditions, materials were classified from mobility spectra alone with principal component analysis. PMID:17958958

Eiceman, G A; Young, D; Schmidt, H; Rodriguez, J E; Baumbach, J I; Vautz, W; Lake, D A; Johnston, M V

2007-10-01

6

Effect of citrate ions on laser ablation of Ag foil in aqueous medium  

NASA Astrophysics Data System (ADS)

Promoting effect of citrate in 1 × 10-5-1×10-2 M concentrations on laser ablation (LA) of a Ag foil in aqueous solution performed by ns laser pulses at 1064 nm is reported. Furthermore, adsorption of citrate ions was found to increase markedly the stability of the resulting LA-Ag hydrosol. The results are discussed on the basis of comparison of surface plasmon extinction spectral characteristics, transmission electron microscopy images, nanoparticle size distributions and surface-enhanced Raman scattering (SERS) spectral tests of hydrosols resulting from LA in neutral and acidic aqueous citrate solutions and in pure water.

Sisková, K.; Vlcková, B.; Turpin, P.-Y.; Fayet, C.; Hromádková, J.; Slouf, M.

2007-04-01

7

Laser ablation-molecular beam method: a simple and versatile diagnosis to study chemistry of monopositive metal ions in the gas phase  

Microsoft Academic Search

Chemistry of monopositive metal ions in the gas phase has been studied with the laser ablation-molecular beam (LAMB) method developed by the authors' group. In this method, monopositive metal ions (M+'s) are prepared in the gas phase by laser ablation of metal substrates in vacuum and they are allowed to react with molecules or clusters in a molecular beam injected

Osamu Ito; Koji Furukuwa; Yasuhiro Horiki; Satoru Nishio; Akiyoshi Matsuzaki; Hiroyasu Sato

1996-01-01

8

The Laser Ablation Ion Funnel: Sampling for in situ Mass Spectrometry on Mars  

NASA Technical Reports Server (NTRS)

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.

2011-01-01

9

Inductively coupled plasma mass spectrometer with laser ablation metal ions release detection in the human mouth  

NASA Astrophysics Data System (ADS)

Presence of more dental alloys in oral cavity often causes pathological symptoms. Due to various and multi-faced symptomatology, they tend to be a source of significant problems not only for the patient but also for the dentist. Metal ions released from alloys can cause subjective and objective symptoms in mouth. The aim of this study was detection of metal elements presence in saliva. There were 4 groups of examined persons: with intact teeth (15 individuals) with metallic restorations, pathological currents 5-30 (mu) A, multi-faced subjective symptomatology and uncharacteristic objective diagnosis (32 patients), with metallic restorations and no subjective symptoms (14 persons) and with metallic restorations, without pathological currents and with problems related to galvanism (13 patients). Presence of 14 metal elements was checked by inductively coupled plasma mass spectrometer with laser ablation. Nd:YAG laser detector was used. There were significant differences in content of silver, gold and mercury between persons with intact teeth and other three groups. There were no differences found between subjects with and without galvanic currents, and presence of subjective and objective symptoms.

Kueerova, Hana; Dostalova, Tatjana; Prochazkova, J.

2002-06-01

10

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

E-print Network

??Ongoing issues that affect the continued maturation of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are studied. Spectral interferences in the form of polyatomic ions can… (more)

Witte, Travis

2011-01-01

11

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

12

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

13

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

14

Femtosecond laser ablation of solid materials  

NASA Astrophysics Data System (ADS)

In this dissertation, femtosecond laser materials processing is studied. A time-of-flight mass spectrometer has been designed, constructed and utilized to measure the time-of-flight spectra of the ions ablated by femtosecond laser pulses. The velocities and kinetic energies of the ions are determined. Emission spectroscopy and imaging have been carried out to analyze the laser-induced plume. Craters ablated in vacuum and under ambient pressure are measured by a scanning electron microscope (SEM) and a light interferometric microscope. Numerical methods in microscale energy transfer are first reviewed. Subsequently, a numerical model based on the two-temperature concept is utilized to account for the non-equilibrium energy transfer processes dominating the ultrashort laser pulse excitation of materials. Time-of-flight measurements reveal the presence of extremely energetic ions in femtosecond laser-induced plumes, with kinetic energies more than one order of magnitude higher than those of nanosecond laser-induced ions. Two different ablation regimes, exhibiting different laser fluence dependence of the total ion yields, and the corresponding percentage of energetic ions and the crater depths, are discovered for femtosecond laser ablation of titanium. Numerical modeling shows that the laser fluences associated with the second ablation regime can raise the lattice system to the range of the thermodynamic critical point and hence may cause explosive evaporation leading to the observed higher ablation rates. The first regime, however, occurs at lower laser fluences, when the laser energy is mainly deposited in the shallow region defined by the optical penetration depth. The more localized energy deposition is believed to lead to higher percentage of energetic ions, albeit to less total ablation volume. Femtosecond laser-induced plumes have been found to be much smaller in spatial dimensions and weaker in intensity than those induced by nanosecond laser pulses. The ambient pressure is found to restrain the expansion of the plumes. The non-equilibrium microscopic energy transfer between the electron and lattice subsystems needs to be considered to model femtosecond laser materials processing. The two-temperature approach is capable of at least semi-quantitatively modeling real engineering problems. Due to the large temperature range encountered in typical laser ablation applications, the temperature dependence of the materials thermal properties is found to be very important for accurate modeling. (Abstract shortened by UMI.)

Ye, Mengqi

15

Improved laser ablation model for asteroid deflection  

NASA Astrophysics Data System (ADS)

This paper presents an improved laser ablation model and compares the performance - momentum coupling and deflection system mass - of laser ablation against contactless deflection methods based on ion-propulsion. The deflection of an asteroid through laser ablation is achieved by illuminating the surface of the asteroid with high intensity laser light. The absorbed energy induces the sublimation of the surface material and the generation of a plume of gas and ejecta. Similar to a rocket engine, the flow of expelled material produces a continuous and controllable thrust that could be used to modify the trajectory and tumbling motion of the asteroid. Recent results gained from a series of laser ablation experiments were used to improve the sublimation and deflection models. In each experiment a terrestrial olivine sample was ablated, under vacuum, with a 90 W continuous wave laser. The paper presents a model that better fits the outcomes of the experimental campaign, in particular in terms of mass flow rate and spot temperature.

Vasile, Massimiliano; Gibbings, Alison; Watson, Ian; Hopkins, John-Mark

2014-10-01

16

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

2013-01-01

17

Laser Ablation for Medical Applications  

NASA Astrophysics Data System (ADS)

Medical applications of laser are measurement, laser surgery, in-situ monitoring, and processing of medical devices. In this paper, author briefly reviews the trends of medical applications, describes some new applications, and then discuss about the future trends and problems of medical applications. At present, the domestic market of laser equipment for medical applications is nearly 1/10 of that for industrial applications, which has registered significant growth continuously. Laser surgery as a minimum invasive surgery under arthroscope is expected to decrease the pain of patients. Precise processing such as cutting and welding is suitable for manufacturing medical devices. Pulsed laser deposition has been successfully applied to the thin film coating. The corneal refractive surgery by ArF excimer laser has been widely accepted for its highly safe operation. Laser ablation for retinal implant in the visual prosthesis is one of the promising applications of laser ablation in medicine. New applications with femtosecond laser are expected in the near future.

Hayashi, Ken-Ichi

18

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

19

Laser Ablation of Biological Tissue Using Pulsed CO2 Laser  

Microsoft Academic Search

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

Yuichi Hashishin; Shu Sano; Takeyoshi Nakayama

2010-01-01

20

The Structure of Gas Phase Tin Oxide Ions Generated by Laser Ablation: A Combined Fourier Transform Mass Spectrometry and Density Functional Theory Study  

Microsoft Academic Search

The radical ion series (SnO)+2-6, (SnO)-2-6, (SnO)0-5Sn+ and (SnO)1-6O- have been generated by the high power laser ablation of SnO and SnO2 targets positioned inside an ICR cell. In all ablation spectra obtained, and for any particular size Snx core, the tin-rich clusters (SnO)xSn+ were more abundant than the corresponding oxygen-equivalent clusters (SnO)+x, while the oxygen-rich clusters (SnO)xO- were always

Phillip Jackson; Keith J. Fisher; Ian G. Dance; Gerard E. Gadd; Gary D. Willett

2002-01-01

21

Limited coordination number and competitive coordination in ammonia-water mixed-ligand complexes of monopositive metal ions as studied by the laser-ablation-molecular beam method: Experiment and simulation  

Microsoft Academic Search

Ammonia-water mixed-ligand complexes of monopositive metal ions M+ (M=Mg, Al, Mn, and Co) were prepared in the gas phase by reactions of metal ions laser-ablated from a metal substrate in vacuum with ammonia-water binary clusters in a molecular beam injected nearby [the laser-ablation-molecular beam (LAMB) method]. Relative abundances of M+(NH3)m(H2O)n are characterized by intensity gaps which indicate limited (typically 2

Hiroyasu Sato; Akiyoshi Matsuzaki; Satoru Nishio; Osamu Ito; Koji Furukawa; Takashi Kawasaki

1998-01-01

22

Quadrupole mass spectrometry and time-of-flight analysis of ions resulting from 532 nm pulsed laser ablation of Ni, Al, and ZnO targets  

SciTech Connect

This work describes the design and validation of an instrument to measure the kinetic energies of ions ejected by the pulsed laser ablation (PLA) of a solid target. Mass spectra show that the PLA of Ni, Al, and ZnO targets, in vacuum, using the second harmonic of a Nd:YAG laser (532 nm, pulse duration {approx}10 ns) generates abundant X{sup n+} ions (n{<=}3 for Ni, {<=}2 for Al, {<=}3 and {<=}2 for Zn and O respectively from ZnO). Ions are selected by their mass/charge (m/z) ratio prior to the determination of their times of flight. PLA of Ni has been studied in most detail. The mean velocities of ablated Ni{sup n+} ions are shown to follow the trend v(Ni{sup 3+})>v(Ni{sup 2+})>v(Ni{sup +}). Data from Ni{sup 2+} and Ni{sup 3+} are fitted to shifted Maxwellian functions and agree well with a model which assumes both thermal and Coulombic contributions to ion velocities. The dependence of ion velocities on laser pulse energy (and fluence) is investigated, and the high energy data are shown to be consistent with an effective accelerating voltage of {approx}90 V within the plume. The distribution of velocities associated with Ni{sup 3+} indicates a population at cooler temperature than Ni{sup 2+}.

Sage, Rebecca S.; Cappel, Ute B.; Ashfold, Michael N. R.; Walker, Nicholas R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom)

2008-05-01

23

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

24

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

25

Laser ablation of silicone composites  

NASA Astrophysics Data System (ADS)

Silicone rubber based composites are widely used to produce outdoor insulators. In adverse weather conditions these can be damaged by surface discharge activity resulting in deterioration of their dielectric properties and an eventual need for replacement. Inclined plane tracking tests are frequently used to determine the relative performance of different material formulations used in their construction. An alternative approach to characterisation is to use an infra-red laser to deposit known amounts of energy at a known rate to the sample's surface allowing comparative ranking of different materials. In this paper several silicone based composites have been ranked using a laser ablation technique and the results were then compared to those obtained from tracking tests on the same materials. The comparison indicates that laser ablation ranks the materials in the same order as the tracking tests and may therefore constitute a quick and cost effective method for the routine characterisation of outdoor insulation components.

Hosier, I. L.; Abd Rahman, M. S.; Vaughan, A. S.; Krivda, A.; Kornmann, X.; Schmidt, L. E.

2011-08-01

26

Status of the Ablative Laser Propulsion Studies  

NASA Technical Reports Server (NTRS)

We present a short review of our laser-propulsion research as well as some of the current results of the Ablative Laser Propulsion (ALP) studies currently underway at the University of Alabama in Huntsville. It has been shown that direct surface ablation of a solid material produces high specific impulse (Isp) at relatively high energy conversion efficiency (20 - 40%). We detail measurements of specific impulse, thrust and coupling coefficients for elemental target materials both with single and with double pulse laser shots. We also present measurements taken using three independent methods for determination of Isp. The three methods produce consistent values from ion time-of-flight technique, impulse measurements and imaging of the expansion front of plasma plume. We present a demonstration of our ALP lightcraft, a small free-flying micro-vehicle that is propelled by ablation. For ALP lightcraft we use a subscale thin shell of nickel replicated over a diamond turned mandrel that produces a highly polished self-focusing, truncated at the focus parabolic mirror. The mass of the lightcraft is 54 mg and it is driven by 100-ps wide, 35-mJ laser pulses at 532 nm wavelength. This is an ongoing research. We also present the latest work on laserdriven micro-thrusters and detail some the near term goals of our program.

Herren, Kenneth A.; Lin, Jun; Cohen, Tinothy; Pakhomov, Andrew V.; Thompson, M. Shane

2004-01-01

27

Laser Ablation Propulsion A Study  

NASA Astrophysics Data System (ADS)

Laser Ablation Propulsion (LAP) will serve as an alternative propulsion system for development of microthrusters. The principle of LAP is that when a laser (pulsed or continuous wave) with sufficient energy (more than the vaporization threshold energy of material) is incident on material, ablation or vaporization takes place which leads to the generation of plasma. The generated plasma has the property to move away from the material hence pressure is generated which leads to the generation of thrust. Nowadays nano satellites are very common in different space and defence applications. It is important to build micro thruster which are useful for orienting and re-positioning small aircraft (like nano satellites) above the atmosphere. modelling of LAP using MATLAB and Mathematica. Schematic is made for the suitable optical configuration of LAP. Practical experiments with shadowgraphy and self emission techniques and the results obtained are analysed taking poly (vinyl-chloride) (PVC) as propellant to study the

Irfan, Sayed A.; Ugalatad, Akshata C.

28

ablation laser spectrometer  

E-print Network

to detect pyrolysis products from plant materi- als using poplar, a potentially high-impact bioenergy:YAG laser (355 nm). The resulting vapors are entrained in a free jet expansion of helium, then skimmed gasification. Potential Impact This combined platform used for the measurement and analysis of biomass cell

29

Laser-plasma interactions in 532 nm ablation of Si  

Microsoft Academic Search

Single-crystal Si was ablated by pulsed 532 nm laser radiation, and the volume of removed material and the time-resolved current of ejected ions were measured. These data were used to determine the ion fraction of ejected material. The ion fractions provide direct evidence that the break point is due to the laser-plasma interaction. This is confirmed by the speed distributions

Gyoowan Han; P. Terrence Murray

2000-01-01

30

From fundamental fullerenes to the cardinal calcium candidate: The development of a Laser Ablation ion source and its diverse application at the LEBIT facility  

NASA Astrophysics Data System (ADS)

A Laser Ablation Source (LAS) has been developed at the Low Energy Beam and Ion Trap (LEBIT) mass spectrometry facility at the National Superconducting Cyclotron Laboratory. LAS enhances the offline capability of LEBIT providing increased access to ions for measurements of scientific interest as well as for calibration measurements and checks of systematic effects. The design and implementation of LAS are described in this work. Carbon cluster ions produced via laser ablation were used to probe LEBIT mass-dependent systematic effects. Since carbon cluster ions span the entire nuclear chart and have essentially no mass uncertainty, they are the ideal tool for these studies. As part of this thesis work, frequency shifts across a 108 u mass range were quantified and found to lead to a relative error in mass determination less than 10-9/u. LAS was operated in tandem with the surface ion source to produce ions of 48Ca+ and 48Ti + for the first direct measurement of the 48Ca double beta decay Q value. Accurate knowledge of this Q value is important for experiments that employ 48Ca for neutrinoless double beta decay searches. The LEBIT high precision Penning trap Q value measurement revealed a 3 sigma shift from the previously accepted value and reduced the uncertainty by a factor of five. The measurement procedure and results are discussed in this thesis. The first direct determination of the 78Kr double electron Q value was accomplished at the LEBIT facility. This determination indicates a 2 sigma shift from the previously accepted value and reduces the uncertainty by a factor of three. With the improved Q value determination, the resonance condition was explored for various double electron captures. The potential for resonance enhancement is evaluated, and the viability of 78Kr as a candidate for neutrinoless double electron capture experiments is discussed.

Bustabad, Scott Edward

31

Characterization of the laser ablation plasma used for the deposition of amorphous carbon  

Microsoft Academic Search

The plasma produced by laser ablation of a graphite target was studied by means of optical emission spectroscopy and a Langmuir planar probe. Laser ablation was performed using a Nd:YAG laser with emission at the fundamental line with pulse length of 28ns. In this work, we report the behavior of the mean kinetic energy of plasma ions and the plasma

Enrique Camps; L. Escobar-Alarcón; V. H. Castrejón-Sánchez; M. A. Camacho-López; Stephen Muhl

2007-01-01

32

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

33

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

34

Fundamental Characteristics of a Laser Ablation Microthruster  

Microsoft Academic Search

The fundamental characteristics of a laser ablation microthruster were investigated for a 10 kg-class microspacecraft. A single-shot impulse measurement was performed using a thrust stand on which a prototype thruster was installed and the associate ablated mass was estimated from the pressure increase in the space chamber. The best performance of several polymer materials was obtained using polyvinylchloride as the

Hiroyuki Koizumi; Takayoshi Inoue; Kimiya Komurasaki; Yoshihiro Arakawa

2007-01-01

35

Imaging and spatial distribution of ?-amyloid peptide and metal ions in Alzheimer’s plaques by laser ablation–inductively coupled plasma–mass spectrometry  

Microsoft Academic Search

Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) has been developed as a new strategy for detection and imaging of ?-amyloid protein in immunohistochemical sections from the brains of a transgenic mouse model of Alzheimer’s disease. The distribution of ?-amyloid deposits in tissue was based on measurement of Eu- and Ni-coupled antibodies. The laser-based methodologies (spot ablation, single line raster, and two-dimensional

Robert W. Hutchinson; Alan G. Cox; Cameron W. McLeod; Peter S. Marshall; Alex Harper; Emma L. Dawson; David R. Howlett

2005-01-01

36

Femtosecond laser ablation of the stapes  

NASA Astrophysics Data System (ADS)

A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations.

McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

2009-03-01

37

Femtosecond Laser Ablation: Fundamentals and Applications  

E-print Network

, laser plasma interactions, and plume hydrodynam- ics. Analytical figures of merit will be discussed. The physics involved in laser-plasma generation and subsequent evolution is very complex and contains manyChapter 6 Femtosecond Laser Ablation: Fundamentals and Applications Sivanandan S. Harilal, Justin R

Harilal, S. S.

38

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

39

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

40

Dynamics of mid-infrared femtosecond laser resonant ablation  

NASA Astrophysics Data System (ADS)

Resonant ablation is beneficial to avoiding uncontrollable subsurface damages in the laser ablation of polymers. In this paper the dynamics of mid-infrared laser resonant ablation of polylactic acid and toluene was calculated by using fluid dynamic equations. The merits and drawbacks of mid-infrared femtosecond laser resonant ablation of high molecular weight polymers have been discussed.

Pang, Dongqing; Li, Yunxuan; Wang, Qingyue

2014-06-01

41

Novel Laser Ablation Technology for Surface Decontamination  

SciTech Connect

Laser ablation for surface cleaning has been pursued for the removal of paint on airplanes. It has also been pursued for the cleaning of semiconductor surfaces. However, all these approaches have been pursued by laser ablation in air. For highly contaminated surface, laser ablation in air can easily cause secondary contamination. Thus it is not suitable to apply to achieve surface decontamination for DOE facilities since many of these facilities have radioactive contaminants on the surface. Any secondary contamination will be a grave concern. The objective of this project is to develop a novel technology for laser ablation in liquid for surface decontamination. It aims to achieve more efficient surface decontamination without secondary contamination and to evaluate the economic feasibility for large scale surface decontamination with laser ablation in liquid. When laser ablation is pursued in the solution, all the desorbed contaminants will be confined in liquid. The contaminants can be precipitated and subsequently contained in a small volume for disposal. It can reduce the risk of the decontamination workers. It can also reduce the volume of contaminants dramatically.

Cheng, Chung H.

2004-06-01

42

Laser Ablation of Biological Tissue Using Pulsed CO2 Laser  

NASA Astrophysics Data System (ADS)

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 CO2 laser (wavelength: 10.6 ?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

2010-10-01

43

Fundamental Characteristics of a Laser Ablation Microthruster  

NASA Astrophysics Data System (ADS)

The fundamental characteristics of a laser ablation microthruster were investigated for a 10 kg-class microspacecraft. A single-shot impulse measurement was performed using a thrust stand on which a prototype thruster was installed and the associate ablated mass was estimated from the pressure increase in the space chamber. The best performance of several polymer materials was obtained using polyvinylchloride as the propellant. More heavily carbon doped polyvinylchloride showed higher performance, which means absorption length has a large effect on performance. The intensity of the laser beam on the ablation material was changed using constant laser power, and it was shown that intensity had little effect on the performance. This qualitative behavior agreed with the results of a simple thermal analysis. Mass spectroscopy of the ablation plume showed that the dominant reaction was dehydrochlorination in the range of 470 to 640 K, and the low-temperature reaction resulted in the best performance for polyvinylchloride.

Koizumi, Hiroyuki; Inoue, Takayoshi; Komurasaki, Kimiya; Arakawa, Yoshihiro

44

Basic ablation phenomena during laser thrombolysis  

NASA Astrophysics Data System (ADS)

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 maximum material removal. The minimum radiant exposures to achieve ablation at any wavelength were measured. The results suggest that most visible wavelengths were equally efficient at removing material at radiant exposures above threshold. Ablation was initiated at surface temperatures just above 100 degrees Celsius. A vapor bubble was formed during ablation. Less than 5% of the total pulse energy is coupled into the bubble energy. A large part of the delivered energy is unaccounted for and is likely released partly as acoustic transients from the vapor expansion and partly wasted as heat. The current laser and delivery systems may not be able to completely remove large clot burden that is sometimes encountered in heart attacks. However, laser thrombolysis may emerge as a favored treatment for strokes where the occlusion is generally smaller and rapid recanalization is of paramount importance. A final hypothesis is that laser thrombolysis should be done at radiant exposures close to threshold to minimize any damaging effects of the bubble dynamics on the vessel wall.

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

1997-05-01

45

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

46

Ablation parameters in KrF laser/plasma interaction: An experimental study  

NASA Astrophysics Data System (ADS)

Experimental measurements of ablation parameters in a KrF laser produced aluminum plasma are presented for the laser intensity range of 1011-1013 W/cm2. Plasma created from large focal spots shows single broad ion current pulses as compared to two groups of ions observed from small focal spots. Detailed analysis of the velocity distributions of emitted ions is carried out to understand this behavior and its effect on measurements of the ablation parameters. Scalings with laser intensity of the mass ablation rate (?˜I0.42L) and of the ablation pressure (Pa˜I0.81L) giving ?=1.5×105 g cm-2 sec-1 and Pa=5.5 Mbar at a laser intensity of 1013 W/cm2 are obtained. The results are found to be in good agreement with the predictions of a plasma ablation model based on inverse bremsstrahlung dominated absorption.

Gupta, P. D.; Tsui, Y. Y.; Popil, R.; Fedosejevs, R.; Offenberger, A. A.

1987-01-01

47

High-temperature transuranium organometallic species from laser ablation of actinide–polymer mixtures  

Microsoft Academic Search

Pulsed laser ablation of dispersions of f-element compounds in polymers produces novel `high-temperature' organometallic complex ions. The M+–L from reactions of metal ions (M+) with polymer fragments (L) in the ablation plume are identified by time-of-flight mass spectrometry. Compositions and abundances of M+–L from ablation of UO2 and lanthanides in polyimide (PI) reflected distinctive f-element chemistries; we report here on

John K Gibson

1998-01-01

48

XeCl laser ablation of polyetheretherketone  

NASA Astrophysics Data System (ADS)

Ablation of polyetheretherketone (PEEK), a high temperature thermoplastic, by XeCl laser radiation occurs at fluences in excess of 0.07±0.01 J cm-2. The volatile products of ablation are CO and C2H2 with smaller quantities of CH4, C4H2, C6H6 and other C3 and C4 hydrocarbons. At fluences close to the threshold ablation produces involatile material of relatively high molecular weight but at high fluences extensive disruption of the PEEK structure occurs with conversion of all of the oxygen in the polymer to carbon monoxide.

Dyer, P. E.; Oldershaw, G. A.; Schudel, D.

1990-11-01

49

On the Feasibility of Depth Profiling of Animal Tissue by Ultrashort Pulse Laser Ablation  

PubMed Central

Experiments were performed to examine the feasibility of MS depth profiling of animal tissue by ~75 fs, 800 nm laser pulses to expose underlying layers of tissue for subsequent MS analysis. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) was used to analyze phospholipids and proteins from both intact bovine eye lens tissue and tissue ablated by ultrashort laser pulses. Laser desorption postionization (LDPI-MS) with 10.5 eV single photon ionization was also used to analyze cholesterol and other small molecules in the tissue before and after laser ablation. Scanning electron microscopy was applied to examine the ablation patterns in the tissue and estimate the depth of the ablation craters. Ultrashort pulse laser ablation was found able to remove a layer of several tens of micrometers from the surface of eye lens tissue while leaving the underlying tissue relatively undamaged for subsequent MS analysis. MS analysis of cholesterol, phospholipids, peptides, and various unidentified species did not reveal any chemical damage caused by ultrashort pulse laser ablation for analytes smaller than ~6 kDa. However, a drop in intensity of larger protein ions was detected by MALDI-MS following laser ablation. An additional advantage was that ablated tissue displayed up to an order of magnitude higher signal intensities than intact tissue when subsequently analyzed by MS. These results support the use of ultrashort pulse laser ablation in combination with MS analysis to permit depth profiling of animal tissue. PMID:22482364

Milasinovic, Slobodan; Liu, Yaoming; Bhardwaj, Chhavi; Melvin, Blaze M.T.; Gordon, Robert J.; Hanley, Luke

2012-01-01

50

Quantifying the quality of femtosecond laser ablation of graphene  

NASA Astrophysics Data System (ADS)

The influence of beam intensity on laser ablation quality and ablation size is experimentally studied on graphene-coated silicon/silicon dioxide substrates. With an amplified femtosecond-pulsed laser system, by systematically decreasing the average power, periodic stripes with decreasing widths are ablated. Histogram analyses of the untouched and ablated regions of scanning electron microscope images of the fabricated structures make it possible to quantify the ablation quality. These analyses reveal that submicron ablation can be achieved while maintaining 75 % ablation accuracy by adjusting the beam intensity around the ablation threshold.

Sahin, Ramazan; Akturk, Selcuk; Simsek, Ergun

2014-08-01

51

Generation of Core/shell Nanoparticles with Laser Ablation  

E-print Network

Two types of core/shell nanoparticles (CS-NPs) generation based on laser ablation are developed in this study, namely, double pulse laser ablation and laser ablation in colloidal solutions. In addition to the study of the generation mechanism of CS...

Jo, Young Kyong

2012-10-19

52

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. PMID:21031139

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

2010-01-01

53

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. PMID:22191028

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

2011-01-01

54

Plume dynamics and shielding by the ablation plume during Er:YAG laser ablation  

Microsoft Academic Search

Free-running Er:YAG lasers are used for precise tissue abla- tion in various clinical applications. The ablated material is ejected into the direction perpendicular to the tissue surface. We investigated the influence of shielding by the ablation plume on the energy depo- sition into an irradiated sample because it influences the ablation dy- namics and the amount of material ablated. The

Kester Nahen; Alfred Vogel

2002-01-01

55

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

56

Reactions of Monovalent Metal Ions (M+) with Mixed Molecular Clusters (NH3)m(H2O)n as Studied by Laser-Ablation Molecular Beam (lamb) Method:. Preferred or Nonspecific Coordination  

Microsoft Academic Search

Three distinct types of competitive solvation around monopositive metal ions in the gas phase have been revealed by the laser-ablation molecular beam method using binary clusters in the molecular beam: (i) preferred solvation of one of the two components, (ii) essentially nonselective solvation, and (iii) magic-number-like behavior of one component in the presence of the other component in the outer

H. Sato; A. Matsuzaki; S. Nishio; Y. Horiki; O. Ito

1996-01-01

57

Optical analysis of the ablation processes in pulsed laser deposition  

E-print Network

in the laser-target and laser-plasma interactions. As laser light strikes the target, it is absorbed via material that is ablated from a target by interaction with a high fluence, pulsed laser. One disadvantage is ablated from a target by interaction with a high fluence, pulsed laser beam and deposited onto a substrate

Reilly, Anne

58

What can We Learn about Atmospheric Meteor Ablation and Light Production from Laser Ablation?  

Microsoft Academic Search

Laboratory based laser ablation techniques can be used to study the size of the luminous region, predict spectral features, estimate the luminous efficiency factor, and assess the role of chemically differentiated thermal ablation. A pulsed Nd:YAG laser was used to ablate regions from ordinary and carbonaceous chondrite meteorites. CCD cameras and a digital spectroscope were used to measure the size

R. L. Hawkes; E. P. Milley; J. M. Ehrman; R. M. Woods; J. D. Hoyland; C. L. Pettipas; D. W. Tokaryk

2008-01-01

59

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition  

SciTech Connect

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

Geohegan, D.B.

1994-09-01

60

Analysis of metallic fuels by laser ablation  

Microsoft Academic Search

A hot cell-based solid sampling system has been developed for application to the analyses of irradiated materials such as metallic reactor fuel from a nuclear reactor, and radioactive waste forms. This system employs one of two sampling techniques, glow discharge or laser ablation, for introduction of material into one of two instruments for analysis, either a time of flight mass

Stephen G. Johnson; Phillip S. Goodall; Sandra M. Kimbrell; Elon L. Wood

1995-01-01

61

Laser ablation mechanism of transparent dielectrics with picosecond laser pulses  

NASA Astrophysics Data System (ADS)

Thin glass sheets (thickness <1 mm) have a great potential in OLED and LCD displays. While the conventional manufacturing methods, such as mechanical scribing and breaking, result in poor edge strength, ultra-short-pulsed laser processing could be a promising solution, offering high-quality cutting edges. However laser precision glass cutting suffers from unwanted material modification and even severe damage (e.g. cracks and chipping). Therefore it is essential to have a deep understanding of the ultra-short-pulsed laser ablation mechanism of transparent dielectrics in order to remedy those drawbacks. In this work, the ablation mechanism of transparent dielectrics irradiated by picosecond laser pulses has been studied. Ultrafast dynamics of free-electrons is analyzed using a rate equation for free-electron density including multi-photon ionization, avalanche ionization and loss terms. Two maps of free-electron density in parameter space are given to discuss the dependence of ablation threshold intensity/fluence on pulse duration. The laser ablation model describing laser beam propagation and energy deposition in transparent dielectrics is presented. Based on our model, simulations and experiments have been performed to study the ablation dynamics. Both simulation and experimental results show good agreement, offering great potential for optimization of laser processing in transparent dielectrics. The effects of recombination coefficient and electron-collision time on our model are investigated.

Sun, Mingying; Eppelt, Urs; Russ, Simone; Hartmann, Claudia; Siebert, Christof; Zhu, Jianqiang; Schulz, Wolfgang

2012-11-01

62

Picosecond laser ablation of porcine sclera  

NASA Astrophysics Data System (ADS)

Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer's solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30?m. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.

Góra, Wojciech S.; Harvey, Eleanor M.; Dhillon, Baljean; Parson, Simon H.; Maier, Robert R. J.; Hand, Duncan P.; Shephard, Jonathan D.

2013-03-01

63

A Review of Laser Ablation Propulsion  

NASA Astrophysics Data System (ADS)

Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Sänger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing ``Lightcraft'' and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important rôle in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

Phipps, Claude; Bohn, Willy; Lippert, Thomas; Sasoh, Akihiro; Schall, Wolfgang; Sinko, John

2010-10-01

64

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

2012-02-01

65

Ablative corona driven by light ion beam  

Microsoft Academic Search

A theoretical model is presented describing the spatial structure and scaling laws for the ablative corona generated by the incidence of an intense light ion beam pulse on a spherical pellet. This treatment differs, from an earlier model in the assumption that the beam velocity vb is higher than the electron thermal velocity vThe everywhere, which allows one to obtain

A R Piriz

1986-01-01

66

Simulation of femtosecond laser ablation of silicon  

NASA Astrophysics Data System (ADS)

Femtosecond laser ablation is an important process in micromachining and nanomachining of microelectronic, optoelectronic, biophotonic and MEMS components. The process of laser ablation of silicon is being studied on an atomic level using molecular dynamics simulations. We investigate ablation thresholds for Gaussian laser pulses of 800 nm wavelength, in the range of a few hundred femtoseconds in duration. Absorption is modelled via linear and 2-photon absorption processes into a hot electron bath which then transfers energy into the crystal lattice. The simulation box is a narrow column approximately 5.4 nm x 5.4 nm x 81 nm with periodic boundaries in the x and y transverse directions and a 1-D heat flow model at the bottom coupled to a heat bath to simulate an infinite bulk medium corresponding to the solid bulk material. A modified Stillinger-Weber potential is used to model the silicon atoms. The calculated thresholds are compared to various reported experimental values for the ablation threshold of silicon. We provide an overview of the code and discuss the simulation techniques used.

Holenstein, Roman; Kirkwood, Sean E.; Fedosejevs, Robert; Tsui, Ying Y.

2004-11-01

67

Metabolic transformation of microalgae due to light acclimation and genetic modifications followed by laser ablation electrospray ionization mass spectrometry with ion mobility separation.  

PubMed

Metabolic profiling of various microalga species and their genetic variants, grown under varied environmental conditions, has become critical to accelerate the exploration of phytoplankton biodiversity and biology. The accumulation of valuable metabolites, such as glycerolipids, is also sought in microalgae for biotechnological applications ranging from food, feed, medicine, cosmetics to bioenergy and green chemistry. In this report we describe the direct analysis of metabolites and lipids in small cell populations of the green alga Chlamydomonas reinhardtii, using laser ablation electrospray ionization (LAESI) mass spectrometry (MS) coupled with ion mobility separation (IMS). These microorganisms are capable of redirecting energy storage pathways from starch to neutral lipids depending on environmental conditions and nutrient availability. Metabolite and lipid productions were monitored in wild type (WT), and genetically modified C. reinhardtii strains with an impaired starch pathway. Lipids, such as triacylglycerols (TAG) and diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), were monitored over time under altered light conditions. More than 200 ions related to metabolites, e.g., arginine, cysteine, serine, palmitate, chlorophyll a, chlorophyll b, etc., were detected. The lipid profiles at different light intensities for strains with impaired starch pathway (Sta1 and Sta6) contained 26 glycerolipids, such as DGTS, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), as well as 33 TAG species. Results were obtained over a 72 hour time period under high and low light conditions for the WT species and the two mutants. Our results indicate that LAESI-IMS-MS can be utilized for the rapid analysis of increased TAG production at elevated light intensities. Compared to WT, the Sta6 strain showed 2.5 times higher lipid production at 72 hours under high light conditions. The results demonstrate our ability to rapidly observe numerous changes in metabolite and lipid levels in microalgal population. These capabilities are expected to facilitate the exploration of genetically altered microalgal strains for biofuel production. PMID:25254963

Stopka, Sylwia A; Shrestha, Bindesh; Maréchal, Eric; Falconet, Denis; Vertes, Akos

2014-10-15

68

Mechanism study of skin tissue ablation by nanosecond laser pulses  

Microsoft Academic Search

Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to

Qiyin Fang

2002-01-01

69

Specific Impulse Definition for Ablative Laser Propulsion  

NASA Technical Reports Server (NTRS)

The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

Herren, Kenneth A.; Gregory, Don A.

2004-01-01

70

Plume dynamics and shielding by the ablation plume during Er:YAG laser ablation.  

PubMed

Free-running Er:YAG lasers are used for precise tissue ablation in various clinical applications. The ablated material is ejected into the direction perpendicular to the tissue surface. We investigated the influence of shielding by the ablation plume on the energy deposition into an irradiated sample because it influences the ablation dynamics and the amount of material ablated. The investigations were performed using an Er:YAG laser with a pulse duration of 200 micros for the ablation of gelatin with different water contents, skin, and water. Laser flash photography combined with a dark field Schlieren technique was used to visualize gaseous and particulate ablation products, and to measure the distance traveled by the ablating laser beam through the ablation plume at various times after the beginning of the laser pulse. The temporal evolution of the transmission through the ablation plume was probed using a second free running Er:YAG laser beam directed parallel to the sample's surface. The ablation dynamics was found to consist of a vaporization phase followed by material ejection. The observation of droplet ejection during water ablation provided evidence that a phase explosion is the driving mechanism for material ejection. The laser light transmission was only slightly reduced by the vapor plume, but decreased by 25%-50% when the ejected material passed the probe beam. At radiant exposures approximately 10 times above the ablation threshold, the laser energy deposited into the sample amounted to only 61% of the incident energy for gelatin samples with 90% water content and to 86% for skin samples. For free-running Er:YAG laser pulses shielding must therefore be considered in modeling the ablation dynamics and determining the dosage for clinical applications. PMID:11966301

Nahen, Kester; Vogel, Alfred

2002-04-01

71

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

72

Solar cell contact formation using laser ablation  

DOEpatents

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

Harley, Gabriel; Smith, David; Cousins, Peter

2012-12-04

73

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

74

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

75

Formation of wide bandgap cerium oxide nanoparticles by laser ablation in aqueous solution  

NASA Astrophysics Data System (ADS)

Cerium oxide nanoparticles were produced by laser ablation in an aqueous solution. Submicron-sized cerium oxide particles were size-reduced by pulsed-laser irradiation into those having diameters of 3.6 nm. It was found that the bandgap of the nanoparticle was larger and the Ce3+ concentration within it was higher than those prepared by other conventional methods. These characteristic structures are likely to originate from additional defect sites in the nanoparticles produced by laser ablation, where O2- ions have a lower coordination with Ce ions, resulting in removal of O atoms and reduction of Ce4+ into Ce3+.

Takeda, Yoshihiro; Mafuné, Fumitaka

2014-04-01

76

Femtosecond laser ablation properties of borosilicate glass Adela Ben-Yakara)  

E-print Network

Femtosecond laser ablation properties of borosilicate glass Adela Ben-Yakara) Mechanical) We study the femtosecond laser ablation properties of borosilicate glass using atomic force. We present a detailed examination of the femtosecond laser ablation properties of borosilicate glass

Byer, Robert L.

77

What can We Learn about Atmospheric Meteor Ablation and Light Production from Laser Ablation?  

Microsoft Academic Search

Laboratory based laser ablation techniques can be used to study the size of the luminous region, predict spectral features,\\u000a estimate the luminous efficiency factor, and assess the role of chemically differentiated thermal ablation. A pulsed Nd:YAG\\u000a laser was used to ablate regions from ordinary and carbonaceous chondrite meteorites. CCD cameras and a digital spectroscope\\u000a were used to measure the size

R. L. Hawkes; E. P. Milley; J. M. Ehrman; R. M. Woods; J. D. Hoyland; C. L. Pettipas; D. W. Tokaryk

2008-01-01

78

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

SciTech Connect

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.; Ganesh, R.; Joshi, H. C. [Institute for Plasma Research, Bhat, Gandhinagar-382428 (India)] [Institute for Plasma Research, Bhat, Gandhinagar-382428 (India); Ashwin, J. [Weizmann Institute of Science, Rehovot - 76100 (Israel)] [Weizmann Institute of Science, Rehovot - 76100 (Israel)

2013-08-15

79

Ablative expansion plasmas in light ion beam fusion  

Microsoft Academic Search

The ablative, quasisteady expansion flow of a plasma generated by impinging a pellet by an intense light ion beam pulse is analysed. Profile of beam density and velocity and plasma density, velocity, and temperatures as functions of the radius are obtained from the analysis. The ablation pressure Pa and the ablated mass rate, for a given pellet radius ra, are

J Sanz; A Velazquez; L Rosety; A Barrero

1985-01-01

80

Sulphur selective ablation by UV laser  

NASA Astrophysics Data System (ADS)

In this work we report the preliminary experimental results on the selective ablation of sulphur in ancient stones. The sulphur concentration was reduced after laser action. For this goal an excimer laser operating at 308 nm wavelength and time duration of 20 ns was used. In order to estimate the sulphur concentration before and after laser cleaning, a portable apparatus for energy-dispersive X-ray fluorescence (EDXRF) was utilised. The processed sample were characterized by an initial sulphur concentration of 2.8% w/w. After the laser treatment, sulphur concentration decreased after a total deposited energy of about 30 J/cm2 up to 1.2% w/w value. Due to the porosity of the stone, in fact, it is difficult to eliminate completely the S presence in the composition of the stones. It was also observed that after a few laser shots the initial black area of the stone became white showing in this way the great potential of the laser action on the cleaning process of the pietra leccese.

Lorusso, Antonella; Nassisi, Vincenzo; Belloni, Fabio; Buccolieri, Giovanni; Caretto, Giuseppe; Castellano, Alfredo

2005-06-01

81

RESEARCH Open Access Focal Laser Ablation of Prostate Cancer  

E-print Network

RESEARCH Open Access Focal Laser Ablation of Prostate Cancer: Numerical Simulation of Temperature between simulation and in vivo experiments of FLA for prostate cancer. Simulation is a promising planning surgical method. Keywords: Prostate cancer focal laser ablation, thermal damage, bioheat transfer

Paris-Sud XI, Université de

82

Pulsed laser ablation of solids and critical phenomena  

Microsoft Academic Search

We consider the possible manifestations of critical phenomena under pulsed laser ablation (PLA). The mechanism of phase explosion under nanosecond laser ablation is considered and the possibility of estimating the critical temperature from PLA experiments is discussed. A model based on the Euler equations and generalized van der Waals equation is developed to describe rarefaction shock waves (RSW) in near-critical

Nadezhda M Bulgakova; Alexander V Bulgakov; Igor M Bourakov; Natalia A Bulgakova

2002-01-01

83

Mechanism study of skin tissue ablation by nanosecond laser pulses  

NASA Astrophysics Data System (ADS)

Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed. A laser-induced and localized thermal ionization pathway has been investigated and it was found to have significant influence on the initial free electron density during plasma formation due to the combination of strong light absorption by chromophores and confined temperature rise in the chromophores. Good agreements have been found between the new plasma-mediated ablation model and experimental results. The implications of this dissertation research to the future improvement of laser systems in dermatology and plastic surgery are discussed.

Fang, Qiyin

84

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

85

Femtosecond laser ablation of brass in air and liquid media  

NASA Astrophysics Data System (ADS)

Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

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

2013-06-01

86

Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation  

SciTech Connect

A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm{sup 2}. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown.

Autrique, D. [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany) [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany); Department of Chemistry, University of Antwerp, 2610 Wilrijk (Belgium); Gornushkin, I. [Federal Institute for Materials Research and Testing - BAM, 12489 Berlin (Germany)] [Federal Institute for Materials Research and Testing - BAM, 12489 Berlin (Germany); Alexiades, V. [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1320 (United States)] [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1320 (United States); Chen, Z.; Bogaerts, A. [Department of Chemistry, University of Antwerp, 2610 Wilrijk (Belgium)] [Department of Chemistry, University of Antwerp, 2610 Wilrijk (Belgium); Rethfeld, B. [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany)] [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany)

2013-10-21

87

Dynamics of femtosecond laser-produced plasma ions  

NASA Astrophysics Data System (ADS)

We investigated the ion laser-produced plasma plume generated during ultrafast laser ablation of copper and silicon targets in high vacuum. The ablation plasma was induced by ?50 fs, 800 nm Ti:Sa laser pulses irradiating the target surface at an angle of 45°. An ion probe was used to investigate the time-of-flight profiles of the emitted ions in a laser fluence range from the ablation threshold up to ?10 J/cm2. The angular distribution of the ion flux and average velocity of the produced ions were studied by moving the ion probe on a circle around the ablation spot. The angular distribution of the ion flux is well described by an adiabatic and isentropic model of expansion of a plume produced by laser ablation of solid targets. The angular distribution of the ion flux narrows as the laser pulse fluence increases. Moreover, the ion average velocity reaches values of several tens of km/s, evidencing the presence of ions with kinetic energy of several hundred eV. Finally, the ion flux energy is confined in a narrow angular region around the target normal.

Ni, Xiaochang; Anoop, K. K.; Wang, X.; Paparo, D.; Amoruso, S.; Bruzzese, R.

2014-10-01

88

Diagnostics and applications of ultrashort pulsed laser ablation /  

E-print Network

ultra-short and high power pulsed laser system to study laser plasma interactions has attracted people will tell us the composition of the plasma plume and help us to study pulsed laser deposition. Eizel lens of plasma plume in pulsed laser ablation. In this work, we have designed and constructed Eizel lens and time

89

Silica nano-ablation using laser plasma soft x-rays  

NASA Astrophysics Data System (ADS)

We have investigated nano-ablation of silica glass and ablation process using focused laser plasma soft Xrays. Laser plasma soft X-rays were generated by irradiation of a Ta target with Nd:YAG laser light. The soft X-rays were focused on silica glass plates using an ellipsoidal mirror at fluences up to 1 J/cm2. In order to fabricate nano-trenches, a silica glass plate was irradiated with laser plasma soft X-rays through the windows of a line and space mask. We demonstrated fabrication of nano-trenches with a width of 50 nm. It should be noted that the feature size is more precise than that estimated from the thermal diffusion length for the 10-ns X-rays (i.e. 80 nm). Furthermore, the ablated area has a depth of 470 nm and a roughness of 1 nm after ten shots of irradiation. Thus, the X-ray irradiation technique have a significant feature of direct nanomachining. The ablation occurs at fluences F beyond a ablation threshould Fth and ablation depth per pulse D obeys the law D = 1/? ln(F/Fth), where ? is an effective absorption coefficient. These results suggest that absorbed energy is accumulated in the absorbed region without energy diffusion until ablation occurs. In addition, time-resolved mass spectroscopy revealed that silica glass is broken into atomic ions and atomic neutrals during ablation. Because Si+ and O+ ions have kinetic energies of 10-30 eV, non-thermal process such as Coulomb explosion may be driving force behind the ablation. Such non-thermal process enables us to fabricate nano-structures on silica glass.

Makimura, Tetsuya; Torii, Shuichi; Niino, Hiroyuki; Murakami, Kouichi

2009-05-01

90

UV laser ablation of parylene films from gold substrates  

SciTech Connect

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 atmospheric pressure, and vacuum. The laser-induced craters were analyzed by optical microscopy and x-ray photoelectron spectroscopy. Multi-pulse ablation thresholds of gold and parylene were estimated.

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

2009-11-19

91

Energy efficiency of femtosecond laser ablation of polymer materials  

NASA Astrophysics Data System (ADS)

We present the results of an experimental study of the ablation spectral energy thresholds for a number of polymer materials ((C2F4) n , (CH2O) n ) exposed to femtosecond (?0.5 ~ 45-70 fs) laser pulses (? ~ 266, 400, 800 nm) under atmospheric conditions and under vacuum ( p ~ 10-2 Pa). We have analyzed the energy thresholds and the efficiency of optical, thermophysical, and gasdynamic processes in laser ablation vs. the laser pulse duration and photon energy.

Loktionov, E. Yu.; Ovchinnikov, A. V.; Protasov, Yu. Yu.; Protasov, Yu. S.; Sitnikov, D. S.

2012-03-01

92

A fundamental study of excimer laser ablation using experimental and MD simulation method  

Microsoft Academic Search

This paper focuses on the effect of pulse duration on ablation rate and behavior of plume in excimer laser ablation. Experimental results of laser ablation demonstrate that the 200 ns pulse laser exhibits a four to five times larger ablation rate than that with 20 ns pulse for the same laser fluence. CCD photography reveals that the plume velocity exceeds

Kazuo Horiuchi; Masafumi Ishiyama; Tadashi Hasebe; Ken Yukimura; Yutaka Imaida

1998-01-01

93

Experimental investigation of the laser ablation process on wood surfaces  

NASA Astrophysics Data System (ADS)

Processing of wood by conventional mechanical tools like saws or planes leaves behind a layer of squeezed wood only slightly adhering to the solid wood surface. Laser ablation of this layer could improve the durability of coatings and glued joints. For technical applications, thorough knowledge about the laser ablation process is necessary. Results of ablation experiments by excimer lasers, Nd:YAG lasers, and TEA-CO 2 lasers on surfaces of different wood types and cut orientations are shown. The process of ablation was observed by a high-speed camera system and optical spectroscopy. The influence of the experimental parameters are demonstrated by SEM images and measurement of the ablation rate depending on energy density. Thermal effects like melting and also carbonizing of cellulose were found for IR- and also UV-laser wavelengths. Damage of the wood surface after laser ablation was weaker for excimer lasers and CO 2-TEA lasers. This can be explained by the high absorption of wood in the ultraviolet and middle infrared spectral range. As an additional result, this technique provides an easy way for preparing wood surfaces with excellently conserved cellular structure.

Panzner, M.; Wiedemann, G.; Henneberg, K.; Fischer, R.; Wittke, Th.; Dietsch, R.

1998-05-01

94

Laser ablation system, and method of decontaminating surfaces  

DOEpatents

A laser ablation system comprising a laser head providing a laser output; a flexible fiber optic cable optically coupled to the laser output and transmitting laser light; an output optics assembly including a nozzle through which laser light passes; an exhaust tube in communication with the nozzle; and a blower generating a vacuum on the exhaust tube. A method of decontaminating a surface comprising the following steps: providing an acousto-optic, Q-switched Nd:YAG laser light ablation system having a fiber optically coupled output optics assembly; and operating the laser light ablation system to produce an irradiance greater than 1.times.10.sup.7 W/cm.sup.2, and a pulse width between 80 and 170 ns.

Ferguson, Russell L. (Idaho Falls, ID); Edelson, Martin C. (Ames, IA); Pang, Ho-ming (Ames, IA)

1998-07-14

95

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

96

Dynamics of laser ablated colliding plumes  

SciTech Connect

We report the dynamics of single and two collinearly colliding laser ablated plumes of ZnO studied using fast imaging and the spectroscopic measurements. Two dimensional imaging of expanding plume and temporal evolution of various species in interacting zones of plumes are used to calculate plume front velocity, electron temperature, and density of plasma. The two expanding plumes interact with each other at early stage of expansion ({approx}20 ns) resulting in an interaction zone that propagates further leading to the formation of stagnation layer at later times (>150 ns) at the lateral collision front of two plumes. Colliding plumes have larger concentration of higher ionic species, higher temperature, and increased electron density in the stagnation region. A one-to-one correlation between the imaging and optical emission spectroscopic observations in interaction zone of the colliding plumes is reported.

Gupta, Shyam L.; Pandey, Pramod K.; Thareja, Raj K. [Department of Physics, Indian Institute of Technology, Kanpur-208016 (India)

2013-01-15

97

Formation of tribological structures by laser ablation  

NASA Astrophysics Data System (ADS)

Many technical applications can benefit from the use of tribological structures in minimizing abrasive material wear and energy consumption without the integration of additional materials in a working assembly. Especially in lubricated friction systems, the tribological character can be significantly improved through the addition of oriented and repetitive microstructure. In this study, experimental tests are discussed for a small range of structure dimensions to verify the effect of optimizing the tribological contact performance. A nanosecond pulsed fiber laser is used to create various test structures with different sizes and form. The quality of the fabricated surface pattern, particularly form correctness, feathering and material modification effects of the ablated area is characterized and optimized. The influence of pulse duration, pulse energy and pulse delay using normal pulsing is presented and compared to various burst modes.

Schilling, Niels; Paschke, Mike; Hendow, Sami T.; Klotzbach, Udo

2012-03-01

98

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., Jr.

1995-04-01

99

Laser ablation dynamics in metals: The thermal regime  

NASA Astrophysics Data System (ADS)

We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

Mezzapesa, F. P.; Columbo, L. L.; Brambilla, M.; Dabbicco, M.; Ancona, A.; Sibillano, T.; Scamarcio, G.

2012-07-01

100

Quantification of polyimide carbonization after laser ablation  

NASA Astrophysics Data System (ADS)

Polyimide was irradiated with a XeCl excimer laser (308 nm) and the ablated area and its surrounding were studied using transmission electron microscopy (TEM) and confocal Raman microscopy. Ring-like structures surrounding the ablated area were detected at all fluences. At fluences lower than 250 mJ/cm-2 the formation of conical structures was observed within the irradiated area. The width of the rings increases with fluence and only slightly with the number of pulses. The rings consist mainly of polycrystalline carbon with a relatively high bond angle disorder, with thickness decreasing radially from the crater edge. The thickness of the deposited carbon was determined from TEM analysis and calculated from the intensity ratios of Raman bands assigned to carbon and polyimide using a two layer model. Comparing the two results an estimate of the absorption coefficient of the deposited carbon could be obtained. On top of the cone structures carbon was detected with a higher degree of crystallinity and lower bond angle disorder as compared to the material deposited outside the crater. With energy dispersive x-ray analysis, calcium could be detected on top of the cones. Therefore, it can be assumed that the Ca impurities are causing the cone structures. The higher crystallinity of the carbon inside the irradiated area is probably due to a tempering-like process on top of the Ca compound which is heated upon laser irradiation or to a mixture of growth mechanisms similar to the ones suggested for the formation of carbon nanotubes on metal particles and carbon nanohorns without metal catalysis.

Raimondi, F.; Abolhassani, S.; Brütsch, R.; Geiger, F.; Lippert, T.; Wambach, J.; Wei, J.; Wokaun, A.

2000-09-01

101

Osteoid Osteoma: Experience with Laser- and Radiofrequency-Induced Ablation  

SciTech Connect

The purpose of this study was to analyze the clinical outcome of osteoid osteoma treated by thermal ablation after drill opening. A total of 17 patients and 20 procedures were included. All patients had typical clinical features (age, pain) and a typical radiograph showing a nidus. In 5 cases, additional histological specimens were acquired. After drill opening of the osteoid osteoma nidus, 12 thermal ablations were induced by laser interstitial thermal therapy (LITT) (9F Power-Laser-Set; Somatex, Germany) and 8 ablations by radiofrequency ablation (RFA) (RITA; StarBurst, USA). Initial clinical success with pain relief has been achieved in all patients after the first ablation. Three patients had an osteoid osteoma recurrence after 3, 9, and 10 months and were successfully re-treated by thermal ablation. No major complication and one minor complication (sensible defect) were recorded. Thermal ablation is a safe and minimally invasive therapy option for osteoid osteoma. Although the groups are too small for a comparative analysis, we determined no difference between laser- and radiofrequency-induced ablation in clinical outcome after ablation.

Gebauer, Bernhard [Charite, Medical University Berlin, Department of Radiology (Germany)], E-mail: bernhard.gebauer@charite.de; Tunn, Per-Ulf [Charite, Medical University Berlin, Department of Surgery and Surgical Oncology (Germany); Gaffke, Gunnar [Charite, Medical University Berlin, Department of Radiology (Germany); Melcher, Ingo [Charite, Medical University Berlin, Campus Virchow-Clinic, Department of Trauma and Reconstructive Surgery (Germany); Felix, Roland; Stroszczynski, Christian [Charite, Medical University Berlin, Department of Radiology (Germany)

2006-04-15

102

Laser ablation of paper: Raman identification of products  

NASA Astrophysics Data System (ADS)

Old paper samples are bleached using pulsed laser radiation with a wavelength of 532 nm. The ablation products of five paper samples that differ by composition and production dates are studied using Raman microspectroscopy. Cellulose, protein, calcite, titanium dioxide (anatase, rutile, and brookite), quartz, lazurite, bonattite, and dolomite are identified as ablation products.

Balakhnina, Irina; Brandt, Nikolay; Chikishev, Andrey; Rebrikova, Natalia; Yurchuk, Yuliya

2014-11-01

103

Acoustic online monitoring of IR laser ablation of burnt skin  

Microsoft Academic Search

In burn surgery necrotic tissue has to be removed prior to grafting. Tangential excision causes high blood loss and destruction of viable tissue. Pulsed infrared laser ablation can overcome both problems because of its high precision and the superficial coagulation of the remaining tissue. We investigated the ablation noise to realize an acoustic feedback system for a selective removal of

Kester Nahen; Alfred Vogel

1999-01-01

104

Performance and Controllability of Pulsed Ion Beam Ablation Propulsion  

Microsoft Academic Search

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 mumt), 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

Masaru Yazawa; Chainarong Buttapeng; Hisayuki Suematsu; Weihua Jiang; Kiyoshi Yatsui; Nobuhiro Harada

2006-01-01

105

Enhancement of pulsed laser ablation in environmentally friendly liquid.  

PubMed

Enhancement of pulsed laser ablation can be achieved in acetic acid as an environmentally friendly liquid. This paper evaluates microholes and textured features induced by a nanosecond pulsed laser under different processing circumstances. The microholes are fabricated by laser drilling in acetic acid and found to be 100% deeper than in air. The textured features achieved in the liquid demonstrate a higher content of Copper and a lower content of Oxygen. The improvement of laser ablation efficiency in the liquid is attributed to the strong confinement of plasma plume accompanying with shockwave and cavitation bubbles. Meanwhile, the laser enhanced chemical etching by the weak acid plays a critical role. PMID:25321965

Luo, Fangfang; Guan, Yingchun; Ong, Weili; Du, Zheren; Ho, Ghimwei; Li, Fengping; Sun, Shufeng; Lim, Gniancher; Hong, Minghui

2014-10-01

106

Laser Ablation of Aluminium: Drops and Voids Johannes Roth1  

E-print Network

Laser Ablation of Aluminium: Drops and Voids Johannes Roth1 , Johannes Karlin1 , Christian Ulrich2 as a #12;2 Johannes Roth et al pollution. Or they can stay in the hole and fill it up. Void formation

Roth, Johannes

107

Selective material ablation by the TEA CO2 laser  

NASA Astrophysics Data System (ADS)

This paper reports two topics in the material processing using TEA CO2 lasers. We demonstrated selective ablation of hydrogenated amorphous silicon (a-Si:H) thin layer on a quartz substrate by the second harmonic (SH) radiation of TEA CO2 laser generated by AgGaSe2 nonlinear crystal. Si-H bonds contained in a-Si:H strongly absorb the 5 micrometers SH radiation and resulted in the selective ablation of the a-Si:H layer. The successful ablation processing of ethylenetetrafluoroethylene (ETFE) copolymer by the 9.6 micrometers fundamental wavelength TEA CO2 laser is also reported. Only ETFE thin film adhered to an aluminum substrate can be ablated by the TEA CO2 laser.

Sumiyoshi, Tetsumi; Shiratori, Akira; Ninomiya, Yutaka; Obara, Minoru

1995-03-01

108

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

109

Tissue ablation through water with erbium: YAG lasers  

Microsoft Academic Search

The authors report the dynamics of vapor cavities generated by 200 mu s long Er:YAG laser pulses under water and in gelatin. Acoustic transients were detected at the beginning of the laser pulse and when the cavity collapsed. Cavity expansion and collapse, and the associated acoustic transients are possible ablation mechanisms with the Er:YAG laser. Shortening of the pulse duration

H. Loertscher; W. Q. Shi; W. S. Grundfest

1992-01-01

110

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

111

Discharge-aided reactive laser ablation for ultrafine powder production  

Microsoft Academic Search

Ultrafine alumina powder was produced by aluminum target ablation with a Nd:YAG laser beam (1064 nm wavelength; 340 mJ\\/pulse energy; 7 ns pulse duration; 10 pps repetition rate), in a 120 Torr O2 atmosphere. A theoretical approach for the ablation process, based on laser energy absorption and energy balance in the target, is used for comparison with the experimental production

Ioan Chis; A. Marcu; T. Yukawa; Dumitru Dragulinescu; Constantin Grigoriu; Dana Miu; Weihua Jiang; Kiyoshi Yatsui

1998-01-01

112

Laser ablation for the synthesis of carbon nanotubes  

DOEpatents

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Holloway, Brian C; Eklund, Peter C; Smith, Michael W; Jordan, Kevin C; Shinn, Michelle

2012-11-27

113

Laser ablation for the synthesis of carbon nanotubes  

NASA Technical Reports Server (NTRS)

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of side pumped, preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2010-01-01

114

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

115

Transient Newton rings in dielectrics upon fs laser ablation  

E-print Network

We report the appearance of transient Newton rings in dielectrics (sapphire and lead-oxide glass) during ablation with single fs laser pulses. Employing femtosecond microscopy with 800 nm excitation and 400 nm illumination, we observe a characteristic ring pattern that dynamically changes for increasing delay times between pump and probe pulse. Such transient Newton rings have been previously observed in metals and semiconductors at fluences above the ablation threshold and were related to optical interference of the probe beam reflected at the front surface of the ablating layer and at the interface of the non-ablating substrate. Yet, it had been generally assumed that this phenomenon cannot be (and has not been) observed in dielectrics due to the different ablation mechanism and optical properties of dielectrics. The fact that we are able to observe them has important consequences for the comprehension of the ablation mechanisms in dielectrics and provides a new method for investigating these mechanisms in ...

Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Solis, Javier

2014-01-01

116

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

117

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

118

Mechanisms of Carbon Nanotube Production by Laser Ablation Process  

NASA Technical Reports Server (NTRS)

We will present possible mechanisms for nanotube production by laser oven process. Spectral emission of excited species during laser ablation of a composite graphite target is compared with that of laser irradiated C60 vapor. The similarities in the transient and spectral data suggest that fullerenes are intermediate precursors for nanotube formation. The confinement of the ablation products by means of a 25-mm diameter tube placed upstream of the target seems to improve the production and purity of nanotubes. Repeated laser pulses vaporize the amorphous/graphitic carbon and possibly catalyst particles, and dissociate fullerenes yielding additional feedstock for SWNT growth.

Scott, Carl D.; Arepalli, Sivaram; Nikolaev, Pavel; Smalley, Richard E.; Nocholson, Leonard S. (Technical Monitor)

2000-01-01

119

Histological analysis of a cornea following experimental femtosecond laser ablation.  

PubMed

: Corneal photorefractive surgery is currently performed by ablation of corneal stroma under the stromal flap. A stromal flap is created using a femtosecond (FS) laser or mechanical microkeratome, although the FS laser procedure is considered safer and more accurate. This review assesses and compares the use of FS laser versus mechanical microkeratome ablation for corneal stromal characteristics mainly examined by histology and cellular biological responses. Supporting data from our studies, using corneas of enucleated porcine eye globes, are included in this review. Histological analysis and experimental studies of cellular/tissue responses to FS laser irradiation should be further investigated, and the equipment used to perform these techniques should be improved. PMID:25289720

Sumioka, Takayoshi; Miyamoto, Takeshi; Takatsuki, Reiko; Okada, Yuka; Yamanaka, Osamu; Saika, Shizuya

2014-11-01

120

Hydrodynamic Efficiency of Ablation Propulsion with Pulsed Ion Beam  

SciTech Connect

This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam on the basis of the ion beam-target interaction. We used a one-dimensional hydrodynamic fluid compressible to study the physics involved namely an ablation acceleration behavior and analyzed it as a rocketlike model in order to investigate its hydrodynamic variables for propulsion applications. These variables were estimated by the concept of ablation driven implosion in terms of ablated mass fraction, implosion efficiency, and hydrodynamic energy conversion. Herein, the energy conversion efficiency of 17.5% was achieved. In addition, the results show maximum energy efficiency of the ablation process (ablation efficiency) of 67% meaning the efficiency with which pulsed ion beam energy-ablation plasma conversion. The effects of ion beam energy deposition depth to hydrodynamic efficiency were briefly discussed. Further, an evaluation of propulsive force with high specific impulse of 4000s, total impulse of 34mN and momentum to energy ratio in the range of {mu}N/W was also analyzed.

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

2006-05-02

121

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

122

Ultrashort laser ablation of PMMA and intraocular lenses  

NASA Astrophysics Data System (ADS)

The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials, techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular lenses, and thus provide an alternative to conventional techniques. Ablation experiments were conducted using various polymer substrates (PMMA samples, hydrophobic acrylic IOL, yellow azo dye doped IOL, and hydrophilic acrylic IOL consist of 25% H2O). The irradiation was performed using 100 fs pulses of 800 nm radiation from a regeneratively amplified Ti:sapphire laser system. We investigated the ablation efficiency and the phenomenology of the ablated patterns by probing the ablation depth using a profilometer. The surface modification was examined using a high resolution optical microscope (IOLs) or atomic force microscope—AFM (PMMA samples). It was found that different polymers exhibited different ablation characteristics, a result that we attribute to the differing optical properties of the materials. In particular, it was observed that the topography of the ablation tracks created on the hydrophilic intraocular lenses was smoother in comparison to those created on the PMMA and hydrophobic lens. The yellow doped hydrophobic intraocular lenses show higher ablation efficiency than undoped hydrophobic acrylic lenses.

Serafetinides, A. A.; Makropoulou, M.; Fabrikesi, E.; Spyratou, E.; Bacharis, C.; Thomson, R. R.; Kar, A. K.

2008-10-01

123

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

124

Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air  

NASA Astrophysics Data System (ADS)

Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences.

Wang, Z. B.; Hong, M. H.; Lu, Y. F.; Wu, D. J.; Lan, B.; Chong, T. C.

2003-05-01

125

Plasma mediated ablation of biological tissues with ultrashort laser pulses  

SciTech Connect

Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

Oraevsky, A.A. [Lawrence Livermore National Lab., CA (United States)]|[Rice Univ., Houston, TX (United States). Dept. of Electrical Engineering; DaSilva, L.B.; Feit, M.D. [Lawrence Livermore National Lab., CA (United States)] [and others

1995-03-08

126

Theory of shock wave propagation during laser ablation  

Microsoft Academic Search

Laser ablation consists of three coupled processes: (i) heat conduction within the solid, (ii) flow through a discontinuity layer (evaporation wave) attached to the solid surface, and (iii) shock wave expansion of the laser induced plume. In this paper, a one-dimensional solution for all three coupled processes is presented. The heat conduction and the evaporation wave are solved numerically. The

Zhaoyan Zhang; George Gogos

2004-01-01

127

Investigation of laser ablated plumes using fast photography  

Microsoft Academic Search

Fast photography is used to investigate the expansion dynamics of the laser ablated plasmas in various ambient atmospheres and laser energies. Dependence of plasma parameters such as velocity, temperature, density, and pressure on time and ambient atmosphere is presented. The measured vapor pressure and temperature decrease with the increase in ambient gas pressure. The images of the expanding plumes are

A. Misra; R. K. Thareja

1999-01-01

128

Growth of metal oxide nanoparticles using pulsed laser ablation technique  

Microsoft Academic Search

Nano particles exhibit physical and chemical properties distinctively different from that of bulk due to high number of surface atoms, surface energy and surface area to volume ratio. Laser is a unique source of radiation and has been applied in the synthesis of nano structured metal oxides. The pulsed laser ablation (PLA) technique in liquid medium has been proven an

M. A. Gondal; Q. A. Drmosh; Tawfik A. Saleh; Z. H. Yamani

2011-01-01

129

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

130

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

131

Femtosecond laser ablation of gallium arsenide investigated with time-of-flight mass spectroscopy  

E-print Network

Femtosecond laser ablation of gallium arsenide investigated with time- of-flight mass spectroscopy laser-induced ablation of gallium arsenide using time-of-flight mass spectroscopy. At the ablation into a collisional expansion process. Above the ablation threshold, the behavior of gallium particles can

von der Linde, D.

132

Toward laser ablation Accelerator Mass Spectrometry of actinides  

NASA Astrophysics Data System (ADS)

A project to measure neutron capture cross sections of a number of actinides in a reactor environment by Accelerator Mass Spectrometry (AMS) at the ATLAS facility of Argonne National Laboratory is underway. This project will require the precise and accurate measurement of produced actinide isotopes in many (>30) samples irradiated in the Advanced Test Reactor at Idaho National Laboratory with neutron fluxes having different energy distributions. The AMS technique at ATLAS is based on production of highly-charged positive ions in an electron cyclotron resonance (ECR) ion source followed by acceleration in the ATLAS linac and mass-to-charge (m/q) measurement at the focus of the Fragment Mass Analyzer. Laser ablation was selected as the method of feeding the actinide material into the ion source because we expect it will have higher efficiency and lower chamber contamination than either the oven or sputtering techniques, because of a much narrower angular distribution of emitted material. In addition, a new multi-sample holder/changer to allow quick change between samples and a computer-controlled routine allowing fast tuning of the accelerator for different beams, are being developed. An initial test run studying backgrounds, detector response, and accelerator scaling repeatability was conducted in December 2010. The project design, schedule, and results of the initial test run to study backgrounds are discussed.

Pardo, R. C.; Kondev, F. G.; Kondrashev, S.; Nair, C.; Palchan, T.; Scott, R.; Seweryniak, D.; Vondrasek, R.; Paul, M.; Collon, P.; Deibel, C.; Youinou, G.; Salvatores, M.; Palmotti, G.; Berg, J.; Fonnesbeck, J.; Imel, G.

2013-01-01

133

Nanoparticle plume dynamics in femtosecond laser ablation of gold  

NASA Astrophysics Data System (ADS)

This paper describes some recent results on femtosecond laser ablation of gold. We have studied both the fast vapour/plasma and slow nanoparticle plumes using Langmuir probe, time-resolved ICCD imaging and time-resolved optical absorption measurements. The nanoparticle plume dynamics was analysed by comparing the optical emission absorption measurements with an adiabatic isentropic model of ablation plume expansion, leading to an estimate of the amount of material in the nanoparticle plume.

O'Connell, G.; Donnelly, T.; Lunney, J. G.

2014-10-01

134

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

135

Nanoscale patterning of graphene through femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We report on nanometer-scale patterning of single layer graphene on SiO2/Si substrate through femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold of graphene. It is shown that, even though both SiO2 and Si have more absorption in the linear regime compared to graphene, the substrate can be kept intact during the process. This is achieved by scanning the sample under laser illumination at speeds yielding a few numbers of overlapping pulses at a certain point, thereby effectively shielding the substrate. By adjusting laser fluence and translation speed, 400 nm wide ablation channels could be achieved over 100 ?m length. Raster scanning of the sample yields well-ordered periodic structures, provided that sufficient gap is left between channels. Nanoscale patterning of graphene without substrate damage is verified with Scanning Electron Microscope and Raman studies.

Sahin, R.; Simsek, E.; Akturk, S.

2014-02-01

136

Ablative Laser Propulsion Using Multi-Layered Material Systems  

NASA Technical Reports Server (NTRS)

Experimental investigations are ongoing to study the force imparted to materials when subjected to laser ablation. When a laser pulse of sufficient energy density impacts a material, a small amount of the material is ablated. A torsion balance is used to measure the momentum produced by the ablation process. The balance consists of a thin metal wire with a rotating pendulum suspended in the middle. The wire is fixed at both ends. Recently, multi-layered material systems were investigated. These multi-layered materials were composed of a transparent front surface and opaque sub surface. The laser pulse penetrates the transparent outer surface with minimum photon loss and vaporizes the underlying opaque layer.

Nehls, Mary; Edwards, David; Gray, Perry; Schneider, T.

2002-01-01

137

Nanostructures synthesis by femtosecond laser ablation of glasses  

NASA Astrophysics Data System (ADS)

In this article, we investigate the variations in ablation dynamics that result in diverse nanostructures on SiO2 based glass samples. A three-dimensional fibrous nanoparticle agglomerate was observed on sodalime glass when exposed to femtosecond laser irradiation. The fused nanoparticles have diameters ranging from 30 nm to 70 nm. Long continuous nanofibers of extremely high aspect ratio (certain fibers up to 100 000:1) were obtained by exposing silica glass surface to femtosecond laser irradiation at MHz repetition rate in air. A nanostructure assembly comprising of nanofiber and nanoparticle agglomerates was also observed by ablating silica glass. From our experimental analysis, it was determined that variation in bandgap and material composition alters ablation dynamics and dictates the response of glass to femtosecond laser irradiation, ultimately leading to the formation of structures with varying morphology on silica and sodalime glass. The possible underlying mechanisms that produce such nanostructures on glass specimens have also been explored.

Vipparty, D.; Tan, B.; Venkatakrishnan, K.

2012-10-01

138

Laser ablation behaviors of SiC–ZrC coated carbon\\/carbon composites  

Microsoft Academic Search

Laser ablation behaviors of carbon\\/carbon composites with an underlying SiC layer and a surface ZrC layer were investigated using a continuous wave CO2 laser. The laser powers varied from 100W to 2000W. The results indicate that the two-layer SiC–ZrC coating can improve the laser ablation resistance of the carbon\\/carbon composites. Three ablation regions can be identified. The ablation mechanisms in

Qiaomu Liu; Litong Zhang; Fengrui Jiang; Jia Liu; Laifei Cheng; Hui Li; Yiguang Wang

2011-01-01

139

Comparison of the ablation plumes arising from ArF laser ablation of graphite, silicon, copper, and aluminum in vacuum  

NASA Astrophysics Data System (ADS)

The ablation plumes arising after irradiation of graphite, silicon, copper and aluminum with a pulsed nanosecond ArF (?=193 nm) laser at fluences between 2 and 20 J cm-2 in vacuum are studied and compared. The neutral and ionic components in the ablation plume have been measured via quadrupole mass spectrometry and ion probes, respectively. Additional information about the degree of ionization and the velocities of singly and multiply charged ions in the plume have been deduced via optical emission spectrometry, and the electron velocity distributions have been measured with Langmuir probes. Probing the plasma properties with this range of techniques is shown to provide a rather detailed picture of the ablation characteristics. The velocity distributions of the neutral atoms are comparatively narrow (˜1 km s-1 full width at half maximum) and peaked at a center of mass velocity of ˜3-4 km s-1. Their general form is reminiscent of those of species expanding supersonically from a pulsed nozzle. The electron and ion velocity distributions are much broader, and centered at much higher velocities (and kinetic energies). The relative ion yield, and the overall degree of ionization, both increase with increasing fluence and scale inversely with the ionization potentials of the respective target materials. Both charged components are found to be accelerating at short distances from the target. Such effects have been rationalized by assuming that incident laser radiation ionizes (by multiphoton ionization) neutral species ablated from the target surface, and that these ions and electrons then act as "seeds" for subsequent plume heating, ionization and plasma formation by inverse bremsstrahlung. This absorption due to inverse bremsstrahlung ensures the incident laser intensity is highest at the outer edge of the expanding plume. The outer region thus receives preferential excitation and heating—traditionally pictured in terms of the so-called two electron temperature model. Some of the resulting "hot" electrons escape from this coronal region, leading to an overall charge imbalance within the plasma, which manifests itself as an acceleration (driven by Coulombic interactions) of the charged components within the plume.

Claeyssens, Frederik; Henley, Simon J.; Ashfold, Michael N. R.

2003-08-01

140

Below-Band-Gap Laser Ablation Of Diamond For TEM  

NASA Technical Reports Server (NTRS)

Thin, electron-transparent layers of diamond for examination in transmission electron microscope (TEM) fabricated from thicker diamond substrates by using laser beam to ablate surface of substrate. Involves use of photon energy below band gap. Growing interest in use of diamond as bulk substrate and as coating material in variety of applications has given rise to increasing need for TEM for characterization of diamond-based materials. Below-band-gap laser ablation method helps to satisfy this need. Also applied in general to cutting and etching of diamonds.

George, Thomas; Foote, Marc C.; Vasquez, Richard P.; Fortier, Edward P.; Posthill, John B.

1995-01-01

141

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

142

Pulsed laser ablation of solids and critical phenomena  

NASA Astrophysics Data System (ADS)

We consider the possible manifestations of critical phenomena under pulsed laser ablation (PLA). The mechanism of phase explosion under nanosecond laser ablation is considered and the possibility of estimating the critical temperature from PLA experiments is discussed. A model based on the Euler equations and generalized van der Waals equation is developed to describe rarefaction shock waves (RSW) in near-critical matter. For a near-surface slab of a gold target heated above the critical point and expanding freely in vacuum, the evolution of the RSW has been studied. The possibility of RSW formation in stellar matter is discussed.

Bulgakova, Nadezhda M.; Bulgakov, Alexander V.; Bourakov, Igor M.; Bulgakova, Natalia A.

2002-09-01

143

Pyrolysis and laser ablation of plasma-polymerized fluorocarbon films: Effects of gold particles  

NASA Astrophysics Data System (ADS)

Plasma-polymerized fluorocarbon (PPFC) films were analyzed by thermogravimetric analysis (TGA), direct pyrolysis/mass spectrometry, and laser-ablation/electron-impact mass spectrometry. Fourier transform mass spectrometry was used to detect products. The films were made by plasma polymerizing tetrafluoroethylene in an argon plasma. Two types of films were studied: with and without fine gold particles incorporated in the PPFC films. TGA showed that gold-containing films decompose more rapidly and at lower temperature with increasing gold content. Pyrolysis products were determined as a function of temperature. The predominant positive product ions, using 20 eV electron-impact ionization, were C2F4+, CF3+ and a distribution of higher-mass unsaturated fluorocarbon species, CnFm+, up to at least n=14 and m?n+1. The predominant negative ions, formed by electron attachment, were also unsaturated fluorocarbon ions which extended up to 1145 u in mass. These species are different from those observed from polytetrafluoroethylene pyrolysis. No dependence of the positive-ion mass spectral distributions of pyrolysis products on gold content of the films was observed. However, the negative-ion pyrograms had a dramatically different temperature dependence for films with and without gold. The results imply that the gold-containing films have regions of lower molecular weight, and a possible formation mechanism is suggested. Laser ablation formed low-mass neutral fluorocarbon species. Ablation of the gold-containing film under direct laser ionization conditions (higher laser power), produced a spectrum resembling the pyrolysis spectrum, suggesting that the gold particles affect the mechanism of the ablation.

Creasy, William R.; Zimmerman, Jeffrey A.; Jacob, Wolfgang; Kay, Eric

1992-09-01

144

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

145

Thermal melting and ablation of silicon by femtosecond laser radiation  

SciTech Connect

The space-time dynamics of thermal melting, subsurface cavitation, spallative ablation, and fragmentation ablation of the silicon surface excited by single IR femtosecond laser pulses is studied by timeresolved optical reflection microscopy. This dynamics is revealed by monitoring picosecond and (sub)nanosecond oscillations of probe pulse reflection, which is modulated by picosecond acoustic reverberations in the dynamically growing surface melt subjected to ablation and having another acoustic impedance, and by optical interference between the probe pulse replicas reflected by the spalled layer surface and the layer retained on the target surface. The acoustic reverberation periods change during the growth and ablation of the surface melt film, which makes it possible to quantitatively estimate the contributions of these processes to the thermal dynamics of the material surface. The results on the thermal dynamics of laser excitation are supported by dynamic measurements of the ablation parameters using noncontact ultrasonic diagnostics, scanning electron microscopy, atomic force microscopy, and optical interference microscopy of the modified regions appearing on the silicon surface after ablation.

Ionin, A. A.; Kudryashov, S. I., E-mail: sikudr@lebedev.ru; Seleznev, L. V.; Sinitsyn, D. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)] [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Bunkin, A. F.; Lednev, V. N.; Pershin, S. M. [Russian Academy of Sciences, General Physics Institute (Russian Federation)] [Russian Academy of Sciences, General Physics Institute (Russian Federation)

2013-03-15

146

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

147

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

148

Laser ablation of liquid surface in air induced by laser irradiation through liquid medium  

Microsoft Academic Search

The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally\\u000a investigated. A supersonic liquid jet is observed at the liquid–air interface. The liquid surface layer is driven by a plasma\\u000a plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only

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

2010-01-01

149

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

150

Synthesis efficiency of heavy carbon clusters from ETFE ablated by different numbers of laser pulse in vacuum  

Microsoft Academic Search

We have carried out mass spectral analysis of positive ions produced by laser ablation of a copolymer of ethylene and tetrafluoroethylene (ETFE: [?CH2?CH2?CF2?CF2?]n) in vacuum using time-of-flight mass spectrometry (TOF-MS). The surfaces of the ETFE targets irradiated by different numbers of laser pulse were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Heavy carbon cluster ions Cn+

K. Shibagaki; N. Takada; K. Sasaki; K. Kadota

2002-01-01

151

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

152

Manufacture of microfluidic glass chips by deep plasma etching, femtosecond laser ablation, and anodic bonding  

Microsoft Academic Search

Two dry subtractive techniques for the fabrication of microchannels in borosilicate glass were investigated, plasma etching\\u000a and laser ablation. Inductively coupled plasma reactive ion etching was carried out in a fluorine plasma (C4F8\\/O2) using an electroplated Ni mask. Depth up to 100 ?m with a profile angle of 83°–88° and a smooth bottom of the etched structure\\u000a (Ra below 3 nm) were

S. Queste; R. Salut; S. Clatot; J.-Y. Rauch; Chantal G. Khan Malek

2010-01-01

153

Ablation scaling in laser-produced plasmas with laser intensity, laser wavelength, and target atomic number  

NASA Astrophysics Data System (ADS)

Layered target experiments at 1.06 ?m have been performed in order to measure the mass-ablation rate ? and the ablation pressure Pa as a function of absorbed laser intensity Ia, laser wavelength ?L, and target atomic number Z in steady-state ablation dominated by nonlocalized inverse bremsstrahlung absorption. The results can be expressed as ?exp(kg/ sec cm2)?65 [Ia(W/cm2)/1013]5/9 ?-4/9L(?m)Z1/4 and Pa(Mbar)?2.5[Ia(W/ cm 2)/ 1013]7/9 ?-2/9L(?m)Z1/8. The measured results show good agreement with theory for nonlocalized absorption and with data of others.

Dahmani, Faiz

1992-06-01

154

Laser ablation in a liquid-confined environment using a nanosecond laser pulse  

SciTech Connect

Laser ablation of aluminum metal with 1 ns, 800 nm pulse at low radiant exposures was investigated in air (dry) and water (wet) environments. Compared to dry ablation, an approximately eight times increase in material removal rate was associated with wet ablation. Based on optical reflectance and scanning electron microscope images, bubble formation/collapse was responsible for augmented acoustic pressure and ablation performance. Numerically simulated temperature distributions during wet ablation were consistent with the occurrence of explosive water vaporization near the critical temperature of water. Strong pressure emission during liquid vaporization and jet formation can account for enhanced ablation process. Radial expansion of bubbles minimized the redeposition of debris, leading to improvements in energy coupling to the target and ablation performance.

Kang, Hyun Wook [American Medical Systems, Minnetonka, Minnesota 55343 (United States); Lee, Ho [School of Mechanical Engineering, Kyungpook National University, Dae-gu 702-701 (Korea, Republic of); Welch, Ashley J. [Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States)

2008-04-15

155

Laser induced modification and ablation of InAs nanowires  

SciTech Connect

InAs nanowires were irradiated locally under an ambient condition using a focused laser beam, which led to laser ablation and thinning of the nanowires. We show that the laser beam can induce a reduction of the local As concentration in an InAs nanowire; the change leads to a significant decrease of local melting temperature of InAs, which results in the thinning and eventually breaking of the nanowire. The results indicate that chemical and mechanical modifications of an InAs nanowire can be accomplished by using a confocal laser beam, which may prove to be a convenient approach in fabricating nanostructural materials and nanodevices.

He Jiayu; Chen Pingping; Lu Wei; Dai Ning [Shanghai Institute of Technical Physics, Academy Science of China, Shanghai (China); Zhu Daming [Department of Physics, University of Missouri - Kansas City, Kansas City, Missouri 64110 (United States)

2012-05-01

156

Laser ablation and selective excitation directed to trace element analysis  

Microsoft Academic Search

A trace (element) analyser based on laser ablation and selectively excited radiation is proposed as an ultramicro-ultratrace technique for quantitative element analysis. Measurements of trace quantities of chromium in samples of NBS standard reference material (steel), doped skim milk powder and doped flour were undertaken. There is a linear 45 deg slope for Log\\/Log plot dependence of signal versus concentration

V. H. S. Kwong

1980-01-01

157

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

158

Mechanical properties of calcium phosphate coatings deposited by laser ablation  

Microsoft Academic Search

Amorphous calcium phosphate and crystalline hydroxyapatite coatings with different morphologies were deposited onto Ti–6Al–4V substrates by means of the laser ablation technique. The strength of adhesion of the coatings to the substrate and their mode of fracture were evaluated through the scratch test technique and scanning electron microscopy. The effect of wet immersion on the adhesion was also assessed. The

L Clèries; E Mart??nez; J. M Fernández-Pradas; G Sardin; J Esteve; J. L Morenza

2000-01-01

159

Elemental fractionation in laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

The major challenge to the use of laser ablation sample introduction, combined with inductively coupled plasma mass spectrometry, is the problem of calibration. In the geological analysis of minerals, calibration is complicated by the extraordinarily wide variety of sample matrices which may be encountered. While there is a lack of mineral standards with well characterized concentrations near 1 g\\/g, the NIST

H. P. Longerich; D. Günther; S. E. Jackson

1996-01-01

160

Deposition of fibrous nanostructure by ultrafast laser ablation  

NASA Astrophysics Data System (ADS)

This research work demonstrated that laser-induced reverse transfer (LIRT) can be used for controllable site-specific deposition of fibrous nanostructure. The LIRT method makes it possible to generate and deposit the fibrous nanostructure of a wide variety of materials on a transparent acceptor in a single-step process at an ambient condition. The deposition of fibrous nanostructures was conducted using ultrafast laser ablation of silicon and aluminum targets placed behind a glass acceptor. Femtosecond laser pulses pass through the transparent acceptor and hit the bulk donor. Consequently a mass quantity of nanoparticles ablates from the donor and then aggregates and forms a porous fibrous nanostructure on the transparent acceptor. Our experiments demonstrated that the gap between the target and the glass acceptor was critical in the formation and accumulation of nanofibers and it determines the density of the formed nanostructure. The formation mechanism of the nanostructures can be explained by the well-established theory of vapor condensation within the plume induced by ultrafast laser ablation. Experimental results also show that the length of the nanostructure can be controlled by the gap between the target and glass acceptor. Lastly, energy-dispersive x-ray spectroscopy (EDS) analysis shows the oxygen concentration in the nanofibrous structure which is associated with oxidation of ablated material at ambient atmosphere.

Tavangar, Amirhossein; Tan, Bo; Venkatakrishnan, K.

2010-05-01

161

Fractal Character of Titania Nanoparticles Formed by Laser Ablation  

SciTech Connect

Titania nanoparticles were fabricated by laser ablation of polycrystalline rutile in water at room temperature. The resulting nanoparticles were analyzed with x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electron micrograph image of deposited nanoparticles demonstrates fractal properties.

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

2009-01-01

162

Magnetically Guided Laser Ablation for High Specific Impulse Thrusters  

Microsoft Academic Search

Laser ablation has long been recognized as a method of obtaining very high temperature plasmas which can form a basis for ultra high specific impulse thrust devices. In the current work, research efforts were directed to explore the use of magnetic field with a strength of up to 4.5 Tesla to direct a laser (1064 nm YAG, 200-450 mJ\\/pulse) generated

S. H. Zaidi; T. W. Smith; R. Murray; L. Qian; R. B. Miles; K. Kremeyer

163

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

2008-02-01

164

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

NASA Astrophysics Data System (ADS)

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 differs by more than a factor of 4—the values of the ablation threshold energy Eabl normalized to the cohesion energy, ?abl=Eabl/Ecoh , are surprisingly universal: all are near 0.3 with ±30% scattering. The difference in the ratio Tc/Ttr means that for metals the melting threshold ?m is low, ?m?abl . This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in ?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.; Inogamov, Nail A.; Rethfeld, Bärbel; Urbassek, Herbert M.

2008-07-01

165

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

166

Laser ion source for Columbia Universitys microbeam A.W. Bigelow a,*, G. Randers-Pehrson a  

E-print Network

Laser ion source for Columbia UniversityÃ?s microbeam A.W. Bigelow a,*, G. Randers-Pehrson a , R High School, NY, USA Available online 29 August 2005 Abstract A laser ion source that will be installed for irradiation experiments with mammalian cells. Through laser ablation the laser ion source can produce heavy

Brenner, David Jonathan

167

Recent advances in laser ablation modelling for asteroid deflection methods  

NASA Astrophysics Data System (ADS)

Over the past few years, a series of studies have demonstrated the theoretical benefits of using laser ablation in order to mitigate the threat of a potential asteroid on a collision course with earth. Compared to other slow-push mitigation strategies, laser ablation allows for a significant reduction in fuel consumption since the ablated material is used as propellant. A precise modelling of the ablation process is however difficult due to the high variability in the physical parameters encountered among the different asteroids as well as the scarcity of experimental studies available in the literature. In this paper, we derive a new thermal model to simulate the efficiency of a laser-based detector. The useful material properties are first derived from thermochemical tables and equilibrium thermodynamic considerations. These properties are then injected in a 3D axisymetrical thermal model developed in Matlab. A temperature-dependent conduction flux is imposed on the exterior boundary condition that takes into account the balance between the incident power and the power losses due to the vaporization process across the Knudsen layer and the radiations respectively. A non-linear solver is finally used and the solution integrated over the ablation front to reconstruct the net thrust and the global mass flow. Compared to an initial 1D model, this new approach shows the importance of the parietal radiation losses in the case of a CW laser. Despite the low energy conversion efficiency, this new model still demonstrates the theoretical benefit of using lasers over more conventional low-thrust strategies.

Thiry, Nicolas; Vasile, Massimiliano

2014-09-01

168

A review of Thulium fiber laser ablation of kidney stones  

NASA Astrophysics Data System (ADS)

The clinical solid-state Holmium:YAG laser lithotripter (?=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 (?=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 for Ho:YAG and TFL. Laser lithotripsy complications also include optical fiber bending failure resulting in endoscope damage and low irrigation rates leading to poor visibility. Both problems are related to fiber diameter and limited by Ho:YAG laser multimode spatial beam profile. This study exploits TFL spatial beam profile for higher power transmission through smaller fibers. A short taper is also studied for expanding TFL beam at the distal tip of a small-core fiber. Stone mass loss, stone crater depths, fiber transmission losses, fiber burn-back, irrigation rates, and deflection through a flexible ureteroscope were measured for tapered fiber and compared with conventional fibers. The stone ablation threshold for TFL was four times lower than for Ho:YAG. Stone retropulsion with Ho:YAG increased linearly with pulse energy. Retropulsion with TFL was minimal at pulse rates < 150 Hz, then rapidly increased at higher pulse rates. TFL beam profile provides higher laser power through smaller fibers than Ho:YAG laser, potentially reducing fiber failure and endoscope damage and allowing greater irrigation rates for improved visibility and safety. Use of a short tapered distal fiber tip also allows expansion of the laser beam, resulting in decreased fiber tip damage compared to conventional fibers, without compromising fiber bending, stone ablation efficiency, or irrigation rates.

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

2011-02-01

169

Progress of laser ablation for accelerator mass spectroscopy at ATLAS utilizing an ECRISa)  

NASA Astrophysics Data System (ADS)

Beams of ions from the laser ablation method of solid materials into an electron cyclotron resonance ion source (ECRIS) plasma have been used for the first time in experiments at ATLAS. Initial accelerator mass spectroscopy experiments using laser ablation for actinides and samarium have been performed. Initial results of coupling the laser system to the ECR source have guided us in making a number of changes to the original design. The point of laser impact has been moved off axis from the center of the ECR injection side. Motor control of the laser positioning mirror has been replaced with a faster and more reliable piezo-electric system, and different raster scan patterns have been tested. The use of the laser system in conjunction with a multi-sample changer has been implemented. Two major problems that are being confronted at this time are beam stability and total beam intensity. The status of the development will be presented and ideas for further improvements will be discussed.

Scott, R.; Palchan, T.; Pardo, R.; Vondrasek, R.; Kondev, F.; Nusair, O.; Peters, C.; Paul, M.; Bauder, W.; Collon, P.

2014-02-01

170

Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments  

SciTech Connect

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-CO{sub 2} 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. [Instituto Tecnologico de Aeronautica 12.228-900-Sao Jose dos Campos (Brazil); Rodrigues, N. A. S.; Minucci, M. A. S. [Instituto de Estudos Avancados 12.228-001-Sao Jose dos Campos (Brazil)

2008-04-28

171

Comparative shock wave analysis during corneal ablation with an excimer laser, picosecond laser, and femtosecond laser  

NASA Astrophysics Data System (ADS)

With the event of topographic steep central islands following excimer laser surgery and the potential damage to the corneal endothelium, shock waves are playing an increasingly important role in laser refractive surgery. With this in mind, we performed a comparative shock wave analysis in corneal tissue using an excimer laser, picosecond laser, and femtosecond laser. We used a Lambda Physik excimer laser at 308 nm wavelength, a Nd:YLF picosecond laser at 1053 nm wavelength and a synchronously pumped linear cavity femtosecond laser at 630 nm wavelength. The pulse widths of the corresponding lasers were 8 ns, 18 ps, 150 fs, respectively. The energy density of irradiation was 2.5 to 8 times the threshold level being 2 J/cm2 (excimer laser), 86 J/cm2 (picosecond laser) and 10.3 J/cm2 (femtosecond laser). Shock wave dynamics were analyzed using time-resolved photography on a nanosecond time scale using the picosecond laser in corneal tissue, water and air. Shock wave dynamics using the femtosecond laser were studied in water only while the excimer laser induced shock wave during corneal ablation was studied in air only. We found the dynamics of shock waves to be similar in water and corneal tissue indicating that water is a good model to investigate shock wave effects in the cornea. The magnitude of the shock wave velocity and pressure decays over time to that of a sound wave. The distance over which it decays is 3 mm in air with the excimer laser and 600 - 700 micrometers in air with the picosecond laser. In water, the picosecond laser shock wave decays over a distance of 150 micrometers compared to the femtosecond laser shock wave which decays over a distance of 30 micrometers . Overall the excimer laser shock wave propagates 5 times further than that of the picosecond laser and the picosecond laser shock wave propagates 5 times further than that of the femtosecond laser. In this preliminary comparison, the time and distance for shock wave decay appears to be directly related to the laser pulse duration. The decay distance of the excimer laser shock waves appear to be 5 times longer than that of the picosecond laser in air while the picosecond laser shock wave distance appears to be 5 times longer than that of the femtosecond laser in water. The shorter shock wave distance of the picosecond laser is advantageous for corneal surgery by minimizing potential acoustic damage to the stromal and endothelial cells. Femtosecond lasers further minimize acoustic damage and their use should be considered in future corneal laser procedures.

Krueger, Ronald R.; Juhasz, Tibor

1995-05-01

172

Laser ablation of silicon in water with nanosecond and femtosecond pulses  

Microsoft Academic Search

We describe laser ablation of Si under water by 5 ns, 355 nm and 100 fs, 800 nm pulses. Compared to that in air, an approximately twofold improvement in the ablation rate is found in water for femtosecond and nanosecond pulses. For higher laser irradiances, the plasma that forms at the water-air interface hampers further improvement of the ablation rate.

Jun Ren; Michael Kelly; Lambertus Hesselink

2005-01-01

173

Next generation Er:YAG fractional ablative laser  

NASA Astrophysics Data System (ADS)

Pantec Biosolutions AG presents a portable fractional ablative laser system based on a miniaturized diode pumped Er:YAG laser. The system can operate at repetition rates up to 500 Hz and has an incorporated beam deflection unit. It is smaller, lighter and cost efficient compared to systems based on lamp pumped Er:YAG lasers and incorporates a skin layer detection to guarantee precise control of the microporation process. The pulse parameters enable a variety of applications in dermatology and in general medicine, as demonstrated by first results on transdermal drug delivery of FSH (follicle stimulating hormone).

Heinrich, A.; Vizhanyo, A.; Krammer, P.; Summer, S.; Gross, S.; Bragagna, T.; Böhler, C.

2011-03-01

174

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

175

Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes  

NASA Technical Reports Server (NTRS)

Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT.

Greendyke, R. B.; Creel, J. R.; Payne, B. T.; Scott, C. D.

2005-01-01

176

Effects of Two-Pulse Sequencing on Characteristics of Elementary Propellants for Ablative Laser Propulsion  

NASA Technical Reports Server (NTRS)

This work continues on previous investigations of elementary propellants for Ablative Laser Propulsion (ALP). This paper details the experimental methods used for alignment of a non-colinear temporal pulse splitting apparatus. Spatial coincidence of the separate pulses is established, the pulses are delayed, and first data is reported on this pulse spacing effect on time-of-fight (TOF) measurements. This includes ion velocity and number density measurements, and this data is compared to results from a previous work. Also, first data on the experimental determination of the time required for the laser-induced plasma to become purely reflective to incident pulses is presented.

Thompson, M. Shane; Pakhomov, Andrew V.; Herren, Kenneth A.

2003-01-01

177

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

178

Quantitative images of metals in plant tissues measured by laser ablation inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of toxic and essential elements in thin sections (thickness of 30 or 40 ?m) of tobacco plant tissues. Two-dimensional images of Mg, Fe, Mn, Zn, Cu, Cd, Rh, Pt and Pb in leaves, shoots and roots of tobacco were produced. Sections of the plant tissues (fixed onto glass slides) were scanned by a focused beam of a Nd:YAG laser in a laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a quadrupole ICP-MS instrument. Ion intensities of the investigated elements were measured together with 13C +, 33S + and 34S + within the entire plant tissue section. Matrix matching standards (prepared using powder of dried tobacco leaves) were used to constitute calibration curves, whereas the regression coefficient of the attained calibration curves was typically 0.99. The variability of LA-ICP-MS process, sample heterogeneity and water content in the sample were corrected by using 13C + as internal standard. Quantitative imaging of the selected elements revealed their inhomogeneous distribution in leaves, shoots and roots.

Becker, J. S.; Dietrich, R. C.; Matusch, A.; Pozebon, D.; Dressler, V. L.

2008-11-01

179

Two-Pulsed Technique for Ablative Laser Propulsion: Force Measurement in Vacuum  

NASA Technical Reports Server (NTRS)

This is a continuation of studies using a two-pulsed technique for Ablative Laser Propulsion (ALP) extended to force measurements in vacuum. Aluminum samples were ablated using pairs of laser pulses, each of 100 ps width, 532 nm wavelength and 5 mJ energy. The pulses were temporally separated in the 0 - 0.67 ns range. The force imparted on Al targets was measured in situ by means of a piezoelectric force gauge. The preliminary results confirm the previously reported oscillatory behavior of ion velocity and number density observed by means of a time-of-flight energy analyzer. The uncertainties of presented measurements and future directions for the study are discussed.

Herren, Kenneth A.; Cohen, Timothy; Lin, Jun; Pakhomov, Andrew V.

2004-01-01

180

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 P S

2014-01-01

181

Detection and Classification of Individual Airborne Microparticles using Laser Ablation Mass Spectroscopy and Multivariate Analysis  

SciTech Connect

We are developing a method for the real-time analysis of airborne microparticles based on laser ablation mass spectroscopy. Airborne particles enter an ion trap mass spectrometer through a differentially-pumped inlet, are detected by light scattered from two CW laser beams, and sampled by a 10 ns excimer laser pulse at 308 nm as they pass through the center of the ion trap electrodes. After the laser pulse, the stored ions are separated by conventional ion trap methods. In this work thousands of positive and negative ion spectra were collected for eighteen different species: six bacteria, six pollen, and six particulate samples. The data were then averaged and analyzed using the Multivariate Patch Algorithm (MPA), a variant of traditional multivariate anal ysis. The MPA correctly identified all of the positive ion spectra and 17 of the 18 negative ion spectra. In addition, when the average positive and negative spectra were combined the MPA correctly identified all 18 species. Finally, the MPA is also able to identify the components of computer synthesized mixtures of the samples studied

Gieray, R.A.; Lazar, A.; Parker, E.P.; Ramsey, J. M.; Reilly, P.T.A.; Rosenthal, S.E.; Trahan, M.W.; Wagner, J.S.; Whitten, W.B.

1999-04-27

182

Pico- and nanosecond laser ablation of mixed tungsten / aluminium films  

E-print Network

In order to extend the investigation of laser-assisted cleaning of ITER-relevant first mirror materials to the picosecond regime, a commercial laser system delivering 10 picosecond pulses at 355 nm at a frequency of up to 1 MHz has been used to investigate the ablation of mixed aluminium (oxide) / tungsten (oxide) layers deposited on poly- and nanocrystalline molybdenum as well as nanocrystalline rhodium mirrors. Characterization before and after cleaning using scanning electron microscopy (SEM) and spectrophotometry shows heavy dust formation, resulting in a degradation of the reflectivity. Cleaning using a 5 nanosecond pulses at 350 and 532 nm, on the other hand, proved very promising. The structure of the film remnants suggests that in this case buckling was the underlying removal mechanism rather than ablation. Repeated coating and cleaning using nanosecond pulses is demonstrated.

Wisse, M; Steiner, R; Mathys, D; Stumpp, A; Joanny, M; Travere, J M; Meyer, E

2014-01-01

183

Pre-ignition laser ablation of nanocomposite energetic materials  

SciTech Connect

Laser ignition of energetic material composites was studied for initiation with heating rates from 9.5 Multiplication-Sign 10{sup 4} to 1.7 Multiplication-Sign 10{sup 7} K/s. This is a unique heating rate regime for laser ignition studies because most studies employ either continuous wave CO{sub 2} lasers to provide thermal ignition or pulsed Nd:YAG lasers to provide shock ignition. In this study, aluminum (Al) and molybdenum trioxide (MoO{sub 3}) nanoparticle powders were pressed into consolidated pellets and ignited using a Nd:YAG laser (1064 nm wavelength) with varied pulse energy. Results show reduced ignition delay times corresponding to laser powers at the ablation threshold for the sample. Heating rate and absorption coefficient were determined from an axisymmetric heat transfer model. The model estimates absorption coefficients from 0.1 to 0.15 for consolidated pellets of Al + MoO{sub 3} at 1064 nm wavelength. Ablation resulted from fracturing caused by a rapid increase in thermal stress and slowed ignition of the pellet.

Stacy, S. C.; Massad, R. A.; Pantoya, M. L. [Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)] [Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

2013-06-07

184

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

NASA Astrophysics Data System (ADS)

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+* ions and C2* 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 (PAr) , 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 PAr 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 PAr 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.

2005-11-01

185

Dynamics of multiple plumes in laser ablation: Modeling of the shielding effect  

NASA Astrophysics Data System (ADS)

The scattering and absorption of laser radiation by previously ablated plumes in laser ablation (known as the shielding effect) dramatically affect the efficiency of laser ablation process. The ablated plumes consisting of water vapor, droplets, and particles are modeled as a gas-particle equilibrium mixture by solution of the Euler equations combined with the transport equation for the ratio of heat capacities. Shielding effect on the overall ablated mass by multiple plumes is studied for a wide range of concentration of particles in vaporized plumes, various laser repetition rates, scattering, and absorption of laser energy. The shielding phenomenon is studied for short sequences of discrete plumes to focus on the shielding effect of individual plumes. The results of numerical modeling were compared to experimental results of laser-induced water explosive vaporization. Ablation rate was calculated for a single ablated plume and for the sequence of six laser pulses at the repetition rates of 0.33 and 1MHz at which gas dynamics interactions between plumes are strong but plumes have not yet form a continuous jet. A single ablated plume has an initial semispherical shape which transforms into mushroomlike cloud with a thin stem and a ring vortex as it was observed in experiments with water and cornea ablation. For the plume with a given ablated mass, the longer ejection of plume with smaller density produces the plume with smaller shielding capacity. For multiple laser pulses, the velocity of ejected mixture increases from the center of the target to its periphery because of the shielding effect. The ablated mass of the current plume depends on the attenuation of the incident laser beam energy caused by the propagation of laser beam through previously ablated plumes. In the case of laser energy absorption, the ablation rate per pulse exceeds 2-2.5 times the rate obtained for the laser energy scattering.

Zinovik, Igor; Povitsky, Alex

2006-07-01

186

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

187

Modeling of laser ablation and fragmentation of human calculi  

SciTech Connect

The large-scale radiation-hydrodynamics computer code LASNEX, has been used to model experimental results in the laser ablation and fragmentation of renal and biliary calculi. Recent experiments have demonstrated laser ablation and fragmentation of human calculi in vitro and in vivo. In the interaction, laser light incident upon the calculus is of sufficient intensity to produce a plasma (a hot ionized gas). The physical picture which emerges is as follows. The plasma couples to acoustic and shear waves which then propagate through the dense stone material, causing spall and fracture by reflection from material discontinuities or boundaries. Experiments have thus far yielded data on the interaction against which models can be tested. Data on the following have been published: (1) light emission, (2) absorption and emission spectra, (3) fragmentation efficiency, (4) cavitation bubble dynamics and (5) mass removal. We have performed one dimensional simulations of the laser-matter interaction to elucidate the important physical mechanisms. We find that good quantitative fits between simulation and experiment are obtained for visible light emission, electron temperature, electron density, plasma pressure and cavitation bubble growth. With regard to mass removal, experiment and simulation are consistent with each other and give an excellent estimate of the ablation threshold. The modeling indicates that a very small ablation layer at the surface of the calculus is responsible for significant mass loss by fragmentation within the bulk of the calculus. With such quantitative fits in hand, we believe this type of modeling can now be applied to the study of other procedures involving plasma formation of interest to the medical community. 25 refs., 7 figs.

Gitomer, S.; Jones, R.D.; Howsare, C.

1989-01-01

188

Growth of epitaxial thin films by pulsed laser ablation  

SciTech Connect

High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

Lowndes, D.H.

1992-01-01

189

Growth of epitaxial thin films by pulsed laser ablation  

SciTech Connect

High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

Lowndes, D.H.

1992-10-01

190

Optical feedback signal for ultrashort laser pulse ablation of tissue  

SciTech Connect

An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

1997-07-01

191

Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Principles and Applications  

Microsoft Academic Search

The application of laser ablation inductively plasma mass spectrometry (LA?ICP?MS) to the determination of major, minor, and trace elements as well as isotope?ratio measurements offers superior technology for direct solid sampling in analytical chemistry. The advantages of LA?ICP?MS include direct analysis of solids; no chemical dissolution is necessary, reduced risk of contamination, analysis of small sample mass, and determination of

N. S. Mokgalaka; J. Gardea-Torresdey

2006-01-01

192

Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers  

SciTech Connect

Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.

Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J.; Herman, S.; Lane, S.M.; London, R.A.; Matthews, D.L.; Perry, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Chang, T.D. [Veterans Administration Hospital, Martinez, CA (United States); Neev, J. [Beckman Laser Inst. and Medical Clinic, Irvine, CA (United States)

1996-05-01

193

Proton emission from a laser ion source.  

PubMed

At intensities of the order of 10(10) W?cm(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. PMID:22380289

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

2012-02-01

194

Trapping ions with lasers  

E-print Network

This work theoretically addresses the trapping an ionized atom with a single valence electron by means of lasers, analyzing qualitatively and quantitatively the consequences of the net charge of the particle. In our model, the coupling between the ion and the electromagnetic field includes the charge monopole and the internal dipole, within a multipolar expansion of the interaction Hamiltonian. Specifically, we perform a Power-Zienau-Woolley transformation, taking into account the motion of the center of mass. The net charge produces a correction in the atomic dipole which is of order $m_e/M$ with $m_e$ the electron mass and $M$ the total mass of the ion. With respect to neutral atoms, there is also an extra coupling to the laser field which can be approximated by that of the monopole located at the position of the center of mass. These additional effects, however, are shown to be very small compared to the dominant dipolar trapping term.

Cecilia Cormick; Tobias Schaetz; Giovanna Morigi

2010-12-16

195

Trapping ions with lasers  

E-print Network

This work theoretically addresses the trapping an ionized atom with a single valence electron by means of lasers, analyzing qualitatively and quantitatively the consequences of the net charge of the particle. In our model, the coupling between the ion and the electromagnetic field includes the charge monopole and the internal dipole, within a multipolar expansion of the interaction Hamiltonian. Specifically, we perform a Power-Zienau-Woolley transformation, taking into account the motion of the center of mass. The net charge produces a correction in the atomic dipole which is of order $m_e/M$ with $m_e$ the electron mass and $M$ the total mass of the ion. With respect to neutral atoms, there is also an extra coupling to the laser field which can be approximated by that of the monopole located at the position of the center of mass. These additional effects, however, are shown to be very small compared to the dominant dipolar trapping term.

Cormick, Cecilia; Morigi, Giovanna

2010-01-01

196

Update On CO2 Laser Ablation Of Polyoxymethylene At 101 kPa  

NASA Astrophysics Data System (ADS)

Recent work has brought about a renewed interest in CO2 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 CO2 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 CO2 laser radiation. Fluences higher (and lower) than previously tested for CO2 laser ablation were studied herein, and record specific impulse values for CO2 laser ablation of flat polyoxymethylene are also reported here.

Sinko, John E.; Scharring, Stefan; Ogita, Naoya; Sasoh, Akihiro; Eckel, Hans-Albert; Röser, Hans-Peter

2010-10-01

197

Modeling of Plume Dynamics in Laser Ablation  

Microsoft Academic Search

The aim of this study is to find thermal conditions for the formation of carbon annotates in a laser furnace. The proposed model includes a multi-species formulation for concentration of chemical components combined with the compressible Euler equations. An axisymmetric unsteady computational gas dynamic model of plume expansion into ambiance has been developed. In the present work, the system of

Diomar Lobao; Alex Povitsky

2003-01-01

198

Laser-assisted ablation of corneal-like material using focused femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

In this article we investigate laser-assisted ablation of Hydroxy Ethyl Methacrylate (Hydro-gel) material using 30 femtosecond laser pulses delivered from a Ti:Sapphire multipass amplifier with a repetition rate of 1 kHz. Measurements of the crater depth, width and removed volume as a function of laser pulse energy and pulse number were made for stationary and translated ablation. Based on laser fluence, crater profile, collateral damage and translation speed, optimal laser parameters for efficient micromachining were defined. The results presented in this paper will be important for future developments in laser ophthalmology, where insight into the optimal laser parameters for corneallike surgery will decrease both processing time and collateral tissue damage.

Kohli, Vikram; Yu, Deli; Elezzabi, Abulhakem Y.

2007-02-01

199

Furnace geometry effects on plume dynamics in laser ablation for nanotube synthesis  

Microsoft Academic Search

Laser ablation (LA) has become a popular method for production of carbon nanotubes where formation of gaseous carbon plume and liberation of catalyst particles are caused by the laser pulse. The plume dynamics in laser ablation is somewhat similar to point explosion where a large amount of energy is liberated in a small volume. The aim of this study is

Diomar Cesar Lobão; Alex Povitsky

2004-01-01

200

Characteristics of Droplets Ejected from Liquid Propellants Ablated by Laser Pulses in Laser Plasma Propulsion  

NASA Astrophysics Data System (ADS)

The angular distribution and pressure force of droplets ejected from liquid water and glycerol ablated by nanosecond laser pulses are investigated under different viscosities in laser plasma propulsion. It is shown that with increasing viscosity, the distribution angles present a decrease tendency for two liquids, and the angular distribution of glycerol is smaller than that of water. A smaller distribution leads to a higher pressure force generation. The results indicate that ablation can be controlled by varying the viscosity of liquid propellant in laser plasma propulsion.

Zheng, Zhiyuan; Gao, Hua; Fan, Zhenjun; Xing, Jie

2014-03-01

201

Lasers in Surgery and Medicine 44:805814 (2012) Femtosecond Plasma Mediated Laser Ablation Has  

E-print Network

Medicine, Department of Surgery, Plastic and Reconstructive Surgery Division, Stanford University SchoolLasers in Surgery and Medicine 44:805­814 (2012) Femtosecond Plasma Mediated Laser Ablation Has post- surgery. However, at 8 weeks post-surgery, there was no significant difference. In the drill

Palanker, Daniel

202

Measurement of energy conversion efficiency during laser ablation by a multiple laser beam deflection probe  

Microsoft Academic Search

We have developed a novel multiple-pass laser beam deflection (LBD) arrangement for detection of acoustic and weak shock waves in fluids. The arrangement gives us the possibility to acquire temporally resolved information (signal waveforms) on single and non-reproducible events in several points of space. We have applied the new arrangement to investigate spherical shocks generated during laser ablation of metallic

Janez Diaci; Janez Možina

1996-01-01

203

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

204

Laser acceleration of ion beams  

E-print Network

We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.

I. A. Egorova; A. V. Filatov; A. V. Prozorkevich; S. A. Smolyansky; D. B. Blaschke; M. Chubaryan

2006-12-18

205

Laser ablation of hard tissue: correlation between the laser beam parameters and the post-ablative tissue characteristics  

NASA Astrophysics Data System (ADS)

Hard dental tissue laser applications, such as preventive treatment, laser diagnosis of caries, laser etching of enamel, laser decay removal and cavity preparation, and more recently use of the laser light to enlarge the root canal during the endodontic therapy, have been investigated for in vitro and in vivo applications. Post-ablative surface characteristics, e.g. degree of charring, cracks and other surface deformation, can be evaluated using scanning electron microscopy. The experimental data are discussed in relevance with the laser beam characteristics, e.g. pulse duration, beam profile, and the beam delivery systems employed. Techniques based on the laser illumination of the dental tissues and the subsequent evaluation of the scattered fluorescent light will be a valuable tool in early diagnosis of tooth diseases, as carious dentin or enamel. The laser induced autofluorescence signal of healthy dentin is much stronger than that of the carious dentin. However, a better understanding of the transmission patterns of laser light in teeth, for both diagnosis and therapy is needed, before the laser procedures can be used in a clinical environment.

Serafetinides, Alexandros A.; Makropoulou, Mersini I.; Khabbaz, Maruan

2003-11-01

206

Laser microprobe and resonant laser ablation for depth profile measurements of hydrogen isotope atoms contained in graphite  

Microsoft Academic Search

We measured the depth profile of hydrogen atoms in graphite by laser microprobing combined with resonant laser ablation. Deuterium-implanted graphite was employed for the measurements. The sample was ablated by a tunable laser with a wavelength corresponding to the resonant wavelength of1S-2S of deuterium with two-photon excitation. The ablated deuterium was ionized by a 2 + 1 resonant ionization process.

Masafumi Yorozu; Tatsuya Yanagida; Terunobu Nakajyo; Yasuhiro Okada; Akira Endo

2001-01-01

207

Nanoparticle preparation of quinacridone and ?-carotene using near-infrared laser ablation of their crystals  

NASA Astrophysics Data System (ADS)

Quinacridone nanoparticles with a mean size of about 200 nm are successfully prepared using nanosecond near-infrared (NIR) laser ablation of its microcrystalline powders in heavy water. The absorption spectra of the formed colloidal solutions depend on the excitation wavelengths, which is eventually ascribed to number and energy of absorbed photons. ?-carotene has low photostability and is easily decomposed upon UV/VIS laser ablation of its solid, while its nanoparticles are prepared utilizing this NIR laser ablation technique. The advantage of nanoparticle preparation by NIR laser ablation is discussed.

Yuyama, K.; Sugiyama, T.; Asahi, T.; Ryo, S.; Oh, I.; Masuhara, H.

2010-12-01

208

Synthesis of cation-exchanged laponite suspensions by laser ablation of microsized-metal particles in liquid  

NASA Astrophysics Data System (ADS)

Laser ablation in the liquid technique has been used to synthesize cation-exchanged laponite suspensions. In summary, laser ablation of the microsize-metal powder (Co, Al, and Cu) dispersed in an aqueous solution containing deionized water laponite crystals was carried out using laser beam generated by a single-mode, Q-switched Nd-Yag laser operating at 532 nm with a pulse duration of 5.5 ns and 10 Hz repetition rate. Laser fluence was 0.265 J/cm 2 for all tests. For all samples, the mass fraction of laponite was 1%. General observations of the prepared samples indicated that an aqueous suspension of 1 wt% laponite retained its free flowing liquid phase characteristics even after aging for several weeks. When bivalent cationic metals (Cu, Co, Al) were ablated in it for about 1 h, even with a small amount of the metal (0.025% and 0.050%) were generated, the suspension became highly viscous and behaved as a shear-thinning and thixotropic material. That is, the suspension gelled strongly when it was allowed to rest. The gels, however, could easily be reverted to a low viscosity liquid with simple shaking. Information from TEM and XRD analysis indicated that such a sol-gel transformation might be due to the charge exchange between the cationic species produced during the laser ablation and the sodium ions in the interlayers of the clay sheets.

Phuoc, Tran X.; Chen, Ruey-Hung

2011-03-01

209

Preparation of nanofluids using laser ablation in liquid technique  

SciTech Connect

In this work we report some results on thermal and transport properties of Ag-di water and Al-di water nanofluids that were prepared using Nd:yag laser to ablate Ag and Al in deionized water. The produced nanofluids were characterized using UV-VIS spectroscopy and TEM analysis. Our results on the UV-VIS spectra of the generated nanofluids demonstrated that using laser ablation in liquid we could generate stable colloids containing well-dispersed nanosized particles without use of any dispersants or surface reactive reagents. For Ag-di water nanofluids, the particles were spherical and the majority of the particles were in the 9 – 21 nm range with some big ones 23 - 26nm in size. The results on Al showed that the amplitude of the UV-VIS absorption spectra of Al-di water changed with time indicating that the ablated Al species reacts with water to yield an amorphous gel that transforms to the crystallized aluminum hydroxides with different shapes and sizes. The shapes were fibrous, triangular, rectangular, spherical shapes and joining of two pieces of triangles. In fact, these triangular and rectangular shapes were indeed pyramidal structures and hexagonal prisms, respectively.

Tran, P.X.; Soong, Yee

2007-06-01

210

Femtosecond pulsed laser ablation deposition of tantalum carbide  

NASA Astrophysics Data System (ADS)

In this work a frequency-doubled Nd:glass laser with a pulse duration of 250 fs has been used to ablate a TaC target and to deposit thin films on silicon. The results have been compared with those previously obtained by nanosecond pulsed laser deposition and evidence of large differences in the plasma characteristics has been revealed. In particular, in the femtosecond and nanosecond plumes the energy and the velocity of neutral and ionized particles are very different. The features of femtosecond ablation include the delayed emission from the target of large and slow particles. The characteristics of the femtosecond plasma are clearly related to the morphology and composition of the deposited films and the results show a nanostructure consisting of a large number of spherical particles, with a mean diameter of about 50 nm, with a stoichiometry corresponding to Ta 2C. To explain these features, an ablation-deposition mechanism, related to the ejection of hot particles from the target, is proposed.

Teghil, R.; De Bonis, A.; Galasso, A.; Villani, P.; Santagata, A.

2007-12-01

211

Ablation of selected conducting layers by fiber laser  

NASA Astrophysics Data System (ADS)

Laser Direct Writing (LDW) are used in the manufacture of electronic circuits, pads, and paths in sub millimeter scale. They can also be used in the sensors systems. Ablative laser writing in a thin functional layer of material deposited on the dielectric substrate is one of the LDW methods. Nowadays functional conductive layers are composed from graphene paint or nanosilver paint, indium tin oxide (ITO), AgHTTM and layers containing carbon nanotubes. Creating conducting structures in transparent layers (ITO, AgHT and carbon nanotubes layers) may have special importance e.g. for flexi electronics. The paper presents research on the fabrication of systems of paths and appropriate pattern systems of paths and selected electronic circuits in AgHTTM and ITO layers deposited on glass and polymer substrates. An influence of parameters of ablative fiber laser treatment in nanosecond regime as well as an influence of scanning mode of laser beam on the pattern fidelity and on electrical parameters of a generated circuit was investigated.

Pawlak, Ryszard; Tomczyk, Mariusz; Walczak, Maria

2014-08-01

212

Real-time measurement of ArF excimer laser corneal tissue ablation rates using cross-  

E-print Network

between several cross-correlation metrics and the directly measured corneal ablation rate, yieldingReal-time measurement of ArF excimer laser corneal tissue ablation rates using cross- correlation refractive surgery. © 2011 Optical Society of America OCIS codes: (170.1020) Ablation of tissue; (170

Hahn, David W.

213

Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma  

SciTech Connect

When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

Tong Huifeng; Yuan Hong [Institute of Fluid Physics, Chinese Academy of Engineering Physics, P.O. Box 919-101, Mianyang, Sichuan 621900 (China); Tang Zhiping [CAS Key Laboratory for Mechanical Behavior and Design of Materials, Department of Mechanics and Mechanical Engineering, University of Science and Technology of China, Hefei 230026 (China)

2013-01-28

214

Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma  

NASA Astrophysics Data System (ADS)

When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

Tong, Huifeng; Yuan, Hong; Tang, Zhiping

2013-01-01

215

Testing of concrete by laser ablation  

DOEpatents

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

216

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

217

Laser ablative synthesis of carbon nanotubes  

DOEpatents

An improved method for the production of single walled carbon nanotubes that utilizes an RF-induction heated side-pumped synthesis chamber for the production of such. Such a method, while capable of producing large volumes of carbon nanotubes, concurrently permits the use of a simplified apparatus that allows for greatly reduced heat up and cool down times and flexible flowpaths that can be readily modified for production efficiency optimization. The method of the present invention utilizes a free electron laser operating at high average and peak fluence to illuminate a rotating and translating graphite/catalyst target to obtain high yields of SWNTs without the use of a vacuum chamber.

Smith, Michael W. (Newport News, VA); Jordan, Kevin (Newport News, VA); Park, Cheol (Yorktown, VA)

2010-03-02

218

Ablation of Silicone Rubber Using UV-Nanosecond and IR-Femtosecond Lasers  

NASA Astrophysics Data System (ADS)

Silicone rubber was ablated by an ArF laser, the forth harmonics of Nd:YAG, and a Ti:sapphire laser for microdrilling. The fs-Ti:sapphire laser ablated the sample at a rate higher than those of the other lasers, in the fluence range of approximately 0.15-2.0 J/cm2. No chemical denaturation was observed after irradiation using each laser. The UV-ArF laser ablated the irradiated area precisely, making the surface flat and smooth.

Fukami, Yuko; Okoshi, Masayuki; Inoue, Narumi

2004-07-01

219

Effects of laser parameters on pulsed Er-YAG laser skin ablation  

Microsoft Academic Search

Previous studies demonstrated that pulsed 2.94m Er-YAG laser radiation allows a precise etching of organic tissue with only minimal thermal damage. This makes the Er-YAG laser a promising tool for the careful removal of superficial skin lesions. In order to provide optimized laser parameters for potential clinical use and to enhance our understanding of the mid-infrared ablation process, we measured

Raimund Hibst; Roland Kaufmann

1991-01-01

220

Ion Acceleration Characteristics of a Laser-Electrostatic Hybrid Microthruster  

NASA Astrophysics Data System (ADS)

A fundamental study on laser-electrostatic hybrid acceleration thruster was conducted, in which laser-induced plasmas were induced through laser beam irradiation on to a solid target and accelerated by an electrostatic field of an acceleration electrode. For thrust measurements, a calibrated torsion-balance type thrust-stand was developed and utilized. A time-of-flight measurement with a Faraday cup was also conducted for ion current and velocity measurements. It was found that an average speed of ions of a pure laser ablation was about 50 km/sec for 40 ?J/pulse with pulse width of 250 psec. Moreover, for acceleration voltage of Vaccl = + 300 V, T = 1.8 ?N, Isp = 3600 sec, and ?th = 52 % were achieved. It was shown that an acceleration electrode with positive potential was more effective than that with negative potential for positive-ion acceleration in the laser induced plasma, in which ions were induced with the Coulomb explosion.

Igari, Akira; Horisawa, Hideyuki; Kimura, Itsuro

2005-04-01

221

Nanosecond and femtosecond laser ablation of brass: Particulate and ICPMS measurements  

SciTech Connect

Femtosecond and nanosecond lasers were compared for ablating brass alloys. All operating parameters from both lasers were equal except for the pulse duration. The ablated aerosol vapor was collected on silicon substrates for particle size measurements or sent into an inductively coupled plasma mass spectrometer. The diameters and size distribution of particulates were measured from scanning electron microscope (SEM) images of the collected ablated aerosol. SEM measurements showed that particles ablated using nanosecond pulses were single spherical entities ranging in diameter from several micrometers to several hundred nanometers. Primary particles ablated using femtosecond ablation were {approx}100 nm in diameter but formed large agglomerates. ICPMS showed enhanced signal intensity and stability using femtosecond compared to nanosecond laser ablation.

Liu, C.; Mao, X.L.; Mao, S.; Zeng, X.; Greif, R.; Russo, R.E.

2003-11-01

222

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

223

Matrix effects in laser ablation molecular isotopic spectrometry  

NASA Astrophysics Data System (ADS)

Recently, it has been shown that laser-induced breakdown spectroscopy (LIBS) can be used for the detection of isotopes of elements via isotopic shifts in diatomic species in a technique known as laser ablation molecular isotopic spectrometry (LAMIS). While LAMIS works quite well for isotopic analysis of pure compounds under optimal conditions, it is desirable for it to be applicable for a variety of compounds and matrices. However, the LIBS plasma emission associated with LAMIS depends on several parameters, including the applied electric field of the laser pulse, the physical properties of the material being investigated, and the presence of additional elements other than the element of interest. In this paper, we address some of the pitfalls arising from these dependencies when using LAMIS for the determination of the relative isotopic abundance of boron-containing materials with varying chemical matrices.

Brown, Staci; Ford, Alan; Akpovo, Charlemagne C.; Martinez, Jorge; Johnson, Lewis

2014-11-01

224

Laser ablation of copper based alloys by single and double pulse laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Single and double pulse laser induced breakdown spectroscopy was applied to the analysis of copper based alloys samples, in order to investigate the material ablation process under two different experimental conditions. An Nd:YAG laser, emitting at the fundamental wavelength (1064 nm) for a fixed value of total energy with the same pulse width, has been used for both set-up configurations. Certified samples of copper based alloys were examined in order to investigate the effect of their different compositions on the ablation process efficiency. The craters produced by the laser on the samples surfaces were measured by a contact profilometer in order to evaluate the mass of ablated material. In this respect the differences in behaviour of the single and the double pulse ablation for Laser Induced Breakdown Spectroscopy (LIBS), respectively, have been considered. The dependence, under the same experimental conditions, of the LIBS background emission of the different ablated masses of the material has also been investigated, by looking for normalization algorithms for quantitative data reduction. The behaviour of some peculiar intensity ratios, suitable for building calibration curves, has been studied in order to evaluate the trend in fractionated evaporation on going from the single pulse to the double pulse technique.

Caneve, L.; Colao, F.; Fantoni, R.; Spizzichino, V.

2006-11-01

225

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

226

Physics of pulsed laser ablation at 248 nm: Plasma energetics and Lorentz interactions  

NASA Astrophysics Data System (ADS)

Pulsed KrF (248 nm) excimer laser ablation of targets can generate quasi-neutral ground state atomic particle plasmas with energies in the range of 200 -1100 eV. Onset of plasma formation occurs when optical intensities exceed 108 W/cm2. The expanding ensemble has a pronounced angular energy dependence, the highest energies peaked in the direction normal to the target. Correlation of the temporal nature of the laser pulse and the ensuing ion mass pulses suggest that transfer of energy is, indeed, a very rapid process -probably less than 5 ns. A wide range of elemental and several compound targets were studied to determine how ion energy distributions were influenced by atomic mass. The energetic plasma beams interact with magnetic fields as predicted from the Lorentz force. Results are consistent with an inverse bremsstrahlung and Lorentz force mechanism for particle acceleration.

Lynds, L.; Weinberger, B. R.

227

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

PubMed Central

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

2012-01-01

228

Characterization of the laser ablation plasma used for the deposition of amorphous carbon  

NASA Astrophysics Data System (ADS)

The plasma produced by laser ablation of a graphite target was studied by means of optical emission spectroscopy and a Langmuir planar probe. Laser ablation was performed using a Nd:YAG laser with emission at the fundamental line with pulse length of 28 ns. In this work, we report the behavior of the mean kinetic energy of plasma ions and the plasma density, as a function of the laser fluence (J/cm 2), and the target to probe (substrate) distance. The characterized regimes were employed to deposit amorphous carbon at different values of kinetic energy of the ions and plasma density. The mean kinetic energy of the ions could be changed from 40 to 300 eV, and the plasma density could be varied from 1 × 10 12 to 7 × 10 13 cm -3. The main emitting species were C + (283.66, 290.6, 299.2 and 426.65 nm) and C ++ (406.89 and 418.66 nm) with the C + (426.65 nm) being the most intense and that which persisted for the longest times. Different combinations of the plasma parameters yield amorphous carbon with different structures. Low levels (about 40 eV) of ion energy produce graphitic materials, while medium levels (about 200 eV) required the highest plasma densities in order to increase the C sbnd C sp 3 bonding content and therefore the hardness of the films. The structure of the material was studied by means of Raman spectroscopy, and the hardness and elastic modulus by depth sensitive nanoindentation.

Camps, Enrique; Escobar-Alarcón, L.; Castrejón-Sánchez, V. H.; Camacho-López, M. A.; Muhl, Stephen

2007-10-01

229

High-resolution ablation of amorphous polymers using CO2 laser irradiation  

NASA Astrophysics Data System (ADS)

Etching of various amorphous polymers by the application of CO2 laser radiation (10.6 ?m) is described. By passage of the radiation through a high-resolution mask in contact with the polymer surface, this ablation can produce images having submicron resolution and good edge acuity. The laser intensity required for ablation is compared for various thermoplastic and thermosetting polymers. Below the required level of intensity, no ablation is observed, but the laser irradiation can result in thermal crystallization. The energy necessary to induce ablation with infrared radiation is comparable to that required for UV decomposition.

Sonnenschein, Mark F.; Roland, C. Michael

1990-07-01

230

Comparative study of gelatin ablation by free-running and Q-switch modes of Er:YAG laser  

Microsoft Academic Search

To optimize the laser ablation of soft wet tissues by Er:YAG laser radiation at 2.94 micrometers the dynamics of ablation is investigated by high-speed photography techniques. Gelatin as model material is used.

Vitaly I. Konov; Lev A. Kulevsky; Alexei V. Lukashev; Vladimir P. Pashinin; Alexander S. Silenok

1991-01-01

231

Treatment of lymphangioma circumscriptum using fractional carbon dioxide laser ablation.  

PubMed

Lymphangioma circumscriptum remains a challenging entity to treat given anatomic considerations and a significant tendency for recurrence regardless of the modality selected. Surgical excision offers the greatest potential for definitive management but is often beset by procedural morbidity and suboptimal cosmetic outcomes. A range of palliative options have been reported for the treatment of lymphangioma circumscriptum, with varying degrees of associated efficacy and morbidity. This report describes the novel use of fractional carbon dioxide laser ablation for the treatment of lymphangioma circumscriptum, with promising cosmetic results and durable symptomatic relief. PMID:23758048

Shumaker, Peter R; Dela Rosa, Kristina M; Krakowski, Andrew

2013-01-01

232

Laser Ablation of Metals Johannes Roth, Carolina Trichet, Hans-Rainer-Trebin, and Steffen Sonntag  

E-print Network

Laser Ablation of Metals Johannes Roth, Carolina Trichet, Hans-Rainer-Trebin, and Steffen Sonntag. The interaction of the laser light with the electrons is described by a continuum equation and #12;2 Johannes Roth

Roth, Johannes

233

Visual laser ablation of the prostate (VLAP) with the prostascope  

NASA Astrophysics Data System (ADS)

Introduction: Laser ablation of the prostatic tissue or laser prostatectomy, is used as an alternative method to traditional endoscopic resection of the prostate. The usual side-firing Nd:YAG laser fiber for the treatment of obstructive symptoms has operational difficulties, a high cost and often poor early results. Materials: We describe the laser coagulation of the prostate using a 600-um bare fiber inserted in a modified Albarran bridge which included at the tip, a new gold-plated deflectable reflector. The complete device passes through a 21Fr.rigid cysto- urethroscope. The system and the fiber can be used for several dozen treatments. The dosimetry was 2000 J per 1 cc of prostatic tissue. Methods: VLAP using the prostascope was performed on more than 70 men in one institution, and 150 in a second one, for obstructive symptoms due to benign prostatic hyperplasia. The parameter included AUA symptom score, flow rate, residual volume and complications. Data were obtained preoperatively and 1, 3, 6 and 12 months after treatment. Discussion: According to our data VLAP with this system is a save, minimal invasive and effective treatment. Results are comparable to other non-contact laser devices. As the gold-plated reflector is inexpensive and the standard bare fiber can be used repeatedly, the cost is less than of an usual side-firing laser fiber.

Mattioli, Stefano; Cremona, M.; Ackaert, K. J.

1997-12-01

234

Characterization of laser ablation of copper in the irradiance regime of laser-induced breakdown spectroscopy analysis  

NASA Astrophysics Data System (ADS)

The LIBS signal depends both on the ablated mass and on the plasma excitation temperature. These fundamental parameters depend in a complex manner on laser ablation and on laser-plasma coupling. As several works in the literature suggest that laser ablation processes play a predominant role compared to plasma heating phenomena in the LIBS signal variations, this paper focuses on the study of laser ablation. The objective was to determine an interaction regime enabling to maximally control the laser ablation. Nanosecond laser ablation of copper at 266 nm was characterized by scanning electron microscopy and optical profilometry analysis, in air at 1 bar and in the vacuum. The laser beam spatial profile at the sample surface was characterized in order to give realistic values of the irradiance. The effect of the number of accumulated laser shots on the crater volume was studied. Then, the ablation crater morphology, volume, depth and diameter were measured as a function of irradiance between 0.35 and 96 GW/cm². Results show that in the vacuum, a regular trend is observed over the whole irradiance range. In air at 1 bar, below a certain irradiance, laser ablation is very similar to the vacuum case, and the ablation efficiency of copper was estimated at 0.15 ± 0.03 atom/photon. Beyond this irradiance, the laser beam propagation is strongly disrupted by the expansion of the dense plasma, and plasma shielding appears. The fraction of laser energy used for laser ablation and for plasma heating is estimated in the different irradiance regimes.

Picard, J.; Sirven, J.-B.; Lacour, J.-L.; Musset, O.; Cardona, D.; Hubinois, J.-C.; Mauchien, P.

2014-11-01

235

Effects of plasma confinement on the femtosecond laser ablation of silicon  

NASA Astrophysics Data System (ADS)

We investigated the femtosecond laser ablation of silicon in a confined condition by covering the surface of a silicon wafer with a glass slide. The ablation was carried out by either irradiating the focused spot with different numbers of pulses or by scanning the laser beam on the surface of the silicon wafer. The morphology of the ablated surface was characterized by scanning electron microscope. For laser fluences much larger than the ablation threshold of silicon, cylindrical holes were generated in the confined ablation, in sharp contrast to the conical holes observed in the ablation performed in open air. Accordingly, grooves with U-shaped and V-shaped cross sections were achieved in the ablations carried out in the confined condition and in open air, respectively. For laser fluences close to the ablation threshold of silicon, the difference in the morphology of micro- and nanostructures obtained by these two ablation methods became not pronounced and two-dimensional nanohole arrays were created on the surface of silicon wafer. While the period of the nanohole arrays in the direction of the laser polarization was found to be close to the laser wavelength, the period in the direction perpendicular to the laser polarization was observed to be more than two times of the laser wavelength. In addition, the distribution of erupted nanoparticles was also found to be different in the two ablation processes. A ring-shaped distribution of nanoparticles was observed in the open air ablation while a monotonic decrease of nanoparticle density along the radial direction was found in the confined ablation.

Zhang, Chengyun; Yao, Jianwu; Lan, Sheng; Trofimov, Vyacheslav A.; Lysak, Tatiana M.

2013-11-01

236

The role of laser wavelength on plasma generation and expansion of ablation plumes in air  

E-print Network

and surface melting, ablation and plasma formation, laser-plasma interaction, shock wave for- mation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma. The presence of an ambient gas dramatically affects the laser-target and laser plasma coupling, as well

Harilal, S. S.

237

Measurement of depth profile of hydrogen isotope atom contained in solid material using resonant laser ablation  

Microsoft Academic Search

The depth profile of hydrogen isotope atoms was measured by using mass spectrometry combined with resonant laser ablation. A graphite sample was implanted with deuterium by a cyclotron and was employed for the measurements. The graphite sample was ablated by a tunable laser which wavelength was corresponding to the resonant wavelength of 1S - 2S for deuterium with two- photon

Masafumi Yorozu; Yasuhiro Okada; Terunobu Nakajyo; Akira Endo

1999-01-01

238

Nanoscale patterning of graphene through femtosecond laser ablation R. Sahin, E. Simsek, and S. Akturk  

E-print Network

graphene sheets can easily be produced using standard chemical vapor deposition (CVD) method.5 High spatial works on the issue, Kalita et al. use the fs laser ablation method to produce 5 lm width grapheneNanoscale patterning of graphene through femtosecond laser ablation R. Sahin, E. Simsek, and S

Simsek, Ergun

239

Laser Ablation (LA-ICPMS) at the Institute of Mineralogy, University of WÃrzburg  

NSDL National Science Digital Library

This website from the University of Wuerzburg briefly describes laser ablation, the most versatile in-situ solid sampling technique for ICP mass spectrometry. The website also features a section detailing applications for laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), including trace element concentration and chemical zoning, and others.

University of Wü Institute of Mineralogy; Rzburg; Wãrzburg, University O.

240

Application of the laser ablation for conservation of historical paper documents  

Microsoft Academic Search

Laser ablation was applied for surface cleaning and spectroscopic diagnostics of historical paper documents and model samples in the framework of the conservation projects. During cleaning the spectra of ablation products were recorded by means of the LIBS technique which allowed for nearly non-destructive identification of surface layers such as contaminants, substrate and pigments. For consecutive laser pulses a strong

A. Kaminska; M. Sawczak; K. Komar; G. ?liwi?ski

2007-01-01

241

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

242

Determination of intratest variability of trace elements in foraminifera by laser ablation inductively coupled  

E-print Network

inductively coupled plasma-mass spectrometry E. C. Hathorne, O. Alard, R. H. James, and N. W. Rogers, Mg, Mn, Cu, Zn, Sr and Ba) within foraminifera tests using laser ablation inductively coupled plasma of trace elements in foraminifera by laser ablation inductively coupled plasma-mass spectrometry, Geochem

Demouchy, Sylvie

243

Major element analysis of natural silicates by laser ablation ICP-MS Munir Humayun,*a  

E-print Network

Major element analysis of natural silicates by laser ablation ICP-MS Munir Humayun,*a Fred A (EMP) analysis to provide complementary information on major element constituents. Here, we present a method for laser ablation ICP-MS analysis of major elements in silicate glasses and minerals that, when

Weston, Ken

244

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

245

A Hybrid MD-DSMC Model of Picosecond Laser Ablation and Desorption  

E-print Network

model of the evolution of a plume generated by laser ablation of an organic solid is presented interaction cross sections. The MD breathing sphere model [15], used for simulation of the initial stageA Hybrid MD-DSMC Model of Picosecond Laser Ablation and Desorption Michael I. Zeifman* , Barbara J

Zhigilei, Leonid V.

246

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

247

Phase explosion in atmospheric pressure infrared laser ablation from water-rich targets  

E-print Network

Phase explosion in atmospheric pressure infrared laser ablation from water-rich targets Zhaoyang pressure. It incorporates the nonlinear absorption of water and the phase explosion due to superheating explosion on laser ablation dynamics, and it is relevant for the preparative, analytical, and medical

Vertes, Akos

248

Comparison of holmium:YAG and thulium fiber laser lithotripsy: ablation thresholds, ablation rates, and retropulsion effects  

NASA Astrophysics Data System (ADS)

The holmium:YAG (Ho:YAG) laser lithotriptor is capable of operating at high pulse energies, but efficient operation is limited to low pulse rates (~10 Hz) during lithotripsy. On the contrary, the thulium fiber laser (TFL) is limited to low pulse energies, but can operate efficiently at high pulse rates (up to 1000 Hz). This study compares stone ablation threshold, ablation rate, and retropulsion for the two different Ho:YAG and TFL operation modes. The TFL (? = 1908 nm) was operated with pulse energies of 5 to 35 mJ, 500-?s pulse duration, and pulse rates of 10 to 400 Hz. The Ho:YAG laser (? = 2120 nm) was operated with pulse energies of 30 to 550 mJ, 350-?s pulse duration, and a pulse rate of 10 Hz. Laser energy was delivered through 200- and 270-?m-core optical fibers in contact mode with human calcium oxalate monohydrate (COM) stones for ablation studies and plaster-of-Paris stone phantoms for retropulsion studies. The COM stone ablation threshold for Ho:YAG and TFL measured 82.6 and 20.8 J/cm2, respectively. Stone retropulsion with the Ho:YAG laser linearly increased with pulse energy. Retropulsion with TFL was minimal at pulse rates less than 150 Hz, then rapidly increased at higher pulse rates. For minimal stone retropulsion, Ho:YAG operation at pulse energies less than 175 mJ at 10 Hz and TFL operation at 35 mJ at 100 Hz is recommended, with both lasers producing comparable ablation rates. Further development of a TFL operating with both high pulse energies of 100 to 200 mJ and high pulse rates of 100 to 150 Hz may also provide an alternative to the Ho:YAG laser for higher ablation rates, when retropulsion is not a primary concern.

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

2011-07-01

249

Process and structures for fabrication of solar cells with laser ablation steps to form contact holes  

DOEpatents

Contact holes of solar cells are formed by laser ablation to accomodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thickness.

Harley, Gabriel; Smith, David D; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

2013-11-19

250

Micromachining of ridge optical waveguides on top of He{sup +}-implanted {beta}-BaB{sub 2}O{sub 4} crystals by femtosecond laser ablation  

SciTech Connect

We report on a technique for the fabrication of ridge optical waveguides on top of {beta}-BaB{sub 2}O{sub 4} (BBO) crystals. The BBO crystals were first implanted by He{sup +} ions to form planar optical waveguides. In the second step, the femtosecond laser ablation technique was employed for micromachining of ridge-type optical waveguides. A thorough study of material-specific ablation parameters for BBO has been performed in order to achieve ablated structures with smooth sidewalls. A further process of Ar{sup +} ion smoothing in a plasma chamber was used to reduce the sidewall roughness of the ablated ridges from 75 to 35 nm root mean square. We demonstrated optical waveguiding in these femtosecond-ablated plasma-treated waveguides and measured total propagation losses of less than 10 dB/cm at 532 nm, making them suitable for nonlinear- and electro-optical applications.

Degl'Innocenti, R.; Reidt, S.; Guarino, A.; Rezzonico, D.; Poberaj, G.; Guenter, P. [Nonlinear Optics Laboratory, Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich (Switzerland)

2006-12-01

251

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

2007-02-01

252

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

253

Laser Ablation Characterization in Laboratori Nazionali di Legnaro  

NASA Astrophysics Data System (ADS)

Using high power laser focalized into a target material generates plasma and it has the consequence to immediately extract and ionize atoms from the target itself. This process is the starting point to have a simple and compact ion source, usually named Laser Ion Source (LIS). This kind of sources are arising in the scenario of ion sources especially in refractory elements ions production, where the atomization of the material to ionize is the main issue because of its high evaporating temperature. These considerations and the fact that ion sources are becoming nowadays more and more important to several fields of science and technology, open an interesting line of research that our group at Laboratori Nazionali di Legnaro wants to investigate. Experiment involves characterization of produced ions by measuring charge state and amount of ions created. Measurements will be performed with several power densities and varying ions collector distance and potential respect to the target. These simple experiments are the necessary preliminary steps to characterize the system and to start a solid future development onto possible different and effective ways to perform ions sources using laser.

Scarpa, D.; Nicolosi, P.; Franci, A.; Tomaselli, A.; Manzolaro, M.; Corradetti, S.; Vasquez, J.; Rossignoli, M.; Calderolla, M.; Monetti, A.; Andrighetto, A.; Prete, G.

2014-04-01

254

Nanofabrication for micropatterned cell arrays by combining electron beam-irradiated polymer grafting and localized laser ablation.  

PubMed

Most methods reported for cell-surface patterning are generally based on photolithography and use of silicon or glass substrates with processing analogous to semiconductor manufacturing. Herein, we report a novel method to prepare patterned plastic surfaces to achieve cell arrays by combining homogeneous polymer grafting by electron beam irradiation and localized laser ablation of the grafted polymer. Poly(N-isopropylacrylamide) (PIPAAm) was covalently grafted to surfaces of tissue culture-grade polystyrene dishes. Subsequent ultraviolet ArF excimer laser exposure to limited square areas (sides of 30 or 50 microm) produced patterned ablative photodecomposition of only the surface region (approximately 100-nm depth). Three-dimensional surface profiles showed that these ablated surfaces were as smooth and flat as the original tissue culture-grade polystyrene surfaces. Time-of-flight secondary ion mass spectrometry analysis revealed that the ablated domains exposed basal polystyrene and were surrounded with PIPAAm-grafted chemistry. Before cell seeding, fibronectin was adsorbed selectively onto ablated domains at 20 degrees C, a condition in which the non-ablated grafted PIPAAm matrix remains highly hydrated. Hepatocytes seeded specifically adhered onto the ablated domains adsorbed with fibronectin. Because PIPAAm, inhibits cell adhesion and migration even at 37 degrees C when the grafted density is > 3 microg/cm2, all the cells were confined within the ablated domains. A 100-cell domain array was achieved by this method. This surface modification technique can be utilized for fabrication of cell-based biosensors as well as tissue-engineered constructs. PMID:14666924

Yamato, Masayuki; Konno, Chie; Koike, Shunsuke; Isoi, Yuki; Shimizu, Tasuya; Kikuchi, Akihiko; Makino, Kimiko; Okano, Teruo

2003-12-15

255

Fabrication of high-density pitch adapters by laser ablation  

NASA Astrophysics Data System (ADS)

High Energy Physics experiments make extensive use of micro-strip silicon sensors for tracking purposes. However, the high granularity of the modern detectors makes the connection between the segmented sensor channels and the readout electronics very complex. Enhancing the complexity, a direct connection is not possible in most of the cases due to the mismatch between the detector pad pitch and the electronics. A new method based on laser technology is presented for the fabrication of pitch adapters. In this new method the high-density metal traces are manufactured by means of laser ablation of the metal layer deposited on top of a substrate. Glass, Kapton and Silicon substrates were metal coated and tested for the fabrication of pitch adapters. Finally, a metal-on-glass prototype has been successfully manufactured and tested for electrical conductivity, bondability and metrology. Detectors have been assembled using this pitch adapters design and tested in particle beams at CERN.

Rey-García, F.; Bao-Varela, C.; Pérez, E.; Rodríguez, P.; Gallas, A.; de la Fuente, G. F.

2014-05-01

256

Laser ablation and the unzipping of addition polymer  

NASA Astrophysics Data System (ADS)

Ability to control decomposition path and products for addition polymers is important in many applications ranging from thin film fabrication and basic understanding of reaction kinetics to evaluating the feasibility of thermal routes for the recycling of addition polymers. Laser ablation, a technique widely used to deposit thin films of a variety of inorganic materials, can also be used as a simple and highly versatile method for the deposition of thin polymer films of materials that are difficult to process and studying decomposition kinetics as well. In situ studies of the products formed by the laser/polymer interaction suggest that, as in standard pyrolysis, decomposition of poly(tetrafluoroethylene), poly(methylmethacrylate), and poly(?-methyl styrene) proceeds via chain unzipping leading to monomer. Unexpectedly, high monomer yields are also observed for addition polymers that pyrolyze by random scission producing little or no monomer. Examples of such materials presented here include poly(vinylfluoride) and polypropylene.

Blanchet, Graciela B.

1996-10-01

257

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

258

Background gas collisional effects on expanding fs and ns laser ablation plumes  

NASA Astrophysics Data System (ADS)

The collisional effects of a background gas on expanding ultrafast and short pulse laser ablation plumes were investigated by varying background pressure from vacuum to atmospheric pressure levels. For producing Cu ablation plumes, either 40 fs, 800 nm pulses from a Ti: Sapphire laser or 6 ns, 1,064 nm pulses from a Nd:YAG laser were used. The role of background pressure on plume hydrodynamics, spectral emission features, absolute line intensities, signal to background ratios and ablation craters was studied. Though the signal intensities were found to be maximum near to atmospheric pressure levels, the optimum signal to background ratios are observed ~20-50 Torr for both ns and fs laser ablation plumes. The differences in laser-target and laser-plasma couplings between ns and fs lasers were found to be more engraved in the crater morphologies and plasma hydrodynamic expansion features.

Harilal, S. S.; Farid, N.; Freeman, J. R.; Diwakar, P. K.; LaHaye, N. L.; Hassanein, A.

2014-10-01

259

Direct Drive Beryllium Ablator Capsules for the Omega Laser  

NASA Astrophysics Data System (ADS)

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 hemispheres affects the implosion. Our proposed design calls for an 1180 micron outisde diameter capsule with 40 micron thick beryllium walls containing 50 atm of deuterium gas. Some of the capsules will also have 0.05 atm of argon. We plan to image the joints with argon fluorescence from inside the capsule. Our plan is to use a 1 ns square pulse with 30 kJ of laser energy. With this drive, we expect the convergence ratio to be about 6.5 to 7. Depending on the capsule design details, we expect that the peak temperature will be 490 ± 40 eV, and the neutron yield will be anywhere from 1× 10^8 to 8× 10^8 neutrons. Some of the uncertainty comes from whether or not we use argon and questions about how much mix the copper-brazed joint will cause. The yield also depends strongly on which beryllium alloy we use. We calculate better implosions in direct drive with pure beryllium, but requirements on allowable grain size may force us to use copper-doped beryllium, which would reduce the yield by about 50%.

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

2001-10-01

260

Manufacture of miniature bioparticle electromanipulators by excimer laser ablation  

NASA Astrophysics Data System (ADS)

Multilevel microelectrode structures have been produced using excimer laser ablation techniques to obtain devices for the electro-manipulation of bioparticles using traveling electric field dielectrophoresis effects. The system used to make these devices operates with a krypton fluoride excimer laser at a wavelength of 248 nm and with a repetition rate of 100 Hz. The laser illuminates a chrome-on-quartz mask which contains the patterns for the particular electrode structure being made. The mask is imaged by a high- resolution lens onto the sample. Large areas of the mask pattern are transferred to the sample by using synchronized scanning of the mask and workpiece with sub-micron precision. Electrode structures with typical sizes of approximately 10 micrometers are produced and a multi-level device is built up by ablation of electrode patterns and layered insulators. To produce a traveling electric field suitable for the manipulation of bioparticles, a linear array of 10 micrometers by 200 micrometers microelectrodes, placed at 20 micrometers intervals, is used. The electric field is created by energizing each electrode with a sinusoidal voltage 90 degree(s) out of phase with that applied to the adjacent electrode. On exposure to the traveling electric field, bioparticles become electrically polarized and experience a linear force and so move along the length of the linear electrode array. The speed and direction of the particles is controlled by the magnitude and frequency of the energizing signals. Such electromanipulation devices have potential uses in a wide range of biotechnological diagnostic and processing applications. Details of the overall laser projection system are presented together with data on the devices which have been manufactured so far.

Gower, Malcolm C.; Harvey, Erol C.; Rizvi, Nadeem H.; Rumsby, Phil T.; Burt, Julian P.; Talary, Mark S.; Tame, John A.; Pethig, Ron

1998-06-01

261

Laser ablation and high precision patterning of biomaterials and intraocular lenses  

NASA Astrophysics Data System (ADS)

The use of intraocular lenses (IOL) is the most promising method for restoring excellent vision in cataract surgery. In addition, multifocal intraocular lenses for good distant and near vision are investigated. Several new materials, techniques and patterns are studied for the formation and etching of intraocular lenses in order to improve their optical properties and reduce the diffractive aberrations. As pulsed laser ablation is well established as a universal tool for surface processing of organic polymer materials, this study was focused in using laser ablation with short and ultra short laser pulses for surface modification of PMMA and intraocular lenses, instead of using other conventional techniques. The main advantage of using very short laser pulses, e.g. of ns, ps or fs duration, is that heat diffusion into the polymer material is negligible. As a result high precision patterning of the sample, without thermal damage of the surroundings, becomes possible. In this study, laser ablation was performed using commercially available hydrophobic acrylic IOLs, hydrophilic acrylic IOLs, and PMMA IOLs, with various diopters. We investigated the ablation efficiency and the phenomenology of the etched patterns by testing the ablation rate, versus laser energy fluence, at several wavelengths and the surface modification with atomic force microscopy (AFM), or scanning electron microscopy (SEM). The irradiated polymers have different optical properties, at the applied wavelengths, and therefore, present different ablation behaviour and morphology of the laser ablated crater walls and surrounding surfaces. The experimental results, some theoretical assumptions for mathematical modeling of the relevant ablation mechanisms are discussed.

Serafetinides, A. A.; Spyratou, E.; Makropoulou, M.

2010-10-01

262

High-speed machining of glass materials by laser-induced plasma-assisted ablation using a 532-nm laser  

NASA Astrophysics Data System (ADS)

In this communication, we report a high-speed machining of glass materials by a novel laser ablation technique using a conventional visible laser for the first time. A high-quality micrograting structure is fabricated in fused quartz by laser-induced plasma-assisted ablation (LIPAA) using a second harmonic of Q-switched Nd+:YAG laser (532 nm). The plasma generated from a silver (Ag) target by the laser irradiation effectively assists in ablation of the fused quartz substrate by the same laser beam, although the laser beam is transparent to the substrate. A grating with a cross-sectional shape like a square-wave (period 20 ?m) is achieved using the mask projection technique. The ablation rate reaches several tens nm/pulse. In addition, LIPAA is applied to high-speed hole drilling (700 ?m in diameter) of fused-quartz (0.5 mm thick) and Pyrex glass (0.5 mm thick).

Zhang, J.; Sugioka, K.; Midorikawa, K.

263

Single-shot ablation threshold of chromium using UV femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Single-shot ablation threshold for thin chromium film was studied using 266 nm, femtosecond laser pulses. Chromium is a useful material in the nanotechnology industry and information on ablation threshold using UV femtosecond pulses would help in precise micromachining of the material. The ablation threshold was determined by measuring the ablation crater diameters as a function of incident laser pulse energy. Absorption of 266 nm light on the chromium film was also measured under our experimental conditions, and the absorbed energy single-shot ablation threshold fluence was 46 ± 5 mJ/cm2. The experimental ablation threshold fluence value was compared to time-dependent heat flow calculations based on the two temperature model for ultrafast laser pulses. The model predicts a value of 31.6 mJ/cm2 which is qualitatively consistent with the experimentally obtained value, given the simplicity of the model.

Banerjee, S. P.; Fedosejevs, R.

2014-07-01

264

Hydrodynamic modeling of femtosecond laser ablation of metals in vacuum and in liquid  

NASA Astrophysics Data System (ADS)

We numerically examine the mechanisms involved in nanoparticle formation by laser ablation of metallic targets in vacuum and in liquid. We consider the very early ablation stage providing initial conditions for much longer plume expansion processes. In the case of ultrashort laser ablation, the initial population of primary nanoparticles is formed at this stage. When a liquid is present, the dynamics of the laser plume expansion differs from that in vacuum. Low compressibility of the ambient liquid results in strong confinement conditions. As a result, ablation threshold rises drastically, the ablated material is compressed, part of it becomes supersaturated and the backscattered material additionally heats the target. The extension of a molten layer leads to the additional ablation at a later stage also favoring nanoparticle formation. The obtained results thus explain recent experimental findings and help to predict the role of the experimental parameters. The performed analysis indicates ways of a control over nanoparticle synthesis.

Povarnitsyn, Mikhail E.; Itina, Tatiana E.

2014-10-01

265

Morphological features of silicon substrate by using different frequency laser ablation in air and water  

NASA Astrophysics Data System (ADS)

The interaction of the nanosecond laser (FWHM = 30 ns, ? = 355 nm) and monocrystalline silicon is investigated in air and water. Conventional optical and scanning electron microscopes are used to characterize surface ablation of the monocrystalline silicon. A numerical model is used to ascertain the time of the bubble motion in water. Morphological features of the laser-induced crater are different under various environments and frequencies. More debris is found when using high frequency ablation, and a larger zone is affected by heat when using low frequency ablation in air. There is no debris found in water, and the morphology of craters is better in low frequency ablation than that in high frequency ablation because bubbles generated by high frequency ablation affect laser transmission.

Xu, J. Y.; Hu, H.; Lei, Y. L.

2014-10-01

266

[The deposition of elements in the process of laser ablation of silicon].  

PubMed

Laser processing in the semiconductor industry (especially silicon material) has broad application prospects. The interaction between the laser and silicon is complex, and the present paper mainly studied the silicon morphology in UV laser ablation and the influence law of ambient gas. Studies have shown that the laser plasma ionization effect of silicon in the UV laser ablation has a decisive impact: the removal of the material becomes possible because of generating gasification and ionization, laser plasma shock wave can make phase transition material discharge effectively, and laser plasma spectroscopy ionization effect can make the oxygen elements in the air ionize and deposit effectively. PMID:23697147

Wang, Shao-Peng; Feng, Guo-Ying; Duan, Tao; Han, Jing-Hua

2013-02-01

267

3D photomechanical model of tooth enamel ablation by Er-laser radiation  

NASA Astrophysics Data System (ADS)

The three-dimensional (3D) photomechanical model of human tooth enamel ablation is described. It takes into account: the structural peculiarities of enamel, Er-laser beam energy spatial distribution and laser radiation attenuation in the tissue. Dynamics change of enamel coefficient of absorption during ablation is also discussed. We consider the 3D photomechanical model of incomplete removal (modification) of the enamel rods by the pressure of water contained in the enamel pores and heated by laser radiation, and complete removal (ablation) of the enamel rods as result of hydroxyapatite heated by laser radiation and evaporation. Modeling results are in close agreement with the experimental results.

Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

2014-02-01

268

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.

2007-06-01

269

Laser Ablation Increases PEM/Catalyst Interfacial Area  

NASA Technical Reports Server (NTRS)

An investigational method of improving the performance of a fuel cell that contains a polymer-electrolyte membrane (PEM) is based on the concept of roughening the surface of the PEM, prior to deposition of a thin layer of catalyst, in order to increase the PEM/catalyst interfacial area and thereby increase the degree of utilization of the catalyst. The roughening is done by means of laser ablation under carefully controlled conditions. Next, the roughened membrane surface is coated with the thin layer of catalyst (which is typically platinum), then sandwiched between two electrode/catalyst structures to form a membrane/ele c t - rode assembly. The feasibility of the roughening technique was demonstrated in experiments in which proton-conducting membranes made of a perfluorosulfonic acid-based hydrophilic, protonconducting polymer were ablated by use of femtosecond laser pulses. It was found that when proper combinations of the pulse intensity, pulse-repetition rate, and number of repetitions was chosen, the initially flat, smooth membrane surfaces became roughened to such an extent as to be converted to networks of nodules interconnected by filaments (see Figure 1). In further experiments, electrochemical impedance spectroscopy (EIS) was performed on a pristine (smooth) membrane and on two laser-roughened membranes after the membranes were coated with platinum on both sides. Some preliminary EIS data were interpreted as showing that notwithstanding the potential for laser-induced damage, the bulk conductivities of the membranes were not diminished in the roughening process. Other preliminary EIS data (see Figure 2) were interpreted as signifying that the surface areas of the laser-roughened membranes were significantly greater than those of the smooth membrane. Moreover, elemental analyses showed that the sulfur-containing molecular groups necessary for proton conduction remained intact, even near the laser-roughened surfaces. These preliminary results can be taken as indications that laser-roughened PEMs should function well in fuel cells and, in particular, should exhibit current and power densities greater than those attainable by use of smooth membranes.

Whitacre, Jay; Yalisove, Steve

2009-01-01

270

Production of stripper foils by laser ablation of carbon-boron sputter targets  

NASA Astrophysics Data System (ADS)

The TRIUMF Applied Technology Group operates several high-power industrial cyclotrons for commercial radioisotope production. Two of these accelerators, TR30-1 and TR30-2, can deliver H - beams of 30 MeV and beam currents in excess of 1000 ?A. For many years, in-house produced diamond-like carbon (DLC) foils of approximately 2.0-3.0 ?m thickness have been utilized to extract proton beams from these accelerators. The TRIUMF Carbon Foil Laboratory uses pulsed laser deposition to manufacture DLC films in a wide thickness range (10 nm to ˜10 ?m). It is known that the quality and the composition of the graphite sputter target used in the laser ablation process has a significant effect on the mechanical properties of the deposited film as well as its durability in ion beams. Encouraged by the findings of Sugai et al. [1], we investigated the production of stripper foils by laser ablation of graphite/boron composites as well as multilayer foils using pure graphite and boron targets.

Zeisler, Stefan K.; Jaggi, Vinder

2010-02-01

271

Particle Generation by Pulsed Excimer Laser Ablation in Liquid: Hollow Structures and Laser-Induced Reactions  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of solid targets in liquid media is a powerful method to fabricate micro-/nanoparticles, which has attracted much interest in the past decade. It represents a combinatorial library of constituents and interactions, and one can explore disparate regions of parameter space with outcomes that are impossible to envision a priori. In this work, a pulsed excimer laser (wavelength 248 nm, pulse width 30 ns) has been used to ablate targets in liquid media with varying laser fluences, frequencies, ablation times and surfactants. It is observed that hollow particles could be fabricated by excimer laser ablation of Al, Pt, Zn, Mg, Ag, Si, TiO2, and Nb2O5 in water or aqueous solutions. The hollow particles, with sizes from tens of nanometers to micrometers, may have smooth and continuous shells or have morphologies demonstrating that they were assembled from nanoparticles. A new mechanism has been proposed to explain the formation of these novel particle geometries. They were formed on laser-produced bubbles through bubble interface pinning by laser-produced solid species. Considering the bubble dynamics, thermodynamic and kinetic requirements have been discussed in the mechanism that can explain some phenomena associated with the formation of hollow particles, especially (1) larger particles are more likely to be hollow particles; (2) Mg and Al targets have stronger tendency to generate hollow particles; and (3) the 248 nm excimer laser is more beneficial to fabricate hollow particles in water than other lasers with longer wavelengths. The work has also demonstrated the possiblities to fabricate novel nanostructures through laser-induced reactions. Zn(OH)2/dodecyl sulfate flower-like nanostructures, AgCl cubes, and Ag2O cubes, pyramids, triangular plates, pentagonal rods and bars have been obtained via reactions between laser-produced species with water, electrolyes, or surfactant molecules. The underlying mechanisms of forming these structures have been discussed. The experimental results and the associated mechanisms developed in my research, and described in this thesis, have enriched the current understanding of particle generation by pulsed laser ablation in liquid. In so doing, my research has expanded the mechanistic routes for novel, or designer, nanoparticle geometries. Within the combinatorial and non-equilibrium environment provided by the unique experimental arrangement, the basic laws of material science still apply. Understanding and utilizing the laws will help researchers to fabricate new nanostructures by this and other methods providing similar environment.

Yan, Zijie

272

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Smoothing of ablation pressure nonuniformities in the laser-plasma corona during heating of laser fusion targets  

Microsoft Academic Search

A method for smoothing ablation pressure nonuniformities during heating of laser fusion targets is described which utilises an extra laser pulse preceding the main pulse. Theoretical and experimental data are presented on heating of thin (3-10 mum) foils (simulating the target shell) by a spatially nonuniform laser beam. In the experiments, the laser pulse width at half maximum was 2

M. A. Zhurovich; O. A. Zhitkova; I. G. Lebo; Yu A. Mikhailov; G. V. Sklizkov; Aleksandr N. Starodub; V. F. Tishkin

2009-01-01

273

Fabrication of Fresnel microlens with excimer laser contour ablation  

NASA Astrophysics Data System (ADS)

Laser micromachining systems based on excimer lasers are usually oriented to work with mask projection regime because of the low pulse repetition rate as well as large beam aperture of the laser source. In case of fabricating of the complex 3D structures, this approach introduces a number of limitations. Alternative solution might be usage of direct writing laser mode. Some examples of the so called contour ablation approach for fabricating microlenses with an absolutely monotonically changing cross-sectional profile are presented in the literature. Based on this idea and introducing new variables like automatic mask selection as well as optimizing process algorithms led us to obtain more versatile method for shape approximation. Hence, there were fabricated structures with cross-sectional profiles described as functions that are monotonic on specified intervals such as Fresnel microlenses. In this paper we describe approximation of process parameters for obtaining desired cross-sectional profiles and finally fabrication of few exemplary microlenses. All structures were characterized by a digital optical microscopy and compared to the given profiles. The accuracy of reproduction of the desired structures at the level of single microns was achieved.

Wójcik, Micha? R.; Anto?czak, Arkadiusz J.; Kozio?, Pawe? E.; ?azarek, ?ukasz K.; Stepak, Bogusz D.; Abramski, Krzysztof M.

2014-08-01

274

Atomistic investigation of ablation of amorphous polystyrene under femtosecond laser pulse  

NASA Astrophysics Data System (ADS)

In the present work we elucidate the thermodynamic mechanisms of femtosecond (fs) laser ablation of amorphous polystyrene by means of molecular dynamics (MD) simulations. The effects of extrinsic parameter of laser pulse intensity and intrinsic parameter of molecular architecture on the laser ablation are further studied. Simulation results show that the laser ablation-induced polymeric material removal is achieved by evaporation from the surface and expansion within the bulk. Furthermore, inter-chain sliding and intra-chain change also play important roles in the microscopic deformation of the material. It is found that both the laser pulse intensity and the arrangement of phenyl groups have significant influence on the fs laser ablation of polystyrene.

Huang, YanHua; Song, ChengWei; Zhang, JunJie; Sun, Tao

2014-09-01

275

Dynamics of femto-and nanosecond laser ablation plumes investigated using optical emission spectroscopy  

E-print Network

emission lifetime. Though both ns and fs laser-plasmas showed similar temperatures ($1 eV), the fs LPP representation of laser-target and laser-plasma coupling along with emission in the visible region is given density surpasses the ablation threshold of the material. The laser-target interaction involves many

Harilal, S. S.

276

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

277

Smoothing of ablation pressure nonuniformities in the laser-plasma corona during heating of laser fusion targets  

Microsoft Academic Search

A method for smoothing ablation pressure nonuniformities during heating of laser fusion targets is described which utilises an extra laser pulse preceding the main pulse. Theoretical and experimental data are presented on heating of thin (3–10 ?m) foils (simulating the target shell) by a spatially nonuniform laser beam. In the experiments, the laser pulse width at half maximum was 2

M A Zhurovich; O A Zhitkova; I G Lebo; Yu A Mikhailov; G V Sklizkov; Aleksandr N Starodub; V F Tishkin

2009-01-01

278

Smoothing of ablation pressure nonuniformities in the laser-plasma corona during heating of laser fusion targets  

Microsoft Academic Search

A method for smoothing ablation pressure nonuniformities during heating of laser fusion targets is described which utilises an extra laser pulse preceding the main pulse. Theoretical and experimental data are presented on heating of thin (3-10 m) foils (simulating the target shell) by a spatially nonuniform laser beam. In the experiments, the laser pulse width at half maximum was 2

M A Zhurovich; Yu A Mikhailov; G V Sklizkov; Aleksandr N Starodub; O A Zhitkova; I G Lebo; V F Tishkin

2009-01-01

279

Modeling of plume dynamics with shielding in laser ablation of carbon  

NASA Astrophysics Data System (ADS)

The process of laser ablation of carbon in presence of background gas is simulated numerically. The plume dynamics in laser ablation is important to study for many reasons including temperature of plume particles and shielding of target by previously ablated plumes. Shielding leads directly to the change in energy deposition of incident laser pulse at the target surface and in turn influences the ablation dynamics and amount of material removed. Carbon ablation is studied for single and multiple laser hits typical for synthesis of nanotubes. Two models of correction of ablated velocity and pressure resulting from shielding effect are proposed and investigated. Numerical modeling of this plume dynamics and its integral effect of shielding is challenging due to inherent high nonlinearity of the problem. Some of available numerical techniques handles nonlinearity but are dissipative, e.g. Godunov type schemes. Other techniques are less dissipative but fail to account for strong nonlinearity typical for initial stages of ablation, e.g. the ENO-Roe. To effectively model this highly nonlinear plume dynamics a combination of two of above mentioned schemes is developed so as the numerical evaluation of fluxes is close to their physical values and the scheme has minimum dissipation. The non-monotonic behavior of ablated mass as a function of time duration between two laser pulses is studied.

Pathak, Kedar; Povitsky, Alex

2007-05-01

280

Depth profiling of tin-coated glass by laser ablation inductively coupled plasma emission spectrometry with acoustic signal measurement.  

PubMed

A pulsed, frequency-quadrupled Nd:YAG laser (266 nm, 10 Hz) coupled to an inductively coupled plasma atomic emission spectrometer (ICP-AES) was employed for depth profiling by ablation of a pyrolytically deposited Sn layer (300 nm) on float glass. The procedure consisted of performing individual ablation cycles (layer-by-layer). A raster with stroke distance of either 50 microm or 200 microm (the raster density) was used as an ablation pattern. The ablation was stopped after each cycle and the peak area of the resulting transient optical signal of the ICP discharge was plotted against the cycle number. The ablation rate of 90 to 20 nm per cycle at a low-energy pulse (6 mJ to 1 mJ) was determined by profilometry. A beam masking was employed to attenuate the laser shot energy and to eliminate the peripheral irregularity of the beam profile. Almost uniform removal of the square area (1 mm x 1 mm) of the coating by ablation was achieved by combining the fitted raster density, beam masking, focusing and beam energy. Different ablation processes were distinguished in cases of the tin coating and the uncoated glass surface. While the coating was mainly evaporated, the uncoated glass surface exhibited a crumbling associated with production of glass powder. This was confirmed by electron microscopy observations. The measured acoustic signal followed the behavior of the emission intensity of the Sn line and was supposed to be proportional to the amount of Sn vapors. The emission intensity depth profile of the Sn coating with graded structure was obtained, which qualitatively corresponded with the depth profile measured by secondary ion mass spectrometry. PMID:11225664

Kanický, V; Otruba, V; Mermet, J M

2000-02-01

281

Simulation of Laser Interaction with Ablative Plasma and ydrodynamic of Laser Supported Plasma(LSP)  

NASA Astrophysics Data System (ADS)

A general Godunov finite difference schemes-WENO(Weighted Essentially Non-Oscillatory) Schemes which have fifth-order accuracy was used to make a numerical calculation for 2-dimensional axis symmetrical laser-supported plasma flow field under laser ablated solid target. The models of the calculation of ionization degree of plasma and the interaction between laser beam and plasma and the simplified eos(equation of state) of plasma were considered in the simulation. The plasma field parameters during and after laser duration variation with time are also obtained. The simulation results show that the laser beam power was strong absorbed by plasma of target surface, and the velocity of LSD(Laser Supported Detonation) wave is half of ideal LSD value which derived from C-J detonation theory.

Huifeng, Tong; Zhiping, Tang

2011-06-01

282

Alternatives to excimer laser refractive surgery: UV and mid-infrared laser ablation of intraocular lenses and porcine cornea  

NASA Astrophysics Data System (ADS)

Despite the fact that the laser applications in human ophthalmology are well established, further research is still required, for better and predictable ablation dosimetry on both cornea tissue and intraocular lenses. Further studies for alternative laser sources to the well established excimer lasers, such as UV or mid-infrared solid state lasers, have been proposed for refractive surgery. The precise lens ablation requires the use of laser wavelengths possessing a small optical penetration depth in the cornea and in the synthetic lenses, in order to confine the laser energy deposition to a small volume. In order to eliminate some very well known problems concerning the reshaping of cornea and the modification of the optical properties of the intraocular lenses, ablation experiments of ex vivo porcine cornea, acrylic PMMA and hydrophilic lenses were conducted with an Er:YAG laser (2.94 ?m) and the fifth harmonic of a Nd:YAG laser (213 nm). The morphology of cornea was recorded using a cornea topography system before and immediately after the ablation. Histology analysis of the specimens was obtained, in order to examine the microscopic appearance of the ablated craters and the existence of any thermal damage caused by the mid-infrared and UV laser irradiation. The macroscopic morphology of the intraocular lens craters was inspected with an optical transmission microscope. Measurements of the ablation rates of the lenses were performed and simulated by a mathematical model.

Serafetinides, A. A.; Makropoulou, M.; Spyratou, E.; Bacharis, C.

2007-03-01

283

Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.  

PubMed

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach. PMID:22565342

Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

2013-01-01

284

Spindle Assembly and Architecture: From Laser Ablation to Microtubule Nucleation  

NASA Astrophysics Data System (ADS)

Spindles are arrays of microtubules that segregate chromosomes during cell division. It has been difficult to validate models of spindle assembly due to a lack of information on the organization of microtubules in these structures. Here we present a novel method, based on femtosecond laser ablation, capable of measuring the detailed architecture of spindles. We used this method to study the metaphase spindle and find that microtubules are shortest near poles and become progressively longer towards the center of the spindle. These data, in combination with mathematical modeling, high resolution imaging, and biochemical perturbations, are sufficient to reject previously proposed mechanisms of spindle assembly. Our results support a new model of spindle assembly in which microtubule polymerization dynamics are not spatially regulated, microtubule transport locally sorts microtubules -- determining their proper organization in the spindle without moving them appreciable distances --, and the profile of microtubule nucleation controls the length of the spindle.

Needleman, Daniel; Brugues, Jan; Nuzzo, Valeria; Mazur, Eric

2012-02-01

285

Laser Ablation of Gallium Arsenide in Different Solutions  

SciTech Connect

The optical, structural, and nonlinear optical characteristics of GaAs nanoparticles obtained by laser ablation in different liquids were investigated. Thermally induced self-defocusing in GaAs solutions was observed using both a high pulse repetition rate and nanosecond pulses. In studying the nonlinear optical characteristics of GaAs solutions using picosecond and femtosecond pulses, two-photon absorption was observed. The nonlinear absorption coefficient of an aqueous GaAs solution measured by the Z-scan technique and the nonlinear susceptibility of GaAs nanoparticles were, respectively, 0.7 x 10{sup -9} cm W{sup -1} and 2 x 10{sup -9} esu at a wavelength of 795 nm.

Ganeev, R.A.; Kuroda, H. [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Ryasnyanskii, A.I. [Samarkand State University, Samarkand, 703004 (Uzbekistan)

2005-12-15

286

Fabrication of pillared PLGA microvessel scaffold using femtosecond laser ablation  

PubMed Central

One of the persistent challenges confronting tissue engineering is the lack of intrinsic microvessels for the transportation of nutrients and metabolites. An artificial microvascular system could be a feasible solution to this problem. In this study, the femtosecond laser ablation technique was implemented for the fabrication of pillared microvessel scaffolds of polylactic-co-glycolic acid (PLGA). This novel scaffold facilitates implementation of the conventional cell seeding process. The progress of cell growth can be observed in vitro by optical microscopy. The problems of becoming milky or completely opaque with the conventional PLGA scaffold after cell seeding can be resolved. In this study, PLGA microvessel scaffolds consisting of 47 ?m × 80 ?m pillared branches were produced. Results of cell culturing of bovine endothelial cells demonstrate that the cells adhere well and grow to surround each branch of the proposed pillared microvessel networks. PMID:22605935

Wang, Hsiao-Wei; Cheng, Chung-Wei; Li, Ching-Wen; Chang, Han-Wei; Wu, Ping-Han; Wang, Gou-Jen

2012-01-01

287

Iron carbide nanoparticles produced by laser ablation in organic solvent  

NASA Astrophysics Data System (ADS)

Laser ablation of iron in an organic solvent (pentane, hexane, or decane) was performed using an air-tight cell to produce iron carbide nanoparticles. Mössbauer spectra of the nanoparticles were obtained at room temperature. They revealed that the nanoparticles consisted of two paramagnetic components and magnetic components. The two paramagnetic components were a high-spin Fe(II) species and an amorphous iron carbide containing a large amount of carbon. Whereas the magnetic components measured at room temperature exhibited superparamagnetism, those measured at low temperature were fitted by a combination of four sextets, which were assigned to Fe7 C 3. The Fe7 C 3 yield was higher in higher molecular weight solvents. Transmission electron microscopy (TEM) images of the samples showed that the nanoparticles were spherical with diameters in the range 10-100 nm.

Matsue, T.; Yamada, Y.; Kobayashi, Y.

2012-03-01

288

Synthesis of magnetic nanoparticles by pulsed laser ablation  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles were prepared by laser ablation of Fe foil in ethanol. The nanoparticles consisted of Fe3O4 and Fe3C and were superparamagnetic with a saturation magnetization Ms = 124 emu/g. Zero field cooled (ZFC) measurements collected at an applied field of 50 Oe displayed a maximum magnetic susceptibility at 120 K with a broad distribution. Field cooled (FC) measurements collected during cooling and heating showed a thermal hysteresis indicative of temperature dependent magnetic viscosity. The magnetic viscosity was calculated from thermoremanent magnetization (TRM) plots and it increased with decreasing temperature. The activation volume of these non uniform magnetic states was calculated from TRM measurements and it was found to decrease with decreasing temperature. The decrease in activation diameters was interpreted as a decrease in exchange length, and hence a decrease in particle-particle interactions.

Franzel, L.; Bertino, M. F.; Huba, Z. J.; Carpenter, E. E.

2012-11-01

289

Moessbauer Study of Iron Films Produced by Laser Ablation  

SciTech Connect

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 Moessbauer 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 the surface plane. Formation of Fe-Al alloy was observed at the boundary between the Fe-films and the Al substrate, and the composition of the Fe-Al alloy was a function of the Al substrate temperature during the deposition. Doublet absorption of FeAl was observed for the sample formed at 10 K, and distributed magnetic splitting with disordered compositions of Fe-Al alloy was observed for the samples formed at 293 K. When the sample was formed at 573 K, two sets of sextets with sharp absorptions were observed indicating the formation of Fe3Al. The films were also examined using scanning electron microscopy (SEM). Similarly, samples of laser-evaporated iron on Si substrates were studied, and alloys of Fe-Si were found. Fe3Si and FeSi were produced when the laser-deposition was performed on Si substrates at 573 K.

Namiki, Kentarou; Yokoyama, Daisuke; Yamada, Yasuhiro [Department of Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)

2005-04-26

290

Synthesis of stable silver colloids by laser ablation in water  

NASA Astrophysics Data System (ADS)

The stable colloid with silver nanoparticles has been produced by irradiation of metal target in deionized water by pulse 1064 nm laser. The dependences of the nanoparticle size and colloid stability on fluence, ablation time, surface conditions of the target, and thickness of the water layer have been studied. The sizes and shape of nanoparticles have been measured by dynamic light scattering and by scanning electron microscopy. It has been shown that decrease of the water layer thickness above the target surface leads to increase of the colloid stability. The proper number of treatment cycles allowed to prepare the target surface for production of the nanoparticles with average size about 34 nm obtained by statistical analysis of the scanning electron microscope images. Several methods have been used to increase the colloid stability: (1) increase of the laser fluence, (2) decrease of the water layer thickness above the target surface, (3) the treatment of the target surface by laser beam scanning. The subsequent increase of the colloid concentration by partial drying slightly enhanced the nanoparticle size. The optimized synthesis conditions and drying parameters allowed to produce the pure colloid with concentration about 0.5 g/l and stability over a month of almost spherical silver nanoparticles with typical size 45±5 nm.

Tyurnina, Anastasiya E.; Shur, Vladimir Y.; Kozin, Roman V.; Kuznetsov, Dmitry K.; Mingaliev, Evgeny A.

2013-11-01

291

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

292

Preparation of nano-size particles of silver with femtosecond laser ablation in water  

NASA Astrophysics Data System (ADS)

Nano-size particles of Ag were prepared by laser ablation in water with femtosecond laser pulses at 800 nm. The formation efficiency and the size of colloidal particles were compared with those of colloidal particles prepared by nanosecond laser pulses. The formation efficiency for femtosecond pulses was significantly lower than that for nanosecond pulses. The size of colloids prepared by femtosecond pulses were less dispersed than that of colloids prepared by nanosecond pulses. The shape of the craters on the targets suggested that ablation process was different between femtosecond and nanosecond ablation. In addition, it was found that the ablation efficiency for femtosecond ablation in water was lower than that in air, while that for nanosecond pulses was similar in both water and air.

Tsuji, Takeshi; Kakita, Toshihiko; Tsuji, Masaharu

2003-02-01

293

Wavelength dependence of boron nitride ablation by TEA CO2 lasers  

NASA Astrophysics Data System (ADS)

Transversely excited atmospheric (TEA) CO2 laser ablation of boron nitride ceramics in both cubic and hexagonal phases (cBN, hBN) was demonstrated. A TEA CO2 laser oscillating at a wavelength of 9.2 ?m, which coincides with a TO-phonon spectrum of the cBN, could ablate the cBN ceramics more efficiently than with 10 ?m band radiation. The hBN samples were also ablated well with 9.2 ?m laser irradiation, however, the ablated site color changed to black due to a boron rich phase left on the surface. In the case of hBN sintered with Al2O3 and SiO2, the ablation threshold fluence is determined by the one of Al2O3, which is the highest threshold among the three elements.

Sumiyoshi, Tetsumi; Tomita, Hiroyuki; Takahashi, Akihisa; Obara, Minoru; Ishii, Katsunori

1996-05-01

294

Comparison of separation performance of laser-ablated and wet-etched microfluidic devices  

PubMed Central

Laser ablation of glass allows for production of microfluidic devices without the need of hydrofluoric acid and photolithography. The goal of this study was to compare the separation performance of microfluidic devices produced using a low-cost laser ablation system and conventional wet etching. During laser ablation, cracking of the glass substrate was prevented by heating the glass to 300°C. A range of laser energy densities was found to produce channel depths ranging from 4 – 35 ?m and channel widths from 118 – 162 ?m. The electroosmotic flow velocity was lower in laser-ablated devices, 0.110 ± 0.005 cm s?1, as compared to wet-etched microfluidic chips, 0.126 ± 0.003 cm s?1. Separations of both small and large molecules performed on both wet- and laser-ablated devices were compared by examining limits of detection, theoretical plate count, and peak asymmetry. Laser-induced fluorescence detection limits were 10 pM fluorescein for both types of devices. Laser-ablated and wet-etched microfluidic chips had reproducible migration times with ? 2.8% RSD and peak asymmetries ranging from 1.0 – 1.8. Numbers of theoretical plates were between 2.8- and 6.2-fold higher on the wet-etched devices compared to laser-ablated devices. Nevertheless, resolution between small and large analytes was accomplished, which indicates that laser ablation may find an application in pedagogical studies of electrophoresis or microfluidic devices, or in settings where hydrofluoric acid cannot be used. PMID:20827468

Baker, Christopher A.; Bulloch, Rayford; Roper, Michael G.

2010-01-01

295

Laser-ablation ICP-MS as a tool for whole rock trace element analyses on fused powders  

NASA Astrophysics Data System (ADS)

Here we present an accurate and precise technique for routine trace element analysis of geologic materials by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We focus on rock powders previously prepared for X-ray fluorescence by fusion in a Li2B4O7 flux, and subsequently quenched in a Pt mold to form a glass disk. Our method allows for the analysis up to 30 trace elements by LA-ICP-MS using a Photon-Machines Analyte G2 193 nm excimer laser coupled to a Thermo-Fisher Scientific ICAP Q quadrupole ICP-MS. Analyses are run as scans on the surface of the disks. Laser ablation conditions for which trace element fractionation effects are minimal have been empirically determined to be ~ 4 J m-2 fluence, at 10 Hz , and 10 ?m s-1 scan speed, using a 110 ?m laser beam size. Ablated material is carried into the ICP-MS by a He carrier at a rate of 0.75 L min-1. Following pre-ablation to remove surface particles, samples are ablated for 200 s, of which 140 s are used for data acquisition. At the end of each scan, a gas blank is collected for 30 s. Dwell times for each element vary between 15 and 60 ?s, depending on abundance and instrument sensitivity, allowing 120 readings of each element during the data acquisition time window. To correct for variations in the total volume of material extracted by the laser, three internal standards are used, Ca, Fe and Zr. These elements are routinely analyzed by X-ray fluorescence by the Geoanalytical laboratory at Michigan State University with precision and accuracy of <5%. The availability of several internal standards allows for better correction of possible persisting laser ablation fractionation effects; for a particular trace element, we correct using the internal standard that best reproduces its ablation behavior. Our calibration is based on a combination of fused powders of US Geological Survey and Geological Survey of Japan rock standards, NIST SRM 612 glass, and US Geological Survey natural and synthetic basalt glasses. Instrumental drift is monitored during each run using two fused standards analyzed multiple times as unknowns. We routinely achieve an external precision of <5% on multiple replicates of standards run as unknowns, which are also within <5% of certified values. Elements analyzed include most first row transition metals, large ion lithophile elements, high field strength elements, lanthanide and actinide rare earth elements.

Girard, G.; Rooney, T. O.

2013-12-01

296

LASER ABLATION SYNTHESIS OF ZINC OXIDE CLUSTERS: A NEW FAMILY OF FULLERENES?  

E-print Network

1 LASER ABLATION SYNTHESIS OF ZINC OXIDE CLUSTERS: A NEW FAMILY OF FULLERENES? Alexander V to fullerenes. A local abundance minimum at n = 13 provides an additional evidence for the presence in the ablation plume of fullerene-like (ZnO)n clusters. #12;2 Recently much interest has been shown in Zn

Paris-Sud XI, Université de

297

Laser flash photography of cold cavitation-driven ablation in tissues  

Microsoft Academic Search

Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped

Alexander A. Oraevsky; Rinat O. Esenaliev; Steven L. Jacques; Frank K. Tittel

1995-01-01

298

Modeling CO{sub 2} laser ablation impulse of polymers in vapor and plasma regimes  

SciTech Connect

An improved model for CO{sub 2} laser ablation impulse in polyoxymethylene and similar polymers is presented that describes the transition effects from the onset of vaporization to the plasma regime in a continuous fashion. Several predictions are made for ablation behavior.

Sinko, John E. [Micro-Nano Global Center of Excellence, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Phipps, Claude R. [Photonic Associates LLC, 200A Ojo de la Vaca Road, Santa Fe, New Mexico 87508 (United States)

2009-09-28

299

Formation of periodic structures upon laser ablation of metal targets in liquids  

SciTech Connect

Experimental data on the formation of ordered microstructures produced upon ablation of metal targets in liquids irradiated by a copper vapour laser or a pulsed Nd:YAG laser are presented. The structures were obtained on brass, bronze, copper, and tungsten substrates immersed in distilled water or ethanol. As a result of multiple-pulse laser ablation by a scanning beam, ordered microcones with pointed vertexes are formed on the target surface. The structures are separated by deep narrow channels. The structure period was experimentally shown to increase linearly with diameter of the laser spot on the target surface. (interaction of laser radiation with matter)

Kazakevich, Pavel V; Simakin, Aleksandr V; Shafeev, Georgii A [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2005-09-30

300

Comparison of silver nanoparticles confined in nanoporous silica prepared by chemical synthesis and by ultra-short pulsed laser ablation in liquid  

NASA Astrophysics Data System (ADS)

Hexagonally ordered mesoporous silica materials, MCM-41 and SBA-15, have been synthesized and loaded with Ag nanoparticles, utilizing both chemical synthesis and ultra-short pulsed laser ablation in liquid. In laser ablation, a silver target, immersed in aqueous suspension of ordered mesoporous silica SBA-15, was irradiated by ultra-short laser pulses to generate silver nanoparticles. For comparison, samples of similar silver contents were prepared either by incorporating silver into the SBA-15 during a hydrothermal synthesis or by introducing silver in MCM-41 by template ion-exchange. Samples were characterized by XRD, N2 physisorption, TEM and UV-vis spectroscopy. All preparations contained significant amount of 5-50 nm size silver agglomerates on the outer surface of the silica particles. The laser ablation process did not cause significant destruction of the SBA-15 structure and metallic silver (Ag0) nanoparticles were mainly generated. It is demonstrated that by laser ablation in aqueous silica suspension smaller and more uniform metallic silver particles can be produced and loaded on the surface of the silica support than by synthesis procedures. Catalytic properties of the samples have been tested in the total oxidation of toluene. Because of its favorable Ag dispersity, the Ag/SBA-15 catalyst, generated by the laser ablation method, had better catalytic stability and, relative to its Ag load, higher activity than the conventional Ag/SBA-15 preparations.

Szegedi, Á.; Popova, M.; Valyon, J.; Guarnaccio, A.; De Stefanis, A.; De Bonis, A.; Orlando, S.; Sansone, M.; Teghil, R.; Santagata, A.

2014-10-01

301

Advanced diagnostics and applications of pulsed ion beams and lasers  

SciTech Connect

Several kinds of experiments are shown concerning the generation diagnostics and applications of pulsed ion beams and lasers. The authors are interested in a few research fields of ICF, material and space sciences. Several high voltage machines both at Yokohama and Albuquerque were used to produce ion beams and laser lights. Proton beams of a few hundred kV energy were produced with a conventional magnetically insulated diode. A cryogenic anode with N{sub 2}O ice as the candidate ion source was operated with the same kind of high voltage apparatus, and the beam species and divergence were measured with the Baryotrak. The purpose of this experiment was to check the possibility o medium mass ion beams as the ICF energy driver in the near future. Various species of ion beams were focused on to a few kinds of targets, and the ablation processes were observed. Two of the aims of these experiments were (1) to clarify the basic processes and (2) to apply the beams to material processing. One of the methods was to make thin films of YBCO or C{sub 3}N{sub 4} as examples. Two kinds of KrF and a CO{sub 2} laser were planned to be applied to targets ablation. The authors use targets at cryogenic and room temperature, and substrates at cryogenic and high temperature. They also made some numerical simulations of target ablation processes with these lasers. The results will be presented, if they shall have enough minutes during the conference session. They also want to use the beams to simulate wall materials for the future advanced ICF reactors with lasers and Z pinches.

Kasuya, K.; Yamashita, T.; Kishi, Y. [and others

1999-07-01

302

The FTICRMS laser microprobe: Speciation of surfaces in resonant laser ablation/ionization (RLA)  

NASA Astrophysics Data System (ADS)

The coupling of a tunable laser with a laser microprobe FT-ICR-MS prototype developed at the University of Metz made it possible to carry out the first RLA-FTICRMS experiment, which combines the selectivity and the sensitivity of two photon resonant laser ablation/ionization and the high accuracy mass measurement. This technique is a tool for the direct analysis of organic (or inorganic) traces on surfaces. The selectivity of the element's detection depends on the choice of resonant line, and on the screen effect of gazeous plume emitted by the laser pulse. In fact, the resonant two photons processes are most effective when the laser power density is lower than 5.108 W/cm2 because the gaseous cloud is relatively transparent in this condition.

Muller, Jean-François; Krier, Gabriel; Aubriet, Frédéric; Vernex-Loset, Lionel; Courrier, Benoît

2001-08-01

303

Measurements of Laser Intensity Dependence of High Specific Impulse for Laser Ablative Propulsion  

SciTech Connect

One of the advantages of laser propulsion is the possibility of controlling exhaust velocity namely specific impulse and optimization of energy and propellant usage. Characteristics of laser plasma interaction with the incident laser intensities of 107{approx}1010W/cm2 have been investigated using multiple plasma diagnostics such as ion collector. Electron temperatures will be discussed.

Bato, Masafumi [Institute of Laser Engineering, Osaka Univ., Osaka (Japan); Uchida, Shigeaki; Shimada, Yoshinori [Institute for Laser Technology, Osaka (Japan)

2004-03-30

304

Laser ion source for heavy ion synchrotrons (invited)  

Microsoft Academic Search

A status overview of the development of laser ion sources suited to heavy ion synchrotrons is presented. The results of experimental and theoretical studies, recently obtained at a number of laboratories, for laser-produced highly charged heavy ions are summarized for plasmas heated by long wavelength lasers. Design of a powerful repetition rate CO2 laser, target interaction chamber, and extraction system

B. Yu. Sharkov; S. Kondrashev; I. Roudskoy; S. Savin; A. Shumshurov; H. Haseroth; H. Kugler; K. Langbein; N. Lisi; H. Magnusson; R. Scrivens; J. C. Schnuringer; J. Tambini; S. Homenko; K. Makarov; V. Roerich; A. Stepanov; Yu. Satov

1998-01-01

305

Computer Simulations of Laser Ablation of Molecular Substrates Leonid V. Zhigilei* and Elodie Leveugle  

E-print Network

of laser plasma thrusters for micro- satellites.10 Further optimization of experimental parameters picture of the ablation process. Time-resolved spectroscopy and imaging methods have been also employed

306

In situ photography of picosecond laser ablation of nickel D.A. Willis1  

E-print Network

In situ photography of picosecond laser ablation of nickel D.A. Willis1 , X. Xu* School. The fundamental and second harmonic wavelengths were used for the pump and probe beams, respectively. The probe

Xu, Xianfan

307

Slit Skiascopic-guided Ablation Using the Nidek Laser  

Microsoft Academic Search

PURPOSE: To present the approach of using a scanning slit refractometer (the ARK 10000) in con- junction with a corneal topography system to guide customized corneal ablation. This diagnostic system is coupled with the Nidek EC-5000 system which combines scanning slit and a scanning small area ablation (1.0 mm) to perform a customized ablation. METHODS: The ARK 10000 diagnostic system

Scott MacRae; Masanao Fujieda

2000-01-01

308

Visualization of microsecond laser ablation of porcine clot and gelatin under a clear liquid  

Microsoft Academic Search

Laser thrombolysis uses microsecond laser pulses to remove thrombus-blocked arteries in the heart and the brain. Rapidly expanding and collapsing vapor bubbles are formed upon absorption of the laser energy by the thrombus. The goal of this study was to visualize the process of ablation and assess the effects of pulse repetition rate. The differences between contact versus non-contact of

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

1996-01-01

309

Preparation and morphology control of silver colloids by laser ablation in water  

Microsoft Academic Search

Nano-size colloids of silver were prepared by laser ablation in water in various conditions of laser pulses, such as wavelength, intensity, and pulse duration. The formation efficiency, the size, and the size distribution of colloids were varied with these conditions. It was suggested that interaction between laser pulses and colloidal particles plays important roles in the formation process. It is

T. Tsuji; N. Watanabe; T. Kakita; M. Tsuji

2003-01-01

310

Preparation of nano-size particles of silver with femtosecond laser ablation in water  

Microsoft Academic Search

Nano-size particles of Ag were prepared by laser ablation in water with femtosecond laser pulses at 800nm. The formation efficiency and the size of colloidal particles were compared with those of colloidal particles prepared by nanosecond laser pulses. The formation efficiency for femtosecond pulses was significantly lower than that for nanosecond pulses. The size of colloids prepared by femtosecond pulses

Takeshi Tsuji; Toshihiko Kakita; Masaharu Tsuji

2003-01-01

311

Internal structure and expansion dynamics of laser ablation plumes into ambient gases  

E-print Network

:YAG laser. The diagnostic tools include fast photography of overall visible plume emission using a 2 ns- pendent on irradiation conditions such as incident laser in- tensity and pulse duration, laser wavelength scattering.17 Fast photography adds another dimen- sion to ablation diagnostics by providing two

Harilal, S. S.

312

Modeling of the ablation source in laser-ultrasonics  

NASA Astrophysics Data System (ADS)

For the excitation of ultrasound by optical irradiation two principal mechanisms play a role. One of them, the so-called thermoplastic effect has been quantitatively described by several groups. In this work, a quantitative model describing the second effect, the excitation of ultrasonic signals by evaporation of the surface of the material onto which the laser pulses impinges, is presented. The evaporation, the expansion of the evaporated material as well as the interaction with the optical radiation is treated in a one-dimensional model. The pressure exerted on the surface of the specimen which results from the expanding vaporized material is used as source for the generation of the ultrasonic signals in the material or component insonified. There is an optical intensity at which the broadband ultrasonic signals exhibit maximal amplitude. The amplitude of the ultrasonic signals calculated using the model presented and the amount of ablated material are compared with experimental results. Despite the simplifications made, the agreement between theory and experiment is excellent for steel and satisfactory for aluminum. The results of this work can be used to optimize the parameters for a laser-based ultrasonic inspection system.

Hoffmann, A.; Arnold, W.

2000-05-01

313

Particle formation by infrared laser ablation of MALDI matrix compounds.  

PubMed

The concentration and size distribution of particles ablated from the infrared matrix-assisted laser desorption/ionization matrix compounds succinic acid (butanedioic acid), ?-cyano-4-hydroxycinnamic acid, and glycerol were measured using an aerodynamic particle sizer combined with a scanning mobility particle sizer. The two sizing instruments together had a sizing range to from 10?nm to 20?µm. Thin layers of the matrix compounds were irradiated with fluences between 6.0 and 9.5?kJ/m(2) and wavelengths between 2.8 and 3.0?µm. The distribution of particles was characterized by a large concentration of clusters in the 20-nm-diameter range and large component of mass in the range of coarse particle with diameters greater than 1?µm. The wavelength dependence revealed a blue shift for the maximum particle production that is attributed to heating and disruption of the hydrogen bonds in the matrix that shifts the absorption to shorter wavelengths. This blue shift has been observed previously in infrared matrix-assisted laser desorption/ionization. PMID:25044838

Musapelo, Thabiso; Murray, Kermit K

2014-07-01

314

Excimer laser ablation for spatially controlled protein patterns  

NASA Astrophysics Data System (ADS)

Two-dimensional control over the location of proteins on surfaces is desired for a number of applications including diagnostic tests and tissue engineered medical devices. Many of these applications require patterns of specific proteins that allow subsequent two-dimensionally controlled cell attachment. The ideal technique would allow the deposition of specific protein patterns in areas where cell attachment is required, with complete prevention of unspecific protein adsorption in areas where cells are not supposed to attach. In our study, collagen I was used as an example for an extracellular matrix protein known to support the attachment of bovine corneal epithelial cells. An allylamine plasma polymer was deposited on a silicon wafer substrate, followed by grafting of poly(ethylene oxide). Two-dimensional control over the surface chemistry was achieved using a 248 nm excimer laser. Results obtained by XPS and AFM show that the combination of extremely low-fouling surfaces with excimer laser ablation can be used effectively for the production of spatially controlled protein patterns with a resolution of less than 1 micrometers . Furthermore, it was shown that bovine corneal epithelial cell attachment followed exactly the created protein patterns. The presented method is an effective tool for a number of in vitro and in vivo applications.

Thissen, Helmut; Hayes, Jason P.; Kingshott, Peter; Johnson, Graham; Harvey, Erol C.; Griesser, Hans J.

2001-11-01

315

Focal Laser Ablation of Prostate Cancer: Definition, Needs, and Future  

PubMed Central

Current challenges and innovations in prostate cancer management concern the development of focal therapies that allow the treatment of only the cancer areas sparing the rest of the gland to minimize the potential morbidity. Among these techniques, focal laser ablation (FLA) appears as a potential candidate to reach the goal of focusing energy delivery on the identified targets. The aim of this study is to perform an up-to-date review of this new therapeutic modality. Relevant literature was identified using MEDLINE database with no language restrictions (entries: focal therapy, laser interstitial thermotherapy, prostate cancer, FLA) and by cross-referencing from previously identified studies. Precision, real-time monitoring, MRI compatibility, and low cost of integrated system are principal advantages of FLA. Feasibility and safety of this technique have been reported in phase I assays. FLA might eventually prove to be a middle ground between active surveillance and radical treatment. In conclusion, FLA may have found a role in the management of prostate cancer. However, further trials are required to demonstrate the oncologic effectiveness in the long term. PMID:22666240

Colin, Pierre; Mordon, Serge; Nevoux, Pierre; Marqa, Mohammed Feras; Ouzzane, Adil; Puech, Philippe; Bozzini, Gregory; Leroux, Bertrand; Villers, Arnauld; Betrouni, Nacim

2012-01-01

316

Nanometer thickness laser ablation for spatial control of cell attachment  

NASA Astrophysics Data System (ADS)

We demonstrate here a new method to control the location of cells on surfaces in two dimensions, which can be applied to a number of biomedical applications including diagnostic tests and tissue engineered medical devices. Two-dimensional control over cell attachment is achieved by generation of a spatially controlled surface chemistry that allows control over protein adsorption, a process which mediates cell attachment. Here, we describe the deposition of thin allylamine plasma polymer coatings on silicon wafer and perfluorinated poly(ethylene-co-propylene) substrates, followed by grafting of a protein resistant layer of poly(ethylene oxide). Spatially controlled patterning of the surface chemistry was achieved in a fast, one-step procedure by nanometer thickness controlled laser ablation using a 248 nm excimer laser. X-ray photoelectron spectroscopy and atomic force microscopy were used to confirm the production of surface chemistry patterns with a resolution of approximately 1 µm, which is significantly below the dimensions of a single mammalian cell. Subsequent adsorption of the extracellular matrix proteins collagen I and fibronectin followed by cell culture experiments using bovine corneal epithelial cells confirmed that cell attachment is controlled by the surface chemistry pattern. The method is an effective tool for use in a number of in vitro and in vivo applications.

Thissen, H.; Hayes, J. P.; Kingshott, P.; Johnson, G.; Harvey, E. C.; Griesser, H. J.

2002-10-01

317

A Laser Ablation Method for the Synthesis of Crystalline Semiconductor Nanowires  

Microsoft Academic Search

A method combining laser ablation cluster formation and vapor-liquid-solid ( VLS) growth was developed for the synthesis of semiconductor nanowires. In this process, laser ablation was used to prepare nanometer-diameter catalyst clusters that define the size of wires produced by VLS growth. This approach was used to prepare bulk quantities of uniform single-crystal silicon and germanium nanowires with diameters of

Alfredo M. Morales; Charles M. Lieber

1998-01-01

318

Formation of Au(III)DNA Coordinate Complex by Laser Ablation of Au Nanoparticles in Solution  

Microsoft Academic Search

We discovered that an Au(III)-DNA coordinate complex, Au(III)(DNA-base)2(amine)l, are formed by laser ablation of Au nanoparticles in an aqueous solution containing DNA molecules in the presence of amines and multi-valent cations, where l represents an unknown ligand (either amine or water). Optical absorption spectrum of the solution after laser ablation exhibited a 360 nm absorption peak assigned to ligand?Au(III) charge

Yoshihiro Takeda; Tamotsu Kondow; Fumitaka Mafuné

2005-01-01

319

X-ray Diffraction of Permalloy Nanoparticles Fabricated by Laser Ablation in Water  

SciTech Connect

Permalloy (NiFeMo) nanoparticles were fabricated by laser ablation of bulk material in water with a UV pulsed laser. Transmission electron microscope images showed that approximately spherical particles about 50 nm in diameter were formed in the ablation process. All diffraction peaks corresponding to the bulk material were present in the nanoparticles. In addition to these peaks several new peaks were observed in the nanoparticles, which were attributed to nickel oxide.

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

2009-01-01

320

Local wettability tuning with laser ablation redeposits on PDMS  

NASA Astrophysics Data System (ADS)

In this paper, we present a method to locally control the wettability behavior of PDMS surfaces by excimer laser ablation. In the ablation process, a micrometer scale roughness is formed in the irradiated regions while a nanometer scale roughness is formed by the redeposits surrounding the irradiated regions. The increase in surface roughness results in a change of the wettability behavior of the PDMS surface. By using a hexagonal pattern and tuning the patterning pitch, two different wetting behaviors were realized. A pitch smaller than 300 ?m resulted in a superhydrophobic surface with an advancing contact angle of ?adv = 165° and a receding contact angle of ?rec = 160°. A pitch between 300 and 500 ?m resulted in a sticky superhydrophobic surface with ?adv = 120-150° and ?rec = 80°. The contact angle hysteresis for the latter was larger than for untreated PDMS resulting in very sticky surfaces with high sliding angles. This gives the method great versatility since the two wetting behaviors are very different. By combining both behaviors, local surface features like pinning sites, non-wetting sites, barriers and guides can all be fabricated by a single method. As an application demonstrator of the method, we show that drops can be caught and released depending on size and tilting angle by creating slippery surfaces with sticky barriers. Additionally, the method is ideal for rapid prototyping as it consist of only a single step. It is a direct write method requiring no lithographic mask. Also the process works in ambient atmosphere, so it can be used for temperature or pressure sensitive applications.

van Pelt, Stijn; Frijns, Arjan; Mandamparambil, Rajesh; den Toonder, Jaap

2014-06-01

321

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

NASA Astrophysics Data System (ADS)

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 essential media, 8% fetal bovine serum, 0.125% HEPES buffer solution, 0.125% gentamicin, and 0.05% fungizone. The entire tissue frame and media container were kept in an incubator at 37 degrees Celsius and 5% CO2. Serial macroscopic photographs of the cultured corneas were taken during the healing process. Histology was performed after 30 days of culture. Results: A clear ablated crater into the stroma was observed immediately after the ablation. The thickness of thermal damage ranges between 1 and 25 micrometer. Haze development within the crater varies from the third day to the fourteenth day according to the depth and the roughness of the crater. Histologic sections of the cultured cornea showed complete re- epithelization of the lased area. Loose fibrous tissue is observed filling the ablated space beneath the epithelium. The endothelium appeared unaffected. Conclusions: The intensity and time of haze development appears dependent upon the depth of the ablation. Cultured human corneas may provide useful information regarding the healing process following laser ablation.

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

1998-06-01

322

Confocal Microscopy-Guided Laser Ablation for Superficial and Early Nodular Basal Cell Carcinoma  

PubMed Central

Importance Laser ablation is a rapid and minimally invasive approach for the treatment of superficial skin cancers, but efficacy and reliability vary owing to lack of histologic margin control. High-resolution reflectance confocal microscopy (RCM) may offer a means for examining margins directly on the patient. Observations We report successful elimination of superficial and early nodular basal cell carcinoma (BCC) in 2 cases-, using RCM imaging to guide Er-:YAG laser ablation. Three-dimensional (3-D) mapping is feasible with RCM-, to delineate the lateral border and thickness of the tumor. Thus, the surgeon may deliver laser fluence and passes with localized control—ie, by varying the ablation parameters in sub-lesional areas with specificity that is governed by the 3-D topography of the BCC. We further demonstrate intra-operative detection of residual BCC after initial laser ablation and complete removal of remaining tumor by additional passes. Both RCM imaging and histologic sections confirm the final clearance of BCC. Conclusions and Relevance Confocal microscopy may enhance the efficacy and reliability of laser tumor ablation. This report represents a new translational application for RCM imaging, which, when combined with an ablative laser, may one day provide an efficient and cost-effective treatment for BCC. PMID:24827701

Chen, Chih-Shan Jason; Sierra, Heidy; Cordova, Miguel; Rajadhyaksha, Milind

2014-01-01

323

Bubble formation induced by nanosecond laser ablation in water and its diagnosis by optical transmission technique  

NASA Astrophysics Data System (ADS)

In this paper, bubble formation and ablation rate in laser ablation of a thin-film aluminum target are studied. The target was an aluminum thin-film coated on a quartz substrate and interacted by a nanosecond Nd:YAG laser beam in ambient air and distilled water. Measuring optical transmission of a He-Ne beam through the ablation region shows that the ablation rate in water is higher than that in ambient air. The results also show that an initial peak appears in the transmission signal which is an evidence for bubble formation in water. Analyzing the data is useful for monitoring the bubble formation in water and relatively estimating the ablation rate.

Mahdieh, M. H.; Akbari Jafarabadi, M.

2014-09-01

324

Absorption coefficient of aluminum near the critical point and the consequences on high-power nanosecond laser ablation  

SciTech Connect

During nanosecond laser ablation, the absorption coefficient determines the laser energy deposition in the target, the accurate knowledge of which near the material critical point is crucial for understanding the fundamental physics of high-power nanosecond laser ablation. In this letter, the absorption coefficient of aluminum near the critical point is calculated through the Drude model based on the measured electrical conductivity data, and its effect on laser ablation is investigated numerically using a heat transfer model. The result supports the experimental observations that phase explosion occurs for the ablation of aluminum by sufficiently intense laser pulses, and the model predicted phase explosion threshold is consistent with experimental measurements.

Wu Benxin; Shin, Yung C. [Center for Laser-based Manufacturing, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2006-09-11

325

The DCU laser ion source.  

PubMed

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 relation to the operation of a LIS are detailed. A range of laser power densities (I approximately 10(8)-10(11) W cm(-2)) and fluences (F=0.1-3.9 kJ cm(-2)) from a Q-switched ruby laser (full-width half-maximum pulse duration approximately 35 ns, lambda=694 nm) were used to generate a copper plasma. In "basic operating mode," laser generated plasma ions are electrostatically accelerated using a dc HV bias (5-18 kV). A traditional einzel electrostatic lens system is utilized to transport and collimate the extracted ion beam for detection via a Faraday cup. Peak currents of up to I approximately 600 microA for Cu(+) to Cu(3+) ions were recorded. The maximum collected charge reached 94 pC (Cu(2+)). Hydrodynamic simulations and ion probe diagnostics were used to study the plasma plume within the extraction gap. The system measured performance and electrodynamic simulations indicated that the use of a short field-free (L=48 mm) region results in rapid expansion of the injected ion beam in the drift tube. This severely limits the efficiency of the electrostatic lens system and consequently the sources performance. Simulations of ion beam dynamics in a "continuous einzel array" were performed and experimentally verified to counter the strong space-charge force present in the ion beam which results from plasma extraction close to the target surface. Ion beam acceleration and injection thus occur at "high pressure." In "enhanced operating mode," peak currents of 3.26 mA (Cu(2+)) were recorded. The collected currents of more highly charged ions (Cu(4+)-Cu(6+)) increased considerably in this mode of operation. PMID:20441334

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

2010-04-01

326

Effect of oblique force source induced by laser ablation on ultrasonic generation.  

PubMed

The effect of asymmetry caused by oblique line-shaped laser ablation on the generation of ultrasonic waves in metal, especially the effect of transverse component of the ablation force source on the ultrasonic waves is analyzed. Due to the oblique force source, the displacements of shear wave increase obviously by the enhanced shear force, the energy concentration area of longitudinal wave deflects to the small range centered on the incident direction while that of shear wave is approximately perpendicular to incident direction. In addition, surface wave enhances in the direction of transverse power flow. Furthermore, some ultrasonic characteristics under vortex laser ablation condition are inferred. PMID:24514978

Guo, Yuning; Yang, Dexing; Chang, Ying; Gao, Wei

2014-01-13

327

Ultrafast laser ablation and machining large-size structures on porcine bone.  

PubMed

When using ultrafast laser ablation in some orthopedic applications where precise cutting/drilling is required with minimal damage to collateral tissue, it is challenging to produce large-sized and deep holes using a tightly focused laser beam. The feasibility of producing deep, millimeter-size structures under different ablation strategies is investigated. X-ray computed microtomography was employed to analyze the morphology of these structures. Our results demonstrated the feasibility of producing holes with sizes required in clinical applications using concentric and helical ablation protocols. PMID:23884158

An, Ran; Khadar, Ghadeer W; Wilk, Emilia I; Emigh, Brent; Haugen, Harold K; Wohl, Gregory R; Dunlop, Brett; Anvari, Mehran; Hayward, Joseph E; Fang, Qiyin

2013-07-01

328

Resonance-enhanced multiphoton ionization spectroscopy of laser-ablated copper atoms  

NASA Astrophysics Data System (ADS)

Resonance-enhanced multiphoton ionization (REMPI) spectra of laser-ablated copper atoms entrained in a supersonic free jet expansion are reported. Depending on the ionization scheme employed, and the conditions under which the copper atoms are produced, very different spectra are produced, which are discussed. In some circumstances, high proportions of metastable atoms survive the ablation and expansion process and are clearly seen in the spectra. The spectroscopic transitions for the observed lines are identified, and it is noted that some caution is merited in the assumption that only ground state copper atoms are present following laser ablation.

Andrejeva, Anna; Harris, Joe P.; Wright, Timothy G.

2014-10-01

329

1D modelling of nanosecond laser ablation of copper samples in argon at P = 1 atm with a wavelength of 532 nm  

NASA Astrophysics Data System (ADS)

A one-dimensional model is developed for nanosecond laser ablation of a metal target (Cu) in a background gas (Ar) at any pressure. Simulations are performed with a 6 ns FWHM Gaussian laser pulse at 532 nm with a fluence of 11.3 J.cm-2. Heating, melting, evaporation, and condensation are considered to model the laser-target interaction. Expansion of the plume is investigated solving the Euler equations in a lagrangian formalism. Plasma formation is taken into account by computing the ionic species densities up to the second order of ionization in both the ablated material and the background gas. Such formation implies a strong laser-plasma interaction, assuming that the absorption phenomena are photoionization, electron-atom, and electron-ion inverse Bremsstrahlung. Radiative losses are supposed to be only described by electron-ion Bremsstrahlung. Preliminary results are presented and discussed.

Clair, Guillaume; L'Hermite, Daniel

2011-10-01

330

Laser ablation threshold dependence on pulse duration for fused silica and corneal tissues: experiments and modeling  

NASA Astrophysics Data System (ADS)

The surface ablation threshold fluence of fused silica and two porcine cornea layers, the epithelium and the stroma, is characterized as a function of the laser pulse duration in the range of 100 fs-5 ps for a wavelength of 800 nm (Ti:sapphire laser system). The plateaulike region observed between 100 fs and 1 ps for the corneal layers indicates that for use in laser surgery, laser pulse durations chosen within this range should be practically equivalent. Our model predicts that the ablation threshold will decrease rapidly for pulse durations in the low end of the femtosecond regime.

Giguère, Dominic; Olivié, Gilles; Vidal, François; Toetsch, Stéphanie; Girard, Guillaume; Ozaki, Tsuneyuki; Kieffer, Jean-Claude; Nada, Ossama; Brunette, Isabelle

2007-06-01

331

Tribological properties of polymer nanohybrids containing gold nanoparticles obtained by laser ablation.  

PubMed

We have studied polystyrene (PS)+Au particles nanohybrids. Approximately spherical gold nanoparticles with the average diameter of 15 nm were obtained by laser ablation in a liquid environment. Thus any chemical residue on the particles was eliminated. Focused ion beam (FIB) milling plus scanning electron microscopy (SEM) observation show that Au particles are fairly well dispersed inside the polymer matrix, better than when PS is simply dissolved in a nanoparticle solution. The Au particles concentration as low as 0.15 wt% results in dramatic changes in tribological properties, namely dynamic friction and pin-on-disk wear. Both wear and dynamic friction results are explained in terms of high brittleness of PS, abrasion of Au particles against a ceramic indenter, and also effects of density of filler particles in the matrix on tribological properties. Effects of varying normal load on friction are small. PMID:22755118

Olea-Mejía, Oscar; Brostow, Witold; Escobar-Alarcón, Luis; Vigueras-Santiago, Enrique

2012-03-01

332

Preferential vaporization and plasma shielding during nano-second laser ablation  

NASA Astrophysics Data System (ADS)

Preferential removal of components from mixed material targets and plasma shielding are studied by using inductively coupled plasma-atomic emission spectrometry (ICP-AES) during UV nano-second laser ablation. The ICP emission intensity for Cu and Zn during ablation of brass samples varies versus laser power density. A model using thermal evaporation and inverse Bremsstrahlung processes is presented. The model shows that plasma shielding occurs at approximately 0.3 GW/cm 2, in agreement with experimental data for change in the mass ablation rate. The good agreement of model and experimental data suggest that thermal effects are important during nano-second laser ablation for power density less than 0.3 GW/cm 2.

Mao, Xianglei; Chan, Wing-Tat; Caetano, Manuel; Shannon, Mark A.; Russo, Richard E.

1996-04-01

333

Comparison of transcatheter laser and direct-current shock ablation of endocardium near tricuspid anulus  

NASA Astrophysics Data System (ADS)

Forty to eighty percent of the patients with accessory pathways (APs) manifest themselves by tachyarrhythmias. Many of these patients needed either life-long medical therapy or surgery. In order to avoid the discomfort and expenses in surgical procedures, closed chest percutaneous catheter ablation of APs became a potentially desirable therapeutic approach. Many investigations indicated that ablation of right APs by transcatheter direct current (dc) shock could cause life-threatening arrhythmias, right coronary arterical (RCA) spasm, etc. With the development of transcatheter laser technique, it has been used in drug-incurable arrhythmias. The results show that laser ablation is much safer than surgery and electric shock therapy. The purpose of this study is to explore the effectiveness, advantages, and complications with transcatheter Nd:YAG laser and dc shock in the ablation of right atrioventricular accessory pathways in the atrium near the tricuspid annulus (TA) in 20 dogs.

Zhang, Yu-Zhen; Wang, Shi-Wen; Li, Junheng

1993-03-01

334

Ablation of ionic crystals induced by capillary-discharge XUV laser  

NASA Astrophysics Data System (ADS)

Single crystals of two fluorides (LiF and CaF2) and a tungstate (PbWO4) were irradiated by nanosecond pulses of 46.9- nm radiation provided by 10-Hz capillary-discharge Ne-like Ar laser (CDL). The damage threshold was determined in LiF using the CDL beam focused by a Sc/Si multilayer-coated spherical mirror. Irradiated samples have been investigated by Nomarski (DIC - Differential Interference Contrast) microscopy and optical (WLI - white light intereferometry) profiler. After an exposure by a certain number of CDL pulses, an ablation rate can be calculated from WLI measured depth of the crater created by the XUV ablation. Potential use of XUV ablation of ionic crystals in pulsed laser deposition (PLD) of thin layers of such a particular material, which is difficult to ablate by conventional UV-Vis- NIR lasers, is discussed in this contribution.

Pira, Peter; Burian, Tomáš; Vyšín, Ludék; Chalupský, Jaromír; Lan?ok, Ján; Wild, Jan; St?ižík, Michal; Zelinger, Zden?k; Rocca, Jorge J.; Juha, Libor

2011-06-01

335

Spectroscopic study on the enhanced excitation of an electron cyclotron resonance nitrogen plasma by pulsed laser ablation of an aluminum target.  

PubMed

The influence of pulsed laser ablation of an aluminum target on the nitrogen plasma produced by electron cyclotron resonance (ECR) microwave discharge has been studied by optical emission spectroscopy (OES) with time and space resolution. The continuous wave (CW) feature of the optical emissions from the ECR nitrogen plasma turns to vary with time and space due to pulsed laser ablation and the expansion of the ablation-induced aluminum plume in the nitrogen plasma. The optical emissions from the nitrogen plasma increase significantly and the emission intensity of nitrogen molecular ions is observed to be more than 20 times higher with the target being ablated in comparison to the case without target ablation. The comparison of the optical emissions from the nitrogen plasma with those from the aluminum plume indicates that the excitation enhancement of the nitrogen plasma occurs in the region where the aluminum plume is expanding, revealing that the expansion of the aluminum plume leads to the excitation enhancement of the nitrogen plasma. Relevant mechanisms responsible for the excitation enhancement of the nitrogen plasma through hybrid processes of ECR microwave discharge and pulsed laser ablation are also discussed. PMID:19007469

Tang, J Y; Zhang, W; Sun, J; Xu, N; Ge, C; Wu, J D

2008-11-01

336

Transmission of 1064 nm laser radiation during ablation with an ultra-short pulse laser (USPL) system  

NASA Astrophysics Data System (ADS)

During ablation of oral hard tissue with an USPL system a small amount of the incident laser power does not contribute to the ablation process and is being transmitted. Partial transmission of ultra-short laser pulses could potentially affect the dental pulp. The aim of this study was to assess the transmission during ablation and to deduce possible risks for the patient. The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz and an average power of 9 W were chosen to achieve high ablation efficiency. A scanner system created square cavities with an edge length of 1 mm. Transmission during ablation of mammoth ivory and dentin slices with a thickness of 2 mm and 5 mm was measured with a power meter, placed directly beyond the samples. Effects on subjacent blood were observed by ablating specimens placed in contact to pork blood. In a separate measurement the temperature increase during ablation was monitored using an infrared camera. The influence of transmission was assessed by tuning down the laser to the corresponding power and then directly irradiating the blood. Transmission during ablation of 2 mm specimens was about 7.7% (ivory) and 9.6% (dentin) of the incident laser power. Ablation of specimens directly in contact to blood caused coagulation at longer irradiation times (t~18s). Direct irradiation of blood with the transmitted power provoked bubbling and smoke formation. Temperature measurements identified heat generation as the main reason for the observed coagulation.

Schelle, Florian; Meister, Jörg; Oehme, Bernd; Frentzen, Matthias

2012-01-01

337

Surface ablation of PLLA induced by KrF excimer laser  

NASA Astrophysics Data System (ADS)

The surface characterization of PLLA (poly-L-lactic-acid) and its ablation due to excimer laser treatment is introduced in this paper. The main focus is to determine surface wettability and morphology changes in combination with changes of surface chemistry. The ablation loss and the determination of ablation threshold were used to study the biopolymer stability when treated to different laser fluences and pulse counts. The surface polarity was estimated using goniometry. AFM (atomic force microscopy) was used to determine the polymer surface morphology and roughness. The excimer laser has a strong effect on the polymer ablation. The thickness loss is strongly dependent on the laser fluence and number of pulses. For the fluences up to 30 mJ cm-2 and 6000 pulses achieved ablation about 5 ?m. The glass transition temperature and melting point were determined for the pristine and laser treated films. The increasing pulsed laser fluence leads to the major changes in roughness and morphology. The surface chemistry depends strongly on number of laser pulses.

Slepi?ka, P.; Michaljani?ová, I.; Sajdl, P.; Fitl, P.; Švor?ík, V.

2013-10-01

338

Laser structuring of metallic mold inserts by using ?s, ns, and ps-laser ablation  

NASA Astrophysics Data System (ADS)

Bio-inspired surfaces targeting functional characteristics such as anti-reflectivity, self-cleaning effects or a drag reduction are of significant interest to industry. In this feasibility study, process chains for the mass production of so-called shark skin structured surfaces are investigated. Due to their drag reduction properties, such bio-inspired surfaces are of relevance to a number of applications in which particular aqua- and aerodynamic characteristics are required. The design of the shark skin structure relies on a bio-mimetic analytical model to generate the 3D surface model necessary to achieve the targeted surface functionality. The process chains presented combine laser ablation as a method for micro structuring masters for high throughput replication employing injection molding. In particular, three different process chains that rely on micro second (?s), nano second (ns) and pico second (ps) laser ablation systems to pattern mold inserts were investigated. Then, these inserts were integrated into a tool for micro injection molding and replication trials were carried out. The results show that all three laser sources can be utilized to create this kind of micro cavities. This research indicates that these micro structures can be replicated successfully, but further work is required to optimize the replication and laser structuring process.

Scholz, Steffen G.; Kolew, Alexander; Griffiths, Christian

2012-03-01

339

High Spatial Resolution Fe isotope analysis by femtosecond Laser Ablation  

NASA Astrophysics Data System (ADS)

In-situ isotopic analysis of geological samples has shown the importance of retrieving isotopic information on the micron scale from isolated mineral grains in complex samples or those that contain multiple isotopic components. Recent studies of magnetite, hematite, and pyrite using femtosecond laser ablation (fs-LA) report sampled volumes (Vs) down to ~6×103?m3, with internal and external reproducibility of ~0.12‰ (2SE) and ~0.20‰ (2SD) respectively [1-3]. We have improved the spatial resolution of fs-LA measurements by a factor of ~10 with the same analytical uncertainty as that cited above. These improvements were made by: (1) using a more efficient ablation cell and (2) improving the electronics of the Faraday detectors. Two cell geometries manufactured by Photon Machines (San Diego, CA, USA) have been studied for aerosol Particle Size Distribution (PSD) and Fe isotope composition under He gas flows of ~0.6L.min-1: the Frame cell (~20cc, ~2s washout time) and the two volumes HelEx cell (inner volume ~7cc, ~0.7s washout time). The measured PSDs are independent of the substrate (hematite, magnetite, pyrite, pyrrhotite, and siderite) or the laser wavelength (?=198 and 263nm). The Frame cell produced a monomodal PSD, centered on an aerodynamic diameter (da) of ~0.25?m, whereas the HelEx cell produced a bi-modal PSD with peaks at da<0.056?m and 0.14?m. The finer aerosols produced by the HelEx cell are interpreted to reflect its faster extraction, limiting collisions and agglomeration, as well as inhomogeneous transport losses and attendant incomplete ionization in the plasma torch. LA-MC-ICP-MS analyses of magnetite using the Frame cell (Vs~1.5×104?m3, 40×10s on peak integrations) yield internal and external precisions of 0.12‰ (2SE) and 0.25‰ (2SD, n=61) respectively [1]. In contrast, the HelEx cell (Vs~5.5×103mm3, 40×5s on peak integrations) provides internal and external precisions of 0.10‰ (2SE) and 0.20‰ (2SD, n=115). A new generation of high-ohm resistors boards (IsotopX, Middlewich, UK) for Faraday detectors has been evaluated, using a 1010ohm resistor for 56Fe and 1011ohm for 54Fe. The new setup improved internal precision for conventional analysis by ~33%, and precision is independent of the on-peak integration time between 1 and 10s. The same improvement is noted for fs-LA using the HelEx cell, where spatial resolution entirely depends on the acquisition time. Hence, we were able to reduce Vs to ~6×102?m3 by performing analyses over only 50s (1s on peak integration), which still yields internal and external precisions of 0.11‰ (2SE) and 0.28‰ (2SD, n=28). In conclusion, and considering similar internal and external precisions, reducing the particle residence time in the ablation cell improves the spatial resolution by a factor of ~3. On the other hand, being able to integrate the signal over only 1s cycles improves the spatial resolution by a factor of ~9 with the same precisions as the currently published data. 1. Czaja, A.D., et al., Earth and Planetary Science Letters, 2013. 363: p. 192-203. 2. Steinhoefel, G., et al., Geochimica et Cosmochimica Acta, 2009. 73(18): p. 5343-5360. 3. Yoshiya, K., et al., Precambrian Research, 2012. 212-213: p. 169-193.

Johnson, C.; Beard, B. L.; d'Abzac, F.

2013-12-01

340

Fully Automated Laser Ablation Liquid Capture Sample Analysis using NanoElectrospray Ionization Mass Spectrometry  

SciTech Connect

RATIONALE: Laser ablation provides for the possibility of sampling a large variety of surfaces with high spatial resolution. This type of sampling when employed in conjunction with liquid capture followed by nanoelectrospray ionization provides the opportunity for sensitive and prolonged interrogation of samples by mass spectrometry as well as the ability to analyze surfaces not amenable to direct liquid extraction. METHODS: A fully automated, reflection geometry, laser ablation liquid capture spot sampling system was achieved by incorporating appropriate laser fiber optics and a focusing lens into a commercially available, liquid extraction surface analysis (LESA ) ready Advion TriVersa NanoMate system. RESULTS: Under optimized conditions about 10% of laser ablated material could be captured in a droplet positioned vertically over the ablation region using the NanoMate robot controlled pipette. The sampling spot size area with this laser ablation liquid capture surface analysis (LA/LCSA) mode of operation (typically about 120 m x 160 m) was approximately 50 times smaller than that achievable by direct liquid extraction using LESA (ca. 1 mm diameter liquid extraction spot). The set-up was successfully applied for the analysis of ink on glass and paper as well as the endogenous components in Alstroemeria Yellow King flower petals. In a second mode of operation with a comparable sampling spot size, termed laser ablation/LESA , the laser system was used to drill through, penetrate, or otherwise expose material beneath a solvent resistant surface. Once drilled, LESA was effective in sampling soluble material exposed at that location on the surface. CONCLUSIONS: Incorporating the capability for different laser ablation liquid capture spot sampling modes of operation into a LESA ready Advion TriVersa NanoMate enhanced the spot sampling spatial resolution of this device and broadened the surface types amenable to analysis to include absorbent and solvent resistant materials.

Lorenz, Matthias [ORNL] [ORNL; Ovchinnikova, Olga S [ORNL] [ORNL; Van Berkel, Gary J [ORNL] [ORNL

2014-01-01

341

Effects of laser ablated silver nanoparticles on Lemna minor.  

PubMed

The present study investigates and models the effect of laser ablated silver nanoparticles (AgNPs) on the development of the aquatic macrophyte Lemna minor. Toxic effects of five different AgNP concentrations (8, 16, 32, 96 and 128 ?g L(-1)) on L. minor were recorded over seven days under simulated natural conditions. Biosorption of AgNPs by L. minor was modeled using four sorption isotherms, and the sorption behavior was found to agree most closely with the Langmuir-Freundlich model (R(2)=0.997). While toxic effects of AgNPs could be observed in all models and concentrations, the greatest increase in toxicity was in the 8-32 ?g L(-1) range. Dry weight- and frond number-based inhibition experiments suggest that growth inhibition does not necessarily scale with AgNP concentration, and that slight fluctuations in inhibition rates exist over certain concentration ranges. Very close fits (R(2)=0.999) were obtained for all removal models, suggesting that the fluctuations are not caused by experimental variation. In addition, L. minor was found to be a successful bioremediation agent for AgNPs, and displayed higher removal rates for increasing AgNP doses. FT-IR spectroscopy suggests that carbonyl groups are involved in AgNP remediation. PMID:24529395

Üçüncü, Esra; Özkan, Alper D; Kur?ungöz, Canan; Ülger, Zeynep E; Ölmez, Tolga T; Tekinay, Turgay; Ortaç, Bülend; Tunca, Evren

2014-08-01

342

Silver Nanoparticles Obtained by Laser Ablation Using Different Stabilizers  

NASA Astrophysics Data System (ADS)

We have synthesized silver nanoparticles by laser ablation in water using three stabilizers: hexadecyltrimethylammonium (CTAB) surfactant, polyamidoamine dendrimer second generation (PAMAM 2G) and polyamidoamine dendrimer fourth generation (PAMAM 4G) at different concentrations. We obtained spherical nanoparticles with narrow size distributions and average sizes ranging from 6 to 20 nm depending on the type of stabilizer and its concentration. For all cases the highest stabilizer concentration yielded the lowest average particle size; 15.5, 9.5, and 5.6 nm for CTAB, PAMAM 2G and PAMAM 4G respectively. We have also studied the stability of the nanoparticle colloids over a period of 30 days. Only the colloids of CTAB 10-3 M, all the concentrations of PAMAM 4G and pure water were stable after this time. This is explained in terms of steric hindrance of the stabilizer molecules and particle charge from Zeta potential measurements. All the results from transmission electron microscopy correlate well with those observed from the ultraviolet and visible spectra of each sample in terms of absorbance, peak width and peak maximum.

Olea-Mejía, Oscar; Pote-Orozco, Héctor; Camacho-López, Marco A.; Olea-Cardoso, Oscar; López-Castañares, Rafael; Vilchis-Néstor, Alfredo R.

2013-11-01

343

Compact And Robust Laser Impulse Measurement Device, With Ultrashort Pulse Laser Ablation Results  

SciTech Connect

An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of {approx}7 ns, {approx}500 ps, and {approx}500 fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. These parameters should be carefully controlled and held constant during a series of measurements. The impulse imparted by ablation due to laser filaments in air was also explored.

Kremeyer, Kevin; Lapeyre, John; Hamann, Steven [Physics, Materials, and Applied Mathematics Research, L.L.C. PM and AM Research in Collaboration with AFRL 1665 E. 18th Street, Suite 112 Tucson, AZ, 85719 (United States)

2008-04-28

344

Standard addition method for laser ablation ICPMS using a spinning platform.  

PubMed

A method has been developed for the fast and easy determination of Pb, Sr, Ba, Ni, Cu, and Zn, which are of geological and environmental interest, in solid samples by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) using a spinning sample platform. The platform, containing a sample and a standard, is spun during the ablation, allowing the quasi-simultaneous ablation of both materials. The aerosols resulting from the ablation of sample and standard were mixed in the ablation cell allowing quantification of analytes by standard additions. The proportion of standard versus sample of the mixing can be increased by performing the ablation further from the axis of rotation. The ablated masses have been determined using a new strategy based on isotope dilution analysis. This spinning laser ablation method has been applied to the Allende meteorite and four powdered standard reference materials (SRMs) fused in lithium borate glasses: two sediments as well as a soil and a rock material. SRM 612 (Trace Elements in Glass) was also analyzed despite having a matrix slightly different from the glass standard obtained by lithium borate fusion. The deviation from the certified values was found to be less than 15% for most of the mass fractions for all the elements and samples studied, with an average precision of 10%. These results demonstrate the validity of the proposed method for the direct and fast analysis of solid samples of different matrixes by standard additions, using a single standard sample. PMID:23418996

Claverie, Fanny; Malherbe, Julien; Bier, Naomi; Molloy, John L; Long, Stephen E

2013-04-01

345

Acoustic spectroscopy of Er:YAG laser ablation of skin: first results  

Microsoft Academic Search

We investigated the acoustic signal of Er:YAG laser ablation in a gaseous environment. The high absorption coefficient of water at the laser wavelength of 2.94 micrometer leads to a small penetration depth of the Er:YAG laser pulses into tissue. The deposition of laser energy in a thin layer at the tissue surface causes a rapid evaporization of tissue water. The

Kester Nahen; Alfred Vogel

1998-01-01

346

Major and trace analysis of basaltic glasses by laser-ablation ICP-MS  

NASA Astrophysics Data System (ADS)

Chemical analysis by laser-ablation ICP-MS can determine a large number of trace elements with a precision approaching traditional whole-rock analysis, but on a scale approaching that achieved by the electron microprobe. These characteristics make it a particularly attractive method for the analysis of volcanic glasses, but at present little is known about systematic errors, especially those from matrix effects. Here we investigate the precision and accuracy of LA-ICP-MS analysis of basaltic glasses for 60 elements, including rare earth elements (REE), large ion lithophile elements (LILE), high field strength elements (HFSE), the first row transition elements (FRTE), as well as less commonly analyzed elements such as Li, Be, Ge, Ga, W, Mo, As, Sb, Sn, Se, Ag, Tl, Bi, Cd and In. The rate of signal decline during ablation was found to vary systematically with the electronic structure of the element, in both calibration material (NIST SRM 612) and unknowns (natural basaltic glass VG-2 and vitrified basalt BCR-2G). These observations allow optimal analytical conditions with the available instrumentation and standards to be established. Analyses of VG-2 and seven of the MPI-DING vitrified rocks, commonly used as secondary standards, obtained under these conditions, are presented.

Jenner, Frances E.; O'Neill, Hugh St. C.

2012-03-01

347

The role of laser wavelength on plasma generation and expansion of ablation plumes in air  

NASA Astrophysics Data System (ADS)

We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

2013-04-01

348

Laser ablation methods for analysis of urinary calculi: Comparison study based on calibration pellets  

NASA Astrophysics Data System (ADS)

Methods based on laser ablation, such as Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass/Optical Emission Spectrometry (LA-ICP-MS/OES) are particularly suitable for urinary calculi bulk and micro analysis. Investigation of spatial distribution of matrix and trace elements can help to explain their emergence and growth. However, quantification is still very problematic and these methods are often used only for qualitative elemental mapping. There are no commercially available standards, which would correspond to the urinary calculi matrix. Internal standardization is also difficult, mainly due to different crystalline phases in one kidney stone. The aim of this study is to demonstrate the calibration capabilities and examine the limitations of laser ablation based techniques. Calibration pellets were prepared from powdered human urinary calculi with phosphate, oxalate and urate matrix. For this comparative study, the most frequently used laser-ablation based analytical techniques were chosen, such as LIBS and LA-ICP-MS. Moreover, some alternative techniques such as simultaneous LIBS-LA-ICP-OES and laser ablation LA-LIBS were also utilized.

Št?pánková, K.; Novotný, K.; Vašinová Galiová, M.; Kanický, V.; Kaiser, J.; Hahn, D. W.

2013-03-01

349

Analysis and removal of ITER relevant materials and deposits by laser ablation  

NASA Astrophysics Data System (ADS)

The analysis of the deposition of eroded wall material on the plasma-facing materials in fusion devices is one of the crucial issues to maintain the plasma performance and to fulfill safety requirements with respect to tritium retention by co-deposition. Laser ablation with minimal damage to the plasma facing material is a promising method for in situ monitoring and removal of the deposition, especially for plasma-shadowed areas which are difficult to reach by other cleaning methods like plasma discharge. It requires the information of ablation process and the ablation threshold for quantitative analysis and effective removal of the different deposits. This paper presents systemic laboratory experimental analysis of the behavior of the ITER relevant materials, graphite, tungsten, aluminum (as a substitution of beryllium) and mixed deposits ablated by a Nd:YAG laser (1064 nm) with different energy densities (1-27 J/cm2, power density 0.3-3.9 GW/cm2). The mixed deposits consisted of W-Al-C layer were deposited on W substrate by magnetron sputtering and arc plasma deposition. The aim was to select the proper parameters for the quantitative analysis and for laser removal of the deposits by investigating the ablation efficiency and ablation threshold for the bulk materials and deposits. The comparison of the ablation and saturation energy thresholds for pure and mixed materials shows that the ablation threshold of the mixed layer depends on the concentration of the components. We propose laser induced breakdown spectroscopy for determination of the elemental composition of deposits and then we select the laser parameters for the layer removal. Comparison of quantitative analysis results from laboratory to that from TEXTOR shows reasonable agreements. The dependence of the spectra on plasma parameters and ambient gas pressure is investigated.

Xiao, Qingmei; Huber, Alexander; Philipps, Volker; Sergienko, Gennady; Gierse, Niels; Mertens, Philippe; Hai, Ran; Ding, Hongbin

2014-12-01

350

Tailored ablation processing of advanced biomedical hydroxyapatite by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

The micromachining of hydroxyapatite (HAp) is highly important for orthopedics and dentistry, since human bone and teeth consist mainly of HAp. We demonstrate ultrashort Ti:sapphire laser ablation of HAp, using pulse-widths of 50 fs, 500 fs, and 2 ps at a wavelength of 820 nm and at 1 kpps. The crucial medical issue is to preserve the chemical properties of the machined (ablated) surface. If the chemical properties of HAp change, the human bone or tooth cannot re-grow after laser processing. Using X-ray photoelectron spectroscopy, we observe chemical properties of HAp ablated in air. The HAp is ablated at laser fluences of 3.2 J/cm2 (6.4×1013 W/cm2 at 50 fs), 3.3 J/cm2 (6.6×1012 W/cm2 at 500 fs), and 9.6 J/cm2 (4.8×1012 W/cm2 at 2 ps), respectively. As a result it is found that the ablated surface is unchanged after laser ablation over the pulse-width range used in this experiment.

Ozono, K.; Obara, M.

351

Comparison between geometrically focused pulses versus filaments in femtosecond laser ablation of steel and titanium alloys  

NASA Astrophysics Data System (ADS)

Kerr self-focusing of high-power ultrashort laser pulses in atmosphere may result in a structure or structures of high intensity that can propagate over long distances with little divergence. Filamentation has garnered significant interest in the nonlinear optics community due to its unique properties. Salient features of filaments include a central region of intense laser power (greater than the ionization threshold of the propagation medium) and a low temperature plasma column that lasts up to nanoseconds in duration after the passage of the laser pulse. Steel and titanium samples are ablated by filaments and by sharply focused sub-picosecond laser pulses. We then performed metrology on the samples to compare the ablation features in addition to modeling of the plasma ablation process. Ablation with filaments leads to a wider range of material responses as compared to ablation with sharply focused pulse. This results in potential complications for applications of filament ablation that depends on the rate of material removal and spectroscopic analysis.

Valenzuela, Anthony; Munson, Chase; Porwitzky, Andrew; Weidman, Matthew; Richardson, Martin

2014-08-01

352

Nd:YAG laser ablation characteristics of thin CIGS solar cell films  

NASA Astrophysics Data System (ADS)

This work reports that the ablation characteristics of thin CuIn1- x Ga x Se2 (CIGS) solar cell film differ significantly with elemental composition and laser pulse energy. From in situ shadowgraphs measured during Nd:YAG laser (1,064 nm) irradiation of CIGS films and crater morphologies, it was found that strong surface evaporation is dominant for low Ga concentration films of which band gap is well below the photon energy. As the band gap of CIGS film becomes close to or over the laser photon energy due to increased Ga content, surface absorption diminishes and at low laser energy, laser heating of the film plays an important role. It is demonstrated that for the CIGS films with Ga/(Ga + In) ratio being approximately over 0.2, the laser irradiation leads to solid phase removal of the film due to thermomechanical fracture at low laser energy but to ablative evaporation at elevated energy.

Lee, S. H.; Kim, C. K.; In, J. H.; Kim, D. S.; Ham, H. J.; Jeong, S. H.

2013-12-01

353

The effect of laser wavelength on the ablation rate of carbon  

NASA Astrophysics Data System (ADS)

The ablation of graphite is studied as a function of laser fluence for 355, 532 and 1,064 nm wavelength generated by a nanosecond Nd:YAG laser. It has been found that in the case of lower wavelengths, the transition from the thermal ablation to the phase explosion takes place at lower laser fluences. The change of crater shape due to the effect of deep drilling in the proximity of the phase explosion threshold was observed. The calculations of plasma radiation flux to the target surface were made, and the considerable increase of absorbed energy density was found in the case of 355 nm wavelength.

Hoffman, J.; Chrzanowska, J.; Kucharski, S.; Moscicki, T.; Mihailescu, I. N.; Ristoscu, C.; Szymanski, Z.

2014-10-01

354

A matrix isolation FTIR investigation of laser-ablated uranium oxide in argon and nitrogen matrices  

Microsoft Academic Search

Uranium oxide was laser-ablated using the second harmonic of a Nd : YAG laser, and the products studied after trapping them\\u000a in Ar and N2 matrices. The species obtained in the Ar matrix were UO, UO2 and UO3, which represent the primary products of laser ablation. Charge transfer complexes, (UO\\u000a 2\\u000a +\\u000a ) (O\\u000a 2\\u000a ?\\u000a ) and (UO\\u000a 2

K Sankaran; K Sundararajan; K S Viswanathan

1999-01-01

355

Kinetic model for ion pressure perturbations in inhomogeneous laser-matter interactions  

SciTech Connect

A Boltzmann-Vlasov Fokker-Planck model is used to characterize the evolution of ion pressure perturbations from nonuniform laser deposition in a plasma slab. It is found that significant reduction and smoothing of ion pressure perturbations from nonuniform optically smoothed single beam laser deposition can be achieved on hydrodynamic time scales over a range of scale sizes. In addition, it is observed that the ion Fokker-Planck model predicts more smoothing of the ion pressure perturbations from the critical to ablation surface than the ion fluid model.

Keskinen, M. J. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2010-05-15

356

Morphology of femtosecond-laser-ablated borosilicate glass surfaces Adela Ben-Yakara)  

E-print Network

Morphology of femtosecond-laser-ablated borosilicate glass surfaces Adela Ben-Yakara) and Robert L August 2003 We study the morphology of borosilicate glass surface machined by femtosecond laser pulses of multiple overlapping craters leads to surface roughness. We carried out experiments on borosilicate glass 1

Byer, Robert L.

357

Morphology of Femtosecond Laser Ablated Borosilicate Glass Surfaces Adela Ben-Yakar and Robert L. Byer  

E-print Network

Morphology of Femtosecond Laser Ablated Borosilicate Glass Surfaces Adela Ben-Yakar and Robert L the morphology of borosilicate glass surface machined by femtosecond laser pulses. Our observations show have been used to machine microchannels in transparent glasses such as borosilicate glass and fused

Harkin, Anthony

358

Characteristics of Plasma Shock Waves Generated in the Pulsed Laser Ablation Process  

Microsoft Academic Search

We modify the Sedov theory to describe plasma shock waves generated in a pulsed laser ablating process. We also study the propagation characteristics of plasma shock waves during the preparation process of functional thin films deposited by a pulsed laser. In particular, we discuss in detail the temporal behaviour of energy causing the difference of the propagation characteristics between the

Zhi-Hua Li; Duan-Ming Zhang; Bo-Ming Yu; Li Guan

2002-01-01

359

Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media  

Microsoft Academic Search

We studied the effects of the surrounding liquid environment on the size and optical properties of silver nanoparticles prepared by laser ablation by a pulsed Nd:YAG laser operated at 1064 nm. The silver targets used were kept in acetone, water and ethanol. TEM observations and optical extinction were employed for characterization of particle size, shape and optical properties, respectively. Nano

R. M. Tilaki; A. Iraji Zad; S. M. Mahdavi

2006-01-01

360

Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media  

Microsoft Academic Search

We studied the effects of the surrounding liquid environment on the size and optical properties of silver nanoparticles prepared by laser ablation by a pulsed Nd:YAG laser operated at 1064 nm. The silver targets used were kept in acetone, water and ethanol. TEM observations and optical extinction were employed for characterization of particle size, shape and optical properties, respectively. Nano silver

R. M. Tilaki; A. Iraji zad; S. M. Mahdavi

2006-01-01

361

Laser ablation threshold dependence on pulse duration for fused silica and corneal tissues: experiments and modeling  

Microsoft Academic Search

The surface ablation threshold fluence of fused silica and two porcine cornea layers, the epithelium and the stroma, is characterized as a function of the laser pulse duration in the range of 100 fs-5 ps for a wavelength of 800 nm (Ti:sapphire laser system). The plateaulike region observed between 100 fs and 1 ps for the corneal layers indicates that

Dominic Giguère; Gilles Olivié; François Vidal; Stéphanie Toetsch; Guillaume Girard; Tsuneyuki Ozaki; Jean-Claude Kieffer; Ossama Nada; Isabelle Brunette

2007-01-01

362

Experimental investigation on spectral-energy efficiency of femtosecond laser ablation of metals  

SciTech Connect

Results of investigation on spectral-energy thresholds, rates, and mass flow rates of laser ablation of structural materials (Cu, Ti, Zr, Nb, Mo) of high-energy photonics are presented. The data were obtained by means of an experimental diagnostic module developed for study of multifactor interaction processes between UV-near IR femtosecond laser pulse radiation and condensed media in vacuum.

Loktionov, E. Yu., E-mail: stcpe@bmstu.ru [Bauman Moscow State Technical University (Russian Federation); Ovchinnikov, A. V. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation); Protasov, Yu. Yu. [Bauman Moscow State Technical University (Russian Federation); Sitnikov, D. S. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2011-12-15

363

Dentin ablation-rate measurements in endodontics witj HF and CO2 laser radiation  

NASA Astrophysics Data System (ADS)

Recent studies focused on the ability of the laser light to enlarge the root canal during the endodontic therapy. The aim of this research is the experimental and theoretical study of the ablation rate of two infrared laser wavelengths on dentin. Thirty freshly extracted human teeth were longitudinally sectioned at thicknesses ranged from 0.5 to 2 mm, and irradiated on the root canal dentin. The measured ablation rates in dentinal wall of the root canal showed that the HF laser at 2.9 micrometer can more effectively penetrate into the tissue, whereas the carbon dioxide laser at 10.6 micrometer leads to high thermal damage of the ablation crater surroundings.

Makropoulou, Mersini I.; Serafetinides, Alexander A.; Khabbaz, Marouan; Sykaras, Sotirios; Tsikrikas, G. N.

1996-01-01

364

A theoretical model of the femtosecond laser ablation of semiconductors considering inverse bremsstrahlung absorption  

NASA Astrophysics Data System (ADS)

The mechanism of the femtosecond laser ablation of semiconductors is investigated. The collision process of free electrons in a conduction band is depicted by the test particle method, and a theoretical model of nonequilibrium electron transport on the femtosecond timescale is proposed based on the Fokker—Planck equation. This model considers the impact of inverse bremsstrahlung on the laser absorption coefficient, and gives the expressions of electron drift and diffusion coefficients in the presence of screened Coulomb potential. Numerical simulations are conducted to obtain the nonequilibrium distribution function of the electrons. The femtosecond laser ablation thresholds are then calculated accordingly, and the results are in good agreement with the experimental results. This is followed by a discussion on the impact of laser parameters on the ablation of semiconductors.

Xiaohui, Lin; Chibin, Zhang; Weisong, Ren; Shuyun, Jiang; Quanhui, Ouyang

2012-04-01

365

Models For Laser Ablation Mass Removal And Impulse Generation In Vacuum  

SciTech Connect

To the present day, literature efforts at modeling laser propulsion impulse often used empirical models. Recently, a simple physical approach was demonstrated to be effective for predicting many practical properties of laser ablative impulse generation under vacuum. The model used photochemical mass removal and energy conservation to predict parameters such as the peak momentum coupling coefficient, the optimal fluence position at which this maximum is reached, and various critical properties related to the laser ablation threshold. Although the current model understanding is not complete, improvements in the treatment of mass removal and ambient pressure are expected to allow this type of model to be broadly applicable to many diverse applications using laser ablation impulse generation. In this paper, we also introduce an alternative formulation of the model incorporating photothermal mass removal. Implications and limitations of the model formulation in its initial stage of development are discussed, particularly concerning critical fluence effects and directions for improvement.

Sinko, John E. [Micro-Nano Global Center of Excellence, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603 (Japan); Gregory, Don A. [Department o Physics, University of Alabama in Huntsville, OB-201B John Wright Dr., Huntsville, AL 35899 (United States)

2010-05-06

366

Time-resolved study of back side ablated molybdenum thin films by ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

Ultrashort laser pulses are used to ablate a thin molybdenum layer from glass by irradiating the metal film through the transparent substrate. The trajectories of ablated molybdenum fragments are recorded using a shadowgraphic setup with a time resolution in the nanosecond range. In addition, the shape of collected molybdenum fragments is examined as a function of applied fluence. It is confirmed that in a fluence regime close to the ablation threshold one single disc is ablated as a whole and its velocity is determined in the order of 50 ms-1. In a second fluence regime, partial melting at the center of the disc is found and small melt droplets are recorded on their flight. Mo fragments ablated in this regime feature a ring-like structure with a brittle fracture at the outer and a molten appearance at the inner edge.

Bartl, Dominik; Michalowski, Andreas; Hafner, Margit; Letsch, Andreas; Nolte, Stefan; Tünnermann, Andreas

2013-01-01

367

Femtosecond laser ablation of dielectric materials in the optical breakdown regime: Expansion of a transparent shell  

NASA Astrophysics Data System (ADS)

Phase transition pathways of matter upon ablation with ultrashort laser pulses have been considered to be understood long-since for metals and semiconductors. We provide evidence that also certain dielectrics follow the same pathway, even at high pulse energies triggering optical breakdown. Employing femtosecond microscopy, we observe a characteristic ring pattern within the ablating region that dynamically changes for increasing time delays between pump and probe pulse. These transient Newton rings are related to optical interference of the probe beam reflected at the front surface of the ablating layer with the reflection at the interface of the non-ablating substrate. Analysis of the ring structure shows that the ablation mechanism is initiated by a rarefaction wave leading within a few tens of picoseconds to the formation of a transparent thin shell of reduced density and refractive index, featuring optically sharp interfaces. The shell expands and eventually detaches from the solid material at delays of the order of 100 ps.

Garcia-Lechuga, M.; Siegel, J.; Hernandez-Rueda, J.; Solis, J.

2014-09-01

368

Femtosecond laser corneal surgery with in situ determination of the laser attenuation and ablation threshold by second harmonic generation  

Microsoft Academic Search

Femtosecond lasers start to be routinely used in refractive eye surgery. Current research focuses on their application to glaucoma and cataract surgery as well as cornea transplant procedures. To avoid unwanted tissue damage during the surgical intervention it is of utmost importance to maintain a working energy just above the ablation threshold and maintain the laser energy at this working

Karsten Plamann; Valeria Nuzzo; Olivier Albert; Gérard A. Mourou; Michèle Savoldelli; Françoise Dagonet; David Donate; Jean-Marc Legeais

2007-01-01

369

Femtosecond laser ablation of metals: precise measurement and analytical model for crater profiles  

NASA Astrophysics Data System (ADS)

Laser ablation of Cu, Al, Fe, Zn, Ni, Pb, and Mo by short pulse laser (800nm wavelength, 70fs pulse duration, 0.01-28 J/cm2 fluence range) in air was studied. Three different ablation thresholds were distinguished in all metals. The lowest ablation threshold was of one order of magnitude lower than the one observed previously. In the fluence range of 0.018-0.18 J/cm2 the ablation rate was ~0.01 nm/pulse. A dependence of the threshold on the pulse duration was demonstrated in the range of 70 fs- 5 ps for cupper. As the laser pulse duration increased, the ablation threshold had the tendency to be higher. A periodic structure was observed at the bottom of the crater in all metals. The spacing d of the patterned structure was determined to be d=300+/-40 nm for 0.07 J/cm2 and d=600+/-40 nm for 0.22 J/cm2. The spacing depended on the laser fluence rather than on laser wavelength.

Hashida, Masaki; Fujita, Masayuki; Tsukamoto, Masahiro; Semerok, Alexandre F.; Gobert, Olivier; Petite, Guillaume; Izawa, Yasukazu; Wagner, J.-F.

2003-02-01

370

Absorption-Ablation-Excitation Mechanisms of Laser-Cluster Interactions in a Nanoaerosol System  

E-print Network

The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy (PS-LIBS). As the excitation laser intensity is increased beyond 0.16GW/cm2, the scattering cross-section of TiO_2 clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensities, the cross-sections of clusters decrease during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by non-dimensionalizing the Fokker-Planck equation, with analogous Strouhal Sl_E, Peclet Pe_E, and Damkohler Da_E n...

Ren, Yihua; Zhang, Yiyang; Tse, Stephen D; Long, Marshall B

2014-01-01

371

Growth of SiO(x) nanowires by laser ablation.  

PubMed

Amorphous SiO(x) nanowires (NWs) were synthesized using laser ablation of silicon-containing targets. The influence of various parameters such as target composition, substrate type, substrate temperature and carrier gas on the growth process was studied. The NWs were characterized using high resolution scanning and transmission electron microscopes (HRSEM and HRTEM) with their attachments: electron dispersive spectroscopy (EDS) and energy electron loss spectroscopy (EELS). A metal catalyst was found essential for the NW growth. A growth temperature higher than 1000?°C was necessary for the NW formation using an Ar-based carrier gas at 500 Torr. The use of Ar-5%H(2) instead of pure Ar resulted in a higher yield and longer NWs. Application of a diffusion barrier on top of the Si substrate guaranteed the availability of metal catalyst droplets on the surface, essential for the NW growth. Ni was found to be a better catalyst than Au in terms of the NW yield and length. Two alternative sequences for the evolution of the amorphous SiO(x) NWs were considered: (a) the formation of Si NWs first and their complete oxidation afterwards, which seems to be doubtful, (b) the direct formation of SiO(x) NWs, which is more likely to occur. The direct formation mechanism was proposed to advance in three stages: preferential adsorption of SiO(x) clusters on the catalyst surface first, a successive surface diffusion to the catalyst droplet lower hemisphere, and finally the formation and growth of the NW between the catalyst and the substrate. PMID:21730706

Aharonovich, Igor; Tamir, Shoshana; Lifshitz, Yeshayahu

2008-02-13

372

A study of gelatin ablation induced by a novel design TEA CO 2 laser  

Microsoft Academic Search

Ablation of gelatin samples was performed by using a semiconductively preionized TEA CO2 laser, emitting pulses of the lower TEM mode, 100 ns duration, at a repetition rate of 2.4Hz. Ablation rate experiments were performed at a range of fluences from 2J cm?2 to 10J cm?2. Assuming that the absorption coefficient is much larger than the scattering coefficient, experimental data

D. Yova; A. A. Serafetinides; M. Makropoulou

1991-01-01

373

In-vivo intratissue ablation by nanojoule near-infrared femtosecond laser pulses  

Microsoft Academic Search

Non-invasive intratissue ablation was performed in the cornea of living rabbits by using 80 MHz near-infrared intense nanojoule\\u000a femtosecond laser pulses. The intratissue surgical effect was induced by multiphoton absorption at a wavelength of 800 nm\\u000a and was ascertained by histological examination. Highly precise intratissue ablation was obtained with no detrimental effects\\u000a to the overlying or underlying layers. Activated keratocytes in the

Bao-Gui Wang; Iris Riemann; Harald Schubert; Karl-Juergen Halbhuber; Karsten Koenig

2007-01-01

374

Developments at the CERN laser ion source  

Microsoft Academic Search

The high current, high charge-state ion beam which can be extracted from a laser produced plasma is well suited, after initial acceleration, for injection into synchrotrons. At CERN, the production of a heavy ion beam using a CO2 laser ion source is studied. The latest results of experiments with a tantalum ion beam with charge states up to 23+ and

H. Haseroth; H. Kugler; K. Langbein; N. Lisi; A. Lombardi; H. Magnusson; W. Pirkl; J. C. Schnuriger; R. Scrivens; J. Tambini; E. Tanke; S. Homenko; K. Makarov; V. Roerich; A. Stepanov; Y. Satov; S. Kondrashev; S. Savin; B. Sharkov; A. Shumshurov; J. Krása; L. Láska; M. Pfeifer; E. Woryna

1998-01-01

375

Ablation of silicon by focusing a femtosecond laser through a subwavelength annular aperture structure  

NASA Astrophysics Data System (ADS)

We experimentally examined the effect of laser energy fluence on the ablation of a silicon wafer using a Ti:sapphire femtosecond laser system. A femtosecond laser was focused through an oxide-metal-oxide (Al2O3/Al/Al2O3) film engraved with a subwavelength annular aperture (SAA) structure, i.e., a Bessel beam composed of a femtosecond laser created using a SAA. The optical performance, such as depth-of-focus (DOF) and focal spot of the SAA structure, was simulated using finite-difference time domain (FDTD) calculations. We found that a far-field laser beam propagating through the SAA structure possesses a sub-micron focal spot as well as high focus intensity. The experimental results demonstrated that silicon can be ablated using an input ablation threshold of an order of 0.05 J/cm2 with a pulse duration at around 120fs. We found the obtained surface hole to have a diameter smaller than 1?m. Different surface ablation results obtained by using different threshold fluences of input laser energy are shown. Possible applications of this technique includes executing high aspect ratio laser drilling for thin film microfabrication, undertaking thru silicon via (TSV) for 3DIC, etc.

Yu, Y. Y.; Chang, C. K.; Lai, M. W.; Huang, L. S.; Lee, C. K.

2010-08-01

376

The Mixed Processing Models Development Of Thermal Fracture And Laser Ablation On Glass Substrate  

NASA Astrophysics Data System (ADS)

As the industries of cell phone and LCD TV were vigorously flourishing and the manufacturing requirements for LCD glass substrate were getting higher, the thermal fracture cutting technology (TFCT) has progressively become the main technology for LCD glass substrate cutting. Due to using laser as the heat source, the TFCT has many advantages, such as uniform heating, small heat effect zone, and high cutting speed, smooth cutting surface and low residual stress, etc. Moreover, a general laser ablation processing or traditional diamond wheel cutting does not have the last two advantages. The article presents a mixed processing of glass substrate, which consists of TFCT and laser ablation mechanisms, and how to enhance the cutting speed with little ablation laser energy. In this study, a 10W Nd:YAG laser and a 40W CO2 laser are used as the heat source of TFCT and laser ablation processing, respectively. The result indicates that the speed of the mixed processing is more than twice the speed of TFCT. Furthermore, after the mixed processing, the residual stresses in the glass substrates are also smaller.

Huang, Kuo-Cheng; Wu, Wen-Hong; Tseng, Shih-Feng; Hwang, Chi-Hung

2011-01-01

377

Wetting and other physical characteristics of polycarbonate surface textured using laser ablation  

NASA Astrophysics Data System (ADS)

Surface texturing of polycarbonate glass is carried out for improved hydrophobicity via controlled laser ablation at the surface. Optical and physical characteristics of the laser treated layer are examined using analytical tools including optical, atomic force, and scanning electron microscopes, Fourier transform infrared spectroscopy, and X-ray diffraction. Contact angle measurements are carried out to assess the hydrophobicity of the laser treated surface. Residual stress in the laser ablated layer is determined using the curvature method, and microhardnes and scratch resistance are analyzed using a micro-tribometer. Findings reveal that textured surfaces compose of micro/nano pores with fine cavities and increase the contact angle to hydrophobicity such a way that contact angles in the range of 120° are resulted. Crystallization of the laser treated surface reduces the optical transmittance by 15%, contributes to residual stress formation, and enhances the microhardness by twice the value of untreated polycarbonate surface. In addition, laser treatment improves surface scratch resistance by 40%.

Yilbas, B. S.; Khaled, M.; Abu-Dheir, N.; Al-Aqeeli, N.; Said, S. A. M.; Ahmed, A. O. M.; Varanasi, K. K.; Toumi, Y. K.

2014-11-01

378

Optical feedback-induced light modulation for fiber-based laser ablation.  

PubMed

Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30 % in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation. PMID:24913423

Kang, Hyun Wook

2014-11-01

379

Tissue ablation by a free-electron laser tuned to the amide II band  

Microsoft Academic Search

EFFORTS to ablate soft tissue with conventional lasers have been limited by collateral damage and by concern over potential photochemical effects1 5. Motivated by the thermal-confinement model6, past infrared investigations targeted the OH-stretch mode of water with fast pulses from lasers emitting near 3,000 nm (refs 1, 7 9). What does a free-electron laser offer for the investigation of tissue

Glenn Edwards; Regan Logan; Michael Copeland; Lou Reinisch; Jeffrey Davidson; Bruce Johnson; Robert Maciunas; Marcus Mendenhall; Robert Ossoff; Jerri Tribble; Jay Werkhaven; Denis O'Day

1994-01-01

380

Enhancement of muonium emission rate from silica aerogel with a laser ablated surface  

E-print Network

Emission of muonium ($\\mu^+e^-$) atoms from a laser-processed aerogel surface into vacuum was studied for the first time. Laser ablation was used to create hole-like regions with diameter of about 270$~\\mu$m in a triangular pattern with hole separation in the range of 300--500$~\\mu$m. The emission probability for the laser-processed aerogel sample is at least eight times higher than for a uniform one.

Beer, G A; Hirota, S; Ishida, K; Iwasaki, M; Kanda, S; Kawai, H; Kawamura, N; Kitamura, R; Lee, S; Marshall, W Lee G M; Mibe, T; Miyake, Y; Okada, S; Olchanski, K; Olin, A; Oishi, Y; Onishi, H; Otani, M; Saito, N; Shimomura, K; Strasser, P; Tabata, M; Tomono, D; Ueno, K; Yokoyama, K; Won, E

2014-01-01

381

Enhancement of muonium emission rate from silica aerogel with a laser ablated surface  

E-print Network

Emission of muonium ($\\mu^+e^-$) atoms from a laser-processed aerogel surface into vacuum was studied for the first time. Laser ablation was used to create hole-like regions with diameter of about 270$~\\mu$m in a triangular pattern with hole separation in the range of 300--500$~\\mu$m. The emission probability for the laser-processed aerogel sample is at least eight times higher than for a uniform one.

G. A. Beer; Y. Fujiwara; S. Hirota; K. Ishida; M. Iwasaki; S. Kanda; H. Kawai; N. Kawamura; R. Kitamura; S. Lee; W. Lee G. M. Marshall; T. Mibe; Y. Miyake; S. Okada; K. Olchanski; A. Olin; Y. Oishi; H. Onishi; M. Otani; N. Saito; K. Shimomura; P. Strasser; M. Tabata; D. Tomono; K. Ueno; K. Yokoyama; E. Won

2014-07-31

382

Enhancement of muonium emission rate from silica aerogel with a laser-ablated surface  

NASA Astrophysics Data System (ADS)

Emission of muonium (? ^+e^-) atoms from a laser-processed aerogel surface into vacuum was studied for the first time. Laser ablation was used to create hole-like regions with diameter of about 270 ? m in a triangular pattern with hole separation in the range of 300-500 ? m. The emission probability for the laser-processed aerogel sample is at least eight times higher than for a uniform one.

Beer, G. A.; Fujiwara, Y.; Hirota, S.; Ishida, K.; Iwasaki, M.; Kanda, S.; Kawai, H.; Kawamura, N.; Kitamura, R.; Lee, S.; Lee, W.; Marshall, G. M.; Mibe, T.; Miyake, Y.; Okada, S.; Olchanski, K.; Olin, A.; Ohnishi, H.; Oishi, Y.; Otani, M.; Saito, N.; Shimomura, K.; Strasser, P.; Tabata, M.; Tomono, D.; Ueno, K.; Won, E.; Yokoyama, K.

2014-09-01

383

Ion Acceleration Characteristics of a Laser-Electrostatic Hybrid Microthruster  

SciTech Connect

A fundamental study on laser-electrostatic hybrid acceleration thruster was conducted, in which laser-induced plasmas were induced through laser beam irradiation on to a solid target and accelerated by an electrostatic field of an acceleration electrode. For thrust measurements, a calibrated torsion-balance type thrust-stand was developed and utilized. A time-of-flight measurement with a Faraday cup was also conducted for ion current and velocity measurements. It was found that an average speed of ions of a pure laser ablation was about 50 km/sec for 40 {mu}J/pulse with pulse width of 250 psec. Moreover, for acceleration voltage of Vaccl = + 300 V, T = 1.8 {mu}N, Isp = 3600 sec, and {eta}th = 52 % were achieved. It was shown that an acceleration electrode with positive potential was more effective than that with negative potential for positive-ion acceleration in the laser induced plasma, in which ions were induced with the Coulomb explosion.

Igari, Akira; Horisawa, Hideyuki [Department of Aeronautics and Astronautics, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292 (Japan); Kimura, Itsuro [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8856 (Japan)

2005-04-27

384

A Randomized Study Comparing Visual Laser Ablation and Transurethral Evaporation of Prostate in the Management of Benign Prostatic Hyperplasia  

Microsoft Academic Search

PurposeWe evaluated the safety, efficacy, failure and complications of 2 techniques of laser prostatectomy for benign prostatic hyperplasia (BPH): transurethral evaporation of the prostate (evaporation) versus visual laser ablation of the prostate (coagulation) in a randomized trial.

Ashutosh Tewari; Sherif Aboseif; Christopher Evans

1995-01-01

385

High-speed photography of excimer laser ablation of the cornea.  

PubMed

We have used laser-based high-speed photography to investigate excimer laser ablation of the cornea. Photographs of the ablation plume were obtained 500 ns to 150 microseconds after incidence of a 193- or 248-nm excimer laser pulse on the surface of the cornea. Ejection of material from the cornea begins on a time scale of nanoseconds and continues for 5 to 15 microseconds following the excimer pulse. At 193 nm the ablation plume resembles a burst of smoke, and individual particles are too small to be optically resolved with our apparatus. At 248 nm the plume resembles a spray of larger, discrete droplets. Material is ejected from the cornea at supersonic velocity but decelerates rapidly; the velocity for the first 500 ns following the excimer pulse averages 400 m/s at 193 nm. Plume size and velocity increase with increasing fluence. PMID:3632443

Puliafito, C A; Stern, D; Krueger, R R; Mandel, E R

1987-09-01

386

Fabrication of a super-hydrophobic surface on metal using laser ablation and electrodeposition  

NASA Astrophysics Data System (ADS)

In this research, the fabrication process of a super-hydrophobic metallic surface using laser ablation and electrodeposition was investigated. Re-entrant structure and surface roughness play an important role in forming a super-hydrophobic surface on intrinsically hydrophilic material. A micro pillar array with a re-entrant structure of copper on stainless steel was fabricated through a sequential process of laser ablation, insulating, mechanical polishing and electrodeposition. Spacing of the micro pillars in the array played a major role in the structure hydrophobicity that was confirmed by measuring the water contact angle. Surface morphology changed relative to the parameters of the laser ablation process and electrodeposition process. Under a gradual increase in current density during the electrodeposition process, surface morphology roughness was maximized for fabricating a super-hydrophobic surface. Finally, the super-hydrophobic surface was successfully fabricated on metal.

Kwon, Min Ho; Shin, Hong Shik; Chu, Chong Nam

2014-01-01

387

Investigations of morphological features of picosecond dual-wavelength laser ablation of stainless steel  

NASA Astrophysics Data System (ADS)

Investigations on the morphological features of holes and grooves ablated on the surface of stainless steel using the picosecond dual-wavelength laser system with different powers combinations are presented based on the scarce researches on morphology of dual-wavelength laser ablation. The experimental results show the profiles of holes ablated by the visible beam appear V-shaped while those for the near-infrared have large openings and display U-shaped, which are independent of the ablation mechanism of ultrafast laser. For the dual-wavelength beam (a combination of visible beam and near-infrared), the holes resemble sunflower-like structures and have smoother ring patterns on the bottom. In general, the holes ablated by the dual-wavelength beam appear to have much flatter bottoms, linearly sloped side-walls and spinodal structures between the bottoms of the holes and the side-walls. Furthermore, through judiciously combining the powers of the dual-wavelength beam, high-quality grooves could be obtained with a flat worm-like structure at the bottom surface and less resolidified melt ejection edges. This study provides insight into optimizing ultrafast laser micromachining in order to obtain desired morphology.

Zhao, Wanqin; Wang, Wenjun; Mei, Xuesong; Jiang, Gedong; Liu, Bin

2014-06-01

388

Feasibility of ablative fractional laser-assisted drug delivery with optical coherence tomography  

PubMed Central

Fractional resurfacing creates hundreds of microscopic wounds in the skin without injuring surrounding tissue. This technique allows rapid wound healing owing to small injury regions, and has been proven as an effective method for repairing photodamaged skin. Recently, ablative fractional laser (AFL) treatment has been demonstrated to facilitate topical drug delivery into skin. However, induced fractional photothermolysis depends on several parameters, such as incident angle, exposure energy, and spot size of the fractional laser. In this study, we used fractional CO2 laser to induce microscopic ablation array on the nail for facilitating drug delivery through the nail. To ensure proper energy delivery without damaging tissue structures beneath the nail plate, optical coherence tomography (OCT) was implemented for quantitative evaluation of induced microscopic ablation zone (MAZ). Moreover, to further study the feasibility of drug delivery, normal saline was dripped on the exposure area of fingernail and the speckle variance in OCT signal was used to observe water diffusion through the ablative channels into the nail plate. In conclusion, this study establishes OCT as an effective tool for the investigation of fractional photothermolysis and water/drug delivery through microscopic ablation channels after nail fractional laser treatment.

Yang, Chih-Hsun; Tsai, Meng-Tsan; Shen, Su-Chin; Ng, Chau Yee; Jung, Shih-Ming

2014-01-01

389

Orbit Modification of Earth-Crossing Asteroids/Comets Using Rendezvous Spacecraft and Laser Ablation  

NASA Technical Reports Server (NTRS)

This report describes the approach and results of an end-to-end simulation to deflect a long-period comet (LPC) by using a rapid rendezvous spacecraft and laser ablation system. The laser energy required for providing sufficient deflection DELTA V and an analysis of possible intercept/rendezvous spacecraft trajectories are studied in this analysis. These problems minimize a weighted sum of the flight time and required propellant by using an advanced propulsion system. The optimal thrust-vector history and propellant mass to use are found in order to transfer a spacecraft from the Earth to a targeted celestial object. One goal of this analysis is to formulate an optimization problem for intercept/rendezvous spacecraft trajectories. One approach to alter the trajectory of the object in a highly controlled manner is to use pulsed laser ablative propulsion. A sufficiently intense laser pulse ablates the surface of a near-Earth object (NEO) by causing plasma blowoff. The momentum change from a single laser pulse is very small. However, the cumulative effect is very effective because the laser can interact with the object over long periods of time. The laser ablation technique can overcome the mass penalties associated with other nondisruptive approaches because no propellant is required to generate the DELTA V (the material of the celestial object is the propellant source). Additionally, laser ablation is effective against a wide range of surface materials and does not require any landing or physical attachment to the object. For diverting distant asteroids and comets, the power and optical requirements of a laser ablation system on or near the Earth may be too extreme to contemplate in the next few decades. A hybrid solution would be for a spacecraft to carry a laser as a payload to a particular celestial body. The spacecraft would require an advanced propulsion system capable of rapid rendezvous with the object and an extremely powerful electrical generator, which is likely needed for the propulsion system as well. The spacecraft would station-keep with the object at a small standoff distance while the laser ablation is performed.

Park, Sang-Young; Mazanek, Daniel D.

2005-01-01

390

Heating and ablation of tokamak graphite by pulsed nanosecond Nd-YAG lasers  

SciTech Connect

The results on laser heating and ablation of graphite tiles of thermonuclear tokamaks are presented. Two pulsed Nd-YAG lasers (20 Hz repetition rate, 5 ns pulse duration and 10 kHz repetition rate, 100 ns pulse duration) were applied for ablation measurements. The ablation thresholds (1.0{+-}0.5 J/cm{sup 2} for 5 ns and 2.5{+-}0.5 J/cm{sup 2} for 100 ns laser pulses) were determined for the Tore Supra tokamak graphite tiles (backside) nonexposed to plasma. The high repetition rate Nd-YAG laser (10 kHz, 100 ns pulse duration) and the developed pyrometer system were applied for graphite heating measurements. Some unexpected features of laser heating of the graphite surface were observed. They were explained by the presence of a thin surface layer with the properties different from those of the bulk graphite. The theoretical models of laser heating and near-threshold ablation of graphite with imperfectly adhered layer were developed to interpret the experimental results.

Semerok, A.; Fomichev, S. V.; Weulersse, J.-M.; Brygo, F.; Thro, P.-Y.; Grisolia, C. [CEA Saclay, DEN/DPC/SCP/LILM, Batiment 467, 91191 Gif sur Yvette (France); CEA Cadarache, DSM/DRFC, Batiment 506, 13108 Saint Paul Lez Durance (France)

2007-04-15

391

Laser ion source development at Holifield Radioactive Ion Beam Facility  

SciTech Connect

This report describes the efforts made to develop a resonant-ionization laser ion source based on tunable Ti:sapphire lasers for nuclear physics and astrophysics research at Holifield Radioactive Ion Beam Facility. Three Ti:sapphire lasers have been upgraded with individual pump lasers to eliminate laser power losses due to synchronization delays. Ionization schemes for 14 elements have been obtained. Off-line studies show that the overall efficiency of the laser ion source can be as high as 40%. TaC surface coatings have been investigated for minimizing surface and bulk trapping of the atoms of interest.

Liu, Y.; Havener, C. C.; Beene, J. R. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Gottwald, T.; Mattolat, C.; Vane, C. R.; Wendt, K. [Institute of Physics, University of Mainz, D-55099 Mainz (Germany); Howe, J. Y.; Kiggans, J. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2012-02-15

392

Laser ion source development at Holifield Radioactive Ion Beam Facilitya)  

NASA Astrophysics Data System (ADS)

This report describes the efforts made to develop a resonant-ionization laser ion source based on tunable Ti:sapphire lasers for nuclear physics and astrophysics research at Holifield Radioactive Ion Beam Facility. Three Ti:sapphire lasers have been upgraded with individual pump lasers to eliminate laser power losses due to synchronization delays. Ionization schemes for 14 elements have been obtained. Off-line studies show that the overall efficiency of the laser ion source can be as high as 40%. TaC surface coatings have been investigated for minimizing surface and bulk trapping of the atoms of interest.

Liu, Y.; Gottwald, T.; Havener, C. C.; Howe, J. Y.; Kiggans, J.; Mattolat, C.; Vane, C. R.; Wendt, K.; Beene, J. R.

2012-02-01

393

Influence of ion-beam energy and substrate temperature on the synthesis of carbon nitride thin films by nitrogen-ion-assisted pulsed laser deposition  

Microsoft Academic Search

Carbon nitride thin films were deposited on silicon wafers by pulsed KrF excimer laser (wavelength 248 nm, duration 23 ns) ablation of graphite with assistance of nitrogen ion beam bombardment. X-ray photoelectron spectroscopy, Raman spectroscopy, and ellipsometry were used to identify the binding structure, nitrogen content, and optical properties of the deposited thin films. The influence of the nitrogen ion

Y. F. Lu; Z. M. Ren; T. C. Chong; B. A. Cheong; S. I. Pang; J. P. Wang; K. Li

1999-01-01

394

Femtosecond laser ablation inductively coupled plasma mass spectrometry: fundamentals and capabilities for depth profiling analysis.  

PubMed

Laser ablation coupled to inductively coupled plasma mass spectrometry has become a versatile and powerful analytical method for direct solid analysis. The applicability has been demonstrated on a wide variety of samples, where major, minor, and trace element concentrations or isotope ratio determinations have been of interest. The pros and cons of UV-nsec laser ablation have been studied in detail, and indicate that aerosol generation, aerosol transport, and aerosol excitation-ionization within the ICP contribute to fractionation effects, which prevent this method from a more universal application to all matrices and all elements. Recent progresses in IR-fs and UV-fs laser ablation coupled to ICP-MS have been reported, which increase the inter-matrix and multi-element quantification capabilities of this method. These fundamental improvements in LA-ICP-MS are of significant importance for entering new applications in material science and related research fields. In particular, because coatings (conducting and non-conducting) consist of single or multilayers of various elemental composition and of different thickness (nm-mm range), significant progress in the field of depth profiling with fs-laser ablation can be expected. Therefore, in-depth profile analysis of polymers, semiconductors, and metal sample investigations, using ultra-fast laser ablation for sampling and the currently achievable figures of merit, are discussed. In this review manuscript, the enhanced capabilities of fs-LA-ICP-MS for direct solid sampling are highlighted, and it is discussed about current methods used for quantitative analysis and depth profiling, the ablation process of UV-ns and UV-fs, the influence of the laser beam profile, aerosol structure and transport efficiency, as well as the influence of the ICP-MS (e.g., vaporization and ionization efficiency in the plasma, and type of mass analyzer). PMID:18636536

Pisonero, Jorge; Günther, Detlef

2008-01-01

395

Minimization of thermomechanical side effects and increase of ablation efficiency in IR ablation by use of multiply Q-switched laser pulses  

NASA Astrophysics Data System (ADS)

Large thermal damage zones have been observed after application of free-running holmium laser pulses inside the human body as, for example, for arthroscopic surgery. The aim of our study is to reduce thermal damage by increasing the ablation efficiency, and to achieve a smooth surface of the ablated tissue. For that purpose we use a multiply Q- switched thulium laser ((lambda) equals 2.0 micrometers , acousto- optical QS) that emits pulse series consisting of a pre- pulse of 40 mJ energy and up to 6 ablation pulses of 100 mJ each, separated by time intervals of 60 microsecond(s) . Q-switched laser pulses explosively ablate the target material. In a liquid environment, this leads to the formation of cavitation bubbles and to mechanical damage of the surrounding tissue. The pre-pulse of 40 mJ serves to minimize the cavitation effects, as it produces a small cavity that is then filled by the ablation products created by the burst of 100-mJ pulses. The pre-pulse creates, furthermore, a channel between fiber tip and target that reduces absorption losses in the liquid. Reduction of cavitation effects and channel formation are demonstrated by time-resolved photography. The use of a thulium laser instead of a holmium laser contributed to the desired reduction of thermal damage, because the penetration depth of the thulium laser light in cartilage (approximately 170 micrometers ) is only half as large as with the holmium laser.

Vogel, Alfred; Schmidt, Peter; Flucke, Barbara

2002-06-01

396

Experimental scaling laws for ablation parameters in plane target-laser interaction with 1.06 µm and 0.35 µm laser wavelengths  

NASA Astrophysics Data System (ADS)

Ablation parameters such as velocity, mass, momentum, pressure, and hydrodynamic efficiency have been investigated with plane targets irradiated in the range 3×1011-1015 W cm-2 with 1 nsec pulses and laser wavelengths of 1.06 ?m and 0.35 ?m. We show that ablation velocity, ablated mass, and momentum are in good agreement with ablation scaling laws deduced from analytical models taking into account inverse bremsstrahlung absorption below the critical density. Nevertheless, processes such as lateral conduction, hot spot, and preheat effects make inaccurate the comparison between ablation pressures, mass ablation rates, or hydrodynamic efficiencies measured for different laser wavelengths. Laser illumination nonuniformities are transmitted to the target in terms of pressure variations. The harmful consequence of a reduced lateral energy flow in 0.35 ?m experiments can eclipse the increasing of ablation pressure and hydrodynamic efficiency.

Meyer, B.; Thiell, G.

1984-01-01

397

Femtosecond laser ablation of neurons in C. elegans for behavioral studies  

NASA Astrophysics Data System (ADS)

Femtosecond laser ablation selectively dissects subcellular components of the C. elegans neuronal circuit with submicrometer precision for studying the neuronal origins of behavior. We describe the theoretical basis for the high precision of femtosecond laser ablation in the target bulk. Next, we present the experimental setup and a worm rotation technique to facilitate imaging and surgery. We describe the damage caused by different pulse energies on cell bodies and neuronal fibers. Finally, we discuss the regrowth of neuronal fibers after surgery and its impact on behavioral study.

Chung, Samuel H.; Mazur, Eric

2009-08-01

398

Asymmetric partitioning of metals among cluster anions and cations generated via laser ablation of mixed aluminum/Group 6 transition metal targets.  

PubMed

While high-power laser ablation of metal alloys indiscriminately produces gas-phase atomic ions in proportion to the abundance of the various metals in the alloy, gas-phase ions produced by moderate-power laser ablation sources coupled with molecular beams are formed by more complicated mechanisms. A mass spectrometric study that directly compares the mass distributions of cluster anions and cations generated from laser ablation of pure aluminum, an aluminum/molybdenum mixed target, and an aluminum/tungsten mixed target is detailed. Mass spectra of anionic species generated from the mixed targets showed that both tungsten and molybdenum were in higher abundance in the negatively charged species than in the target material. Mass spectra of the cationic species showed primarily Al(+) and aluminum oxide and hydroxide cluster cations. No molybdenum- or tungsten-containing cluster cations were definitively assigned. The asymmetric distribution of aluminum and Group 6 transition metals in cation and anion cluster composition is attributed to the low ionization energy of atomic aluminum and aluminum suboxide clusters. In addition, the propensity of both molybdenum and tungsten to form metal oxide cluster anions under the same conditions that favor metallic aluminum cluster anions is attributed to differences in the optical properties of the surface oxide that is present in the metal powders used to prepare the ablation targets. Mechanisms of mixed metal oxide clusters are considered. PMID:23413829

Waller, Sarah E; Mann, Jennifer E; Jarrold, Caroline Chick

2013-02-28

399

Investigation of the spatial and temporal distribution of plasma excited species produced in laser ablation-glow discharge  

NASA Astrophysics Data System (ADS)

Laser Ablation and Glow Discharge (LAGD) plasmas have been coupled and optical emission measurements have been performed in order to study the spatial and temporal distribution of LA and GD species and hence to get further insights into the interaction between them. The relative delay between the laser event and the emission measurement along the GD pulse has been found as a crucial parameter. In addition, no post excitation of the ablated material has been observed when laser ablation takes place during GD prepeak or plateau. In contrast, emission enhancements (e.g. Al I lines at ~ 877 nm presented an enhancement of up to 4 times in the LAGD plasma) were obtained during the afterglow or late plateau, when firing the laser at delays close (< 100 ?s) to GD pulse termination. Penning ionization of the ablated material within the GD afterglow, followed by recombination processes, seems to account for the emission enhancements obtained when combining laser ablation and glow discharge.

Valledor, Rebeca; Tarik, Mohamed; Pisonero, Jorge; Bordel, Nerea; Günther, Detlef

2014-10-01

400

Chapter 5 Laser Ablation at the Solid/Liquid Interface 138 Chapter 5 Laser Ablation at the Solid/Liquid  

E-print Network

of both white and red phosphorus under various carbon containing liquids will be presented. From ablation of graphite under water was clear in appearance, containing a visible suspended black solid. After

Bristol, University of

401

Laser ion source for low charge heavy ion beams  

SciTech Connect

For heavy ion inertial fusion application, a combination of a laser ion source and direct plasma injection scheme into an RFQ is proposed. The combination might provide more than 100 mA of singly charged heavy ion beam from a single laser shot. A planned feasibility test with moderate current is also discussed.

Okamura,M.; Pikin, A.; Zajic, V.; Kanesue, T.; Tamura, J.

2008-08-03

402

Improved analytical characterization of solid waste forms (glass, metals, soils) by fundamental development of the laser ablation technology. 1997 annual progress report  

Microsoft Academic Search

'Laser ablation is a promising technology for chemical characterization within every DOE EM major problem area (high-level waste tanks, contaminant plumes, D and D activities, spent nuclear fuel, mixed wastes, landfills, nuclear waste disposal, and HEU disposition). This EMSP research endeavors to expand the fundamental basis in laser ablation technology for its application to these DOE characterization needs. Laser ablation

1997-01-01

403

Comparative shock wave analysis during corneal ablation with an excimer laser, picosecond laser, and femtosecond laser  

Microsoft Academic Search

With the event of topographic steep central islands following excimer laser surgery and the potential damage to the corneal endothelium, shock waves are playing an increasingly important role in laser refractive surgery. With this in mind, we performed a comparative shock wave analysis in corneal tissue using an excimer laser, picosecond laser, and femtosecond laser. We used a Lambda Physik

Ronald R. Krueger; Tibor Juhasz

1995-01-01

404

Laser ablation for small hepatocellular carcinoma: State of the art and future perspectives  

PubMed Central

During the last two decades, various local thermal ablative techniques for the treatment of unresectable hepatocellular carcinoma (HCC) have been developed. According to internationally endorsed guidelines, percutaneous thermal ablation is the mainstay of treatment in patients with small HCC who are not candidates for surgical resection or transplantation. Laser ablation (LA) represents one of currently available loco-ablative techniques. In this article, the general principles, technique, image guidance, and patient selection are reported. Primary effectiveness, long-term outcome, and complications are also discussed. A review of published data suggests that LA is equivalent to the more popular and widespread radiofrequency ablation in both local tumor control and long-term outcome in the percutaneous treatment of early HCC. In addition, the LA technique using multiple thin laser fibres allows improved ablative effectiveness in HCCs greater than 3 cm. Reference centres should be equipped with all the available techniques so as to be able to use the best and the most suitable procedure for each type of lesion for each patient. PMID:25349642

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

2014-01-01

405

Pulsed laser ablation of binary semiconductors: mechanisms of vaporisation and cluster formation  

SciTech Connect

Formation of small clusters during pulsed ablation of two binary semiconductors, zinc oxide and indium phosphide, in vacuum by UV, visible, and IR laser radiation is comparatively studied. The irradiation conditions favourable for generation of neutral and charged Zn{sub n}O{sub m} and In{sub n}P{sub m} clusters of different stoichiometry in the ablation products are found. The size and composition of the clusters, their expansion dynamics and reactivity are analysed by time-of-flight mass spectrometry. A particular attention is paid to the mechanisms of ZnO and InP ablation as a function of laser fluence, with the use of different ablation models. It is established that ZnO evapourates congruently in a wide range of irradiation conditions, while InP ablation leads to enrichment of the target surface with indium. It is shown that this radically different character of semiconductor ablation determines the composition of the nanostructures formed: zinc oxide clusters are mainly stoichiometric, whereas In{sub n}P{sub m} particles are significantly enriched with indium. (photonics and nanotechnology)

Bulgakov, A V; Evtushenko, A B; Shukhov, Yu G [S S Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Ozerov, I; Marin, W [Universite de la Mediterranee, CINaM, UPR CNRS 3118, Marseille (France)

2010-12-29

406

Laser mass ablation efficiency measurements indicate bubble-driven dynamics dominates laser thrombolysis  

SciTech Connect

Mass removal experiments have been performed at the Oregon Medical Laser Center with 10 to 100 mJ 1 {micro}s laser pulses at optical wavelengths. Above the energy threshold for bubble formation, the laser mass ablation efficiency ({micro}g/mJ) for removal of gel surrogate thrombus is nearly constant for a given experimental geometry and gel absorption coefficient. The efficiency in contact experiments, in which the optical fiber delivering the energy is in close proximity to the absorbing gel, is approximately three times that of non-contact experiments, in which the optical fiber is {approximately}1 mm from the gel. Mass removal occurs hundreds of microseconds after the laser deposition. Experimental data and numerical simulations are consistent with the hypothesis that jet formation during bubble collapse plays a dominant role in mass removal. This hypothesis suggests a model in which the mass removed scales linearly with the maximum bubble volume and explains the distinctive features, including the magnitude, of the mass removal.

Godwin, R.P.; Chapyak, E.J. [Los Alamos National Lab., NM (United States). Applied Theoretical and Computational Physics Div.; Prahl, S.A.; Shangguan, H.Q. [Providence St. Vincent Hospital, Portland, OR (United States). Oregon medical Laser Center

1998-03-01

407

Polarization-dependent femtosecond laser ablation of poly-methyl methacrylate  

NASA Astrophysics Data System (ADS)

We show that ablation features in poly-methyl methacrylate (PMMA) induced by a single femtosecond laser pulse are imposed by light polarization. The ablation craters are elongated along the major axis of the polarization vector and become increasingly prominent as the pulse energy is increased above the threshold energy. We demonstrate ˜40% elongation for linearly and elliptically polarized light in the fluence range of 4-20 J cm-2, while circularly polarized light produced near circular ablation craters irrespective of pulse energies. We also show that irradiation with multiple pulses erases the polarization-dependent elongation of the ablation craters. However, for line ablation the orientation of the electric field vector is imprinted in the form of quasi-periodic structures inside the ablated region. Theoretically, we show that the polarization dependence of the ablation features arises from a local field enhancement during light-plasma interaction. Simulations also show that in materials with high nonlinearities such as doped PMMA, in addition to conventional explosive boiling, sub-surface multiple filamentation can also give rise to porosity.

Guay, J.-M.; Villafranca, A.; Baset, F.; Popov, K.; Ramunno, L.; Bhardwaj, V. R.

2012-08-01

408

Kinetic theory analysis of laser ablation of carbon: Applicability of one-dimensional models  

SciTech Connect

The paper discusses the applicability of a one-dimensional approximation in a recently proposed model of ablation of carbon by a nanosecond laser pulse that considers the kinetics of the process. The model approximates the process as sublimation and combines conduction heat transfer in the target with the gas dynamics of the ablated plume which are coupled through the boundary conditions at the interface. The ablated mass flux and the temperature of the ablating material are obtained from the conservation relations at the interface derived from the moment solution of the Boltzmann equation for arbitrarily strong evaporation. It is shown that in the one-dimensional approximation the surface pressure and the ablation rate are too low and that the ablation rate is restricted most of the time by the kinetic theory limitation on the maximum mass flux that can be attained in a phase-change process. As a consequence, the model overpredicts the surface temperature and the duration of the process. However, it predicts the total ablated mass with good accuracy.

Shusser, Michael [Faculty of Mechanical Engineering, Technion, Haifa 32000 (Israel)

2007-02-01

409

Optical properties of petal-like aggregated nanocrystalline zinc oxide synthesized by laser ablation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Petal like ZnO nanocrystals are synthesized by high frequency laser ablation in water. Black-Right-Pointing-Pointer Optical band gap of ZnO nanocrystals was tunable by changing the laser pulse energy. Black-Right-Pointing-Pointer Nonlinear optical properties and limiting threshold were obtained by Z-scan technique. -- Abstract: The results of the investigations carried out on the third-order nonlinearity in zinc oxide (ZnO) nanocrystals (NCs) by Z-scan technique are included in this paper. ZnO NCs show negative nonlinearity and good nonlinear absorption behavior at 532 nm. The third-order optical susceptibility {chi}(3) increases with enlargement of NCs due to the size dependent enhancement of exciton oscillator strength. The synthesis of ZnO NCs was performed by laser ablation from a high-purity metallic target of Zn in distilled water medium. For the ablation process, a high frequency pulsed Nd:YAG laser was employed operating at 532 nm with 100 ns pulse duration. UV-vis absorption spectroscopy illustrated the enhancement of the size of ZnO NCs upon increasing the laser pulse energy applied in ablation process. Accordingly the corresponding optical band gap (E{sub g}) decrease by increasing the size of NCs. X-ray diffraction (XRD) associated with transmission electron microscopy (TEM) was utilized to characterize the crystalline phase and also for determining the ZnO NCs morphology.

Jafarkhani, P.; Chehrghani, A. [Iranian National Centre for Laser Science and Technology (INLC), PO Box: 14665-576, Tehran (Iran, Islamic Republic of)] [Iranian National Centre for Laser Science and Technology (INLC), PO Box: 14665-576, Tehran (Iran, Islamic Republic of); Torkamany, M.J., E-mail: mjtorkamany@inlc.ir [Iranian National Centre for Laser Science and Technology (INLC), PO Box: 14665-576, Tehran (Iran, Islamic Republic of)

2012-03-15

410

Photodynamic Therapy with Ablative Carbon Dioxide Fractional Laser in Treatment of Actinic Keratosis  

PubMed Central

Background Recently, photodynamic therapy (PDT) has been shown to be an effective first-line treatment for actinic keratosis (AK). However, a major limitation of PDT is the long incubation time required to allow penetration of the photosensitizer. Objective The aim of this study was to assess if pretreatment with an ablative carbon dioxide (CO2) fractional laser can reduce the incubation time of the photosensitizer. Methods Initially, 29 patients with a total of 34 AK lesions were treated with an ablative CO2 fractional laser at Ajou University Hospital between January and December 2010. Immediately after the laser treatment, topical 20% 5-aminolevulinic acid or methyl-aminolevulinate was applied to the AK lesions and incubated for 70 to 90 minutes. Then, the treated areas were illuminated with a red light source. Improvement was clinically or histologically assessed eight weeks after the treatment. Results In spite of the short incubation time, 24 lesions (70.6%) showed a complete response (CR) within three sessions of PDT (10 lesions a clinical CR and 14 lesions a clinical/histological CR). There were no significant side effects associated with the combination of ablative CO2 fractional laser and PDT. Conclusion Ablative CO2 fractional laser may be considered an additional treatment option for reducing the incubation time of the photosensitizer in PDT. PMID:24371387

Jang, Yong Hyun; Lee, Dong Jun; Shin, Jaeyoung; Kang, Hee Young; Lee, Eun-So

2013-01-01

411

Corneal tissue ablation using 6.1 ?m quantum cascade laser  

NASA Astrophysics Data System (ADS)

High absorption property of tissues in the IR range (?> 2 ?m) results in effective tissue ablation, especially near 3 ?m. In the mid-infrared range, wavelengths of 6.1 ?m and 6.45 ?m fall into the absorption bands of the amide protein groups Amide-I and Amide-II, respectively. They also coincide with the deformation mode of water, which has an absorption peak at 6.1 ?m. This coincidence makes 6.1 ?m laser a better ablation tool that has promising effectiveness and minimum collateral damages than 3 ?m lasers. In this work, we performed bovine corneal ablation test in-vitro using high-power 6.1?m quantum cascade laser (QCL) operated at pulse mode. Quantum cascade laser has the advantages of low cost, compact size and tunable wavelength, which makes it great alternative Mid-IR light source to conventional tunable free-electron lasers (FEL) for medical applications. Preliminary results show that effective corneal stroma craters were achieved with much less collateral damage in corneal tissue that contains less water. Future study will focus on optimizing the control parameters of QCL to attain neat and precise ablation of corneal tissue and development of high peak power QCL.

Huang, Yong; Kang, Jin U.

2012-03-01

412

351-nm femtosecond laser with Nd:glass regenerative amplifier for thin films ablation  

NASA Astrophysics Data System (ADS)

Recently, ultra-fast pulse lasers have been attractive in the field of fine processing applications, such as three-dimensional optical waveguides, photonic crystals and ablation. Because femotosecond lasers have the superior characteristics of a short pulse width and high peak power, we can reduce thermal influence that causes splatters, roll up of the edge and damages of glass substrate in the thin films ablation. Due to this non-thermal ablation process, a control of the stable and fine process can be available. In this letter, we LFT (Laserfront Technologies, Inc., former NEC Laser Solution Division) have developed a femtosecond laser system. It consists of a mode-locked fiber oscillator, a regenerative amplifier, a pulse compressor and a third harmonic generator. The gain media of the regenerative amplifier is Nd:glass. The output energy of the regenerative amplifier is 3mJ at 7 Hz repetition rate. The final THG (351 nm) output energy is 300?J, 10% conversion efficiency was obtained. Using above femtosecond laser, we conducted ablation processing of thin films such as aluminum on the glass substrate. The results of fine processing are reported.

Mukaihara, Katsuji; Yoshioka, Masao; Ito, Shinji; Suzuki, Yoshikazu

2006-02-01

413

Waste volume reduction using surface characterization and decontamination by laser ablation. 1998 annual progress report  

SciTech Connect

'Much of the contaminated concrete from nuclear facilities contains radionuclides only in the near surface region. Removal of the contaminated layer would greatly reduce the volume of waste requiring storage. The objectives of this research are to understand the depth-dependent concentration and chemistry of radionuclide-contaminated concrete surfaces, to determine the mechanism and efficacy of laser ablation in removing contaminated surface layers, and to chemically and physically characterize the captured ablation effluent which would become the stored waste. This report summarizes work from the first eight months of a three-year project. Samples consisted of specimens of non-contaminated high density concrete from the Experimental Boiling Water Reactor at Argonne National Laboratory (sectioned into small coupons) and samples cast in the laboratory using Type 1 Portland cement and either silica, alumina, or sand. Some samples of concrete and cement were doped with Cs-133. Ablation experiments were done with a 1.6 kW pulsed Nd:YAG laser. The beam was delivered via a fiber optic cable, focused to a 0.5 \\265m spot, and rastered across the surface. The ablated material was collected with a vacuum shroud system and captured on a 0.2 micron filter. Virgin and ablated surfaces were chemically analyzed with laser desorption surface mass spectrometry.'

Pellin, M.J.; Leong, K.; Savina, M.R.

1998-06-01

414

Synthesis efficiency of heavy carbon clusters from ETFE ablated by different numbers of laser pulse in vacuum  

NASA Astrophysics Data System (ADS)

We have carried out mass spectral analysis of positive ions produced by laser ablation of a copolymer of ethylene and tetrafluoroethylene (ETFE: [?CH 2?CH 2?CF 2?CF 2?] n) in vacuum using time-of-flight mass spectrometry (TOF-MS). The surfaces of the ETFE targets irradiated by different numbers of laser pulse were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Heavy carbon cluster ions C n+ with n?30 were observed in the mass spectra. The fractional abundance of heavy clusters in the mass spectrum decreased with the number of laser pulse. On the other hand, carbon became rich in the atomic composition of the laser-irradiated surface, and the eroded area on the surface increased with the number of laser pulse. From these results, it is suggested that the carbon-rich material surface results in the less efficient production of heavy carbon clusters. In addition, it is also suggested that clustering reactions in eroded craters do not contribute to the synthesis of heavy clusters.

Shibagaki, K.; Takada, N.; Sasaki, K.; Kadota, K.

2002-09-01

415