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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

Laser ablation loading of a radiofrequency ion trap  

E-print Network

The production of ions via laser ablation for the loading of radiofrequency (RF) ion traps is investigated using a nitrogen laser with a maximum pulse energy of 0.17 mJ and a peak intensity of about 250 MW/cm^2. A time-of-flight mass spectrometer is used to measure the ion yield and the distribution of the charge states. Singly charged ions of elements that are presently considered for the use in optical clocks or quantum logic applications could be produced from metallic samples at a rate of the order of magnitude 10^5 ions per pulse. A linear Paul trap was loaded with Th+ ions produced by laser ablation. An overall ion production and trapping efficiency of 10^-7 to 10^-6 was attained. For ions injected individually, a dependence of the capture probability on the phase of the RF field has been predicted. In the experiment this was not observed, presumably because of collective effects within the ablation plume.

Zimmermann, K; Herrera-Sancho, O A; Peik, E

2012-01-01

3

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

Microsoft Academic Search

Direct laser irradiation to an electrostatic probe disturbs the negative ion signals of laser photodetachment (LPD) in helium-hydrogen plasmas, particularly when the electron density is considerably high. In order to analyse the characteristics and production mechanism of ablation signals, laser irradiation experiments were performed on a tungsten surface using helium plasmas. To prevent direct laser irradiation to the electrostatic probe

Shin Kajita; Shinichiro Kado; Satoru Tanaka

2005-01-01

4

Investigation Of Excimer Laser Ablated Y-Ba-Cu-O Superconductors Using Spectroscopy And Ion Probes  

NASA Astrophysics Data System (ADS)

KrF laser ablation of Y-Ba-Cu-O targets has been studied using time resolved visible-uv spectroscopy and ion collector probes. These techniques have allowed the principal luminous species, ablation velocity and extent of ionization in the plume to be deduced. Comparative work using the TEA CCD, laser shows that similar spectral signatures are generated by the plume but that higher electron temperatures may exist because of stronger plasma coupling effects with the long wavelength laser.

Dyer, Peter E.; Greenough, R. D.; Issa, Almoutaz; Key, Phillip H.

1989-04-01

5

Production of fullerene ions by combining of plasma sputtering with laser ablation  

SciTech Connect

We have produced C{sub 60} ion beams by combining plasma sputtering and laser ablation. A C{sub 60} sample was placed in an electron cyclotron resonance type ion source, negatively biased and sputtered by argon plasma. The beam current of C{sub 60}{sup +} decreased rapidly, but it was transiently recovered by a single laser shot that ablates the thin sample surface on the sputtered area. Temporal variations in beam current are reported in response to laser shots repeated at intervals of a few minutes.

Yamada, K., E-mail: yamada.keisuke@jaea.go.jp; Saitoh, Y.; Yokota, W. [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)] [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

2014-02-15

6

Ambient molecular imaging by laser ablation electrospray ionization mass spectrometry with ion mobility separation  

E-print Network

Ambient molecular imaging by laser ablation electrospray ionization mass spectrometry with ion ionization LAESI Ambient ionization Ion mobility separation Mass spectrometry imaging A B S T R A C T Mass, the implementation of ambient ionization techniques for MSI has grown rapidly, enabling operation under native

Vertes, Akos

7

Multidiagnostic analysis of ion dynamics in ultrafast laser ablation of metals over a large fluence range  

NASA Astrophysics Data System (ADS)

The dynamics of ions in ultrafast laser ablation of metals is studied over fluences ranging from the ablation threshold up to ?75 J/cm2 by means of three well-established diagnostic techniques. Langmuir probe, Faraday cup, and spectrally resolved intensified charge coupled device imaging simultaneously monitored the ions produced during ultrafast laser ablation of a pure copper target with 800 nm, ?50 fs, Ti: Sapphire laser pulses. The fluence dependence of ion yield is analyzed, resulting in the observance of three different regimes. The specific ion yield shows a maximum at about 4-5 J/cm2, followed by a gradual reduction and a transition to a high-fluence regime above ?50 J/cm2. The fluence dependence of the copper ions angular distribution is also analyzed, observing a gradual increase in forward-peaking of Cu ions for fluences up to ?10 J/cm2. A broader ion component is observed at larger angles for fluences larger than ?10 J/cm2. Finally, an experimental characterization of the ionic angular distribution for several metallic targets (Mg, Al, Cr, Fe, Cu, and W) is carried out at a relatively high fluence of ?66 J/cm2. Interestingly, the ion emission from the volatile metals shows a narrow, forward-peaked distribution, and a high peak ion yield compared to the refractory metals. Moreover, the width of ionic angular distributions presents a striking correlation with the peak ion yield.

Anoop, K. K.; Polek, M. P.; Bruzzese, R.; Amoruso, S.; Harilal, S. S.

2015-02-01

8

Laser Ablation Electrodynamic Ion Funnel for In Situ Mass Spectrometry on Mars  

NASA Technical Reports Server (NTRS)

A front-end instrument, the laser ablation ion funnel, was developed, which would ionize rock and soil samples in the ambient Martian atmosphere, and efficiently transport the product ions into a mass spectrometer for in situ analysis. Laser ablation creates elemental ions from a solid with a high-power pulse within ambient Mars atmospheric conditions. Ions are captured and focused with an ion funnel into a mass spectrometer for analysis. The electrodynamic ion funnel consists of a series of axially concentric ring-shaped electrodes whose inside diameters (IDs) decrease over the length of the funnel. DC potentials are applied to each electrode, producing a smooth potential slope along the axial direction. Two radio-frequency (RF) AC potentials, equal in amplitude and 180 out of phase, are applied alternately to the ring electrodes. This creates an effective potential barrier along the inner surface of the electrode stack. Ions entering the funnel drift axially under the influence of the DC potential while being restricted radially by the effective potential barrier created by the applied RF. The net result is to effectively focus the ions as they traverse the length of the funnel.

Johnson, Paul V.; Hodyss, Robert P.; Tang, Keqi; Smith, Richard D.

2012-01-01

9

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma  

SciTech Connect

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

Ikeda, Shunsuke, E-mail: shunsuke.ikeda@riken.jp; Sekine, Megumi [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan) [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan); Riken, Wako, Saitama (Japan); Romanelli, Mark [Cornell University, Ithaca, New York 14850 (United States)] [Cornell University, Ithaca, New York 14850 (United States); Cinquegrani, David [University of Michigan, Ann Arbor, Michigan 48109 (United States)] [University of Michigan, Ann Arbor, Michigan 48109 (United States); Kumaki, Masafumi [Waseda University, Shinjuku, Tokyo (Japan)] [Waseda University, Shinjuku, Tokyo (Japan); Fuwa, Yasuhiro [Kyoto University, Uji, Kyoto (Japan)] [Kyoto University, Uji, Kyoto (Japan); Kanesue, Takeshi; Okamura, Masahiro [Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Brookhaven National Laboratory, Upton, New York 11973 (United States); Horioka, Kazuhiko [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan)] [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan)

2014-02-15

10

Theory of electron-ion energy transfer applied to laser ablation  

SciTech Connect

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

Vorberger, J.; Gericke, D. O. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2012-07-30

11

Infrared laser bone ablation  

Microsoft Academic Search

The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and COâ, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig

Roger C. Nuss; Richard L. Fabian; Rajabrata Sarkar; Carmen A. Puliafito

1988-01-01

12

Structural features of laser ablation particulate from Si target, as revealed by focused ion beam technology  

NASA Astrophysics Data System (ADS)

Heterogeneity in laser-induced particle structures was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of individual particles micro-machined using focused ion beam (FIB). The primary particle size distribution spanned over three orders of magnitude, i.e., in the range 10 nm-10 ?m with few larger secondary objects. The particulate larger than 0.5 ?m often resulted from particle-particle aggregation, mostly upon a spherical core, seldom in chain-like structures. The core of these fractal aggregates was found to be polycrystalline. The heterogeneity of the particles with respect to structure and chemistry is surely of importance for elemental analysis using laser ablation as sample introduction technique.

Bleiner, D.; Gasser, P.

13

Understanding plume splitting of laser ablated plasma: A view from ion distribution dynamics  

SciTech Connect

Plume splitting in low-pressure ambient air was understood in view of ion distribution dynamics from the laser ablated Al plasma (1064 nm 0.57 J/mm{sup 2}) by combining fast photography and spatially resolved spectroscopy. In the beginning, the spectral lines were mainly from the Al III ion. Then, the Bragg peak in stopping power of the ambient gas to Al III could be the dominant reason for the enhanced emission from the fast moving part, and the recombination of Al III to Al I-II ions near the target surface was response to the radiations from the slow moving/stationary part. As the ambient gas pressure increased, stopping distances of the Al III decreased, and radiation from the air ions became pronounced. The laser shadowgraph image at 1100 Pa indicated that the shock wave front located between the fast moving and slow moving parts. Electron densities of the fast moving plasma, which peaked at the plasma front, were on the order of 10{sup 16} cm{sup ?3}, and the electron temperatures were 2–3 eV.

Wu, Jian; Li, Xingwen; Wei, Wenfu; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Shaanxi 710049 (China)] [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Shaanxi 710049 (China)

2013-11-15

14

150 MeV Au ion induced modification of Si nanoparticles prepared by laser ablation  

NASA Astrophysics Data System (ADS)

We have investigated in detail the effects of 150 MeV Au ions irradiation on Si nanoparticles (NPs) synthesized by picosecond laser ablation of single crystal Si wafers in acetone. The formation of Si NPs was confirmed by Raman spectroscopy, transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) measurements. The size distribution of synthesized NPs was found to be in the range of few nm to 80 nm. These samples were then irradiated with 150 MeV Au ions at various fluences ranging from 1 × 1013 to 1 × 1014 ions/cm2. The effects of ion irradiation on the size and shape of Si NPs were further investigated using TEM, FESEM and micro Raman spectroscopy. From TEM data, we have noticed the reduction in size of NPs with increasing ion irradiation fluence. Furthermore with the increasing fluence we also observed the nucleation of 6-9 nm NPs in the vicinity of bigger NPs where there were no such NPs before ion irradiation. The increase in the FWHM of the Raman peak and its shift towards lower wave number side also suggests that the decrease in NP size is a result of increase in the fluence of irradiation.

Saikiran, V.; Vendamani, V. S.; Hamad, S.; Nageswara Rao, S. V. S.; Venugopal Rao, S.; Pathak, A. P.

2014-08-01

15

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

Microsoft Academic Search

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

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

2008-01-01

16

Ablation of solids by femtosecond lasers: Ablation mechanism and ablation thresholds for metals and dielectrics  

Microsoft Academic Search

The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion

E. G. Gamaly; A. V. Rode; B. Luther-Davies; V. T. Tikhonchuk

2002-01-01

17

Surface-plasmon-ion interaction in laser ablation of ions from a surface  

NASA Astrophysics Data System (ADS)

Experimental work by Shea and Compton suggests that Ag+ ions emitted from a roughened Ag surface irradiated by a nanosecond or picosecond laser beam may absorb the full energy of the Ag surface plasmon (SP). We have modeled this process as an inverse bremsstrahlung-type absorption of the SP quantum by an Ag+ ion which undergoes a collision with the surface. We estimate the absorption probability and find it to be consistent with the Shea-Compton results.

Ritchie, R. H.; Manson, J. R.; Echenique, P. M.

1994-01-01

18

Time-of-flight detection of monoatomic ions generated by femtosecond laser ablation from large molecules  

NASA Astrophysics Data System (ADS)

Single-shot femtosecond laser ablation (fsLA) was applied to large molecules to analyze elemental composition through out wide range of mass-to-charge ratio. Molecular samples such as Eu-DNA and cosmetic powders were atomized and ionized simultaneously by the single-shot fsLA and positive atomic ions were detected using a reflectron time-of-flight (TOF) mass spectrometer. The ratios among the signal intensity of the detected stable isotopes including 151,153Eu and 182-184,186W were consistent with the respective natural abundances of the isotopes. The results demonstrate the feasibility of the fsLA-TOF method as a high-throughput analytical technique for elemental microanalysis of large molecular samples in small quantities.

Kato, Toshiyuki; Kobayashi, Tohru; Kurata-Nishimura, Mizuki; Okamura-Oho, Yuko; Sano, Takuma; Oyama, Rieko; Matsumura, Yonehiro; Yamamoto, Hiroshi; Hayashizaki, Yoshihide; Matsuo, Yukari; Kawai, Jun

2008-03-01

19

Femtosecond laser ablation of copper  

Microsoft Academic Search

In recent years, femtosecond (fs) laser ablation has attracted much interest in both basic and applied physics, mainly because of its potential application in micromachining and pulsed laser deposition. Ultrashort laser ablation have the capability to ablate materials precisely with little or no collateral damage, even with materials that are impervious to laser energy from conventional pulsed lasers. The extreme

Yeow-Whatt Goh; Yong-Feng Lu; Ming-Hui Hong; Tow Chong Chong

2003-01-01

20

Infrared Laser Ablation Atmospheric Pressure Photoionization Mass Spectrometry  

E-print Network

Infrared Laser Ablation Atmospheric Pressure Photoionization Mass Spectrometry Anu Vaikkinen, Washington, DC 20052, United States *S Supporting Information ABSTRACT: In this paper we introduce laser ablation atmo- spheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass

Vertes, Akos

21

Laser ablation of concrete.  

SciTech Connect

Laser ablation is effective both as an analytical tool and as a means of removing surface coatings. The elemental composition of surfaces can be determined by either mass spectrometry or atomic emission spectroscopy of the atomized effluent. Paint can be removed from aircraft without damage to the underlying aluminum substrate, and environmentally damaged buildings and sculptures can be restored by ablating away deposited grime. A recent application of laser ablation is the removal of radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on concrete samples using a high power pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied on various model systems consisting of Type I Portland cement with varying amounts of either fine silica or sand in an effort to understand the effect of substrate composition on ablation rates and mechanisms. A sample of non-contaminated concrete from a nuclear power plant was also studied. In addition, cement and concrete samples were doped with non-radioactive isotopes of elements representative of cooling waterspills, such as cesium and strontium, and analyzed by laser-resorption mass spectrometry to determine the contamination pathways. These samples were also ablated at high power to determine the efficiency with which surface contaminants are removed and captured. The results show that the neat cement matrix melts and vaporizes when little or no sand or aggregate is present. Surface flows of liquid material are readily apparent on the ablated surface and the captured aerosol takes the form of glassy beads up to a few tens of microns in diameter. The presence of sand and aggregate particles causes the material to disaggregate on ablation, with intact particles on the millimeter size scale leaving the surface. Laser resorption mass spectrometric analysis showed that cesium and potassium have similar chemical environments in the matrix, as do strontium and calcium.

Savina, M.

1998-10-05

22

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

23

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

24

Construction of waveguiding structures in potassium lithium tantalate niobate crystals by combined laser ablation and ion implantation  

NASA Astrophysics Data System (ADS)

A generic methodology for constructing complex integrated electro-optic circuits in waveguided configurations is presented. The method is based on combining two techniques, "laser ablation" and "refractive index engineering by ion implantations." The constructed circuits are side-cladded by air trenches that were produced using laser ablation and bottom-cladded by a layer with a reduced refractive index which is generated through the implantation of He+ ions. This fabrication technique enables the construction of circular structures with complex geometry featuring small radii of curvature, and further can be employed to construct microfluidic channels on the same substrate. The research demonstrates waveguides in both linear and circular configurations that were constructed in a potassium lithium tantalate niobate (KLTN) substrate using the aforementioned method, proving that this substrate is a suitable candidate for use in creating laboratories-on-a-chip with multifunctional capabilities. The proposed techniques used in the research are generic and applicable to a wide range of substrates.

Yashar, Ayelet Badichi; Ilan, Harel; Agranat, Aharon J.

2015-02-01

25

LASER ABLATION STUDIES OF CONCRETE  

EPA Science Inventory

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

26

OCDR guided laser ablation device  

DOEpatents

A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

Dasilva, Luiz B. (Danville, CA); Colston, Jr., Bill W. (Livermore, CA); James, Dale L. (Tracy, CA)

2002-01-01

27

Subcellular analysis by laser ablation electrospray ionization mass spectrometry  

DOEpatents

In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

2014-12-02

28

Laser ablation studies of concrete  

Microsoft Academic Search

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

M. Savina; Z. Xu; Y. Wang; C. Reed; M. Pellin

1999-01-01

29

Direct chemical-analysis of uv laser-ablation products of organic polymers by using selective ion monitoring mode in gas-chromatography mass-spectrometry  

USGS Publications Warehouse

Trace quantities of laser ablated organic polymers were analyzed by using commercial capillary column gas chromatography/mass spectrometry; the instrument was modified so that the laser ablation products could be introduced into the capillary column directly and the constituents of each peak in the chromatogram were identified by using a mass spectrometer. The present study takes advantage of the selective ion monitoring mode for significantly improving the sensitivity of the mass spectrometer as a detector, which is critical in analyzing the trace quantities and confirming the presence or absence of the species of interest in laser ablated polymers. The initial composition of the laser ablated polymers was obtained by using an electron impact reflectron time-of-flight mass spectrometer and the possible structure of the fragments observed in the spectra was proposed based on the structure of the polymers.

Choi, Y.; Lee, H.W.; Fountain, S.T.; Lubman, D.M.

1994-01-01

30

Development of the C(6+) laser ablation ion source for the KEK digital accelerator.  

PubMed

A laser ion source that provides a fully ionized carbon ion beam is under joint development at the High Energy Accelerator Research Organization and Brookhaven National Laboratory. Long-pulse (6 ns) and short-pulse (500 ps) laser systems were tested by using them to irradiate a graphite target. Notable differences between the systems were observed in these experiments. Preliminary experimental results, such as the charge-state spectrum, beam intensity, and stability, are discussed. PMID:24593627

Munemoto, Naoya; Takayama, Ken; Takano, Susumu; Okamura, Masahiro; Kumaki, Masahumi

2014-02-01

31

Development of the C{sup 6+} laser ablation ion source for the KEK digital accelerator  

SciTech Connect

A laser ion source that provides a fully ionized carbon ion beam is under joint development at the High Energy Accelerator Research Organization and Brookhaven National Laboratory. Long-pulse (6 ns) and short-pulse (500 ps) laser systems were tested by using them to irradiate a graphite target. Notable differences between the systems were observed in these experiments. Preliminary experimental results, such as the charge-state spectrum, beam intensity, and stability, are discussed.

Munemoto, Naoya, E-mail: munemoto.n.ad@m.titech.ac.jp [Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503 (Japan) [Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503 (Japan); High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Takayama, Ken [Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503 (Japan) [Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503 (Japan); High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Graduate University for Advanced Studies, Hayama, Miura, Kanagawa 240-8550 (Japan); Takano, Susumu [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)] [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Okamura, Masahiro [Brookhaven National Laboratory, Upton, New York 11973-5000 (United States) [Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kumaki, Masahumi [RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan) [RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-0072 (Japan)

2014-02-15

32

PROCEEDINGS288 ---c..*. LASER ABLATION: I:`.  

E-print Network

AIP I CONFERENCE PROCEEDINGS288 ---c..*. . LASER ABLATION: I:`. MECHANEMS ABSTRACT A one dimensional hydrodynamic' model of laser ablation and plume breakdown is presented. The en for KrF and XeCl excimer laser ablation of YBa,Cu30Y_xtargets in vacuum, XeF excimer laser ablation

Vertes, Akos

33

Multiple target laser ablation system  

DOEpatents

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

Mashburn, Douglas N. (Knoxville, TN)

1996-01-01

34

Multiple target laser ablation system  

DOEpatents

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

Mashburn, D.N.

1996-01-09

35

Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation  

SciTech Connect

The ablation plume dynamics arising from ablation of silver with a 500 fs, 248 nm laser at {approx}2 J cm{sup -2} has been studied using angle-resolved Langmuir ion probe and thin film deposition techniques. For the same laser fluence, the time-of-flight ion signals from femtosecond and nanosecond laser ablation are similar; both show a singly peaked time-of-flight distribution. The angular distribution of ion emission and the deposition are well described by the adiabatic and isentropic model of plume expansion, though distributions for femtosecond ablation are significantly narrower. In this laser fluence regime, the energy efficiency of mass ablation is higher for femtosecond pulses than for nanosecond pulses, but the ion production efficiency is lower.

Toftmann, B.; Schou, J. [DTU Fotonik, Riso Campus, DK-4000 Roskilde (Denmark); Doggett, B.; Budtz-Jorgensen, C.; Lunney, J. G. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland)

2013-02-28

36

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

37

Plume collimation for laser ablation electrospray ionization mass spectrometry  

DOEpatents

In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

Vertes, Akos; Stolee, Jessica A.

2014-09-09

38

Resonant laser ablation: Mechanisms and applications  

SciTech Connect

Ever since the first report of laser action, it has been recognized that laser ablation (evaporation/volatilization) may provide a useful sampling mechanism for chemical analysis. In particular, laser ablation is rapidly gaining popularity as a method of sample introduction for mass spectrometry. While most laser ablation/mass spectrometry has been performed with fixed frequency lasers operating at relatively high intensities/fluences ({ge}10{sup 8} W/cm{sup 2}, {ge}1 J/cm{sup 2}), there has been some recent interest in the use of tunable lasers to enhance the ionization yield of selected components in an analytical sample. This process has been termed resonant laser ablation (RLA), and typically relies on irradiation of a sample in a mass spectrometer with modest intensity laser pulses tuned to a one- or two-photon resonant transition in the analyte of interest. Potential advantages of RLA include: (1) simplification of the mass spectrum, by enhancement of signal from the analyte of interest; (2) improvement of the absolute detection limits by improving the ionization efficiency, and (3) improvement in relative sensitivity. The sensitivity enhancement results from reduction of spurious signal, and accompanying noise, in the detection channel. This spurious signal may be due to bleed through from adjacent mass channels, or from isobaric interferences. RLA tends to produce higher mass resolution because of minimal spatial spread in the ion source and small space charge effects. In this manuscript we present a survey of RLA attributes and applications.

Anderson, J.E.; Bodla, R.; Eiden, G.C.; Nogar, N.S.; Smith, C.H.

1994-06-01

39

Femtosecond laser ablation of copper  

NASA Astrophysics Data System (ADS)

In recent years, femtosecond (fs) laser ablation has attracted much interest in both basic and applied physics, mainly because of its potential application in micromachining and pulsed laser deposition. Ultrashort laser ablation have the capability to ablate materials precisely with little or no collateral damage, even with materials that are impervious to laser energy from conventional pulsed lasers. The extreme intensities and short timescale at which ultrashort pulsed lasers operate differentiate them from other lasers such as nanosecond laser. In this work, we investigate the expansion dynamics of Cu (copper) plasma generated by ultrashort laser ablation of pure copper targets by optically examining the plasma plume. Time-integrated optical emission spectroscopy measurements by using intensified charged couple detector array (ICCD) imaging were used to detect the species present in the plasma and to study the laser-generated plasma formation and evolution. Temporal emission profiles are measured. Our interest in the dynamics of laser-generated copper plasma arises from the fact that copper has been considered as a substitute for Aluminum (Al) interconnects/metallization in ULSI devices (for future technology). It is important to know the composition and behavior of copper plasma species for the understanding of the mechanisms involved and optimizing the micro-machining processes and deposition conditions.

Goh, Yeow-Whatt; Lu, Yong-Feng; Hong, Ming-Hui; Chong, Tow Chong

2003-02-01

40

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments  

PubMed Central

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: Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion. 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. 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

41

Femtosecond Laser Ablation: Fundamentals and Applications  

E-print Network

Chapter 6 Femtosecond Laser Ablation: Fundamentals and Applications Sivanandan S. Harilal, Justin R of laser ablation process using ultrashort laser pulses are not still fully understood. Pulse duration in the sample lattice. This results in dif- ferent laser ablation and heat dissipation mechanisms as compared

Harilal, S. S.

42

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

43

Laser ablation based fuel ignition  

DOEpatents

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

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

1998-06-23

44

Lee, C-T A Laser Ablation Data Reduction 2006 LASER ABLATION ICP-MS: DATA  

E-print Network

Lee, C-T A Laser Ablation Data Reduction 2006 1 LASER ABLATION ICP-MS: DATA REDUCTION Cin-Ty A. Lee 24 September 2006 Analysis and calculation of concentrations Laser ablation analyses are done in time by turning on the laser and ablating the sample, generating a time-dependent signal (Fig. 1). Measurements

Lee, Cin-Ty Aeolus

45

Laser ablation studies of concrete  

SciTech Connect

Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. The authors present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied using cement and high density concrete as targets. Ablation efficiency and material removal rates were determined as functions of irradiance and pulse overlap. Doped samples were also ablated to determine the efficiency with which surface contaminants were removed and captured in the effluent. The results show that the cement phase of the material melts and vaporizes, but the aggregate portion (sand and rock) fragments. The effluent consists of both micron-size aerosol particles and chunks of fragmented aggregate material. Laser-induced optical emission spectroscopy was used to analyze the surface during ablation. Analysis of the effluent showed that contaminants such as cesium and strontium were strongly segregated into different regions of the particle size distribution of the aerosol.

Savina, M.; Xu, Z.; Wang, Y.; Reed, C.; Pellin, M.

1999-10-20

46

Impact of laser wavelength on the emission of electrons and ions from thin gold films during femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

This experimental study supports computational evidence that the excitation of d-band electrons have a significant impact on the material response of gold to an ultrashort laser pulse. A voltage biased Langmuir probe was used to detect the electron and positive ion emission from a 20 nm thick Au film at 343 nm, 515 nm and 1030 nm laser wavelengths. The laser wavelengths used provided photon energies above and below the interband transition threshold (ITT) for d-band excitation in gold (1.9 eV). Variations in optical properties of the Au film at different laser wavelengths were accounted for to ensure that comparisons were made at equal values of absorbed fluences. Data showed a significantly higher number of electrons emitted over a longer period when the energy of the incident photons exceeded the ITT. The electronic current generated at the probe indicated that the first electrons detected were primarily emitted via multiphoton photoemission. Electrons were also detected at later times when the photon energy exceeded the ITT and this was attributed to thermionic emission. The current generated from the positive ion emission was significantly lower than for electron emission, but indicated the formation of a plasma at a threshold fluence that increases with decreasing photon energy.

Haustrup, N.; O'Connor, G. M.

2014-05-01

47

Dynamics of laser ablation plume penetration through low pressure background gases  

E-print Network

Dynamics of laser ablation plume penetration through low pressure background gases David B; accepted for publication 2 May 1995 The dynamics of laser-ablated yttrium plume propagation through . During expansion into low-pressure background gases, the ion flux in the laser ablation plasma plume

Geohegan, David B.

48

Picosecond laser ablation for silicon micro fuel cell fabrication  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

49

Simulation of Double-Pulse Laser Ablation  

SciTech Connect

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

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

2010-10-08

50

Plume dynamics in femtosecond laser ablation of metals  

SciTech Connect

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

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

2010-10-08

51

Subpicosecond UV laser ablation of metals  

Microsoft Academic Search

Laser ablation of Nickel, Copper, Molybdenum, Indium, Tungsten and Gold by short ultraviolet laser pulses (0.5 ps, 248 nm) in vacuum is reported for the first time. For Nickel and Indium, ablation is also studied in air to demonstrate the influence of the ambient atmosphere. Metal ablation in air is significantly less efficient than in vacuum due to redeposition of

S. Preuss; A. Demchuk; M. Stuke

1995-01-01

52

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

53

Precise laser ablation with ultrashort pulses  

Microsoft Academic Search

Laser ablation of solid targets by Ti:sapphire laser radiation is studied. The targets are irradiated by 150 fs–5 ns laser pulses with a fluence in the range of several J\\/cm2. Measurements on the ablation depth yield an effective penetration depth higher than the optical penetration depth. Advantages and potentials of sub-picosecond laser radiation for the ablation and for the microstructuring

C. Momma; S Nolte; B N. Chichkov; F v. Alvensleben; A Tünnermann

1997-01-01

54

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

55

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.

56

Prompt electrons driving ion acceleration and formation of a two temperatures plasma in nanosecond laser-ablation domain  

E-print Network

We present the results of an experiment on plasma generation via laser ablation at 10^12 W/cm^2 of power intensity and in a nanosecond domain. Prompt electrons emission and complex plasma plume fragmentation were simultaneously observed for the first time in this laser intensity regime, along with a double electron temperature inside the plasma bulk surviving for a long time to the plume expansion. 1D PIC simulations are in agreement with experimental data as long as the emission of initial prompt electrons is considered. This assumption results to be the key to explain all the other experimental evidences.

Mascali, D; Gambino, N; Pluchino, A; Anzalone, A; Musumeci, F; Rapisarda, A; Spitaleri, A

2011-01-01

57

Endometrial ablation  

MedlinePLUS

Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

58

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 active surveillance and radical therapy. Focal laser ablation (FLA) could be one surgical method. Keywords: Prostate cancer focal laser ablation, thermal damage, bioheat transfer

Paris-Sud XI, Université de

59

Pulsed infrared laser ablation and clinical applications  

NASA Astrophysics Data System (ADS)

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

Chan, Kin Foong

60

PULSED LASER ABLATION OF CEMENT AND CONCRETE  

EPA Science Inventory

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

61

Ultrafast laser ablation of metals with a pair of collinear laser pulses  

SciTech Connect

We investigated the process of ultrafast laser ablation of metallic targets induced by a pair of identical laser pulses, with either p or s polarizations, temporally delayed from {approx_equal}1 ps to a few nanoseconds. We used fast ion probe diagnostics to characterize the ion plume at the moderate laser intensity ({approx_equal}10{sup 12} W/cm{sup 2}) typically employed in ultrafast laser deposition and material processing. We observed a consistent time-correlated enhancement of the ion yield and velocity, which lends itself to an interesting and useful method for manipulating ablation plasma characteristics. The mechanisms producing this feature are also discussed.

Amoruso, S.; Bruzzese, R.; Wang, X.; Xia, J. [Coherentia CNR-INFM and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy)

2008-11-10

62

Numerical simulation of pulsed laser ablation in air  

Microsoft Academic Search

Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric

Bukuk Oh; Dongsik Kim; Wonseok Jang; Bosung Shin

2003-01-01

63

Laser ablation and micromachining with ultrashort laser pulses  

Microsoft Academic Search

The mechanisms of ultrashort-pulse laser ablation of materials are discussed, and the differences to that of long laser pulses are emphasized. Ultrashort laser pulses offer both high laser intensity and precise laser-induced breakdown threshold with reduced laser fluence. The ablation of materials with ultrashort pulses has a very limited heat-affected volume. The advantages of ultrashort laser pulses are applied in

X. Liu; D. Du; G. Mourou

1997-01-01

64

Direct coupling of a laser ablation cell to an AMS  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

65

Nanoparticle generation and transport resulting from femtosecond laser ablation of ultrathin metal films: Time-resolved measurements  

E-print Network

Nanoparticle generation and transport resulting from femtosecond laser ablation of ultrathin metal-threshold backside laser ablation of 2­20 nm-thick Pt films deposited on fused silica substrates was found to produce to be nanoparticles.4­9 In most cases, however, there still remains an ion plasma component10 to the laser ablation

Zhigilei, Leonid V.

66

Resonant laser ablation: Applications and mechanistic aspects  

SciTech Connect

Ever since the first report of laser action, it has been recognized that laser ablation (evaporation/volatilization) may provide a useful sampling mechanism for chemical analysis. In particular, laser ablation is rapidly gaining popularity as a method of sample introduction for mass spectrometry. Since its original description, numerous research papers and review articles have appeared on various aspects of laser mass spectrometry. While most laser ablation/mass spectrometry has been performed with fixed frequency lasers operating at relatively high intensities/fluences ({ge} 10{sup 8} W/cm{sup 2}, {ge} 1 J/cm{sup 2}), there has been some recent interest in the use of low-power tunable lasers to ablate and resonantly ionize selected components in the ablation plume. This process has been termed resonant laser ablation (RLA). The authors report here on aspects of RLA behavior for a number of metals, alloys and thin films. The versatility of RLA is demonstrated, with results on a variety of samples and in several mass spectrometers. In addition, the application to depth profiling of thin films and multilayers is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation is discussed.

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

1995-12-31

67

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

68

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 introduction to the process of laser ablation, its simulation by the molecular dynamics method, and results be simulated which form during laser ablation. Laser ablation is a process where material is removed from

Roth, Johannes

69

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

SciTech Connect

Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

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

2004-03-23

70

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

SciTech Connect

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

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

2012-10-15

71

IR laser ablation of dental enamel  

NASA Astrophysics Data System (ADS)

An overview of the basic mechanisms of IR laser ablation of dental enamel is presented. Enamel is a highly structured tissue consisting of an heterogeneous distribution of water, mineral, protein and lipid. Absorption bands of water and carbonated hydroxyapatite can be selectively targeted from 2.7 to 11-micrometer via several laser wavelengths. Mechanistic differences in the nature of ablation and the varying surface morphology produced can be explained by the microstructure of the tissue. Suggested criteria for the choice of the optimum laser parameters for clinical use, the influence of plasma shielding and the role of exogenous water on the mechanism of ablation are discussed.

Fried, Daniel

2000-03-01

72

Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency  

NASA Astrophysics Data System (ADS)

The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3/J when the laser fluence was set at 6.51 J/cm2. For enamel, the maximum ablation efficiency was 0.009 mm3/J at a fluence of 7.59 J/cm2. Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value.

Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

2015-02-01

73

Femtosecond laser ablation of the stapes  

PubMed Central

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. PMID:19405768

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

2014-01-01

74

PROCEEDINGS288 -;-m__c_ LASER ABLATION  

E-print Network

TAIP CONFERENCE PROCEEDINGS288 -;-m__c_ LASER ABLATION: MECHANISMSAND ..'m . . APPLICATIONS States of America. #12;Extending Laser Fusion Concepts Into the Lower Power ( 5 1 GW Heights, NY 10598 USA Claude PHIPPS Chemical and Laser Science Div., Los Alamos National Lab. Los Alamos

Vertes, Akos

75

Retained Foreign Body After Laser Ablation  

PubMed Central

Laser ablation for varicose veins is a common practice, and postoperative complications may happen. A retained foreign body could be left accidently in the treated leg. It is rarely reported in literature. We herein describe two cases of retained foreign body during the laser ablation for varicose veins. One patient with varicose veins received laser therapy 5 years earlier, and had experienced discomfort and pain. After investigation, an overlooked sheath fragment was removed surgically from the leg. Another patient with varicose veins had discomfort after laser ablation for 8 days, and has been asymptomatic after the removal of the retained foreign body in the leg. The essential preventive approach include to pinpoint the site of the tip of fiberoptic laser fiber and pull 1 to 2 cm of the sheath out of the patient, then withdrawal the fiberoptic fiber and sheath simultaneously. A white flash light in the trunk of the fiberoptic laser fiber is an important warning signal of an erroneous manipulation during the operation. The surgeon should routinely check the intact sheath and fiberoptic fiber after laser ablation. In conclusion, retained foreign body can be prevented by following some practical tips during laser ablation. PMID:23294067

Ren, Shiyan; Liu, Peng; Wang, Wei; Yang, Yuguan

2012-01-01

76

Dual beam optical system for pulsed laser ablation film deposition  

DOEpatents

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

Mashburn, D.N.

1996-09-24

77

Dual beam optical system for pulsed laser ablation film deposition  

DOEpatents

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target.

Mashburn, Douglas N. (Knoxville, TN)

1996-01-01

78

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

Microsoft Academic Search

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

Peter. Arrowsmith

1987-01-01

79

Laser Ablation Electrospray Ionization for Atmospheric Pressure, in Vivo, and Imaging Mass  

E-print Network

Laser Ablation Electrospray Ionization for Atmospheric Pressure, in Vivo, and Imaging Mass changes in organisms with high specificity. Here we report on a novel combination of infrared laser ablation with electrospray ionization (LAESI) as an ambient ion source for mass spectrometry. As a result

Vertes, Akos

80

Ultrashort-pulse laser ablation of nanocrystalline aluminum  

SciTech Connect

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

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

2011-12-01

81

Effects of Laser Wavelength on Ablator Testing  

NASA Technical Reports Server (NTRS)

Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

White, Susan M.

2014-01-01

82

Infrared Laser Ablation Sample Transfer for MALDI and Electrospray  

Microsoft Academic Search

We have used an infrared laser to ablate materials under ambient conditions that were captured in solvent droplets. The droplets\\u000a were either deposited on a MALDI target for off-line analysis by MALDI time-of-flight mass spectrometry or flow-injected into\\u000a a nanoelectrospray source of an ion trap mass spectrometer. An infrared optical parametric oscillator (OPO) laser system at\\u000a 2.94 ?m wavelength and approximately

Sung-Gun Park; Kermit King Murray

2011-01-01

83

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

84

Cavity formation in a liquid Sn droplet driven by laser ablation pressure for an extreme ultraviolet light source target  

E-print Network

Cavity formation in a liquid Sn droplet driven by laser ablation pressure for an extreme.10,11 However, these cavities are typically machined or laser-ablated (using many laser pulses) on solid planar in liquid Sn droplets for the purpose of increasing ion density from Sn plasma produced by a CO2 laser

Najmabadi, Farrokh

85

Ultraviolet-laser ablation of skin  

Microsoft Academic Search

The authors report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding

R. Linsker; J. J. Wynne; A. Torres; R. G. Geronemus

1985-01-01

86

Molecular dynamics simulation of ultrafast laser ablation of fused silica  

E-print Network

Molecular dynamics simulation of ultrafast laser ablation of fused silica C Cheng, A Q Wu and X Xu-mail: xxu@ecn.purdue.edu Abstract. Ultrafast laser ablation of fused silica is studied using molecular that ultrafast laser is capable of microscale fabrication of glass. The process of "laser ablation

Xu, Xianfan

87

Laser ablation in analytical chemistry—a review  

Microsoft Academic Search

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

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

2002-01-01

88

Polymers designed for laser ablation-inuence of photochemical properties  

E-print Network

Polymers designed for laser ablation-in¯uence of photochemical properties T. Lipperta,* , J applications for lasers have been developed. Nowadays, laser ablation is used e.g. in medicine [2], art conservation [3], and thin ®lm deposition [4]. Laser ablation of polymers was ®rst reported in 1982 [5

Dickinson, J. Thomas

89

Diagnostics and applications of ultrashort pulsed laser ablation /  

E-print Network

Diagnostics and applications of ultrashort pulsed laser ablation / deposition 694220044 #12 by pulsed laser ablation focused on the quality of thin film by pulsed laser deposition. Direct measurements of plasma plume in pulsed laser ablation. In this work, we have designed and constructed Eizel lens and time

90

High-throughput cell and tissue analysis with enhanced molecular coverage by laser ablation electrospray ionization mass spectrometry using ion mobility separation.  

PubMed

Ambient ionization methods, such as laser ablation electrospray ionization (LAESI), facilitate the direct analysis of unperturbed cells and tissues in their native states. However, the lack of a separation step in these ionization techniques results in limited molecular coverage due to interferences, ion suppression effects, and the lack of ability to differentiate between structural isomers and isobaric species. In this contribution, LAESI mass spectrometry (MS) coupled with ion mobility separation (IMS) is utilized for the direct analysis of protein mixtures, megakaryoblast cell pellets, mouse brain sections, and Arabidopsis thaliana leaves. We demonstrate that the collision cross sections of ions generated by LAESI are similar to the ones obtained by ESI. In various applications, LAESI-IMS-MS allows for the high-throughput separation and mass spectrometric detection of biomolecules on the millisecond time scale with enhanced molecular coverage. For example, direct analysis of mouse brain tissue without IMS had yielded ?300 ionic species, whereas with IMS over 1?100 different ions were detected. Differentiating between ions of similar mass-to-charge ratios with dissimilar drift times in complex biological samples removes some systematic distortions in isotope distribution patterns and improves the fidelity of molecular identification. Coupling IMS with LAESI-MS also expands the dynamic range by increasing the signal-to-noise ratio due to the separation of isobaric or other interfering ionic species. We have also shown that identification of potential biomarkers by LAESI can be enhanced by using the drift times of individual ions as an additional parameter in supervised orthogonal projections to latent structures discriminant analysis. Comparative analysis of drift time versus mass-to-charge ratio plots was performed for similar tissue samples to pinpoint significant metabolic differences. PMID:24684249

Shrestha, Bindesh; Vertes, Akos

2014-05-01

91

Ablation de matériaux par laser femtoseconde  

NASA Astrophysics Data System (ADS)

L'ablation de métaux par laser impulsionnel ultrabref (femtoseconde) est étudiée en analysant les cratères par microscopie optique. La profondeur du cratère a été mesurée en fonction du nombre d'impulsions et de la fluence. Les résultats sont comparés à un modèle analytique décrivant l'interaction laser-matière en régime femtoseconde.

Bruneau, S.; Hermann, J.; Itina, T.; Sentis, M.; Semerok, A.; Marine, W.

2003-06-01

92

Langmuir probe study of laser ablation plume dynamics  

Microsoft Academic Search

For many applications of pulsed laser ablation it is necessary to have an understanding of the expansion dynamics of the ablation plume both in vacuum and in low pressure gases. Knowledge of the ablation plume hydrodynamics can also contribute to the understanding of the laser ablation process. In this paper we will consider some of the existing theoretical models of

James G. Lunney; Brendan Doggett

2006-01-01

93

Femtosecond laser ablation properties of borosilicate glass  

SciTech Connect

We study the femtosecond laser ablation properties of borosilicate glass using atomic force microscopy and laser pulses of 200 fs duration, centered at 780 nm wavelength. We show that both single-shot and multishot ablation threshold fluences can be determined by studying the diameter and the depth of single-shot ablated craters. The linear relationship between the square of the crater diameter and the logarithm of the laser fluence in the form of D{sup 2}=2w{sub 0}{sup 2}ln(F{sub 0}/F{sub th}{sup N=1}) provides the single-shot ablation threshold, F{sub th}{sup N=1}, whereas the linear relationship between the ablation depth and the logarithm of laser fluence in the form of h{sub a}={alpha}{sub eff}{sup -1}ln(F{sub 0}/F{sub th}{sup N>1}) provides the multishot ablation threshold, F{sub th}{sup N>1}. The results depict a multishot ablation threshold of {approx_equal}1.7 J/cm{sup 2} independent of the atmospheric conditions. The slopes of the linear fits also provide a precise estimate of the beam radius at the surface, w{sub 0}{approx_equal}5.9 {mu}m, and the ''effective optical penetration depth,'' {alpha}{sub eff}{sup -1}{approx_equal}238 nm in air. The method is systematic, provides results that are consistent with the literature, and eliminates uncertainties because of instrument sensitivities. We also show that threshold measurement based on the extrapolation of volume to zero, a method used often in previous studies, is somewhat questionable. Finally, the measured dimensions of ablated craters reveal that the ablation volume per unit input energy is about 1.3-1.5 {mu}m{sup 3}/{mu}J at an intermediate fluence regime of 10ablation efficiency when compared to the ablation of glass with nanosecond ultraviolet laser pulses.

Ben-Yakar, Adela; Byer, Robert L. [Mechanical Engineering Department, University of Texas at Austin, Austin, Texas 78712 (United States); Applied Physics Department, Ginzton Lab, Stanford University, Stanford, California 94305 (United States); Applied Physics Department, Ginzton Lab, Stanford University, Stanford, California 94305 (United States)

2004-11-01

94

Multidiagnostic analysis of ultrafast laser ablation of metals with pulse pair irradiation  

SciTech Connect

Copper targets are irradiated in the ablation regime by pairs of equal, time-delayed collinear laser pulses separated on a timescale going from {approx_equal}2 ps to {approx_equal}2 ns. The ablation plume is characterized by ion probe diagnostic, fast imaging, and temporally and spatially resolved optical emission spectroscopy. The variation in the ablation efficiency with the delay between the pulses is analyzed by measuring the ablation crater profile with a contact profilometer. The second laser pulse modifies the characteristics of the plasma plume produced by the first pulse and the ablation efficiency. The different mechanisms involved in double pulse ultrafast laser ablation are identified and discussed. The experimental findings are interpreted in the frame of a simple model of the interaction of the second pulse with the nascent ablation plume produced by the first pulse. This model yields consistent and quantitative agreement with the experimental findings predicting the observed experimental trends of the ablation depth reduction and ion yield increase with the delay between the pulses, as well as the characteristic timescale of the observed changes. The possibility of controlling the characteristics of the plumes produced during ultrafast laser ablation via an efficient coupling of the energy of the second pulse to the various ablation components produced by the first pulse is of particular interest in ultrafast pulsed laser deposition and microprobe analyses of materials.

Amoruso, S.; Bruzzese, R. [Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Wang, X. [CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); O'Connell, G.; Lunney, J. G. [School of Physics, Trinity College-Dublin, Dublin 2 (Ireland)

2010-12-01

95

Laser Ablation-ICP-MS Analysis of Dissected Tissue: A  

E-print Network

Laser Ablation-ICP-MS Analysis of Dissected Tissue: A Conservation-Minded Approach to Assessing the animal. In this paper, we report on the application of laser ablation-ICP-MS (LA- ICP-MS) for sampling

Hopkins, William A.

96

Laser ablated hard coating for microtools  

DOEpatents

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

McLean, W. II; Balooch, M.; Siekhaus, W.J.

1998-05-05

97

Laser ablated hard coating for microtools  

DOEpatents

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

McLean, II, William (Oakland, CA); Balooch, Mehdi (Berkeley, CA); Siekhaus, Wigbert J. (Berkeley, CA)

1998-05-05

98

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

99

Femtosecond laser ablation for controlling micro and nano structuration  

E-print Network

Femtosecond laser ablation for controlling micro and nano structuration Dissertation zur Erlangung and sub micrometer scales. Laser ablation, which has the great advantage of precise material removal micrométriques et sub micrométriques. L'ablation laser, qui a le grand avantage d'un enlèvement de matière très

Paris-Sud XI, Université de

100

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires  

E-print Network

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires Wensheng Shi Kong, SAR, China Silicon carbide (SiC) nanowires were synthesized at 900°C by the laser ablation. Introduction THE laser ablation technique has been widely used for nano- struc tural processing because of its

Zheng, Yufeng

101

FEATURE ARTICLE A Microscopic View of Laser Ablation  

E-print Network

FEATURE ARTICLE A Microscopic View of Laser Ablation Leonid V. Zhigilei, Prasad B. S. Kodali applications of the breathing sphere model for molecular dynamics simulations of laser ablation of organic for microscopic simulations of laser ablation. I. Introduction The use of microscopic computer simulations

Zhigilei, Leonid V.

102

Femtosecond Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics  

E-print Network

Femtosecond Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics A thesis presented Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics Eric Mazur Brian R. Tull Abstract, with intense femtosecond laser pulses at energy densities exceeding the threshold for ablation (the macroscopic

Mazur, Eric

103

ORIGINAL ARTICLE Ultrashort pulsed laser ablation and stripping  

E-print Network

ORIGINAL ARTICLE Ultrashort pulsed laser ablation and stripping of freeze-dried dermis Huan Huang # Springer-Verlag London Ltd 2009 Abstract Plasma-mediated laser ablation and dissection of freeze was generally within 10 µm with 100 continuously repeated line scans. Ultrashort pulsed laser ablation

Guo, Zhixiong "James"

104

Femtosecond laser near-field ablation from gold nanoparticles  

E-print Network

LETTERS Femtosecond laser near-field ablation from gold nanoparticles ANTON PLECH1 *, VASSILIOS.plech@uni-konstanz.de Published online: 18 December 2005; doi:10.1038/nphys191 S hort-pulse laser ablation is promising owing to the low threshold for material removal from surfaces. In the laser-ablation process, solid material

Loss, Daniel

105

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

106

Dynamics of Laser-Driven Ablatively Accelerated Targets.  

NASA Astrophysics Data System (ADS)

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

Grun, Jacob

107

Laser Ablation for Small Hepatocellular Carcinoma  

PubMed Central

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is increasingly detected at small size (<5?cm) owing to surveillance programmes in high-risk patients. For these cases, curative therapies such as resection, liver transplantation, or percutaneous ablation have been proposed. When surgical options are precluded, image-guided tumor ablation is recommended as the most appropriate therapeutic choice in terms of tumor local control, safety, and improvement in survival. Laser ablation (LA) represents one of currently available loco-ablative techniques: light is delivered via flexible quartz fibers of diameter from 300 to 600??m inserted into tumor lesion through either fine needles (21g Chiba needles) or large-bore catheters. The thermal destruction of tissue is achieved through conversion of absorbed light (usually infrared) into heat. A range of different imaging modalities have been used to guide percutaneous laser ablation, but ultrasound and magnetic resonance imaging are most widely employed, according to local experience and resource availability. Available clinical data suggest that LA is highly effective in terms of tumoricidal capability with an excellent safety profile; the best results in terms of long-term survival are obtained in early HCC so that LA can be proposed not only in unresectable cases but, not differently from radiofrequency ablation, also as the first-line treatment. PMID:22191028

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

2011-01-01

108

Beam current controller for laser ion source  

DOEpatents

The present invention relates to the design and use of an ion source with a rapid beam current controller for experimental and medicinal purposes. More particularly, the present invention relates to the design and use of a laser ion source with a magnetic field applied to confine a plasma flux caused by laser ablation.

Okamura, Masahiro

2014-10-28

109

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

110

Short-pulse laser ablation of solid targets  

Microsoft Academic Search

Laser ablation of solid targets by Ti:sapphire laser radiation is studied. The solid targets are irradiated by 0.2–5000 ps laser pulses in the intensity range of 109 ? 5 × 1016Wcm2. Dependences of the ablation depth on the laser pulse energy and pulse duration are discussed. Advantages of sub-picosecond laser radiation for precise material processing are demonstrated.

Carsten Momma; Boris N Chichkov; Stefan Nolte; Ferdinand von Alvensleben; Andreas Tünnermann; Herbert Welling; Bernd Wellegehausen

1996-01-01

111

Modeling topology formation during laser ablation  

NASA Astrophysics Data System (ADS)

Micromachining high aspect-ratio structures can be accomplished through ablation of surfaces with high-powered lasers. Industrial manufacturers now use these methods to form complex and regular surfaces at the 10-1000 ?m feature size range. Despite its increasingly wide acceptance on the manufacturing floor, the underlying photochemistry of the ablation mechanism, and hence the dynamics of the machining process, is still a question of considerable debate. We have constructed a computer model to investigate and predict the topological formation of ablated structures. Qualitative as well as quantitative agreement with excimer-laser machined polyimide substrates has been demonstrated. This model provides insights into the drilling process for high-aspect-ratio holes.

Hodapp, T. W.; Fleming, P. R.

1998-07-01

112

Numerical simulation of laser ablation with cavity reflections  

Microsoft Academic Search

A self-consistent ablation, heat-conduction, and radiation-transport model is required to model laser ablation of reflective targets properly. In laser-ablation experiments on metal-loaded carbon targets, the shiny metallic crater formed by the beam can act as a focusing cavity. This phenomenon results in highly augmented ablation rates in small-spot laser tests in which the aspect ratio of the cavity (depth\\/spot diameter)

A. W. Bailey; A. Modak

1989-01-01

113

Pulsed holmium laser ablation of cardiac valves  

Microsoft Academic Search

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

Lothar Lilge; Wolfgang Radtke; Norman S. Nishioka

1989-01-01

114

NOVEL LASER ABLATION TECHNOLOGY FOR SURFACE DECONTAMINATION  

EPA Science Inventory

The objective of this project is to develop a novel Laser Ablation Decontamination in Liquid (LADIL) technology for surface decontamination and safe removal of radioactive and/or toxic contaminants. It aims to achieve more efficient surface decontamination without secondary conta...

115

Wavelength dependence of soft tissue ablation by using pulsed lasers  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-micron wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er:YAG laser produced the highest quality ablation with clear, sharp cuts following closely the spatial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The ablation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

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

2007-04-01

116

A Review of Laser Ablation Propulsion  

SciTech Connect

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 Saenger 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 role 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 [Photonic Associates, LLC, 200A Ojo de la Vaca Road, Santa Fe NM 87508 (United States); Bohn, Willy [Bohn Laser Consult, Weinberg Weg 43, Stuttgart (Germany); Lippert, Thomas [Paul Scherrer Institut, CH5232 Villigen PSI (Switzerland); Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Chikusa-ku, Nagoya (Japan); Schall, Wolfgang [DLR Institute of Technical Physics, Stuttgart (Germany); Sinko, John [Micro-Nano GCOE, Nagoya University, Furo-cho, Nagoya, Aichi (Japan)

2010-10-08

117

Laser-ablation processes (Invited Paper)  

NASA Astrophysics Data System (ADS)

The physical mechanisms associated with ablation of matter by laser irradiation are quite different in different regions of parameter space. The important parameters are the laser wavelength; the laser flux versus time, position, and angle of incidence at the target; and the target properties as well as the properties of the laser-transport medium adjacent to the irradiated target surface. Important target properties include surface contour, laser reflectivity and absorption depth, thermal diffusively, vaporization energy, Gruneisen coefficient, spall strength, ionization energies and plasma opacity versus temperature and density. As the flux increases, the process becomes less dependent on most of these target properties. Depending on the values of these various parameters, at relatively low fluxes targets can be vaporized and these vapors can be transparent to the laser beam. If a transparent liquid or solid transport medium exists in front of the vaporized target material, then a complicated contained- vaporization process takes place and the work done on the target by the vapors can be several orders of magnitude larger than with a gas or vacuum transport medium; the degree of work enhancement can depend strongly on the vapor condensability and condensed matter thermal conductivity. For short-pulselength irradiations of semi-transparent targets with a low- acoustic-impedance-laser-transport medium adjacent to the target, ablation needs to be a vacuum in order for the beam to be able to propagate to the target. For targets in a vacuum exposed to fluxes of this order (and considerably higher) and for long pulselengths, most of the laser energy will be absorbed (before reaching the critical surface) by inverse bremsstrahlung in material blown off from the target; at higher fluxes, the beam will be stopped at the critical surface producing localized absorption along with much higher energy densities and non-thermal equilibrium behavior. When the combination of pulselength, beam diameter, flux and target material are such that the blowoff becomes opaque to the laser and also the blowoff can traverse many beam diameters during the pulselength, then a complicated radiation-hydrodynamic process is involved with strong feedback between blowoff hydrodynamic expansion, laser absorption, radiation transport, and target ablation by plasma reradiation. In this paper the various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 1013 W/cm2, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, Ronald S.

1992-06-01

118

Investigations of Basic Ablation Phenomena During Laser Thrombolysis  

Microsoft Academic Search

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

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

119

Novel method for measuring excimer laser ablation thresholds of polymers  

NASA Astrophysics Data System (ADS)

Conical features produced on excimer laser ablated polymers are shown to provide a sensitive technique for determining ablation thresholds. This has been applied to polyimide, polyethylene terephthalate, polyethylene, and nylon 66 ablated using the 157 nm vacuum ultraviolet F2 laser.

Dyer, P. E.; Jenkins, S. D.; Sidhu, J.

1988-05-01

120

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, Éric; Falconet, Denis; Vertes, Akos

2014-11-21

121

Ripple formation at laser ablation of chromium thin film  

Microsoft Academic Search

Ablation characteristics of chromium thin film on a glass substrate by nanosecond laser pulses were investigated. The laser beam was tightly focused through the glass substrate to a stripe-like spot using the acylindrical lens. The metal was removed only by the central part of the laser beam, where local laser fluence exceeded the well-defined ablation threshold. Formation of a wide

Kestutis Regelskis; Gediminas Raciukaitis; Paulius Gecys

2007-01-01

122

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

123

Nanosecond Infrared Laser for Tissue Ablation  

NASA Astrophysics Data System (ADS)

The Mark-III Free-Electron Laser (FEL), operating at the 6.45?m wavelength, has been used successfully in human surgery. Due to the FEL's size and cost, there has been interest in the development of a compact, inexpensive infrared laser for human surgical applications. We have investigated the role of the FEL superpulse, leading to the prediction that nanosecond pulses can satisfy the dynamic criteria for tissue ablation. We have developed a laser based on difference frequency mixing and stimulated Raman scattering with four stages of frequency conversion, emitting at a wavelength of 6.45?m with 3-5ns pulse duration, pulse energies of up to 2mJ, and a pulse repetition rate of 3MHz. The laser system successfully ablated tissue, where collateral thermal damage was limited to several microns. In the future, it will be necessary to increase the pulse repetition rate to achieve an ablation rate acceptable for human surgery. We acknowledge the grant support: R43 RR018435, N00014-99-1-0891, and F49620-00-1-0370.

Edwards, G. S.; Pearlstein, R. D.; Copeland, M. L.; Hutson, M. S.; Latone, K.; Spiro, A.; Pasmanik, G.

2007-03-01

124

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

PubMed

This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)--a Nu Plasma HR--equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235U/238U, 236U/238U, 145Nd/143Nd, 146Nd/143Nd, 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred mum to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235U/238U and 236U/238U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the 235U/238U ratios measured in ten microsamples varied in the range from 0.0073 (corresponding to the natural uranium isotopic composition) to 0.023 (corresponding to initial 235U enrichment in reactor fuel). An inverse correlation was observed between the 236U/238U and 235U/238U isotope ratios, except in the case of one sample with natural uranium. The heterogeneity of the uranium isotope composition is attributed to the different burn-up grades of uranium in the fuel rods from which the microsamples originated. PMID:17874079

Boulyga, Sergei F; Prohaska, Thomas

2008-01-01

125

Z .Applied Surface Science 127129 1998 111116 Explosive phase transformation in excimer laser ablation  

E-print Network

, IN 47907, USA Abstract This work investigated phase change mechanisms during excimer laser ablation and the velocity of the laser-ablated plume, the ablation rate per pulse, light scattering from the laser-ablated particles and the size of the laser-ablated particles, in the laser fluence range y2 y2 Z y2 y2 .between 2

Xu, Xianfan

126

Nanochemical effects in femtosecond laser ablation of metals  

SciTech Connect

We study chemical energy released from the oxidation of aluminum in multipulse femtosecond laser ablation in air and oxygen. Our study shows that the released chemical energy amounts to about 13% of the incident laser energy, and about 50% of the ablated material is oxidized. The ablated material mass per laser pulse is measured to be on the nanogram scale. Our study indicates that femtosecond laser ablation is capable of inducing nanochemical reactions since the femtosecond laser pulse can controllably produce nanoparticles, clusters, and atoms from a solid target.

Vorobyev, A. Y.; Guo, Chunlei [The Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)] [The Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2013-02-18

127

Femtosecond, picosecond and nanosecond laser ablation of solids  

Microsoft Academic Search

Laser ablation of solid targets by 0.2-5000rps Ti : Sapphire laser pulses is studied. Theoretical models and qualitative explanations of experimental results are presented. Advantages of femtosecond lasers for precise material processing are discussed and demonstrated.

B. N. Chichkov; C. Momma; S. Nolte; F. von Alvensleben; A. Tünnermann

1996-01-01

128

Ultraviolet-laser ablation of skin  

SciTech Connect

The authors report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.

Lane, R.J.; Linsker, R.; Wynne, J.J.; Torres, A.; Geronemus, R.G.

1985-05-01

129

Particle analysis using laser ablation mass spectroscopy  

DOEpatents

The present invention provides a method of quickly identifying bioaerosols by class, even if the subject bioaerosol has not been previously encountered. The method begins by collecting laser ablation mass spectra from known particles. The spectra are correlated with the known particles, including the species of particle and the classification (e.g., bacteria). The spectra can then be used to train a neural network, for example using genetic algorithm-based training, to recognize each spectra and to recognize characteristics of the classifications. The spectra can also be used in a multivariate patch algorithm. Laser ablation mass specta from unknown particles can be presented as inputs to the trained neural net for identification as to classification. The description below first describes suitable intelligent algorithms and multivariate patch algorithms, then presents an example of the present invention including results.

Parker, Eric P.; Rosenthal, Stephen E.; Trahan, Michael W.; Wagner, John S.

2003-09-09

130

Barium ferrite films grown by laser ablation  

Microsoft Academic Search

Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al2O3 single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe12O19 phase, very well oriented with (001) texture, and exhibit a large perpendicular magnetic anisotropy. In this case, the microstructure and the anisotropy orientation are not influenced by variation

A. Lisfia; J. C. Lodder; P. de Haan; M. A. Smithers; F. J. G. Roesthuis

1998-01-01

131

KTP-532 laser ablation of urethral strictures  

NASA Astrophysics Data System (ADS)

In 1988, the KTP-532 laser was used to ablate a series of benign urethral strictures. Rather than using a single incision, as in urethrotomy, strictures were treated with a 360$DEG contact photoradiation. Thirty-one males, average age 53.2 years, received 37 treatments. Six patients underwent a second laser treatment. Stricture etiology was commonly iatrogenic (32%), traumatic (16%), and post-gonococcal (10%). Stricture location included mainly bulbar (49%), membranous (20%), and penile (12%) areas. The surgical technique consisted of a circumferential ablation followed by foley catheter placement (mean 10 days). Follow-up on 29 of 31 patients ranged from 1 to 16 months (mean 9.7) Complete success occurred in 17 patients (59%) who had no further symptoms or instrumentation. Partial success was seen in 6 patients (20.5%) with symptoms but no stricture recurrence. Six patients (20.5%) failed therapy requiring additional surgery or regular dilatations. No complications were encountered. Although longer assessment is required, KTP-532 laser ablation of urethral strictures appears efficacious.

Malloy, Terrence R.

1991-07-01

132

Properties of zirconia thin films deposited by laser ablation  

SciTech Connect

Zirconia thin films have been deposited by laser ablation of a ceramic ZrO{sub 2} target in vacuum or in oxygen background at 0.01 mbar. The laser beam generated by an ArF laser (?=193 nm, ?=40 Hz) has been focalized on the target through a spherical lens at an incident angle of 45°. The laser fluence has been established to a value from 2.0 to 3.4 Jcm{sup ?2}. A silicon (100) substrate has been placed parallel to the target, at a distance of 4 cm, and subsequently has been heated to temperatures ranging between 300 °C and 600 °C. Thin films morphology has been characterized by atomic force microscopy and secondary ion mass spectrometry. Biocompatibility of these thin films has been assessed by studying the cell attachment of L929 mouse fibroblasts.

Cancea, V. N. [Department of Physics, University of Craiova, Craiova 200585 (Romania); Filipescu, M.; Colceag, D.; Dinescu, M. [Department of Lasers, National Institute for Laser, Plasma and Radiation Physics, Magurele 077125 (Romania); Mustaciosu, C. [Horia Hulubei National Institute of Physics and Nuclear Engineering, Magurele, Bucharest (Romania)

2013-11-13

133

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 materiat layer; and forming conductive contacts in the plurality of contact holes.

Harley, Gabriel; Smith, David D.; Cousins, Peter John

2014-07-22

134

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

135

CO2 Laser Absorption in Ablation Plasmas  

SciTech Connect

The impulse formation by laser ablation is limited by the premature absorption of the incident laser radiation in the initially produced cloud of ablation products. The power fraction of a CO2 laser pulse transmitted through a small hole in a POM sample for pulse energies of 35 to 150 J focused on a spot of 2 cm2 has been compared with the incident power. The plasma formation in vacuum and in air of 3500 Pa and the spread of the shock wave with velocities of 1.6 to 2.4 km/s in the low pressure air was observed by Schlieren photography. A sharp edged dark zone with a maximum extension of 10 to 12 mm away from the target surface develops within 5 {mu}s independently of the pressure and is assumed to be a plasma. In order to find out, if this is also the zone where the majority of the incident laser radiation is absorbed, a CO2 probe laser beam was directed through the expansion cloud parallel to and at various distances from the sample surface. The time behavior of the absorption signal of the probe beam has been measured and an absorption wave could be observed.

Eckel, Hans-Albert; Tegel, Jochen; Schall, Wolfgang O. [DLR-Institute of Technical Physics, D-70503 Stuttgart, Postfach 80 03 20 (Germany)

2006-05-02

136

Nanosecond and femtosecond excimer laser ablation of fused silica  

Microsoft Academic Search

Ablation of fused silica using standard excimer lasers (20–30 ns pulse duration at 193, 248, and 308 nm) and a short pulse laser system (500 fs at 248 nm) is reported. Ablation rates range from several hundred nm\\/pulse (193 nm or fs-laser) up to about 6 µm\\/pulse (308 nm). The performance of the ablation is found to depend not only

J. Ihlemann; B. Wolff; P. Simon

1992-01-01

137

Ionization and fragmentation of solid C{sub 60} by femtosecond laser ablation  

SciTech Connect

Ionization and fragmentation of solid C{sub 60} dispersed on a silicon plate are investigated by femtosecond laser ablation. Bimodal mass distribution with large fragment ions C{sub 60-2n}{sup +} (0{<=}n{<=}11) and small fragment ions C{sub n}{sup +} (13{<=}n{<=}28), formation of dimer ion (C{sub 60}){sub 2}{sup +}, and delayed ionization of C{sub 60} have been observed as reported in gas phase experiments with nanosecond laser excitation. Metastable dissociation of small fragment ions C{sub n}{sup +} has been observed for the first time, which suggests different structures of fragment ions compared with those of well-studied carbon cluster ions. From these observations, strong coupling of laser energy to electronic degrees of freedom of solid C{sub 60} has been revealed for femtosecond laser ablation as compared with excitation in the gas phase.

Kobayashi, T.; Kato, T.; Matsuo, Y.; Kurata-Nishimura, M.; Kawai, J.; Hayashizaki, Y. [Discovery Research Institute, RIKEN, 2-1 Hirosawa, Saitama 351-0198 (Japan); Genomic Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Genomic Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045 (Japan); Discovery Research Institute, RIKEN, 2-1 Hirosawa, Saitama 351-0198, Japan and Genomic Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045 (Japan)

2007-02-14

138

Atomistic Modeling of Short Pulse Laser Ablation of Metals: Connections between Melting, Spallation, and Phase Explosion  

E-print Network

Atomistic Modeling of Short Pulse Laser Ablation of Metals: Connections between Melting, Spallation. Introduction Short pulse laser ablation is the phenomenon that is actively usedinabroadrangeofapplications for small satellites.4 The mechanisms responsible for the material removal in laser ablation include

Zhigilei, Leonid V.

139

Computational model for multiscale simulation of laser ablation Leonid V. Zhigilei  

E-print Network

Computational model for multiscale simulation of laser ablation Leonid V. Zhigilei Department computational approach that combines different methods to study laser ablation phenomenon is presented of laser ablation, a combined MD - finite element method (FEM) approach for simulation of propagation

Zhigilei, Leonid V.

140

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

141

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

142

Spectroscopic characterization of laser ablated silicon plasma  

NASA Astrophysics Data System (ADS)

We report plasma parameters of laser ablated silicon plasma using the fundamental (1064 nm) and second harmonics (532 nm) of a Nd?:?YAG laser. The electron temperature and electron number density are evaluated using the Boltzmann plot method and Stark broadened line profile, respectively. The electron temperature and electron number density are deduced using the same laser irradiance 2-16 GW cm-2 for 1064 nm and 532 nm as 6350-7000 K and (3.42-4.44) × 1016 cm-3 and 6000-6400 K and (4.20-5.72) × 1016 cm-3, respectively. The spatial distribution of plasma parameters shows a decreasing trend of 8200-6300 K and (4.00-3.60) × 1016 cm-3 for 1064 nm and 6400-5500 K and (5.10-4.50) × 1016 cm-3 for 532 nm laser ablation. Furthermore, plasma parameters are also investigated at low pressure from 45 to 550 mbar, yielding the electron temperature as 4580-5535 K and electron number density as (1.51-2.12) × 1016 cm-3. The trend of the above-mentioned results is in good agreement with previous investigations. However, wavelength-dependent studies and the spatial evolution of plasma parameters have been reported for the first time.

Shakeel, Hira; Mumtaz, M.; Shahzada, S.; Nadeem, A.; Haq, S. U.

2014-06-01

143

A spectroscopic study of laser ablation plasma from Mo target  

NASA Astrophysics Data System (ADS)

The goal of this contribution is to present time-resolved optical spectroscopy studies of laser ablation of the Mo target with ˜ 3.5 ns, 0.4 J pulses delivered by the Nd-YAG laser system at 1.06 ?m. The sample was placed in a vacuum chamber under 5 × 10-5 mbar pressure and irradiated, with power densities varied up to 22.7 GW cm-2. The ion emission from the plasma plume was measured using an electrostatic ion energy analyzer (IEA) and ion collector, which allowed us to estimate the ion kinetic energy and charge independent of the applied power densities. The signal collected by the IEA indicated the presence of molybdenum ions up to eight-ion charge. Simultaneously after the ion emission, the optical spectra acquired within 2 ?s of exposure time were observed in the wavelength range from 200 to 1000 nm with a Mechelle 5000 spectrometer equipped with an iCCD (iStar) detector. The plasma electron temperature was estimated from a Boltzmann plot based on the registered spectra as well as from the ion measurements.

Jakubowska, Katarzyna; Kubkowska, Monika; Blagoev, Alexander; Rosi?ski, Marcin; Parys, Piotr; G?sior, Pawe?

2014-05-01

144

Ultrashort-pulse laser ablation of indium phosphide in air  

Microsoft Academic Search

.   Ablation of indium phosphide wafers in air was performed with low repetition rate ultrashort laser pulses (130 fs, 10 Hz)\\u000a of 800 nm wavelength. The relationships between the dimensions of the craters and the ablation parameters were analyzed. The\\u000a ablation threshold fluence depends on the number of pulses applied to the same spot. The single-pulse ablation threshold value\\u000a was estimated to be

J. Bonse; J. M. Wrobel; J. Krüger; W. Kautek

2001-01-01

145

Numerical study on propulsion properties of laser ablated polymer target  

NASA Astrophysics Data System (ADS)

Laser propulsion as a new concept propulsion technology, it is paid more and more extensive concern. Laser ablation micro thruster is one of the focus with its high specific impulse, wide dynamic range of impulse, small minimum impulse bit, low power etc, laser ablation micro thruster has wide application prospects on high-precision task of satellite attitudeadjustment, orbit maintain and networking formation control. Due to low thermal conduction, low ablation threshold, polymer material was easily ablated to generate thrust. A computational model of laser ablated polymer was established to simulated the micro-thruster working in vacuum environment. The polymer don't have fixed fusion point, so build the ablation criterion based on threshold energy, which has observed in many experiments. Put forward the polymer ablation criterion in the numerical model, the target ablation phenomenon happens when inner deposited energy achieve the threshold value. Established the energy distribution equation to describes the ablation process of temperature rise, phase change and the influence of chemical exothermic process. When ablation phenomenon happened the ablation products would ejected, and the target gained recoil impulse from ejection process. According to energy distribution equations we can get the ejection energy, and then get the recoil momentum of target based on momentum conservation law. The propulsion properties of laser ablated polymer was studied through the numerical analysis model. Revealed the relationship between the propulsion capability and laser parameters. Analyzed influence of different propellants to propulsion performance. The numerical analysis model can reflect the propulsion capability of different polymer propellant, revealed the law of propulsion parameters in laser ablation process.

Li, Nanlei; Hong, Yanji; Wu, Jie; Zhou, Weijing; Ye, Jifei

2013-05-01

146

Endovenous laser ablation for the treatment of varicose veins.  

PubMed

Lower extremity venous insufficiency secondary to saphenous vein insufficiency is a common medical condition that decreases a patient's quality of life. Traditionally treated with high ligation and stripping, minimally invasive procedures using endovenous thermal ablation techniques, such as endovenous laser ablation, have evolved. The use of detailed imaging and advances in the understanding of the anatomy of truncal vein insufficiency are important for performing the endovenous laser ablation procedure successfully. Endovenous laser ablation eliminates reflux with less morbidity, faster recovery, and improved cosmetic results with high patient satisfaction. As such, it has become the preferred treatment method for varicose veins since it was first introduced a decade ago. PMID:22205579

O?uzkurt, Levent

2012-01-01

147

Arterial false aneurysm in the groin following endovenous laser ablation.  

PubMed

Endovenous laser ablation is a minimally invasive catheter-based procedure for the treatment of varicose veins. The procedure involves injecting tumescent anaesthesia around the catheterised truncal vein, before thermal ablation by the laser. We report a case of a false aneurysm arising from a branch of the inferior epigastric artery, following endovenous laser ablation. The false aneurysm was thought to be caused by injury to the artery by the needle used to inject the tumescent anaesthesia. Although a rare complication, newer tumescentless techniques such as mechanicochemical ablation and cyanoacrylate glue would prevent such a complication. PMID:24255091

Ostler, Alexandra E; Holdstock, Judy M; Harrison, Charmaine C; Whiteley, Mark S

2015-04-01

148

Ripple formation in the chromium thin film during laser ablation  

Microsoft Academic Search

The beam of a nanosecond pulse laser tightly focused to a line was applied for the back-side ablation of the chromium thin film on a glass substrate. The stripe ablated with a single laser pulse had sharp edges on both sides and ridges of the melted metal around it. The partially overlapping pulses formed a wide cleaned area with a

Kestutis Regelskis; Gediminas Raciukaitis; Mindaugas Gedvilas

2007-01-01

149

Metal Ablation with Short and Ultrashort Laser Pulses  

Microsoft Academic Search

In laser microstructuring there is a general conflict between precision and efficiency. Short pulsed micro- and nanosecond systems generally allow high ablation rates. Yet, thermal damage of the workpiece cannot be avoided completely. Ultrafast picoand femtosecond systems allow a higher precision, yet at lower ablation efficiency. This on the one hand can be attributed to the generally lower medium laser

Karl-Heinz Leitz; Benjamin Redlingshöfer; Yvonne Reg; Andreas Otto; Michael Schmidt

2011-01-01

150

Determination of femtosecond ablation thresholds by using laser ablation induced photoacoustics (LAIP)  

NASA Astrophysics Data System (ADS)

Femtosecond laser material processing as micromachining and nanoparticles fabrication require a careful control of the fluences deposited on the samples. In many cases, best results are obtained by using fluences slightly above the Laser Ablation Threshold (LAT), therefore its accurate determination is an important requirement. LAT can be obtained by measuring the intensity of the acoustic signal generated during the ablation process as a function of the laser fluence. In this work femtosecond laser ablation thresholds of commercially polished stainless steel plates, white high impact polystyrene, frosted glass, antique rag papers and silicon oxynitride thin films were determined by using laser ablation induced photoacoustics (LAIP). Results were compared with similar data previously obtained by using a nanosecond Nd:YAG laser.

Orzi, Daniel J. O.; Alvira, Fernando C.; Bilmes, Gabriel M.

2013-03-01

151

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

152

Femtosecond laser ablation of brass in air and liquid media  

SciTech Connect

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. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada) [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Physics, Faculty of Sciences, Tanta University, Tanta (Egypt); Gagnon, J. E.; Fryer, B. J. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada) [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Earth and Environmental Sciences, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

2013-06-07

153

Laser ablation plume dynamics in nanoparticle synthesis  

SciTech Connect

The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO{sub 2} laser pulse with a duration of {approx}500 {mu}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 {mu}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 ({approx}10 {mu}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. (interaction of laser radiation with matter. laser plasma)

Osipov, V V; Platonov, V V; Lisenkov, V V [Institute of Electrophysics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

2009-06-30

154

Neutral atomic jet generation by laser ablation of copper targets  

SciTech Connect

This work aimed the obtainment of a neutral atomic jet departing from a plume generated by laser ablation of copper targets. A pair of electrodes together with a transducer pressure sensor was used to study the ablated plume charge composition and also to measure the ion extraction from the plasma plume. The neutral beam was produced with this setup and the relative abundance of neutrals in the plasma was measured, it decreases from 30% to 8% when the laser fluence is varied from 20 J/cm{sup 2} to 32 J/cm{sup 2}. The necessary voltage to completely remove the ions from the plume varied from 10 V to 230 V in the same fluence range. TOF analysis resulted in center of mass velocities between 3.4 and 4.6 km/s, longitudinal temperature in the range from 1 × 10{sup 4} K to 2.4 × 10{sup 4} K and a Mach number of M = 2.36, calculated using purely hydrodynamic expansion approximation.

Matos, J. B. de; Rodrigues, N. A. S. [Department of Physics, Technological Institute for Aeronautics – ITA/DCTA, São José dos Campos, P.O. Box 6050, 12.228-900 Sao Paulo (Brazil); Destro, M. G.; Silveira, C. A. B. da [Photonics Division, Institute for Advanced Studies – IEAv/DCTA, São José dos Campos, P.O. Box 6044, 12.231-970 Sao Paulo (Brazil)

2014-08-15

155

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

156

Metal particles produced by laser ablation for ICP-MSmeasurements  

SciTech Connect

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

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

2007-06-01

157

Nanosecond Pulsed Laser Ablation of Copper in Supercritical Carbon Dioxide  

NASA Astrophysics Data System (ADS)

A copper target in supercritical CO2 was ablated using nanosecond Nd:YAG laser pulses for a variety of different laser irradiation times, temperatures and pressures. The irradiated copper surface was evaluated by scanning electron microscopy and laser microscopy. Experiments were also conducted in atmospheric conditions with air and liquid hexane to evaluate the environmental dependence of ablation. The results demonstrated that laser ablation of a metal target in high pressure was affected by the pressure and the surrounding environment. An ablation crater with a depth of 6.9 µm was produced by ablating at a temperature of 40 °C, a pressure of 25 MPa, and an irradiation time of 500 s.

Kuwahara, Yutaka; Saito, Takashi; Haba, Minori; Iwanaga, Tomoki; Sasaki, Mitsuru; Goto, Motonobu

2009-04-01

158

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

159

Renaissance of laser interstitial thermal ablation.  

PubMed

Laser interstitial thermal therapy (LITT) is a minimally invasive technique for treating intracranial tumors, originally introduced in 1983. Its use in neurosurgical procedures was historically limited by early technical difficulties related to the monitoring and control of the extent of thermal damage. The development of magnetic resonance thermography and its application to LITT have allowed for real-time thermal imaging and feedback control during laser energy delivery, allowing for precise and accurate provision of tissue hyperthermia. Improvements in laser probe design, surgical stereotactic targeting hardware, and computer monitoring software have accelerated acceptance and clinical utilization of LITT as a neurosurgical treatment alternative. Current commercially available LITT systems have been used for the treatment of neurosurgical soft-tissue lesions, including difficult to access brain tumors, malignant gliomas, and radiosurgery-resistant metastases, as well as for the ablation of such lesions as epileptogenic foci and radiation necrosis. In this review, the authors aim to critically analyze the literature to describe the advent of LITT as a neurosurgical, laser excision tool, including its development, use, indications, and efficacy as it relates to neurosurgical applications. PMID:25727222

Missios, Symeon; Bekelis, Kimon; Barnett, Gene H

2015-03-01

160

Amalgam ablation with the Er:YAG laser  

Microsoft Academic Search

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

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

1995-01-01

161

Quantitative Measurements Of Pulsed Infrared Laser Tissue Ablation  

NASA Astrophysics Data System (ADS)

Several new lasers that emit infrared laser radiation are being considered for surgical applications. In order to understand the irradiation and tissue parameters that control the infrared laser ablation process, three different, yet related, experiments were conducted. Ablation of guinea pig skin and bovine aorta, myocardium and liver using a TEA CO2 laser with a pulse duration of 2 ?s was quantified by measuring the mass of tissue removed as a function of incident fluence per pulse. For per pulse fluences greater than 5 J/cm2 the ablation rate data are strongly dependent upon the mechanical strength of the tissue thus indicating a potential inadequacy of ablation models that do not consider tissue strength. The ablation of both soft and hard tissues using the normal-spiking-mode Er:YAG laser was quantified by measuring the number of pulses needed to perforate a measured thickness of tissue. The ablation of aorta and skin was more efficient than bone ablation. The ablation craters formed in skin and bone were the same shape as the incident laser beam, i.e. circular. In aorta, elliptical craters were formed at high fluence pulses; the long axis of the ellipse was always oriented perpendicular to the longitudinal axis of the aorta. Again, tissue mechanical properties were shown to be important. Er:YAG laser ablation dynamics were studied using flash photography and optical pump-probe techniques. The velocity of the plume front was found to be approximately Mach 4. It was also shown that each spike in the normal-spiking-mode pulse train was capable of ablating and rapidly ejecting tissue. The combined results of the three experiments indicate that removal of tissue by infrared laser radiation is an explosive process, the speed of which is determined in part by the mechanical strength of the tissue.

Walsh, Joseph T.

1989-08-01

162

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

163

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

SciTech Connect

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

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

2012-05-15

164

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

165

Atmospheric pressure imaging mass spectrometry of drugs with various ablating lasers  

NASA Astrophysics Data System (ADS)

The atmospheric pressure mass spectrometric detection efficiency of organic species (tofisopam and verapamil) was measured by means of the laser ablation of dried solution drops containing known amount of the analyte. Ablated molecules were ionized by an atmospheric pressure laser plasma cell and then introduced in the TOF mass-spectrometer. The spot was formed by dripping 2 ?l of solution on the stainless steel substrate and consequent drying. Then it was scanned by an intense ablating beam of various lasers (CO2, Nd:YAG and femtosecond fiber laser) until the spot was completely eroded during the non-stop MS-analysis of ablated material. The sensitivity was defined as the ratio of the total ion current integral of the relevant mass peaks to the amount of molecules in the spot. All the tested lasers are suitable for the ablation and subsequent MS-detection of organic species in dried solution spots given enough power deposition is provided. The measured sensitivity values reach 0.1 ions/fg of tested analytes.

Moshkunov, K. A.; Alimpiev, S. S.; Grechnikov, A. A.; Nikifirov, S. M.; Pento, A. V.; Simanovsky, Ya O.

2014-12-01

166

Ablation of crystalline oxides by infrared femtosecond laser pulses  

SciTech Connect

We use focused laser pulses with duration of 180 fs and wavelength of 800 nm to study the interactions of high power near-infrared light with the surfaces of single-crystal transparent oxides (sapphire, LaAlO{sub 3}, SrTiO{sub 3}, yttria-stabilized ZrO{sub 2}, and MgO); the morphologies of the ablation craters are studied by atomic force microscopy and scanning electron microscopy. With the exception of LaAlO{sub 3}, the high temperature annealing of these oxide crystals produces atomically flat starting surfaces that enable studies of the morphology of ablation craters with subnanometer precision. The threshold fluence for ablation is determined directly from atomic-force microscopy images and increases approximately linearly with the band gap of the oxide. For all oxides except sapphire, the depth of the ablation crater increases approximately as the square root of the difference between the peak laser fluence and the threshold fluence for ablation. Sapphire shows unique behavior: (i) at laser fluences within 1 J/cm{sup 2} of the threshold for ablation, the depth of the ablation crater increases gradually instead of abruptly with laser fluence, and (ii) the rms roughness of the ablation crater shows a pronounced minimum of <0.2 nm at a laser fluence of 1 J/cm{sup 2} above the threshold.

Watanabe, Fumiya; Cahill, David G.; Gundrum, Bryan; Averback, R. S. [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2006-10-15

167

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

168

Physical mechanisms of short pulse laser ablation D. von der Linde and K. Sokolowski-Tinten  

E-print Network

Physical mechanisms of short pulse laser ablation D. von der Linde and K. Sokolowski and optical properties. Keywords: Laser ablation, femtosecond pulses 1. INTRODUCTION Laser processing removal of material from the surface following laser exposure, commonly called laser ablation or laser

von der Linde, D.

169

The mesoscopic modeling of laser ablation  

NASA Astrophysics Data System (ADS)

It is common to look at the atomic processes of removal of atoms or ions from surfaces. At this microscopic scale, one has to understand which surface ions are involved, which excited states are created, how electrons are transferred and scattered, and how the excitation leads to ion removal. It is even more common to look at continuum models of energy deposition in solids, and at the subsequent heat transfer. In these macroscopic analyses, thermal conduction is combined with empirical assumptions about surface binding. Both these pictures are useful, and both pictures have weaknesses. The atomistic pictures concentrate on relatively few atoms, and do not recognize structural features or the energy and carrier fluxes on larger scales. The continuum macroscopic models leave out crystallographic information and the interplay of the processes with high nonequilibrium at smaller scales. Fortunately, there is a middle way: mesoscopic modeling, which both models the key microstructural features and provides a link between microscopic and macroscopic. In a mesoscopic model, the length scale is determined by the system; often this scale is similar to the grain size. Microstructural features like grain boundaries or dislocations are considered explicitly. The time scale in a mesoscopic model is determined by the ablation process (such as the pulse length) rather than the short time limitations of molecular dynamics, yet the highly nonequilibrium behavior is adequately represented. Mesoscopic models are especially important when key process rates vary on a short length scale. Some microstructural feature (like those in dentine or dental enamel) may absorb light much more than others; other features (like grain boundaries) may capture carriers readily, or allow easier evaporation, or capture and retain charge (like grain boundaries); it is these processes which need a mesoscopic analysis. The results described will be taken largely from the work on MgO of Ribeiro, Ramos, and Stoneham for ablation by sub-band gap light.

Stoneham, A. M.; Ramos, M. M. D.; Ribeiro, R. M.

170

Studies of silicon-nitride (Si 3N 4) using laser ablation mass spectrometry  

NASA Astrophysics Data System (ADS)

A reflectron time-of-flight mass spectrometer combined with pulsed laser ablation and post ablation ionisation techniques was used to investigate the ionic and neutral ablation products from powder and thin film samples of Si 3N 4 at 266 nm. Two prominent peaks at m/q = 28 and 70 were always observed for both the ionic and neutral ablation products. However, on the basis of the isotopic abundance of Si, it is found that the mass peak at m/q = 70 should be assigned as Si 2N + rather than (Si 3N 4) 2+ as suggested by Takigawa and Hemminger [Appl. Surf. Sci. 79/80 (1994) 146]. The photo-fragmentation pattern of the neutral ablation product at m/q = 70 also strongly supports this argument: when Si 2N is dissociated by a 355 nm laser, it fragments into SiN and Si. This result is consistent with the experimental results of Iraqi et al. [J. Phys. Chem. 97 (1993) 11371] using neutralisation-reionisation collisional mass spectrometry. In addition, the ion yields of neutral ablation product Si and Si 2N as a function of time delay between the post-ionisation and the ablation laser were also investigated. The result shows the experimental velocity distributions are broader than expected for a Maxwell-Boltzmann distribution.

Wang, S. L.; Ledingham, K. W. D.; Jia, W. J.; Singhal, R. P.

1996-03-01

171

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

172

Corneal ablation using the pulse stretched free electron laser  

Microsoft Academic Search

The Mark-III Free Electron Laser (FEL), tuned to lambda=6.45 mum has been demonstrated to provide for efficient ablation in ocular and neural tissues with minimal collateral damage. To date, the role of the FEL pulse structure on the mechanism of ablation has not been determined. In an effort to study the role of the FEL micropulse on the ablation of

Mark A. Mackanos; Karen M. Joos; John A. Kozub; E. D. Jansen

2005-01-01

173

Influence of laser-induced air breakdown on femtosecond laser ablation of aluminum.  

PubMed

We investigated the influence of laser-induced air breakdown on the femtosecond laser ablation of aluminum target using time-resolved pump-probe shadowgraphic imaging method. The early-stage plasma expanding dynamics and subsequent expanding behaviors of shockwaves and material ejection plume were analyzed through shadowgraphs recorded at different time delays. The dominated mechanisms were clarified at different stages during femtosecond laser pulses ablating aluminum, which provide very valuable information for ultrashort laser ablation of metals. PMID:25835895

Zhang, Hang; Zhang, Fangteng; Du, Xi; Dong, Guoping; Qiu, Jianrong

2015-01-26

174

Laser ablation dynamics in metals: The thermal regime  

SciTech Connect

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.; Brambilla, M.; Dabbicco, M.; Scamarcio, G. [CNR-IFN UOS Bari, via Amendola 173, I-70126 Bari (Italy); Dipartimento Interateneo di Fisica, Universita degli Studi e Politecnico di Bari, via Amendola 173, I-70126 Bari (Italy); Columbo, L. L. [CNR-IFN UOS Bari, via Amendola 173, I-70126 Bari (Italy); Dipartimento di Scienza ed Alta tecnologia, Universita dell'Insubria, via Valleggio 11, 22100 Como (Italy); Ancona, A.; Sibillano, T. [CNR-IFN UOS Bari, via Amendola 173, I-70126 Bari (Italy)

2012-07-02

175

Carbon nanofoam formed by laser ablation.  

PubMed

Foam-like carbon (carbon nanofoam, CNF) which belongs to the porous carbon family is formed by pulsed laser ablation of graphite in liquid nitrogen. Each bubble is about 3-10 nm in size and has a layered structure with typically one to four graphene layers. The CNF forms nanoparticles of about 100 nm in size. CNF encapsulating platinum nanoparticles (Pt@CNF) is formed when a mixture of graphite, platinum, and hexadecanoic acid is used as a target. Each bubble encapsulating a platinum nanoparticle is approximately 15 +/- 4 nm in diameter and contains typically 6 +/- 3 graphene walls. The platinum nanoparticles in the CNF are 9 +/- 4 nm in diameter. The annealing of the Pt@CNF at 300 degrees C for a week in vacuum reveals that the CNF effectively prevents the platinum nanoparticles from aggregating. PMID:22755133

Kohno, Hideo; Tatsutani, Kentaro; Ichikawa, Satoshi

2012-03-01

176

A rotational study of laser ablated thiourea.  

PubMed

A laser ablation device in combination with a molecular beam Fourier-transform microwave spectrometer has allowed the observation of the rotational spectrum of solid thiourea for the first time. The sensitivity reached in the experiment allowed the observation of the isotopomers (34)S, (13)C, and (15)N in their natural abundance. The spectrum of D(4)-thiourea was also analyzed from an enriched sample. The complicated hyperfine structure arising from the presence of two (14)N quadrupolar nuclei has been fully resolved and analyzed. The substitution r(s) structure has been derived from the experimental moments of inertia. Thiourea in gas phase presents a planar heavy atom skeleton. Experimental inertial defect values and high-level ab initio calculations reveal that the amino groups hydrogen atoms lie out-of-plane with a C(2) symmetry configuration and are involved in large amplitude inversion motions. PMID:15267505

Lesarri, Alberto; Mata, Santiago; Blanco, Susana; Lopez, Juan C; Alonso, Jose L

2004-04-01

177

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

178

Outcomes of ablative fractional laser scar treatment.  

PubMed

Ablative fractional laser (AFL) systems are commonly used to treat various scars, and recent reports have indicated that early scar treatment with fractional lasers has good aesthetic results. Some scars respond dramatically to AFL treatment, incurring high levels of patient satisfaction; however, other scars respond poorly or became worse after treatment. This study was designed to clarify prognostic factors that predict AFL scar treatment outcomes. A total of 108 patients were included in this study. The fractional laser treatments were repeated every 4 weeks until the scar site was acceptable and no additional improvement was expected or the patient discontinued the treatment. The scar improvements were defined as changes in the Manchester scar scale (MSS) from before to after laser treatment. A digital camera was used to acquire digital photographs of the scars under the same light source, the same background, exposure, and white balance. This study developed a modification of the MSS for image analysis in which colour assessment was based on L*a*b* colour co-ordinates of the digital images. The mean MSS values prior to and after laser treatments were 11.6 ± 3.6 and 9.5 ± 2.9, respectively (p < 0.01). AFL treatment improved the qualities of each scar, and the improvements were evident in colour and contour. Scar elevation, pigmentation, high vascularity, early onset of treatment, and the number of treatment sessions were directly related to scar improvement after AFL therapy (p < 0.05). AFL treatments were effective methods for scar treatment. Clinicians can use these prognostic factors to determine treatment plans and to estimate scar improvement after AFL treatment. PMID:24845386

Kim, Deok-Woo; Hwang, Na-Hyun; Yoon, Eul-Sik; Dhong, Eun-Sang; Park, Seung-Ha

2015-04-01

179

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

2014-12-01

180

Short pulse laser ablation is photomechanical, not thermal or chemical  

Microsoft Academic Search

Proposed mechanisms for pulsed laser ablation of biological tissue include photochemical, photothermal and photomechanical models. The principal observed effects which the correct model must explain include the high efficiency of the process, typically an order of magnitude less energy is required than for long pulse or cw ablation, and the minimal thermal damage to surrounding tissue. The photomechanical model postulates

I. Itzkan; D. Albagli; M. Dark; L. T. Perelman; C. von Rosenberg; M. S. Feld

1994-01-01

181

Transient States of Matter during Short Pulse Laser Ablation  

Microsoft Academic Search

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

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

1998-01-01

182

In situ Diagnostics During Carbon Nanotube Production by Laser Ablation  

NASA Technical Reports Server (NTRS)

The preliminary results of spectral analysis of the reaction zone during the carbon nanotube production by laser ablation method indicate synergetic dependence on dual laser setup. The emission spectra recorded from different regions of the laser ablated plume at different delay times from the laser pulses are used to map the temperatures of C2 and C3. These are compared with Laser Induced Fluorescence (LIF) spectra also obtained during production to model the growth mechanism of carbon nanotubes. Experiments conducted to correlate the spectral features with nanotube yields as a function of different production parameters will be discussed.

Arepalli, Sivaram

1999-01-01

183

Preparation and investigation of thick carbon foils prepared by laser plasma ablation deposition  

Microsoft Academic Search

Carbon foils prepared by laser plasma ablation deposition using a power density of >1GW\\/cm2 are so far the only ones which have been shown to have a total random orientation of the nanocrystallites and thus the theoretically best resistance against irradiation damage caused by ion bombardment. Need for longer lifetimes of carbon stripper foils was observed firstly in tandem accelerator

P. Maier-Komor; G. Dollinger; R. Krücken

2006-01-01

184

Ablation characteristics of cubic-boron nitride ceramic with femtosecond and picosecond laser pulses  

NASA Astrophysics Data System (ADS)

Ablation of cubic-boron nitride (c-BN) ceramic irradiated by Ti:sapphire laser (110 fs, 790 nm) and Nd:YAG laser (100 ps, 1.064 ?m) pulses is comparatively studied. In the case of Ti:sapphire laser ablation, it is observed that the ablation depth per pulse has two different ablation regimes, being similar to the fs laser ablation of metals. The ablation threshold fluence for the 110 fs Ti:sapphire laser is estimated to be 15 mJ/cm2 for low fluence ablation, and 180 mJ/cm2 for high fluence ablation. With x-ray photoelectron spectroscopy signal and scanning electron microscope observation it is evident that the surface ablated with the 110 fs Ti:sapphire laser pulses remains as the BN layer itself and is not melted. With the 100 ps Nd:YAG laser ablation, the boron semiconductor layer is formed on the ablated surface.

Hirayama, Yoichi; Obara, Minoru

2001-12-01

185

Hydrocarbon level detection with nanosecond laser ablation  

NASA Astrophysics Data System (ADS)

Nanosecond laser induced breakdown in liquid is used as a technique to detect hydrocarbon levels in water. A Q-switched Nd:YAG laser was focused to generate optical breakdown associated with shock wave generation. The shock wave was propagated at the speed of sound in the medium after travelling 1 ?s outward from the center of optical breakdown. Different amplitudes of sound were traced with the aid of an ultrasonic probe. The optical properties of the hydrocarbon solution were quantified via fundamental refractive index measurement (the Snell law). A continuous mode diode pumped solid state laser with second harmonic generation was used as the illumination light source. A CCD video camera with Matrox version 4.2 software was utilized to analyze the recording image. Option line analysis was performed to analyze the intensity of optical breakdown at different input energies. Gray level analysis was also conducted on the scattering light after passing through the hydrocarbon solution at different concentrations. The hydrocarbon solution comprised impurities or particles that varied according to the concentration. The average of the gray level is assumed to present the size of the particle. Inherently, as the acoustic wave propagates outward, it transports the mass (particles or impurities) and impacts on the ultrasonic probe. As a result a higher concentration of hydrocarbons reveals a larger amplitude of sound waves. This phenomenon is identified as a finger print for hydrocarbon levels between 100 and 1000 ppm. The transient detection, without complicated sampling preparation and no hazardous chemical involvement, makes laser ablation a promising technique to detect in situ hydrocarbon levels in water.

Bidin, Noriah; Hosseinian S, Raheleh; Nugroho, Waskito; Mohd Marsin, Faridah; Zainal, Jasman

2013-12-01

186

Surface Decontamination Using Laser Ablation Process - 12032  

SciTech Connect

A new decontamination method has been investigated and used during two demonstration stages by the Clean-Up Business Unit of AREVA. This new method is based on the use of a Laser beam to remove the contaminants present on a base metal surface. In this paper will be presented the type of Laser used during those tests but also information regarding the efficiency obtained on non-contaminated (simulated contamination) and contaminated samples (from the CEA and La Hague facilities). Regarding the contaminated samples, in the first case, the contamination was a quite thick oxide layer. In the second case, most of the contamination was trapped in dust and thin grease layer. Some information such as scanning electron microscopy (SEM), X-Ray scattering spectroscopy and decontamination factors (DF) will be provided in this paper. Laser technology appears to be an interesting one for the future of the D and D applications. As shown in this paper, the results in terms of efficiency are really promising and in many cases, higher than those obtained with conventional techniques. One of the most important advantages is that all those results have been obtained with no generation of secondary wastes such as abrasives, chemicals, or disks... Moreover, as mentioned in introduction, the Laser ablation process can be defined as a 'dry' process. This technology does not produce any liquid waste (as it can be the case with chemical process or HP water process...). Finally, the addition of a vacuum system allows to trap the contamination onto filters and thus avoiding any dissemination in the room where the process takes place. The next step is going to be a commercial use in 2012 in one of the La Hague buildings. (authors)

Moggia, Fabrice; Lecardonnel, Xavier; Damerval, Frederique [AREVA, Back End Business Group, Clean Up Business Unit (France)

2012-07-01

187

Kinoform optics: direct fabrication by F2 laser ablation  

Microsoft Academic Search

A 64×64 element kinoform was microfabricated in fused silica by direct ablation with a pulsed 157-nm laser source that circumvents multistep lithographic patterning and etching routines. A 4-level design of ?300-nm etch layers is described.

Amir H. Nejadmalayeri; Andrew Yick; Jianzhao Li; Peter R. Herman

2003-01-01

188

Dental material ablation with the Er:YAG laser  

Microsoft Academic Search

It is essential for any laser which will be used in the clinic by dentists to remove existing dental materials for this laser to be a viable replacement of the dental drill. There is however a concern about the thermal damage which a laser can cause due to the heat that is generated by the ablation of these materials. The

H. Wigdor; S. R. Visuri

1994-01-01

189

Formation of ZnO nanoparticles by laser ablation in neat water Kuk Ki Kim a  

E-print Network

Formation of ZnO nanoparticles by laser ablation in neat water Kuk Ki Kim a , Daehyun Kim b , Sang by laser ablation with various ablation times (10­40 min), fluences (50­130 mJ/pulse), and wavelengths using physical and chemical methods [1­3]. Recently, laser ablation of a zinc metal target in liquid

Kim, Sang Kyu

190

Nanometer-scale ablation with a table-top soft x-ray laser  

E-print Network

Nanometer-scale ablation with a table-top soft x-ray laser G. Vaschenko, A. Garcia Etxarri, C. S Optical Society of America OCIS codes: 140.3390, 140.7240, 310.3840. Laser ablation of nanoscale features- rectly ablating sub-100 nm nanoscale holes using a focused soft x-ray laser beam. Very clean ablation

Rocca, Jorge J.

191

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

E-print Network

Nanoscale patterning of graphene through femtosecond laser ablation R. Sahin, E. Simsek, and S.164.158.129 On: Mon, 10 Feb 2014 15:01:27 #12;Nanoscale patterning of graphene through femtosecond laser ablation femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold

Simsek, Ergun

192

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 solids laser ablation is not fully understood. In the case of metals and strongly absorbing

von der Linde, D.

193

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

E-print Network

1 Ciliary white-light: optical aspect of ultrashort laser ablation on transparent dielectrics Yi on a novel nonlinear optical phenomenon, coined as ciliary white-light, during laser ablation of transparent dynamics of the ablated surface, providing a real time in-situ observation of the laser ablation process

Paris-Sud XI, Université de

194

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 stoichiometry were synthesized in the gas phase by excimer ArF laser ablation of a ZnO target and investigatedOm clusters of different stoichiometry in a laser-ablation plasma plume. The effect of ablation conditions

Paris-Sud XI, Université de

195

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

SciTech Connect

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

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

2010-10-08

196

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

197

Femtosecond laser ablation of silicon–modification thresholds and morphology  

Microsoft Academic Search

.   We investigated the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses\\u000a of 5 to 400 fs duration. In accordance with earlier established models, we found the phenomena amorphization, melting, re-crystallization,\\u000a nucleated vaporization, and ablation to occur with increasing laser fluence down to the shortest pulse durations. We noticed\\u000a new morphological features (bubbles) as well

J. Bonse; S. Baudach; J. Krüger; W. Kautek; M. Lenzner

2002-01-01

198

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

199

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

2012-01-01

200

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 an output above about 50 watts/cm2 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

2010-04-06

201

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

SciTech Connect

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. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada) [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Physics, Faculty of Sciences, Tanta University, Tanta (Egypt); Gagnon, J. E.; Fryer, B. J. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada) [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Earth and Environmental Sciences, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

2013-08-28

202

Femtosecond laser ablation of indium tin-oxide narrow grooves for thin film solar cells  

E-print Network

Femtosecond laser ablation of indium tin-oxide narrow grooves for thin film solar cells Qiumei Bian in revised form 15 June 2012 Accepted 18 June 2012 Keywords: Ablation Femtosecond laser Indium tin oxide a b of laser pulse duration, laser fluence and laser scanning speed on the ablation of ITO. The single pulse

Van Stryland, Eric

203

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

E-print Network

Background gas collisional effects on expanding fs and ns laser ablation plumes S. S. Harilal · N of a background gas on expanding ultrafast and short pulse laser ablation plumes were investigated by varying are observed *20­50 Torr for both ns and fs laser ablation plumes. The differences in laser­target and laser

Harilal, S. S.

204

Quantitative analysis by resonant laser ablation with optical emission detection: Resonant laser-induced breakdown spectroscopy  

Microsoft Academic Search

Resonant laser ablation (RLA) is a solid sampling technique that makes use of radiation trapping, and desorption induced by electronic transitions (DIET), to produce enhanced numbers of analyte atoms in the laser-induced plasma (LIP). This is achieved by tuning the laser ablation wavelength to a gas-phase resonant transition of the analyte. In this paper, RLA was coupled with detection of

Danielle Cleveland; Robert G. Michel

2010-01-01

205

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

206

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

SciTech Connect

This paper presents an overview of pulsed-laser ablation for film deposition and surface microstructure formation. By changing the ambient gas pressure from high vacuum to several Torr (several hundred Pa) and by selecting the pulsed-laser wavelength, the kinetic energy of ablated atoms/ions can be varied from several hundred eV down to {approximately}0.1 eV and films ranging from superhard to nanocrystalline may be deposited. Furthermore, cumulative (multi-pulse) irradiation of a semiconductor surface (e.g. silicon) in an oxidizing gas (0{sub 2}, SF{sub 6}) et atmospheric pressure can produce dense, self-organized arrays of high-aspect-ratio microcolumns or microcones. Thus, a wide range of materials synthesis and processing opportunities result from the hyperthermal flux and reactive growth conditions provided by pulsed-laser ablation.

Lowndes, D.H.

1999-11-08

207

Laser ablation of a turbid medium: Modeling and experimental results  

SciTech Connect

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

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

2006-08-01

208

Improved picosecond laser ablation with second harmonic seeding  

NASA Astrophysics Data System (ADS)

We report on recent results of laser ablation in semiconductors obtained by simultaneous irradiation of the sample with a superposition of the fundamental beam of a picosecond-Neodymium-Vanadate (Nd:VAN) laser (1064 nm, 10 ps pulse duration) and a small fraction of its second harmonic (SH) produced in a thin nonlinear crystal. In this fashion, the ablation yield could be increased by 70%. In addition, the ablation quality was improved in terms of surface smoothness. The underlying mechanism can be attributed to a 'seeding' of the target area with free carriers by the 532 nm radiation.

Zoppel, S.; Zehetner, J.; Reider, G. A.

2006-03-01

209

Reflection of femtosecond laser light in multipulse ablation of metals  

SciTech Connect

The shot-to-shot reflectance of high-intensity laser light is studied as a function of both the number of laser shots and laser fluence in multipulse ablation of a metal when the irradiated surface undergoes structural changes from an initially smooth surface to a deep crater. Our study shows that the reflectance of the irradiated surface significantly decreases due to the high intensity of laser pulses and the laser-induced surface structures in ablation regimes typically used for femtosecond laser processing of materials. The high-intensity effect dominates in the reflection reduction at low numbers of laser shots when laser-induced surface structures do not cause the reflectance to decrease noticeably. With increasing the number of laser shots, the structural effect comes into play, and both high-intensity and structural effects quickly reduce the reflectance of the sample to a low value.

Vorobyev, A. Y.; Guo Chunlei [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2011-08-15

210

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

211

Ablation enhancement of silicon by ultrashort double-pulse laser ablation  

SciTech Connect

In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1?ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1?ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

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

2014-09-15

212

MRI-guided laser ablation of neuroendocrine tumor hepatic metastases  

PubMed Central

Background Neuroendocrine tumors (NET) represent a therapeutically challenging and heterogeneous group of malignancies occurring throughout the body, but mainly in the gastrointestinal system. Purpose To describe magnetic resonance imaging (MRI)-guided laser ablation of NET liver metastases and assess its role within the current treatment options and methods. Material and Methods Two patients with NET tumor hepatic metastases were treated with MRI-guided interstitial laser ablation (LITT). Three tumors were treated. Clinical follow-up time was 10 years. Results Both patients were successfully treated. There were no local recurrences at the ablation site during the follow-up. Both patients had survived at 10-year follow-up. One patient is disease-free. Conclusion MRI-guided laser ablation can be used to treat NET tumor liver metastases but combination therapy and a rigorous follow-up schedule are recommended. PMID:24778794

Perälä, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriälä, Ilkka; Salmela, Pasi I; Tervonen, Osmo

2014-01-01

213

Excimer laser ablation of polymer-clay nanocomposites  

NASA Astrophysics Data System (ADS)

The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this work. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration. The excimer laser induced surface micro/nano structure formation and modification of PS-Clay Nanocomposites at various OMMT concentrations were also investigated. Scanning electron microscopy, atomic force microscopy and Fourier Transform Infrared (FTIR) spectroscopy with attenuated total reflectance accessory were utilized to analyze the ablated surface. Results show that, in general, better dispersion of OMMT leads to less continuous surface structures and more pronounced carbonyl regions on FTIR spectra. Clay nanoparticles are exposed on ablated surfaces and affect surface structure formation after irradiation by laser. A mechanism for the formation of excimer laser induced surface structures on injection molded parts is thus proposed.

Chang, I.-Ta

214

In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer  

NASA Technical Reports Server (NTRS)

A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) 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. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

2012-01-01

215

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

216

Separate Effects of the Microkeratome Incision and Laser Ablation on the Eye's  

E-print Network

Separate Effects of the Microkeratome Incision and Laser Ablation on the Eye's Wave Aberration, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ to the laser ablation and not the microkeratome cut. In addi- tion, the total and higher order root mean square

Williams, David

217

Velocity distributions of molecules ejected in laser ablation Leonid V. Zhigilei and Barbara J. Garrisona)  

E-print Network

Velocity distributions of molecules ejected in laser ablation Leonid V. Zhigilei and Barbara J applications of laser ablation are in mass spectrometry and thin film deposition. In mass spectrometry laser in laser ablation experiments for a variety of systems, such as mo- lecular solids,3,5 polymers,6,10 frozen

Zhigilei, Leonid V.

218

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

E-print Network

Dynamics of femto- and nanosecond laser ablation plumes investigated using optical emission plasmas, brass targets were ablated in vacuum employing pulses either from a Ti:Sapphire ultrafast laser of Physics. [http://dx.doi.org/10.1063/1.4764060] I. INTRODUCTION Laser ablation (LA) and laser

Harilal, S. S.

219

Emission features and expansion dynamics of nanosecond laser ablation plumes at different ambient pressures  

E-print Network

Emission features and expansion dynamics of nanosecond laser ablation plumes at different ambient deposition (PLD),1 laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS),2 laser.12 The interaction of a nanosecond laser ablation plume with an ambient gas has been studied

Harilal, S. S.

220

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

E-print Network

A Hybrid MD-DSMC Model of Picosecond Laser Ablation and Desorption Michael I. Zeifman* , Barbara J model of the evolution of a plume generated by laser ablation of an organic solid is presented and discussed. The first stage of the laser ablation involves laser coupling to the target and ejection

Zhigilei, Leonid V.

221

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 that a thin rim is formed around ablated craters after a single laser pulse. When multiple laser pulses. The substrates were cleaned ultrasonically with alcohol before the experiments. After laser ablation, the debris

Harkin, Anthony

222

Toward Single-Cell Analysis by Plume Collimation in Laser Ablation Electrospray Ionization Mass Spectrometry  

E-print Network

Toward Single-Cell Analysis by Plume Collimation in Laser Ablation Electrospray Ionization Mass is used to deliver laser energy to a sample in laser ablation electrospray ionization (LAESI) mass.g., laser ablation electrospray ionization (LAESI),12 among a host of others.13 Some ambient methods, e

Vertes, Akos

223

Combined molecular dynamicsdirect simulation Monte Carlo computational study of laser ablation plume evolution  

E-print Network

Combined molecular dynamics­direct simulation Monte Carlo computational study of laser ablation of evolution of a plume generated by laser ablation of an organic solid is proposed and developed. The first stage of the laser ablation, which involves laser coupling to the target and ejection of molecules

Zhigilei, Leonid V.

224

Page 2 of 55 Low-cost photomask fabrication using laser ablation  

E-print Network

Page 2 of 55 Accepted M anuscript 2 Low-cost photomask fabrication using laser ablation G. Legeaya-coated on titanium. It is ablated with partially-overlapping laser impacts and undergoes self-combustion under laser beam. Proper heat treatments are applied before and after laser ablation to circumvent smearing

225

MICROANALYSIS OF SIDEROPHILE ELEMENTS IN FREMDLINGE USING LASER ABLATION ICP-MS. A. J. Campbell  

E-print Network

MICROANALYSIS OF SIDEROPHILE ELEMENTS IN FREMDLINGE USING LASER ABLATION ICP-MS. A. J. Campbell 1@midway.uchicago.edu). Introduction: Laser ablation ICP mass spectrome- try has been used to measure distributions of the highly vein in Allende (CV3-oxidized). Experimental: The laser ablation system utilized a CETAC LSX-200 laser

Grossman, Lawrence

226

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@itap.physik.uni-stuttgart.de 1 Introduction Laser ablation is the process of removing material with very intensive, pulsed laser process itself still lacks behind. The time scales of the processes involved in laser ablation

Roth, Johannes

227

Solid sampling with 193-nm excimer laser ablation  

NASA Astrophysics Data System (ADS)

Reproducible and sensitive elemental analysis of solid samples is a crucial task in areas of geology (e.g. microanalysis of fluid inclusions), material sciences, industrial quality control as well as in environmental, forensic and biological studies. To date the most versatile detection method is mass-spectroscopic multi-element analysis. In order to obtain reproducible results, this requires transferring the solid sample into the gas-phase while preserving the sample's stoichiometric composition. Laser ablation in combination with Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a proven powerful technique to meet the requirements for reliable solid sample analysis. The sample is laser ablated in an air-tight cell and the aerosol is carried by an inert gas to a micro-wave induced plasma where its constituents are atomized and ionized prior to mass analysis. The 193 nm excimer laser ablation, in particular, provides athermal sample ablation with very precise lateral ablation and controlled depth profiling. The high photon energy and beam homogeneity of the 193 nm excimer laser system avoids elemental fractionation and permits clean ablation of even transmissive solid materials such as carbonates, fluorites and pure quartz.

Delmdahl, Ralph

2007-02-01

228

Ultrafast laser ablation ICP-MS: role of spot size, laser fluence, and repetition rate in signal intensity  

E-print Network

Ultrafast laser ablation ICP-MS: role of spot size, laser fluence, and repetition rate in signal,a Richard E. Russob and Ahmed Hassaneina Ultrafast laser ablation inductively coupled plasma mass system. Though ultrafast laser ablation sample introduction provides better accuracy and precision

Harilal, S. S.

229

Thermal ablation of liver metastases from colorectal cancer: radiofrequency, microwave and laser ablation therapies.  

PubMed

Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12-49 months follow-up, 2.7-12.5 % of MW ablated lesions at 5-19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4-33 % of patients treated with RF ablation, 0-19 % of patients treated with MW ablation and 0.1-3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases. PMID:24894923

Vogl, Thomas J; Farshid, Parviz; Naguib, Nagy N N; Darvishi, Abbas; Bazrafshan, Babak; Mbalisike, Emmanuel; Burkhard, Thorsten; Zangos, Stephan

2014-07-01

230

Parallel femtosecond laser ablation with individually controlled intensity.  

PubMed

The use of computer generated holograms together with spatial light modulator (SLM) enable highly parallel laser micromachining. Usually SLM is used for splitting the original laser beam to desired number of beams with equal intensity. However, this technique also enables that the intensity of every beam can be controlled individually. Example of the hologram designing procedure for separation of the original beam to 400 beams with individually controlled intensity is presented. The proposed technique is demonstrated by femtosecond laser ablation of grayscale pictures so that grey scale of the pixel is addressed with corresponding beam intensity in the ablated picture. PMID:24663553

Silvennoinen, Martti; Kaakkunen, Jarno; Paivasaari, Kimmo; Vahimaa, Pasi

2014-02-10

231

Ultrafast photographic investigation on laser ablation of liquid metals  

NASA Astrophysics Data System (ADS)

The application of laser pulses as `photographic flash' gives the possibility to record ultrafast phenomena. Since the duration of the laser pulses may be tuned from fs to cw, it is easy to choose a right laser source to resolve the time domain to be investigated. In this study excimer laser ablation of molten metal targets was followed by ultrafast photography based on delayed dye laser pulses. Molten tin and bismuth were ablated in vacuum by an ArF excimer laser. Pictures of the surface and the ablated material were taken at different moments after the start of the excimer laser pulse with temporal resolution of 1 ns. The series of snapshots contain information on the initial phase of plume formation in the ns time regime, and on liquid motion (surface waves, protuberances, liquid jet formations, splashing) in microsecond time scale. The important result of this study is the registration of the processes leading to droplet emission from the ablated target surface, because the elimination of droplets is a crucial requirement in depositing thin films by the pulsed laser deposition technique.

Toth, Zsolt; Smausz, Tomi; Hopp, Bela; Ignacz, Ferenc; Kantor, Zoltan; Szoerenyi, Tamas; Bor, Zsolt

1998-08-01

232

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

233

Thermal oxidative degradation of molybdenum films under laser ablation  

NASA Astrophysics Data System (ADS)

The problems of laser ablation of molybdenum films that are related to the formation of topological patterns of contact masks are discussed. The thermal oxidative degradation of thin molybdenum films under high-intensity laser irradiation is analyzed. The results of theoretical estimations are compared with the Raman data on the chemical composition of molybdenum oxide.

Volkov, A. V.; Kazanskiy, N. L.; Moiseev, O. Yu.; Poletayev, S. D.

2015-02-01

234

The physical mechanisms of short-pulse laser ablation  

Microsoft Academic Search

Time-resolved experiments demonstrate that the removal of material from the surface of metals and semiconductors following irradiation with pico- or femtosecond laser pulses occurs on a nanosecond time scale. It is shown that short-pulse laser ablation can be interpreted in terms of transient thermal processes involving states of matter with unusual thermodynamic, hydrodynamic and optical properties.

D. von der Linde; K. Sokolowski-Tinten

2000-01-01

235

Stereotactic laser ablation of high-grade gliomas.  

PubMed

Evolving research has demonstrated that surgical cytoreduction of a high-grade glial neoplasm is an important factor in improving the prognosis of these difficult tumors. Recent advances in intraoperative imaging have spurred the use of stereotactic laser ablation (laser interstitial thermal therapy [LITT]) for intracranial lesions. Among other targets, laser ablation has been used in the focal treatment of high-grade gliomas (HGGs). The revived application of laser ablation for gliomas parallels major advancements in intraoperative adjuvants and groundbreaking molecular advances in neuro-oncology. The authors review the research on stereotactic LITT for the treatment of HGGs and provide a potential management algorithm for HGGs that incorporates LITT in clinical practice. PMID:25434378

Hawasli, Ammar H; Kim, Albert H; Dunn, Gavin P; Tran, David D; Leuthardt, Eric C

2014-12-01

236

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

237

TEA CO2 laser ablation studies of Y-Ba-Cu-O  

NASA Astrophysics Data System (ADS)

Of the various lasers that have been used for the ablation of Y-Ba-Cu-O samples to form superconducting films from deposited products, UV excimer and visible systems have met with most success. TEA CO2 lasers provide an interesting, alternative, ablation source although, as yet, little work has been reported on the mechanisms involved at this longer wavelength. In this paper visible-UV spectroscopic and ion probe measurements on the ablation products from bulk Y-Ba-Cu-O targets irradiated using a TEA CO2 laser are reported. Information gained from the luminescent species recorded at various distances from the target and from non-species resolved ion-probe traces are reported and discussed. Relatively high plasma temperatures are duduced to occur at quite modest fluence levels. Etch-rate measurements show that material removal decreases beyond a certain fluence, probably as a result of shielding due to strong inverse bremmstrahlung absorption in the ablation plume. A comparison with similar studies conducted using the KrF excimer laser is made and the possible implications for film deposition discussed.

Dyer, P. E.; Greenough, R. D.; Issa, A.; Key, P. H.

1989-12-01

238

Laser ablation and arc\\/spark solid sample introduction into inductively coupled plasma mass spectrometers  

Microsoft Academic Search

Sample introduction using laser ablation and arc and spark ablation is reviewed. Few references were found in the literature on the use of spark or arc ablation as a sample introduction technique into the ICP-MS and emphasis is therefore placed on the use of laser ablation sampling, particularly for Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection; however, many of the

Detlef Günther; Simon E. Jackson; Henry P. Longerich

1999-01-01

239

Toward laser ablation Accelerator Mass Spectrometry of actinides  

SciTech Connect

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 highlycharged 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.

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

2013-01-01

240

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

241

CuBr laser ablation of titanium surface  

NASA Astrophysics Data System (ADS)

Interaction of a CuBr laser, operating at 511 nm wavelength and pulse duration of 30 ns with titanium wafers was studied. It was investigated the efficiency of laser ablation, depending on the laser fluence, on the laser beam scanning speed, and laser pulse frequency. The titanium surface modification was studied by scanning electron microscopy (SEM) and XPS (X-ray Photoelectron Spectroscopy). Nanosecond laser irradiation of Ti led to the formation of high porous granular structures consisting of agglomerated small micro- and sub microparticles.

Balchev, Ivaylo; Minkovski, Nikolay; Dimitrov, Krasimir; Atanasov, Atanas; Stefanov, Plamen

2015-01-01

242

Ultrashort pulse laser ablation of polycarbonate and polymethylmethacrylate  

Microsoft Academic Search

Ablation experiments with ultrashort laser pulses (pulse duration 150 fs, wavelength 800 nm) on polymers (PC, PMMA) relevant for biomedical technology have been performed in air. The lateral and vertical machining precision was evaluated by optical, atomic force and scanning electron microscopy. The ablation threshold reaches values in the range of 0.5–2.5 J\\/cm2 and depends significantly on the number of

S. Baudach; J Bonse; J Krüger; W Kautek

2000-01-01

243

Enhancement of laser ablation yield by two color excitation  

NASA Astrophysics Data System (ADS)

We present ablation results of silicon obtained by simultaneous irradiation of the sample with the fundamental beam of a picosecond-neodymium-vanadate (Nd:VAN) laser (1064 nm, 10 ps pulse duration) and a small amount of second harmonic (SH) produced in a thin nonlinear crystal. In this fashion, the ablation yield could be increased by 70%. In addition, the ablation quality was improved in terms of surface smoothness. The underlying mechanism can be attributed to a ‘seeding’ of the target area with free carriers by the 532 nm radiation.

Zoppel, S.; Merz, R.; Zehetner, J.; Reider, G. A.

2005-09-01

244

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

SciTech Connect

This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Environments; Determining {lambda}{sub o}; resonant refraction effects; fringe shift interpretation; shot-to-shot consistency; laser ablation in vacuum and low pressure, inert, background gas; theoretically modeling plume expansion in vacuum and low pressure, inert, background gas; and laser ablation in higher pressure, inert, background gas.

Lindley, R.A. [Michigan Univ., Ann Arbor, MI (United States)

1993-10-01

245

Pulsed laser ablation of dental calculus in the near ultraviolet.  

PubMed

Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ?8??J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5??J/cm2 but has not been observed above this fluence. PMID:24549442

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

2014-02-01

246

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

SciTech Connect

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

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

2010-10-13

247

Improved time control on Cretaceous coastal deposits: new results from Sr isotope measurements using laser ablation  

E-print Network

using laser ablation Stefan Burla,1 Felix Oberli,2 Ulrich Heimhofer,3 Uwe Wiechert4 and Helmut Weissert5 that laser ablation (LA) combined with multi-collector inductively cou- pled plasma mass spectrometry (MC

Gilli, Adrian

248

Wavelength-dependent fragmentation and clustering observed after femtosecond laser ablation of solid C{sub 60}  

SciTech Connect

We report here the resonance effect in femtosecond laser ablation of solid C{sub 60} by investigating wavelength and fluence dependence of product ion species. When the ablation laser wavelength is far from the molecular absorption band of C{sub 60}, we observe both C{sub 60-2n}{sup +} fragment ions and C{sub 60+2n}{sup +} cluster ions as well as C{sub 60}{sup +} parent ion. Delayed ionization of C{sub 60} is not significant. When the ablation laser wavelength is near resonant with the molecular absorption, we observe C{sub 60}{sup +} and some amount of C{sub 60-2n}{sup +} fragment ions depending on the laser fluence. Delayed ionization of C{sub 60} is significant in this case, which indicates high internal energy of C{sub 60} molecule. From the observations, we confirm the strong coupling of femtosecond laser energy with C{sub 60} molecule when the molecular absorption is high at the ablation laser wavelength.

Kobayashi, T.; Kato, T.; Matsuo, Y.; Kurata-Nishimura, M.; Hayashizaki, Y.; Kawai, J. [RIKEN Discovery Research Institute, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); RIKEN Genomic Science Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); RIKEN Genomic Science Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045 (Japan); RIKEN Discovery Research Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan and RIKEN Genomic Science Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045 (Japan)

2007-09-21

249

CO2 laser ablative etching of polyethylene terephthalate  

NASA Astrophysics Data System (ADS)

Films of polyethylene terephthalate (PET) can be successfully etched with 9 ?m radiation from a pulsed TEA CO2 laser. The relationship between etch depth and fluence is broadly similar to that observed for excimer laser etching but with a less well-defined threshold. Time-resolved photoacoustic measurements of stress waves generated in the interaction show that at a fluence of 1.8 J cm-2 ablation occurs 100 200 ns after the start of the laser pulse, a time which is consistent with the rate of thermal decomposition of PET. The volatile products of ablation are carbon monoxide, carbon dioxide, methane, ethyne, ethene, benzene, ethanal, and small quantities of other products. For fluences close to and appreciably above the threshold the ablated material consists predominantly of involatile species of relatively high molecular weight, whereas at higher fluences substantial fragmentation of the polymer to small molecules occurs.

Dyer, P. E.; Oldershaw, G. A.; Sidhu, J.

1989-06-01

250

Ablative fractional laser resurfacing helps treat restrictive pediatric scar contractures.  

PubMed

Conventional management of debilitating pediatric scar contractures, including hand therapy and surgery, may often be beset by delayed treatment, suboptimal results, and additional surgical morbidity. Ablative fractional laser resurfacing is an emerging adjunctive procedural option for scar contractures because of its promising efficacy and safety profile. However, its use to improve function has not been studied in the pediatric population. Herein we report 2 pediatric patients with recalcitrant scar contractures, causing persistent functional deficits, treated with an ablative fractional laser protocol. Both patients experienced rapid and cumulative subjective and objective improvements in range of motion and function as measured by an independent occupational therapist without reported complications. We highlight ablative fractional laser resurfacing as a novel and promising tool in the management of function-limiting scar contractures in children and propose that the technique be incorporated into existing scar treatment paradigms, guided by future research. PMID:25367535

Krakowski, Andrew C; Goldenberg, Alina; Eichenfield, Lawrence F; Murray, Jill-Peck; Shumaker, Peter R

2014-12-01

251

Pulsed laser ablation of Al Cu Fe quasicrystals  

NASA Astrophysics Data System (ADS)

Quasicrystalline Al65-Cu23-Fe12 targets have been ablated by a doubled Nd:YAG laser and deposited on silicon substrates. The results show evidence of distinct ablation mechanisms, which lead to different gas phase composition, as a function of the laser fluence. Films containing the quasicrystalline phase can be deposited only at fluences higher than about 6.5 J/cm2 while at lower fluences the aluminium content exceeds the stoichiometric value. The films obtained by laser ablation of quasicrystalline Al65-Cu23-Fe12 were compared with those obtained from the metallic alloy Al70-Cu20-Fe10. The differences between the two systems could be explained on the basis of the low thermal conductivity of the quasicrystalline phase.

Teghil, R.; D'Alessio, L.; Simone, M. A.; Zaccagnino, M.; Ferro, D.; Sordelet, D. J.

2000-12-01

252

Ultrafast laser ablation of gold thin film targets  

SciTech Connect

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

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

2011-12-15

253

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

254

Nanoscale patterning of graphene through femtosecond laser ablation  

SciTech Connect

We report on nanometer-scale patterning of single layer graphene on SiO{sub 2}/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 SiO{sub 2} 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.; Akturk, S., E-mail: selcuk.akturk@itu.edu.tr [Department of Physics, Istanbul Technical University, Maslak 34469, Istanbul (Turkey); Simsek, E. [Electrical and Computer Engineering, The George Washington University, Washington, DC 20052 (United States)

2014-02-03

255

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

NASA Astrophysics Data System (ADS)

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

Vaezzadeh, Majid; Saeidi, Mohammadreza; Zarei, Mohsen

2010-03-01

256

Glass particles produced by laser ablation for ICP-MSmeasurements  

SciTech Connect

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

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

2007-06-01

257

Visual servoing of a laser ablation based cochleostomy  

NASA Astrophysics Data System (ADS)

The aim of this study is a defined, visually based and camera controlled bone removal by a navigated CO II laser on the promontory of the inner ear. A precise and minimally traumatic opening procedure of the cochlea for the implantation of a cochlear implant electrode (so-called cochleostomy) is intended. Harming the membrane linings of the inner ear can result in damage of remaining organ functions (e.g. complete deafness or vertigo). A precise tissue removal by a laser-based bone ablation system is investigated. Inside the borehole the pulsed laser beam is guided automatically over the bone by using a two mirror galvanometric scanner. The ablation process is controlled by visual servoing. For the detection of the boundary layers of the inner ear the ablation area is monitored by a color camera. The acquired pictures are analyzed by image processing. The results of this analysis are used to control the process of laser ablation. This publication describes the complete system including image processing algorithms and the concept for the resulting distribution of single laser pulses. The system has been tested on human cochleae in ex-vivo studies. Further developments could lead to safe intraoperative openings of the cochlea by a robot based surgical laser instrument.

Kahrs, Lüder A.; Raczkowsky, Jörg; Werner, Martin; Knapp, Felix B.; Mehrwald, Markus; Hering, Peter; Schipper, Jörg; Klenzner, Thomas; Wörn, Heinz

2008-03-01

258

Laser ablation of a platinum target in water. II. Ablation rate and nanoparticle size distributions  

SciTech Connect

This is the second in a series of three papers examining nanomaterial formation in laser ablation in liquids (LAL). Here we study the effect of the laser wavelength and fluence on the mass yield and size distribution of nanoparticles prepared by laser ablation of a platinum target immersed in water. For all wavelengths tested, laser fluences in the range of 10-70 J/cm{sup 2} resulted in spheroidal, nonagglomerated platinum nanoparticles with sizes ranging from 1 to 30 nm. Nanoparticle size distributions are found to be composed of two modes that are attributed to thermal vaporization and explosive boiling mechanisms. The peak of the smaller size mode remains nearly constant at 3 nm for all laser conditions, which is suggested to be due to the strong confinement of the vapor plume by the liquid. The larger size mode peaks in the range of 5-15 nm with a population that is strongly dependent on the laser parameters. It is concluded that changes in the mean size reported in many earlier studies on LAL of metal targets are a result of the relative quantity of nanoparticles from each mechanism rather than direct control over the ablation process. Additionally, it was observed that the yield of platinum nanoparticles was significantly larger for 1064 nm wavelength at fluences greater than 10 J/cm{sup 2}. The maximum ablation rate was approximately 4.4 mg/h, with an estimated ablation and collection efficiency of 0.9 {mu}g/J. Dependence of the mass yield on wavelength and fluence is seen to be dependent primarily on the extent of the explosive mechanism.

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

259

The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled  

E-print Network

The effect of ultrafast laser wavelength on ablation properties and implications on sample wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate

Harilal, S. S.

260

Laser Ablative Structural Modification of Poly(ethylene-alt-maleic anhydride)  

E-print Network

Laser Ablative Structural Modification of Poly(ethylene-alt-maleic anhydride) Josef Pola Manuscript Received July 30, 2003 Pulsed IR laser ablation of poly(ethylene-alt-maleic anhydride) results rare example of laser ablative deposition of polymeric films that are structurally identical

Masoudi, Husain M.

261

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

E-print Network

The role of laser wavelength on plasma generation and expansion of ablation plumes in air A. E to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser

Harilal, S. S.

262

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 silicates has previously been accomplished only by combining laser ablation ICP-MS with electron microprobe a method for laser ablation ICP-MS analysis of major elements in silicate glasses and minerals that, when

Weston, Ken

263

High-Resolution Optical Coherence Tomography-Guided Laser Ablation of Surgical Tissue1  

E-print Network

High-Resolution Optical Coherence Tomography-Guided Laser Ablation of Surgical Tissue1 Stephen A backscattering properties of tissue, changes in tissue optical properties due to sur- gical laser ablation should to guide the placement and observe the dynamics of surgical laser ablation in a variety of tissue types

Boppart, Stephen

264

Phase explosion and its time lag in nanosecond laser ablation Xianfan Xu*  

E-print Network

Phase explosion and its time lag in nanosecond laser ablation Xianfan Xu* School of Mechanical kinetics during nanosecond pulsed excimer ablation of a metal. During laser heating, the surface can reach in ablation induced by nanosecond or shorter pulsed lasers. This paper discusses experiments for investigating

Xu, Xianfan

265

Analyses of femtosecond laser ablation of Ti, Zr and Hf. D. Grojo, J. Hermann*  

E-print Network

Analyses of femtosecond laser ablation of Ti, Zr and Hf. D. Grojo, J. Hermann* , S. Bruneau and T ABSTRACT Femtosecond laser ablation of Ti, Zr and Hf has been investigated by means of in-situ plasma ablation process. The expansion behaviour of these two components has been analysed as a function of laser

Paris-Sud XI, Université de

266

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement irradiation regimes  

E-print Network

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement material ejection at laser fluences above the ablation threshold. This phase explosion leads and photomechanical processes in laser ablation. In the present study we apply a molecular-level simulation technique

Zhigilei, Leonid V.

267

Time of Flight Mass Spectroscopy of Femtosecond Laser Ablation of Solid Surfaces  

E-print Network

1 Time of Flight Mass Spectroscopy of Femtosecond Laser Ablation of Solid Surfaces A. Cavalleri, K boiling causes material removal. After excitation with femtosecond laser pulses, ablation can be achieved with a 100 fs, 620 nm laser pulse. In order to provide information on single shot ablation, the sample

von der Linde, D.

268

Femtosecond laser-induced ablation of graphite K. Sokolowski-Tinten1  

E-print Network

Femtosecond laser-induced ablation of graphite K. Sokolowski-Tinten1 , S. Kudryashov1 , V. Temnov1 the changes of the interatomic potentials due to electronic excitation. Femtosecond laser ablation of solids experimental and theoretical study of ultrashort laser pulse ablation of graphite, emphasizing how the specific

von der Linde, D.

269

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 dynamics model was developed for the ablation of water-rich targets by infrared laser pulses at atmospheric explosion on laser ablation dynamics, and it is relevant for the preparative, analytical, and medical

Vertes, Akos

270

Metal ablation by picosecond laser pulses: A hybrid simulation Carsten Schafer and Herbert M. Urbassek*  

E-print Network

Metal ablation by picosecond laser pulses: A hybrid simulation Carsten Scha¨fer and Herbert M 2002; published 5 September 2002 We investigate picosecond laser ablation of metals using a hybrid UV laser irradiation of copper, we investigate the fluence dependence of the ablation yield

Zhigilei, Leonid V.

271

High-throughput metal nanoparticle catalysis by pulsed laser ablation Selim Senkan a,*, Michael Kahn a  

E-print Network

High-throughput metal nanoparticle catalysis by pulsed laser ablation Selim Senkan a,*, Michael online 18 July 2006 Abstract A high-throughput pulsed laser ablation (HT-PLA) system was developed for the preparation of multi-metallic nanoparticles that are anchored to the support materials. Pulsed laser ablation

Senkan, Selim M.

272

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 of the laser fluence in the form of D2 =2w0 2 ln F0/Fth N=1 provides the single-shot ablation threshold, Fth N

Byer, Robert L.

273

A Low Diffraction Laser Beam as Applied to Polymer Ablation Xuanhui Lu*  

E-print Network

A Low Diffraction Laser Beam as Applied to Polymer Ablation Xuanhui Lu* , Y. Lawrence Yao , and Kai that of a Gaussian beam. The effects of the improved beam quality on laser ablation process are investigated on polymeric material. A theoretical model is provided to predict laser ablated hole profile

Yao, Y. Lawrence

274

Summer 2010 Pulsed Laser Ablation of solid targets in a liquid  

E-print Network

Summer 2010 #12; Pulsed Laser Ablation of solid targets in a liquid environment has proved will be presented. #12;A high power laser is used to vaporize the target in an ablation plume. The particles (CVD)- APPROX. 100% FORMS NANOTUBES. Simply because Laser Ablation offers a very versatile means

Baltisberger, Jay H.

275

Catalytic nanoparticles for carbon nanotube growth synthesized by through thin film femtosecond laser ablation  

E-print Network

laser ablation C. M. Rouleau,1* M. Tian,2 A. A. Puretzky,1 M. Mahjouri-Samani,1 G. Duscher,2 and D. B of femtosecond-based through thin film laser ablation (TTFA) to that of ns TTFA, and testing the feasibility-described through thin film ablation (TTFA) and laser-induced jets of nanoparticle arrays, respectively, to create

Geohegan, David B.

276

Photoluminescence from gas-suspended SiOx nanoparticles synthesized by laser ablation  

E-print Network

Photoluminescence from gas-suspended SiOx nanoparticles synthesized by laser ablation David BOx particles formed by laser ablation of Si into 1­10 Torr He and Ar. Three spectral bands 1.8, 2.5 and 3.2 e clusters of 30 atoms .2 Laser ablation is a versatile vaporization tool, and has recently been used to form

Geohegan, David B.

277

Combining cell microdissection ... ... with laser ablation electrospray ionization (LAESI) mass spectrometry enables the  

E-print Network

. Combining cell microdissection ... ... with laser ablation electrospray ionization (LAESI) mass Gradients in Single Cells by Laser Ablation Electrospray Ionization Mass Spectrometry** Jessica A. Stolee are not available for analysis.[29­31] In laser ablation electrospray ionization (LAESI) of biological samples

Vertes, Akos

278

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. Our observations show that a thin rim is formed around ablated craters after a single laser pulse writing of microchannels in glass.3­6 Using this laser ablation technique, it is possible to fabricate

Byer, Robert L.

279

EFFECT OF PULSING PARAMETERS ON LASER ABLATIVE CLEANING OF COPPER Paper # M602  

E-print Network

EFFECT OF PULSING PARAMETERS ON LASER ABLATIVE CLEANING OF COPPER OXIDES Paper # M602 Jie Zhang the laser ablative cleaning process. In the model, property discontinuity and Stephan and kinetic boundary based on the working mechanism of laser ablation. Copper is the most widely utilized metal

Yao, Y. Lawrence

280

Laser Ablation Electrospray Ionization for Atmospheric Pressure Molecular Imaging Mass Spectrometry  

E-print Network

Chapter 9 Laser Ablation Electrospray Ionization for Atmospheric Pressure Molecular Imaging Mass Spectrometry Peter Nemes and Akos Vertes Abstract Laser ablation electrospray ionization (LAESI) is a novel-IR) MALDI (3), laser ablation S.S. Rubakhin, J.V. Sweedler (eds.), Mass Spectrometry Imaging, Methods

Vertes, Akos

281

A low diffraction laser beam as applied to polymer ablation Xuanhui Lu,a)  

E-print Network

A low diffraction laser beam as applied to polymer ablation Xuanhui Lu,a) Y. Lawrence Yao beam. The effects of the improved beam quality on a laser ablation process are investigated using a polymeric material. A theoretical model is provided to predict the laser ablated hole profile

Yao, Y. Lawrence

282

Photochemical fragmentation processes in laser ablation of organic Yaroslava G. Yingling a,*, Leonid V. Zhigilei b  

E-print Network

Photochemical fragmentation processes in laser ablation of organic solids Yaroslava G. Yingling a) laser ablation of molecular solids have received considerable attention due to its proven and potential applications. Despite its active practical use the mechanisms of laser ablation are still being studied

Zhigilei, Leonid V.

283

Sediment profiles of less commonly determined elements measured by Laser Ablation ICP-MS  

E-print Network

Sediment profiles of less commonly determined elements measured by Laser Ablation ICP on a short list of high-abundance trace elements. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry of this investigation is to harness the analytical power of Laser Ablation ICP-MS to explore the behavior of a large

Mcdonough, William F.

284

RAPID COMMUNICATION Quantifying the quality of femtosecond laser ablation of graphene  

E-print Network

RAPID COMMUNICATION Quantifying the quality of femtosecond laser ablation of graphene Ramazan Sahin laser ablation [9­19] might be a simple yet efficient alternative technique compared to standard litho, femtosecond (fs) laser ablation provides high quality and repeatable struc- tures due to its non

Simsek, Ergun

285

Laser ablation atmospheric pressure photoionization mass spectrometry imaging of phytochemicals from sage leaves  

E-print Network

Laser ablation atmospheric pressure photoionization mass spectrometry imaging of phytochemicals. In this contribution, we explore the feasibility of laser ablation atmospheric pressure photoionization (LAAPPI-time-of-flight (TOF)-MSI without any sample preparation. Leaf mass spectra were also recorded with laser ablation

Vertes, Akos

286

Mechanisms of small clusters production by short and ultra-short laser ablation  

E-print Network

Mechanisms of small clusters production by short and ultra-short laser ablation Tatiana E. Itina a The mechanisms involved into the formation of clusters by pulsed laser ablation are studied both numerically ablation: (i) direct cluster ejection upon the laser-material interaction, and (ii) collisional sticking

Zhigilei, Leonid V.

287

Characterization of hydrocarbon and mixed layers in TEXTOR by laser induced ablation spectroscopy  

E-print Network

Characterization of hydrocarbon and mixed layers in TEXTOR by laser induced ablation spectroscopy in TEXTOR by laser induced ablation spectroscopy N Gierse1,2 , S Brezinsek1 , T F Giesen2 , A Huber1 , M systematic laser-induced ablation spectroscopy (LIAS) measurements carried out on various surface layers

Giesen, Thomas

288

Multiscale simulation of laser ablation of organic solids: evolution of the plume  

E-print Network

Multiscale simulation of laser ablation of organic solids: evolution of the plume Michael I. The combined multiscale model addresses different processes involved in the laser ablation phenomenon distribution 1. Introduction The need to understand the mechanisms of plume expansion in laser ablation

Zhigilei, Leonid V.

289

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 investigated the time evolution of nickel ablation induced by high-energy picosecond laser pulses. A Nd.V. All rights reserved. Keywords: Picosecond laser; Ablation; Heat transfer; Homogeneous nucleation

Xu, Xianfan

290

Limit of overheating and the threshold behavior in laser ablation Barbara J. Garrison  

E-print Network

Limit of overheating and the threshold behavior in laser ablation Barbara J. Garrison Department, designed to examine the threshold behavior in laser ablation, demonstrate that the rate of homogeneous demonstrated and ana- lytic theories 3 have predicted that there is a threshold for pulsed laser ablation

Zhigilei, Leonid V.

291

Precise ablation milling with ultrashort pulsed Nd:YAG lasers by optical and acoustical process control  

Microsoft Academic Search

Laser ablation milling with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials like metals, ceramics and polymers. A precise machining result with high surface quality requires a defined ablation process. Problems arise through the scatter in the resulting ablation depth of the laser beam machining process where material is removed in layers. Since

Volker Schulze; Patricia Weber

2010-01-01

292

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

293

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

294

Broadening of the spectral lines of a buffer gas and target substance in laser ablation  

SciTech Connect

The broadening of discrete spectral lines from the plasma produced in the laser ablation of metal targets in a broad pressure range (10{sup 2} - 10{sup 7} Pa) of the ambient gas (Ar, He, H{sub 2}) was studied experimentally. The behaviour of spectral line broadening for the buffer gases was found to be significantly different from that for the atoms and ions of the target material. In comparison with target atoms, the atoms of buffer gases radiate from denser plasma layers, and their spectral line profiles are complex in shape. (interaction of laser radiation with matter. laser plasma)

Kask, Nikolai E; Michurin, Sergei V [D.V. Skobel'tsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2012-11-30

295

Lasers in Surgery and Medicine 40:483493 (2008) Effects of Laser Repetition Rate on Corneal Tissue Ablation  

E-print Network

Ablation for 193-nm Excimer Laser Light Leia M. Shanyfelt, MS,1 Pamela L. Dickrell, PhD,1 Henry F generated at laser repetition rates of up to 400 Hz are comparable to ablations performed at rates effects of excimer laser repetition rate on the overall corneal ablation metrics revealed no measurable

Hahn, David W.

2008-01-01

296

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

297

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

298

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

299

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

300

Effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion  

Microsoft Academic Search

Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion. A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 mum, 30 J pulse energy was used to ablate water contained in a quadrate quartz

C. Y. Cui; Y. J. Hong; J. F. Ye; M. Wen; N. L. Li

2011-01-01

301

Endometrial laser ablation in rabbits: A comparative study of three laser types  

SciTech Connect

Endometrial laser ablation is one of the alternatives to hysterectomy in cases of intractable uterine bleeding. It is currently performed using the Nd:YAG laser at 1.06 microns. The aim of this study was to compare the tissue effect of three types of laser irradiation (Nd:YAG laser at 1.06 and 1.32 microns and holmium laser at 2.12 microns) on the rabbit endometrium. Crater formation, coagulation necrosis, and muscle necrosis were evaluated at the time of ablation, as well as at 1 week and 4 weeks postablation. The results were assessed by determining the depth and width of the affected portion in the uterine wall (lumen to serosa). It was shown that Nd:YAG laser at 1.32 microns caused more generalized and extended effects as compared with the other laser types examined. Endometrial regeneration was faster after ablation by the Nd:YAG laser at 1.06 microns and the holmium laser than by the Nd:YAG laser at 1.32 microns. The widest range of ablation energy (defined as that causing ablation without muscle damage) was achieved by applying the holmium laser. Further evaluation of the holmium laser for this indication is recommended.

Rosenberg, C.; Tadir, Y.; Braslavsky, D.; Fisch, B.; Karni, Z.; Ovadia, J. (Beilinson Medical Center, Tel Aviv (Israel))

1990-01-01

302

Detection efficiencies in nano- and femtosecond laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Detection efficiencies of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), defined as the ratio of ions reaching the detector and atoms released by LA were measured. For this purpose, LA of silicate glasses, zircon, and pure silicon was performed using nanosecond (ns) as well as femtosecond (fs) LA. For instance, ns-LA of silicate glass using helium as in-cell carrier

M. Wälle; J. Koch; L. Flamigni; S. Heiroth; T. Lippert; W. Hartung; D. Günther

2009-01-01

303

The formation mechanism of clusters produced by laser ablation of solid sodium azide  

NASA Astrophysics Data System (ADS)

The mass spectra of sodium azide (NaN3) cluster ions, produced by 532 nm laser ablation of a solid NaN3 sample, were measured by a time-of-flight (TOF) mass spectrometer. The spectra showed that most of the cluster ions could be ascribed to the following series: Nan?, (NaN3)n?, Na(NaN3)n?, N3(NaN3)n?, Nan+, Nan(NaN3)+ and Na2(NaN3)n+. According to the possible distribution of the ions, possible formation mechanisms of NaN3 clusters are proposed.

Zhang, Wei; Shen, Ruiqi; Wu, Lizhi; Ye, Yinghua; Hu, Yan; Zhu, Peng

2013-02-01

304

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

305

Laser Ablative Shaping of Plastic Optical Components for Phase Control  

NASA Astrophysics Data System (ADS)

A new scheme for phase control of optical components with laser ablation has been developed. One can ablate the surface shape of optical plastic material coated on a glass plate by using 193-nm laser light to control the transmission wave front. The surface shape is monitored in situ and corrected to attain the desired aberration level. The irradiation fluence is approximately 40 mJ cm 2 , and the ablation depth pulse is approximately 0.01 m pulse for UV-cured resin. A wave-front aberration of 3.0 is reduced to 0.17 for flat surface shaping. For spherical surface generation, an aberration of 2.5 is reduced to 0.2 . The increase in surface roughness is kept within acceptable levels.

Jitsuno, Takahisa; Tokumura, Keiu; Nakashima, Nobuaki; Nakatsuka, Masahiro

1999-05-01

306

Excimer laser ablation of thick SiOx-films: Etch rate measurements and simulation of the ablation threshold  

NASA Astrophysics Data System (ADS)

Excimer laser ablation of 4.5 ?m thick SiOx-films with x ? 1 is investigated at 193 nm, 248 nm, and 308 nm. Strong absorption enables precisely tunable removal depths. The ablation rates correlate with laser penetration depths calculated from low level absorption coefficients. The experimental ablation thresholds are in agreement with numerical simulations on the basis of linear absorption and one-dimensional heat flow. This behaviour is similar to that of strongly UV-absorbing polymers, leading to well controllable micro machining prospects. After laser processing, SiOx can be converted to SiO2, opening a route to laser based fabrication of micro optical components.

Ihlemann, J.; Meinertz, J.; Danev, G.

2012-08-01

307

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation  

NASA Astrophysics Data System (ADS)

Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

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

2007-04-01

308

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

309

The physics of UV laser cornea ablation  

Microsoft Academic Search

Experiments to determine the optimum parameters of an excimer irradiation of the cornea for clinical application are reported. The materials, procedures, and results are described. A theoretical model of cornea ablation that takes into consideration the thermal effects and mechanical stresses is suggested

Moishe S. Kitai; Valery L. Popkov; V. A. Semchischen; Alexei A. Kharizov

1991-01-01

310

Pulsed laser ablation of pepsin on an inorganic substrate  

NASA Astrophysics Data System (ADS)

Pressed pepsin pellets used as targets were ablated with the pulses of the Nd-YAG laser. The activity of the pepsin thin layer, deposited on a glass substrate, was successfully detected by analyzing the proteolytic degradation areas on the polyacrylamide gel (PA-gel) copolymerized with albumin from the hen egg white (ovalbumin), used as an enzymatic substrate.

Cicco, N.; Lopizzo, T.; Marotta, V.; Morone, A.; Verrastro, M.; Viggiano, V.

2009-03-01

311

Synthesis of cubic ruthenium nitride by reactive pulsed laser ablation  

Microsoft Academic Search

The recent synthesis of platinum nitride opens the possibility of novel platinum-group metal nitrides to exist. In this work we report the synthesis of ruthenium nitride by reactive pulsed laser ablation. Several plausible structures have been evaluated by ab initio calculations using the full potential linearized augmented plane wave method, in order to investigate the ruthenium nitride structural and electronic

M. G. Moreno-Armenta; J. Diaz; A. Martinez-Ruiz; G. Soto

2007-01-01

312

Direct writing of microlenses in polycarbonate with excimer laser ablation  

Microsoft Academic Search

A method for fabricating microlenses in polycarbonate material is reported. Using a direct-write technique based on scanning excimer laser ablation with a circular beam, we can etch an arbitrary shape in the polymer material. The beam is obtained by imaging a circular aperture onto the polymer surface, and scanning is realized by the translation stage carrying the sample, which makes

Kris Naessens; Heidi Ottevaere; Roel Baets; Peter van Daele; Hugo Thienpont

2003-01-01

313

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

E-print Network

Laser ion source for Columbia UniversityÕs 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

314

Ablation by short optical and x-ray laser pulses  

Microsoft Academic Search

The paper is devoted to experimental and theoretical studies of ablation of condensed matter by optical (OL), extreme ultraviolet (EUV) and X-ray lasers (XRL). Results obtained at two different XRL are compared. The first XRL is collision Ag-plasma laser with pulse duration tauL = 7 ps and energy of quanta hv=89.3 eV, while the second one is EUV free electron

N. A. Inogamov; S. I. Anisimov; V. V. Zhakhovsky; A. Ya. Faenov; Yu. V. Petrov; V. A. Khokhlov; V. E. Fortov; M. B. Agranat; S. I. Ashitkov; P. S. Komarov; I. Yu. Skobelev; Y. Kato; T. A. Pikuz; V. V. Shepelev; Y. Fukuda; M. Tanaka; M. Kishimoto; M. Ishino; M. Nishikino; M. Kando; T. Kawachi; M. Nagasono; H. Ohashi; M. Yabashi; K. Tono; Y. Senba; T. Togashi; T. Ishikawa

2010-01-01

315

Laser ablation\\/ionization mass spectrometry on tokamak deposition probes  

Microsoft Academic Search

Laser ablation-ionization mass spectrometric surface analysis was applied in plasma diagnostic experiments on the MT-1M tokamak. Non-intrinsic impurities were injected into the discharges using laser blow-off in order to study the impurity transport processes. High purity silicon samples were used as deposition probes in the edge plasma of the tokamak. The distributions of the impurities deposited on the probe surfaces

M. Á. Kedves; J. S. Bakos; P. N. Ignácz; B. Kardon; J. Szigeti

1996-01-01

316

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

317

Laser ablation in a model two-phase system Gareth J. Williams a,*, Leonid V. Zhigilei a,b  

E-print Network

Laser ablation in a model two-phase system Gareth J. Williams a,*, Leonid V. Zhigilei a,b , Barbara, University of Virginia, Charlottesville, VA 22903, USA Abstract Short pulse laser ablation of a model two methods; Laser ablation of hard tissue 1. Introduction Laser ablation is an increasingly important

Zhigilei, Leonid V.

318

Picosecond laser ablation of nickel-based superalloy C263  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

319

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

Microsoft Academic Search

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

Seung H. Ko; Heng Pan; David J. Hwang; Jaewon Chung; Sangil Ryu; Costas P. Grigoropoulos; Dimos Poulikakos

2007-01-01

320

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

321

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

322

Comparison of ablation stake measurements and Airborne Laser Scanning results  

NASA Astrophysics Data System (ADS)

Ablation measurements using ablation stakes are a well-established method in glaciology, which sees a lot of use. However, ablation stakes cannot always be installed and read at a sufficient number of points on a glacier or on multiple glaciers, due to limited personnel and financial capacities or because of inaccessible areas due to dangerous zones (crevasses, rock falls, avalanches) or remote terrain. Furthermore, ablation stakes only enable measurements of surface melt, whereas basal or internal melt processes as well as surface change related to glacier dynamics cannot be measured. Multi temporal Airborne laser scanning (ALS) can provide high resolution and very accurate topographic information for the whole glacier area, which allows the calculation of the difference in surface height and therefore - if the density profile is known or can be estimated - the determination of the local mass balance, including processes like basal melt at least to a certain degree. To gain a better understanding of the differences between ablation stake readings and differential ALS data at the stake locations, the results of both methods have been compared in detail. At Langenferner, a glacier in the Italian Eastern Alps, where mass balance measurements have been carried out since 2004, three ALS campaigns have been conducted at the end of the hydrological year in 2005, 2010 and 2013. There are about 30 ablation stakes installed at the glacier, which have been read during or very close to the time of the flight campaigns. The ablation measurements are then compared to the surface differences calculated from ALS data at the locations of the ablation stakes. To take the movement of the stakes due to glacier dyanmics into account, the position of the stakes has been measured with a differential GPS.

Rieg, Lorenzo; Galos, Stephan; Klug, Christoph; Sailer, Rudolf

2014-05-01

323

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

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

324

Zirconium carbide thin films deposited by pulsed laser ablation  

NASA Astrophysics Data System (ADS)

A study of the laser ablation and deposition of zirconium carbide has been carried out in our laboratory. The target has been vaporised by a doubled Nd:YAG laser and the ablation plume has been characterised by time-of-flight mass spectrometry, emission spectroscopy and ultrafast imaging performed by an Intensified Coupled Charge Device (ICCD). The results show a single ablation mechanism in the whole range of laser fluence used in the experiments (0.5-15 J/cm2) and this is quite different from the case of TiC. The gas phase data are confirmed by the analysis of the films deposited on oriented silicon. In fact, by X-ray diffraction and subsequent XPS analysis, their composition is fluence independent leading to films with constant characteristics on a large range of experimental conditions. The difference between ZrC and TiC ablation mechanisms may be explained in terms of chemical-physical properties and thermodynamic considerations which can also clarify the gas phase composition.

D'Alessio, L.; Santagata, A.; Teghil, R.; Zaccagnino, M.; Zaccardo, I.; Marotta, V.; Ferro, D.; De Maria, G.

2000-12-01

325

Pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser ablation of fibrocartilage and articular cartilage  

Microsoft Academic Search

A new, near-infrared, pulsed holmium laser (wave length, 2.1 ?m; pulse duration, 400 ?s) was used to ablate bovine articular cartilage and meniscal fibrocar tilage. Microscopic examination revealed zones of ther mal damage extending 550 ?m from ablation sites. Ablation rates were measured with a mass loss tech nique. Above threshold, mass removal rates were pro portional to laser radiant

Kenneth Trauner; Norman Nishioka; Dinesh Patel

1990-01-01

326

Vitreoretinal Ablation With the 193-nm Excimer Laser in Fluid Media  

E-print Network

Vitreoretinal Ablation With the 193-nm Excimer Laser in Fluid Media Daniel Palanker,* Itzhak Hemo of the laser. Ablation occurred only when the tip was held in contact with the tissue. Conclusions,-\\ Igor Turovets* Hanan Zauberman,\\ Galina Fish,* and Aaron Lewis* Purpose. To ablate retina and vitreous

Palanker, Daniel

327

Ultraviolet laser ablation of polycarbonate and glass in air  

SciTech Connect

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

Bormotova, T. A.; Blumenthal, R. [Auburn University, Alabama 36849 (United States)

2009-02-01

328

Generic incubation law for laser damage and ablation thresholds  

NASA Astrophysics Data System (ADS)

In multi-pulse laser damage and ablation experiments, the laser-induced damage threshold (LIDT) usually changes with the number of pulses in the train, a phenomenon known as incubation. We introduce a general incubation model based on two physical mechanisms—pulse induced change of (i) absorption and (ii) critical energy that must be deposited to cause ablation. The model is applicable to a broad class of materials and we apply it to fit data for dielectrics and metals. It also explains observed changes of the LIDT as a function of the laser repetition rate. We discuss under which conditions the crater-size method to determine LIDTs can be applied in multi-pulse experiments.

Sun, Zhanliang; Lenzner, Matthias; Rudolph, Wolfgang

2015-02-01

329

Ultrafast laser ablation of metal films on flexible substrates  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

330

Heat diffusion and ablation front dynamics in Er:YAG laser skin resurfacing  

NASA Astrophysics Data System (ADS)

Influence of pulse energy, duration and beam cross-section on the outcome of Er:YAG laser ablation of skin is interpreted on the basis of an analytical model of heat diffusion and ablation front dynamics. Derived expressions enable us to identify different ablation regimes in terms of ablation efficiency and depth of thermally affected tissue layer for any thermally driven laser ablation process. Influence of laser wavelength is also discussed, focusing on a comparison between Er:YAG and carbon-dioxide laser skin resurfacing. Preliminary experimental and clinical evidence in agreement with the model is also presented.

Majaron, Boris; Lukac, Matjaz; Drnovsek-Olup, Brigita; Vedlin, Boris; Rotter, Aleksander

1997-05-01

331

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

SciTech Connect

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

Zhang Hao; Oosten, D. van; Krol, D. M.; Dijkhuis, J. I. [Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80000, 3508 TA Utrecht (Netherlands)

2011-12-05

332

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

PubMed Central

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

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

2013-01-01

333

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

334

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

Microsoft Academic Search

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

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

2008-01-01

335

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

Microsoft Academic Search

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

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

2008-01-01

336

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

337

Planar laser-driven ablation model for nonlocalized absorption  

SciTech Connect

A model for planar laser-driven ablation is presented. Nonlocalized inverse bremsstrahlung absorption of laser energy at a density {ital n}{sub 1}{lt}{ital n}{sub {ital c}} is assumed. A steady-state solution in the conduction zone is joined to a rarefaction wave in the underdense plasma. The calculations relate all steady-state fluid quantities to only the material, absorbed intensity, and laser wavelength. The theory agrees well with results from a computer hydrodynamics code MEDUSA (Comput. Phys. Commun. {bold 7}, 271 (1974)) and experiments.

Dahmani, F.; Kerdja, T. (Haut Commissariat a la Recherche/CDTA, Laboratorire de Fusion Thermonucleaire, 2, Bd Frantz Fanon, BP 1017 Alger-Gare, Algiers, Algeria (DZ))

1991-05-01

338

PREFACE AND CONFERENCE INFORMATION: Eighth International Conference on Laser Ablation  

NASA Astrophysics Data System (ADS)

Laser ablation encompasses a wide range of delicate to extreme light interactions with matter that present considerably challenging problems for scientists to study and understand. At the same time, laser ablation also represents a basic process of significant commercial importance in laser material processing—defining a multi-billion dollar industry today. These topics were widely addressed at the 8th International Conference on Laser Ablation (COLA), held in Banff, Canada on 11-16 September 2005. The meeting took place amongst the majestic and natural beauty of the Canadian Rocky Mountains at The Banff Centre, where delegates enjoyed many inspiring presentations and discussions in a unique campus learning environment. The conference brought together world leading scientists, students and industry representatives to examine the basic science of laser ablation and improve our understanding of the many physical, chemical and/or biological processes driven by the laser. The multi-disciplinary research presented at the meeting underlies some of our most important trends at the forefront of science and technology today that are represented in the papers collected in this volume. Here you will find new processes that are producing novel types of nanostructures and nano-materials with unusual and promising properties. Laser processes are described for delicately manipulating living cells or modifying their internal structure with unprecedented degrees of control and precision. Learn about short-pulse lasers that are driving extreme physical processes on record-fast time scales and opening new directions from material processing applications. The conference papers further highlight forefront application areas in pulsed laser deposition, nanoscience, analytical methods, materials, and microprocessing applications. Laser ablation continues to grow and evolve, touching forefront areas in science and driving new technological trends in laser processing applications. Please enjoy the collection of papers in this proceeding. Also, please join us for COLA 2007, to be held in the Canary Islands, Spain (http://www.io.csic.es/cola07/index.php). Conference on Laser Ablation (COLA'05) September 11-16, 2005 Banff, Canada Supported by University of Toronto, Canada (UT) Pacific Northwest National Laboratory (PNNL) Sponsors Sponsorship from the following companies is gratefully acknowledged and appreciated AMBP Tech Corporation GSI Lumonics Amplitude Systèmes IMRA America, Inc. Andor Technologies Journal of Physics D: Applied Physics North Canadian Institute for Photonic Innovations LUMERA LASER GmbH Clark-MXR, Inc. Pascal Coherent, Lamdbda Physik, TuiLaser PVD Products, Inc. Continuum Staib Instruments, Inc. Cyber Laser Inc. Surface GAM LASER, Inc. International Steering Committee C. Afonso (Spain)W. Husinsky (Austria) D. Bäuerle (Austria)W. Kautek (Germany) I.W. Boyd (UK) H. Koinuma (Japan) E.B. Campbell (Sweden) H.U. Krebs (Germany) J.T. Dickinson (USA) D.H. Lowndes (USA) M. Dinescu (Romania) J.G. Lunney (Ireland) J.J. Dubowski (Canada) W. Marine (France) E. Fogarassy (France) K. Murakami (Japan) C. Fotakis (Greece) T. Okada (Japan) D. Geohegan (USA) R.E. Russo (USA) M. Gower (UK) J. Schou (Denmark) R.H. Haglund Jr. (USA) M. Stuke (Germany) R.R. Herman (Canada) K. Sugioka (Japan) W.P. Hess (USA) F. Traeger (Germany) J.S Horwitz (USA) A. Yabe (Japan) Local Organizing Committee Nikki Avery Pacific Northwest National Laboratory Ken Beck Pacific Northwest National Laboratory Jan J. Dubowski University of Alberta Robert Fedosejevs Université de Sherbrooke Alan Joly Pacific Northwest National Laboratory Michel Meunier École Polytechnique de Montréal Suwas Nikumb National Research Council Canada Ying Tsui University of Alberta Conference photograph.

Hess, Wayne P.; Herman, Peter R.; Bäuerle, Dieter; Koinuma, Hideomi

2007-04-01

339

Laser ablation absorption spectroscopy for remote analysis of uranium  

NASA Astrophysics Data System (ADS)

To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm2. The temporal evolution of the ablation plume was investigated in 800 Pa helium environment. It was found that the observation at 3-5 ?s after the ablation at the height of about 2.5 mm are most suited for obtaining higher sensitivity. Using the established conditions, we obtained the limit of detection of the isotope ratio (235U/238U) to be 0.01 %. In addition, the limit of detection of elemental abundance of uranium in uranium glass was also evaluated.

Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Maruyama, Y.; Ohba, H.; Tampo, M.; Wakaida, I.

2013-04-01

340

Optical properties of tin oxide nanoparticles prepared by laser ablation in water: Influence of laser ablation time duration and laser fluence  

SciTech Connect

Colloidal tin oxide nanoparticles are prepared by laser (having a wavelength of 1064 nm) ablation of tin metallic target immersed in pure deionized water. The influences of laser ablation time and laser fluence on the size and optical properties of the synthesized nanoparticles are studied. Prepared tin oxide nanoparticles are characterized by transmission electron microscope, selected area electron diffraction and UV-Visible absorption spectroscopy. The morphology of prepared tin oxide nanoparticles is found to be mostly spherical and with sizes in the nanometric range (mean radius of 3.2 to 7.3 nm). The measured UV-Visible absorption spectra show the presence of absorption peaks in the ultraviolet region. The band gap energy of samples prepared with different laser ablation time duration is calculated and is found to be increased with decrease in size (radius) of the prepared nanoparticles. Photoluminescence emission measurements at room temperature show that all the samples exhibit photoluminescence in the visible region. The peak photoluminescence emission intensity in the sample prepared with 50 min of laser ablation time is 3.5 times larger than that obtained in the sample prepared with 10 min of laser ablation time. - Highlights: Black-Right-Pointing-Pointer SnO{sub 2} nanoparticles (6.4-14.6 nm) are prepared by laser ablation in liquid technique. Black-Right-Pointing-Pointer The influences of laser ablation time and laser fluence are studied. Black-Right-Pointing-Pointer Samples are characterized by TEM and UV-Visible absorption spectroscopy. Black-Right-Pointing-Pointer UV-Visible absorption spectra exhibit quantum confinement effect. Black-Right-Pointing-Pointer Samples exhibit enhanced photoluminescence emissions in the visible region.

Desarkar, Himadri Sankar; Kumbhakar, P., E-mail: nitdgpkumbhakar@yahoo.com; Mitra, A.K.

2012-11-15

341

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

342

Ablation depth in planar Sn targets during the interaction with a Nd:YAG laser for extreme ultraviolet lithography  

E-print Network

Ablation depth in planar Sn targets during the interaction with a Nd:YAG laser for extreme-0417-9642 ABSTRACT The depth of mass ablation in planar Sn targets during the interaction with a pulsed Nd:YAG laser of steady-state laser ablation developed for the laser fusion application, at which laser intensity

Najmabadi, Farrokh

343

Laser-ablation-assisted microparticle acceleration for drug delivery  

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

344

CdTe nanoparticles synthesized by laser ablation  

SciTech Connect

Nanoparticle generation by laser ablation of a solid target in a liquid environment is an easy, fast, and 'green' method for a large scale production of nanomaterials with tailored properties. In this letter we report the synthesis of CdTe nanoparticles by femtosecond laser [387 nm, 180 fs, 1 kHz, pulse energy=6 {mu}J (fluence=1.7 J/cm{sup 2})] ablation of the target material. Nanoparticles with diameters from {approx}2 up to {approx}25 nm were observed to be formed in the colloidal solution. Their size distribution follows the log-normal function with a statistical median diameter of {approx_equal}7.1 nm. Their crystal structure is the same as that of the bulk material (cubic zincblende) and they are slightly Cd-rich (Cd:Te percentage ratio {approx}1:0.9). Photoluminescence emission from the produced nanoparticles was detected in the deep red ({approx}652 nm)

Semaltianos, N. G.; Logothetidis, S. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki GR-54124 (Greece); Perrie, W.; Romani, S.; Potter, R. J.; Dearden, G.; Watkins, K. G. [Department of Engineering, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom); Sharp, M. [General Engineering Research Institute, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF (United Kingdom)

2009-07-20

345

Ablation and nanostructuring of metals by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ~109 s-1.

Ashitkov, S. I.; Komarov, P. S.; Ovchinnikov, A. V.; Struleva, E. V.; Zhakhovskii, V. V.; Inogamov, N. A.; Agranat, M. B.

2014-06-01

346

Hydrodynamic simulation of ultrashort pulse laser ablation of gold film  

NASA Astrophysics Data System (ADS)

The electron collision frequency in a hydrodynamic model was improved to match the laser energy absorbed with experimental data. The model calculation was used to investigate the ablation depth and the dependence of the threshold fluence of gold film on pulse width and wavelength. Two methods for estimating the ablation depth are introduced here with their respective scope of application. The dependence of the threshold fluence of gold film on the pulse width of the laser with a 1053 nm center wavelength agreed well with the experimental data. It was also observed that for pulses shorter than ~200 ps, the threshold fluence showed linear dependence on the logarithm of pulse width and increased with the wavelength, which was different from previous results.

Yu, Dong; Jiang, Lan; Wang, Feng; Shi, Xuesong; Qu, Liangti; Lu, Yongfeng

2015-03-01

347

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

348

The role of valence-band excitation in laser ablation of KCl  

NASA Technical Reports Server (NTRS)

We present recent measurements of excited-atom and ion emission from KCl surfaces illuminated by vacuum-ultraviolet synchrotron radiation (h-nu = 8-28 eV) and ultraviolet laser light (h-nu = 4 eV). At low intensities characteristic of the synchrotron experiments, excited atoms are desorbed by simple valence-band excitation process involving the metallization of the KCl surface. At the higher intensities typical of laser desorption and ablation, we observe a strong decrease in K emission as a function of the number of laser shots, but an essentially constant yield of Cl. K(+) and Cl(-) emission at high intensities show similar behavior. The energetics of these desorption phenomena can be treated in a bond-orbital model which shows that creation of a single valence hole is sufficient to excite an ion to an anti-bonding state.

Haglund, Richard F., Jr.; Tang, Kai; Bunton, Patrick H.; Wang, Ling-Jun

1991-01-01

349

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

350

Nanosecond Infrared Laser for Tissue Ablation  

Microsoft Academic Search

The Mark-III Free-Electron Laser (FEL), operating at the 6.45mum wavelength, has been used successfully in human surgery. Due to the FEL's size and cost, there has been interest in the development of a compact, inexpensive infrared laser for human surgical applications. We have investigated the role of the FEL superpulse, leading to the prediction that nanosecond pulses can satisfy the

G. S. Edwards; R. D. Pearlstein; M. L. Copeland; M. S. Hutson; K. Latone; A. Spiro; G. Pasmanik

2007-01-01

351

Morphology and oxidation of Zr-based amorphous alloy ablated by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Femtosecond laser ablation of an amorphous alloy in air, including single-pulse ablation, multi-pulse drilling and trenching has been investigated. Laser-induced ablation and related effects were examined by means of scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy and electron diffraction. Oxidation was observed in the multi-pulse ablation region surface. With selected parameters, molten trace, spatter and crystallization can be avoided in the vicinity of the machining area. The results show that femtosecond laser ablation with selected parameters is a promising method for micromachining amorphous alloys.

Wang, Xinlin; Lu, Peixiang; Dai, Nengli; Li, Yuhua; Liao, Changrui; Chang, Yanxiao; Yang, Guang; Zheng, Qiguang

2007-11-01

352

Reassembling Solid Materials by Femtosecond Laser Ablation: Case of Aluminum Nitride  

NASA Astrophysics Data System (ADS)

Through atomization and ionization, we could completely alter the composition of a nonconductive material, aluminum nitride, by femtosecond laser ablation. Preferential production of pure aluminum cluster cations Aln+ (n?32) reflects not only their higher energetic stability compared with mixed clusters AlnNm+ but also completion of thermal relaxation in ablation plasma. Observation of metastable dissociation of Aln+ indicates that cluster cations have still enough internal energy for dissociation to occur, although the process is much slower than the cluster formation. Almost no cluster formation has been observed after nanosecond laser ablation of aluminum nitride, which highlights the distinct nature of ablation plasma produced by femtosecond laser ablation.

Kobayashi, Tohru; Matsuo, Yukari

2013-06-01

353

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

354

Plasma ablation characterization by a laser beam deflection technique  

NASA Astrophysics Data System (ADS)

Laser probe beam and multiple-pass deflection techniques were used for real time monitoring of plumes of ablation materials in the mTorr pressure regime by chock wave characterization. Intensity and transit time of shock fronts were studied as functions of focal lens position, energy and pressure. The velocity of the shock wave was determined to be up to 30 km s-1 for a pressure of 40 mTorr.

Villagran-Muniz, Mayo; Sobral, H.; Sanchez Ake, C.; Escobar, L.; Camps, E.

2001-08-01

355

Ultrashort laser ablation of PMMA and intraocular lenses  

Microsoft Academic Search

The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials,\\u000a techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive\\u000a aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular

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

2008-01-01

356

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

357

Laser ablation of human atherosclerotic plaque without adjacent tissue injury  

NASA Technical Reports Server (NTRS)

Seventy samples of human cadaver atherosclerotic aorta were irradiated in vitro using a 308 nm xenon chloride excimer laser. Energy per pulse, pulse duration and frequency were varied. For comparison, 60 segments were also irradiated with an argon ion and an Nd:YAG laser operated in the continuous mode. Tissue was fixed in formalin, sectioned and examined microscopically. The Nd:YAG and argon ion-irradiated tissue exhibited a central crater with irregular edges and concentric zones of thermal and blast injury. In contrast, the excimer laser-irradiated tissue had narrow deep incisions with minimal or no thermal injury. These preliminary experiments indicate that the excimer laser vaporizes tissue in a manner different from that of the continuous wave Nd:YAG or argon ion laser. The sharp incision margins and minimal damage to adjacent normal tissue suggest that the excimer laser is more desirable for general surgical and intravascular uses than are the conventionally used medical lasers.

Grundfest, W. S.; Litvack, F.; Forrester, J. S.; Goldenberg, T.; Swan, H. J. C.

1985-01-01

358

Interferometric diagnostic suite for ultrafast laser ablation of metals  

NASA Astrophysics Data System (ADS)

We report on the development of a suite of novel techniques to measure important characteristics in intense ultrashort laser solid target experiments such as critical surface displacement, ablation depth, and plasma characteristics. Measurement of these important characteristics on an ultrafast (~50 fs) time scale is important in understanding the primary event mechanisms in laser ablation of metal targets. Unlike traditional methods that infer these characteristics from spectral power shifts, phase shifts in frequency domain interferometry (FDI) or laser breakthrough studies of multiple shots on bulk materials, these techniques directly measure these characteristics from a single ultrafast heating pulse. These techniques are based on absolute displacement interferometry and nanotopographic applications of wavefront sensors. By applying all these femtosecond time-resolved techniques to a range of materials (Al, Au, and Au on plastic) over a range of pulse energies (1011 to 1016 W/cm2) and pulse durations (50 to 700 fs), greater insight into the ablation mechanism and its pulse parameter dependencies can be determined. Comparison of these results with hydrocode software programs also reveals the applicability of hydrocode models.

Clarke, Steven A.; Rodriguez, George; Taylor, Antoinette J.; Forsman, Andrew

2004-09-01

359

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

SciTech Connect

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

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

2010-10-08

360

ENERGY DEPOSITION AND NON-THERMAL ABLATION IN FEMTOSECOND LASER GROOVING OF SILICON  

Microsoft Academic Search

Ultra-short pulsed laser ablation of crystalline silicon is characterized by a complicated heat diffusion and material removal process. In this research, a computational investigation is undertaken to understand the temperature distribution and heat effect in femtosecond laser grooving of silicon. Energy accumulation and threshold fluence of silicon ablation by femtosecond lasers are estimated through solving coupled energy balance equations. Thermal

D. P. Wan; Jun Wang; Philip Mathew

2011-01-01

361

Microstructural evolution in laser-ablation-deposited Fe25 at.% Ge thin film  

E-print Network

Microstructural evolution in laser-ablation-deposited Fe­25 at.% Ge thin film Krishanu Biswasa in the solidifying droplets. I. INTRODUCTION The formation of coatings and thin films using pulsed laser ablation; accepted 3 October 2005) Films with Fe­25 at.% Ge composition are deposited by the process of laser

Srivastava, Kumar Vaibhav

362

Characteristics of focused soft X-ray free-electron laser beam determined by ablation  

E-print Network

Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic. Dyer, "Excimer laser polymer ablation: twenty years on," Appl. Phys. A77, 167-173 (2003) and references of coherent radiation, FLASH (Free-electron LASer in Hamburg) provides ultra-intense femtosecond radiation

von der Linde, D.

363

Generation of nanoparticles by laser ablation: Combined MD-DSMC computational study  

E-print Network

Generation of nanoparticles by laser ablation: Combined MD- DSMC computational study Tatiana E.1088/1742-6596/59/1/010 Eighth International Conference on Laser Ablation 44© 2007 IOP Publishing Ltd #12;condensation models. Itina1 and Leonid V. Zhigilei2 1 Laboratory of Lasers, Plasmas and Photonic Processing (LP3, UMR 6182

Zhigilei, Leonid V.

364

Laser ablation for analytical sampling: what can we learn from modeling?  

Microsoft Academic Search

The paper is built up in two parts. First, a rather comprehensive introduction is given, with a brief overview of the different application fields of laser ablation, focusing mainly on the analytical applications, and an overview of the different modeling approaches available for laser ablation. Further, a discussion is presented here about the laser evaporated plume expansion in vacuum or

Annemie Bogaerts; Zhaoyang Chen; Renaat Gijbels; Akos Vertes

2003-01-01

365

Invited Paper 505 In High-Power Laser Ablation V, Claude R. Phipps, Editor  

E-print Network

Invited Paper 505 In High-Power Laser Ablation V, Claude R. Phipps, Editor Proceedings of SPIE, Vol and disintegration of material in laser ablation. Recent progress in the development of new optical and x. 5448 (2004) Computer modeling of laser melting and spallation of metal targets Leonid V. Zhigilei

Zhigilei, Leonid V.

366

1714 OPTICS LETTERS / Vol. 24, No. 23 / December 1, 1999 Focusing of a tabletop soft-x-ray laser beam and laser ablation  

E-print Network

beam and laser ablation B. R. Benware, A. Ozols,* and J. J. Rocca Department of Electrical and Computer the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray distribution near the exit of the amplifier was verified to also be annular; the unfocused laser beam ablated

Rocca, Jorge J.

367

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

368

Dynamics of laser ablation for thin film growth by pulsed laser deposition  

SciTech Connect

Fundamental gas dynamic and laser-material interactions during pulsed laser deposition are explored through sensitive imaging and plasma spectroscopic diagnostics. Two recent phenomena, plume-splitting in background gases and the unusual dynamics of graphite ablation for amorphous diamond film growth, are presented.

Geohegan, D.B.; Puretzky, A.A.

1996-02-01

369

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

370

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

2011-04-19

371

Femtosecond laser bone ablation with a high repetition rate fiber laser source.  

PubMed

Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process. PMID:25657872

Mortensen, Luke J; Alt, Clemens; Turcotte, Raphaël; Masek, Marissa; Liu, Tzu-Ming; Côté, Daniel C; Xu, Chris; Intini, Giuseppe; Lin, Charles P

2015-01-01

372

Corneal ablation using the pulse stretched free electron laser  

NASA Astrophysics Data System (ADS)

The Mark-III Free Electron Laser (FEL), tuned to ?=6.45 ?m has been demonstrated to provide for efficient ablation in ocular and neural tissues with minimal collateral damage. To date, the role of the FEL pulse structure on the mechanism of ablation has not been determined. In an effort to study the role of the FEL micropulse on the ablation of corneal tissue, the native pulse structure of the FEL, a 2.85 gigahertz repetition of picosecond pulses within a five microsecond macropulse envelope, was changed using a a pulse stretcher. This device changes the duration of the micropulse from 1 picosecond to 30-200 picoseconds in length, thus reducing the peak intensity of the micropulse by as much as 200x the original intensity, while the macropulse energy remains unchanged. Two basic metrics were studied: the ablation threshold on water and the ablation crater depth on gelatin. These metrics were employed at ?=6.45 and 6.1 ?m for 1, 100, and 200 picoseconds in micropulse duration. The results showed a very slight difference between the 1, 100, and 200 picosecond micropulse duration, given a 200 fold decrease in peak energy for both the threshold and crater depth measurements. Brightfield imaging was also performed to probe the ablation dynamics and showed no difference between the 1 and 200 ps micropulses. The effect of changing the micropulse duration was studied on the ablation of canine cornea. Craters (500 micron diameter) were created with 25 pulses at three times the ablation threshold as determined for water on freshly enucleated corneas within 12 hours of removal. Three rows of seven craters were created on the center of each cornea. The native one picosecond micropulse and 200 picosecond stretched micropulse were compared at ?=6.1 and 6.45 ?m. Histological data shows that less thermal damage is present at 6.1 ?m compared with 6.45 ?m however, there is no significant difference between the native and stretched pulses with respect to thermal damage.

Mackanos, Mark A.; Joos, Karen M.; Kozub, John A.; Jansen, E. D.

2005-04-01

373

Nanoparticle generation and transport resulting from femtosecond laser ablation of ultrathin metal films: Time-resolved measurements and molecular dynamics  

E-print Network

Nanoparticle generation and transport resulting from femtosecond laser ablation of ultrathin metal thermo-elastic laser ablation mechanism on the generation of nanoparticles from thin gold films Appl.1063/1.3223331 Nanoparticles as potential risk during femtosecond laser ablation J. Laser Appl. 19, 65 (2007); 10

Geohegan, David B.

374

Direct femtosecond laser ablation of copper with an optical vortex beam K. K. Anoop,1,2  

E-print Network

Direct femtosecond laser ablation of copper with an optical vortex beam K. K. Anoop,1,2 R September 2014) Laser surface structuring of copper is induced by laser ablation with a femtosecond optical by nanoparticles produced during laser ablation. At large number of pulses (200

Marrucci, Lorenzo

375

Femtosecond laser plasma plume characteristics in the nanojoule ablation regime  

SciTech Connect

Laser ablation of chromium with nanojoule energy UV femtosecond pulses under background pressure conditions between 0.3 Torr and 700 Torr is studied and the corresponding plasma plume images at different times after irradiation are measured. The ablation focal spot is less than or the order of a micron when 170 nJ of laser pulse energy is used. This low pulse energy leads to short lifetimes of the plasma of the order of tens of nanoseconds. The plume shape changes with ambient pressure due to the collision with background gas. An axially stretched plume changes to a more circular plume as the pressure increases. In addition, a separation of the ionic and atomic components is observed at lower pressure. These two components move at significantly different velocities as well. The plasma plume expands at almost constant velocity at very low pressure but exhibits significant deceleration at higher pressure reaching an asymptotic stopping distance. Plume images are also obtained near the ablation threshold pulse energy. The plume characteristics are compared to different models of plume expansion.

Banerjee, S. P.; Chen, Zhijiang; Fedosejevs, R. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G2V4 (Canada)] [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G2V4 (Canada)

2013-05-14

376

A study of particle generation during laser ablation withapplications  

SciTech Connect

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

Liu, Chunyi

2005-08-12

377

On the efficiency of laser ablation of photopolymerizing compositions in liquid and solidified states  

NASA Astrophysics Data System (ADS)

The efficiency of laser ablation of photocuring compositions that are working substances of various laser-plasma facilities is investigated for the first time. A substantial difference in spectral-energetic laser ablation thresholds, specific mass consumption, momentum coupling coefficient, and conversion efficiency of the laser energy to the kinetic energy of gas-plasma flow for liquid and solidified phases is demonstrated. Application of this class of working media allows not only solving problems related to laser ablation of a target, transport, fine dosing, and obtaining long lifetime and reliability of laser-plasma-based technological setups, but also considerably broadens the range of their operational characteristics.

Loktionov, E. Yu.; Protasov, Yu. S.; Protasov, Yu. Yu.; Telekh, V. D.

2015-02-01

378

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

379

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

380

IR laser ablation of doped poly(methyl methacrylate)  

NASA Astrophysics Data System (ADS)

We investigate the TEA CO 2 laser ablation of films of poly(methyl methacrylate), PMMA, with average MW 2.5, 120 and 996 kDa doped with photosensitive compounds iodo-naphthalene (NapI) and iodo-phenanthrene (PhenI) by examining the induced morphological and physicochemical modifications. The films casted on CaF 2 substrates were irradiated with a pulsed CO 2 laser (10P(20) line at 10.59 ?m) in resonance with vibrational modes of PMMA and of the dopants at fluences up to 6 J/cm 2. Laser induced fluorescence probing of photoproducts in a pump and probe configuration is carried out at 266 nm. Formation of naphthalene (NapH) and phenanthrene (PhenH) is observed in NapI and PhenI doped PMMA, respectively, with relatively higher yields in high MW polymer, in similarity with results obtained previously upon irradiation in the UV at 248 nm. Above threshold, formation of photoproducts is nearly complete after 200 ms. As established via optical microscopy, bubbles are formed in the irradiated areas with sizes that depend on polymer MW and filaments are observed to be ejected out of the irradiated volume in the samples made with high MW polymer. The implications of these results for the mechanisms of polymer IR laser ablation are discussed and compared with UV range studies.

Gaspard, S.; Oujja, M.; Rebollar, E.; Walczak, M.; Díaz, L.; Santos, M.; Castillejo, M.

2007-05-01

381

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

SciTech Connect

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

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

2011-05-09

382

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

383

Testing of concrete by laser ablation  

SciTech Connect

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

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

1997-01-01

384

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

385

Customized ablation using an all-solid-state deep-UV laser  

NASA Astrophysics Data System (ADS)

We show first deep UV ablation results achieved with our new all solid state laser system. The system parameters allow high repetition rate ablation with a small spot diameter of about 0.250mm and a fluence of 350 mJ/cm2 at a wavelength of 210 nm using sequential frequency conversion of a diode pumped laser source. The single shot and multishot ablation rates as well as the ablation profiles have been defined using MicroProf (Fries Research and Technology GmbH, Germany). By means of computer controlled scanning we produce smooth ablation profiles corresponding to a correction of myopia, hyperopia or astigmatism. Due to the small spot size and high repetition rate of the laser we are able to generate in short time intervals complicated ablation profiles described by higher order polynomial functions which are required for the needs of customized corneal ablation.

Korn, G.; Lenzner, M.; Kittelmann, O.; Zatonski, R.; Kirsch, M.; Kuklin, Y.

2003-07-01

386

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

SciTech Connect

Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom density (n{sub n} of order 10{sup 18} cm{sup -3}) and weakly ionized (n{sub e}/n{sub n}, < 0.001) at long time delays of order 200 ns. Recollections of Al plumes confirm the low plume divergence and demonstrate high material adhesion to the receiving substrate, as well as a higher Al material yield than that of conventional pulsed laser deposition. Al redepositions are also highly conductive at the deposit/substrate interface, suggesting possible applications in selective laser-assisted bonding.

BULLOCK, A B

1999-05-26

387

Preparation of polyynes by laser ablation of graphite in aqueous media  

NASA Astrophysics Data System (ADS)

Polyynes were prepared by liquid-phase laser ablation of a graphite target at 1064 nm and identified by analyzing UV absorption spectra in deionized water and various aqueous solutions. We observed that major UV absorption peaks coincide with the electronic transitions corresponding to linear hydrogen-capped polyynes (C nH 2: n = 6, 8, 10). The peak intensities increased when polyynes were produced by irradiating the target immersed in acidic media, while those were relatively weak in basic media. This leads us to conclude that OH - or H + ions play a certain role in the formation of polyynes.

Shin, Seung Keun; Song, Jae Kyu; Park, Seung Min

2011-04-01

388

Tellurite glass thin films on silica and polymer using UV (193 nm) pulsed laser ablation  

NASA Astrophysics Data System (ADS)

Erbium-doped tellurite glass thin films were deposited using excimer (193 nm) laser ablation onto two different types of substrates: silica and polymer-coated silica for engineering optical integrated active-passive devices. The deposition conditions were optimized for both substrates in order to produce high-quality rare-earth (Er3+) ion-doped glass thin films with low propagation loss. The optical and spectroscopic properties of the deposited films, namely transmittance, fluorescence, lifetime as well as refractive indices at 633 nm were measured and analysed in detail.

Zhao, Zhanxiang; Jose, Gin; Steenson, Paul; Bamiedakis, Nikos; Penty, Richard V.; White, Ian H.; Jha, Animesh

2011-03-01

389

Characterization of the plasma plume and of thin film epitaxially produced during laser ablation of SnSe  

NASA Astrophysics Data System (ADS)

Laser-induced ablation was applied to thin film deposition from a tin selenide target. Diagnostic methods are applied to the characterization of the laser ablated plume. Emission from atomic and ionic excited states of tin and selenium dominates the total emission of the plasma plume with excitation temperatures up to 12 000 K. A high-speed ICCD camera has also been used to study three-dimensional plume propagation. Positive and negative cluster ions of bare tin, selenium and of the combined elements have been detected by laser mass-spectrometry of the plume. The growth of SnSe has been analysed by electrical and optical techniques. The effect of laser fluence on the plume and on the properties of the deposits has also been studied. The epitaxial growth of SnSe on several substrates is reported.

Teghil, R.; Santagata, A.; Marotta, V.; Orlando, S.; Pizzella, G.; Giardini-Guidoni, A.; Mele, A.

1995-12-01

390

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry  

SciTech Connect

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime of Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.

Wicklein, S.; Koehl, A.; Dittmann, R. [Peter Gruenberg Institut and JARA-FIT, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Sambri, A.; Amoruso, S.; Wang, X.; Bruzzese, R. [CNR-SPIN and Dipartimento di Scienze Fisiche, Complesso Universitario di Monte Sant'Angelo, Via Cintia, I-80125 Napoli (Italy)

2012-09-24

391

Characterization of the ablation of TeO2 crystals in air with femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Femtosecond (fs) laser pulse ablation (pulse duration of 150 fs, wavelength of 775 nm, repetition rate of 1 kHz) of single-crystalline TeO2 surfaces was performed in air using the direct focusing technique. The lateral and vertical dimensions of laser ablated craters as well as the laser damage thresholds were evaluated for different pulse numbers applied to the same spot. The joint observation using optical microscopy, atomic force microscopy and scanning electron microscopy revealed the surface morphology of the ablated craters and also showed that the ablation threshold depends significantly on the number of laser pulses applied to the same spot due to incubation effects. The incubation effects change the absorption processes involved in fs-laser ablation of the transparent material from multiphoton absorption to a single-photon absorption. These results are discussed on the basis of recent models of the interaction of fs-laser pulses with dielectrics.

Beke, S.; Sugioka, K.; Midorikawa, K.; Péter, Á.; Nánai, L.; Bonse, J.

2010-01-01

392

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

393

Laser ablation of CFRP using picosecond laser pulses at different wavelengths from UV to IR  

NASA Astrophysics Data System (ADS)

Laser processing of carbon fibre reinforced plastics (CFRP) has a great industrial relevance for high performance structural parts in airplanes, machine tools and cars. Through-holes drilled by nanosecond laser pulses show thermal induced molten layers and voids. Recently, picosecond lasers have demonstrated the ability to drill high-efficient and high-quality rivet through-holes. In this paper a high-power picosecond laser system operating at different wavelengths (355 nm, 532 nm and 1064 nm) has been used for CFRP ablation experiments to study the influence of different laser parameters in terms of machining quality and processing time.

Wolynski, Alexander; Herrmann, Thomas; Mucha, Patrick; Haloui, Hatim; L'huillier, Johannes

394

Pulsed laser ablation growth and doping of epitaxial compound semiconductor films  

SciTech Connect

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

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

1995-12-01

395

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

DOEpatents

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

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

2000-01-01

396

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

SciTech Connect

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

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

2009-09-15

397

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration  

Microsoft Academic Search

PurposeTo study the optical changes induced by the microkeratome cut, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ keratomileusis (LASIK) eyes.

Jason Porter; Scott MacRae; Geunyoung Yoon; Cynthia Roberts; Ian G Cox; David R Williams

2003-01-01

398

The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: ablation metrics  

Microsoft Academic Search

Pulsed mid-infrared (6.45 µm) radiation has been shown to cut soft tissue with minimal collateral damage (<40 µm) however, the mechanism of ablation has not been elucidated to date. The goal of this research was to examine the role of the unique pulse structure of the Vanderbilt Mark-III free-electron laser (FEL) and its role in the efficient ablation of soft

Mark A. Mackanos; John A. Kozub; E. Duco Jansen

2005-01-01

399

The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: ablation metrics  

Microsoft Academic Search

Pulsed mid-infrared (6.45 m) radiation has been shown to cut soft tissue with minimal collateral damage (<40 m); however, the mechanism of ablation has not been elucidated to date. The goal of this research was to examine the role of the unique pulse structure of the Vanderbilt Mark-III free-electron laser (FEL) and its role in the efficient ablation of soft

Mark A Mackanos; John A Kozub; E Duco Jansen

2005-01-01

400

Efficiency and Plume Dynamics for Mid-IR Laser Ablation of Cornea  

Microsoft Academic Search

This paper reports ablation experiments on porcine corneal tissue using the Vanderbilt Mark III Free Electron Laser (FEL) and a tabletop Raman-shifted Alexandrite laser. These experiments were designed to test previous models that suggested wavelength and intensity dependent ablation mechanisms. In one test, we compare ablation efficiency and plume dynamics for two FEL wavelengths (lambda=2.77, 6.45 mum) chosen such that

Aroshan Jayasinghe; Borislav Ivanov; M. Shane Hutson

2009-01-01

401

XUV-laser induced ablation of PMMA with nano-, pico-, and femtosecond pulses  

Microsoft Academic Search

For conventional wavelength (UV–vis–IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, etch (ablation) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various very short-wavelength (?<100nm) lasers, emitting pulses with durations ranging from ?10fs to ?1ns, have recently been placed into routine operation. This has facilitated

L. Juha; M. Bittner; D. Chvostova; V. Letal; J. Krasa; Z. Otcenasek; M. Kozlova; J. Polan; A. R. Präg; B. Rus; M. Stupka; J. Krzywinski; A. Andrejczuk; J. B. Pelka; R. Sobierajski; L. Ryc; J. Feldhaus; F. P. Boody; M. E. Grisham; G. O. Vaschenko; C. S. Menoni; J. J. Rocca

2005-01-01

402

Growth modes of ZnO nanostructures from laser ablation  

SciTech Connect

ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

Amarilio-Burshtein, I. [Faculty of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Tamir, S. [Institute of Metals, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Lifshitz, Y. [Faculty of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

2010-03-08

403

Production of warm aluminum cluster anions by femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We report on the production of warm aluminum cluster anions, Al{/n -} (1 ? n ? 26), after femtosecond laser ablation of an aluminum nitride substrate. Large cluster anions of n ? 8 suffer metastable dissociation after their production, which indicates the internal energy of the cluster anions is high enough for the dissociation of an Al atom. We find that the efficiency of metastable dissociation is dependent on the size of cluster anions and the dependence can be rationalized by the dissociation energy of an Al atom from the cluster anions calculated with thermochemical data of the clusters.

Kobayashi, T.; Matsuo, Y.

2015-02-01

404

Towards redistribution laser cooling of molecular gases: Production of candidate molecules SrH by laser ablation  

E-print Network

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

Simon, Philipp; Weller, Lars; Sass, Anne; Weitz, Martin; 10.1117/12.2002379

2013-01-01

405

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 W& uuml Institute of Mineralogy

406

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

407

Modeling of nanosecond-laser ablation: calculations based on a nonstationary averaging technique (spatial moments)  

Microsoft Academic Search

Semi-analytical approach to a quantitative analysis of thermal ns laser ablation is presented. It permits one to take into account: (1) Arbitrary temperature dependences of material parameters, such as the specific heat, thermal conductivity, absorptivity, absorption coefficient, etc. (2) Arbitrary temporal profiles of the laser pulse. (3) Strong (Arrhenius- type) dependence of the ablation velocity on the temperature of the

N. D. Arnold; Boris S. Luk'yanchuk; Nikita M. Bityurin; D. Baeuerle

1998-01-01

408

Microfluidic cell counter with embedded optical fibers fabricated by femtosecond laser ablation  

E-print Network

Microfluidic cell counter with embedded optical fibers fabricated by femtosecond laser ablation using femtosecond laser ablation and anodic bonding. In a first application, we constructed a cell counting device based on small angle light scattering. The counter featured embedded optical fibers

409

Treatment of Vaginal Intraepithelial Neoplasia with Laser Ablation and Upper Vaginectomy  

Microsoft Academic Search

To assess the effectiveness of laser ablation and upper vaginectomy in the treatment of vaginal intraepithelial neoplasia (VAIN), we have reviewed the charts of 52 patients managed with laser ablation (28 patients) and upper colpectomy (24 patients). On the basis of our results, patient selection and operator skill have a significant influence on the outcome. In posthysterectomy patients with VAIN3

Emmanuel Diakomanolis; Alexandros Rodolakis; Zanis Boulgaris; Georgios Blachos; Stylianos Michalas

2002-01-01

410

Characterization of Aerosols Generated by Nanosecond Laser Ablation of an Acrylic Paint  

Microsoft Academic Search

This study focuses on particles produced during laser ablation of a green colored acrylic wall paint, which is frequently used in industrial buildings and in particular in nuclear installations. Ablation is carried out with a Nd:YAG laser at a wavelength of 532 nm and a pulse duration of 5 ns, in a cell at ambient pressure and temperature, which is

Pascale Dewalle; Jacques Vendel; Jean-Marc Weulersse; Philippe Hervé; Guy Decobert

2010-01-01

411

Regression of Barrett's esophagus by laser ablation in an anacid environment  

Microsoft Academic Search

Summary Consistent regression of intestinal metaplasia in Barrett's esophagus has not been achieved with medical or surgical interventions. In this case report, a patient with Barrett's esophagus of stable length had half the circumference of the Barrett's epithelium ablated with laser therapy while on a high-dose proton-pump inhibitor. In the absence of esophageal acid exposure and after laser ablation, the

Richard E. Sampliner; Lee J. Hixson; M. Brian Fennerty; Harinder S. Garewal

1993-01-01

412

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

EPA Science Inventory

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

413

Deposition of polyimide precursor by resonant infrared laser ablation  

NASA Astrophysics Data System (ADS)

We report the successful deposition of a polyimide precursor using resonant infrared laser ablation (RIR-LA). A solution of poly(amic acid) (PAA) dissolved in N-methyl-2-pyrrolidinone (NMP), the melt processable precursor to polyimide, was frozen in liquid nitrogen for use as an ablation target in a high-vacuum chamber. Fourier transform infrared spectroscopy was used to determine that the local chemical structure remained unaltered. Gel permeation chromatography demonstrated that the transferred PAA retained its molecular weight, showing that RIR-LA is able to transfer the polymer intact, with no detectable chain fragmentation. These results are in stark contrast to UV-processing which degrades the polymer. After deposition the PAA may be removed with a suitable solvent; however, once the material has undergone cyclodehydration it forms an impenetrable three-dimensional network associated with thermosetting polymers. The transfer of uncured PAA precursor supports the hypothesis that RIR-LA is intrinsically a low temperature process, because the PAA is transferred without reaching the curing temperature. The RIR-LA also effectively removes the solvent NMP from the PAA, during both the ablation and deposition phases; this is a necessary step in generating PI films.

Dygert, N. L.; Gies, A. P.; Schriver, K. E.; Haglund, R. F., Jr.

2007-11-01

414

Laser ablated copper plasmas in liquid and gas ambient  

SciTech Connect

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (n{sub e}) determined using Stark broadening of the Cu I (3d{sup 10}4d{sup 1} {sup 2}D{sub 3/2}-3d{sup 10}4p{sup 1} {sup 2}P{sub 3/2} at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (T{sub e}) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ?590 nm.

Kumar, Bhupesh; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)] [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)

2013-05-15

415

Ins and outs of endovenous laser ablation: afterthoughts.  

PubMed

Physicists and medical doctors "speak" different languages. Endovenous laser ablation (EVLA) is a good example in which technology is essential to guide the doctor to the final result: optimal treatment. However, for the doctor, it is by far insufficient just to turn on the knobs of the laser. He should understand what is going on in the varicose vein. On the other hand, the physicist is usually not aware what problems the doctor finds on his road towards improving a new technique. We have tried to bring both languages together in the special on Ins and outs of endovenous laser ablation published in this issue of Lasers in Medical Science. The 13 articles include endovenous related clinical (de Roos 2014; Kockaert and Nijsten 2014; van den Bos and Proebstle 2014) and socioeconomical articles (Kelleher et al 2014), the first paper on the molecular pathophysiologic mechanisms (Heger et al 2014), fiber tips (Stokbroekx et al 2014), the future of EVLA (Rabe 2014), a review of EVLA with some important issues for debate (Malskat et al 2014), an excellent paper on transcutaneous laser therapies of spider and small varicose veins (Meesters et al 2014), as well as several scientific modeling articles, varying from a mathematical model of EVLA that includes the carbonized blood layer on the fiber tip (van Ruijven et al 2014) and its application to the simulation of clinical conditions (Poluektova et al 2014) via experimental measurements of temperature profiles in response to EVLA, radiofrequency waves, and steam injections (Malskat et al 2014) to a literature review and novel physics approach of the absorption and particularly scattering properties of whole blood also including the infrared wavelengths used by EVLA (Bosschaart et al 2014). The aim of our afterthoughts, the 14th article in this special, is to try to amalgamate the clinical and physical contents of these contributions, providing the reader with the bridge that overlaps these different backgrounds. PMID:24399461

Neumann, H A Martino; van Gemert, Martin J C

2014-03-01

416

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

417

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response  

SciTech Connect

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon [Manufacturing Processes Department, Fundacion TEKNIKER, Av. Otaola 20, 20600, Eibar, Guipuzcoa (Spain); Lejardi, Ainhoa; Sarasua, Jose-Ramon [Department of Mining and Metallurgy Engineering and Materials Science, School of Engineering, University of the Basque Country (EHU-UPV), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

2011-11-01

418

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

419

Laser lift-off initiated by direct induced ablation of different metal thin films with ultra-short laser pulses  

Microsoft Academic Search

Molybdenum thin films on glass substrates play an important role as contact layer for thin film solar cells. They can be ablated by picosecond laser pulses irradiated from the substrate side at low laser fluences of less than 1 J cm?2, while structured trenches remain free from thermal damage and residues. The fluence for that so-called direct induced ablation from

Gerhard Heise; Matthias Domke; Jan Konrad; Sebastian Sarrach; Jürgen Sotrop; Heinz P Huber

2012-01-01

420

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

421

Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser  

SciTech Connect

The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm{sup 2}.

Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun, E-mail: wenjunwang@mail.xjtu.edu.cn; Wang, Kedian; Mei, Xuesong [School of Mechanical Engineering, Xi'an Jiaotong University, No. 28, Xianning Westroad, Xi'an 710049 (China) [School of Mechanical Engineering, Xi'an Jiaotong University, No. 28, Xianning Westroad, Xi'an 710049 (China); State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054 (China)

2014-03-15

422

Near-IR imaging of Erbium Laser Ablation with a Water Spray.  

PubMed

Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm(1). Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium lasers versus carbon dioxide laser systems due to the nature of the primary absorber and it is necessary to have water present on the tooth surface for efficient ablation at erbium laser wavelengths. In this study, sound human tooth sections of approximately 2-3-mm thickness were irradiated by free running and Q-switched Er:YAG & Er:YSGG lasers under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with a band-pass filter centered at 1310-nm combined with an InGaAs area camera with a NIR zoom microscope. Obvious differences in the crater evolution were observed between CO(2) and erbium lasers. Ablation stalled after a few laser pulses without a water spray as anticipated. Efficient ablation was re-initiated by resuming the water spray. Micro-fractures were continuously produced apparently driven along prism lines during multi-pulse ablation. These fractures or fissures appeared to merge together as the crater evolved to form the leading edge of the ablation crater. These observations support the proposed thermo-mechanical mechanisms of erbium laser involving the strong mechanical forces generated by selective absorption by water. PMID:21892255

Darling, Cynthia L; Maffei, Marie E; Fried, William A; Fried, Daniel

2008-01-20

423

Near-IR imaging of erbium laser ablation with a water spray  

NASA Astrophysics Data System (ADS)

Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm1. Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium lasers versus carbon dioxide laser systems due to the nature of the primary absorber and it is necessary to have water present on the tooth surface for efficient ablation at erbium laser wavelengths. In this study, sound human tooth sections of approximately 2-3-mm thickness were irradiated by free running and Q-switched Er:YAG & Er:YSGG lasers under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with a band-pass filter centered at 1310-nm combined with an InGaAs area camera with a NIR zoom microscope. Obvious differences in the crater evolution were observed between CO2 and erbium lasers. Ablation stalled after a few laser pulses without a water spray as anticipated. Efficient ablation was re-initiated by resuming the water spray. Micro-fractures were continuously produced apparently driven along prism lines during multi-pulse ablation. These fractures or fissures appeared to merge together as the crater evolved to form the leading edge of the ablation crater. These observations support the proposed thermo-mechanical mechanisms of erbium laser involving the strong mechanical forces generated by selective absorption by water.

Darling, Cynthia L.; Maffei, Marie E.; Fried, William A.; Fried, Daniel

2008-02-01

424

Laser ablation of NaN3 and CsN3 Leonid Belau, Jonathan Gorodetsky, and Yehuda Haas  

E-print Network

Laser ablation of NaN3 and CsN3 Leonid Belau, Jonathan Gorodetsky, and Yehuda Haas Department sodium azide and cesium azide crystals were irradiated by high power laser pulses; the ablation products of Physics. DOI: 10.1063/1.1899564 I. INTRODUCTION Laser ablation of materials has been used to prepare

Haas, Yehuda

425

Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS Wolfgang Muller,*a  

E-print Network

Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS Wolfgang Muller,*a J recrystalli- zation of ice with increasing depth. Using 193 nm excimer laser-ablation ICPMS (UV-LA-ICPMS), we in this study. A custom- built cryo-sample holder is loaded into a standard Laurin two-volume laser-ablation

Royal Holloway, University of London

426

UV-Laser-Ablation-Combustion-GC-IRMS a tool for on-line analysis of intra-annual  

E-print Network

UV-Laser-Ablation-Combustion-GC-IRMS a tool for on-line analysis of intra-annual variation of d13C standards which are also ablated by laser shots and combusted. CO2 Standard gas is needed for mass conventional method (elemental analysis-IRMS) indicated a high level of accuracy of the Laser ablation

427

Evaluation of pneumatic nebulization and ns-laser ablation ICP-MS for bulk elemental analysis and 2-dimensional  

E-print Network

Evaluation of pneumatic nebulization and ns-laser ablation ICP-MS for bulk elemental analysis and 2 nebulization and ns-laser ablation ICP-MS for bulk elemental analysis and 2-dimensional element mapping of iron 20XX DOI: 10.1039/b000000x The capabilities and limitations of nanosecond laser ablation ICP ­ mass

Claeys, Philippe

428

Production efficiency of thin metal flyers formed by laser ablation S. Cogan, E. Shirman, and Y. Haasa  

E-print Network

Production efficiency of thin metal flyers formed by laser ablation S. Cogan, E. Shirman, and Y. INTRODUCTION Research on ablative acceleration of thin foil targets by intense pulsed lasers began in the late of the dependence of the ablation efficiency of thin copper films on the laser-pulse length upon front irradia- tion

Haas, Yehuda

429

IR laser ablative desulfurization of poly(1,4-phenylene sulfide) Sardar M.A. Durani a  

E-print Network

IR laser ablative desulfurization of poly(1,4-phenylene sulfide) Sardar M.A. Durani a , Ehsan E; accepted 13 January 2005 Available online 13 March 2005 Abstract Pulsed infrared laser-induced ablation of polymers is pulsed infrared laser-induced ablation (PLAD) that can take place by exposing a polymer

Masoudi, Husain M.

430

Abstract This paper describes the automated in situ trace element analysis of solid materials by laser ablation (LA)  

E-print Network

by laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS). A compact computer-controlled solid state Nd:YAG Mer- chantekTM EO UV laser ablation (LA) system has been coupled with the high­1 to 455 ng g­1 and less than 100 ng g­1 for most trace elements. Introduction Laser ablation (LA

Chen, Zhongxing

431

PROCESS CHARACTERISATION OF PICOSECOND LASER ABLATION OF SIO2 AND SINX LAYERS ON PLANAR AND TEXTURED SURFACES  

E-print Network

PROCESS CHARACTERISATION OF PICOSECOND LASER ABLATION OF SIO2 AND SINX LAYERS ON PLANAR-through" processes such as screen printing of grid lines on the front side. Laser ablation with ultra short pulses. In the present paper, we investigate picosecond laser ablation of passivating SiO2 and SiNx layers on planar

432

Internal distribution of Li and B in serpentinites from the Feather River Ophiolite, California, based on laser ablation  

E-print Network

, based on laser ablation inductively coupled plasma mass spectrometry Cin-Ty Aeolus Lee, Masaru Oka Occidentale, UMR6538, CNRS, F-29238 Brest CEDEX 3, France [1] Laser ablation inductively coupled plasma mass Ophiolite, California, based on laser ablation inductively coupled plasma mass spectrometry, Geochem

Lee, Cin-Ty Aeolus

433

SF2I.7.pdf CLEO:2014 2014 OSA Emission and expansion features of ns and fs laser ablation  

E-print Network

SF2I.7.pdf CLEO:2014 © 2014 OSA 1 Emission and expansion features of ns and fs laser ablation and hydrodynamic expansion dynamics of ns and fs laser ablated metal plasmas in the presence of an ambient and femtosecond laser ablation (LA) have been demonstrated as a powerful tool for numerous applications. Some

Harilal, S. S.

434

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

SciTech Connect

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

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

2012-06-15

435

Absence of amorphous phase in high power femtosecond laser-ablated silicon  

SciTech Connect

As femtosecond lasers emerge as viable tools for advanced microscale materials processing, it becomes increasingly important to understand the characteristics of materials resulting from femtosecond laser microablation or micromachining. We conducted transmission electron microscopy experiments to investigate crater structures in silicon produced by repetitive high power femtosecond laser ablation. Comparable experiments of nanosecond laser ablation of silicon were also performed. We found that an amorphous silicon layer that is typically produced in nanosecond laser ablation is absent when the material is irradiated by high power femtosecond laser pulses. Instead, only a defective single crystalline layer was observed in the high power femtosecond laser-ablated silicon crater. Possible mechanisms underlying the formation of the defective single crystalline phase are discussed.

Rogers, Matthew S.; Grigoropoulos, Costas P. [Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720 (United States); Minor, Andrew M. [Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, California 94720, USA and National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Mao, Samuel S. [Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720 (United States); Advanced Energy Technologies Department, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2009-01-05

436

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

437

Wall-ablative laser-driven in-tube accelerator  

NASA Astrophysics Data System (ADS)

The laser-driven in-tube accelerator in which the propellant is supplied from laser-ablated gas from the tube wall was developed. Proof-of concept demonstrations of vertical launch were successfully done. The device had a 25mm X 25mm square cross-section; two opposing walls were made of polyacetal and acted as the propellant, the other two acrylic window with guide grooves to the projectile. The upper end of the launch tube was connected to a vacuum chamber of an inner volume of 0.8 m2, in which the initial pressure was set to lower than 20 Pa. With plugging the bottom end of the launch tube, a momentum coupling coefficient exceeding 2.5 mN/W was obtained. Even with the bottom end connected to the same vacuum chamber through a different duct, the projectile was vertical launched successfully, obtaining 0.14 mN/W.

Sasoh, Akihiro; Suzuki, Shingo; Matsuda, Atsushi

2008-05-01

438

Fabrication of crystallized boron films by laser ablation  

NASA Astrophysics Data System (ADS)

Polycrystalline ?-rhombohedral boron films mixed with amorphous boron phase have been successfully fabricated on quartz substrates using pulsed laser ablation in a quartz glass tube chamber placed in an electric furnace. The crystallinity of the films strongly depended on the temperature of the furnace and the pressure of background argon gas. High temperature and high pressure in the chamber were suitable for crystallized boron film preparation. The best crystalline films (without B 2O 3 phase formation) were obtained at 1000°C, 100 Pa. XPS measurements demonstrated that the major contaminants were carbon and oxygen, and the atomic ratio of oxygen to boron was 0.05 under the preparation conditions of well-crystallized films. The surface roughness of the films decreased by lowering laser energy to 150 mJ/pulse under the same pressure and temperature conditions.

Wang, Zhongke; Shimizu, Yoshiki; Sasaki, Takeshi; Kirihara, Kazuhiro; Kawaguchi, Kenji; Kimura, Kaoru; Koshizaki, Naoto

2004-04-01

439

Endometrial ablation using SideFire laser fiber  

NASA Astrophysics Data System (ADS)

The first successful report using the neodymium:yttrium-aluminum-garnet (Nd:YAG) Laser to control hypermenorrhea was reported in 1981. Variations on the treatment technique have been attempted to improve the amenorrhea rate. Reports using the Nd:YAG laser with the blanching or non-touch technique seem to result in a better outcome and higher rate of total amenorrhea than using the dragging technique. Due to the report of improved rates of amenorrhea when using the blanching technique and the Nd:YAG laser, a fiber was developed to direct the laser energy at right angles to the axis of the fiber, therefore allowing a total treatment of the entire uterus in a perpendicular fashion. The theoretic benefit of this would be a more complete and predictable destruction of the endometrial lining, avoiding fluid overload by coagulating and sealing of the vessels and lymphatic. After a follow-up of 12 to 36 months, 56 of the 60 patients (93%) who underwent complete endometrial ablation with the SideFireTM technique had excellent results. Total absolute amenorrhea resulted in 50 patients (83%). Contrary to earlier reports, using the rollerball electrode, this procedure technique resulted in no decrease in results in younger patients. In conclusion, this seems to be a reasonable alternative which offers improved results when compared to previously available methods using electrosurgery or the Nd:YAG laser without the use of the SideFireTM device.

Everett, Royice B.

1996-05-01

440

Picosecond laser ablation of nano-sized WTi thin film  

NASA Astrophysics Data System (ADS)

Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm2 were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma.

Petrovi?, S.; Gakovi?, B.; Peruško, D.; Desai, T.; Batani, D.; ?ekada, M.; Radak, B.; Trtica, M.

2009-08-01

441

Fabrication of polymer waveguides by laser ablation using a 355 nm wavelength Nd:YAG laser  

Microsoft Academic Search

The demand for optical waveguides integrated into Printed Circuit Boards (PCBs) is increasing as the limitations of copper interconnects are being reached. Optical polymer materials offer a good solution due to their relatively low cost and compatibility with traditional PCB manufacturing processes. Laser ablation is one method of manufacture, for which excimer lasers have been used, butUV Nd:YAG (Neodymium-doped Yttrium

Paul P. Conway; David A. Hutt; David R. Selviah; Kai Wang; Jeremy Rygate; Jonathan Calver; Witold Kandulski

2011-01-01

442

Laser ablation of human atherosclerotic plaque without adjacent tissue injury.  

PubMed

Seventy samples of human cadaver atherosclerotic aorta were irradiated in vitro using a 308 nm xenon chloride excimer laser. Energy per pulse, pulse duration and frequency were varied. For comparison, 60 segments were also irradiated with an argon ion and an Nd:YAG (neodymium:yttrium aluminum garnet) laser operated in the continuous mode. Tissue was fixed in formalin, sectioned and examined microscopically. The Nd:YAG and argon ion-irradiated tissue exhibited a central crater with irregular edges and concentric zones of thermal and blast injury. In contrast, the excimer laser-irradiated tissue had narrow deep incisions with minimal or no thermal injury. These preliminary experiments indicate that the excimer laser vaporizes tissue in a manner different from that of the continuous wave Nd:YAG or argon ion laser. The sharp incision margins and minimal damage to adjacent normal tissue suggest that the excimer laser is more desirable for general surgical and intravascular uses than are the conventionally used medical lasers. PMID:3838324

Grundfest, W S; Litvack, F; Forrester, J S; Goldenberg, T; Swan, H J; Morgenstern, L; Fishbein, M; McDermid, I S; Rider, D M; Pacala, T J

1985-04-01

443

Spectroscopic observation of ablation plasma generated with a laser-driven extreme ultraviolet light source  

NASA Astrophysics Data System (ADS)

An extreme ultraviolet (EUV) light source (? = 9-25 nm, 10 Hz) was developed to study EUV ablation physics and applications. The EUV source device including an elliptical total reflection mirror was optimized to provide EUV irradiance as high as 4.2 × 109 W/cm2 on ablation samples. Time-resolved spectroscopic observation of ablation plasma from a Si plate was conducted to derive electron temperature and density, and compared with those for laser-produced ablation at the same irradiance. Difference in ablation mechanism between two sources is discussed.

Masuda, Masaya; Tanaka, Nozomi; Hane, Kazuyoshi; Sunahara, Atsushi; Fujioka, Shinsuke; Nishimura, Hiroaki

2015-02-01

444

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

445

Studies of the plume accompanying pulsed ultraviolet laser ablation of zinc oxide  

NASA Astrophysics Data System (ADS)

The plume of ejected material accompanying pulsed laser ablation of a ZnO target at 193 nm in vacuum has been investigated using wavelength and spatially resolved optical emission spectroscopy and Langmuir probes. All lines in the observed optical emission spectra are assignable to electronically excited Zn+* cations, and Zn* and O* neutrals, all of which emitting species we attribute to the result of electron-ion recombination processes in the gas phase following material ejection, laser-plume interactions, ionization, and thus, plasma formation. Various contributory components can be identified within the plume. Included among these are: a fast distribution of Zn2+ ions (observed via emission from highly excited states of Zn+*) together with an accompanying subset of fast electrons—the relative importance of which increases with increasing incident fluence on the target; a more abundant slower component involving both Zn+ and O+ ions, which expand in association with the main body of the electron distribution; and a slow moving component of Zn* emitters, which we suggest should be associated with material that has been backscattered from the expanding plasma ball towards the target surface and then rebounded or desorbed into the gas phase. The observation that the postablated target surface is substantially enriched in Zn provides additional support for the importance of material backscattering from within the dense plasma ball, accommodation, and in this case, recondensation on the target. The deduction that the target surface in the vicinity of the irradiated area is Zn rich after just a few laser shots provides an explanation for the oft-reported observation that ZnO films deposited by pulsed laser ablation of ZnO in vacuum are nonstoichiometric, with a Zn:O ratio greater than unity. Such backscattering from the plasma volume and selective recondensation of the less volatile component or components within the plume prior to the next ablation pulse being incident on the target surface appear to account for virtually all reported instances of nonstoichiometric film growth by pulsed laser deposition (PLD) in vacuum. Indeed, given the deduced area of the target surface affected by such redeposition and the target translation speeds typically employed in PLD studies, it would appear that nonstoichiometric film growth is likely to be the norm whenever PLD is carried out in vacuum and at wavelengths and fluences that lead to formation of a sufficiently dense plasma to cause material redeposition on the target.

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

2002-12-01

446

Fabrication of Silver Nanoparticles Dispersed in Palm Oil Using Laser Ablation  

PubMed Central

In this study we used a laser ablation technique for preparation of silver nanoparticles. The fabrication process was carried out by ablation of a silver plate immersed in palm oil. A pulsed Nd:YAG laser at a wavelength of 1064 nm was used for ablation of the plate at different times. The palm coconut oil allowed formation of nanoparticles with very small and uniform particle size, which are dispersed very homogeneously within the solution. The obtained particle sizes for 15 and 30 minute ablation times were 2.5 and 2 nm, respectively. Stability study shows that all of the samples remained stable for a reasonable period of time. PMID:21151470

Zamiri, Reza; Zakaria, Azmi; Ahangar, Hossein Abbastabar; Sadrolhosseini, Amir Reza; Mahdi, Mohd Adzir

2010-01-01

447

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

2011-12-01

448

Dynamics of Laser Ablation Plasmas in Vacuum and Background Gases: Effects of Scattering and Interplume Collisions on Velocity Distributions used for PLD Film Growth  

Microsoft Academic Search

Pulsed laser deposition (PLD) uses laser ablation of a solid target to accelerate atoms and ions in a high-density plasma to superthermal kinetic energies (typically 10-100 eV). These high kinetic energies have proven essential for the nonequilibrium formation of thin films of new ultrahard metastable phases, such as the synthesis of amorphous diamond (ta-C, tetrahedrally-coordinated, amorphous carbon) from the laser

David Geohegan

1996-01-01

449

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

2015-03-01

450

Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes  

SciTech Connect

Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

Lopez-Arias, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Unidad Asociada Departamento de Quimica Fisica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid, and Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain); Oujja, M.; Sanz, M.; Castillejo, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T. [Institute of Electronics, Uzbekistan Academy of Sciences, Akademgorodok, 33, Dormon Yoli Street, Tashkent 100125 (Uzbekistan)

2012-02-15

451

The direct measurement of ablation pressure driven by 351-nm laser radiation  

SciTech Connect

The instantaneous scaling of ablation pressure to laser intensity is directly inferred for ramp compression of diamond targets irradiated by 351-nm light. Continuously increasing pressure profiles from 100 to 970 GPa are produced by direct-drive laser ablation at intensities up to 7 x 10{sup 13} W/cm{sup 2}. The free-surface velocity on the rear of the target is used to directly infer the instantaneous ablation-pressure profile at the front of the target. The laser intensity on target is determined by laser power measurements and fully characterized laser spots. The ablation pressure is found to depend on the laser intensity as P(GPa)=42({+-}3)[I(TW/cm{sup 2})]{sup 0.71({+-}0.01)}.

Fratanduono, D. E. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Mechanical Engineering, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Boehly, T. R. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Celliers, P. M.; Eggert, J. H.; Smith, R. F.; Hicks, D. G.; Collins, G. W. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Barrios, M. A. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Physics and Astronomy, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Meyerhofer, D. D. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Mechanical Engineering, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Department of Physics and Astronomy, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States)

2011-10-01

452

Applications of Ion Laser Systems  

NASA Astrophysics Data System (ADS)

This paper provides an introduction to the more common applications of ion laser systems. Applications discussed include photocoagulation, flow cytometry, laser disk mastering, laser doppler velocimetry, Raman spectroscopy, holography, laser light shows, large screen projection, fingerprint detection, and applications in printing such as color separation and scanning. All these applications are currently in widespread use. At the end of the paper a short review is provided of developing applications such as cardiovascular surgery and semiconductor processing.

Fletcher, Peter W.

1987-04-01

453

Effects of Ion Beam Waveform on Flyer Acceleration Produced by Pulsed Ion Beam Ablation Plasma  

NASA Astrophysics Data System (ADS)

The main objective of the current study is to clarify the influence of ion beam waveform and to investigate the momentum producing capability of flyer acceleration for propulsion applications, which is produced by irradiating target materials with pulsed ion beam. Al thin foil with a thickness of 50 ?m was used to form the high-pressure, high-temperature, and high-energy density ablation plasma when it interacts with pulsed ion beam. The analytical procedures are based on one-dimensional hydrodynamic equations together with a real gas equation of state. This paper presents not only the physical parameters of pulsed ion beam interaction with a target, but also shows the effects of ion beam waveform on momentum production. In addition, we describe the mechanism of ablation pressure formation and compare the results obtained for the rectangular and the parabolic waveform of ion beam irradiation. An ion beam with parabolic waveform produces ablation pressure more efficiently than a rectangular waveform. Propulsion performance is also estimated. An impulse bit of 50.7 mNs and a specific impulse of 5200 s are obtained at an electric power consumption of 1677 W.

Buttapeng, Chainarong; Yazawa, Masaru; Harada, Nobuhiro

454

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

455

Below band-gap laser ablation of diamond for transmission electron microscopy  

NASA Technical Reports Server (NTRS)

A 248 nm excimer laser was used to thin naturally occurring type 1a diamond substrates at normal and glancing (22 deg) incidence. Perforation of a 250-micron-thick substrate was achieved in about 15 min at normal incidence. While the substrate thinned at glancing incidence was found to have large electron-transparent areas, that thinned at normal incidence required additional argon-ion milling to achieve electron transparency. X-ray photoelectron spectroscopy of the back surface of the diamond failed to detect any graphite or glassy carbon, confirming that damage due to laser ablation occurs only at the incident surface. Samples prepared using this technique imaged in the transmission electron microscope were observed to have retained the nitrogen platelets characteristic of such type 1a diamonds.

George, T.; Foote, M. C.; Vasquez, R. P.; Fortier, E. P.; Posthill, J. B.

1993-01-01

456

The role of asymmetric excitation in self-organized nanostructure formation upon femtosecond laser ablation  

SciTech Connect

Surface pattering upon multi-pulse femtosecond laser ablation is modeled by a non-linear-dynamic erosion/smoothing model, similar to structure formation during ion sputtering. The model is adopted to account for the influence of laser polarization on nanostructure features. Based on a nonlinear equation of the Kuramoto-Siavshinsky type, it is shown that the directional anisotropy in the pattern formation may result from a spatial anisotropy of the initial excitation/energy-coupling process, such as resonant coupling to surface plasmons/polaritons, or electron diffusion properties. Also, anisotropy of elasto-dynamic surface and diffusion properties may be involved. A comparison of numeric simulations based on the model with corresponding experi-mental results gives a very good agreement.

Reif, Juergen; Varlamova, Olga; Varlamov, Sergej; Bestehorn, Michael [Brandenburgische Technische Universitaet (BTU) Cottbus Platz der Deutschen Einheit 1, 03046 Cottbus (Germany); Brandenburgische Technische Universitaet (BTU) Cottbus Platz der Deutschen Einheit 1, 03046 Cottbus (Germany)

2012-07-30

457

Laser driven compact ion accelerator  

DOEpatents

A laser driven compact ion source including a light source that produces an energy pulse, a light source guide that guides the energy pulse to a target and produces an ion beam. The ion beam is transported to a desired destination.

Tajima, Toshiki

2005-03-15

458

Dynamics of laser ablation of microparticles prior to nanoparticle generation  

SciTech Connect

To better understand the process of nanoparticle formation when microspheres are ablated by a high-energy laser pulse, we investigated the Nd:YAG laser-induced breakdown of 20 {mu}m glass microspheres using time-resolved optical shadow images and Schlieren images. Time-resolved imaging showed the location of the initial breakdown and the shockwave motion over its first 300 {mu}m of expansion. From these measurements, we determined the shockwave velocity dependence on laser fluence. Measured shockwave velocities were in the range of 1{endash}10 km/s. We also developed a numerical model that simulated breakdown in the glass microsphere and the propagation of this disturbance through the edge of the sphere where it could launch an air shock. Our objective was to simulate the shockwave velocity dependence on laser fluence and to generate glass density, temperature, and mass velocity profiles after breakdown. The simulation and experimental data compared favorably. {copyright} 2001 American Institute of Physics.

Lee, Jaemyoung; Becker, Michael F.; Keto, John W.

2001-06-15

459

Bone Ablation at 2.94 mm Using the Free-Electron Laser and Er:YAG Laser  

NASA Astrophysics Data System (ADS)

Bone Ablation at 2.94 microns Using the Free-Electron Laser and Er:YAG Laser in Perfluorocarbon Compounds B. Ivanov^1, A. M. Hakimian^1, G. M. Peavy^2, R. F. Haglund, Jr.1 1Department of Physics and Astronomy, W. M. Keck Foundation Free-Electron Laser Center, Vanderbilt University, Nashville, TN 37235 2Beckman Laser Institute and Medical Clinic, College of Medicine, University of California, Irvine, CA 92612 We report studies on the efficiency of mid-IR laser ablation of cow cortical bone using the Vanderbilt free-electron laser (FEL), when irrigating the ablation zone with an inert and biocompatible perfluorocarbon compounds (PFC). At 2.94 microns, the bone matrix (mainly by water) absorbs the radiation while the PFCs transmit this wavelength, dissipate heat and acoustical stress, and prevent carbonization of the bone sample. The ablation rate, as a function of laser fluence, scanning speed and the type of PFC, was investigated. The laser fluence was estimated to be 5 J/cm^2 - 100 J/cm^2 with a laser focal spot diameter of 160 microns 500 microns and a scanning speed of 40 microns/s 2960 microns/s. The ablation rate was estimated from scanning electron microscopy to be 0.5 mm/s 2.4 mm/s