Note: This page contains sample records for the topic laser ablation spectroscopy from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

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

2

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

PubMed

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

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

2013-08-10

3

Influence of sample surface condition on chemical analysis using laser ablation inductively coupled plasma atomic emission spectroscopy  

Microsoft Academic Search

The influence of sample surface condition on chemical analysis was investigated when using laser ablation sampling with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The ablated mass quantity and composition were found to be significantly different from original vs. pre-ablated surfaces. The ablated mass quantity from original surfaces was much greater than that from pre-ablated surfaces, and the ablation rate

Xianglei Mao; Richard E. Russo; Wing-Tat Chan

1997-01-01

4

Laser ablation mass removal versus incident power density during solid sampling for inductively coupled plasma atomic emission spectroscopy  

Microsoft Academic Search

For laser ablation solid sampling, the quantity of material ablated (removed) influences the sensitivity of chemical analysis. The mass removal rate depends strongly on the laser power density, which is the main controllable parameter for a given material and wavelength parameter using laser solid sampling for inductively coupled plasma atomic emission spectroscopy (ICP-AES). For a wide variety of materials, a

Mark A. Shannon; Xianglei L. Mao; Alberto. Fernandez; Wing-Tat. Chan; Richard E. Russo

1995-01-01

5

In situ characterisation of hydrocarbon layers in TEXTOR by laser induced ablation and laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Laser based methods in combination with spectroscopy are proposed for in situ characterisation of the first wall in ITER and are tested presently and applied in TEXTOR. A ruby laser is used to heat up a defined area at a surface of a test limiter, which then leads to ablation. The released particles are observed spectroscopically either at the surface or in the edge of the tokamak plasma.The absolute calibration affords the knowledge of the ablation process, especially the ablated debris compounds as a function of laser energy. Beyond that, the interaction of the released material with the edge plasma and the atomic and spectroscopic data of the species must be known, e.g. breakup of clusters and molecules, ionisation and excitation of atoms.In laboratory experiments the ablation process has been investigated in detail. Carbon test samples with known layer properties are exposed by laser radiation in laboratory and in TEXTOR with comparable power densities.

Gierse, N.; Schweer, B.; Huber, A.; Karger, O.; Philipps, V.; Samm, U.; Sergienko, G.

2011-08-01

6

Depth-profile investigations of triterpenoid varnishes by KrF excimer laser ablation and laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

The ablation properties of aged triterpenoid dammar and mastic films were investigated using a Krypton Fluoride excimer laser (248 nm, 25 ns). Ablation rate variations between surface and bulk layers indicated changes of the ablation mechanisms across the depth profiles of the films. In particular, after removal of the uppermost surface varnish layers there was a reduction of the ablation step in the bulk that was in line with a significant reduction of carbon dimer emission beneath the surface layers as detected by laser-induced breakdown spectroscopy. The results are explicable by the generation of condensation, cross-linking and oxidative gradients across the depth profile of triterpenoid varnish films during the aging degradation process, which were recently quantified and established on the molecular level.

Theodorakopoulos, C.; Zafiropulos, V.

2009-07-01

7

Two-dimensional space-resolved emission spectroscopy of laser ablation plasma in water  

NASA Astrophysics Data System (ADS)

We developed a method for two-dimensional space-resolved emission spectroscopy of laser-induced plasma in water to investigate the spatial distribution of atomic species involved in the plasma. Using this method, the laser ablation plasma produced on a Cu target in 5 mM NaCl aqueous solution was examined. The emission spectrum varied considerably depending on the detecting position. The temperature and the atomic density ratio NNa/NCu at various detecting positions were evaluated by fitting emission spectra to a theoretical model based on the Boltzmann distribution. We are successful in observing even a small difference between the distributions of the plasma parameters along the directions vertical and horizontal to the surface. The present approach gives direct information for sound understanding of the behavior of laser ablation plasma produced on a solid surface in water.

Matsumoto, Ayumu; Tamura, Ayaka; Fukami, Kazuhiro; Ogata, Yukio H.; Sakka, Tetsuo

2013-02-01

8

Emission spectroscopy of laser ablation plasma with time gating by acousto-optic modulator  

NASA Astrophysics Data System (ADS)

The capability of acousto-optic modulator (AOM) to perform time-gated measurements for laser ablation plasma spectroscopy has been examined. Especially, we focused on the capability of the ``AOM gating'' to exclude the continuum and extremely broadened spectra usually observed immediately after the laser ablation. Final goal of the use of the AOM is to achieve considerable downsizing of the system for in situ and on-site analyses. In the present paper, it is shown that narrow and clear spectral lines can be obtained with the AOM gating even if the target is submerged in water. Also, application of this technique to the targets in air is demonstrated. It has been revealed that the AOM gating is fast enough to exclude the continuum and broadened lines, while effectively acquiring sufficiently narrow atomic lines lasting slightly longer than the continuum.

Sakka, Tetsuo; Irie, Kyohei; Fukami, Kazuhiro; Ogata, Yukio H.

2011-02-01

9

Emission spectroscopy of laser ablation plasma with time gating by acousto-optic modulator  

SciTech Connect

The capability of acousto-optic modulator (AOM) to perform time-gated measurements for laser ablation plasma spectroscopy has been examined. Especially, we focused on the capability of the ''AOM gating'' to exclude the continuum and extremely broadened spectra usually observed immediately after the laser ablation. Final goal of the use of the AOM is to achieve considerable downsizing of the system for in situ and on-site analyses. In the present paper, it is shown that narrow and clear spectral lines can be obtained with the AOM gating even if the target is submerged in water. Also, application of this technique to the targets in air is demonstrated. It has been revealed that the AOM gating is fast enough to exclude the continuum and broadened lines, while effectively acquiring sufficiently narrow atomic lines lasting slightly longer than the continuum.

Sakka, Tetsuo [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Institute of Sustainability Science, Kyoto University, Uji, Kyoto 611-0011 (Japan); Irie, Kyohei; Fukami, Kazuhiro; Ogata, Yukio H. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan)

2011-02-15

10

Laser induced breakdown spectroscopy surface analysis correlated with the process of nanoparticle production by laser ablation in liquids  

NASA Astrophysics Data System (ADS)

Laser induced ablation of solids situated in liquids (LAL) was used in order to produce nanoparticles. Laser induced breakdown spectroscopy (LIBS) surface analysis correlated with the process of nanoparticle production by LAL was applied to explain the composition of the obtained nanoparticles as determined by Electron Dispersive X-ray Spectroscopy (EDS). In the case of aluminum rods placed in distilled water irradiated with pulsed laser radiation (355 nm wavelength, 6 ns pulse length) we have obtained spheric nanoparticles with dimensions lower than 100 nm. Quantitative EDS analyses on the obtained spheres showed the presence of, Al, O, and Si. This indicates that probably the composition of the nanoparticles is an aluminum silicate. LIBS analysis on the aluminum target have shown the presence of a Si line with low intensity indicating a small quantity of silicon in the first ablated layers. The LIBS spectra for a sequence of pulses evidenced also that the intensity of the aluminum lines after a number of pulses decreases. This means that the quantity of ablated material becomes smaller due to the ablation depth decrease.

Apostol, I.; Damian, V.; Damian, R.; Nistor, L. C.; Pascu, A.; Staicu, A.; Udrea, C.

2013-04-01

11

Two-tracer spectroscopy diagnostics of temperature profile in the conduction layer of a laser-ablated plastic foil  

NASA Astrophysics Data System (ADS)

A technique that combines the diagnostics of electron temperature history and the measurements of ablation velocity with two-tracer x-ray spectroscopy has been developed for diagnosing the temperature profiles in the thermal conduction layers of laser-ablated plastic foils. The electron temperature in the plastic ablator was diagnosed using the isoelectronic line ratios of Al Ly? line to Mg Ly? line, emitted from a tracer layer of Al/Mg mixture buried under the ablator. The ablation velocity was inferred from the time delay between the onset time of x-ray line emissions from Al and Mg tracer layers buried at two depths in the ablator, respectively. From the measured electron temperatures and ablation velocity, the electron temperature profile in the conduction layer was inferred. The measured temperature profile was compared with the simulated one and reasonable agreement was found.

Zhang, Jiyan; Yang, Guohong; Hu, Xin; Yang, Jiamin; Ding, Yaonan; Ding, Yongkun; Zhang, Baohan; Zheng, Zhijian; Xu, Yan; Yan, Jun; Pei, Wenbin

2010-11-01

12

Hook spectroscopy as an atomic number density diagnostic applied to laser-ablated copper plasmas  

SciTech Connect

Hook spectroscopy has been used to determine the absolute number density of ground state copper atoms in laser-ablated plasma plumes. An ablation laser power flux of {approximately} 1.5 GW/cm{sup 2} is applied to a solid copper target in a background gas, producing a plasma plume suitable for studying homogeneous copper vapor condensation. Density is measured at post-ablation time delays ranging from 10 {mu}s to 3 ms with 25 torr of argon as the background gas. Planar laser-induced fluorescence (PLEF) images containing relative density information are used in conjunction with the hook spectra to resolve spatially the absolute density within the plume. Copper atom densities thus measured ranged from 1.9 {times} 10{sup 15} cm{sup {minus}3} at a delay of 10 {mu}s to 2.7 {times} 10{sup 13} cm{sup {minus}3} at 3 ms delay in 25 torr of argon The decrease in density is due to the condensation of copper vapor to form fine particulate. As a combustion diagnostic, the hook method may prove extremely useful for the determination of metal impurity density in coal fired flames as well as a single -- shot OH density and temperature diagnostic.

Zerkle, D.K.; Sappey, A.D.; Gamble, T.K.

1993-11-01

13

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

NASA Astrophysics Data System (ADS)

Laser-based methods are investigated for the development of an in situ diagnostic for spatially and temporally resolved characterization of the first wall in fusion devices. Here we report on the first systematic laser-induced ablation spectroscopy (LIAS) measurements carried out on various surface layers in the TEXTOR tokamak. These materials include a-C:D, mixed W/C/Al/D2, Oerlikon Balzers 'Balinit' diamond-like carbon layers and EK98 fine-grain graphite. In LIAS, the bulk or deposited material is evaporated during the plasma discharge by intense laser radiation. The light emitted by particles entering the edge of the ionizing tokamak plasma is then observed by optical spectroscopy. In the measurements taken, it was found that the studied layers can be identified by their characteristic line emission. A good correlation between the observed line intensity and layer thickness is found. The observed plumes show target material dependence. To analyze layers formed during tokamak operation, further investigation of the ablation process and reference materials for cross calibration is required.

Gierse, N.; Brezinsek, S.; Giesen, T. F.; Huber, A.; Laengner, M.; Leyte-Gonzales, R.; Marot, L.; Meyer, E.; Möller, S.; Naiim-Habib, M.; Philipps, V.; Pospieszczyk, A.; Schweer, B.; Sergienko, G.; Zlobinski, M.; Samm, U.; TEXTOR Team

2011-12-01

14

Laser ablation: LIBS and ICPMS  

SciTech Connect

Laser ablation has become a dominant technology for directsolid sampling chemical analysis. Commonly used detection modalitiesinclude LIBS (laser induced breakdown spectroscopy) for directspectroscopic analysis from the laser-induced plasma at the samplesurface,and ICPMS (inductively coupled plasma mass spectroscopy) in whichthe ablated aerosol is transported and excited in a secondary source.Each measurement approach dictates the laser parameters required foroptimum performance. Fundamental and experimental research studies haveled to significant improvements in performance metrics for laser ablationsolid sampling chemical analysis using both LIBS and ICPMS.

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

2006-08-29

15

Laser ablation of blepharopigmentation  

SciTech Connect

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

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

1988-01-01

16

Calcium detection of human hair and nail by the nanosecond time-gated spectroscopy of laser-ablation plume  

NASA Astrophysics Data System (ADS)

We demonstrate the nanosecond time-gated spectroscopy of plume in laser ablation of biological tissue, which allows us to detect calcium (Ca) with high sensitivity by the use of either a UV or a near-IR laser pulse. Clear and sharp peaks of Ca+ appear in the luminescence spectrum of laser-ablation plume although the Ca content is only 0.1 percent in human hair and nail. Luminescence peaks of sodium atom (Na) and ionized carbon are also detectable. This specific spectroscopy is low invasive because a single low-energy laser pulse illuminates the tissue sample, and it does not require any poisonous sensititizers like fluorescence dye. This method, therefore, is a promising candidate for optical biopsy in the near future. In particular, Ca detection of human hair may lead to new diagnosis, including monitor of daily intake of Ca and a screening diagnosis of osteoporosis.

Haruna, Masamitsu; Ohmi, Masato; Nakamura, Mitsuo; Morimoto, Shigeto

2000-04-01

17

Fundamental characteristics of laser-material interactions (ablation) in noble gases at atmospheric pressure using inductively coupled plasma-atomic emission spectroscopy  

Microsoft Academic Search

Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is used to study fundamental behavior underlying the explosive removal of solid material by high power pulsed laser irradiation. The influence of power density (irradiance) and carrier gas environment on the mass ablation rate behavior is discussed. Data are presented for nanosecond and picosecond laser ablation of metals.

Richard E. Russo; Xianglei L. Mao; Manuel Caetano; Mark A. Shannon

1996-01-01

18

Laser-ablation processes.  

National Technical Information Service (NTIS)

The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10(sup 13) W/cm(sup ...

R. S. Dingus

1992-01-01

19

Laser-ablation processes  

SciTech Connect

The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10{sup 13} W/cm{sup 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, R.S.

1992-05-01

20

Laser-ablation processes  

SciTech Connect

The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10{sup 13} W/cm{sup 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, R.S.

1992-01-01

21

Micro-spectrochemical analysis of document paper and gel inks by laser ablation inductively coupled plasma mass spectrometry and laser induced breakdown spectroscopy  

Microsoft Academic Search

Current methods used in document examinations are not suitable to associate or discriminate between sources of paper and gel inks with a high degree of certainty. Nearly non-destructive, laser-based methods using laser induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used to improve the forensic comparisons of gel inks, ballpoint inks and document papers

Tatiana Trejos; Alejandra Flores; José R. Almirall

2010-01-01

22

Laser ablation sampling  

Microsoft Academic Search

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

Richard E Russo; Xianglei Mao; Oleg V Borisov

1998-01-01

23

Representative sampling using single-pulse laser ablation withinductively coupled plasma mass spectroscopy  

SciTech Connect

Single pulse laser ablation sampling with inductively coupled plasma mass spectrometry (ICP-MS) was assessed for accurate chemical analysis. Elemental fractionation (e.g. Pb/U), the quantity of ablated mass (crater volume), ICP-MS intensity and the particle contribution (spike signal) during single pulse ablation of NIST 610 glass were investigated. Pb/U fractionation significantly changed between the first and second laser pulse and showed strong irradiance dependence. The Pb/U ratio obtained by the first pulse was usually higher than that of the second pulse, with the average value close to the representative level. Segregation during laser ablation is proposed to explain the composition change between the first and second pulse. Crater volume measurements showed that the second pulse produced significantly more ablated mass. A roll-off of the crater depth occurred at {approx}750 GW/cm{sup 2}. The absolute ICP-MS intensity from the second pulse showed no correlation with crater depth. Particle induced spikes on the transit signal showed irradiance and elemental species dependence.

Liu, Haichen; Mao, Xianglei; Russo, Richard E.

2001-04-02

24

Liquid sampling-atmospheric pressure glow discharge optical emission spectroscopy detection of laser ablation produced particles: A feasibility study  

NASA Astrophysics Data System (ADS)

The use of a liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma source as an alternative to conventional inductively coupled plasma (ICP) detection of laser ablation (LA) produced particles using a Nd:YAG laser at 1064 nm is demonstrated. This configuration utilizes a 180° geometry, which is different from the 40° geometry that was used to ionize ablated particles followed by mass spectrometric detection. The use of a hollow counter electrode (nickel, 0.3 cm o.d., 0.1 cm i.d.) was implemented to introduce ablated particles directly into the APGD plasma with helium as a carrier gas. The LS-APGD source was optimized using ablated copper as the test sample (helium carrier gas flow rate (0.30 L min- 1 He), discharge current (60 mA), laser power (44 mJ), and solution electrode sheath gas (0.2 L min- 1 He) and solution flow rates (10 ?L min- 1 5% HNO3)). Standard brass samples having known Zn/Cu percentages were ablated and analyzed using the LS-APGD source. As a comparison, the established technique of laser-induced breakdown spectroscopy (LIBS) was used to analyze the same set of brass standards under similar ablation conditions to the LS-AGPD measurements, yielding comparable results. The Zn/Cu ratio results for the LS-APGD and LIBS measurements showed good similarity to previous measurements using ICP-MS detection. The performance of the LS-APGD-OES microplasma, comparable to well established methods, with lower capital and operational overhead expenses, suggests a great deal of promise as an analytical excitation source.

Quarles, C. Derrick, Jr.; Gonzalez, Jhanis; Choi, Inhee; Ruiz, Javier; Mao, Xianglei; Marcus, R. Kenneth; Russo, Richard E.

2012-10-01

25

Pb distribution in bones from the Franklin expedition: synchrotron X-ray fluorescence and laser ablation/mass spectroscopy  

NASA Astrophysics Data System (ADS)

Synchrotron micro-X-ray Fluorescence has been used to map the metal distribution in selected bone fragments representative of remains associated with the Franklin expedition. In addition, laser ablation mass spectroscopy using a 25 ?m diameter circular spot was employed to compare the Pb isotope distributions in small regions within the bone fragments. The X-ray Fluorescence mapping shows Pb to be widely distributed in the bone while the Pb isotope ratios obtained by laser ablation within small areas representative of bone with different Pb exchange rates do not show statistically significant differences. These results are inconsistent with the hypothesis that faulty solder seals in tinned meat were the principle source of Pb in the remains of the expedition personnel.

Martin, Ronald Richard; Naftel, Steven; Macfie, Sheila; Jones, Keith; Nelson, Andrew

2013-04-01

26

Investigation of heavy-metal accumulation in selected plant samples using laser induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Single-pulse Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass-Spectrometry (LA-ICP-MS)\\u000a were applied for mapping the silver and copper distribution in Helianthus Annuus L. samples treated with contaminant in controlled conditions. For Ag and Cu detection the 328.07 nm Ag(I) and 324.75 nm Cu(I)\\u000a lines were used, respectively. The LIBS experimental conditions (mainly the laser energy and the observation

M. Galiová; J. Kaiser; K. Novotný; J. Novotný; T. Vaculovic; M. Liska; R. Malina; K. Stejskal; V. Adam; R. Kizek

2008-01-01

27

Laser ablation and spectroscopy of copper in liquid and solid {sup 4}He  

SciTech Connect

We present an experimental study of the laser-induced fluorescence spectra of Cu atoms in bulk liquid and solid helium matrices as well as in the dense plasma created by the laser ablation of copper in liquid helium. We observe transitions of the valence electron and of inner-shell electrons. The former produce structureless line shapes, a large broadening, and a blueshift. The latter practically are not shifted with respect to the free atom and possess a substructure consisting of a zero-phonon line and phonon wings. We suggest a qualitative interpretation of the observed spectra based on the atomic bubble model that takes the lifting of the |M{sub J}| degeneracy due to the bubble deformation and matrix-phonon interactions into account.

Moroshkin, P.; Lebedev, V.; Weis, A. [Departement de Physique, Universite de Fribourg, Chemin du Musee 3, CH-1700 Fribourg (Switzerland)

2011-11-15

28

Nanoparticles by Laser Ablation  

Microsoft Academic Search

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

N. G. Semaltianos

2010-01-01

29

High resolution pulsed infrared cavity ringdown spectroscopy: Application to laser ablated carbon clusters  

NASA Astrophysics Data System (ADS)

We report the design and performance of a tunable, pulsed high resolution mid infrared cavity ringdown spectrometer. Stimulated Raman scattering in H2/D2 is used to downconvert the output of a SLM Alexandrite ring laser (720-800 nm) to the mid infrared (3-8 ?m). The infrared frequency bandwidth was determined to be 90+/-5 MHz from measurements of Doppler broadened OCS transitions at 5 ?m. The minimum detectable per pass fractional absorption is 1 ppm. We observe a frequency dependent ringdown cavity transmission of +/-5 ppm due to spatial variations of the mirror reflectivity. The ?6 band of linear C9 formed by laser ablation of graphite in a He molecular beam was measured, showing a factor of 2 improvement in sensitivity relative to previous IR diode laser experiments. Based on calculated IR intensities, the number density of C9 in the molecular beam is 1.3*1011 molec/cm3 and the minimum detectable density is 1*109 molec/cm3. We expect this spectrometer to be a powerful tool for the study of transient species formed in molecular beams.

Casaes, Raphael; Provençal, Robert; Paul, Joshua; Saykally, Richard J.

2002-04-01

30

Non-ablative lasers.  

PubMed

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

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

2011-08-16

31

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...

32

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

SciTech Connect

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

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

1995-02-01

33

Ultrasonic characterization of laser ablation.  

National Technical Information Service (NTIS)

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

J. A. Smith K. L. Telschow

1991-01-01

34

Femtosecond laser ablation of bovine cortical bone  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

35

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

36

Diagnostics Techniques of Plasmas Produced by Laser Ablation  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

37

Laser spectroscopy  

NASA Astrophysics Data System (ADS)

The primary purpose of this trip was to present two invited lectures at the Second Venezuelan Workshop on Laser Spectroscopy. This conference included essentially all of the Venezuelan researchers active in this area. In addition, four speakers from outside of Venezuela were invited to this meeting; two from the USA and two from the former Soviet Union (FSU). The primary topics of the meeting were fluorescence spectroscopy, photothermal spectroscopy, and laser - material interactions. Prior to the conference, three institutions in Caracas were visited (IVIC, USB, and UCV) and a presentation was given at UCV. The group of scientists and students attending the conference were interested in establishing collaborations with scientists in the USA.

Ramsey, J. M.

1992-12-01

38

Species-resolved imaging and gated photon counting spectroscopy of laser ablation plume dynamics during KrF- and ArF-laser PLD of amorphous diamond films  

SciTech Connect

Gated photon counting spectroscopy and species-resolved ICCD photography were used to study the weak plasma luminescence following the propagation of the initial ablation plume in vacuum and during the rebound of the plume with a substrate during pulsed laser deposition of amorphous diamond. These methods techniques were required in order to investigate notable differences between amorphous diamond-like carbon films formed by pulsed laser deposition from ArF (193 nm) and KrF (248 nm) irradiation of pyrolytic graphite in vacuum. Three principal regions of plume emission were found: (1) a bright luminescent ball (v {approximately}3--5 cm/{mu}s) displaying nearly entirely C{sup +} emission which appears to result from laser interaction with the initial ejecta, (2) a spherical ball of emission (v {approximately} 1 cm/{mu}s) displaying neutral carbon atomic emission lines and, at early times, jets of excited C{sub 2}, and (3) a well-defined region of broadband emission (v {approximately} 0.3 cm/{mu}s) near the target surface first containing emission bands from C{sub 2}, then weak, continuum emission thought to result from C{sub 3} and higher clusters and/or blackbody emission from hot clusters or nanoparticles.

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

1995-12-01

39

Dynamics of femtosecond-laser-ablated liquid-aluminum nanoparticles probed by means of spatiotemporally resolved X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

We investigated spatiotemporal evolution of expanding ablation plume of aluminum created by a 100-fs, 1014-1015-W/cm2 laser pulse. For diagnosing dynamic behavior of ablation plume, we employed the spatiotemporally resolved X-ray absorption spectroscopy (XAS) system that consists of a femtosecond-laser-plasma soft X-ray source and a Kirkpatrick-Baez (K-B) microscope. We successfully assigned the ejected particles by analyzing structure of absorption spectra near the L II,III absorption edge of Al, and we clarified the spatial distribution of Al+ ions, Al atoms, and liquid droplets of Al in the plume. We found that the ejected particles strongly depend the irradiated laser intensity. The spatial distribution of atomic density and the expansion velocity of each type of particle were estimated from the spatiotemporal evolution of ablation particles. We also investigated a temperature of the aluminum fine particles in liquid phase during the plume expansion by analyzing the slope of the L II,III absorption edge in case of 1014-W/cm2 laser irradiation where the nanoparticles are most efficiently produced. The result suggests that the ejected particles travel in a vacuum as a liquid phase with a temperature of about 2500 to 4200 K in the early stage of plume expansion.

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

2010-11-01

40

Laser ablation in analytical chemistry - A review  

Microsoft Academic Search

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

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

2001-01-01

41

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

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-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM  

SciTech Connect

This report describes the installation, testing, and acceptance of the Waste Treatment and Immobilization Plant (WTP) procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste (HLW) samples in a hot cell environment. The work was completed by the Analytical Process Development (APD) group in accordance with Task Order 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S Laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

SEIDEL CM; JAIN J; OWENS JW

2009-02-23

44

LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM  

SciTech Connect

This report describes the installation, testing and acceptance of the Waste Treatment and Immobilization Plant procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste samples in a hot cell environment. The 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

LOCKREM LL; OWENS JW; SEIDEL CM

2009-03-26

45

Ablation of metals by ultrashort laser pulses  

Microsoft Academic Search

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

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

2005-01-01

46

Temporal pulse shaping effects on aluminium and boron ablation plumes generated by ultrashort pulsed laser ablation and analyzed by time- and space-resolved optical spectroscopy  

NASA Astrophysics Data System (ADS)

This paper focuses on the effect of temporal shaping of femtosecond laser pulses on laser ablation of aluminium and boron. The influence on plasma composition is deduced from optical emission investigations. Irradiation generated by the temporal tailoring of an incident laser pulse into double pulses or longer pulses is examined and compared to results deduced from hydrodynamic simulations of plasma temperature profiles. Above the ion formation threshold, increasing the delay in the double pulses sequence or increasing the pulse duration leads to an increase of the ion emission of the plasma plume of aluminium or boron. The observed increase with a saturation of ion emission at long delays or long pulse durations result from an interaction between the shaped laser pulse and the expanding matter after the onset of the plasma. Irradiation of boron with long pulses or double pulses reduces the production of nanoparticles, compared to the case of short pulses. Temporal shaping does not significantly affect the nanoparticle temperature, in spite of significant variations in the quantity of the ejected nanoparticles.

Bourquard, F.; Colombier, J.-P.; Guillermin, M.; Loir, A.-S.; Donnet, C.; Stoian, R.; Garrelie, F.

2012-09-01

47

Temperature and Emission Spatial Profiles of Laser-Induced Plasmas during Ablation Using Time-Integrated Emission Spectroscopy  

Microsoft Academic Search

Emission spectra and excitation temperature spatial profiles, within la- ser-induced plasmas from solid copper targets, are characterized as a function of laser power density with the use of time-integrated emission spectroscopy. This research shows how the measured axial spatial emis- sion intensity of the expanding plasma can be influenced by the time integration. The excitation temperatures calculated from these inte-

Xianglei L. Mao; Mark A. Shannon; Alberto J. Fernandez; Richard E. Russo

1995-01-01

48

Magnetic Colloids By Pulsed Laser Ablation  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

49

Real-Time Analysis of Individual Airborne Microparticles Using Laser Ablation Mass Spectroscopy and Genetically Trained Neural Networks  

SciTech Connect

We are developing a method for analysis of airborne microparticles based on laser ablation of individual molecules in an ion trap mass spectrometer. Airborne particles enter the spectrometer through a differentially-pumped inlet, are detected by light scattered from two CW laser beams, and sampled by a pulsed excimer laser 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. The mass spectra are then analyzed using genetically-trained neural networks (NNs). A number of mass spectra are averaged to obtain training cases which contain a recognizable spectral signature. Averaged spectra for a bacteria and a non-bacteria are shown to the NNs, the response evaluated, and the weights of the connections between neurodes adjusted by a Genetic Algorithm (GA) such that the output from the NN ranges from 0 for non-bacteria to 1 for bacteria. This process is iterated until the population of the GA converges or satisfies predetermined stopping criteria. Using this type of bipolar training we have obtained generalizing NNs able to distinguish five new bacteria from five new non-bacteria, none of which were used in training the NN.

Parker, E.P.; Rosenthal, S.E.; Trahan, M.W.; Wagner, J.S.

1999-01-22

50

Parametric study of CN films deposited by reactive laser ablation  

Microsoft Academic Search

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

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

1997-01-01

51

Basic ablation phenomena during laser thrombolysis  

Microsoft Academic Search

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

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

1997-01-01

52

Laser ablation at the hydrodynamic regime  

NASA Astrophysics Data System (ADS)

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

Gojani, Ardian B.

2013-04-01

53

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

Microsoft Academic Search

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

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

2009-01-01

54

Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

Anderson localization of matter-waves in a controlled disorder: a quantum simulator? / A. Aspect ... [et al.] -- Squeezing and entanglement in a Bose-Einstein condensate / C. Gross ... [et al.] -- New physics in dipolar Bose-Einstein condensates / Y. Kawaguchi, H. Saito, and M. Ueda -- Observation of vacuum fluctuations in a spinor Bose-Einstein condensate / C. Klempt ... [et al.] -- Negative-index media for matter waves / F. Perales ... [et al.] -- Entanglement of two individual atoms using the Rydberg blockade / A. Browaeys ... [et al.] -- Array of mesoscopic ensembles on a magnetic atom chip / A. F. Tauschinsky ... [et al.] -- Stability of the proton-to-electron mass ratio tested with molecules using an optical link to primary clock / A. Amy-Klein ... [et al.] -- Metastable helium: lifetime measurements using cold atoms as a test of QED / K. G. H. Baldwin ... [et al.] -- Optical lattice clocks with single occupancy bosons and spin-polarized fermions toward 10[symbol] accuracy / M. Takamoto ... [et al.] -- Frequency measurements of Al[symbol] and Hg[symbol] optical standards / W. M. Itano ... [et al.] -- Switching of light with light using cold atoms inside a hollow optical fiber / M. Bajcsy ... [et al.] -- Room-temperature atomic ensembles for quantum memory and magnetometry / K. Jensen ... [et al.] -- Components for multi-photon non-classical state preparation and measurement / G. Puentes ... [et al.] -- Quantum field state measurement and reconstruction in a cavity by quantum nondemolition photon counting / M. Brune ... [et al.] -- XUV frequency comb spectroscopy / C. Gohle ... [et al.] -- Ultrahigh-repetition-rate pulse train with absolute-phase control produced by an adiabatic raman process / M. Katsuragawa ... [et al.] -- Strongly correlated bosons and fermions in optical lattices / S. Will ... [et al.] -- Bragg spectroscopy of ultracold bose gases in optical lattices / L. Fallani ... [et al.] -- Synthetic quantum many-body systems / C. Guerlin ... [et al.] -- Ultracold Ytterbium atoms in optical lattices / S. Sugawa ... [et al.] -- Ultracold polar molecules in the rovibrational ground state / J. Deiglmayr ... [et al.] -- Polar molecules near quantum degeneracy / J. Ye and D. S. Jin -- Production of a quantum gas of rovibronic ground-state molecules in an optical lattice / J. G. Danzl ... [et al.] -- Recent progress in x-ray nonlinear optics / K. Tamasaku, K. Sawada, and T. Ishikawa -- Gas in scattering media absorption spectroscopy - laser spectroscopy in unconventional environments / S. Svanberg -- Laser spectroscopy on relativistic ion beams / S. Reinhardt ... [et al.] -- Single frequency microcavity lasers and applications / L. Xu ... [et al.].

Katori, H.; Yoneda, H.; Nakagawa, K.; Shimizu, F.

2010-02-01

55

Optical transient absorption spectroscopy of LaO produced by pulsed laser ablation of La2O3.  

PubMed

Temporally and spatially resolved absorption spectrometry has been used to study molecular LaO absorption in laser ablated plume from an La2O3 target The absorption time-of-flight (TOF) spectra of ground-state LaO molecules were measured The TOF spectra indicate that only one component is observed in vacuum and in an Ar ambient, while there are two component, a fast and a broad slow component, observed at higher O2 pressure. The absorbance of LaO molecules decreases gradually with increasing ambient gas pressure. The dependence of the absorbance of LaO on the detection distance can be fitted by an exponential decay equation. The shock wave model is used to describe the behavior of ground state LaO molecules in high O2 pressure region. PMID:10728868

Tang, Y; Yang, X; Liu, X; Qin, Q

2000-01-01

56

Direct measurements of sample heating by a laser-induced air plasma in pre-ablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS).  

PubMed

Direct measurements of temperature changes were made using small thermocouples (TC), placed near a laser-induced air plasma. Temperature changes up to ~500 °C were observed. From the measured temperature changes, estimates were made of the amount of heat absorbed per unit area. This allowed calculations to be made of the surface temperature, as a function of time, of a sample heated by the air plasma that is generated during orthogonal pre-ablation spark dual-pulse (DP) LIBS measurements. In separate experiments, single-pulse (SP) LIBS emission and sample ablation rate measurements were performed on nickel at sample temperatures ranging from room temperature to the maximum surface temperature that was calculated using the TC measurement results (500 °C). A small, but real sample temperature-dependent increase in both SP LIBS emission and the rate of sample ablation was found for nickel samples heated up to 500 °C. Comparison of DP LIBS emission enhancement values for bulk nickel samples at room temperature versus the enhanced SP LIBS emission and sample ablation rates observed as a function of increasing sample temperature suggests that sample heating by the laser-induced air plasma plays only a minor role in DP LIBS emission enhancement. PMID:22800813

Register, Janna; Scaffidi, Jonathan; Angel, S Michael

2012-07-13

57

Picosecond laser ablation of thin copper films  

Microsoft Academic Search

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

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

1996-01-01

58

Polarization-resolved measurements of picosecond laser-ablated plumes  

SciTech Connect

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

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

2005-08-01

59

Analysis of geological samples by atomic emission spectroscopy of plasmas induced by laser ablation at low pressures  

NASA Astrophysics Data System (ADS)

Elemental analysis of geologic samples based on atomic emission spectroscopy is currently considered for several future space lander missions to planets, moons and asteroids in solar system. The spectroscopic techniques, called laser-induced plasma (breakdown) spectroscopy (LIBS), provides quantitatively the microscopic in-situ abundances of all major and many trace elements of surfaces of solar system bodies. Excitation and evolution of the plasmas induced by lasers depend on the properties of the investigated material and on environmental conditions. This study focuses on the feasibility of spectroscopy of plasmas induced by low-energy laser (below 1 mJ per pulse) for the exploration of solar system bodies with thin atmospheres (pressures below 1 mPa). At such low pressures the excited plasmas have small plumes and expand very rapidly, which limits both the LIBS signal intensity and the available acquisition time. This, in turn, requires usually relatively powerful laser sources to create a detectable LIBS plasma. The low pressure conditions are simulated in a dedicated chamber at the DLR-Berlin Institute of Planetary Research, that can hold the Martian-like atmosphere or high vacuum conditions. Two infrared Q-switched lasers are used for comparative investigation of atomic emission spectra: Firstly, a Nd:YAG laser (Inlite, Continuum) operating at 1064 nm and at 10 Hz, pulse energy up to 230 mJ at 8-10 ns pulse duration and, secondly, developed for future planetary missions Nd:YLF laser (NeoLASE) operating at 1053 nm and at 10-50 Hz, pulse energy up to 3 mJ at 3-5 ns pulse duration. The emitted light of the laser-induced plasma is analysed by an echelle spectrometer (LTB Aryelle Butterfly) covering the wavelength range of 280-900 nm with a spectral resolution of around 104. Identification of atomic transitions is performed using the LTB built-in spectrometer software by comparison with the NIST spectral database. Several basaltic rock and sediment standards were crushed to powder and pressed into pellets. Reduction of both pressure and laser excitation energy results in a significant decrease of the signal-to-noise ratio for most atomic lines (an exception are the widely broadened lines of H). However, the detection of atomic emission lines of elements with relative abundances above 10-3 (0.1 wt%) - Al, Ca, Cr, H, K, Mg, Mn, Na, Ni, O, Si, Ti, - is possible down to a laser excitation energy of 0.9 mJ (laser irradiance on the sample surface 46 MW/mm2). Additionally, the detection of carbon and sulphur, having strong atomic transitions in ultraviolet range, can be expected by extension of the spectral range of the LIBS spectrometer to 190 nm. Atomic doublet and triplet transitions, broadened by atomic collisions at ambient pressures (100 kPa), become spectrally resolved and are identified below 1 mPa. This demonstrates the feasibility of miniaturized laser-induced breakdown spectrometry for space missions to solar bodies with absent or thin atmospheres.

Pavlov, S.; Schröder, S.; Jessberger, E.; Hübers, H.

2011-12-01

60

Ablation of metals by ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

61

Dynamics of Laser Driven, Ablatively Accelerated Targets.  

National Technical Information Service (NTIS)

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

J. Grun

1981-01-01

62

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

NASA Astrophysics Data System (ADS)

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

Lash, Joel Staton

63

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

64

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...

65

Laser ablation studies using RIS  

SciTech Connect

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

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

1984-01-01

66

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

Microsoft Academic Search

The aim of this work is to elucidate the ablation-induced plasma physics for chemical species analysis by laser-induced breakdown spectroscopy at higher spatial resolution. To accomplish this, the effect of the laser spot size on the laser ablation-induced plasma characteristics is experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of ~200 nm thickness

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

2008-01-01

67

Selective ablation of Copper-Indium-Diselenide solar cells monitored by laser-induced breakdown spectroscopy and classification methods  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) and two classification methods, i.e. linear correlation and artificial neural networks (ANN), are used to monitor P1, P2 and P3 scribing steps of Copper-Indium-Diselenide (CIS) solar cells. Narrow channels featuring complete removal of desired layers with minimum damage on the underlying film are expected to enhance efficiency of solar cells. The monitoring technique is intended to determine that enough material has been removed to reach the desired layer based on the analysis of plasma emission acquired during multiple pass laser scribing. When successful selective scribing is achieved, a high degree of similarity between test and reference spectra has to be identified by classification methods in order to stop the scribing procedure and avoid damaging the bottom layer. Performance of linear correlation and artificial neural networks is compared and evaluated for two spectral bandwidths. By using experimentally determined combinations of classifier and analyzed spectral band for each step, classification performance achieves errors of 7, 1 and 4% for steps P1, P2 and P3, respectively. The feasibility of using plasma emission for the supervision of processing steps of solar cell manufacturing is demonstrated. This method has the potential to be implemented as an online monitoring procedure assisting the production of solar cells.

Diego-Vallejo, David; Ashkenasi, David; Lemke, Andreas; Eichler, Hans Joachim

2013-09-01

68

Microporous polymer surfaces prepared by an excimer laser ablation technique.  

PubMed

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

Nakayama, Y; Matsuda, T

69

Power dependence of size of laser ablated colloidal silver nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

70

Influence of deposition parameters on laser ablation deposited amorphous carbon  

Microsoft Academic Search

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

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

1995-01-01

71

Mössbauer Study of Iron Films Produced by Laser Ablation  

Microsoft Academic Search

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

Kentarou Namiki; Daisuke Yokoyama; Yasuhiro Yamada

2005-01-01

72

Electron beam ablation versus laser ablation: plasma plume diagnostic studies  

Microsoft Academic Search

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

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

1998-01-01

73

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

74

Femtosecond laser ablation ICP-MS  

SciTech Connect

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

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

2002-02-15

75

Characterization of high performance polymers transferred by resonant infrared laser ablation  

Microsoft Academic Search

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

Nicole L. Dygert; Richard F. Haglund Jr.

2008-01-01

76

CO2 Laser Ablation Propulsion Tractor Beams  

NASA Astrophysics Data System (ADS)

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

Sinko, John E.; Schlecht, Clifford A.

2010-05-01

77

Laser ablation in analytical chemistry - A review  

SciTech Connect

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

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

2001-10-10

78

Laser ablation of hymenal fissures.  

PubMed

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

Michlewitz, H

1986-01-01

79

KrF-laser ablation of polyurethane  

Microsoft Academic Search

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

S. Küper; J. Brannon

1993-01-01

80

Dynamics of laser driven, ablatively accelerated targets  

Microsoft Academic Search

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

J. Grun

1981-01-01

81

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

Microsoft Academic Search

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

Joel Staton Lash

1996-01-01

82

KrF laser ablation of polyurethane  

Microsoft Academic Search

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

Stephan Kueper; James H. Brannon

1991-01-01

83

Innovative Laser Ablation Technology for Surface Decontamination  

SciTech Connect

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

Chen, Winston C. H.

2002-06-01

84

Influence of the liquid environment on the products formed from the laser ablation of tin  

NASA Astrophysics Data System (ADS)

Tin targets immersed in ethanol and distilled water were ablated using a UV pulsed laser. The ablated products were investigated with transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. For ablation in both liquids, the size distribution of the produced particles was bimodal, with particles having diameters of ˜10 nm and ˜1 ?m. Formation mechanisms that caused the bimodal distribution are suggested. Ablation in ethanol resulted in nanoparticles that were found to be single crystals of tin coated with tin hydroxide (Sn(OH)2) while ablation in water yielded nanoparticles that were polycrystalline tin dioxide (SnO2) throughout.

Musaev, O. R.; Driver, M. S.; Sutter, E. A.; Caruso, A. N.; Wrobel, J. M.; Kruger, M. B.

2013-02-01

85

Influence of the liquid environment on the products formed from the laser ablation of tin  

NASA Astrophysics Data System (ADS)

Tin targets immersed in ethanol and distilled water were ablated using a UV pulsed laser. The ablated products were investigated with transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. For ablation in both liquids, the size distribution of the produced particles was bimodal, with particles having diameters of ˜10 nm and ˜1 ?m. Formation mechanisms that caused the bimodal distribution are suggested. Ablation in ethanol resulted in nanoparticles that were found to be single crystals of tin coated with tin hydroxide (Sn(OH)2) while ablation in water yielded nanoparticles that were polycrystalline tin dioxide (SnO2) throughout.

Musaev, O. R.; Driver, M. S.; Sutter, E. A.; Caruso, A. N.; Wrobel, J. M.; Kruger, M. B.

2013-11-01

86

Velocity and metastable state population distributions of laser-ablated neodymium  

NASA Astrophysics Data System (ADS)

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

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

2004-10-01

87

Laser Ablation of Alumina in Water  

SciTech Connect

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

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

2010-01-01

88

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

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

Hirata, Takafumi

2003-01-15

89

Nanosecond laser ablation of gold nanoparticle films  

SciTech Connect

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

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

2006-10-02

90

Subpicosecond laser ablation of dental enamel  

NASA Astrophysics Data System (ADS)

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

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

2002-08-01

91

Analysis of infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

92

Evolution and imaging of nanoparticles observed in laser ablated carbon plume  

Microsoft Academic Search

We report evidence of nanoparticles formation in laser ablated carbon plasma created by irradiating a graphite target with nanosecond neodymium doped yttrium aluminum garnet laser. The temporal evolution and spatial distribution of C2 molecules in the plasma is studied using optical emission spectroscopy, dynamic imaging and laser induced fluorescence techniques. The laser induced fluorescence spectrum and imaging of C2 fluorescence

Dheerendra Yadav; Varun Gupta; Raj K. Thareja

2009-01-01

93

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

SciTech Connect

The ablation-induced plasma physics at reduced ablation crater dimensions is experimentally investigated. Frequency doubled femtosecond laser pulses are tightly focused through objective lenses onto a Cr thin film coated on quartz wafer in order to obtain ablation craters of submicron lateral dimensions. Side-view time-resolved emission images and the corresponding spectra depict the detailed plasma evolution at the fluence range near the ablation threshold. Collected emission spectra at the laser fluence level of around two to three times of ablation threshold display characteristic atomic transition peaks of the ablated Cr material from submicron ablation craters. This finding confirms that improved spatial resolution for laser-induced breakdown spectroscopy can be achieved.

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

2007-12-17

94

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

SciTech Connect

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

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

2008-07-01

95

Hafnium Oxide Film Synthesis via Laser Ablation Plasma Ion Deposition  

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

96

Optical modeling of laser ablated microstructures  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

97

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

Microsoft Academic Search

Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the

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

2005-01-01

98

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

Microsoft Academic Search

Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature

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

2005-01-01

99

Investigation of matrix effects in inductively coupled plasma-atomic emission spectroscopy using laser ablation and solution nebulization — effect of second ionization potential  

Microsoft Academic Search

Plasma-related non-spectroscopic matrix effects of 31 elements in inductively coupled plasma (ICP)-atomic emission spectrometry were investigated using both laser ablation and solution nebulization as sample introduction techniques. Matrix effects were studied by monitoring the excitation conditions of the plasma using the ionic to atomic spectral line intensity ratios of zinc and magnesium. A new kind of matrix interference was found

George C.-Y. Chan; Wing-Tat Chan; Xianglei Mao; Richard E. Russo

2001-01-01

100

Nanosecond laser ablation of silver nanoparticle film  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

101

Interaction of flows of laser ablation plasmas  

SciTech Connect

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

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

1997-04-01

102

Interaction of flows of laser ablation plasmas  

SciTech Connect

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

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

1997-04-15

103

Rapid tooling using controlled laser ablation  

NASA Astrophysics Data System (ADS)

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

Geiger, Manfred; Schubart, Doris; Kauf, Michael

1996-08-01

104

UV laser ablation patterns in intraocular lenses  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

105

Resonant laser ablation: mechanisms and applications  

SciTech Connect

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

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

1996-10-01

106

Tumour ablation by laser in general surgery  

Microsoft Academic Search

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

R. A. Sultan

1990-01-01

107

Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation  

SciTech Connect

Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

Kim, B.M.; Feit, M.D.; Rubenchick, A.M.; Gold, D.M.; Darrown, C.B.; Da Silva, L.B.

1998-01-01

108

Ultrashort Pulse Laser Ablation for Depth Profiling of Bacterial Biofilms  

PubMed Central

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

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

2010-01-01

109

Mapping of different structures on large area of granite sample using laser-ablation based analytical techniques, an exploratory study  

Microsoft Academic Search

Laser-ablation based analytical techniques represent a simple way for fast chemical analysis of different materials. In this work, an exploratory study of multi-element (Ca, Al, Fe, Mn) mappings of a granite sample surface was performed by laser-induced breakdown spectroscopy (LIBS) and subsequently by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. The operating parameters (e.g. pulse energy, ablation-crater size)

K. Novotny; J. Kaiser; M. Galiova; V. Kone?ná; J. Novotny; R. Malina; M. Liska; V. Kanický; V. Otruba

2008-01-01

110

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

NASA Astrophysics Data System (ADS)

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

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

2000-04-01

111

Laser Ablation for Small Hepatocellular Carcinoma  

PubMed Central

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

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

2011-01-01

112

KrF-laser ablation of polyurethane  

NASA Astrophysics Data System (ADS)

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

Küper, S.; Brannon, J.

1993-09-01

113

Dynamics of laser driven, ablatively accelerated targets  

NASA Astrophysics Data System (ADS)

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

Grun, J.

1981-05-01

114

Laser Ablation and Thin Film Deposition  

NASA Astrophysics Data System (ADS)

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

Schneider, Christof W.; Lippert, Thomas

115

Experimental studies on plasma emission spectroscopy of laser ablation of hexahydro-l,3,5-trinitro-l,3,5-triazine  

NASA Astrophysics Data System (ADS)

A Q-switched Nd: YAG laser (with a wavelength of 532 nm and a pulse width of 15 ns) was used to ablate hexahydrol, 3,5-trinitro-l,3,5-triazine (RDX) in the air. The plasma emission spectra were recorded by an intensified charge-coupled device (ICCD) camera. The results showed that the plasma existed in the process of laser ablation of RDX. In the ultraviolet area, the main spectral lines were C I (187.46 nm and 223.01 nm), C II (323.1 nm) and N II (243.72 nm and 332.9 nm), while the dominating emission lines in the visible area were N II (393.9 nm and 454.7 nm), O II (490.75 nm) and O III (401.2 nm). Under experimental conditions, the intensities of the main peaks grew obviously with the increasing of the pulse delay, but laser energy didn't have so much effect on the spectra. The ionization of the air almost did not influence plasma emission lines of RDX.

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

2013-05-01

116

F2 laser ablation of silicone rubber  

NASA Astrophysics Data System (ADS)

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

Takao, Hiromitsu; Okoshi, Masayuki; Inoue, Narumi

2004-10-01

117

Fabrication of gold nanoparticles in water by laser ablation technique and their characterization  

NASA Astrophysics Data System (ADS)

A colloidal solution of gold nanoparticles in deionized nanopure water was produced by laser ablation technique without the use of any chemical/surfactant. Spectral characterization and morphological studies of these nanoparticles were carried out by UV-Vis Spectroscopy and Scanning Electron Microscopy, respectively. A number of variables of the ablating laser pulse have been used to control the size of the fabricated nanoparticles. Excellent correlation between ablating laser pulse parameter and optical and morphological parameters of the gold colloids were obtained. The peak of the extinction spectra shows a monotonic blue shift for laser fluence of 410 J/cm2 and above. Below this the extinction peak remains fairly constant in wavelength. Blue shifts of the extinction spectra were also observed with increasing re-ablation time of previously ablated gold colloids. Possible explanations of all these observations are discussed.

Haider, A. F. M. Y.; Sengupta, S.; Abedin, K. M.; Talukder, Aminul I.

2011-11-01

118

Confined laser ablation for single-shot nanoparticle deposition of silver  

NASA Astrophysics Data System (ADS)

Spatially confined laser ablation of silver was used to form long-lived dense plasma for single-shot deposition of a nanoparticle film. The expansion of the ablation plume was restricted by placing a glass substrate at 50 ?m from the silver target surface. Time-resolved optical emission spectroscopy showed that the confined plasma is sustained for longer time than for free ablation. A single laser shot is sufficient to produce a layer of silver nanoparticles on the substrate. In absorption the nanoparticle layer displays a surface plasmon resonance which is comparable to films made by conventional pulsed laser deposition in vacuum.

Donnelly, T.; Lunney, J. G.

2013-10-01

119

Innovative Laser Ablation Technology for Surface Decontamination  

SciTech Connect

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

Chen, Winston C. H.

2003-06-01

120

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

121

117Sn and 119Sn hyperfine structure in the rotational spectrum of tin monosulfide recorded using laser ablation-source equipped, chirped-pulse Fourier transform microwave spectroscopy  

NASA Astrophysics Data System (ADS)

Tin metal has been ablated with pulsed radiation from a Nd:YAG laser (?=1064 nm). Carbonyl sulfide, diluted in high pressure argon, has been pulsed into the resultant Sn plasma. One of the results of this experiment has been the production of SnS. These events have allowed a rotational spectrum of tin monosulfide to be studied using a chirped-pulse Fourier transform microwave spectrometer. The resolution of the spectrum obtained was sufficient to observe hyperfine structure from the 117Sn and 119Sn-containing SnS molecules. Tin nuclear spin-rotation hyperfine constants are reported for the first time.

Grubbs, G. S.; Cooke, S. A.

2010-02-01

122

Free electron laser ablation of urinary calculi: an experimental study  

Microsoft Academic Search

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

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

2001-01-01

123

Ablation laser femtoseconde pour le dépôt de DLC  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

124

Double-pulse laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

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

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

2005-01-01

125

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

126

Surface Characterization of Laser-Ablated Polymers Used for Microfluidics  

Microsoft Academic Search

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

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

2002-01-01

127

Characterization of Laser-Ablated, Magnetized Carbon Plasmas Relevant to Magnetized Collisionless Shocks  

NASA Astrophysics Data System (ADS)

We present experiments on laser-ablated, magnetized carbon plasmas performed at the University of California, Los Angeles (UCLA). A graphite target placed inside a static magnetic field (1 kG) created by a 50 cm-diameter Helmholtz coil was ablated by laser pulses at 1053 nm with energies between 10-100 J. Magnetic flux probes measured the magnetic field compression and expulsion of the resulting blow-off plasma and diamagnetic bubble. A separate laser at 527 nm was used for Thomson scattering to characterize the electron temperature and density up to several cm from the target and several microseconds after the initial laser ablation. The carbon ionization states and blow-off velocities were further measured with emission spectroscopy. The data was used to inform 2D hybrid simulations of a laser-ablated plasma expanding into an ambient plasma, relevant to upcoming magnetized collisionless shock experiments on the Large Plasma Device at UCLA.

Schaeffer, D. B.; Bondarenko, A. S.; Everson, E. T.; Clark, E. S.; Constantin, C. G.; Niemann, C.; Winske, D.

2012-10-01

128

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

129

Modeling CO{sub 2} Laser Ablative Impulse with Polymers  

SciTech Connect

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

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

2010-10-08

130

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

Microsoft Academic Search

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

Danny Y Lin; Edward E Manche

2004-01-01

131

KrF laser ablation of polyurethane  

NASA Astrophysics Data System (ADS)

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

Kueper, Stephan; Brannon, James H.

1991-12-01

132

Inertial effects in laser-driven ablation  

SciTech Connect

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

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

1983-08-18

133

Laser ablation of multilayer polymer films  

SciTech Connect

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

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

1994-10-01

134

Pressure impulses during microsecond laser ablation.  

PubMed

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

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

1997-12-01

135

Reactive laser ablation deposition of CN films  

Microsoft Academic Search

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

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

1996-01-01

136

Measurement and analysis of the pure rotational spectra of tin monochloride, SnCl, using laser ablation equipped chirped pulse and cavity Fourier transform microwave spectroscopy  

NASA Astrophysics Data System (ADS)

The pure rotational spectrum of tin monochloride, SnCl, has been measured and analyzed using chirped pulse and cavity Fourier transform microwave spectrometers equipped with a laser ablation source. SnCl, in its X2? electronic state, has been measured in the 8-17 GHz region. Rotational constants, centrifugal distortion constants, ?-doubling constants, magnetic hyperfine constants, and nuclear electric quadrupole coupling constants for multiple isotopologues have been determined and are reported. The bond length, nuclear magnetic and quadrupole constants have been analyzed and compared against the family of tetral halides. Analysis of the bond length and hyperfine interactions point to a Sn-Cl single bond which is largely ionic in nature.

Grubbs, G. S.; Frohman, Daniel J.; Novick, Stewart E.; Cooke, S. A.

2012-10-01

137

Investigating Age Resolution in Laser Ablation Geochronology  

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

138

Optimization of laser ablation technique for deposited layer removal on carbon plasma facing components  

NASA Astrophysics Data System (ADS)

A laser ablation technique has been adapted for removal of the deposited layers on carbon plasma facing components from Tore Supra. This paper describes in detail the experiments performed to adjust the scan parameters and optimize the laser ablation technique. The goal was to reduce the process duration in order to be able to treat large surfaces. To remove layers up to 50 ?m thick, with an Ytterbium fiber laser of 1 mJ, the process duration limit is 20 h/m2. The conditions to reach 1 h/m2 are presented. Confocal Microscopy (CM) as well as Nuclear Reaction Analysis (NRA) and Thermal Desorption Spectroscopy (TDS), were used to assess the thickness of the layers removed and the Deuterium content before and after ablation. The efficiency of the laser ablation technique to remove the D content is established.

Roche, H.; Courtois, X.; Delaporte, Ph.; Dittmar, T.; Farcage, D.; Gauthier, E.; Hernandez, C.; Languille, P.; Loarer, T.; Mercadier, L.; Naiim Habib, M.; Pascal, J.-Y.; Pocheau, C.; Semerok, A.; Tsitrone, E.; Vignal, N.; Grisolia, C.

2011-08-01

139

Inertial effects in laser-drive ablation  

NASA Astrophysics Data System (ADS)

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

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

1983-07-01

140

Inertial effects in laser-driven ablation  

SciTech Connect

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

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

1983-07-15

141

Influence of nonuniform laser intensities on ablatively accelerated targets  

Microsoft Academic Search

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

Mark Emery; Joseph Orens; John Gardner; Jay Boris

1982-01-01

142

Measurement of Er:YAG laser ablation plume dynamics  

Microsoft Academic Search

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

J. T. Walsh; T. F. Deutsch

1991-01-01

143

Spectroscopic characterization of laser ablation brass plasma  

SciTech Connect

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated.

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

2008-11-15

144

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

145

Nanosecond laser ablation for pulsed laser deposition of yttria  

NASA Astrophysics Data System (ADS)

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

Sinha, Sucharita

2013-04-01

146

Calcified lesion modeling for excimer laser ablation  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

147

Pulsed holmium laser ablation of cardiac valves  

SciTech Connect

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

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

1989-01-01

148

Dynamics of laser ablation of biological tissues  

NASA Astrophysics Data System (ADS)

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

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

1993-10-01

149

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser  

PubMed Central

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

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

2011-01-01

150

Influence of the ablation threshold fluence on laser-driven acceleration  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

151

Numerical Model of Laser Ablation and Plasma Expansion for Ultrashort Laser Pulses  

NASA Astrophysics Data System (ADS)

Laser induced plasma spectroscopy (LIPS) is a promising technique for the chemical analysis of materials, which receives presently much attention. The technique is based on the measurement of lines intensities of the different chemical elements heated by the surrounding plasma. We have developed a one-dimensional Lagrangian fluid model to improve our understanding of the various processes involved in LIPS, namely: of laser ablation, of the subsequent plasma expansion, and of the ambient gas shock wave dynamics, which is strongly coupled to the plasma. The calculated ablation depth and the ablation threshold fluence for simple metals are in agreement with experiments (i.e., less than 1 J/cm2 for the threshold fluence). The model also shows a stage of explosive boiling leading to the ejection of high-density fluid agglomerations. In the case of aluminum, for a fluence of the order of 10 J/cm_2, the model indicates that the expansion of the ablated plasma is generally limited to a few mm and has practically stopped after about 10 microseconds. At this time, the axial distribution of the ablated matter is not at all homogeneous. The temperature can vary from ~0.1 eV to ~1 eV while the gas particle density can vary from ~10^18 cm-3 to ~10^19 cm-3.

Laville, Stéphane; Vidal, Frangois; Chaker, Mohamed; Barthilemy, Olivier; Johnston, Tudor Wyatt; Le Drogoff, Boris; Margot, Jo'"Elle; Sabsabi, Mohamad

2000-10-01

152

Internal Explosion in Laser Ablation of Superconducting Targets.  

National Technical Information Service (NTIS)

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

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

1992-01-01

153

Study of Particle Generation During Laser Ablation with Applications.  

National Technical Information Service (NTIS)

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

C. Liu

2005-01-01

154

Critical-Point Phase Separation in Laser Ablation of Conductors  

NASA Astrophysics Data System (ADS)

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

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

2001-03-01

155

Mechanistic studies of resonant infrared laser ablation of polystyrene  

Microsoft Academic Search

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

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

2009-01-01

156

Antibacterial effects of laser ablated Ni nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

157

Characterization of water contribution to excimer laser ablation of collagen  

Microsoft Academic Search

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

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

2001-01-01

158

Advantages of dual-laser ablation in the growth of multicomponent thin films  

NASA Astrophysics Data System (ADS)

We report the use of a dual-laser deposition process to grow stoichiometric films of the piezoelectric material PbZr0.52Ti0.48O3 (PZT) and the thermoelectric material Ba8Ga16Ge30. High volatility of Pb and Ba in these materials leads to non-stoichiometric growth in conventional PLD processes. Dual-laser ablation process preserves the Pb and Ba stoichiometry while significantly reducing the thickness variation and particulate density on the deposited films. This lead to the growth of smooth uniform films with enhanced ferroelectric and electrical properties. The dual-laser ablation combines the pulses of a KrF excimer laser (248 nm wavelength, 30 ns pulse width) and a CO2 laser (10.6 ?m wavelength, 250 ns pulse width) where the beams are spatially overlapped on the ablation target and temporally delayed. At an optimum delay that is dependent on the physical properties of the material, CO2 pulse energy is coupled into the plume, generating a high temperature plasma (>25,000K). Laser-target interaction studies have shown the evaporation to be stoichiometric. Emission spectroscopy studies have shown ten-fold increase in emission intensities in dual-laser ablation while time-gated 2D ICCD imaging studies revealed the plume expansion to be stoichiometric over a large cone-angle of the plume under these conditions. Time-of-flight investigations in concert with hydrodynamic modeling provided a clear understanding of the mechanism of dual-laser ablation. Furthermore, plasma generated in the process is highly ionized (>75%) leading to films with high density and crystallinity. This paper will show the enhancement in properties attainable by the dual-laser ablation process in comparison to the single laser ablation.

Mukherjee, Devajyoti; Hyde, Robert; Mukherjee, Pritish; Witanachchi, Sarath

2012-07-01

159

Optical Thomson scatter from a laser-ablated magnesium plume  

SciTech Connect

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

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

2009-10-15

160

Laser ablation of aluminum from normal evaporation to phase explosion  

SciTech Connect

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

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

2009-05-15

161

Nonlinear-optical diagnostics for laser ablation and photo-heating of biotissue  

NASA Astrophysics Data System (ADS)

Tissue nonlinear spectroscopy has been investigated as a potential method for monitoring the laser photo-heating and laser ablation of biological tissues samples. The nonlinear optical phenomenon of the second harmonic generation (SHG) for femtosecond-picosecond duration laser beam pulses passing through collagen containing a layer of biotissue was used to monitor the photothermal processes induced by laser irradiation. The samples of biotissues were photo-heated by CW Nd:YAG laser. A picosecond Nd:YAG beam with 1064 nm and pulse duration ?imp = 33 ps was used for probing. After the laser heating of fasciae and tendon samples, the SHG radiation decreased six times in the area of irradiation. The laser ablation of skin samples was performed with a CW Nd:YAG laser at the power of 2 W. As a result of laser ablation the SHG nonlinear signal increased by a factor of 2. The results demonstrate, that the SHG nonlinear phenomenon enables real-time monitoring of photo-heating and ablation processes of biological tissue in novel laser surgical procedures.

Lalayan, A. A.

2005-07-01

162

Laser ablated Fe 100? x Pd x and Fe 100? x Mn x thin films ( x=20 and 50)  

Microsoft Academic Search

Thin films (50nm) of Fe100?xPdx and Fe100?xMnx (x=20 and 50) were deposited by laser ablation on a Si wafer and studied by X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS). In all cases, the XRD patterns of the target surface before and after ablation show a congruent transfer of ablated material. For the Fe80Pd20 thin film, XRD spectra show

Monica Sorescu; L. Diamandescu; A. Grabias

2006-01-01

163

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

164

Nanosecond pulsed laser ablation of silicon in liquids  

Microsoft Academic Search

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

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

2009-01-01

165

Laser ionization mass spectroscopy  

NASA Astrophysics Data System (ADS)

Laser Ionization Mass Spectroscopy (LIMS) is a simple technique with several advantages and disadvantages over standard mass spectroscopy techniques. The LIMS technique uses a laser to vaporize a small portion of a sample. The vapor from the sample consists of a mixture of charged and neutral atoms or fragments. Using electrostatic grids, the ions (positive or negative) are given a known amount of kinetic energy and sent down a time-of-flight tube. The time it takes the ions to travel down the flight tube is recorded. Knowing the ions' energy, the length of the flight tube, and the time it takes the ions to travel that distance, the masses of the ions can be calculated. The instrument used is a LIMA 3 made by Cambridge Mass Spectrometry. It has a Quanta Ray DCR-11 Nd:YAG laser, which was frequency-quadrupled to 266 nm. The laser spot size is typically between 2 and 5 microns in diameter and the pulse width is between 5 and 10 nanoseconds. The energy of the laser is continually variable between 0.1 and 3.0 millijoules. The detector is a 17-stage venetian-blind multiplier made by Thorn EMI. The analysis is carried out under vacuum, usually between 10(exp -8) and 10(exp -9) Torr. The LIMA 3 has several useful features such as: a He-Ne pilot laser used to target the Nd:YAG laser; a microscope (which is used to view the sample through the laser optics); and a precision sample stage for accurate sample alignment.

Bernardez, Luis J., III; Siekhaus, W. J.

1989-10-01

166

Planning and simulation of microsurgical laser bone ablation  

Microsoft Academic Search

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

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

2010-01-01

167

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

168

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

169

Momentum coupling efficiency of laser ablation for space debris removal  

Microsoft Academic Search

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

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

2000-01-01

170

The impact of laser ablation on optical soft tissue differentiation for tissue specific laser surgery-an experimental ex vivo study  

PubMed Central

Background Optical diffuse reflectance can remotely differentiate various bio tissues. To implement this technique in an optical feedback system to guide laser surgery in a tissue-specific way, the alteration of optical tissue properties by laser ablation has to be taken into account. It was the aim of this study to evaluate the general feasibility of optical soft tissue differentiation by diffuse reflectance spectroscopy under the influence of laser ablation, comparing the tissue differentiation results before and after laser intervention. Methods A total of 70 ex vivo tissue samples (5 tissue types) were taken from 14 bisected pig heads. Diffuse reflectance spectra were recorded before and after Er:YAG-laser ablation. The spectra were analyzed and differentiated using principal component analysis (PCA), followed by linear discriminant analysis (LDA). To assess the potential of tissue differentiation, area under the curve (AUC), sensitivity and specificity was computed for each pair of tissue types before and after laser ablation, and compared to each other. Results Optical tissue differentiation showed good results before laser exposure (total classification error 13.51%). However, the tissue pair nerve and fat yielded lower AUC results of only 0.75. After laser ablation slightly reduced differentiation results were found with a total classification error of 16.83%. The tissue pair nerve and fat showed enhanced differentiation (AUC: 0.85). Laser ablation reduced the sensitivity in 50% and specificity in 80% of the cases of tissue pair comparison. The sensitivity of nerve–fat differentiation was enhanced by 35%. Conclusions The observed results show the general feasibility of tissue differentiation by diffuse reflectance spectroscopy even under conditions of tissue alteration by laser ablation. The contrast enhancement for the differentiation between nerve and fat tissue after ablation is assumed to be due to laser removal of the surrounding lipid-rich nerve sheath. The results create the basis for a guidance system to control laser ablation in a tissue-specific way.

2012-01-01

171

Micro-Crater Laser Induced Breakdown Spectroscopy-an Analytical approach in metals samples  

Microsoft Academic Search

The laser ablation has been increasing its popularity like as technique of chemical analysis. This is due to its great potentiality in the analysis of solid samples. On the way to contributing to the development of the technique, we in this work studied the laser induced breakdown spectroscopy (LIBS) in conditions of micro ablation for future studies of coverings and

Vincent Piscitelli; Jhanis Gonzalez; Xianglei Mao; Alberto Fernandez; Richard Russo

2008-01-01

172

Pulse laser ablation at water–air interface  

Microsoft Academic Search

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

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

2010-01-01

173

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

174

Application of Laser Ablation Processing in Electric Power System Industries  

NASA Astrophysics Data System (ADS)

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

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

175

Femtosecond Laser Ablation Regimes in a Single-Crystal Superalloy  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

177

Tailored ablation processing of advanced biomedical hydroxyapatite by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

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

Ozono, K.; Obara, M.

178

Investigations on laser hard tissue ablation under various environments.  

PubMed

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

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

2008-06-03

179

Investigations on laser hard tissue ablation under various environments  

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

180

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

Microsoft Academic Search

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

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

2004-01-01

181

Selective photothermal ablation of tissue with a fiber-delivered Er:YAG laser  

NASA Astrophysics Data System (ADS)

The feasibility of using laser-induced photoemission signals to distinguish between hard and soft biological tissues during photothermal ablation with a pulsed Er:YAG laser has been investigated. Time-resolved emission spectroscopy indicated a threshold fluence of approximately 35 J/cm2 to regularly initiate photoemission from dental enamel, while no emission was detected from porcine muscle tissue with incident laser fluences of up to approximately 140 J/cm2. The delay time of an emission signal with respect to the incident, ablative Er:YAG laser pulse was found to decrease from approximately 150 microseconds near the emission threshold fluence to approximately 60 microseconds at the highest fluence level used. Optical multichannel analyzer spectroscopy of Er:YAG irradiated enamel demonstrated that photoemissions typically consisted of a broad, continuous background in the visible region, with superimposed peaks arising from the presence of elements including calcium, characteristic of plasma emission either from the sample surface or emission plume.

Pierce, Mark C.; Dickinson, Mark R.; Devlin, Hugh

1999-06-01

182

Amalgam ablation with the Er:YAG laser  

NASA Astrophysics Data System (ADS)

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

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

1995-04-01

183

Picosecond laser ablation of nickel-based superalloy C263  

Microsoft Academic Search

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

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

2010-01-01

184

Dynamics of Laser-Driven Ablatively Accelerated Targets  

Microsoft Academic Search

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

Jacob Grun

1981-01-01

185

Dynamics of laser driven, ablatively accelerated targets. Memorandum report  

Microsoft Academic Search

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

Grun

1981-01-01

186

A prototype transition-metal olefin complex C2H4...AgCl synthesised by laser ablation and characterised by rotational spectroscopy and ab initio methods  

NASA Astrophysics Data System (ADS)

C2H4...Ag-Cl has been synthesised in the gas phase in a pulsed-jet, Fourier-transform microwave spectrometer by the reaction of laser-ablated metallic silver with carbon tetrachloride to give AgCl, which subsequently reacts with ethene to give the complex. The ground-state rotational spectra of six isotopologues (C2H4...107Ag35Cl, C2H4...109Ag35Cl, C2H4...107Ag37Cl, C2H4...109Ag37Cl, 13C2H4...107Ag35Cl, and 13C2H4...109Ag35Cl) were recorded and analysed to give rotational constants A0, B0, and C0, centrifugal distortion constants ?J and ?JK, and Cl nuclear quadrupole coupling constants ?aa(Cl) and ?bb(Cl) - ?cc(Cl). These spectroscopic constants were interpreted in terms of a geometry for C2H4...Ag-Cl of C2V symmetry in which the AgCl molecule lies along the C2 axis of ethene that is perpendicular to the C2H4 plane. The Ag atom forms a bond to the midpoint (*) of the ethene ? bond. A partial rs-geometry and a r0-geometry were determined, with the values r(*...Ag) = 2.1719(9) A?, r(C-C) = 1.3518(4) A?, and r(Ag-Cl) = 2.2724(8) A? obtained in the latter case. The C-C bond lengthens on formation of the complex. Detailed ab initio calculations carried out at the CCSD(T)/cc-pVQZ level of theory give results in good agreement with experiment and also reveal that the ethene molecule undergoes a small angular distortion. The distortion is such that the four H atoms move in a direction away from Ag but remain coplanar. The two C atoms are no longer contained in this plane, however. The electric charge redistribution when C2H4...Ag-Cl is formed and the strength of the ?...Ag bond are discussed.

Stephens, Susanna L.; Tew, David P.; Mikhailov, Victor A.; Walker, Nicholas R.; Legon, Anthony C.

2011-07-01

187

Pulsed Tm:YAG laser ablation of knee joint tissues  

NASA Astrophysics Data System (ADS)

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

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

1992-06-01

188

Laser mass spectrometric studies of high temperature superconductor ablation  

SciTech Connect

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

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

1990-01-01

189

Simulation of cluster formation in laser-ablated silicon plumes  

Microsoft Academic Search

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

Sushmita R. Franklin; R. K. Thareja

2005-01-01

190

Direct Drive Beryllium Ablator Capsules for the Omega Laser  

Microsoft Academic Search

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

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

2001-01-01

191

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

192

Two-phase zirconium boride thin film obtained by ultra-short pulsed laser ablation of a ZrB12 target  

NASA Astrophysics Data System (ADS)

Two-phase zirconium boride thin films have been obtained by ultra-short pulsed laser ablation (PLA) of a zirconium dodecaboride (ZrB12) target performed in vacuum. The ablation source was a frequency doubled (? = 527 nm) Nd:glass laser with a pulse duration of 250 fs. Laser induced plasma has been studied by ICCD imaging and time and space resolved optical emission spectroscopy (OES), whereas the deposited films have been characterized by atomic force microscopy, scanning electron microscopy, X-Ray diffraction and micro-Raman spectroscopy. The film morphology and composition have been interpreted on the basis of the laser ablation mechanism.

De Bonis, A.; Santagata, A.; Rau, J. V.; Latini, A.; Mori, T.; Medici, L.; Teghil, R.

2013-10-01

193

Properties of plasmas produced by short double pulse laser ablation of metals  

NASA Astrophysics Data System (ADS)

We investigate the composition of plasmas produced by laser ablation of metals with two time-delayed short laser pulses using fast imaging and time- and space-resolved optical emission spectroscopy. The ablated material is deposited on mica substrates and analyzed by atomic force microscopy. The laser-produced craters are inspected by optical microscopy to evaluate the ablated material quantity. It is shown that the fraction of nanoparticles in the ablation plume is strongly altered when a second laser pulse of sufficiently large delay is applied. Comparing the results obtained for different metals, we observe a significant nanoparticle reduction for interpulse delays of the order of the characteristic time of electron-lattice thermalization. More detailed analyses show that the plume changes occur on two different characteristic times, indicating two different mechanisms at its origin. Here, we discuss the involved processes and we propose a simple and efficient technique for the measurement of electron-lattice thermalization times based on plume observations during double pulse laser ablation.

Hermann, J.; Mercadier, L.; Axente, E.; Noël, S.

2012-11-01

194

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

196

Cancer Diagnosis by Laser Spectroscopy.  

National Technical Information Service (NTIS)

Significant progress has been achieved to distinguish between cancerous and normal human breast and lung tissues by laser fluorescence spectroscopy. Several spectroscopic methods, such as pulse and CW laser fluorescence spectra, excitation spectra, and pi...

A. Pradhan G. C. Tang J. Chen R. R. Alfano W. Sha

1989-01-01

197

Formation of nanostructures upon laser ablation of silver in liquids  

SciTech Connect

The formation of a dense array of nanospikes is studied upon ablation of a silver target immersed into water or ethanol by 350-ps pulses from a neodymium laser. The average height of nanospikes is 50 nm and their density amounts to 10{sup 10}cm{sup -2}. The irradiated surface is studied by using reflection spectroscopy in the 200-600-nm range and an atomic force microscope. Small lateral dimensions of nanospikes confine plasmon oscillations of electrons, which is manifested in the colouring of the irradiated surface. The plasmon resonance of nanospikes is observed at 380 nm and shifts to the visible region upon oxidation in air. The initial spectrum of nanospikes is recovered after processing of their oxidised surface in an aqueous solution of ammonium. The use of nanospikes for observing surface enhanced Raman scattering is discussed. (nanostructures)

Zavedeev, E V; Petrovskaya, A V; Simakin, Aleksandr V; Shafeev, Georgii A [Wave Research Centre, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2006-10-31

198

Laser tattoo removal with preceding ablative fractional treatment  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

199

A Miniaturized Laser Ablation Mass Spectrometer for Space Research  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

200

Growth of multilayered epitaxial films by pulsed excimer laser ablation  

SciTech Connect

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

Lowndes, D.H.

1993-06-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

202

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

Microsoft Academic Search

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

Roger Alan Lindley

1993-01-01

203

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

204

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

205

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

206

Analyte response in laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

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

Zhongke Wang; Bodo Hattendorf; Detlef Günther

2006-01-01

207

A review of Thulium fiber laser ablation of kidney stones  

Microsoft Academic Search

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

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

2011-01-01

208

SIMS study of plumes generated from laser ablation of polymers  

Microsoft Academic Search

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

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

2004-01-01

209

Two-Dimensional Effects in Laser Ablation of Carbon  

Microsoft Academic Search

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

Michael Shusser

2009-01-01

210

Time resolved study of simulated volcanic lightning by laser induced plasma in a plume of ablated basalt  

Microsoft Academic Search

Lightning activity is typically generated by explosive volcanic activity. In this work we report an experimental simulation of a volcanic lightning by focusing into a basaltic rock the emission of a pulsed Nd: YAG laser in air at atmospheric pressure (laser ablation). The temporal evolution of air breakdown in an ash plume was studied by emission spectroscopy and shadowgraphy. The

Hugo Sobral; Roberto Sanginés de Castro; Mayo Villagrán-Muniz; Rafael Navarro-González

2004-01-01

211

High Current Cathodes Fabricated by KrF Laser Ablation  

SciTech Connect

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

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

2010-10-08

212

Will nonablative rejuvenation replace ablative lasers? Facts and controversies.  

PubMed

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

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

213

Porcine cortical bone ablation by ultrashort pulsed laser irradiation  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

214

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

215

Modification of polyimide wetting properties by laser ablated conical microstructures  

NASA Astrophysics Data System (ADS)

Laser texturing of Kapton® HN polyimide was performed by low-fluence ablation using a pulsed, frequency tripled (349 nm) Nd:YLF laser. The laser was scanned in two dimensions in order to generate texture over a large area. The laser overlap percentage and fluence were varied and the resulting texture was studied. The texture features were inspected by electron microscopy and energy dispersive X-Ray spectroscopy (EDS), while the static contact angle of de-ionized water was measured by a contact angle goniometer. Rounded bump features were formed at all fluences, which decreased in areal density with fluence and number of laser pulses. Conical microstructures or "cones" were also formed at most fluences. Cones were larger than the bumps and thus had lower areal density, which increased as a function of the number of laser pulses. The polyimide was hydrophilic before texturing, with a contact angle of approximately 76°. For most of the experimental conditions the contact angle increased as a result of texturing, with the contact angle exceeding 90° for some textured surfaces, and reaching values as high as 118°. In general, the surfaces with significant increases in contact angle had high density of texture features, either bumps or cones. The surfaces that experienced a decrease in contact angle generally had low density of texture features. The increase in contact angle from a wetting (? < 90°) to a nonwetting surface (? > 90°) cannot be explained by texturing alone. EDS measurements indicate that textured regions had higher carbon content than the untextured regions due to depletion of oxygen species. The increase in carbon content relative to the oxygen content increased the native contact angle of the surface, causing the transition from hydrophilic to hydrophobic behavior. The contact angle of a textured surface increased as the relative spacing of features (diameter to spacing) decreased.

Least, Brandon T.; Willis, David A.

2013-05-01

216

Investigation of plumes produced by material ablation with two time-delayed femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

We experimentally investigated and herewith reported the results of laser ablation of copper and gold with two time-delayed femtosecond laser pulses at 800 nm in vacuum. The ablation plume dynamic was monitored by fast plume imaging and time- and space-resolved optical emission spectroscopy. Optical microscopy was used to follow the ablation depth as a function of the delay between the two laser pulses. Nanoparticles deposition on mica substrates was analysed by atomic force microscopy. We estimate roughly the plume's atomization degree - that is the mass fraction of atomized material over the total ablated mass - from the relative intensities of radiation emitted from atoms and nanoparticles. It is shown that the atomization degree depends critically on the time delay between both laser pulses and on the characteristic time of electron-lattice relaxation. The increase of the atomization degree is accompanied by the decrease of the ablation depth. Atomic force microscopy measurements confirm the partial atomization of nanoparticles, as the analyses of particle deposition on mica substrates show a large decrease of the number of nanoparticles for large delay between the two pulses.

Noël, S.; Axente, E.; Hermann, J.

2009-09-01

217

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

SciTech Connect

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

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

2006-12-01

218

Moessbauer Study of Iron Films Produced by Laser Ablation  

SciTech Connect

Iron atoms evaporated by laser ablation were deposited on Al substrates and Si substrates. The iron and alloy (Fe-Al and Fe-Si) films thus formed were evaluated using Moessbauer spectroscopy in order to study their magnetic and chemical properties. Neat iron films (thicker than 50 nm) deposited on Al substrates at 10 K were found to have spin orientations parallel to the surface plane. Formation of Fe-Al alloy was observed at the boundary between the Fe-films and the Al substrate, and the composition of the Fe-Al alloy was a function of the Al substrate temperature during the deposition. Doublet absorption of FeAl was observed for the sample formed at 10 K, and distributed magnetic splitting with disordered compositions of Fe-Al alloy was observed for the samples formed at 293 K. When the sample was formed at 573 K, two sets of sextets with sharp absorptions were observed indicating the formation of Fe3Al. The films were also examined using scanning electron microscopy (SEM). Similarly, samples of laser-evaporated iron on Si substrates were studied, and alloys of Fe-Si were found. Fe3Si and FeSi were produced when the laser-deposition was performed on Si substrates at 573 K.

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

2005-04-26

219

Laser ablation of polymethylmethacrylate and polystyrene at 308 nm: Demonstrtion of thermal and photothermal mechanisms by a time-of-flight mass spectroscopic study  

NASA Astrophysics Data System (ADS)

Laser ablation of polymethylmethacrylate and polystyrene films by an excimer laser at 308 nm was studied by detecting the fragments by time-of-flight mass spectroscopy after multiphoton ionization. Neutral fragments ablating from the polymer surface were predominantly monomer and dimer methylmethacrylate and monomer strene, as deduced from the mass spectra. Thus, `unzipping' of these polymers occurs. The dependence of fragment yields on ablating laser fluence and kinetic energy distributions of ablating species demonstrates thermal and photothermal dissociation of these polymers under the experimental conditions.

Tsunekawa, Makoto; Nishio, Satoru; Sato, Hiroyasu

1994-11-01

220

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

221

Improving Consistency in Laser Ablation Geochronology  

NASA Astrophysics Data System (ADS)

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

Horstwood, Matt; Gehrels, George; Bowring, James

2010-07-01

222

Time progression of ultrashort laser ablation in a transparent material  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

223

Forensic comparative glass analysis by laser-induced breakdown spectroscopy  

Microsoft Academic Search

Glass samples of four types commonly encountered in forensic examinations have been analyzed by laser-induced breakdown spectroscopy (LIBS) for the purpose of discriminating between samples originating from different sources. Some of the glass sets were also examined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Refractive index (RI) measurements were also made on all glass samples and the refractive index data

Candice M. Bridge; Joseph Powell; Katie L. Steele; Michael E. Sigman

2007-01-01

224

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

Microsoft Academic Search

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

Daria Riabinina; Mohamed Chaker; Joëlle Margot

2012-01-01

225

Metal ablation by picosecond laser pulses: A hybrid simulation  

Microsoft Academic Search

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

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

2002-01-01

226

Solid material evaporation into an ECR source by laser ablation.  

National Technical Information Service (NTIS)

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

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

1993-01-01

227

UV Laser Ablation of Parylene Films from Gold Substrates.  

National Technical Information Service (NTIS)

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

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

2009-01-01

228

Laser ablation machining of metal\\/polymer composite materials  

Microsoft Academic Search

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

A. Slocombe; L Li

2000-01-01

229

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

230

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

Microsoft Academic Search

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

Majid Vaezzadeh; Mohammadreza Saeidi; Mohsen Zarei

2010-01-01

231

Femtosecond laser near-field ablation from gold nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2006-01-01

232

Production of bundles of single walled nanotubes by a simple laser ablation technique  

NASA Astrophysics Data System (ADS)

High yield single-walled nanotube (SWNT) material has been obtained by using a very simple laser-ablation experimental set-up. It significantly differs from the usually employed ones in three main points: a) Use of a CO2-laser (in continuous wave mode), b) a simple vertical evaporation-chamber with rotating graphite/metal composite rods, and c) the absence of a furnace around the graphite targets. The obtained SWNT material is characterized by electron microscopy (SEM, TEM) and Raman spectroscopy. We show that our simple laser system creates very favorable growth conditions and discuss the importance of certain experimental parameters during the formation of SWNTs.

Maser, W. K.; Muñoz, E.; Benito, A. M.; Martínez, M. T.; de La Fuente, G. F.; Anglaret, E.; Sauvajol, J.-L.

1999-09-01

233

Laser ablative patterning of copoly(imide siloxane)s generating superhydrophobic surfaces.  

PubMed

Low surface energy copoly(imide siloxane)s were generated via condensation polymerization reactions. The generated materials were characterized spectroscopically, thermally, mechanically, and via contact angle goniometry. The decrease in tensile modulus and opaque appearance of copoly(imide siloxane) films indicated phase segregation in the bulk. Preferential surface partitioning of the siloxane moieties was verified by X-ray photoelectron spectroscopy (XPS) and increased advancing water contact angle values (theta(A)). Pristine copoly(imide siloxane) surfaces typically exhibited theta(A) values of 111 degrees and sliding angles from 27 degrees to >60 degrees. The surface properties of these copoly(imide siloxane) films were further altered using laser ablation patterning (frequency-tripled Nd:YAG laser, 355 nm). Laser-etched square pillar arrays (25 microm pillars with 25 microm interspaces) changed theta(A) by up to 64 degrees. Theta(A) values approaching 175 degrees and sliding angles from 1 degree to 15 degrees were observed. ATR-IR spectroscopy and XPS indicated polymer chain scission reactions occurred as a result of laser ablation. Initial particle adhesion studies revealed that the copoly(imide siloxane)s outperformed the corresponding homopolyimides and that laser ablation patterning further enhanced this result. PMID:20446721

Wohl, Christopher J; Belcher, Marcus A; Chen, Lillian; Connell, John W

2010-07-01

234

Raman mapping of laser-induced changes and ablation of InAs nanowires  

NASA Astrophysics Data System (ADS)

Indium arsenic (InAs) nanowires were irradiated with a focused laser beam, followed by in situ Raman spectroscopy mapping and scanning electron microscopy imaging to investigate the changes of the nanowires due to laser irradiation. It was found that laser irradiation with the power intensity above a certain threshold causes arsenic (As) atoms to disintegrate from InAs and accumulate on the surface of the nanowire; the accumulated As atoms evaporate under the continued laser irradiation. This process reduces the As content in the nanowire. The reduction of As content, in turn, lowers the melting temperature of the nanowire locally and facilitates laser ablation, which eventually fractures the nanowire. The laser irradiation induced changes of the InAs nanowires are attributed to the local temperature rises due to the irradiation, as confirmed by the Raman peak shifts. The results from this work show that in situ Raman spectroscopy mapping can provide detailed information about the entire process of laser-induced change and ablation of InAs nanowires and has the potential to become a powerful tool for the characterization of laser modification of nanowires and other nanometer-sized objects.

He, Jiayu; Chen, Pingping; Lu, Wei; Dai, Ning; Zhu, Da-Ming

2013-08-01

235

In vitro bioactivity of laser ablation pseudowollastonite coating.  

PubMed

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

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

2004-05-01

236

Generation of low work function, stable compound thin films by laser ablation  

DOEpatents

Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

Dinh, Long N. (Concord, CA); McLean, II, William (Oakland, CA); Balooch, Mehdi (Berkeley, CA); Fehring, Jr., Edward J. (Dublin, CA); Schildbach, Marcus A. (Livermore, CA)

2001-01-01

237

Rutile microtubes assembly from nanostructures obtained by ultra-short laser ablation of titanium in liquid  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of a titanium target in water was performed by an ultra-short laser source (Ti-sapphire, ? = 800 nm, 1 kHz, 100 fs). The obtained structures were characterized by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy and X-ray diffraction, revealing the presence of non-stoichiometric titanium oxide nanoparticles with a certain amount of crystalline rutile phase. Upon remaining in water the ablated species, the formation of a lamellar phase has been observed. This lamellar phase rolls up to microtubes by remaining in water for a month, through a self-assembling process. The formed microtubes, with an inner diameter of about 2 ?m and an outer diameter of 4 ?m are characterized by a smooth interior surface and aggregation of nanoparticles on the outer surface.

De Bonis, A.; Galasso, A.; Ibris, N.; Laurita, A.; Santagata, A.; Teghil, R.

2013-03-01

238

Results from the numerical modelling (for various laser pulsewidths) of laser-induced ablation and the subsequent plasma expansion  

NASA Astrophysics Data System (ADS)

To study Laser Induced Plasma Spectroscopy (LIPS) for quantitative analysis of materials, we have developed a self-consistent one-dimensional Lagrangian fluid model using a fractional solid-angle spherical geometry. We have modeled both the (i) laser ablation of an aluminum target and (ii) the subsequent plasma expansion in ambient air. Various laser fluences and several pulse durations (from femtoseconds to nanoseconds) were considered. The calculated ablation depth and the ablation threshold fluence are in good agreement with experiments. The integrated absorption coefficient in aluminum for the laser pulse is constant for pulsewidths of 10 picoseconds or less and is a maximum for pulsewidth of a few hundred picoseconds. The greatest ablation efficiency is obtained for pulsewidths less than picoseconds, in agreement with experiments. The model also shows that the separation of the ablated material occurs via the unstable Van Der Waals pressure instability and is accompanied by the formation of droplets ejected from the target. The model indicates that the ablated plasma in air expands to a distance of a few millimetres and stops expanding after about 10 microseconds. The axial profiles of temperature and density are strongly inhomogeneous and the maximum radiation emission occurs in the outer region of the plasma. The model also shows that, at late times, the spatially integrated values of temperature and electron density do not depend on the laser pulse duration for a given fluence, and this is also in agreement with experiments. In addition, experimental results are in reasonable agreement with the condition of local thermodynamic equilibrium, which is an important assumption in the model.

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

2001-10-01

239

Mechanism of Resonant Mid-Infrared Laser Ablation of Polystyrene  

NASA Astrophysics Data System (ADS)

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

Haglund, Richard; Johnson, Stephen; Bubb, Daniel

2009-03-01

240

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

241

Micro-optic fabrication using laser ablation process  

Microsoft Academic Search

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

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

2002-01-01

242

Diagnostics of laser ablated plasmas using fast photography  

NASA Astrophysics Data System (ADS)

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

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

1999-02-01

243

Optical emission and mass spectrometric characterization of laser ablation process of Ca, Mg, and Ba at 1064 nm  

SciTech Connect

A systematic experimental study of the laser ablation of three alkaline-earth metals (Ca, Mg, and Ba) was carried out to understand the ablation processes of the metals. In this work the infrared laser ablation of alkaline-earth metals was studied by mass spectrometry together with the optical emission spectroscopy of the species generated in the ablation process. The analysis and modeling of the results were done using a heuristic equation that includes the Arrhenius, the screening, and the lineal regions that describe the three different regimes usually observed as a function of the laser fluence. We intend to prove that this equation depends on a fit surface parameter that includes the roughness surface, and it allows us to determine a critical fluence that can be related to the physical properties of the metal target.

Cabanillas-Vidosa, Ivan; Rinaldi, Carlos A.; Ferrero, Juan C. [Centro Laser de Ciencias Moleculares, INFIQC, Departamento de Fisicoquimica Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, 5000 Cordoba (Argentina)

2007-07-01

244

Molecular dynamics simulations studies of laser ablation in metals  

SciTech Connect

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

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

2012-07-30

245

Modeling and computer simulation of pulsed-laser-induced ablation  

NASA Astrophysics Data System (ADS)

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

Tosto, S.

246

Novel CO2 laser system for hard tissue ablation  

Microsoft Academic Search

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

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

1994-01-01

247

Mechanical stress power measurements during high-power laser ablation  

Microsoft Academic Search

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

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

1996-01-01

248

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

249

Multi-wavelength enhancement of silicon Raman scattering by nanoscale laser surface ablation  

NASA Astrophysics Data System (ADS)

In this paper, we produce nanoholes on a silicon surface by laser ablation. Those nanoholes lead to a yield enhancement of light–matter interaction. Performing Raman spectroscopy on silicon, an enhancement of its main Raman mode is observed: it is twice higher with the nanoholes compared to a flat surface. Such a feature appears whatever the excitation wavelength (488, 514.5 and 632.8 nm) and the laser power, revealing a broad band light–matter interaction enhancement. In addition, no change in the position and shape of the main Raman mode of silicon is observed, suggesting that no structural damages are induced by laser ablation. These results clearly demonstrate the potentiality of such nanostructures for the further development of silicon photonics.

Merlen, A.; Sangar, A.; Torchio, P.; Kallepalli, L. N. D.; Grojo, D.; Utéza, O.; Delaporte, P.

2013-11-01

250

Production of copper and brass nanoparticles upon laser ablation in liquids  

SciTech Connect

The production of nanoparticles upon ablation of copper and brass by pulsed radiation from Nd:YAG and copper lasers in water, ethanol, and acetone is studied. The nanoparticles were investigated by the methods of X-ray diffractometry, optical spectroscopy, and transmission electron microscopy. The produced copper and brass nanoparticles were shown to exhibit a plasmon resonance lying in the visible spectral range near 580 and 510 nm. The brass nanoparticles produced by ablation in ethanol have a shell approximately 10-nm thick for an average dimension of 20-30 nm. A chemical modification of ethanol was observed, which manifested itself in the appearance of intense UV absorption bands. Upon laser irradiation of brass nanoparticles in a liquid their absorption spectrum gradually transformed into the spectrum of copper nanoparticles. (interaction of laser radiation with matter)

Kazakevich, Pavel V; Simakin, Aleksandr V; Shafeev, Georgii A [Scientific Center for Wave Studies, A.M.Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Voronov, Valerii V [Laser Materials and Technology Research Center, A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2004-10-31

251

Study on laser atomic spectroscopy.  

National Technical Information Service (NTIS)

Laser atomic spectroscopic study on actinium element has been performed in many areas of spectroscopy. The study on characteristics of atomic vapor has been done for copper atom and the spatial density distribution of copper vapor is measured. This experi...

H. K. Cha K. S. Song D. Y. Jeong J. Lee J. H. Yi

1993-01-01

252

Cancer Diagnosis by Laser Spectroscopy.  

National Technical Information Service (NTIS)

The objective of this project is to investigate and develop novel optically based diagnostics modalities to distinguish between normal and cancerous tissues using various types of steady state and ultrafast laser spectroscopy. Significant work has been co...

R. R. Alfano

1990-01-01

253

Fabrication of iron oxide nanoparticles using laser ablation in liquids  

NASA Astrophysics Data System (ADS)

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

Iwamoto, T.; Ishigaki, T.

2013-06-01

254

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

255

Evolution and imaging of nanoparticles observed in laser ablated carbon plume  

SciTech Connect

We report evidence of nanoparticles formation in laser ablated carbon plasma created by irradiating a graphite target with nanosecond neodymium doped yttrium aluminum garnet laser. The temporal evolution and spatial distribution of C{sub 2} molecules in the plasma is studied using optical emission spectroscopy, dynamic imaging and laser induced fluorescence techniques. The laser induced fluorescence spectrum and imaging of C{sub 2} fluorescence corresponding to transition d {sup 3}PI{sub g}-a {sup 3}PI{sub u} (0, 1) (lambda=563.5 nm) is investigated by probing the expanding plume using a dye laser. The temporal evolution of ground state number density of C{sub 2} shows density varying from 2.6x10{sup 20}/m{sup 3} to 1.2x10{sup 22}/m{sup 3} on varying delay between the ablating and probe pulse from 200 to 600 ns. A peculiar bifurcation of carbon plume into two parts at approx270 ns after the formation of plasma is attributed to recombination of carbon species and formation of nanoparticles. This study may help in quantitatively understanding of formation of carbon molecular species and the nanoparticles produced in laser ablated carbon plume.

Yadav, Dheerendra; Gupta, Varun; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (UP) (India)

2009-09-15

256

Trace Element Microanalysis in Iron Meteorites by Laser Ablation ICPMS.  

PubMed

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

Campbell, A J; Humayun, M

1999-03-01

257

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

258

RODEO MRI guided laser ablation of breast cancer  

NASA Astrophysics Data System (ADS)

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

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

1999-06-01

259

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

260

Plume dynamics of cross-beam pulsed-laser ablation of graphite  

NASA Astrophysics Data System (ADS)

The dynamics of the interaction between two plasmas induced by cross-beam pulsed-laser ablation was analyzed by time resolved optical emission spectroscopy and fast photography. The plasmas were created in vacuum by irradiating two perpendicular graphite targets with an excimer (248 nm) and a Nd:yttrium-aluminum-garnet (1064 nm) laser. In this configuration, a laser is focused onto a target generating a highly directed plume; subsequently, an additional laser produces a second plasma from the perpendicular target which expands through the first plume. Collisional processes cause a reduction of the kinetic energy of the second plume species as compared to the single pulse experiment. For a fixed delay between lasers of 2 ?s, the second plume was divided in two perpendicular directions. The dynamics of this plasma has been compared with laser-induced plume propagation through a background gas in terms of the drag model.

Sánchez Aké, C.; Sanginés de Castro, R.; Sobral, H.; Villagrán-Muniz, M.

2006-09-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2001-06-01

262

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

Microsoft Academic Search

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

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

1999-01-01

263

Hydrodynamic simulations of metal ablation by femtosecond laser irradiation  

SciTech Connect

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

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

2005-04-15

264

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

265

Ionization in vacuum ultraviolet F2 laser ablated polymer plumes  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

266

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

267

Combined optical tweezers and laser dissector for controlled ablation of functional connections in neural networks  

NASA Astrophysics Data System (ADS)

Regeneration of functional connectivity within a neural network after different degrees of lesion is of utmost clinical importance. To test pharmacological approaches aimed at recovering from a total or partial damage of neuronal connections within a circuit, it is necessary to develop a precise method for controlled ablation of neuronal processes. We combined a UV laser microdissector to ablate neural processes in vitro at single neuron and neural network level with infrared holographic optical tweezers to carry out force spectroscopy measurements. Simultaneous force spectroscopy, down to the sub-pico-Newton range, was performed during laser dissection to quantify the tension release in a partially ablated neurite. Therefore, we could control and measure the damage inflicted to an individual neuronal process. To characterize the effect of the inflicted injury on network level, changes in activity of neural subpopulations were monitored with subcellular resolution and overall network activity with high temporal resolution by concurrent calcium imaging and microelectrode array recording. Neuronal connections have been sequentially ablated and the correlated changes in network activity traced and mapped. With this unique combination of electrophysiological and optical tools, neural activity can be studied and quantified in response to controlled injury at the subcellular, cellular, and network level.

Difato, Francesco; Dal Maschio, Marco; Marconi, Emanuele; Ronzitti, Giuseppe; Maccione, Alessandro; Fellin, Tommasso; Berdondini, Luca; Chieregatti, Evelina; Benfenati, Fabio; Blau, Axel

2011-05-01

268

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

269

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

270

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

NASA Astrophysics Data System (ADS)

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

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

1994-06-01

271

Ablation-initiated Isotope-selective Atomic Absorption Spectroscopy of Lanthanide Elements  

NASA Astrophysics Data System (ADS)

For remote isotope analysis of low-decontaminated trans-uranium (TRU) fuel, absorption spectroscopy has been applied to a laser-ablated plume of lanthanide elements. To improve isotopic selectivity and detection sensitivity of the ablated species, various experimental conditions were optimized. Isotope-selective absorption spectra were measured by observing the slow component of the plume produced under low-pressure rare-gas ambient. The measured minimum line width of about 0.9 GHz was close to the Doppler width of the Gd atomic transition at room temperature. The relaxation rate of high-lying metastable state was found to be higher than that of the ground state, which suggests that higher analytical sensitivity can be obtained using low-lying state transition. Under helium gas environment, Doppler splitting was caused from particle motion. This effect was considered for optimization for isotope selection and analysis. Some analytical performances of this method were determined under optimum conditions and were discussed.

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

2009-03-01

272

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors  

SciTech Connect

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

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

2010-10-08

273

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

274

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

275

Dynamics of laser driven, ablatively accelerated targets. Memorandum report  

SciTech Connect

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

Grun, J.

1981-05-08

276

CO2 Laser Ablation Propulsion Area Scaling With Polyoxymethylene Propellant  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

277

Pulsed CO2 laser ablation of graphite and polymers  

NASA Astrophysics Data System (ADS)

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

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

1998-02-01

278

Ablative thresholds in laser cleaning of substrates from particulates  

NASA Astrophysics Data System (ADS)

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

Arnold, N.; Schrems, G.; Bäuerle, D.

279

Production of nanoparticles from natural hydroxylapatite by laser ablation  

PubMed Central

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

2011-01-01

280

Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide  

NASA Astrophysics Data System (ADS)

Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

2012-09-01

281

In situ monitoring of pulsed laser indium–tin-oxide film deposition by optical emission spectroscopy  

Microsoft Academic Search

We performed optical emission spectroscopy to monitor the plasma produced during the ablation of indium–tin-oxide targets under different oxygen pressure conditions using a pulsed UV laser. Molecular bands of InO were identified in the fluorescent spectra produced by pulsed laser ablation. InO line monitoring allowed obtaining the optimal conditions for good-quality ITO film deposition. We demonstrated that it is possible

R. Macaluso; M. Mosca

2001-01-01

282

Infrared Laser Ablation Sample Transfer for MALDI and Electrospray  

NASA Astrophysics Data System (ADS)

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

Park, Sung-Gun; Murray, Kermit King

2011-08-01

283

Comparative study on laser tissue ablation between PV and HPS lasers  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

284

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

NASA Astrophysics Data System (ADS)

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

Zhao, Xin; Shin, Yung C.

2013-10-01

285

Plasma diagnostics during laser ablation in a cavity  

Microsoft Academic Search

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

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

2003-01-01

286

Perfluorocarbon compounds: transmitting liquids for infrared laser tissue ablation  

Microsoft Academic Search

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

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

1996-01-01

287

Controlled Ablation of Microtubules Using a Picosecond Laser  

Microsoft Academic Search

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

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

2004-01-01

288

Laser ablation assisted adhesive bonding of automotive structural composites  

SciTech Connect

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

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

1999-07-03

289

Perfluorocarbon compounds: transmitting liquids for infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

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

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

1996-05-01

290

Thermal Simulation of UV Laser Ablation of Polyimide  

Microsoft Academic Search

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

Peter Gordon; Balint Balogh; Balint Sinkovics

2005-01-01

291

Thermal simulation of UV laser ablation of polyimide  

Microsoft Academic Search

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

Péter Gordon; Bálint Balogh; Bálint Sinkovics

2007-01-01

292

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

NASA Astrophysics Data System (ADS)

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

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

293

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

SciTech Connect

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

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

1999-01-01

294

Characterization of high performance polymers transferred by resonant infrared laser ablation  

NASA Astrophysics Data System (ADS)

A polyamide imide and a polymeric precursor to polyimide have both been successfully transferred using resonant infrared laser ablation. Additionally a random copolymer mixture, possessing structural features common to polyimide and polyamide imide, was readily transferred using resonant infrared laser ablation. The materials are transferred with local structure intact as evidenced by Fourier transform infrared spectroscopy studies. The deposition rates of the polyimide precursor were examined at various wavelengths using a quartz crystal microbalance mounted in the deposition chamber. The effect of target type on deposition rate was also examined using two different 20 wt% polyamide imide solutions in N-methyl pyrrolidinone and dimethyl formamide and a solid pressed pellet target of polyamide imide. Both wavelength and target form were found to have a discernible effect on deposition rate. The deposited material was examined using a combination of profilometry and optical microscopy. The results show highly rough films with large, dark, string-like polymeric moieties on the surface.

Dygert, Nicole L.; Haglund, Richard F., Jr.

2008-03-01

295

INTERACTION OF LASER RADIATION WITH MATTER: Production of copper and brass nanoparticles upon laser ablation in liquids  

NASA Astrophysics Data System (ADS)

The production of nanoparticles upon ablation of copper and brass by pulsed radiation from Nd:YAG and copper lasers in water, ethanol, and acetone is studied. The nanoparticles were investigated by the methods of X-ray diffractometry, optical spectroscopy, and transmission electron microscopy. The produced copper and brass nanoparticles were shown to exhibit a plasmon resonance lying in the visible spectral range near 580 and 510 nm. The brass nanoparticles produced by ablation in ethanol have a shell approximately 10-nm thick for an average dimension of 20-30 nm. A chemical modification of ethanol was observed, which manifested itself in the appearance of intense UV absorption bands. Upon laser irradiation of brass nanoparticles in a liquid their absorption spectrum gradually transformed into the spectrum of copper nanoparticles.

Kazakevich, Pavel V.; Voronov, Valerii V.; Simakin, Aleksandr V.; Shafeev, Georgii A.

2004-10-01

296

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

SciTech Connect

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

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

2004-08-30

297

Pulsed laser ablation plasmas generated in CO2 under high-pressure conditions up to supercritical fluid  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO2 at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

2012-11-01

298

Growth of SiO(x) nanowires by laser ablation.  

PubMed

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

Aharonovich, Igor; Tamir, Shoshana; Lifshitz, Yeshayahu

2008-01-23

299

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

300

308-nm excimer laser ablation of human cartilage  

NASA Astrophysics Data System (ADS)

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

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

1993-07-01

301

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

SciTech Connect

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

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

2008-07-15

302

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

Microsoft Academic Search

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

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

1996-01-01

303

Laser sources for Raman spectroscopy  

NASA Astrophysics Data System (ADS)

While conventional Raman Spectroscopy (RS) has predominately used fixed wavelength cw lasers, advanced Raman spectroscopic techniques such as Stimulated Raman and some types of Raman Imaging typically need pulsed lasers with sufficient energy to induce the Raman process. In addition, pulsed lasers are beneficial for the following Raman techniques: Time Resolved Raman (TRR), Resonance Raman (RR), or non linear Raman techniques, such as Coherent anti-Stokes Raman spectroscopy (CARS). Here the naturally narrower linewidth of a ns pulse width laser is advantageous to a broader linewidth ultrafast pulsed laser. In this paper, we report on the development of a compact, highly efficient, high power solid-state Ti: Sapphire laser ideally suited for many Raman spectroscopic techniques. This laser produces nanosecond pulses at kHz repetition rates with a tunable output wavelength from ~1 micron to ~200 nm and pulse energies up to 1 mJ. The narrow bandwidth of this laser (<0.1cm-1) is ideally suited for applications such as Laser-induced fluorescence (LIF) measurement of OH free-radicals concentrations, atmospheric LIDAR and Raman spectroscopy. New KBBF and RBBF deep ultraviolet (DUV) and vacuum ultraviolet (VUV) crystals are now available that enable direct doubling of the SHG output of these tunable Ti: Sapphire lasers to directly achieve wavelengths as short as 175 nm without the need to generate the 3rd harmonic and utilize frequency mixing. This results in a highly efficient output in the DUV/VUV, enabling improved signal to noise ratios (S/N) in these previously difficult wavelength regions. Photonics Industries has recently achieved a few mW of power at 193nm with such direct doubling crystals.

Kilmer, J.; Iadevaia, A.; Yin, Y.

2011-05-01

304

Structure and magnetic properties of iron oxide films deposited by excimer laser ablation of a metal-containing polymer  

Microsoft Academic Search

The process of depositing iron oxide films on fused quartz substrates via the plume generated by excimer laser ablation of poly(ferric methacrylate), a metal-containing polymer, is reported in this paper. The chemical composition of the deposited films was analyzed by means of X-ray photoelectron spectroscopy and Roman spectroscopy. The results suggest that the deposited films consist of iron-rich Fe3O4 and

Meng Ouyang; Hiroyuki Hiraoka

1997-01-01

305

Infrared laser ablation atmospheric pressure photoionization mass spectrometry.  

PubMed

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

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

2012-01-19

306

Ultraviolet laser ablation of polycarbonate and glass in air  

NASA Astrophysics Data System (ADS)

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

Bormotova, T. A.; Blumenthal, R.

2009-02-01

307

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

Microsoft Academic Search

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

Manuel Caetano; Xianglei Mao; Richard E. Russo

1996-01-01

308

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

Microsoft Academic Search

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

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

1997-01-01

309

Shadowgraphy of pulsed CO2 laser ablation of polymers  

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

310

Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments  

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

311

Ablation of aluminum thin films by ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

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

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

2001-06-01

312

Ablation of aluminum thin films by ultrashort laser pulses  

SciTech Connect

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

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

2001-06-15

313

Ultrafast laser ablation of metal films on flexible substrates  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

314

Pillars formed by laser ablation and modified by wet etching  

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

315

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

PubMed

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

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

2013-03-18

316

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

Microsoft Academic Search

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

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

1996-01-01

317

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

Microsoft Academic Search

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

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

1996-01-01

318

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

319

Silicon and zinc telluride nanoparticles synthesized by low energy density pulsed laser ablation into ambient gases  

SciTech Connect

The size distributions of Si and ZnTe nanoparticles produced by low energy density ArF (193 nm) pulsed laser ablation into ambient gases were measured as a function of the gas pressure, {ital P}, and target-substrate separation, D{sub ts}. For both Si and ZnTe, the largest nanoparticles were found closest to the ablation target, and the mean nanoparticle size {ital decreased} with increasing D{sub ts}. For Si ablation into He, the mean nanoparticle diameter did not increase monotonically with gas pressure but reached a maximum near Pthinsp=thinsp6 Torr. High resolution Z-contrast transmission electron microscopy and energy loss spectroscopy revealed that ZnTe nanoparticles consist of a crystalline core surrounded by an amorphous ZnO shell; growth defects and surface steps are clearly visible in the crystalline core. A pronounced narrowing of the ZnTe nanocrystal size distribution with increasing D{sub ts} also was found. The results demonstrate that the size of laser-ablated nanoparticles can be controlled by varying the molecular weight and pressure of an ambient gas and that nanometer-scale particles can be synthesized. Larger aggregates of both ZnTe and Si having a {open_quotes}flakelike{close_quotes} or {open_quotes}weblike{close_quotes} structure were formed at the higher ambient gas pressures; for ZnTe these appear to be open agglomerates of much smaller ({approximately}10 nm) particles. {copyright} {ital 1999 Materials Research Society.}

Lowndes, D.H.; Rouleau, C.M.; Duscher, G.; Pennycook, S.J. [Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6056 (United States); Thundat, T.G. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6123 (United States); Kenik, E.A. [Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6376 (United States)

1999-02-01

320

Thermal-mechanical modeling of laser ablation hybrid machining  

NASA Astrophysics Data System (ADS)

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

Matin, Mohammad Kaiser

2001-08-01

321

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

322

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

323

Modeling of dynamical processes in laser ablation  

SciTech Connect

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

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

1995-12-31

324

Fourier-transform laser spectroscopy  

NASA Astrophysics Data System (ADS)

The development of microphotonic sensors based on Fourier-transform laser spectroscopy (FT-LS) is discussed. The application demonstrated is for measurement of vapors from the hydrocarbon fuels JP-8, diesel fuel, and gasoline. The two-laser prototype FT-LS sensor used for our research employs distributed-feedback lasers in the near-infrared spectral region (1.3- and 1.7-?m wavelength). An extension of this research to multilaser arrays is discussed. We believe that this is the first measurement of middle-distillate fuel-vapor concentrations using this optical mixing technique.

McNesby, Kevin L.; Miziolek, Andrzej W.

2003-04-01

325

Laser induced breakdown spectroscopy for contamination removal on engine-run thermal barrier coatings  

Microsoft Academic Search

A method for cleaning thermal barrier coatings (TBCs) contaminated during engine operation has been developed using laser ablation. Surface contamination on the turbine blades hinders nondestructive remaining life evaluation using photoluminescence piezospectroscopy (PLPS). Real time monitoring of the removed material is employed to prevent damage to the underlying coating. This method relies on laser induced breakdown spectroscopy (LIBS) to compute

Mark S. Majewski; Colin Kelley; Waled Hassan; William Brindley; Eric H. Jordan; Michael W. Renfro

2011-01-01

326

Ground state C 2 density measurement in carbon plume using laser-induced fluorescence spectroscopy  

Microsoft Academic Search

The temporal evolution and spatial distribution of C2 molecules produced by laser ablation of a graphite target is studied using optical emission spectroscopy, dynamic imaging and laser-induced fluorescence (LIF) investigations. We observe peculiar bifurcation of carbon plume into two parts; stationary component close to the target surface and a component moving away from the target surface which splits further in

Dheerendra Yadav; Varun Gupta; Raj K. Thareja

2009-01-01

327

Emission features of femtosecond laser ablated carbon plasma in ambient helium  

NASA Astrophysics Data System (ADS)

We investigated the optical emission features of plasmas produced by 800 nm, 40 fs ultrafast laser pulses on a carbon target in the presence of ambient helium or nitrogen gases at varied pressures. Fast photography employing intensified charge coupled device, optical emission spectroscopy, and temporally spatially resolved optical time of flight emission spectroscopy were used as diagnostic tools. Spatio-temporal contours of excited neutral, ionic, as well as molecular carbon species in the plume were obtained using time of flight emission spectroscopy. These contours provided detailed account of molecular species evolution and expansion dynamics and indicate that three-body recombination is a major mechanism for carbon dimers generation in ultrafast laser ablation plumes in the presence of ambient gas. A systematic comparison of the emission features from ns and fs laser ablation carbon plumes as well as their expansion in ambient helium is also given. C2 vibrational temperatures were estimated during carbon plasma expansion with lower values in ambient helium compared to nitrogen and showed decreasing values with respect to space and ambient gas pressure.

Al-Shboul, K. F.; Harilal, S. S.; Hassanein, A.

2013-04-01

328

Noble metal nanoparticles produced by nanosecond laser ablation  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

329

Generation of metal-oxide nanoparticles using continuous-wave fibre laser ablation in liquid  

NASA Astrophysics Data System (ADS)

In recent years, laser ablation in liquid has become an increasingly important technique for the fabrication of nanoparticles (NPs). To date, only pulsed lasers have been used. This paper reports our recent studies on the generation of Ti-oxide and Ni-oxide NPs by the ablation of metal targets in aqueous environments using a high-power, high-brightness continuous-wave (cw) fibre laser at a wavelength of 1070 nm. Owing to the high and uniform irradiation, the fibre laser provides an alternative approach for NP generation with well-controlled phase, size and size distribution, along with high production rate. Characterization of the NPs, in terms of morphology, size and size distribution, chemical composition and phase structure, by means of high-resolution transmission electron microscopy (HRTEM), high-angle annular dark field (HAADF) in scanning-transmission (STEM) mode, energy-dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD), has been presented. In addition, limitations of the cw fibre laser process have been discussed in comparison with pulsed laser process.

Liu, Z.; Yuan, Y.; Khan, S.; Abdolvand, A.; Whitehead, D.; Schmidt, M.; Li, L.

2009-05-01

330

The Potential Use of Laser Ablation for Selective Cleaning of Indiana Limestone  

NASA Astrophysics Data System (ADS)

The aim of this investigation and conservation study was to examine and evaluate the laser ablation method as a practical technique for cleaning of Indiana limestone, a calcite-cemented stone widely used in historic structures throughout the United States. To this goal, a thorough petrographic characterization of the samples was performed prior to and following laser cleaning tests by Q-switched and short free running Nd:YAG lasers. The main optimization problem was the amber-gray appearance associated with the laser ablation by Q-switching lasers. Following the evaluation of such a cleaning result, two practicable solutions based on suitable pulse duration or wavelength selections were successfully demonstrated and then compared with different intervention protocols proposed. This chapter will show that through this case study, an understanding of effective uses of cleaning highly weathered Indiana limestone through the use of three types of Q-switched and short free running Nd:YAG lasers can be most effective in the removal from limestone of surface soiling and thick built-up carbon deposits ranging from 0.5 to 1mm in thickness. Case study evaluation methods included petrographic examination of composition, texture, and microstructure using optical microscopy and scanning electron microscopy performed on thin and polished sections of limestone sampled from six areas before and after cleaning. The microscopy studies were supplemented with energy-dispersive X-ray spectroscopy to characterize crystalline phases and track changes in chemistry.

Normandin, K. C.; Powers, L.; Slaton, D.; Scheffler, M. J.

331

An Electron Emission Effect on Dynamics of Laser Ablation  

SciTech Connect

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

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

2004-03-30

332

Excimer Laser Ablation Process of Different Metals  

Microsoft Academic Search

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

M. Kutsuna; T. Ikeda; A. Tsuboi

333

Role of Optical Coherence Tomography on Corneal Surface Laser Ablation  

PubMed Central

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

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

2012-01-01

334

Excimer laser surface ablation: a review of recent literature.  

PubMed

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

O'Brart, David Ps

2013-05-01

335

Doppler Free Laser Spectroscopy  

NSDL National Science Digital Library

In this experiment you will use a technique known as saturation-absorption spectroscopy to study the hyperfine structure (hfs) of rubidium. This particular method is designed to overcome the limitations imposed by the Doppler-broadening of spectral lines while avoiding the need to work at low temperatures.

2012-01-09

336

Simulation of cluster formation in laser-ablated silicon plumes  

SciTech Connect

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

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

2005-06-15

337

Tunable Diode Laser Spectroscopy.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. This thesis presents the results of the first laser study of the 6p_{1/2} to 6p_{3/2} transition in thallium at 1.28 mum. The work includes direct observation of absorption and Faraday rotation spectra and the comparison of these spectra with theoretical predictions. These experiments are the first of a series, the final aim of which is to study and measure the parity violating (PV) optical rotation which is predicted by the Glashow-Weinberg-Salam theory of the electroweak interaction. The impetus to study thallium comes from the high accuracy claimed for the atomic calculations which link the electroweak theory to the magnitude of the optical effect; the rotation at 1.28 ?m is predicted to have a peak value of 1.7 times 10 ^{-7} radians per absorption length of vapour. The laser used in all of the experiments described is an InGaAsP semiconductor laser, which operates on several modes simultaneously. The amplitude noise on an individual mode, coupled with the noise from the germanium photodetectors used, limited the signal-to-noise ratio that could be obtained. It was also observed that the absorption and Faraday rotation effects of the transition produce spectra, the form of which cannot be described correctly without including the particular characteristics of the particular diode laser used. A model for the spectra incorporating the laser characteristics is constructed which accounts for many of the observed features of the data. In particular, the analysis shows that the characteristics of the laser, notably the linewidth of the mode of interest and the satellite modes, which occur on either side of the central mode, vary significantly over the wavelength region of the transition. The analysis is made complicated by this but the values of the atomic and the line broadening parameters which are deduced are consistent with the theoretically predicted values. In a further series of experiments the geometry of the optical polarimeter was varied to optimise the signal -to-noise ratio. A final static resolution of 3 muradians for one absorption length was observed. This is a factor of 20 above the resolution at which we expect to observe PV rotations. Further developments in laser technology at this wavelength coupled with the suggested improvements in the design of the experiment discussed in the thesis should enable the necessary level of resolution to be reached in the near future.

Deeny, J. A.

338

Laser ablation of a silicon target in chloroform: formation of multilayer graphite nanostructures  

NASA Astrophysics Data System (ADS)

With the use of high-resolution transmission electron microscopy, selected area electron diffraction and x-ray photoelectron spectroscopy methods of analysis we show that the laser ablation of a Si target in chloroform (CHCl3) by nanosecond UV pulses (40 ns, 355 nm) results in the formation of about 50-80 nm core-shell nanoparticles with a polycrystalline core composed of small (5-10 nm) Si and SiC mono-crystallites, the core being coated by several layers of carbon with the structure of graphite (the shell). In addition, free carbon multilayer nanostructures (carbon nano-onions) are also found in the suspension. On the basis of a comparison with similar laser ablation experiments implemented in carbon tetrachloride (CCl4), where only bare (uncoated) Si nanoparticles are produced, we suggest that a chemical (solvent decomposition giving rise to highly reactive CH-containing radicals) rather than a physical (solvent atomization followed by carbon nanostructure formation) mechanism is responsible for the formation of graphitic shells. The silicon carbonization process found for the case of laser ablation in chloroform may be promising for silicon surface protection and functionalization.

Abderrafi, Kamal; García-Calzada, Raúl; Sanchez-Royo, Juan F.; Chirvony, Vladimir S.; Agouram, Saïd; Abargues, Rafael; Ibáñez, Rafael; Martínez-Pastor, Juan P.

2013-04-01

339

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

SciTech Connect

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

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

2005-08-15

340

Optoacoustic monitoring of cutting and heating processes during laser ablation  

NASA Astrophysics Data System (ADS)

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

Bay, Erwin; Douplik, Alexandre; Razansky, Daniel

2013-03-01

341

Targets on superhydrophobic surfaces for laser ablation ion sources  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

342

Tissue ablation via optical fibre delivery of UV laser radiation  

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

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

Real time assessment of RF cardiac tissue ablation with optical spectroscopy  

SciTech Connect

An optical spectroscopy approach is demonstrated allowing for critical parameters during RF ablation of cardiac tissue to be evaluated in real time. The method is based on incorporating in a typical ablation catheter transmitting and receiving fibers that terminate at the tip of the catheter. By analyzing the spectral characteristics of the NIR diffusely reflected light, information is obtained on such parameters as, catheter-tissue proximity, lesion formation, depth of penetration of the lesion, formation of char during the ablation, formation of coagulum around the ablation site, differentiation of ablated from healthy tissue, and recognition of micro-bubble formation in the tissue.

Demos, S G; Sharareh, S

2008-03-20

345

Stable isotope laser spectroscopy  

NASA Astrophysics Data System (ADS)

Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.

Becker, J. F.; Yaldaei, Ramil; McKay, Christopher P.

1989-03-01

346

Laser ablated coatings on ceramic fibers for ceramic matrix composites  

Microsoft Academic Search

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

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

1995-01-01

347

In vitro bioactivity of laser ablation pseudowollastonite coating  

Microsoft Academic Search

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

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

2004-01-01

348

Laser reactive ablation deposition of carbon nitride thin films  

Microsoft Academic Search

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

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

1996-01-01

349

Effect of ablation photon energy on the distribution of molecular species in laser-induced plasma from polymer in air  

NASA Astrophysics Data System (ADS)

Distribution of molecular species, C2 and CN, in laser-induced plasma from a polymer target (polyvinyl chloride: PVC) was observed for ablation with 266 nm and 355 nm pulses. The influence of ablation photon energy on the distribution of molecular species in the plasma has been thus studied. Time- and space-resolved emission spectroscopy was used for the observation which led to the determination of emission intensity profiles of C2 molecule and CN radical for different delays after the impact of the laser pulse on the target. The profiles of related elements, C, N, and excitation temperature in the plasma were further determined to correlate with those of molecular emission intensity. Different behaviors were clearly observed between plasmas induced by pulses with the two different wavelengths chosen to be close each other in the near ultraviolet (UV). A closer analysis shows the photon energy corresponding to 266 nm pulse of 4.66 eV is larger than bond energies of all the chemical bonds in the studied polymer, while that of 355 nm radiation of 3.49 eV is smaller than or in the same range of the involved bond energies. Observed different behaviors suggest therefore different ablation mechanisms of polymer by laser radiation, and consequently different channels of molecule formation in the plasma. Observation of the morphology of the craters on the target surface left by laser ablation confirmed further different ablation mechanisms with the two used wavelengths.

Lei, W. Q.; Ma, Q. L.; Motto-Ros, V.; Bai, X. S.; Zheng, L. J.; Zeng, H. P.; Yu, J.

2012-07-01

350

Single-walled carbon nanotubes synthesis: a direct comparison of laser ablation and carbon arc routes.  

PubMed

Carbon arc and chemical vapor deposition are at present the most efficient methods for mass production of single-walled carbon nanotubes. However, laser ablation is renowned for high quality nanotubes with narrow diameter distributions and hence is also of great interest. The aim of this work was to compare both the carbon arc and laser ablation techniques with respect to the quality--and relative yield of the produced SWCNTs. For this comparative study we used Fe as the catalyst, which is known not to be very active in laser ablation. However, we show this is not the case when H2 is included in the reaction. The reactions for both synthesis routes were carried out in a N2-H2 (95-5% vol.) atmosphere. The same homogenous carbon rods with different iron contents, between 1 and 5 at.% were used as the carbon feedstock and catalyst supply in both synthesis routes. Additionally, two types of carbon rods containing 1 at.% Fe with different graphitization degrees were also investigated. In the arc-discharge case, the low-graphitized electrode produced a web-like product rich in SWCNTs, while the high-graphitized carbon rods yielded soot containing carbon-encapsulated iron nanocrystallites, amorphous carbon nanoparticles, and surprisingly a small fraction of SWCNTs. With laser ablation synthesis, the Fe content and the reactor temperature significantly influenced the SWCNTs yield. Carbon arc plasma diagnostics were also performed. By using optical emission and Absorption spectroscopy the plasma temperature, C2 and CN radical content in the arc zone were determined. PMID:19198361

Bystrzejewski, M; Rümmeli, M H; Lange, H; Huczko, A; Baranowski, P; Gemming, T; Pichler, T

2008-11-01

351

Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere  

NASA Astrophysics Data System (ADS)

We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near the laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times <=400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.

Harilal, S. S.; Miloshevsky, G. V.; Diwakar, P. K.; LaHaye, N. L.; Hassanein, A.

2012-08-01

352

Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere  

SciTech Connect

We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near the laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times {<=}400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.

Harilal, S. S.; Miloshevsky, G. V.; Diwakar, P. K.; LaHaye, N. L.; Hassanein, A. [Center for Materials under Extreme Environment, and School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2012-08-15

353

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

354

Laser induced effects on ZnO targets upon ablation at 266 and 308 nm wavelengths  

SciTech Connect

The development of structural changes in ZnO targets, upon laser irradiation at the wavelengths of 266 and 308 nm, is studied by Raman spectroscopy. At the wavelength of 308 nm, oxygen vacancies are found to develop monotonically with increasing laser intensity. At 266 nm, a structural change in the irradiated ZnO targets, possibly related to nanostructuring, is observed above the laser fluence of 0.45 J cm{sup -2}. The different natures of the laser target interaction processes taking place at both wavelengths are investigated through the characterization of the composition and energy distribution of the species ejected in the ablation. The energy of the neutral Zn and Zn{sub 2} present in the ablation at 308 nm shows a smooth dependence on laser fluence which is consistent with the observed smooth development of oxygen vacancies. At 266 nm, the average kinetic energy of the ejected fragments is higher than at 308 nm and changes abruptly with the ablating laser fluence, consistently with the presence of a fluence threshold above which structural transform is observed at this wavelength. The plume shows the same neutral composition (Zn, ZnO, and Zn{sub 2}) at both wavelengths but the dependence on fluence of the ratio of neutral atomic Zn to the dimer Zn{sub 2} shows significant differences. From the latter, different temperature regimes can be inferred in the plume generated at both wavelengths. At 266 nm the cationic composition of the plume is mainly stoichiometric whereas at 308 nm ZnO{sub 2(3)}H{sub 2(1)}{sup +} cations have the highest intensity.

Jadraque, Maria; Martin, Margarita [Instituto de Quimica Fisica 'Rocasolano', C.S.I.C. Serrano 119, 28006 Madrid (Spain); Domingo, Concepcion [Instituto de Estructura de la Materia, C.S.I.C. Serrano 121, 28006 Madrid (Spain)

2008-07-15

355

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

356

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

Microsoft Academic Search

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

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

2004-01-01

357

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

Microsoft Academic Search

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

Mihai Stafe; Constantin Negutu; Ion M. Popescu

2007-01-01

358

Micro-optic fabrication using laser ablation process  

NASA Astrophysics Data System (ADS)

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

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

2002-09-01

359

Mass spectroscopic characterization of yttrium-containing metallofullerene YC82 using resonant laser ablation  

Microsoft Academic Search

In this paper, resonant laser ablation time-of-flight mass spectroscopy (RLA-TOF-MS) has been used to mass spectroscopic characterization of yttrium-containing fullerenes. Solvent soluble, yttrium-containing fullerenes are extracted from yttrium\\/carbon soot produced by the carbon-arc fullerene generation method. The RLA-TOF mass spectra indicate the presence of YC82. The metallofullerences YC60, YC70, Y2C82 and a series of Y2C2n are not observed by RLA-TOF-MS.

Shiliang Wang; Jiahe Tian; Songtao Dai; Dieyan Chen; Chuping Luo; Haisong Tan; Liangbing Gan; Chunhui Huang

1995-01-01

360

Phosphorus doping and hydrogen passivation of donors and defects in silicon nanowires synthesized by laser ablation  

SciTech Connect

Phosphorus (P) doping was performed during the synthesis of silicon nanowires (SiNWs) by laser ablation. At least three types of signals were observed by electron spin resonance (ESR) at 4.2 K. Phosphorus doping into substitutional sites of crystalline Si in SiNWs was demonstrated by the detection of an ESR signal with a g value of 1.998, which corresponds to conduction electrons in crystalline Si, and by an energy-dispersive x-ray spectroscopy spectrum of the P K{alpha} line. The ESR results also revealed the presence of defects. These defects were partially passivated by hydrogen and oxygen atoms.

Fukata, N.; Chen, J.; Sekiguchi, T.; Matsushita, S.; Oshima, T.; Uchida, N.; Murakami, K.; Tsurui, T.; Ito, S. [Advanced Electronic Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2007-04-09

361

Formation of core/shell structured cobalt/carbon nanoparticles by pulsed laser ablation in toluene  

NASA Astrophysics Data System (ADS)

Magnetic cobalt nanoparticles encapsulated in shells of layered structure have been produced by the technique of pulsed laser ablation in toluene. The morphology, microstructure, and magnetic properties of the prepared nanoparticles were characterized by electron microscopy, micro-Raman spectroscopy, and superconducting quantum interference device magnetometry, respectively. The results indicated that the cobalt nanoparticles fabricated are noncrystalline but coated with the graphitic carbon layers. It is believed that the formation of these carbon layers well-protect the cobalt nanoparticles to be oxidized thus maintaining the superparamagnetic property. This is an important feature that makes the cobalt nanoparticles a useful material for medical and many other magnetic based applications.

Kwong, H. Y.; Wong, M. H.; Leung, C. W.; Wong, Y. W.; Wong, K. H.

2010-08-01

362

Biocompatible inorganic fullerene-like molybdenum disulfide nanoparticles produced by pulsed laser ablation in water.  

PubMed

We report on the synthesis of inorganic fullerene-like molybdenum disulfide (MoS(2)) nanoparticles by pulsed laser ablation (PLA) in water. The final products were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and resonance Raman spectroscopy, etc. Cell viability studies show that the as-prepared MoS(2) nanoparticles have good solubility and biocompatibility, which may show a great potential in various biomedical applications. It is shown that the technique of PLA in water also provides a green and convenient method to synthesize novel nanomaterials, especially for biocompatible nanomaterials. PMID:21230008

Wu, Haihua; Yang, Rong; Song, Baomin; Han, Qiusen; Li, Jingying; Zhang, Ying; Fang, Yan; Tenne, Reshef; Wang, Chen

2011-01-11

363

Plume dynamics and cluster formation in laser-ablated copper plasma in a magnetic field  

SciTech Connect

Laser-ablated copper plasma plume expanding in a nonuniform magnetic field and ambient gas is investigated to understand plume dynamics using optical emission spectroscopy and fast imaging of the plume. A peculiar oscillatory behavior of the plume observed in magnetic field is discussed. The appearance and enhancement of Cu{sub 2} (A-X) band in ambient gas and in the presence of magnetic field is reported. The presence of magnetic field favors the formation of copper clusters in the expanding plumes.

Pandey, Pramod K.; Thareja, R. K. [Department of Physics, Indian Institute of Technology, Kanpur, Kanpur 208016 (U.P.) (India)

2011-04-01

364

Mass spectroscopic characterization of yttrium-containing metallofullerene YC82 using resonant laser ablation  

SciTech Connect

In this paper, resonant laser ablation time-of-flight mass spectroscopy (RLA-TOF-MS) has been used to mass spectroscopic characterization of yttrium-containing fullerenes. Solvent soluble, yttrium-containing fullerenes are extracted from yttrium/carbon soot produced by the carbon-arc fullerene generation method. The RLA-TOF mass spectra indicate the presence of YC82. The metallofullerences YC60, YC70, Y2C82 and a series of Y2C2n are not observed by RLA-TOF-MS. This result is consistent with the ESR spectral result reported by Shinohara et al.

Wang Shiliang; Tian Jiahe; Dai Songtao; Chen Dieyan; Luo Chuping; Tan Haisong; Gan Liangbing; Huang Chunhui [Laser Single Atom Detection Laboratory, Department of Physics, Tsinghua University, Beijing 100084 (China); State Key Laboratory of Rare Earth Material Chemistry and Applications, Peking University, Beijing 100871 (China)

1995-04-01

365

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

Microsoft Academic Search

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

Annemie Bogaerts; Zhaoyang Chen

2005-01-01

366

Deposition of polymer barrier materials by resonant infrared pulsed laser ablation  

NASA Astrophysics Data System (ADS)

We describe resonant infrared pulsed laser deposition (RIR-PLD) of cyclic olefin copolymer, a barrier and protective layer; for comparison, we describe RIR-PLD of polystyrene and poly(ethylene dioxythiophene) about which we already have significant knowledge. Film deposition based on resonant infrared laser ablation is a low-temperature process leading to evaporation and deposition of intact molecules. In this paper, we focus on deposition of this model barrier and protective material that is potentially useful in the fabrication of organic light emitting diodes. The films were characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. We also compared the properties of films deposited by a free electron laser and a picosecond optical parametric oscillator.

Avanesyan, S. M.; Halabica, A.; Johnson, S. L.; Kelley, M. J.; Klopf, J. M.; Park, H. K.; Schriver, K. E.; Singaravelu, S.; Haglund, R. F., Jr.

2010-02-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

368

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

PubMed

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

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

2013-03-01

369

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

370

Laser ablation laser induced fluorescence for sensitive detection of heavy metals in water  

NASA Astrophysics Data System (ADS)

Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the first pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (? 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy single-pulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 muJ and an excitation laser pulse energy of 8 muJ. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the effect of detector gain, the gate delay and the gate width were studied. In this thesis LIBS and LA-LIF were also used to analyze ultralow volumes of analyte in liquids in micro uidic geometries. LIBS was applied for the detection of Na in liquid droplets in a microfluidic system. The detection of Na as low as 360 femtograms was demonstrated for 100 shots integrated in this system. An LOD of 7 ppm for Pb for 100 shot accumulation was demonstrated using the LA-LIF technique on an 18 mum diameter microdroplet. To study the laser interaction with the water targets the MEDUSA one dimensional hydrocode was used. The propagation of the shockwave and plume dynamics were studied using this modeling code. The expansion of the plume was studied and compared to experimentally measured values and to physical models for blast wave expansion and stagnation. Two preconcentration techniques were also studied, one of which used a wood-chip as a substrate to absorb the analyte liquid and wick the salt on to the surface for analysis and the other used an electroplating technique to plate the analyte metal as a thin film on a substrate metal used as a cathode. The electroplating method for preconcentration was also studied using a microchip laser and a LOD of 6.4 ppb for Pb in water was obtained for an accumalation of 200,000 shots.

Godwal, Yogesh

371

Fabrication of microchannels by UV laser ablation  

NASA Astrophysics Data System (ADS)

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

Takahashi, Satoshi; Suzuki, Yoshimasa; Yoshida, Yoshikazu

2003-02-01

372

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

373

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

NASA Astrophysics Data System (ADS)

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

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

1998-05-01

374

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

Microsoft Academic Search

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

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

1999-01-01

375

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

Microsoft Academic Search

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

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

2003-01-01

376

Laser desorption jet cooling spectroscopy  

NASA Astrophysics Data System (ADS)

Laser desorption followed by jet-cooling allows wavelength-selective as well as mass-selective detection of organic molecules desorbed from a surface without fragmentation. The absolute detection sensitivity is demonstrated with the perylene molecule. A two-color REMPI spectrum (400 wavelength points) of perylene is recorded using only 30 picogram of material. Rotational cooling to 5 - 10 K is demonstrated with laser-desorbed anthracene; vibrational cooling below 15 K is demonstrated with laser-desorbed diphenylamine. The ability to take a 'snapshot' of molecules on a surface is illustrated with the spectrum of benzoic acid monomers. Other applications are discussed, i.e. PABA dimer spectroscopy and detection of C60.

de Vries, Mattanjah S.; Hunziker, Heinrich E.; Meijer, Gerard; Wendt, H. R.

1991-04-01

377

Femtosecond laser ablation of polymethyl-methacrylate with high focusing control  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

378

Onset of laser ablation in CaF2 crystal under excimer laser irradiation  

NASA Astrophysics Data System (ADS)

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

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

2002-06-01

379

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

380

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

381

Femtosecond laser ablation characteristics of nickel-based superalloy C263  

Microsoft Academic Search

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

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

2009-01-01

382

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

383

Controlled USP laser ablation strategies for shaping optics  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

384

Quantitative determination of element concentrations in industrial oxide materials by laser-induced breakdown spectroscopy  

Microsoft Academic Search

Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) method is employed for quantitative determination of oxide\\u000a concentrations in multi-component materials. Industrial oxide materials from steel industry are laser ablated in air, and\\u000a the optical plasma emission is collected by spectrometers and gated detectors. The temperature and electron number density\\u000a of laser-induced plasma are determined from measured LIBS spectra. Emission lines of aluminium (Al),

B. Praher; R. Rössler; E. Arenholz; J. Heitz; J. D. Pedarnig

385

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

386

Femtosecond-laser-induced breakdown spectroscopy of explosives  

NASA Astrophysics Data System (ADS)

We use femtosecond laser-induced breakdown spectroscopy (LIBS) to detect trace amounts of TNT and RDX. A high-power pulsed laser is used in LIBS to form a plasma on the material surface and the optical emission from the plasma is spectrally analyzed to determine the material composition. Femtosecond LIBS results for TNT and RDX on aluminum substrates and glass slides are reported. Results are examined in terms of the optical properties of the substrate and the strong linear absorption for aluminum is contrasted with the weaker multiphoton absorption for glass. Optical microscope images of the ablated explosives are shown for femtosecond and nanosecond laser excitation. Fragmentation studies by femtosecond laser mass spectrometry are used to interpret LIBS results.

Dikmelik, Yamac; McEnnis, Caroline; Spicer, James B.

2006-06-01

387

Phase-modulation laser spectroscopy  

NASA Astrophysics Data System (ADS)

A novel phase-modulation technique which permits subkilohertz-laser stability and new levels of precision in laser spectroscopy was reported recently. For spectroscopy, the basic arrangement consists of a combination of an optical pump and a probe field which is phase modulated. The pump prepares the atomic sample by burning a narrow hole within the atom's inhomogeneous line shape, and the probe beam samples the prepared hole when its modulation sidebands are swept into resonance. Off resonance, the probe is balanced as pairs of sidebands produce heterodyne beat signals of opposite phase which just cancel. On resonance, the balance is upset and yields a nonvanishing beat signal with a Lorentzian absorption or dispersion line shape and with residual noise approaching the shot noise limit. Here we investigate the theory of phase-modulation spectroscopy. We treat the nonlinear response of an atomic two-level quantum system subject to an intense pump and a weak copropagating or counterpropagating phase-modulated probe beam. The density-matrix equations of motion are solved by a Laplace-transform method and by the novel use of a translation operator which allows the infinite hierarchy of coupled equations to close. A solution equivalent to the rate-equation result is developed and coherence corrections are found which predict new resonances that have just been detected in this laboratory. The delayed pump-probe technique encountered in solid-state laser spectroscopy is analyzed in this context for two- and three-level quantum systems. The response of a Fabry-Perot cavity to a phase-modulated light wave is examined also and reveals an unexpected absorption feature.

Schenzle, Axel; Devoe, Ralph G.; Brewer, Richard G.

1982-05-01

388

Peak polarity overturn for charged particles in laser ablation process  

SciTech Connect

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

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

2006-07-01

389

Magnetic resonance-guided percutaneous laser ablation of uterine fibroids.  

PubMed

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

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

2000-10-01

390

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

PubMed

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

Hirata, Takafumi; Kon, Yoshiaki

2008-03-01

391

Plasma properties of laser-ablated strontium target  

SciTech Connect

Optical emission spectroscopy is used to characterize the laser-produced strontium plasma by using the fundamental, second, and third harmonics of a Nd:YAG laser. Variations in the electron temperature (T{sub e}) and number density (N{sub e}) as a function of distance, laser irradiance, and ambient gas pressure have been studied by using the emission lines of neutral strontium. In addition, absorption mechanisms responsible for the variation of the electron temperature and number density and the dependence of the spectral line intensities on the ambient gas pressure and laser irradiance are discussed.

Hafeez, S.; Shaikh, Nek M.; Rashid, Baber; Baig, M. A. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan)

2008-04-15

392

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

393

Analysis of laser ablation: Contribution of ionization energy to the plasma and shock wave properties  

SciTech Connect

By fitting simulation results with experimentally measured trajectories of the shock wave and the vapor/background gas contact surface, we found that inclusion of ionization energy in the analysis leads to a change in the evolution of the pressure, mass density, electron number density, and temperature of the vapor plume. The contribution of ionization energy to both the plasma and shock wave has been neglected in most studies of laser ablation. Compared to previous simulations, the densities, pressures, and temperatures are lower shortly after the laser pulse (<5 ns), but become larger (by a factor of 2) as the time after the laser pulse increases (>50 ns). The predicted laser energy conversion ratio also showed about a 20% increase (from 35% to 45%) when the ionization energy is considered. The changes in the evolution of the physical quantities result from the retention of the ionization energy in the vapor plume, which is then gradually transformed to kinetic and thermal energies. When ionization energy is included in the simulation, the vapor plume attains higher expansion speeds and temperatures for a longer time after the laser pulse. The better determination of the temperature history of the vapor plume not only improves the understanding of the expansion process of the laser induced vapor plume but also is important for chemical analysis. The accurate temperature history provides supplementary information which enhances the accuracy of chemical analysis based on spectral emission measurements (e.g., laser induced breakdown spectroscopy)

Wen, S.-B.; Mao Xianglei; Greif, Ralph; Russo, Richard E. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States); Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2007-08-15

394

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

NASA Astrophysics Data System (ADS)

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

Ozono, Kazue; Obara, Minoru; Sakuma, Jun

2003-06-01

395

Fabrication of Mg-doped ZnO thin films by laser ablation of Zn:Mg target  

Microsoft Academic Search

Mg-doped ZnO thin films were fabricated by laser ablation of Zn:Mg targets consisting of Mg metallic strips and Zn disk in oxygen atmosphere with a goal to facilitate convenient control of Mg contents in the films. The characteristics of the deposited films were examined by analyzing their photoluminescence (PL), X-ray diffraction and X-ray photoelectron spectroscopy (XPS) spectra. Mg contents as

Tae Hyun Kim; Jin Jae Park; Sang Hwan Nam; Hye Sun Park; Nu Ri Cheong; Jae Kyu Song; Seung Min Park

2009-01-01

396

TOF MS studies concerning the synthesis of BN and B-C-N nanaostructured materials by laser ablation  

Microsoft Academic Search

Time-of-flight mass spectroscopy (TOF MS) spectra of ions ablated from BN-ceramic, amorphous carbon, graphite and fullerene-60 targets were recorded at different experimental conditions. It was found that the TOF MS spectra significantly simplify as the energy density of the laser radiation was increased, and show temporal evolution as the distance between the target surface and work area of TOF MS

Dachun Huang; Vladimir I. Makarov; Arturo Hidalgo; Brad R. Weiner; Gerardo Morell

2006-01-01

397

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

398

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

399

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

400

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

Microsoft Academic Search

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

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

1999-01-01

401

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

NASA Astrophysics Data System (ADS)

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

Makarov, G. N.

2013-07-01

402

Improved analytical characterization of solid waste-forms by fundamental development of laser ablation technology. 1998 annual progress report  

SciTech Connect

'This EMSP research endeavors to understand fundamental laser-ablation sampling processes and to determine the influence of these processes on analytical characterization of EM waste-site samples. The issues germane to the EMSP are sensitivity and accuracy of analysis. These issues are researched by studying fractionation, sample transport, mass loading, and analytical system optimization. Inductively coupled plasma-mass spectroscopy (ICP-MS) is emphasized in this research because of its use throughout the DOE labs and sites. This report summarizes research performed over the first half of this three-year program. Four issues were emphasized to improve analytical sensitivity and accuracy, including the time dependent laser removal of mass from a solid sample, fractionation, particle generation and transport, and optimization of the ICP-MS for laser ablation sampling. This research has led to six journal publications.'

Russo, R.E.

1998-06-01

403

Characterization of binary silver based alloys by nanosecond-infrared-laser-ablation-inductively coupled plasma-optical emission spectrometer  

NASA Astrophysics Data System (ADS)

A nanosecond infrared laser ablation (LA) system was examined to determine the composition of several silver–copper alloys through an inductively coupled plasma-optical emission spectrometer (ICP-OES). Samples with different concentrations were prepared and analyzed by atomic absorption, and ICP-OES after sample digestion, and compared with an energy-dispersive x-ray spectrometer–scanning electron microscopy (EDX–SEM). Elemental fractionation during the ablation process and within the ICP was investigated for different laser frequencies and fluences. Samples were used for optimizing and calibrating the coupling between LA to the ICP-OES system. Results obtained from the samples analysis were in agreement with those obtained by atomic absorption spectroscopy, ICP-OES and EDX–SEM, showing that fractionation was not significant for laser fluences higher than 55 J cm?2.

Márquez, Ciro; Sobral, Hugo

2013-11-01

404

Laser ablative cutting of ceramics for electronics applications  

SciTech Connect

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

Warner, B. E., LLNL

1996-03-01

405

Heat transfer and phase change during picosecond laser ablation of nickel  

Microsoft Academic Search

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

David A. Willis; Xianfan Xu

2002-01-01

406

Plume Dynamics in Tea CO2 Laser Ablation of Polymers and Graphite  

Microsoft Academic Search

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

T. Y. Tou; O. H. Chin

2008-01-01

407

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

408

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

Microsoft Academic Search

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

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

2009-01-01

409

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

Microsoft Academic Search

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

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

2009-01-01

410

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

Microsoft Academic Search

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

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

1998-01-01

411

Laser Ablation Plume Expansion In The Presence Of Charged Impurities  

SciTech Connect

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

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

2008-09-23

412

Production and acceleration of ion beams by laser ablation  

SciTech Connect

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

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

2012-02-15

413

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

Microsoft Academic Search

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

Thure E. Cerling; Zachary D. Sharp

1996-01-01

414

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...

415

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

Microsoft Academic Search

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

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

1999-01-01

416

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

Microsoft Academic Search

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

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

2002-01-01

417

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

Microsoft Academic Search

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

Chao-Xuan Liu; Jin-Woo Choi

2012-01-01

418

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

Microsoft Academic Search

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

Kaustubh R. Rau

2000-01-01

419

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

Microsoft Academic Search

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

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

2003-01-01

420

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

Microsoft Academic Search

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

Richard E

2000-01-01

421

Mechanism of water augmentation during IR laser ablation of dental enamel  

Microsoft Academic Search

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

Daniel Fried; Nahal Ashouri; Thomas Breunig; Ramesh Shori

2002-01-01

422

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

423

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

424

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

Microsoft Academic Search

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

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

1998-01-01

425

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

Microsoft Academic Search

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

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

1999-01-01

426

Ultra-fast movies of thin-film laser ablation  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

427

Synthesis and characterization of nanocrystalline niobium aluminides by laser ablation technique  

NASA Astrophysics Data System (ADS)

This thesis presents a study of the synthesis and characterization of nanocrystalline Nb-aluminides by laser ablation in an ambient gas atmosphere. The goal of this work is to establish the science base for the nanocrystalline synthesis by this method by studying the relationships between processing conditions and physical characteristics of products. Using a newly developed ablation system, nanocrystalline Nb-aluminides have been synthesized by varying the processing variables such as laser energy density and He backing gas pressure. Ablation rate is relatively insensitive to the variation of He gas pressure. However, we observe a threshold laser energy density above which the ablation rate does not increase. Collection rate of powders depends strongly on the He backing gas pres