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1

Laser ablation loading of a radiofrequency ion trap  

NASA Astrophysics Data System (ADS)

The production of ions via laser ablation for the loading of radiofrequency (RF) ion traps is investigated using a nitrogen laser with a maximum pulse energy of 0.17 mJ and a peak intensity of about 250 MW/cm2. A time-of-flight mass spectrometer is used to measure the ion yield and the distribution of the charge states. Singly charged ions of elements that are presently considered for the use in optical clocks or quantum logic applications could be produced from metallic samples at a rate of the order of magnitude 105 ions per pulse. A linear Paul trap was loaded with Th+ ions produced by laser ablation. An overall ion production and trapping efficiency of 10-7 to 10-6 was attained. For ions injected individually, a dependence of the capture probability on the phase of the RF field has been predicted. In the experiment this was not observed, presumably because of collective effects within the ablation plume.

Zimmermann, K.; Okhapkin, M. V.; Herrera-Sancho, O. A.; Peik, E.

2012-06-01

2

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

3

Ultrashort-laser-produced heavy ion generation via target laser-ablation cleaning  

NASA Astrophysics Data System (ADS)

It has become apparent in the last few years that the surface contamination on laser-acceleration targets is a major impediment to the acceleration of the actual target ions. To this end we have performed experiments at the Los Alamos Trident Laser facility using one arm of the Trident laser at 150 ps to ablatively clean targets that are subsequently irradiated by the Trident TW Short-pulse arm to accelerate the bulk target ions to high energies. The 150 ps ablation pulse rids the rear of the target of its omnipresent surface contamination layer allowing the short-pulse to illuminate the target and accelerate ions via the Target Normal Sheath Acceleration (TNSA) mechanism. Our experimental results are compared to the LASNEX code to validate and improve our predictive capabilities for future acceleration experiments.

Flippo, K. A.; Hegelich, B. M.; Schmitt, M. J.; Meserole, C. A.; Fisher, G. L.; Gautier, D. C.; Cobble, J. A.; Johnson, R.; Letzring, S.; Schreiber, J.; Schollmeier, M.; Fernández, J. C.

2006-06-01

4

Magnetic control of laser ablation plasma for high-flux ion injectors  

NASA Astrophysics Data System (ADS)

We investigated the interaction of a laser ablation plasma with a longitudinal magnetic field aiming to create a directionally moving plasma for high-flux and low-emittance ion injectors. To study the plasma dynamics, time-of-flight measurements and energy analysis of the plasma ion flux were made as functions of the laser intensity and the magnetic field. Moderate magnetic field (˜0.2T) directed the fast and highly charged ions in the target normal. In addition, a slow peak appeared and increased with increasing the magnetic field. These results indicated that directional electric field is formed and recombination increases by the application of longitudinal magnetic field.

Ikeda, Shunsuke; Nakajima, Mitsuo; Hasegawa, Jun; Kawamura, Tohru; Horioka, Kazuhiko

2014-01-01

5

Short-Pulse Heavy Ion Production via Target Laser-Ablation-Cleaning and Proton Acceleration Suppression  

NASA Astrophysics Data System (ADS)

In the last few years it has become apparent that the surface contamination on laser ion-acceleration targets is a major impediment to the acceleration of the actual target ions. To this end we have performed experiments at the Los Alamos Trident Laser facility using one arm of the Trident laser at 150 ps to ablatively clean the target's rear-surface. The front-surface is then irradiated by the Trident TW Short-pulse to accelerate the heavy-ions to high energies. This process was used on targets consisting of 15 microns of vanadium. Normally ions with the lightest charge to mass ratio (i.e. protons) would be accelerated preferentially from the surface at the expense of heavier ions. However, with the rear contamination layer removed, the TNSA mechanism is available to accelerate the bulk material ions to high energies. A lower energy proton component from the front surface is also present and has been observed experimentally and modeled recently with the TRISTAN PIC code, and mitigation is discussed. We report on the ion beam parameters achieved to date, including laser-beam conversion efficiency, ion energy, and beam divergence. Our ablation results are compared to the LASNEX code to validate and improve our predictive capabilities for future experiments.

Flippo, Kirk; Lin, T.

2005-10-01

6

Energy distribution of ions produced by laser ablation of silver in vacuum  

NASA Astrophysics Data System (ADS)

The ion energy in a silver ablation plume for fluence in the range of 0.6-2.4 J cm-2, typical for a pulsed laser deposition (PLD) experiment has been investigated. In this fluence range the ion fraction of the ablated particles becomes gradually dominant and can be utilized to characterize the ablation process. A silver target in vacuum was irradiated with a Nd:YAG laser at a wavelength of 355 nm and detailed measurements of the time-resolved angular distribution of plume ions were made. In contrast to earlier work, the beam spot was circular such that any flip-over effect of the plume is avoided. The angular energy distribution of ions in forward direction exceeds values of 500 eV, while at large angles the ion energy tail is below 100 eV. The maximum for the time-of-flight distributions agrees consistently with the prediction of Anisimov's model in the low fluence range, in which hydrodynamic motion prevails.

Toftmann, B.; Schou, J.; Canulescu, S.

2013-08-01

7

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

8

Laser ablation of silicon in neon gas: Study of excitation mechanism of neon neutrals by ablated silicon ions  

SciTech Connect

The excitation mechanism of buffer gas in the laser-ablation process was investigated by time- and space-resolved emission spectroscopies. A silicon disk was ablated in neon gas at a pressure of 1 torr by the fundamental beam output of a Nd: yttrium aluminum garnet laser (1064 nm). The time-resolved emission spectra showed the generation of excited silicon ions Si{sup n+}*(n=1-3) and excited neon neutrals Ne* to the 2p{sub 1} level immediately after laser irradiation. Excitation of Ne to the 2p{sub n}(n=2-10) levels was delayed by 150 ns. The temporal evolutions of the space-resolved emission from Ne* indicated excitation by fast (<100 ns) and/or slow (<300 ns) processes. The slow process contributed to all 2p{sub n} levels, while the fast process was observed only in excitation to the 2p{sub 1} level. This means that the fast process involves level-selective excitation. Based on temporal evolutions, the energy levels, and the collision cross sections of Ne and Si{sup n+}, we assigned the fast and slow processes to excitations by electronic-to-electronic energy transfer from Si{sup 2+}* and translational-to-electronic energy transfer from Si{sup +}, respectively.

Saeki, Morihisa; Hirata, Kohichi; Sakka, Tetsuo; Ohba, Hironori; Yokoyama, Atsushi [Department of Materials Science, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Department of Materials Science, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

2005-08-15

9

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

NASA Astrophysics Data System (ADS)

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

Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-02-01

10

Ablation cleaning techniques for high-power short-pulse laser produced heavy ion targets  

NASA Astrophysics Data System (ADS)

It has become apparent in the last few years that the light ion surface contamination on short-pulse laser targets is a major impediment to the acceleration of heavier target ions. Mitigation strategies have been tested in experiments at the Los Alamos Trident Laser facility using one arm of the Trident laser at 150 ps to ablatively clean a large area of heated targets in a single short that are subsequently irradiated by the Trident 30 TW short-pulse arm to accelerate the bulk target ions to high energies. This process was used on targets consisting of 15 microns of vanadium. The 150 ps pulse rids the rear of the target of its omnipresent surface contamination layer, consisting mainly of water vapor and hydrocarbons, and allows the Trident 30 TW short-pulse arm to illuminate the target and accelerate ions via the Target Normal Sheath Acceleration (TNSA) mechanism. Because this mechanism relies on a laser generated electrostatic sheath, the ions with the lightest charge to mass ratio (i.e. protons) would be accelerated preferentially at the expense of heavier ions. However with the contamination layer removed, and hence the bulk of the available protons, the TNSA mechanism is able to accelerate the bulk material ions to high energies. Our experimental results are discussed and compared to the LASNEX rad-hydro code to validate and improve our predictive capabilities for future acceleration experiments.

Flippo, Kirk A.; Hegelich, B. Manuel; Schmitt, Mark J.; Gauthier, D. Cort; Meserole, Chad A.; Fisher, Gregory L.; Cobble, James A.; Johnson, Randall A.; Letzring, Samuel A.; Fernández, Juan C.; Schollmeier, Marius; Schreiber, Jörg

2006-05-01

11

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

SciTech Connect

We are developing a new technique for the chemical characterization of microparticles based upon the use of electrodynamic traps. The electrodynamic trap has achieved widespread use in the mass spectrometry community in the form of the ion trap mass spectrometer or quadrupole ion trap. Small macroscopic particles can be confined or levitated within the electrode structure of a three-dimensional quadrupole electrodynamic trap in the same way as fundamental charges or molecular ions by using a combination of ac and dc potentials. Our concept is to use the same electrode structure to perform both microparticle levitation and ion trapping/mass analysis. The microparticle will first be trapped and spatially stabilized within the trap for characterization by optical probes, i.e., absorption, fluorescence, or Raman spectroscopy. After the particle has been optically characterized, it is further characterized using mass spectrometry. Ions are generated from the particle surface using laser ablation or desorption. The characteristics of the applied voltages are changed to trap the ions formed by the laser with the ions subsequently mass analyzed. The work described in this paper focuses on the ability to perform laser desorption experiments on microparticles contained within the ion trap.

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

1991-01-01

12

Emittance dependence on anode morphology of an ion beam provided by laser ablation  

NASA Astrophysics Data System (ADS)

In this work, we studied the characteristics of ion beams generated by Platone accelerator in different anode configurations. The accelerator is a laser ion source with two gaps which accelerate the ions in cascade. The laser is a ns pulsed KrF able to apply irradiances of 109-1010 W/cm2. The target ablated was pure disk of Cu. The accelerating voltage applied in this work was 60 kV. The emittance evaluation was performed by the pepper pot method utilizing radio-chromic films, EBT Gafchromic, as sensible targets. The study was performed by varying the geometric configuration of the anode (the extracting electrode), modifying the hole morphology, e.g. a plane and curved grid were mounted in order to change the extraction configuration. The results were compared with the ones obtained with the extraction hole without any grid. For the normalized emittance the lowest value was 0.20? mm mrad.

Velardi, L.; Delle Side, D.; Nassisi, V.

2014-07-01

13

Ion velocity measurements for laser mass ablation studies  

Microsoft Academic Search

The measurements used 10 J, 1.7 ns (FWHM), 1.06 micrometers laser pulse to irradiate flat Al targets. A range of lenses with focal lengths from 75 mm to 2000 mm were used to focus 50 mm diameter beam on target, resulting in a range of optical spot diameters from 30 micrometers to 3.5 mm. Irradiance on target was varied by

L. Pina

1981-01-01

14

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

SciTech Connect

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

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

1991-01-01

15

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

16

Infrared laser bone ablation  

Microsoft Academic Search

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

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

1988-01-01

17

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

SciTech Connect

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

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

2013-11-15

18

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

19

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

Microsoft Academic Search

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

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

2002-01-01

20

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

SciTech Connect

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

Ritchie, R.H. (Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6123 (United States) Department of Physics, University of Tennessee, Knoxville, Tennessee 37966 (United States)); Manson, J.R. (Department of Physics, Clemson University, Clemson, South Carolina 29631 (United States)); Echenique, P.M. (Materialen Fisika Saila, Universidad Pais Vasco, Apartado 1072, San Sebastian (Spain))

1994-01-15

21

Laser ablation of dyes  

NASA Astrophysics Data System (ADS)

High density 50 ?s pulses of the UV dyes PPF, POPOP and BBO and of two dyes in the visible region, Xanthen N92 and Fluorol 7GA were generated by laser ablation. Dye powders were pressed with 7800 kp/cm 2 in round pellets which were ablated by exposure to KrF excimer laser radiation (248 nm) at a fluence of 100 mJ/cm 2. The ablation cloud was optically activated with a XeCl excimer laser. Its fluorescence spectrum was measured and was identified as a dye vapour fluorescence spectrum by comparison to conventional dye solution and dye vapour spectra. The dye cloud is not deflected in an electric field (10 6 V/m). By changing the delay time between the ablation laser and the focused activation laser, the velocity distribution of the ablated dye was measured. Its maximum is at 600 m/s for PPF. Knowing the thickness of the ablated dye layer per shot (300 Å) and the size of the ablation cloud (pictures of a video camera), one can estimate the maximum density of the dye in the gas pulse to be 10 -5 mol/ l in the range of concentration of lasing dyes. However, no lasing was observed up to now.

Späth, M.; Stuke, M.

1992-01-01

22

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

SciTech Connect

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

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

1994-10-15

23

Charge-transfer cross section measurements using laser ablation ion source and reflection time-of-flight mass spectrometer  

Microsoft Academic Search

A new method is developed that combines the production of ions by laser ablation with a reflection time-of-flight mass spectrometer (RTOFMS) for charge-transfer cross section measurements. This method allows a specific charge-transfer channel of an ion-neutral pair to be measured at energies of about 0.1 KeV\\/amu. The charge- transfer cross section is determined by measuring the intensity ratio of the

Jiebing Wang

1997-01-01

24

Mechanisms of ablation and ion formation in infrared laser mass spectrometry  

NASA Astrophysics Data System (ADS)

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

Papantonakis, Michael Robert

25

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

27

Ionization and stopping of heavy ions in dense laser-ablated plasmas  

NASA Astrophysics Data System (ADS)

Enhanced plasma stopping and enhanced projectile ionization in plasma are considered within the framework of the standard stopping model (SSM), the most economical extension to plasmas of the standard cold-matter formalism. The main goal of this work is to check quantitatively the SSM predictions using the setup SPQR1 (stopping plasma quantitatively reinforced) developed at Bruyères-le-Chatel. It consists of a laser-ablated C or Al plasma synchronized with a 50-MeV Cu ion beam bunched out of a tandem Van de Graaff accelerator. A combination of a Thomson parabola spectrometer and an ionographic tube provides charge-state distribution and energy-loss data. Plasma expansion is modeled and yields electron-temperature and density-profile-matching diagnostics performed in the interaction chamber. In agreement with theoretical expectations, charge-distribution maxima at the plasma exit are shifted toward higher ionization compared to the equivalent results in cold matter. The distribution width is smaller than its cold-target homologue. Energy losses in partially ionized C and Al targets are several times larger than in the respective cold solid. The relevance to heavy-ion-driven inertial fusion is emphasized.

Couillaud, C.; Deicas, R.; Nardin, Ph.; Beuve, M. A.; Guihaumé, J. M.; Renaud, M.; Cukier, M.; Deutsch, C.; Maynard, G.

1994-02-01

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

OCDR guided laser ablation device  

DOEpatents

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

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

2002-01-01

30

Laser induced desorption of ions from insulators near the ablation threshold  

NASA Astrophysics Data System (ADS)

The intensity dependence of the yield and kinetic energies of positive ions desorbed from SrF 2, CaF 2 and MgO under 193 and 308 nm excimer laser irradiation has been investigated by the time-of-flight method. The main ion species observed were the metal ions (Sr +, Ca +, Mg +), molecular ions (SrF +, CaF + and MgO +) and F + or O +, respectively. Nearly all observed ion species gain kinetic energies in the order of hundreds of eV for laser intensities above the emission threshold. These results indicate that dielectric breakdown leads to the formation of a plasma at the surface. Analysis of the near threshold region has shown no reliable and reproducible correlation with a multiphoton process, with the exception of F + emission from SrF 2 under 308 nm irradiation. Furthermore, for laser intensities well above the threshold we observed a constant total ion yield, but large fluctuations of the yields for the components (e.g. Sr + and F + in the case of SrF 2) showing a pronounced anticorrelation. We have analyzed this behavior in terms of consecutive laser shots and found strong evidence that a laser shot does precondition the surface for the next laser shot. To obtain information about the surface composition after a single laser shot, an Ar + ion pulse was used to analyze the top layer.

Kreitschitz, O.; Husinsky, W.; Betz, G.; Tolk, N. H.

1993-05-01

31

Femtosecond laser ablation of solid materials  

NASA Astrophysics Data System (ADS)

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

Ye, Mengqi

32

CO2 laser ablation of biological tissue  

Microsoft Academic Search

This paper presents a comprehensive review of the CO2 laser ablation of biological tissue. Based on energy balance for modeling laser ablation, the thermal relaxation time and the ablation threshold are determined. Laser ablation of biological tissue is related to the spatial coherence of laser beams, so that the propagation of laser beams, the beam quality and the focusability of

Dan C. Dumitras; Doru C. Dutu; Consuela-Elena Matei

1998-01-01

33

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

NASA Astrophysics Data System (ADS)

A novel laser ablation and ionization time-of-flight mass spectrometer has been used for direct elemental analysis of alloys. The system was incorporated with an ion guide cooling cell to reduce the kinetic energy distribution for the purpose of better resolution. Parametric studies have been conducted on the system with respect to the buffer gas pressure and the distance from sample to the nozzle to obtain the maximal signal intensities. In order to obtain satisfactory relative sensitivity coefficients (RSC) for different elements, the influence of the laser irradiance, nozzle voltage, rf frequency and voltage of the hexapole were also investigated. Under the optimized conditions, the RSC of different elements were available for direct semi-quantitative analysis. The mass resolving power (FWHM) of the spectrometer was approximately 7000 (m/?m) and the limit of detection (LOD) was 10 - 6 g/g.

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

2008-08-01

34

Multiple target laser ablation system  

DOEpatents

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

Mashburn, D.N.

1996-01-09

35

Multiple target laser ablation system  

DOEpatents

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

Mashburn, Douglas N. (Knoxville, TN)

1996-01-01

36

Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation  

SciTech Connect

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

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

2013-02-28

37

Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation  

NASA Astrophysics Data System (ADS)

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

Toftmann, B.; Doggett, B.; Budtz-Jørgensen, C.; Schou, J.; Lunney, J. G.

2013-02-01

38

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

39

Resonant laser ablation: Mechanisms and applications  

SciTech Connect

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

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

1994-06-01

40

Angular emission distributions of neutrals and ions in laser ablated particle beams  

NASA Astrophysics Data System (ADS)

The present work represents investigations of angular emission distributions in laser-produced particle beams resolved for the different ion groups (up to q=4) and the neutral particle component. The measurements are for a spectrum of target masses: 12 C, 27Al, 48 Ti, 59Ni, 96Mo and 181Ta. The plasma was produced by obliquely incident Q-switched pulses (TAU=5~ns and LAMBDA=1.06~MU m) of a Nd-YAG laser focused to energy densities ranging from about 20 to 180~J~cm-2. For the first time the results reveal in detail that the emission distributions systematically depend on the degree of ionization of the particles in the cloud. While for the neutral particles the angular emission is always dominated by a broad background with an additional, but less pronounced, peaked component, the background component rapidly but continuously diminishes with the increasing charge state of the ions. If, in the usual way, the emission distribution is approximated by the superposition of a cosine and a cosn fit function, the distribution of ions with qgeq 2 can already be well fitted by a cosn function alone. It seems highly probable, that this behaviour essentially is a result of the recombination dynamics during the expansion. It was found that the effect holds for all atomic masses investigated, whereby the mass dependence of the exponent n for all species behaves alike, approximately following a A3/4 law.

Thum-Jager, Andrea; Rohr, Klaus

1999-11-01

41

Synthesis technique of diamondlike carbon films by laser ablation ion source in atmosphere  

NASA Astrophysics Data System (ADS)

We have developed a technique of depositing a synthetic diamond-like carbon film on glass substrate in atmosphere at ambient temperature. By placing a glass substrate within the plume created by irradiating a carbon target with a Nd:YAG laser, we are able to deposit a diamond- like carbon film on the surface of the substrate. Using a highly purified graphite carbon target insures that only carbon ions are ejected and present in the plume. We will provide an analysis of the films by both vertical and diagonal irradiation by Raman spectroscopy and electron probe micro analysis.

Suzuki, Kaoru; Taniyama, Tetsuya; Nakata, Junji; Masutani, Takaya

1992-11-01

42

Laser Ablation of Biological Tissue Using Pulsed CO2 Laser  

Microsoft Academic Search

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and

Yuichi Hashishin; Shu Sano; Takeyoshi Nakayama

2010-01-01

43

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

44

UV Laser Ablation of Electronically Conductive Polymers.  

National Technical Information Service (NTIS)

The UV laser ablation of thin polypyrrole and polyaniline films coated on an insulating substrate is described. UV laser ablation is used to pattern the conductive polymer coating; patterns with submillimeter features are easily obtained with edge resolut...

L. S. Van Dyke C. J. Brumlik Z. Yu G. J. Collins C. R. Martin

1992-01-01

45

Laser surface ablation cleaning of nuclear facilities  

NASA Astrophysics Data System (ADS)

High power Nd:YAG laser beam with wavelength 1064nm, pulsewidth 10 picosecond regime was focused onto the scanning targets of SUS304 stainless steel with Zn coating of thickness 21 micrometers , and delivered via a step index fused silica optical fiber of length 3m and core diameter 1mm. Irradiation ablation effect and some basic aspects of high power laser beam transporting in optical fiber were studied. Ablation rate was defined as ablated volume to laser fluence and used as a description of ablation cleaning ability which was investigated by means of ablated profile measurement, ablation rate calculation, chemical composition analysis of ablated area.

Zhou, Xianglin; Imasaki, Kazuo; Umino, Hideo; Sakagishi, Kohji; Nakai, Sadao; Yamanaka, Chiyoe

2000-01-01

46

Laser ablation studies of concrete  

SciTech Connect

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

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

1999-10-20

47

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

NASA Astrophysics Data System (ADS)

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

Haustrup, N.; O’Connor, G. M.

2014-05-01

48

Structural identification and quantification of protein phosphorylations after gel electrophoretic separation using Fourier transform ion cyclotron resonance mass spectrometry and laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

In the present work mass spectrometric approaches are described for the identification of phosphorylated protein structures, and the direct quantification of protein–phosphorus contents, using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). An ultrahigh resolution FT-ICR-MS method was developed and applied for the structural identification of phosphorylations in proteins, using direct

J. Sabine Becker; Sergej F. Boulyga; J. Susanne Becker; Carola Pickhardt; Eugen Damoc; Michael Przybylski

2003-01-01

49

Information recording by laser ablation  

Microsoft Academic Search

Information recording by laser ablation involves energy absorption by an active layer followed by heating at the focal point and in the immediately adjacent area. We have used various organic dyes as recording media and characterized their properties. The substrates employed were made of polymethyl methacrylate (PMMA) or polycarbonate (PC). The influence of defect in the substrate and the birefringence

Maria Bardosova; A. V. Irlin; G. Cik; Volodymir G. Tsukanov

1995-01-01

50

Nanoparticle Formation by Laser Ablation  

Microsoft Academic Search

The properties of nanoparticle aerosols of size ranging from 4.9?nm to 13?nm, generated by laser ablation of solid surfaces are described. The experimental system consisted of a pulsed excimer laser, which irradiated a rotating target mounted in a cylindrical chamber 4?cm in diameter and 18-cm long. Aerosols of oxides of aluminum, titanium, iron, niobium, tungsten and silicon were generated in

Marc Ullmann; Sheldon K. Friedlander; Andreas Schmidt-Ott

2002-01-01

51

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

52

Simulation of Double-Pulse Laser Ablation  

SciTech Connect

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

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

2010-10-08

53

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

54

Observation of single high-harmonic enhancement by quasi-resonance with a tellurium ion in a laser-ablation plume at 29.44 nm  

SciTech Connect

We demonstrate the intensity enhancement of a single high-order harmonic (27th harmonic) at 29.44 nm by using lowly charged tellurium ions in a laser-ablation plume. The enhancement of a single harmonic is due to multiphoton resonance with a Te II transition having strong oscillator strength. By tuning the wavelength of the pump laser, we found that the enhancement factor depends on the difference between the wavelength of the enhanced harmonic and that of the strong radiative transition. For tellurium, we show that intense single harmonic generation can be generated when the wavelength of the 27th harmonic is closer to the wavelength of the strong transition.

Suzuki, Masayuki; Baba, Motoyoshi; Kuroda, Hiroto [The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Ganeev, Rashid A. [Scientific Association Akadempribor, Academy of Sciences of Uzbekistan, Akademgorodok, Tashkent 100125 (Uzbekistan); Ozaki, Tsuneyuki [Institut national de la recherche scientifique, 1650 boul. Lionel-Boulet Varennes (Quebec) J3X 1S2 (Canada)

2007-10-15

55

Analysis of Atomic Beams Produced by Laser-Induced Ablation  

Microsoft Academic Search

Pulsed atomic beams with flux densities above 1016 cm-2 s-1 have been produced in vacuum with high reproducibility by laser induced ablation from titanium and iron targets. The power of the TEA CO2 laser was kept at a level where plasma production at the target surface was avoided: no ions were detectable. The beams were analysed by laser fluorescence. The

K P Selter; H-J Kunze

1982-01-01

56

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

57

Precise laser ablation with ultrashort pulses  

Microsoft Academic Search

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

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

1997-01-01

58

Status of the Ablative Laser Propulsion Studies  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

59

Ionization in vacuum ultraviolet F2 laser ablated polymer plumes  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

60

Deposition of epitaxial Cu 2O films on (100) MgO by laser ablation and their processing using ion beams  

NASA Astrophysics Data System (ADS)

Epitaxial thin films of Cu 2O have been deposited on (100) MgO substrates by pulsed excimer laser ablation technique. Chemical polishing of the substrates by etching them in hot phosphoric acid prior to film deposition is found to be a critical step in realizing epitaxy. A KrF excimer laser operating at 248 nm wavelengths was used for ablation. The depositions were carried out at the laser energy density of 2 J/cm 2 and the pulse repetition rate of 5 Hz. The substrate temperature was held at 700°C and the oxygen partial pressure during deposition and cooling was 10 -3 Torr. The epitaxial nature of the deposited films was established via X-ray diffraction (XRD) and Rutherford back-scattering (RBS) channelling measurements. The epitaxial films thus obtained were then subjected to ion bombardment for studies of damage formation. Implantations were carried out using 110 keV Ar + ions over a dose range between 5 x 10 14 and 1.5 x 10 16 ions/cmz. The as-grown and implanted samples were subjected to resistivity versus temperature measurements in view of the importance of the Cu-O system in the context of the phenomenon of high temperature superconductivity.

Ogale, S. B.; Bilurkar, P. G.; Mate, Nitant; Parikh, Nalin; Patnaik, B.

1993-03-01

61

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

Microsoft Academic Search

Presence of more dental alloys in oral cavity often causes pathological symptoms. Due to various and multi-faced symptomatology, they tend to be a source of significant problems not only for the patient but also for the dentist. Metal ions released from alloys can cause subjective and objective symptoms in mouth. The aim of this study was detection of metal elements

Hana Kueerova; Tatjana Dostalova; J. Prochazkova

2002-01-01

62

In-plane aligned YBCO film on textured YSZ buffer layer deposited on NiCr alloy tape by laser ablation with only O+ ion beam assistance  

NASA Astrophysics Data System (ADS)

High critical current density and in-plane aligned YBa2 Cu3 O7-x (YBCO) film on a textured yttria-stabilized zirconia (YSZ) buffer layer deposited on NiCr alloy (Hastelloy c-275) tape by laser ablation with only O+ ion beam assistance was fabricated. The values of the x-ray phi-scan full width at half-maximum (FWHM) for YSZ(202) and YBCO(103) are 18° and 11°, respectively. The critical current density of YBCO film is 7.9 × 105 A cm-2 at liquid nitrogen temperature and zero field, and its critical temperature is 90 K.

Tang Huang, Xin; Qing Wang, You; Wang, Qiu Liang; Chen, Qing Ming

2000-02-01

63

Laser ablation of aluminosilicates: Comparison between allophane and mixed alumina/silicas by Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Laser ablation coupled to Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry [FT-ICR-MS] was used for analysing allophane aluminosilicates and mixtures of Al 2O 3/SiO 2. We show that both positive and negative ionization modes in FT-ICR-MS allows direct analysis of the various Al/Si ratios in allophanes and mixed alumina/silica samples. FT-ICR-MS technique provides a routine analytical methodology providing insight into the Al/Si molar composition and the origin of any aluminosilicate materials.

Castello, J.; Gaumet, J. J.; Muller, J. F.; Derousseaux, S.; Guilment, J.; Poncelet, O.

2007-07-01

64

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

65

Laser-plasma interactions in 532 nm ablation of Si  

Microsoft Academic Search

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

Gyoowan Han; P. Terrence Murray

2000-01-01

66

Laser mass spectrometric studies of high temperature superconductor ablation  

SciTech Connect

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

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

1990-01-01

67

Note: application of UF-4 emulsion films to detect low-energy ions from plasmas produced by laser ablation.  

PubMed

Detection of low-energy ions via Thomson parabola mass analyzer in the absence of any additional electrical systems is examined. Numerous low-energy ions were recorded on UF-4 solid state emulsion films. Kinetic energies between 1 and 4 keV of ions generated by YAG laser focused on Al and Ti targets were obtained using Thomson parabola measurements. Characteristics of ion tracks on the UF-4 detector are discussed in terms of pressure ranges of vacuum chamber. Moreover, differences in charges of ions between this study and previous spectroscopic measurements are discussed. PMID:24784684

Nishio, M; Shrestha, I; Kantsyrev, V L; Tooth, M; Takasugi, K

2014-04-01

68

Permalloy nanoparticles generated by laser ablation  

Microsoft Academic Search

We describe a new method for producing ultrafine magnetic particles that employs pulsed-laser particle ablation. Pulsed-laser radiation with wavelength of 248 nm was used to ablate 1 to 10 ?m diameter Permalloy microparticles under normal atmospheric conditions. The ejected nanoparticles were collected on silicon substrates for further analysis. Scanning electron micrographs of the samples were analyzed by computer aided image

Jaemyoung Lee; M. F. Becker; J. R. Brock; J. W. Keto; R. M. Walser

1996-01-01

69

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...

70

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

National Technical Information Service (NTIS)

A laser ablation/ionization mass spectrometer system is described for the direct chemical analysis of solids. An Nd:YAG laser is used for ablation and ionization of the sample in a quadrupole ion trap operated in an ion-storage (IS) mode that is coupled w...

J. K. Holt E. J. Nelson G. L. Klunder

2005-01-01

71

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

SciTech Connect

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

Witte, Travis

2011-11-30

72

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

SciTech Connect

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

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

2004-03-23

73

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

NASA Astrophysics Data System (ADS)

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 J.; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

2004-09-01

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

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

76

IR laser ablation of dental enamel  

NASA Astrophysics Data System (ADS)

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

Fried, Daniel

2000-03-01

77

Femtosecond laser ablation of the stapes.  

PubMed

A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations. PMID:19405768

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

2009-01-01

78

Femtosecond laser ablation of the stapes  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

79

Modern physical principles of laser ablation  

NASA Astrophysics Data System (ADS)

Physical principles of ablation, that is a phenomenon of fast superficial evaporation of the solid or liquid due to energy deposition into a thin layer near a surface of the specimen, are discussed. The opportunity of studying ablation at a laboratory is directly related to invention of a laser, which is very intensive source of radiation energy. For the first time, the laser ablation was demonstrated by Maiman in 1960 just by using his ruby laser for perforation of a razor blade. Since then there has been demonstrated, that the laser ablation has very complicated physics and can be used for a lot of applications. This fact results from a tremendous variety of laser parameters. Variations of laser intensity in time, radiation spectrum, geometry of specimen irradiation, its chemical composition, etc., result in unique possibility of changing physical parameters of ablation and, hence, its physical features, which allow us to use laser radiation both in science and technology beginning from laser material processing up to high-temperature plasma formation for laser fusion.

Krokhin, Oleg N.

2000-08-01

80

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

81

Dynamics of mid-infrared femtosecond laser resonant ablation  

NASA Astrophysics Data System (ADS)

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

Pang, Dongqing; Li, Yunxuan; Wang, Qingyue

2013-11-01

82

Dynamics of mid-infrared femtosecond laser resonant ablation  

NASA Astrophysics Data System (ADS)

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

Pang, Dongqing; Li, Yunxuan; Wang, Qingyue

2014-06-01

83

Estimation of Laser Ablation Surface Cleaning Efficiency  

Microsoft Academic Search

Based on the properties of a high-power short–pulsed Nd:YAG laser and its ablation effect investigated using a 21 ?m-thick\\u000a Zn-coated steel plate as a target, the surface cleaning efficiency of laser ablation processing was discussed through theoretical\\u000a analysis and experimental data. Cleaning efficiency was derived and a 2-fibre structure was used to examine whether calculations\\u000a agreed with experimental results. The

X. Zhou; K. Imasaki; H. Furukawa; S. Nakai; C. Yamanaka

2002-01-01

84

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

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

Hirata, Takafumi

2003-01-15

85

Pulse laser ablation of ground glass  

NASA Astrophysics Data System (ADS)

We have studied pulse laser ablation of ground glass surface. Ablation process in air and in vacuum has been observed by high speed framing camera. Burst of small fragments of glass has been observed in the present experiment, when ground glass surface is laser ablated through glass plate from rear side. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of ablation of other transparent materials. By using ns-duration Nd:YAG laser of 100 400 mJ/pulse, observed maximum particle velocity ranges from 0.5 to 1.5 km/s. In order to understand the particle generation process, scanning electron micrograph observation of the ground surface in the region of no laser irradiation and also in the damaged region, has been made. Cleavage surface structure has been evidenced in the damaged surface area, which stems from plenty of micro cracks covering the virgin glass surface. Effects of surface roughness on the particle generation were studied by using ground glass of quartz with different surface roughness. Produced glass particles were captured in vacuum by a polymethylmetacrylate (PMMA) plate. Size distribution was obtained by analysing the trapped particles on the PMMA plate and revealed that most probable particles size has almost no dependence on the initial surface roughness. Finally, we applied the phenomena to ignite pentaerithritoltetranitrate (PETN) powder explosive, and succeeded in igniting (PETN) powder only by laser ablation of ground glass.

Nagayama, K.; Kotsuka, Y.; Kajiwara, T.; Nishiyama, T.; Kubota, S.; Nakahara, M.

2007-11-01

86

A Proton Source via Laser Ablation of Hydrogenated Targets  

NASA Astrophysics Data System (ADS)

In this work we present results on the extraction of proton beams from a plasma generated by pulsed laser ablation of solid hydrogenated targets. The laser used was an excimer KrF operating at low irradiances (108–109 W/cm2) and nanosecond pulse duration. The ablated targets were disks obtained by compression of TiH2 powder. The ion emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. In order to improve the ion yield, an electrostatic extraction system was applied. Studies on the produced plasma for different laser irradiances and accelerating voltages have been performed. The results obtained show that this setup is suitable for a high yield proton source.

Delle Side, D.; Nassisi, V.; Velardi, L.

2014-04-01

87

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

88

Analysis of infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

89

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

90

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

91

Infrared Laser Ablation Sample Transfer for MALDI and Electrospray  

Microsoft Academic Search

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

Sung-Gun Park; Kermit King Murray

2011-01-01

92

Highspeed laser ablation cutting of metal  

NASA Astrophysics Data System (ADS)

In laser ablation cutting, irradiation of high-intense laser beams causes ejection of molten and evaporated material out of the cutting zone as a result of high pressure gradients, induced by expanding plasma plumes. This paper investigates highspeed laser ablation cutting of industrial grade metal sheets using high-brilliant continuous wave fiber lasers with output powers up to 5 kW. The laser beam was deflected with scan speeds up to 2700 m/min utilizing both a fast galvanometer scan system and a polygon scan system. By sharp laser beam focusing using different objectives with focal lengths ranging between 160 mm and 500 mm, small laser spot diameters between 16.5 ?m and 60 ?m were obtained, respectively. As a result high peak intensities between 3*108 W/cm² and 2.5*109 W/cm² were irradiated on the sample surface, and cutting kerfs with a maximum depth of 1.4 mm have been produced. In this study the impact of the processing parameters laser power, laser spot diameter, cutting speed, and number of scans on both the achievable cutting depth and the cutting edge quality was investigated. The ablation depths, the heights of the cutting burr, as well as the removed material volumes were evaluated by means of optical microscope images and cross section photographs. Finally highspeed laser ablation cutting was studied using an intensified ultra highspeed camera in order to get useful insights into the cutting process.

Ullmann, F.; Loeschner, U.; Hartwig, L.; Szczepanski, D.; Schille, J.; Gronau, S.; Knebel, T.; Drechsel, J.; Ebert, R.; Exner, H.

2013-02-01

93

Laser Ablation of Biological Tissue Using Pulsed CO2 Laser  

NASA Astrophysics Data System (ADS)

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO2 laser (wavelength: 10.6 ?m pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

2010-10-01

94

Ultraviolet-laser ablation of skin  

Microsoft Academic Search

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

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

1985-01-01

95

Laser ablation threshold of cultural heritage metals  

Microsoft Academic Search

The present work has the purpose to evaluate experimentally the ablation threshold fluences of copper, silver, and their alloys in order to induce a safety laser cleaning of the metal artifacts avoiding damages to the bulkE We used two different pulsed lasers: a KrF excimer laser operating at 248 nm, 23 ns pulse duration and a Nd:YAG laser operating at

A. Lorusso; V. Nassisi; A. Buccolieri; G. Buccolieri; A. Castellano; L. S. Leo; M. di Giulio; L. Torrisi; F. Caridi; A. Borrielli

2008-01-01

96

Basic Physics of Femtosecond Laser Ablation  

Microsoft Academic Search

Laser ablation being the basic process for many prominent applications of lasers in present day high technology, medicine,\\u000a and other fields, its basic physics is reviewed in this chapter. In order to distinguish the fundamental, laser–material interaction\\u000a from the secondary effects, we concentrate on ultrashort laser pulses (???100?fs duration) at comparably low intensities,\\u000a below the commonly indicated threshold for massive

Juergen Reif

97

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

PubMed

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

Shrestha, Bindesh; Vertes, Akos

2014-05-01

98

Laser ablation in analytical chemistry—a review  

Microsoft Academic Search

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

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

2002-01-01

99

Ablation de matériaux par laser femtoseconde  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

100

Pulsed Laser Deposition — Ablation Mechanism and Applications  

NASA Astrophysics Data System (ADS)

Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough. In general, the method of pulsed laser deposition (PLD) is simple. Only few parameters need to be controlled during the process. Targets used in PLD are small compared with other targets used in other sputtering techniques. It is quite easy to produce multi-layer film composed of two or more materials. Besides, by controlling the number of pulses, a fine control of film thickness can be achieved. Pulsed-laser deposition has been used to deposit an extraordinarily wide range of materials. Historically, the most significant application of PLD has been in the area of high temperature superconducting thin films. The demonstration that PLD could be used to deposit YBa2Cu3O7-x (YBCO) films with zero resistivity at nearly 85 K sparked a significant amount of high temperature superconductivity research over the past decade and has stimulated research in PLD in general. The most striking limitations of PLD are the generation of particulates during the deposition process and the non uniform coating thickness, when substrates of large area are deposited.

Rao, M. C.

101

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

102

Feasibility of depth profiling of animal tissue by ultrashort pulse laser ablation.  

PubMed

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

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

2012-05-01

103

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

104

Ultrafast microscopy of laser ablation of refractory materials: ultra low threshold stress-induced ablation  

Microsoft Academic Search

The fundamental mechanisms of photothermal laser ablation of thin films of refractory materials on glass are investigated, using time-resolved microscopy with variable duration ablation pulses (1ns–10?s). A fundamental understanding of ablation mechanisms can be used to develop designer materials with ultra efficient ablation, i.e. materials that can be ablated using economical low power laser sources. Refractory Ti and TiN thin

Serguei G. Koulikov; Dana D. Dlott

2001-01-01

105

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

106

Femtosecond laser lithotripsy: feasibility and ablation mechanism  

NASA Astrophysics Data System (ADS)

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (?=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 ?m, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 ?m, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

Qiu, Jinze; Teichman, Joel M. H.; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D.; Chan, Kin Foong; Milner, Thomas E.

2010-03-01

107

Quantifying the quality of femtosecond laser ablation of graphene  

NASA Astrophysics Data System (ADS)

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

Sahin, Ramazan; Akturk, Selcuk; Simsek, Ergun

2014-06-01

108

Laser ablated hard coating for microtools  

DOEpatents

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

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

1998-05-05

109

Laser ablated hard coating for microtools  

DOEpatents

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

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

1998-05-05

110

Efficient lasing in continuous wave and graphene Q-switched regimes from Nd:YAG ridge waveguides produced by combination of swift heavy ion irradiation and femtosecond laser ablation.  

PubMed

We report on the continuous wave and passively Q-switched lasers in Nd:YAG ridge waveguides fabricated by a combination of swift Kr ion irradiation and femtosecond laser ablation. Owing to the deep penetration length (~50 ?m) of 670 MeV Kr8+ ions into the crystal, ridge waveguides with large-area cross section, supporting nearly symmetric guiding modes, were produced. Continuous wave lasers with maximum 182 mW output power at ~1064 nm have been realized at 808-nm optical pump. Using graphene as a saturable absorber, passively Q-switched waveguide laser operations were achieved. The pulsed laser produces 90 ns pulses, with a ~4.2 MHz repetition rate, 19% slope efficiency and 110 mW average output power, corresponding to single-pulse energy of 26.5 nJ. PMID:24921487

Jia, Yuechen; Tan, Yang; Cheng, Chen; Vázquez de Aldana, Javier R; Chen, Feng

2014-06-01

111

Kilohertz laser ablation for doping helium nanodroplets  

SciTech Connect

A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the nonvolatile DNA basis guanine is found to be efficient and a number of oligomers are detected.

Mudrich, M.; Forkl, B.; Mueller, S.; Dvorak, M.; Buenermann, O.; Stienkemeier, F. [Physikalisches Institut, Universitaet Freiburg, D-79104 Freiburg (Germany)

2007-10-15

112

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

113

Laser ablation of gall bladder stones  

NASA Astrophysics Data System (ADS)

Study of laser interaction with calculi is presented. A system of Nd-Yag and Ho-Yag pulsed lasers were used to produce fluorescence and plasma signals at the stone surface surrounded by saline and bile fluids. Fourth harmonic from Nd-Yag laser was transmitted to the samples by graded UV optical fibres. Gall bladder stones of various compositions were subjected to the high power Ho-Yag laser. Temporal transients and spectral evolution of plasma and fluorescence signals were monitored by a streak camera. A profile of acoustic pressures generated by shock waves was recorded with sensitive hydrophones placed in the surrounding fluids. Ablation threshold, cavitation process and fluorescence dependence on the laser parameters were studied in detail. Potential of stone identification by fluorescence and possible hydrodynamic model for ablation of biological samples is discussed.

Marafi, M.; Makdisi, Y.; Bhatia, K. S.; Abdulah, A. H.; Kokaj, Y.; Mathew, K.; Quinn, F.; Qabazard, A.

1999-06-01

114

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

115

Hydroxyapatite coatings deposited by laser-assisted laser ablation method  

Microsoft Academic Search

Application of a new hydroxyapatite coating method called the laser-assisted laser ablation method improves adhesion due to irradiation by an assist laser beam for optical annealing. In this study, substrate immersion in a simulated body fluid was performed to confirm the biocompatibility of the technique. The coatings contained a significant quantity of amorphous calcium phosphates. The amorphous phase was dissolved

Masahito Katto; Masahiro Nakamura; Toshiharu Tanaka; Takeyoshi Nakayama

2002-01-01

116

Femtosecond laser ablation of bovine cortical bone.  

PubMed

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. PMID:23208295

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

2012-12-01

117

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

118

A unified model in the pulsed laser ablation process  

NASA Astrophysics Data System (ADS)

In this unified model, we introduce the electron-phonon coupling time ( t ie ) and laser pulse width ( t p ). For long pulses, it can substitute for the traditional thermal conduction model; while for ultrashort pulses, it can substitute for the standard two-temperature model. As an example of the gold target, we get the dependence of the electron and ion temperature evolvement on the time and position by solving the thermal conduction equation using the finite-difference time-domain (FDTD) method. It is in good agreement with experimental data. We obtain the critical temperature of the onset of ablation using the Saha equation and then obtain the theoretical value of the laser ablation threshold when the laser pulse width ranges from nanosecond to femtosecond timescale, which consists well with the experimental data.

Hu, De-Zhi

2008-07-01

119

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

SciTech Connect

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

Geohegan, D.B.

1994-09-01

120

Picosecond laser ablation of transparent materials  

NASA Astrophysics Data System (ADS)

Processing of thin and ultra-thin glass displays is becoming more important in the fast increasing market of display manufacturing. As conventional technologies such as mechanical scribing followed by manual breaking mostly lead to bad edge quality and thus to a huge amount of reject, other processes like ablation processes [1] with picosecond lasers are getting more and more interesting. However processing with ultrashort pulsed lasers partially leads to unwanted effects which should be understood in a better way by means of intensive basic research. Therefore the ablation mechanism of ultrashort pulses on transparent materials was investigated in this research project. On the one hand the ablation mechanism was analyzed in a simulative way by means of rate equations on the other hand by laboratory experiments.

Russ, Simone; Siebert, Christof; Eppelt, Urs; Hartmann, Claudia; Faißt, Birgit; Schulz, Wolfgang

2013-03-01

121

Dynamical modeling of laser ablation processes  

SciTech Connect

Several 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; gas dynamic, hydrodynamic, and collisional descriptions of plume transport; and molecular dynamics models of the interaction of plume particles with the deposition substrate. The complexity of the phenomena involved in the laser ablation process is matched by the diversity of the modeling task, which combines materials science, atomic physics, and plasma physics.

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

1995-09-01

122

Surface properties of femtosecond laser ablated PMMA.  

PubMed

The effects of femtosecond laser ablation on the physical and chemical properties at the surface of poly methylmethacrylate (PMMA) were studied. Femtosecond laser microfabrication caused the initially wetting behavior of PMMA to become nonwetting, mainly because of the laser-induced surface porosity at the submicroscale. Static and dynamic contact angle measurements along with morphological characterization revealed that after the laser irradiation, the system lies in an intermediate regime between those theorized by Wenzel and Cassie-Baxter. Spectroscopic analysis did not evidence any significant variation in the chemical properties of the processed polymeric surfaces. PMID:20735111

Marco, Carmela De; Eaton, Shane M; Suriano, Raffaella; Turri, Stefano; Levi, Marinella; Ramponi, Roberta; Cerullo, Giulio; Osellame, Roberto

2010-08-01

123

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

Microsoft Academic Search

Mass spectrometric analysis of biomolecules under ambi- ent conditions promises to enable the in vivo investiga- tion of diverse biochemical changes in organisms with high specificity. Here we report on a novel combination of infrared laser ablation with electrospray ionization (LAESI) as an ambient ion source for mass spectrometry. As a result of the interactions between the ablation plume and

Peter Nemes; Akos Vertes

2007-01-01

124

Reactions of Laser-Ablated Metal Atoms.  

National Technical Information Service (NTIS)

Laser-ablated boron atoms react with methyl fluoride in an argon stream to form two major products, CH2BF and CHBF. In similar reactions of boron with methyl chloride and methyl bromide, both CH2BX and CHBX are also observed, as well as the primary insert...

L. Andrews

2000-01-01

125

NOVEL LASER ABLATION TECHNOLOGY FOR SURFACE DECONTAMINATION  

EPA Science Inventory

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

126

Laser ablation investigations for future microthrusters  

NASA Astrophysics Data System (ADS)

Low thrust engines with high specific impulse and long lifetime that allow for precise distance control in satellite formation flight and compensation of small disturbing forces become increasingly important in missions for geodetic purposes or astronomic science. Currently available microthrusters cannot yet meet these demands. Laser ablative micropropulsion is a relatively new concept that has already proven its potential for providing very small impulse bits and high specific impulses. Additionally, by using electro-optic beam control even the most stringent conditions like "no moving parts" could be met. An overview of the experimental facilities for characterization of the ablation process and future plans for the experimental setups are presented. In a first step, laser ablation of metal targets in a vacuum vessel using short pulse solid state laser sources is investigated. In this paper we present first results on Faraday cup and profilometry measurements and discuss their impact on further investigations of plume characteristics. Future experimental goals as well as DLR's research strategy for the development of precise and reliable laser ablation microthrusters are addressed.

Karg, Stephanie; Scharring, Stefan; Eckel, Hans-Albert

2012-07-01

127

Laser ablation and cryotherapy of melanoma metastases.  

PubMed

Both laser therapy and cryotherapy have been used with good results in the ablation of cutaneous melanoma metastases. There is less literature evidence in support of cryotherapy. Carbon dioxide laser therapy is a simple, low cost, patient-friendly technique, effective for palliation of individual lesions. There is evidence of a more profound regional effect, with unexplained absences of recurrence at treated sites and reported complete remissions, which demands further investigation. PMID:24249157

John, Hannah E; Mahaffey, Peter J

2014-03-01

128

Plasma chemistry in laser ablation processes  

Microsoft Academic Search

Based on the results of quantitative spectroscopic diagnostics (LIF in combination with time resolved emission spectroscopy) chemical dynamics in laser-produced plasmas of metallic (Ti, Al,), and graphite samples have been examined. The Nd-YAG (1064 nm, 10 ns, 100 mJ) and excimer XeCl (308 nm, 10 ns, 10 mJ) lasers were employed for ablation. The main attention was focused on the

V. S. Burakov; N. V. Tarasenko; N. A. Savastenko

2001-01-01

129

Laser surface ablation cleaning of nuclear facilities  

Microsoft Academic Search

High power Nd:YAG laser beam with wavelength 1064nm, pulsewidth 10 picosecond regime was focused onto the scanning targets of SUS304 stainless steel with Zn coating of thickness 21 micrometers , and delivered via a step index fused silica optical fiber of length 3m and core diameter 1mm. Irradiation ablation effect and some basic aspects of high power laser beam transporting

Xianglin Zhou; Kazuo Imasaki; Hideo Umino; Kohji Sakagishi; Sadao Nakai; Chiyoe Yamanaka

2000-01-01

130

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

131

Laser ablation mechanism of transparent dielectrics with picosecond laser pulses  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

132

Wavelength dependence of soft tissue ablation by using pulsed lasers  

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

133

A Review of Laser Ablation Propulsion  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

134

A Review of Laser Ablation Propulsion  

SciTech Connect

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

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

2010-10-08

135

Laser plasma interaction at an early stage of laser ablation  

Microsoft Academic Search

Laser scattering and its interaction with plasma during KrF excimer laser ablation of silicon are investigated by ultrafast phototube detection. There are two peaks in an optical signal with the first peak attributed to laser scattering and the second one to plasma generation. For laser fluence above 5.8 J\\/cm2, the second peak rises earlier to overlap with the first one.

Y. F. Lu; M. H. Hong; T. S. Low

1999-01-01

136

Ablation Plasma Ion Implantation Optimization and Deposition of Compound Coatings  

NASA Astrophysics Data System (ADS)

Ablation Plasma Ion Implantation (APII) utilizes KrF laser ablation plasma plumes to implant ions into pulsed, negatively-biased substrates [1]. Ablation targets are Ti foils and TiN disks. Substrates are Si wafers and Al, biased from 0 to -10 kV. Optimization experiments address: 1) configurations that reduce arcing, 2) reduction of particulate, and 3) deposition/implantation of compounds (e.g. TiN). Arcing is suppressed by positioning the target perpendicular (previously parallel) to the substrate. Thus, bias voltage can be applied at the same time as the KrF laser, resulting in higher ion current. This geometry also yields lower particulate. APII with TiN has the goal of hardened coatings with excellent adhesion. SEM, AFM, XPS, TEM, and scratch tests characterize properties of the thin films. Ti APII films at - 4kV are smoother with lower friction. 1. B. Qi, R.M. Gilgenbach, Y.Y. Lau, M.D. Johnston, J. Lian, L.M. Wang, G. L. Doll and A. Lazarides, APL, 78, 3785 (2001) * Research funded by NSF

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

2002-10-01

137

Small glass particle cloud generation induced by laser ablation  

Microsoft Academic Search

Burst of small fragments of glass has been evidenced in the present study, when ground glass surface is laser ablated. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of metal or polymer ablation. In this case, no additional metal coating has been made to further

Kunihito Nagayama; Yuriko Kotsuka; Motonao Nakahara; Shiro Kubota

2005-01-01

138

Specific Impulse Definition for Ablative Laser Propulsion  

NASA Technical Reports Server (NTRS)

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

Herren, Kenneth A.; Gregory, Don A.

2004-01-01

139

[Laser ablation. Do we still need it?].  

PubMed

Laser ablation (LA) is momentarily the only invasive ablation procedure besides radiofrequency ablation (RFA) which can be performed entirely under magnetic resonance imaging (MRI) guidance. The long-term outcome and morbidity profiles are broadly identical for both modalities, excluding the RFA-specific prevalence for skin burns. The technical and logistic disadvantages of LA have been overcome since the introduction of miniaturized two-component applicators. The main advantage of LA is its superior MRI compatibility. Interference-free imaging during LA allows MR thermometric real-time therapy control without the need for RF filters. High-resolution thermometry in the target zone only makes sense without the extinction artifact of a metal probe and this condition is met only by the glass fibers of LA. An independent therapy monitoring is crucial in modern scenarios of oncologic quality management. PMID:22249697

Rosenberg, C; Hoffmann, C O M; Mensel, B; Puls, R; Hosten, N

2012-01-01

140

Surface cleaning by laser ablation.  

National Technical Information Service (NTIS)

Nd:YAG laser cleaning of metal oxides from 304L stainless steel surfaces has been characterized. Thin chromium oxide films can be completely removed from the surface using a single 10 nsec pulse of laser radiation with an average surface irradiance greate...

H. C. Peebles N. A. Creager D. E. Peebles

1991-01-01

141

Experimental research of two-wavelength laser ablation biological tissue  

NASA Astrophysics Data System (ADS)

Laser ablation biologic tissue is an important performance of laser application. Based on the combination function of two-wavelength laser to biologic tissue ablation, the semi-continuous two-wavelength laser at 532nm and 1064nm ablating blood tissue was investigated by experiment. The fresh pork and pig liver specimens were ablated at different laser power density and different laser power proportion in water conditions and ablation depth and thermo-damage thickness were measured. The experiment results indicate that there is no effective ablation but deeper thermo-damage of the 1064 nm laser to biologic tissue in water conditions when the 532nm laser power is little but the ablation efficiency sharp inc- reases and the thermo-damage sharp decreases when the 532nm laser power arrives to a threshold. The combination function of two wavelength laser to tissue ablation is appeared here. It indicates that the ablation efficiency and hemostatic function in laser surgery can be adjusted by the two-wavelength laser power proportion.

Yao, Yucheng; Huang, Chuyun; He, Yanyan; Chen, Xia

2009-08-01

142

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

143

Modeling CO2 Laser Ablative Impulse with Polymers  

NASA Astrophysics Data System (ADS)

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 CO2 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 CO2 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.; Phipps, Claude R.; Sasoh, Akihiro

2010-10-01

144

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

Microsoft Academic Search

A laser ablation-miniature mass spectrometer (LA-MMS) for the chemical and isotopic measurement of rocks and minerals is described. In the LA-MMS method, neutral atoms ablated by a pulsed laser are led into an electron impact ionization source, where they are ionized by a 70 eV electron beam. This results in a secondary ion pulse typically 10-100 mus wide, compared to

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

2011-01-01

145

Quasi-steady expansion of plasma ablated from laser-irradiated pellets  

Microsoft Academic Search

The ablative, quasi-steady expansion of the spherical coronal plasma produced by irradiating an overdense pellet by a high-intensity laser pulse, is studied for large ion charge number Z\\/sub i\\/. The entire structure of the flow and its changes as the laser power is increased, are determined. The instantaneous power W required to generate a given ablation pressure P\\/sub a\\/ and

J. Sanz; A. Liñán; M. Rodríguez; J. R. Sanmartín

1981-01-01

146

Femtosecond, picosecond and nanosecond laser ablation of solids  

Microsoft Academic Search

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

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

1996-01-01

147

Characterization of laser ablation plasmas by laser beam deflection  

Microsoft Academic Search

Laser probe beam and multiple-pass deflection techniques were used for real time and in situ monitoring of laser ablation plasma plumes in the mTorr pressure regime. Intensity and transit time of shock wave fronts were studied as functions of focal lens position, laser energy and pressure. The velocity of the shock wave was determined to be up to 30kms?1 for

C. Sánchez Aké; H. Sobral; M. Villagrán Muniz; L. Escobar-Alarcon; E. Camps

2003-01-01

148

Analysis of metallic fuels by laser ablation  

NASA Astrophysics Data System (ADS)

A hot cell-based solid sampling system has been developed for application to the analyses of irradiated materials such as metallic reactor fuel from a nuclear reactor, and radioactive waste forms. This system employs one of two sampling techniques, glow discharge or laser ablation, for introduction of material into one of two instruments for analysis, either a time of flight mass spectrometer or an inductively coupled argon plasma-atomic emission spectrometer (ICP-AES). This paper will discuss using ICP-AES for the analysis of major, minor and trace constituents in an unirradiated U-10 wt % Zr metallic reactor fuel. The behavior of highly refractory elements, such as Zr, in the laser ablation process will be examined in detail. Additional corroborative data provided via scanning electron microscopy-energy dispersive x-ray fluorescence spectroscopy (SEM-EDS) will be presented.

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

1995-04-01

149

Photopolymers designed for laser ablation - photochemical ablation mechanism  

NASA Astrophysics Data System (ADS)

We have designed photopolymers based on a photolabile chromophore with absorption properties tailored for a specific irradiation wavelength. The introduction of the two photolabile groups (-N?N-N?) into one repetition unit of the main polymer chain results in a well-defined decomposition pathway. The exothermic decomposition mechanism yields high energetic, gaseous products, which are not contaminating the polymer surface. The products of laser ablation were studied with time-of-flight mass spectroscopy (TOF-MS). All products are totally compatible with a photochemical decomposition mechanism and their high energies can be explained by a laser induced microexplosion. Time resolved techniques, such as transmission, reflectivity or surface interferometry, revealed a `dynamic' behavior. Ns-interferometry showed that etching of the polymer nearly starts and ends with the laser pulse. During the initial stages of the irradiation, darkening of the surface was detected, which corresponds to a decrease of reflectivity and an increase of transmission. This is due to a decrease of the refractive index and absorption coefficient, caused by the photodecompostion of the polymer starting with the irradiation pulse.

Lippert, Thomas; Dickinson, J. T.; Langford, S. C.; Furutani, H.; Fukumura, H.; Masuhara, H.; Kunz, T.; Wokaun, A.

1998-05-01

150

KTP-532 laser ablation of urethral strictures  

NASA Astrophysics Data System (ADS)

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

Malloy, Terrence P.

1991-07-01

151

Nickel plasma produced by 532-nm and 1064-nm pulsed laser ablation  

NASA Astrophysics Data System (ADS)

A comparison between laser ablation of nickel in vacuum by using 532-and 1064-nm Nd:YAG (Yttrium Aluminium Garnet) laser wavelengths, with an intensity of 5 × 109 W/cm2, is reported. Nanosecond pulsed ablation produces high nonisotropic emission of neutrals and ionic species. For 532-nm laser irradiation, mass quadrupole spectrometry, coupled to electrostatic ion deflection and time-of-flight measurements, allows estimation of the energy distributions of the emitted species from plasma. For 1064-nm laser ablation, a cylindrical electrostatic ion analyzer permits one to measure the yield and the charge state of the emitted ions and reconstruct the ion energy and charge state distributions. Neutrals show typical Boltzmann-like distributions, while ions show Coulomb-Boltzmann-shifted distributions depending on their charge state. Surface profiles of the ablated craters permitted study of the ablation threshold and yields of nickel in vacuum versus the laser fluence. The plasma temperature was evaluated using experimental data. Special regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated at nonequilibrium plasma conditions and the angular distribution of the emitted species.

Torrisi, L.; Caridi, F.; Margarone, D.; Giuffrida, L.

2008-07-01

152

Solar cell contact formation using laser ablation  

SciTech Connect

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

Harley, Gabriel; Smith, David; Cousins, Peter

2012-12-04

153

Properties of zirconia thin films deposited by laser ablation  

NASA Astrophysics Data System (ADS)

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

Cancea, V. N.; Filipescu, M.; Colceag, D.; Mustaciosu, C.; Dinescu, M.

2013-11-01

154

CO2 Laser Absorption in Ablation Plasmas  

SciTech Connect

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

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

2006-05-02

155

Nanosecond and femtosecond excimer laser ablation of fused silica  

Microsoft Academic Search

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

J. Ihlemann; B. Wolff; P. Simon

1992-01-01

156

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

157

Ionization and fragmentation of solid C60 by femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

Ionization and fragmentation of solid C60 dispersed on a silicon plate are investigated by femtosecond laser ablation. Bimodal mass distribution with large fragment ions C60-2n+ (0<=n<=11) and small fragment ions Cn+ (13<=n<=28), formation of dimer ion (C60)2+, and delayed ionization of C60 have been observed as reported in gas phase experiments with nanosecond laser excitation. Metastable dissociation of small fragment ions Cn+ has been observed for the first time, which suggests different structures of fragment ions compared with those of well-studied carbon cluster ions. From these observations, strong coupling of laser energy to electronic degrees of freedom of solid C60 has been revealed for femtosecond laser ablation as compared with excitation in the gas phase.

Kobayashi, T.; Kato, T.; Matsuo, Y.; Kurata-Nishimura, M.; Kawai, J.; Hayashizaki, Y.

2007-02-01

158

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

NASA Astrophysics Data System (ADS)

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

Takeda, Yoshihiro; Mafuné, Fumitaka

2014-04-01

159

Ablation dynamics in laser sclerotomy ab externo  

NASA Astrophysics Data System (ADS)

Laser sclerostomy ab externo with flashlamp excited mid-IR laser systems emitting in the 2-3 micrometer spectral range is in phase II clinical trials. Although acutely high success rates were achieved, the restenosis rate after several months is about 40%. Laser pulses of several hundreds of microseconds, known to induce thermo-mechanical explosive evaporation were used for this procedure. We investigated the ablation dynamics in tissue and the cavitation bubble dynamics in water by means of an Er:YAG laser system to estimate the extent of mechanical damage zones in the sclera and in the anterior chamber, which may contribute to the clinical failure. We found substantial mechanical tissue deformation during the ablation process caused by the cavitation effects. Stress waves up to several bar generated by explosive evaporization were measured. The fast mechanical stretching and collapsing of the scleral tissue induced by cavitation resulted in tissue dissection as could be proved by flash photography and histology. The observed high restenosis might be a result of a subsequent enhanced wound healing process. Early fistula occlusions due to iris adherences, observed in about 20% of the clinical cases may be attributed to intraocular trauma induced by vapor bubble expansion through the anterior chamber after scleral perforation. An automatic feedback system minimizing adverse effects by steering and terminating the laser process during scleral fistulization is demonstrated. Moreover, a new approach in laser sclerostomy ab externo is presented using a cw-IR laser diode system emitting at the 1.94 micrometer mid-IR water absorption peak. This system was used in vitro and showed smaller damage zones compared to the pulsed laser radiation.

Brinkmann, Ralf E.; Droege, Gerit; Mohrenstecher, Dirk; Scheu, M.; Birngruber, Reginald

1996-01-01

160

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

National Technical Information Service (NTIS)

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 inte...

R. A. Lindley

1993-01-01

161

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

162

Vapor breakdown during ablation by nanosecond laser pulses  

SciTech Connect

Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. Although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no attempts made on vapor breakdown by nanosecond laser pulses. This work intends to fill the gap. A kinetic model is developed considering following factors: (1) two temperatures of both electrons and heavy-body particles (ions, neutrals, and excited states of neutrals), (2) absorption mechanisms of laser energy include inverse bremstrahlung (IB) processes and photoionization of excited states, (3) ionization acceleration mechanisms included are electron-impact excitation of ground state neutrals, electron-impact ionization of exited states of neutrals, photoionization of excited states of neutrals, and all necessary reverse processes. The rates of various processes considered are calculated according to the formula given by Zel`dovich and Raizer. The authors use a second order predictor-corrector numerical scheme for iterations of the rate equations. The rate equations are solved for five quantities, namely, densities of electrons, neutrals, and excited states of neutrals, and the temperatures of electrons and heavy-body particles. The total breakdown times (sum of evaporation time and vapor breakdown time) at different energy fluences are then calculated. The results are compared with experimental observations of Si target ablation using a KrF laser. A more detailed description of the model and the results will be published later.

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

1995-04-01

163

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 exp 14 W/cm exp 2 ), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arra...

J. Grun

1981-01-01

164

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

SciTech Connect

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

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

2013-08-15

165

Elemental fractionation and stoichiometric sampling in femtosecond laser ablation  

Microsoft Academic Search

Elemental fractionation in femtosecond laser ablation is studied by ICP-MS by applying successive single laser shots to binary metallic and semiconductor samples as well as to multi-component glasses. Fractionation can be observed in the first laser shots in particular if the laser fluence is near the ablation threshold of the sample. However, the element ratio in the laser-sampled masses changes

Carmen C. Garcia; Helmut Lindner; Alex von Bohlen; Cedomil Vadla; Kay Niemax

2008-01-01

166

Spectroscopic characterization of laser ablated silicon plasma  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

167

Fabricating atom chips with femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We report on the microfabrication of atom chips using a femtosecond laser ablation technique to arbitrarily sculpture both thin conductive metal films and permanent magnetic materials. We have measured the threshold fluences for a variety of materials relevant to atom chip development (Au, Ag, Cu, Cr, Ni, TbGdFeCo, SmCo, CoCr). The quality of the ablation process is investigated by extracting the power spectral density of the edge roughness from composite scanning electron microscope images and through the use of a magnetoresistance microscope to measure the associated magnetic field noise. Finally, we present results from a sculptured wire which produces an array of tunable double wells designed for near-surface force sensing with Bose-Einstein condensates.

Wolff, C. H.; Whitlock, S.; Lowe, R. M.; Sidorov, A. I.; Hall, B. V.

2009-04-01

168

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

169

A spectroscopic study of laser ablation plasma from Mo target  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

170

Energy balance in laser ablation of metal targets  

SciTech Connect

Laser-generated plasma was induced on metallic targets glued to a piezoelectric microphone and placed between the plates of a planar charged capacitor. The plasma generates a temporal redistribution of electric charge on the plates that can easily be measured by a resistor connected to the ground plate; this signal is proportional to the total number of ions removed by breakdown. Both the absorbed and scattered energies were simultaneously monitored by the photoacoustic signal and an energy meter. From these signals it was possible to determine the energy involved in each of the processes. Just above the ablation threshold most of the delivered energy is absorbed and the acoustic signal prevails compared to other contributions. Above this region, the electric signal, which is proportional to the energy involved in the ablation process, becomes dominant.

Sobral, H.; Villagran-Muniz, M.; Bredice, F. [Laboratorio de Fotofisica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-186, Mexico Distrito Federal, Codigo Postal 04510 (Mexico); Centro de Investigaciones Opticas, P.O. Box 124, Codigo Postal 1900, La Plata (Argentina)

2005-10-15

171

Effects of pressure rise on cw laser ablation of tissue  

NASA Astrophysics Data System (ADS)

The objectives of this research were to identify mechanisms responsible for the initiation of continuous wave (cw) laser ablation of tissue and investigate the role of pressure in the ablation process. Porcine aorta samples were irradiated in a chamber pressurized from 1 X 10-4 to 12 atmospheres absolute pressure. Acrylic and Zn-Se windows in the experimental pressure chamber allowed video and infrared cameras to simultaneously record mechanical and thermal events associated with cw argon laser ablation of these samples. Video and thermal images of tissue slabs documented the explosive nature of cw laser ablation of soft biological media and revealed similar ablation threshold temperatures and ablation onset times under different environmental pressures; however, more violent initiation explosions with decreasing environmental pressures were observed. These results suggest that ablation initiates with thermal alterations in the mechanical strength of the tissue and proceeds with an explosion induced by the presence superheated liquid within the tissue.

LeCarpentier, Gerald L.; Motamedi, Massoud; Welch, Ashley J.

1991-06-01

172

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

173

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

NASA Astrophysics Data System (ADS)

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 and electron number density of the laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-induced plasmas decreased faster than ns-induced 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 were compared.

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

2005-02-01

174

Numerical study on propulsion properties of laser ablated polymer target  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

175

Parametric study on femtosecond laser pulse ablation of Au films  

NASA Astrophysics Data System (ADS)

Ablation process of 1 kHz rate femtosecond lasers (pulse duration 148 fs, wavelength 775 nm) with Au films on silica substrates has been systemically studied. The single-pulse threshold can be obtained directly. For the multiple pulses the ablation threshold varies with the number of pulses applied to the surface due to the incubation effect. From the plot of accumulated laser fluence N × ?th( N) and the number of laser pulses N, incubation coefficient of Au film can be obtained ( s = 0.765). As the pulse energy is increased, the single pulse ablation rate is increasing following two ablation logarithmic regimes, which can be explained by previous research.

Ni, Xiaochang; Wang, Ching-yue; Yang, Li; Li, Jianping; Chai, Lu; Jia, Wei; Zhang, Ruobing; Zhang, Zhigang

2006-11-01

176

Focal laser ablation for localized prostate cancer.  

PubMed

Throughout history, medicine has witnessed paradigm shifts that significantly change patient treatment. In surgical oncology, the introduction of lumpectomy revolutionized breast cancer treatment while partial nephrectomy has altered the management of kidney cancer. In both cases, organ preservation is combined with efficacious management of the cancer via a less invasive approach. Within urology, prostate cancer (PCa) may be the next to benefit from such a treatment paradigm. Current management of PCa involves either whole organ treatment, with the inherent side effects, while selected patients are eligible for active surveillance. Focal therapy offers a middle ground for low-risk patients with PCa, again using the principles of a minimally invasive treatment of the cancer, in this case using an energy source with few side effects, combined with maximal organ preservation. Because focal therapy for PCa is still in evolution, there is no consensus on the ideal energy source that should be used to ablate the PCa, imaging to monitor the tissue destruction in real time, how many treatments may be offered, and the ideal follow-up regimen. Long-term follow-up of patients is needed before it is recommended as a first-line treatment. Nevertheless, evidence is accumulating that radically treating PCa holds survival benefit for patients; however, the number of men needed to treat is considerable, with significant side effects; thus, more centers are investigating focal therapy as an option. This review focuses on the use of the laser as the energy source for focal ablation, while bringing historically relevant information regarding laser energy and highlighting the perceived advantageous of focal laser ablation. PMID:20477544

Lindner, Uri; Lawrentschuk, Nathan; Trachtenberg, John

2010-05-01

177

Structure and Scaling Laws of Laser-Driven Ablative Implosions.  

National Technical Information Service (NTIS)

A stationary, spherical flow model gives the form of laser-driven ablation fronts and scaling laws for the dependence of implosion parameters on laser wavelength, pusher atomic number, and other input quantities.

S. J. Gitomer R. L. Morse B. S. Newberger

1975-01-01

178

Germanium dioxide whiskers synthesized by laser ablation  

NASA Astrophysics Data System (ADS)

We obtained germanium dioxide (GeO2) whiskers in bulk quantity by ablating a germanium target at 820 °C with a pulsed KrF excimer laser in an argon atmosphere. Most of the GeO2 whiskers were smooth and straight with hexagonal or triangular, or quadrilateral cross sections while some of them had a bamboo-shoot-shaped form. Results of scanning electron microscopy, transmission electron microscopy, and x-ray diffraction showed that the whiskers are hexagonal crystalline GeO2.

Tang, Y. H.; Zhang, Y. F.; Wang, N.; Bello, I.; Lee, C. S.; Lee, S. T.

1999-06-01

179

Diamond-like carbon deposited by femtosecond pulsed-laser ablation: evidence of nanocrystalline diamond  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation is a well-known technique used for thin film deposition, extending from oxydes to hard and wear resistant Diamond-Line Carbon (DLC) films. Most of the previous studies devoted to DLC thin films elaboration have used pulsed duration in the nanosecond range. The present study concerns femtosecond (10-15 s range) laser ablation of a graphite target for the elaboration of Diamond-Like Carbon. Compared to conventional nanosecond laser ablation, femtosecond laser pulses allow the production of high energy (up to a few keV) ions in the plasma, which may strongly affect the structure and properties of the deposited films. DLC films have been deposited under vacuum onto (100) p-type silicon substrates at room temperature, by ablating graphite targets with femtosecond laser pulses. The nature and properties of the film have been characterized by various techniques, including Raman, XPS and AFM. Discussion will be focused on the comparison between present results obtained using femtosecond laser pulses, with previously published results related to DLC films deposited using nanosecond laser pulses. Especially, Raman spectra of DLC films obtained by nanosecond laser ablation always show the two well-known D and G bands (located respectively at around 1350 cm-1 and 1550 cm-1), whereas some DLC films obtained when using femtosecond laser pulses exhibit an intense peak at 1140 cm-1, which may be attributed to nanocrystalline diamond.

Garrelie, Florence; Loir, Anne S.; Goutaland, Francois; Donnet, C.; Le Harzic, Ronan; Angleraud, Benoit; Ouerdane, Youcef; Laporte, Pierre

2002-09-01

180

Microlens fabrication in PMMA with scanning excimer laser ablation techniques  

Microsoft Academic Search

Laser ablation is a versatile technique for fabricating microstructures on polymer surfaces. Due to the nature of the process, the fabrication of the microstructure can take place in a very late stage of a heterogeneous assembly. This makes laser ablation very attractive for fabricating micro-optical components on opto-electronic assemblies in comparison to other fabrication techniques like injection molding and embossing.

Kris Naessens; Peter Van Daele

181

Direct optimization of femtosecond laser ablation using adaptive wavefront shaping  

Microsoft Academic Search

We introduce an approach based on using an iterative simulated annealing algorithm to drive the outcome of femtosecond laser ablation towards a specific target shape by using a two-dimensional deformable mirror. Unlike previous work combining adaptive optics and laser machining we use the machining outcome itself as the fitness parameter for the optimization procedure. Single-pulse ablation features with programmable aspect

S Campbell; S M F Triphan; R El-Agmy; A H Greenaway; D T Reid

2007-01-01

182

Acceleration of solid macro-particles by laser produced ablation  

Microsoft Academic Search

The feasibility of accelerating a macroparticle (BB) with laser light is studied. One and two dimensional Lagrangian hydrodynamic calculations are performed using the LASNEX magnetohydrodynamic computer code. The results of these calculations are then used to infer laser intensity, scaling laws for ablation pressure, and mass flow rate. In order to optimize the BB kinetic energy production efficiency, the ablation

T. E. McCann

1978-01-01

183

Investigation of plasma produced by laser and electron pulse ablation  

Microsoft Academic Search

Short laser pulses with high energy are a very promising tool for controlled ablation of materials, both for structurization and for deposition. They are especially suited for the ablation of non-conducting and of complex materials. The plasmas induced by the laser irradiation are distinguished by their high degree of ionization and excitation. A new source with comparable pulse properties is

Th. Witke; A. Lenk; B. Schultrich; C. Schultheiss

1995-01-01

184

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

185

Diagnostics Techniques of Plasmas Produced by Laser Ablation  

SciTech Connect

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.

Villagran Muniz, M.; Sobral, H.; Sanchez Ake, C.; Sangines de Castro, R.; Sterling, E. [Laboratorio de Fotofisica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-186, Mexico D.F. 04510 (Mexico); Bredice, F. [Centro de Investigaciones Opticas, P.O.Box 124, C.P.1900, La Plata (Argentina)

2005-04-21

186

Mechanism study of skin tissue ablation by nanosecond laser pulses  

NASA Astrophysics Data System (ADS)

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

Fang, Qiyin

187

Laser ablation of aluminum from normal evaporation to phase explosion  

NASA Astrophysics Data System (ADS)

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.

2009-05-01

188

Femtosecond laser ablation of brass in air and liquid media  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

189

Femtosecond laser ablation of brass in air and liquid media  

SciTech Connect

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

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

2013-06-07

190

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

191

Laser ablation plume dynamics in nanoparticle synthesis  

SciTech Connect

The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO{sub 2} laser pulse with a duration of {approx}500 {mu}s (at the 0.03 level), energy of 1.0-1.3 J and peak power of 6-7 kW have been studied using high-speed photography of the plume luminescence and shadow. The targets were used to produce nanopowders by laser evaporation. About 200 {mu}s after termination of the pulse, shadowgraph images of the plumes above the YSZ and Nd:YAG targets showed dark straight tracks produced by large particles. The formation of large ({approx}10 {mu}m) particles is tentatively attributed to cracking of the solidified melt at the bottom of the ablation crater. This is supported by the fact that no large particles are ejected from graphite, which sublimes without melting. Further support to this hypothesis is provided by numerical 3D modelling of melt cooling in craters produced by laser pulses of different shapes. (interaction of laser radiation with matter. laser plasma)

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

2009-06-30

192

Proton extraction by laser ablation of transition metals  

NASA Astrophysics Data System (ADS)

A study on the proton beams extraction from a plasma generated by pulsed laser ablation by targets containing transition metals is presented. The targets used were pure disks of titanium and tantalum and disks of TiH2, obtained by compression of TiH2 powder. The plasma was produced by means of a nanosecond excimer KrF laser operating at low irradiance (109-1010 W/cm2). The proton and ions emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. Studies on the produced protons and ions at different laser irradiances from 2 to 15 GW/cm2 were performed. The characterization showed that it is possible to obtain good proton fluxes from these targets, up to 1011 proton/pulse. The results obtained are very interesting if compared with those available in literature where proton fluxes per pulse ranging from 108 to 109 by hydride targets were obtained, at the same laser irradiances.

Velardi, L.; Delle Side, D.; Krása, J.; Nassisi, V.

2014-07-01

193

Laser ablation and plasma interferometry with a tabletop soft x-ray laser  

Microsoft Academic Search

We report the first study of laser ablation and the demonstration of plasma interferometry with a tabletop soft x-ray laser. A capillary discharge pumped Ne-like Ar laser (46.9 nm) was focused using multilayer optics to significantly exceed the energy density necessary for the ablation of metals. Ablation in brass, stainless steel and aluminum samples is reported. The ablation patterns on

Jorge J. Rocca; Jorge Filevich; Mario C. Marconi; A. Ozols; Kelly Kanizay; Brady R. Benware; Juan L. Chilla; Igor A. Artioukov; Yuriy S. Kasjanov; V. V. Kondratenko; Alexander V. Vinogradov

2000-01-01

194

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

SciTech Connect

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

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

2013-10-21

195

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

NASA Astrophysics Data System (ADS)

A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm2. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown.

Autrique, D.; Gornushkin, I.; Alexiades, V.; Chen, Z.; Bogaerts, A.; Rethfeld, B.

2013-10-01

196

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

NASA Astrophysics Data System (ADS)

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

Ray, M. P.; Baldwin, J. W.; Feygelson, T. I.; Butler, J. E.; Pate, B. B.

2011-05-01

197

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

198

Enhanced ablation of human atheroma using a copper vapor laser  

NASA Astrophysics Data System (ADS)

The most suitable type of laser and delivery system for arterial recanalisation remains a matter of controversy. Atheroma demonstrates preferential absorption of laser light relative to normal vessel wall at wavelengths in the region of SOOnm. This phenomenon may be useful in laser angioplasty. A low power commercial quasi-continuous-wave copper vapour laser (CVL) licensed for photodynamic therapy (Oxford Lasers model CUb-A, Oxford, U.K.), emits light at 2 wavelengths - 51mm (green) and 578nm (yellow) [green/yellow ratio 2:1]. This laser may also be used to pump a dye laser producing a tunable output from 530-900nm. The output was coupled to a 1 mm diameter bare quartz optical fiber, and the effects of these wavelengths on atheroma were studied. Perforation thresholds in normal vessel were determined initially. Subsequently, tissue craters were created in sections of normal human femoral artery and in white fibrous atheromatous artery, using a total of 8 J of laser energy delivered with the fiber in contact and perpendicular to the tissue. Crater dimensions were determined histologically in 10 sections from each group, using an optical graticule. Results:- The dye laser pumping produced insufficient power output to achieve tissue ablation. The crater depth, width, and volume, in normal (N) and atheromatous (A) arterial wall achieved with the CVL were statistically compared using a Paired Student's t-test. Crater depth (mm) [mean (s.e.)]: N 0.91 (0.06), A 0.69 (0.05), pablation of atheroma using low power copper vapour laser light is possible. The CVL is an attractive alternative to argon ion laser and its potential application to laser angioplasty merits further study, preferably using a modified optical fibertip delivery system.

Ashley, Simon; Brooks, Stephen G.; Wright, Helena; Gehani, Abdurrazak A.; Rees, Michael R.

1990-07-01

199

UV laser ablation of parylene films from gold substrates  

SciTech Connect

Parylene films, coating gold substrates, were removed by laser ablation using 248 nm light from an excimer laser. Each sample was processed by a different number of pulses in one of three different environments: air at atmospheric pressure, nitrogen at atmospheric pressure, and vacuum. The laser-induced craters were analyzed by optical microscopy and x-ray photoelectron spectroscopy. Multi-pulse ablation thresholds of gold and parylene were estimated.

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

2009-11-19

200

Ablation of polymers by picosecond vibrational laser excitation  

Microsoft Academic Search

Polymers are attractive model materials for mechanistic studies of laser ablation because their vibrational, optical and thermo-mechanical properties are often very well known. We have studied the mechanism of infrared laser ablation in model polymers such as poly(ethylene glycol) (PEG) and poly(styrene) (PS) by resonant and non-resonant vibrational excitation, using a free-electron laser delivering tunable picosecond radiation in a microsecond-long

Michael Papantonakis; J. R. Haglund; Daniel Bubb; James Horwitz

2002-01-01

201

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

202

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

SciTech Connect

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

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

2012-05-15

203

Ablation of crystalline oxides by infrared femtosecond laser pulses  

SciTech Connect

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

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

2006-10-15

204

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

205

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

206

Excimer laser ablation of polycarbonate-based plastic substrates  

Microsoft Academic Search

Ablation of polycarbonate-based plastics under excimer laser irradiation has been studied, with emphasis on the influence of specific inorganic additives in the polymer to the ablation process. Such additives consisted of 0.2 ?m sized, (spherical) TiO2 grains, in either 5% or 10% mass concentration. Irradiation products are analyzed, with respect to roughness and ablation, by scanning electron microscopy, energy dispersive

M. Devalckenaere; A. Jadin; K. Kolev; L. D. Laude

1999-01-01

207

Modeling of stress generation induced by laser ablation  

NASA Astrophysics Data System (ADS)

In the present work we discuss in some details the development of the stress induced into the target by laser ablation in air. The analytical treatment based on the variable energy blast theory allowed to provide the scaling law of the peak and the temporal profile of the generated pressure wave. Measurements of the acoustic transient associated with excimer laser ablation of polyimide, obtained by means of polyvinyldenefloride (PVDF) sensors were successfully compared with the behaviors provided by the analysis. The description here proposed can be extended to pulsed laser ablation of soft tissues where the target material is removed in vapor or gaseous phases.

Siano, Salvatore; Pini, Roberto; Salimbeni, Renzo

1999-06-01

208

Laser ablation dynamics in metals: The thermal regime  

SciTech Connect

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

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

2012-07-02

209

Laser-Ablation Rates Measured Using X-Ray Laser Transmission  

SciTech Connect

The rate of laser ablation at irradiances of {approx}2x10{sup 14} W cm{sup -2} of solid iron has been measured using the transmission of a neonlike zinc x-ray laser at 21.2 nm through thin iron targets. Ablated iron becomes transparent to the x-ray laser flux, enabling the thickness of unablated material and hence the rate of ablation to be measured from time resolved x-ray laser transmission.

Edwards, M. H.; Whittaker, D. S.; Tallents, G. J.; Mistry, P.; Pert, G. J.; Rus, B.; Mocek, T.; Kozlova, M.; Polan, J.; Praeg, A.; Stupka, M.; Homer, P. [Department of Physics, University of York, York, YO10 5DD (United Kingdom); Department of X-ray Lasers, PALS Research Centre, Institute of Physics, Academy of Sciences of the Czech Republic, 182 21 Prague 8 (Czech Republic)

2007-11-09

210

Dynamics of laser ablated colliding plumes  

SciTech Connect

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

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

2013-01-15

211

Carbon nanofoam formed by laser ablation.  

PubMed

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

Kohno, Hideo; Tatsutani, Kentaro; Ichikawa, Satoshi

2012-03-01

212

Tissue interactions and measurement of ablation rates with ultraviolet and visible lasers in canine and human arteries  

SciTech Connect

Ablation rates measured as the depth of tissue excavation per unit time were determined in human and canine aortas subjected to radiation with ultraviolet (UV) excimer (ArF 193 nm, KrF 248 nm, XeF 351 nm) and visible lasers (continuous wave (cw) and 50-ms chopped argon ion, 478 nm-514 nm; pulsed double-frequency Nd:YAG, 532 nm). For UV and pulsed double-frequency Nd:YAG lasers ablation rates were constant in time and depended linearly on average laser power, but for cw and chopped argon lasers ablation rates varied with irradiation time and were nonlinearly dependent on laser power. In human aortas, atherosclerosis without gross calcification had no influence on ablation rates. Charring and tissue disruption were observed with cw and chopped argon ion, whereas excimer and pulsed Nd:YAG lasers produced only minimal injury to surrounding tissue. We conclude that the determination of ablation rates is useful for the selection of laser wavelengths and power densities applicable to angioplasty and that UV and pulsed visible laser permit a better control of ablation compared to continuous wave lasers.

Sartori, M.; Henry, P.D.; Sauerbrey, R.; Tittel, F.K.; Weilbaecher, D.; Roberts, R.

1987-01-01

213

Precision ablation of dental enamel using a subpicosecond pulsed laser.  

PubMed

In this study we report the use of ultra-short-pulsed near-infrared lasers for precision laser ablation of freshly extracted human teeth. The laser wavelength was approximately 800nm, with pulsewidths of 95 and 150fs, and pulse repetition rates of 1kHz. The laser beam was focused to an approximate diameter of 50microm and was scanned over the tooth surface. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain below 5 degrees C when the tooth was air-cooled during laser treatment. The surface preparation of the ablated teeth, observed by optical and electron microscopy, showed no apparent cracking or heat effects, and the hardness and Raman spectra of the laser-treated enamel were not distinguishable from those of native enamel. This study indicates the potential for ultra-short-pulsed lasers to effect precision ablation of dental enamel. PMID:14738125

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

2003-12-01

214

Solid state laser ablation effect on laser-proof composite coating applied in aerospace material  

NASA Astrophysics Data System (ADS)

This paper concentrates on the measurement and analysis of laser ablation effect of particularly prepared aerospace material, polycarbosilane (PCS). Laser ablation experiment setup is designed and built, based on a continuous-wave high-power solid-state laser (CWHPSSL). Steel samples with composite PCS coating are prepared. After that, a group of laser ablation experiment is performed. The samples are shot by laser beam with thousands W/cm2 fluence. The results, including the ablation morphology and temperature data, is shown and discussed. Temperature data gives a good demonstration of thermal protection effect of composite coating, and in the meanwhile the morphological features in the ablated region reveal the principle of PCS laser-proof effect. Theoretical investigation has also been carried out. The temperature field is simulated based on Fourier equation of heat conduction, and the simulation result provides a good demonstration on thermal-proof effect of PCS coating layer during laser ablation process.

Li, Jing; Zheng, Yi; Luo, Jing; Liu, Zhichao; Chen, Songlin; Zhang, Yuzhong; Wang, Zhiyong

2014-02-01

215

In situ Diagnostics During Carbon Nanotube Production by Laser Ablation  

NASA Technical Reports Server (NTRS)

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

Arepalli, Sivaram

1999-01-01

216

A new UHV system for the preparation of carbon stripper foils by laser plasma ablation deposition  

Microsoft Academic Search

Laser plasma ablation of spectroscopically pure graphite under UHV conditions is a well established method for the preparation of thin carbon stripper foils. Such foils with their structure of randomly oriented nanocrystallites can best withstand ion irradiation damage. Accelerator users around the world are interested in this type of carbon stripper foils due to a guaranteed reproducibility, quality, thickness and

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

2004-01-01

217

Selective material ablation by the TEA CO2 laser  

NASA Astrophysics Data System (ADS)

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

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

1995-03-01

218

Imaging of excimer laser vascular tissue ablation by ultrafast photography  

NASA Astrophysics Data System (ADS)

Ablation and tissue removal of normal and atherosclerotic arterial tissue by UV excimer-laser radiation were probed by taking photographs with a dye laser as a flash light-source. The ablating pulses were transmitted through a fused silica fiber into a cuvette with the samples exposed to saline solution. The delay time of the probing dye-laser pulse with respect to the ablating excimer-laser pulse was varied in the nanosecond range up to several hundred microseconds. The ablation process and the resulting plume above the tissue surface were recorded with a CCD camera attached to a PC-based image processing system. All samples under investigation were fresh human cadaver aortic and femoral artery specimens which had been shock-frozen for less than 48 hours. The arterial segments showed different types of lipid-rich and calcified plaques. Big cavitation bubbles and small tissue particles emerging from the irradiated area have been recorded.

Nyga, Ralf; Neu, Walter; Preisack, M.; Haase, Karl K.; Karsch, Karl R.

1991-11-01

219

Peak polarity overturn for charged particles in laser ablation process  

Microsoft Academic Search

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

P. Zhang; Y. J. Ji; X. M. Lai; B. M. Bian; Z. H. Li

2006-01-01

220

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

221

Morphology of femtosecond-laser-ablated borosilicate glass surfaces  

Microsoft Academic Search

We study the morphology of borosilicate glass surface machined by femtosecond laser pulses. Our observations show that a thin rim is formed around ablated craters after a single laser pulse. When multiple laser pulses are overlapped, the crater rims also overlap and produce a surface roughness. The rim appears to be a resolidified splash from a molten layer generated during

Adela Ben-Yakar; Robert L. Byer; Anthony Harkin; Jacqueline Ashmore; Howard A. Stone; Mengyan Shen; Eric Mazur

2003-01-01

222

Cleaning of large area by excimer laser ablation  

Microsoft Academic Search

Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser,

Marc L. Sentis; Philippe C. Delaporte; Vladimir I. Marine; Olivier Uteza

2000-01-01

223

Vapor breakdown during ablation by nanosecond laser pulses  

Microsoft Academic Search

Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. Although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no attempts made on vapor breakdown by nanosecond laser pulses. This work intends to fill the gap. A kinetic model is developed

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

1995-01-01

224

Next generation Er:YAG fractional ablative laser  

Microsoft Academic Search

Pantec Biosolutions AG presents a portable fractional ablative laser system based on a miniaturized diode pumped Er:YAG laser. The system can operate at repetition rates up to 500 Hz and has an incorporated beam deflection unit. It is smaller, lighter and cost efficient compared to systems based on lamp pumped Er:YAG lasers and incorporates a skin layer detection to guarantee

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

2011-01-01

225

Experimental evaluation of optimized ablation patterns for laser refractive surgery.  

PubMed

A new experimental model based on plastic (Filofocon A) artificial eyes was used to study the ablation profiles and the outcomes of three state-of-the-art refractive surgery excimer lasers provided with narrow-beam flying spot and optimized algorithms (Ladarvision 4000, Alcon; Technolas 217 Z100, Bausch and Lomb; Allegretto wave Eye-Q, Wavelight). The 3-D ablation patterns produced by myopic laser corrections (-9, -6 and -3 D) on flat and spherical surfaces of Filofocon A were measured using high resolution optical profilometry. We found significant differences across lasers in the shape and depth of the ablation patterns. A comparison of the ablation patterns on flat and on spherical surfaces provided a measurement of the laser efficiency losses from the center to the periphery at each point of the spherical plastic corneas. This effect also varied across lasers, depending on their fluence (120-400 mJ/cm(2)). Estimates of the post-operative corneal shapes were obtained from the measurement on Filofocon A and plastic-corneal tissue correction factors. The predicted post-operative corneal ablation shape, ablated volume, asphericity and spherical aberration varied across lasers, as well as the relative contribution of ablation pattern designs and efficiency losses to the increased asphericity. Although the results show that the algorithms have been optimized to reduce the induction of spherical aberration, they would still benefit from the application of correction factors for efficiency effects derived from a systematic approach using experimental plastic models. These models have proved useful (1) to assess the outcomes of different lasers or ablation algorithms, (2) for precise calibration and testing of the lasers, and (3) to calculate experimental correction factors for efficiency effects. PMID:19688008

Dorronsoro, Carlos; Remon, Laura; Merayo-Lloves, Jesús; Marcos, Susana

2009-08-17

226

Femtosecond laser ablation of silicon–modification thresholds and morphology  

Microsoft Academic Search

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

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

2002-01-01

227

Laser ablation for the synthesis of carbon nanotubes  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

228

Optodynamic aspect of a pulsed laser ablation process  

NASA Astrophysics Data System (ADS)

A study of a pulsed laser ablation process is presented from a novel, optodynamic aspect. By quantitative analysis of laser-induced bulk ultrasonic and blast waves in the air the ablation dynamics is characterized. In this way the influence of the laser pulse parameters and of the interacting material on the ablation process was assessed. By the analysis of the laser drilling process of thin layered samples the material influence was demonstrated. Besides the ultrasonic evaluation of the laser pulse power density the plasma shielding for 10 ns laser pulses was analyzed by the same method. All measurements were noncontact. Bulk waves in the solid and blast waves in the air were measured simultaneously, an interferometric and a probe beam deflection method were used, respectively.

Hrovatin, Rok; Možina, Janez

1995-02-01

229

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

230

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

SciTech Connect

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

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

2013-08-28

231

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

232

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

SciTech Connect

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

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

2007-11-13

233

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

234

Dynamics of the plumes produced by ultrafast laser ablation of metals  

NASA Astrophysics Data System (ADS)

We have analyzed ultrafast laser ablation of a metallic target (Nickel) in high vacuum addressing both expansion dynamics of the various plume components (ionic and nanoparticle) and basic properties of the ultrafast laser ablation process. While the ion temporal profile and ion angular distribution were analyzed by means of Langmuir ion probe technique, the angular distribution of the nanoparticulate component was characterized by measuring the thickness map of deposition on a transparent substrate. The amount of ablated material per pulse was found by applying scanning white light interferometry to craters produced on a stationary target. We have also compared the angular distribution of both the ionic and nanoparticle components with the Anisimov model. While the agreement for the ion angular distribution is very good at any laser fluence (from ablation threshold up to ~1 J/cm2), some discrepancies of nanoparticle plume angular distribution at fluencies above ~0.4 J/cm2 are interpreted in terms of the influence of the pressure exerted by the nascent atomic plasma plume on the initial hydrodynamic evolution of the nanoparticle component. Finally, analyses of the fluence threshold and maximum ablation depth were also carried out, and compared to predictions of theoretical models. Our results indicate that the absorbed energy is spread over a length comparable with the electron diffusion depth Lc (~30 nm) of Ni on the timescale of electron-phonon equilibration and that a logarithmic dependence is well-suited for the description of the variation in the ablation depth on laser fluence in the investigated range.

Donnelly, T.; Lunney, J. G.; Amoruso, S.; Bruzzese, R.; Wang, X.; Ni, X.

2010-08-01

235

Femtosecond laser ablation of Au film around single pulse threshold  

NASA Astrophysics Data System (ADS)

Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence 'phi'0. From the plot of the accumulated laser fluence N'phi'_(th)(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.

Ni, Xiaochang; Wang, Ching-Yue; Wu, Yinzhong; Yang, Li; Jia, Wei; Chai, Lu

2006-04-01

236

Cluster emission under femtosecond laser ablation of silicon  

NASA Astrophysics Data System (ADS)

Rich populations of clusters have been observed after femtosecond laser ablation of bulk silicon in vacuum. Size and velocity distributions of the clusters as well as their charge states have been analyzed by reflectron time-of-flight mass spectrometry. An efficient emission of both neutral silicon clusters Sin (up to n = 6) and their cations Sin+ (up to n = 10) has been observed. The clusters are formed even at very low laser fluences, below ablation threshold, and their relative yield increases with fluence. We show the dependencies of the cluster yield as well as the expansion dynamics on both laser wavelength and laser fluence. The mechanisms of the cluster formation are discussed.

Bulgakov, A.

2004-04-01

237

Mechanisms of Carbon Nanotube Production by Laser Ablation Process  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

238

GENERATION OF HIGHER FULLERENES FROM LASER ABLATION OF CARBYNE AND C60 PHOTOPOLYMER ASTROCHEMICAL IMPLICATIONS  

Microsoft Academic Search

Laser ablation of targets of carbonaceous matter containing carbyne nanodomains (the sp hybridised carbon chains) or targets of C60 photopolymer produced carbon clusters which have been detected by FT-ICR (Fourier-Transform Ion Cyclotron Resonance) mass spectrometer. When the carbonaceous matter containing carbyne has been employed as laser target, no C60 has been generated but only fullerene cages from C74 up to

Franco Cataldo; Yeghis Keheyan

2002-01-01

239

Optical emission spectroscopy and modeling of plasma produced by laser ablation of titanium oxides  

Microsoft Academic Search

In the present study, the time evolution of electron number density, of electron, atom and ion temperatures, of plasma produced by KrF excimer laser ablation of titanium dioxide and monoxide targets, are investigated by temporally and spatially resolved optical emission spectroscopy over a wide range of laser fluence from 1.7 to 6 J cm?2, oxygen pressures of 10?2–10?1 torr and

A. De Giacomo; V. A. Shakhatov; O. De Pascale

2001-01-01

240

Ripple formation at laser ablation of chromium thin film  

NASA Astrophysics Data System (ADS)

Ablation characteristics of chromium thin film on a glass substrate by nanosecond laser pulses were investigated. The laser beam was tightly focused through the glass substrate to a stripe-like spot using the acylindrical lens. The metal was removed only by the central part of the laser beam, where local laser fluence exceeded the well-defined ablation threshold. Formation of a wide area cleaned by the series of laser pulses caused some side effects. The stripe ablated by a single laser pulse had sharp edges on both sides, while the partially overlapping pulses formed a wide stripe with a complicated structure made of the remaining metal. Regular structures, ripples, were developed when laser fluence was slightly above the threshold and the shift between pulses was less than a half width of the line ablated by a single laser pulse. The ripples were located periodically (~4 ?) and were orientated perpendicularly to the long axis of the beam spot (in parallel to the laser pulse shift direction). Their direction did not depend on the laser beam polarization. Different models of the ripple formation in the thin metal film were considered, and instability of the moving vapor-liquid- solid contact line during evaporation of thin liquid films appear to be the most appropriate process responsible for the observed phenomena. Regular gratings with the unlimited line length can be produced by using the technique.

Regelskis, Kestutis; Raciukaitis, Gediminas; Gecys, Paulius

2007-02-01

241

MRI-guided laser ablation of neuroendocrine tumor hepatic metastases  

PubMed Central

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

Perala, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriala, Ilkka; Salmela, Pasi I; Tervonen, Osmo

2014-01-01

242

Comparison of tissue ablation with pulsed holmium and thulium lasers  

SciTech Connect

The ablation rates and tissue effects produced by a pulsed holmium laser (wavelength 2.12 {mu}m, pulse duration 250 {mu}s) and a pulsed thulium laser (wavelength 2.01 {mu}m, pulse duration 250 {mu}s) are compared. Because the absorption coefficient of water is almost three times greater at the shorter wavelength (65 versus 24 cm{sup {minus}1}), the thulium laser should have a significantly lower threshold of ablation and produce significantly less residual thermal injury. These hypotheses were tested in vitro. Ablation rates were measured using fresh liver and a mass loss technique and found to increase linearly with delivered radiant exposure. The threshold radiant exposure for ablation was derived from the mass loss measurements and found to be 36 J/cm{sup 2} for the holmium laser and 29 J/cm{sup 2} for the thulium laser. The corresponding heats of ablation were 10 kJ/cm{sup 3} for the holmium laser and 9.7 kJ/cm{sup 3} for the thulium laser. These values were not statistically different.

Nishioka, N.S.; Domankevitz, Y. (Massachusetts General Hospital, Boston, MA (US))

1990-12-01

243

Laser cutting of carbon fiber reinforced plastics (CFRP) by UV pulsed laser ablation  

NASA Astrophysics Data System (ADS)

In this paper, we report on a micro-cutting of carbon fiber reinforced plastics (CFRP) by nanosecond-pulsed laser ablation with a diode-pumped solid state UV laser (DPSS UV laser, ?= 355nm). A well-defined cutting of CFRP which were free of debris and thermal-damages around the grooves, were performed by the laser ablation with a multiple-scanpass irradiation method. CFRP is a high strength composite material with a lightweight, and is increasingly being used various applications. UV pulsed laser ablation is suitable for laser cutting process of CFRP materials, which drastically reduces a thermal damage at cut regions.

Niino, Hiroyuki; Kurosaki, Ryozo

2011-02-01

244

Micro-patterning for polymer electrolyte fuel cells: Single pulse laser ablation of aluminum films from glassy carbon  

NASA Astrophysics Data System (ADS)

Microfuel cells are a possible replacement for batteries as energy sources in portable devices. At PSI a micropolymer electrolyte fuel cell was developed, whose flow fields consist of micro-structured glassy carbon plates. Micro-structuring of glassy carbon is carried out in a multi-step process. A sputtered aluminum mask is selectively removed by single pulse laser ablation from glassy carbon thereby defining micro-channels subsequently etched by reactive ion etching. A pulsed XeCl excimer laser (308 nm) is used for the single pulse patterning of a metal mask on the glassy carbon. The influence of the excimer laser typical pulse to pulse energy fluctuations on the micro-structuring process must be known to minimize defects during RIE etching of the micro-channels. To obtain a better understanding of the processes occurring during ablation, ns-shadowgraphy was performed. The formation of a shockwave was observed, followed by a similar but much slower perturbation, and the subsequent release of fragments. The calculated velocities can be correlated with the energy release during ablation. The post-ablation examination of the samples by profilometry, optical microscopy, SEM and EDX is used to measure the amount of removed material, the quality of the aluminum mask edges and aluminum residues on the glassy carbon surface. Such criteria allow us to classify the laser irradiation as a function of laser fluence: no ablation, partial ablation, complete ablation, and over-ablation.

Seyfang, Bernhard C.; Fardel, Romain; Lippert, Thomas; Scherer, Guenther G.; Wokaun, Alexander

2009-03-01

245

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

246

Laser ablation of silicate glasses doped with transuranic actinides  

SciTech Connect

Direct sampling laser ablation plasma mass spectrometry (DS-LAMS) was applied to silica glasses doped with {sup 237}Np, {sup 242}Pu or {sup 241}Am using a unique instrument recently installed into a transuranic glovebox. The primary goal was to assess the utility of mass spectrometry of directly ablated ions for facile evaluation of actinide (An) constituents of silicate glass immobilization matrices used for encapsulation of radionuclides. The instrument and general procedures have been described elsewhere. Three high-purity silicate glasses prepared by a sol-gel process (SG) and one conventional high-temperature (HT; melting point {approx} 1,450 C) borosilicate glass were studied. These glasses comprised the following constituents, with compositions expressed in mass percentages: Np-HT {approx} 30% SiO{sub 2} + 6% B{sub 2}O{sub 3} + 3% BaO + 13% Al{sub 2}O{sub 3} + 10% PbO + 30% La{sub 2}O{sub 3} + 8% {sup 237}NpO{sub 2}; Np-SG {approx} 70% SiO{sub 2} + 30% {sup 237}NpO{sub 2}; Pu-SG {approx} 70% SiO{sub 2} + 30% {sup 242}PuO{sub 2}; Am-SG {approx} 85% SiO{sub 2} + 15% {sup 241}AmO{sub 2}.

Gibson, J.K.; Haire, R.G.

1998-10-01

247

Cleaning of large area by excimer laser ablation  

NASA Astrophysics Data System (ADS)

Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser, beam deliver, particle collection cell, real time control of cleaning processes. Results concerning surface laser interaction and substrate modifications are presented.

Sentis, Marc L.; Delaporte, Philippe C.; Marine, Vladimir I.; Uteza, Olivier

2000-01-01

248

Acoustic wave monitoring during laser ablation of tissue  

Microsoft Academic Search

The homogeneous and inhomogeneous model media, human aorta tissue were investigated under irradiation of Q-switched Nd-YAG laser and XeCl excimer laser. Temporal course of acoustic pressure with resolution of 3 - 5 ns, the efficiency of ablation, the distribution of ejected droplets over sizes were studied for laser fluencies 0.1 - 15 J\\/cm2. Pressure course depends on laser fluence and

Alexander A. Karabutov; Natalia B. Podymova; Vladilen S. Letokhov

1996-01-01

249

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

250

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

251

A new UHV system for the preparation of carbon stripper foils by laser plasma ablation deposition  

NASA Astrophysics Data System (ADS)

Laser plasma ablation of spectroscopically pure graphite under UHV conditions is a well established method for the preparation of thin carbon stripper foils. Such foils with their structure of randomly oriented nanocrystallites can best withstand ion irradiation damage. Accelerator users around the world are interested in this type of carbon stripper foils due to a guaranteed reproducibility, quality, thickness and uniformity given by the procedure. In addition a high reproducible yield with a low effort for floating, mounting and slackening is desired. Users of high-energy accelerators want to profit from this development, but need stripper foils of up to 500 ?g/cm 2 for the relevant charge state equilibrium whereas carbon foils of this type could only be prepared with an upper limit of 10 ?g/cm 2 in the existing set up. The new design was aimed to overcome all thickness limitations. The crucial component of the laser plasma ablation technique is the laser entrance window which becomes opaque during carbon ablation. A new plant which overcomes this problem is being assembled. Due to a higher source-to-window distance and a better laser light transmission, caused by slightly changed laser plasma conditions, the life of the laser entrance window before exchange could be prolonged by a factor of five. Presumably, there are no thickness limitations anymore due to a vacuum interlock that permits the exchange of the entrance window without breaking the vacuum in the ablation-deposition chamber.

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

2004-03-01

252

Wavelength scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency in laser fusion  

SciTech Connect

We examine the scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency with the wavelength of the laser, using a recent theoretical analysis of ablative laser driven implosions as a tool. Symmetrization by a hot atmosphere is most effective for long wavelength lasers, whereas ablation pressure and hydrodynamic efficiency are best for shorter laser wavelengths.

Max, C.E.; Lindl, J.D.; Mead, W.C.

1981-07-31

253

Plasma mediated ablation of biological tissues with ultrashort laser pulses  

SciTech Connect

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

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

1995-03-08

254

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

PubMed

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

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

2014-07-01

255

Parallel femtosecond laser ablation with individually controlled intensity.  

PubMed

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

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

2014-02-10

256

EXCIMER LASER ABLATION OF GLASS FIBER IN REINFORCED POLYMER  

Microsoft Academic Search

In excimer laser ablation of glass fiber reinforced polymer, the fibers were found to be acting as refocusing lenses and caused partial fiber removal within the fiber. An analytical analysis based on Snell's law of refraction was used to calculate the laser intensity within the fiber, and the results of which were able to explain the partial removal phenomenon.

T. M. Yue; S. M. Mei; K. C. Chan

2002-01-01

257

Vapor breakdown during ablation by nanosecond laser pulses.  

National Technical Information Service (NTIS)

Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. Although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no ...

C. L. Liu D. B. Geohegan J. M. Donato J. N. Leboeuf R. F. Wood

1995-01-01

258

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

259

Endovenous laser ablation with TM-fiber laser  

NASA Astrophysics Data System (ADS)

Endovenous Laser Ablation (EVLA) has become a popular minimally invasive alternative to stripping in the treatment of saphenous vein reflux. Several wavelengths have been proposed; of which 810, 940 and 980- nm are the most commonly used. However, the most appropriate wavelength is still the subject of debate. Thermal shrinkage of collagenous tissue during EVLA plays a significant role in the early and late results of the treatment. The aim of this study is to compare the efficacy of 980 and 1940-nm laser wavelengths in the treatment of varicose veins. In this study, 980 and 1940-nm lasers at different power settings (8/10W for 980-nm, 2/3W for 1940-nm) were used to irradiate stripped human veins. The most prominent contraction and narrowing in outer and inner diameter were observed with the 1940-nm at 2W, following 980-nm at 8W, 1940-nm at 3W and finally 980-nm at 10W. The minimum carbonization was observed with the 1940-nm at 2W. As a conclusion, 1940-nm Tm-fiber laser which has a significant effect in the management of varicose veins due to more selective energy absorption in water and consequently in the vein is a promising method in the management of varicose veins.

Somunyudan, Meral Filiz; Topaloglu, Nermin; Ergenoglu, Mehmet Umit; Gulsoy, Murat

2011-02-01

260

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

Microsoft Academic Search

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

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

1999-01-01

261

Pulsed infrared laser ablation rates and characteristics in otic capsule  

NASA Astrophysics Data System (ADS)

Holmium:YAG (2.1 micrometers ) and Erbium:YAG (2.9 micrometers ) lasers have been suggested for use in neurotologic operations. The relatively high absorption in biologic tissues and minimal thermal diffusion associated with pulsed lasers make them attractive alternatives to CO2 and visible wavelength lasers, which currently enjoy widespread clinical use. There has been no systematic investigation of the properties of these lasers in a tissue model relevant to temporal bone operations, though there are numerous clinically oriented studies using these wavelengths. The microarchitecture of otic capsule (bone tissue of the inner ear) differs dramatically from bone found elsewhere in the body. Porcine otic capsule was machined into 0.8 mm thick specimens. The ablation rates of Ho:YAG and Erbium:YAG lasers were determined with incident flux varying from 6 - 20 J/cm2/pulse at 4 Hz PPR. Otic capsule specimens were ablated under both wet (physiologic) and dry (chemical dehydration) conditions. With Ho:YAG irradiation, dry otic capsule ablated with multiple episodes of stalling out. The relative number of specimens where stalling out occurred decreased with increasing laser flux. Wet tissue demonstrated similar characteristics, but with a lower ablation rate for a given fluence. In Erbium:YAG treated tissue, similar observations were noted, but the dependence on fluence is less clear in both wet and dry tissues. Water is shown to play a key role in the ablation process. The threshold of ablation is lower in wet tissue than in dehydrated tissue. The homogeneous microarchitecture of otic tissue also strongly influences the ablation process. Possible mechanisms are discussed.

Wong, Brian J.; Neev, Joseph; Sung, Vivian; Simonian, Belinda; Cheung, Eric M.; Berns, Michael W.

1995-05-01

262

Ablation studies of erbium:YAG laser radiation with ?  

NASA Astrophysics Data System (ADS)

The ablative mechanisms associated with 0022-3727/29/11/001/img2 radiation produced by a free-running Er:YAG laser have been studied using pellethane as a target medium. Probe beam techniques have been used and provide evidence that each individual relaxation oscillation within the free-running pulse can lead to ablation. A simple model, which takes into account the presence of the ablation plume, has been applied to the data and fits well. A threshold fluence for ablation of 0022-3727/29/11/001/img3 was obtained with an absorption coefficient of 0022-3727/29/11/001/img4. The studies may have relevance to medical applications of the laser.

Wannop, N. M.; Dickinson, M. R.; Farrar, S. R.; King, T. A.

1996-11-01

263

Characterization of products of excimer laser ablation of collagen  

NASA Astrophysics Data System (ADS)

The presence of hydroxyl radicals in the ArF excimer ablation sites in bovine corneal tissue has been investigated by laser-induced fluorescence and Raman spectroscopy. Raman spectroscopy has also been applied to examine the time-resolved temperature of the water component of the ablation site as well as the spatially selective measurement of surface desiccation. Results indicate that the hydroxyl radical is not generate in abundance during the ablation process. Also, Raman monitoring of the ablation site demonstrates no detectable heating during ArF irradiation, while elevated temperatures are observed following exposure of the corneal surface to a Er:YAG laser. Finally, comparison of C-H and O-H Raman bands shows potential utility as a spatially selective means for monitoring tissue hydration.

Ediger, Marwood N.; Hahn, D. W.; Pettit, George H.

1995-05-01

264

Optical properties measurement of the laser-ablated tissues for the combined laser ablation with photodynamic therapy  

NASA Astrophysics Data System (ADS)

Laser ablation therapy combined with photodynamic therapy (PDT) is studied for treatment of advanced cancers. The clinical outcome of PDT may be improved by the accurate knowledge about the light distribution within tissue. Optical properties [absorption coefficient (?a), scattering coefficient (?s), anisotropy factor (g), refractive index, etc.] of tissues help us realizing a light propagation through the tissue. It is important to understand of the effect of laser coagulation formed by laser ablation to PDT. The aim of this study is to estimate of influence of coagulated region to PDT for effective PDT combined laser ablation therapy. We evaluated the optical property of mouse tumor tissue in native and coagulated state using a double integrating sphere system and an inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. After laser ablation, the ?a and reduced scattering coefficient spectra of coagulated tissues were increased in the wavelength range from 350 to 1000 nm. The optical penetration depth of coagulated tissues is 1.2-2.9 times lower than the native state in the wavelength range from 350 to 1000 nm. The intensity of the light energy inside the coagulated tissue falls to about 60% of its original value at the end of coagulated layer. The evaluation of light energy distribution by the determination of the tissues optical properties could be useful for optimization of the treatment procedure in combined laser ablation with PDT.

Honda, Norihiro; Ishii, Katsunori; Awazu, Kunio

2012-02-01

265

Mechanism of laser ablation in an absorbing fluid field  

SciTech Connect

Selection of a laser source for intravascular applications has frequently been predicated upon assumptions involving transmissibility in blood of the wavelength of light emitted by a given laser. Standard absorption curves for ultraviolet radiation in blood and infrared radiation in water would suggest that transmission of ultraviolet radiation through a blood field and infrared radiation through any aqueous fluid field would be insufficient for tissue ablation. The present series of experiments was undertaken to determine whether these theoretical predictions would in fact obviate the use of these wavelengths in a blood field. Specimens of normal human myocardium and/or polyvinylchloride were submerged under blood and water and irradiated with ultraviolet radiation (351 nm) delivered as a focused beam and via an optical fiber and infrared radiation (10,600 nm) delivered as a focused beam. Ablation of myocardium was successfully accomplished with a focused beam of both ultraviolet and infrared radiation under as much as 5 mm of blood and with ultraviolet radiation via an optical fiber with the fiber tip up to 3 mm distant from the tissue specimen. High-speed cine recordings of ablation carried out using a focused beam of laser radiation demonstrated that formation of a dynamic optical cavity is the basis for successful pulsed ultraviolet and infrared laser transanguineous tissue ablation. These results thus demonstrate that prediction of wavelength transmission through fluid media based on optical properties of a static fluid does not predict ability to accomplish ablation under dynamic circumstances of laser irradiation.

Isner, J.M.; DeJesus, S.R.; Clarke, R.H.; Gal, D.; Rongione, A.J.; Donaldson, R.F.

1988-01-01

266

Corneal sensitivity and nerve regeneration after excimer laser ablation.  

PubMed

We studied the recovery of corneal sensitivity and corneal regeneration after excimer laser and manual epithelial debridement. The corneal epithelia of right eyes of New Zealand white rabbits (n = 21) were manually debrided and the corneal epithelia of the left eyes were ablated with the excimer laser (47 mm depth, 5 Hz, and 160 mJ/cm2). The relative density of innervation on the intraepithelial layer was measured using gold chloride staining and light microscopy. Wound healing and corneal sensitivity also were observed. Laser-ablated corneal sensitivity increased rapidly to a normal level by day 5, then increased gradually and reached a maximum at day 42. It remained elevated until 126 days, then returned to normal at 210 days. There were significant differences in the recovery of sensitivity after excimer ablation and manual epithelial removal. At day 35, relative density of innervation in the intraepithelial layer treated with excimer laser ablation was significantly higher than that treated with manual debridement. We observed a correlation between increased sensitivity and increased nerve density after excimer ablation. Compared with manual debridement, laser treatment resulted in an increase in networks of axons with terminal endings. This may not be the only factor correlating directly with hypersensitivity after corneal debridement, but it may indicate a quicker recovery route by using a presurgical manual debridement technique. PMID:8033572

Ishikawa, T; del Cerro, M; Liang, F Q; Loya, N; Aquavella, J V

1994-05-01

267

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

268

Tridimensional ablation region in femtosecond laser micromachining with diffractive lenses  

NASA Astrophysics Data System (ADS)

Increment of the axial region of ablation in a micromachining process is demonstrated when a refractive lens (RL) is replaced by a diffractive lens (DL). The depth of focus of a DL and a RL with the same numerical aperture are compared. For ultrashort pulses, the broadband spectrum of the laser together with the chromatic aberrations associated to the DL made its ablation region greater than the one corresponding to a RL. We measure experimentally the tridimensional ablation region for both types of lenses with 100 fs and 30 fs pulses. This study is expected to be promising to alleviate the mechanical tolerances in femtosecond micromachining with diffractive optical elements (DOEs).

Torres-Peiró, S.; González Ausejo, J.; Mendoza-Yero, O.; Mínguez-Vega, G.; Lancis, J.

2013-11-01

269

Transient electron excitation in laser-induced plasma-assisted ablation of transparent materials  

SciTech Connect

We investigate the mechanism of laser-induced plasma-assisted ablation (LIPAA), by which high-quality and high-efficiency ablation of transparent materials, such as glass, can be performed with a single conventional pulsed laser. The laser-induced plasma induces transient absorption of the laser beam (532 nm) by the glass substrate. The origin of the transient absorption is electron excitation by ions with kinetic energy more than approximately 10 eV in the plasma, which is observed by measuring transient polarization change in the glass substrate applied with a high external pulsed electric field during the plasma-assisted electron excitation (plasma-conductivity measurement). A possible mechanism of LIPAA is proposed based on the results obtained.

Hanada, Yasutaka; Sugioka, Koji; Obata, Kotaro; Garnov, Serge V.; Miyamoto, Iwao; Midorikawa, Katsumi [Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan) and Department of Applied Electronics, Faculty of Industrial Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); A.M. Prokhorov General Physics Institute of Russian Academy of Sciences, Vavilov Street 38, 119991 Moscow (Russian Federation); Department of Applied Electronics, Faculty of Industrial Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)

2006-02-15

270

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

SciTech Connect

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

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

1993-10-01

271

Matrix-Independent Calibration of Laser Ablation Microanalysis by High Resolution ICP- MS  

NASA Astrophysics Data System (ADS)

The combination of laser ablation and inductively coupled plasma mass spectrometry (LA-ICPMS) allows for rapid chemical analysis of solid samples at high spatial resolution. Calibration of the technique is limited by the small number of reliable standards available and by the diversity of solid matrices, including silicates, oxides, sulfides, carbonates, metals, etc. The situation is best for silicate glasses, for which both USGS standards and MPI-DING glass standards are available spanning a wide range of silica content. In laser ablation, the laser produces an aerosol that is ionized by the argon plasma source, so that ionization efficiency depends primarily on the plasma and not on the ablation process. Thus, internally standardized measurements by laser ablation should, in principle, be insensitive to matrix composition. Concerns about the necessity for sample-standard matrix matching have previously limited the possible quantitative applications of the method, but the necessity of matrix matching has not been previously studied in detail. We will present the results of a detailed study of matrix- dependence on inter-calibration of a broad range of elements in silicate, sulfide, metal and aqueous matrices, using a UP213 (213 nm) laser ablation system coupled to high resolution ICP-MS (Element1 and Element XR). We define a relative sensitivity factor (RSF) for each element which, when multiplied by the ion intensity ratio, yields a concentration ratio to an internal standard element. This study documents that the RSFs for practically all elements with a First Ionization Potential (FIP) below 8 ev are matrix-independent. The calibration of laser ablation analysis of such elements can be performed using aqueous or desolvated aqueous standards. Finally, using the faraday cup detector of an Element XR, we examine the influence of the measured oxygen and argon ion intensities on the RSFs of other elements. We find that as the oxygen ion to argon ion ratio increases, the RSF of high FIP elements increases (i.e., measured intensity decreases). Thus, for such elements the decrease of measured ion intensity is coincident with increased oxygen ion production in the plasma (most notably for aqueous matrices), and this constitutes a true matrix effect for ICP-MS analysis.

Gaboardi, M.; Humayun, M.

2008-05-01

272

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

273

Ablative Laser Propulsion Using Multi-Layered Material Systems  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

274

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

275

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy : ablation properties and analytical behaviour.  

SciTech Connect

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1-15 GW cm{sup 2} Zr deficient, 40-250 GW cm{sup 2} Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP. Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.

Goodall, P. S.; Wood, E. L.; Johnson, S. G.; Fuels and Engineering (Argonne-West)

1995-12-01

276

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy: ablation properties and analytical behavior  

NASA Astrophysics Data System (ADS)

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1-15 GW cm -2 Zr deficient, 40-250 GW cm -2 Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP. Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.

Goodall, Phillip; Johnson, Stephen G.; Wood, Elon

1995-12-01

277

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

278

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

SciTech Connect

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

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

2006-12-01

279

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

280

Photomechanical basis of laser ablation of biological tissue  

NASA Astrophysics Data System (ADS)

The photomechanical picture of laser ablation of biological tissue asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. We have developed a three-dimensional theoretical 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. In addition, we have developed a complimentary interferometric technique which can measure the laser- induced thermoelastic expansion of a material with nanometer spatial resolution on a nanosecond time scale. The complex features of this expansion allow the needed optical, thermal, and mechanical properties of the target to be determined, which then allows the stress distribution to be calculated. This work has led to several significant results which support the photomechanical model of ablation of biological tissue. First, unlike the one-dimensional model predicts the development of significant tensile stressed on the surface of the target, precisely where ablation is observed to occur. Experimental results from bone are consistent with mechanical fracture caused by laser-induced stresses. Experimental results from human meniscus, a representative soft tissue, show additional behavior consistent with the growth and collapse of cavitation bubbles within the tissue caused by laser-induced stresses.

Perelman, Lev T.; Albagli, Douglas; Dark, Marta; von Rosenberg, Charles; Itzkan, Irving; Feld, Michael S.; Schaffer, Jonathan

1995-05-01

281

Laser ablated zirconium plasma: A source of neutral zirconium  

NASA Astrophysics Data System (ADS)

The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped using planner laser induced fluorescence imaging and total ablated mass of neutral zirconium atoms is estimated. Temporal and spatial evolutions of electron density and temperature are discussed by measuring Stark broadened profile and ratio of intensity of emission lines, respectively.

Yadav, Dheerendra; Thareja, Raj K.

2010-10-01

282

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

283

Below-Band-Gap Laser Ablation Of Diamond For TEM  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

284

Pulsed Laser Ablation Synthesis of Diamond Molecules in Supercritical Fluids  

NASA Astrophysics Data System (ADS)

Nanocarbon materials have been synthesized by pulsed laser ablation (532 nm; 52 J/cm2; 7 ns; 10 Hz) of highly oriented pyrolytic graphite in adamantane-dissolved supercritical xenon at a temperature T = 290.2 K and pressure p = 5.86 MPa. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3 hybridized bonds also found in diamond structures. The synthesis of diamantane was confirmed by gas chromatography-mass spectrometry. The same measurements also indicate the possible synthesis of other diamondoids up to octamantane. Thus, laser ablation in supercritical fluids is proposed as one practical method of synthesizing diamondoids.

Nakahara, Sho; Stauss, Sven; Miyazoe, Hiroyuki; Shizuno, Tomoki; Suzuki, Minoru; Kataoka, Hiroshi; Sasaki, Takehiko; Terashima, Kazuo

2010-09-01

285

Modelling the formation of nanostructures on metal surface induced by femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We employ the particle-in-cell method to simulate the mechanisms of femtosecond (fs) laser interactions with a metallic target. The theoretical approach considers the solid as a gas of free electrons in a lattice of immobile ions and the laser fluences close to the ablation threshold. At first moments of the interaction, our simulations mapped out different nanostructures. We carefully characterized the rippling phase and found that its morphology is dependent on the distribution of the electron density and the period of the ripples depends on the laser intensity. The simulation method provides new insights into the mechanisms that are responsible for surface grating formation.

Djouder, M.; Itina, T. E.; Deghiche, D.; Lamrous, O.

2012-01-01

286

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

PubMed

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

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

2011-09-01

287

Thermal melting and ablation of silicon by femtosecond laser radiation  

SciTech Connect

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

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

2013-03-15

288

Formation and characterization of nanoparticles via laser ablation in solution  

NASA Astrophysics Data System (ADS)

The work presented in this thesis encompassed laser ablation of various transition metals within a liquid environment. Through an improved understanding of the ablation process, control over the properties of the resultant nanoparticles can be obtained, and thusly nanoparticles can be tailored with specific properties. Creation of nanoparticles via laser ablation in solution is a relatively youngtechnique for nanoparticle synthesis, and the work presented should prove useful in guiding further exploration in ablation processes in liquids for nanomaterial production. When a laser is focused onto a target under a liquid environment, the target material and its surrounding liquid are vaporized. The concoction of vapor is ejected normal to the surface as a bubble. The bubble has a temperature reaching the boiling point of the metal, and has a gradient to the boiling point of the solvent. The bubble expands until it reaches a critical volume, and then subsequently collapses. It is within this bubble that nanoparticle formation occurs. As the bubble expands, the vapor cools and nanoparticle growth transpires. During the bubble collapse, pressures reaching GigaPascals have been reported, and a secondary nanoparticle formation occurs as a result of these high pressures. Chapter 1 delves a little more into the nanoparticle formation mechanisms, as well as an introduction to the analytical techniques used for characterization. Ablation of titanium took place in isopropanol, ethanol, water, and n-hexane, under various fluences, with a 532 nm Nd:YAG operating at 10 Hz. It was found that a myriad of nanoparticles could be made with vastly different compositions that were both solvent and fluence dependent. Nanoparticles were made that incorporated carbon and oxygen from the solvent, showing how solvent choice is an important factor in nanoparticle creation. Chapter 3 discusses the results of the titanium work in great detail and demonstrates carbide production with ablation in isopropyl alcohol. Ablation in n-hexane also showed diffraction patterns correlating with carbides, and water showed oxygen incorporation. These results showed the ability to utilize the solvent in tailoring nanoparticles to achieve desired properties. Zirconium and nickel were ablated with the Nd:YAG at 532 nm. These studies utilized a stainless steel chamber designed and built to improve control over the experimental variables. The nickel study showcased the new chamber's ability for reproducibility in a size dependence study based upon laser fluence. The results of ablation with the Nd:YAG were compared to femtosecond ablation experiments performed with a titanium:sapphire femtosecond laser system. The Ti:sapphire femtosecond laser operated at 10 Hz, produced femtosecond pulses centered at ˜795 nm. The pulse duration was varied from 100 fs to 390 fs, the nanoparticles created from each condition were characterized, and the results are presented in chapters 5 and 6. Aluminum nanoparticles were made using both nanosecond and femtosecond laser ablation techniques. Aluminum nanoparticles have a great deal of potential for use as fuel additives as well as in paints and coatings. The nanosecond ablation process rendered large nanoparticles (over 200 nm) and the results are briefly shown in Appendix A. The femtosecond system produced a much smaller distribution of nanoparticles, with nanoparticles remaining in suspension for over a month's time, as evidenced by their unique UV-Vis absorbance. These nanoparticles were produced in isopropyl alcohol, and were stabilized by the solvent, as TEM analysis showed nanoparticles with very little oxygen incorporation. The solvent is bound to the nanoparticles as a result of the formation process and as a result forms a protective coating, which prevents further oxidation over time. The remarkable stability of these aluminum nanoparticles is a testament of employing the high energy scheme of the laser ablation process in a manner to tailor the production of novel nanomaterials. (Abstract shortened by UMI.)

Golightly, Justin Samuel

289

Infrared laser ablation of dental enamel: influence of an applied water layer on ablation rate and peripheral damage  

NASA Astrophysics Data System (ADS)

Studies have shown that a water spray may augment the laser ablation rate of dental hard tissues in addition to reducing heat accumulation. However, the mechanism of augmentation is controversial and poorly understood. The influence of an optically thick applied water layer on the ablation rate was investigated at wavelengths in which water is a primary absorber and the magnitude of absorption varies markedly. Water was manually applied with a pipette and troughs were cut in enamel blocks using a laser scanning system. Q- switched and free running Er:YSGG and Er:YAG, free running Ho:YAG and 9.6 micrometers TEA CO2 laser systems were investigated. The addition of water increased the rate of ablation and produced a more desirable surface morphology during enamel ablation with all the erbium systems. Ablation was markedly more efficient for the Q-switched erbium lasers than for the longer free-running laser systems when a water layer was added. Although, the addition of a thick water layer reduced the rate of ablation during CO2 laser ablation, the addition of the water removed undesirable deposits of non-apatite mineral phases from the crater surface. There was extensive peripheral damage after irradiation with the Ho:YAG laser with and without added water without effective ablation of enamel. The results of this study suggest that water augments the ablation of dental enamel by aiding in the removal of loosely attached deposits of non-apatite mineral phase from the crater surface, thus producing a more desirable crater surface morphology. The non-apatite mineral phase interfere with subsequent laser pulses during erbium laser irradiation reducing the rate of ablation and their removal aids in maintaining efficient ablation during multiple pulses irradiation.

Ashouri, Nahal; Shori, Ramesh K.; Cheung, Jason M.; Fried, Daniel

2001-04-01

290

Double pulse laser ablation and plasma: Laser induced breakdown spectroscopy signal enhancement  

Microsoft Academic Search

A review of recent results of the studies of double laser pulse plasma and ablation for laser induced breakdown spectroscopy applications is presented. The double pulse laser induced breakdown spectroscopy configuration was suggested with the aim of overcoming the sensitivity shortcomings of the conventional single pulse laser induced breakdown spectroscopy technique. Several configurations have been suggested for the realization of

V. I. Babushok; F DELUCIAJR; J. L. Gottfried; C. A. Munson; A. W. Miziolek

2006-01-01

291

Laser-induced modification of metal nanoparticles formed by laser ablation technique in liquids  

Microsoft Academic Search

The effects of laser irradiation of silver colloids prepared by laser ablation technique in acetone have been studied. The laser irradiation was performed using laser radiation at different wavelengths (532, 266, 400 and 800nm). Additional irradiation of colloids resulted in the changes of particles morphology, which were monitored by absorption spectroscopy and transmission electron microscopy methods. The experimental conditions favoring

N. V. Tarasenko; A. V. Butsen; E. A. Nevar

2005-01-01

292

Surface ablation of transparent polymers with femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

In this work, a study of the laser ablation on the surface of poly methyl-methacrylate (PMMA) is presented. Experiments were performed with a femtosecond laser delivering 450 fs pulses at a wavelength of 1027 nm. The laser beam energy was controlled through a polarizer based attenuator and measured by a calibrated photodiode energy meter. A focusing method called z-scan is used to place the sample on the beam waist. This method uses a second energy meter placed behind the sample, which was used to monitor the energy transmitted across the sample in situ. Thus, the absorption was evaluated by comparing the measurements of both energy meters. The z-scan method is evaluated by studying the laser ablation in three different positions between the sample and the laser beam waist. It is found that above a threshold energy that depends on the focusing conditions, the absorbance of the samples increases with the pulse energy. After irradiation, dimensional analysis of the craters produced at different pulse energies is performed in order to determine the best focusing conditions and the ablation threshold for ablation of PMMA samples.

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

2014-05-01

293

Small glass particle cloud generation induced by laser ablation  

NASA Astrophysics Data System (ADS)

Burst of small fragments of glass has been evidenced in the present study, when ground glass surface is laser ablated. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of metal or polymer ablation. In this case, no additional metal coating has been made to further enhance absorption of laser pulse. Pulse laser shadowgraph has been taken to study the details of the phenomena in air and in vacuum. At least in vacuum, particle burst is found almost normal to the surface. By using ns-duration Nd:YAG laser of 100 mJ/pulse, observed particle velocity ranges 0.5 km/s to 1.5 km/s in case of in air and the maximum velocity is extended up to 1.5-2 km/s in vacuum. SEM observation of the ground surface reveals that glass surface is covered with micro cracks with several microns deep, which might attribute to macro particle production. In this sense, not surface roughness but also surface structure will be important in the ablation phenomena of glass. It is plausible that absorption of laser beam at the glass surface causes spallation like phenomena as well as production of an amount of plasma, and the plasma production might be responsible for the acceleration of broken fragments of glass. We applied the phenomena to ignite PETN powder explosive, and succeeded in igniting PETN powder only by laser ablation of ground glass.

Nagayama, Kunihito; Kotsuka, Yuriko; Nakahara, Motonao; Kubota, Shiro

2005-03-01

294

Surface quality of excimer laser corneal ablation with different frequencies.  

PubMed

To test the effects of different frequencies of a 193-nm excimer laser on the surface smoothness of the ablated materials and the damage to the adjacent structure, four different frequencies (5, 10, 15, and 20 Hz) of a 193-nm excimer laser were used to perform ablations on 20 rabbit corneas and four polymethylmethacrylate blocks at a fluence of 160 mJ/cm2. Each frequency was tested five times on five corneas. The ablated materials were processed and examined with scanning electron microscopy (SEM) and light and transmission electron microscopy (TEM) and a Zygo interference microscope, which quantitatively evaluates the surface smoothness. The results from the Zygo microscope show that there is no statistically significant difference in surface smoothness between any two different frequencies. The SEM reveals similar regularity and uniformity on the ablated surfaces, with no relationship between the laser frequencies and the amount of surface deposits. The TEM demonstrates no correlation between the various frequencies and the thickness of the superficial pseudomembrane and the amount of collateral damage in the adjacent stroma. It appears that the higher frequencies are comparable to the lower one (5 Hz) as to ablation quality, with the benefit of curtailing surgical time and decreasing the chances of eye movement. PMID:8261781

Liang, F Q; Ishikawa, T; Kim, J; del Cerro, M; Park, S B; Aquavella, J V

1993-11-01

295

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors  

NASA Astrophysics Data System (ADS)

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 ZnnOm and InnPm 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 In4P 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.; Ozerov, Igor; Marine, Wladimir

2010-10-01

296

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

297

Time Resolved Diagnostic of Dual-Pulsed Laser Ablation on Graphite Targets  

SciTech Connect

Plasma emission produced by Dual Pulsed Laser Ablation (DPLA) on two perpendicular graphite targets, separated 3 mm, was analyzed. Ablation was carried out in vacuum (10-6 Torr) by an excimer (248 nm) and a Nd: YAG (1064 nm) lasers, delayed up to 20 {mu}s. Spatial and temporal measurements were performed by time resolved optical emission spectroscopy, fast photography and two color interferometry. Time of flight was studied in order to determine the kinetic energies from the carbon species (C I, C II and C III). Comparison between dual-laser and single excimer laser ablation reveals that, ion energy distribution can be controlled by changing pulse delay between lasers. Results show that the highest reduction in the second pulse species velocities occurs at temporal delay between lasers from 1 to 5 {mu}s. Under these experimental conditions, the temporal evolution of temperature, electron and neutral densities was determined. Two colors interferometry allows study the plasma only up to 1.5 mm from the surface target. Thus no changes on the density values in single and dual pulse experiments were observed. On the other hand, time resolved optical emission spectroscopy shows an increase in temperature and electron density in dual pulse configuration at a distance of 10 mm from the target.

Sangines de Castro, R.; Sanchez Ake, C.; Sobral, H.; Villagran-Muniz, M. [Laboratorio de Fotofisica. Centro de Ciencias Aplicadas y Desarrollo Tecnologico. Universidad Nacional Autonoma de Mexico. Apartado Postal 70-186, Mexico D.F. 04510 (Mexico)

2006-12-04

298

Trace contaminant determination in fish scale by laser-ablation technique  

NASA Astrophysics Data System (ADS)

Laser ablation on rings of fish scale has been used to analyze the historical accumulation of polychlorinated biphenyls (PCB) in striped bass in the Watts Bar Reservoir. Rings on a fish scale grow in a pattern that forms a record of the fish's chemical intake. In conjunction with the migration patterns of fish monitored by ecologists, relative PCB concentrations in the seasonal rings of fish scale can be used to study the PCB distribution in the reservoir. In this study, a tightly-focused laser beam from a XeCl excimer laser was used to ablate and ionize a small portion of a fish scale placed in a vacuum chamber. The ions were identified and quantified by a time-of-flight mass spectrometer. Studies of this type can provide valuable information for the Department of Energy (DOE) off-site clean-up efforts as well as identifying the impacts of other sources to local aquatic populations.

Lee, Ida; Coutant, C. C.; Arakawa, E. T.

1993-10-01

299

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

Microsoft Academic Search

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

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

2002-01-01

300

Computational modeling of physical processes during laser ablation  

SciTech Connect

A combined theoretical and experimental effort to model various physical processes during laser ablation of solids (silicon) using a variety of computational techniques is described. Currently the focus of the modeling is on the following areas: (a) rapid transformations through the liquid and vapor phases under possibly nonequilibrium thermodynamic conditions induced by laser-solid interactions, (b) breakdown of the vapor into a plasma in the early stages of ablation through both electronic and photoionization processes, (c) hydrodynamic behavior of the vapor/plasma during and after ablation, and (d) effects of initial conditions in the vapor, in particular, the nature of the initial velocity distribution, on the characteristics of subsequent vapor expansion. Results from the modeling are compared with experimental observations where possible.

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

1994-09-01

301

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

302

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

303

Micro-ablation with high power pulsed copper vapor lasers  

NASA Astrophysics Data System (ADS)

Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser

Knowles, Martyn

2000-07-01

304

Temperature monitoring by infrared radiation measurements during ArF excimer laser ablation with cornea  

NASA Astrophysics Data System (ADS)

We measured infrared thermal radiation from porcine cornea during various fluences ArF excimer laser ablations with 1 microsecond(s) rise time. To obtain absolute temperature by means of Stefan-Boltzman law of radiation, we carried out a collection efficiency and detective sensitivity by a pre-experiment using panel heater. We measured the time course of the thermal radiation intensity with various laser fluences. We studied the relation between the peak cornea temperature during the ablation and irradiation fluences. We found the ablation situations, i.e., sub-ablation threshold, normal thermal ablation, and over-heated ablation, may be judged by both of the measured temperature transient waveforms and peak temperature. The boundary fluences corresponding to normal thermal ablation were 90 and 160 mJ/cm2. Our fast remote temperature monitoring during cornea ablation might be useful to control ablation quality/quantity of the cornea ArF laser ablation, that is PRK.

Ishihara, Miya; Arai, Tsunenori; Sato, Shunichi; Nakano, Hironori; Obara, Minoru; Kikuchi, Makoto

1999-06-01

305

Laser induced modification and ablation of InAs nanowires  

SciTech Connect

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

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

2012-05-01

306

Diagnostics and Impulse Performance of Laser-Ablative Propulsion  

SciTech Connect

Pressure time variations and associated flows induced by pulsed laser ablation were experimentally studied using the Velocity Interferometer System for Any Reflector (VISAR) and framing Schlieren visualization. The combination of either aluminum or polyacetal target and TEA CO{sub 2} laser pulse were examined. The VISAR measurement resolved that the pressure modulated from the laser power variation in the impulse generation processes. Integrated impulse induced by repetative CO{sub 2} laser pulses was measured using a torsion-type impulse balance. The effect of the ambient pressure was significant. The measured impulse characteristics were closely associated with target surface morphology and fluid dynamics.

Sasoh, Akihiro; Mori, Koichi [Department of Aerospace Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Anju, Kohei; Suzuki, Koji; Shimono, Masaya; Sawada, Keisuke [Department of Aerospace Engineering, Tohoku University, 6-6-2 Aramaki-Aza-Aoba, Sendai 980-8579 (Japan)

2008-04-28

307

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

308

The physics of UV laser cornea ablation  

Microsoft Academic Search

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

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

1991-01-01

309

Laser-ablation-assisted microparticle acceleration for drug delivery  

Microsoft Academic Search

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

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

2005-01-01

310

Preparation of planar multilayered targets for laser ablation studies  

Microsoft Academic Search

A method is described for the reliable production of reproducible multilayered targets for laser ablation rate studies using time-resolved x-ray spectroscopy. The targets consist of alternating layers of plastic and evaporated metals whose thickness and uniformity were examined by weighing and by SEM micrography to be suitable for experiments. The plastic layers are deposited by a dipping technique using various

R. Popil; A. Haromy; R. Fedosejevs; A. A. Offenberger

1986-01-01

311

Strongly Polarized Plasma Emission Produced by Laser Ablation of Aluminum  

Microsoft Academic Search

We have found that continuum emission produced in the laser ablation of a material may be strongly polarized, whereas as discrete atomic or ionic emission lines appear as minima in the plasma polarization spectrum [1]. This effect is indicative of strong directionality of electrons recombining in the plasma. By placing a polarizer before the detector, it is possible to suppress

Robert Gordon; Yaoming Liu; John Penczak; Youbo Zhao

2009-01-01

312

Cluster generation under pulsed laser ablation of zinc oxide  

NASA Astrophysics Data System (ADS)

Neutral and cationic Zn n O m clusters of various stoichiometry have been produced by nanosecond laser ablation of ZnO in vacuum and investigated by time-of-flight mass spectrometry. Particular attention was paid to the effect of laser wavelength (in the range from near-IR to UV) on cluster composition. Under 193-nm laser ablation, the charged clusters are essentially substoichiometric with ZnnO_{n-1}+ and ZnnO_{n-3}+ being the most abundant series. Both sub- and stoichiometric cationic clusters are generated in abundance at 532- and 1064-nm ablation whose composition depends on the cluster size. The reactivity of small stoichiometric ZnnOn+ clusters ( n<11) toward hydrogen is found to be high, while oxygen-deficient species are less reactive. The neutral plume particles are mainly stoichiometric with Zn4O4 tetramer being a magic cluster. It is suggested that the Zn4O4 loss is the dominant fragmentation channel of large zinc oxide clusters upon electron impact. Plume expansion conditions under ZnO ablation with visible and IR laser pulses are shown to be favorable for stoichiometric cluster formation.

Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G.; Ozerov, Igor; Marine, Wladimir

2010-12-01

313

Pulsed laser ablation of pepsin on an inorganic substrate  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

314

Trace contaminant determination in fish scale by laser ablation technique.  

National Technical Information Service (NTIS)

Laser ablation on rings of fish scale has been used to analyze the historical accumulation of polychlorinated biphenyls (PCB) in striped bass in the Watts Bar Reservoir. Rings on a fish scale grow in a pattern that forms a record of the fish's chemical in...

I. Lee, C. C. Coutant, E. T. Arakawa

1993-01-01

315

Manipulation of Laser Ablation Plume by Magnetic Field Application  

Microsoft Academic Search

Time- and wavelength-resolved observation of a laser ablation plume from a strontium titanate target was performed under a dipole magnetic field applied from the substrate side. In contrast to the conventional method, the present method gave rise to increasing ionization of the growth species in the plume in the vicinity of the substrate. Using this method, NiO films could be

Minoru Tachiki; Takeshi Kobayashi

1999-01-01

316

Preheat Studies on Laser Ablatively-Accelerated Foils.  

National Technical Information Service (NTIS)

The achievement of laser fusion requires the inward acceleration of pellet shells to very high velocity without excessive preheat of the pellet fuel. In a study of ablatively accelerated thin planar Al foils, we have determined the complete time history o...

E. A. McLean S. H. Gold J. A. Stamper R. R. Whitlock H. R. Griem

1980-01-01

317

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

318

Elemental fractionation in laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

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

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

1996-01-01

319

Study of Laser Ablation Efficiency for an Acrylic-Based Photopolymerizing Composition  

NASA Astrophysics Data System (ADS)

Results are presented from study of the effi ciency (ablated mass per unit energy, mechanical recoil momentum per unit energy) of laser ablation for a light-curable polymer. A substantial difference is seen between the thresholds and indicated criteria for laser ablation effi ciency in the liquid and cured phases. The highest energy effi ciency for laser ablation (~22.6 %) is achieved when the initially liquid polymer is exposed to radiation with the wavelength optimal for photopolymerization (365 ± 15 nm).

Loktionov, E. Yu.

2014-05-01

320

Laser ablation of organic coatings as a basis for micropropulsion  

Microsoft Academic Search

The micro laser plasma thruster (?LPT) is a new micropropulsion device which is competitive with the pulsed plasma thruster (?PPT) for steering or propelling 10–100 kg ‘microsatellites’. It is driven by a cluster of fiber-coupled infrared diode lasers, focused onto a two-layer ablating tape. Electrical to optical conversion efficiency is 50%. The tape consists of a transparent supporting layer through

C. Phipps; J. Luke; T. Lippert

2004-01-01

321

Laser ablation of a B 4C–polysiloxane composite  

Microsoft Academic Search

Composite materials, specifically ceramic–polymer composites and metal–polymer composites have received increased interest in a number of engineering applications, from impact protection, microelectronics to tribology. The characteristics of Nd:YAG laser ablation of a B4C:polysiloxane mixture have been studied with the use of time-integrated spectroscopy, laser surface profiling and microscopic analysis. The removal process for a variety of pulse widths and pulse

M. J. J. Schmidt; D. K. Y. Low; L. Li

2002-01-01

322

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

323

Acoustic transient generation in pulsed holmium laser ablation under water  

Microsoft Academic Search

In this study the role of acoustical transients during pulsed holmium laser ablation is addressed. For this the collapse of cavitation bubbles generated by 2.12 micrometers Cr:Tm:Ho:YAG laser pulses delivered via a fiber in water is investigated. Multiple consecutive collapses of a single bubble generating acoustic transients are documented. Pulse durations are varied from 130 - 230 microsecond(s) and pulse

Thomas Asshauer; Klaus Rink; Guy P. Delacretaz; Rene-Paul Salathe; Bruno E. Gerber; Martin Frenz; Hans Pratisto; Michael Ith; Valerio Romano; Heinz P. Weber

1994-01-01

324

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

325

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

326

Investigation of mechanisms of ultrashort laser pulse ablation through experiments and simulations  

Microsoft Academic Search

Ultrashort laser pulse (USLP) ablation has been investigated over a decade long. The machining quality, however, as well as ablation efficiency and understanding of the ablation mechanism, still need improvement. ^ First, a combined molecular dynamics (MD) and Monte Carlo (MC) method is used to investigate the particle transport and energy transport phenomena in USLP ablation. It is found that

Wenqian Hu

2011-01-01

327

Ablative and transport fractionation of trace elements during laser sampling of glass and copper  

Microsoft Academic Search

The fractionation of trace elements due to ablation and transport processes was quantified during Q-switched infrared laser sampling of glass and copper reference materials. Filter-trapping of the ablated product at different points in the sample introduction system showed ablation and transport sometimes caused opposing fractionation effects, leading to a confounded measure of overall (ablative + transport) fractionation. An unexpected result

P. M. Outridge; W. Doherty; D. C. Gregoire

1997-01-01

328

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

329

Stereotactic laser ablation of epileptogenic periventricular nodular heterotopia.  

PubMed

Periventricular nodular heterotopia (PVNH) is a neuronal migrational disorder often associated with pharmacoresistant epilepsy (PRE). Resective surgery for PVNH is limited by its deep location, and the overlying eloquent cortex or white matter. Stereotactic MR guided laser interstitial thermal therapy (MRgLITT) has recently become available for controlled focal ablation, enabling us to target these lesions. We here demonstrate the novel application and techniques for the use of MRgLITT in the management of PVNH epilepsy. Comprehensive presurgical evaluation, including intracranial EEG monitoring in two patients revealed the PVNH to be crucially involved in their PRE. We used MRgLITT to maximally ablate the PVNH in both cases. In the first case, seizure medication adjustment coupled with PVNH ablation, and in the second, PVNH ablation in addition to temporal lobectomy rendered the patient seizure free. A transient visual deficit occurred following ablation in the second patient. MRgLITT is a promising minimally invasive technique for ablation of epileptogenic PVNH, a disease not generally viewed as surgically treatable epilepsy. We also show here the feasibility of applying this technique through multiple trajectories and to create lesions of complex shapes. The broad applicability and long term efficacy of MRgLITT need to be elaborated further. PMID:24518890

Esquenazi, Yoshua; Kalamangalam, Giridhar P; Slater, Jeremy D; Knowlton, Robert C; Friedman, Elliott; Morris, Saint-Aaron; Shetty, Anil; Gowda, Ashok; Tandon, Nitin

2014-03-01

330

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

331

Copper-ion lasers  

Microsoft Academic Search

Three hollow cathode arrangements are examined to determine the optimal infrared output capacity of CuII-ion lasers. It is found that by employing slotted hollow cathodes, the highest electrical and pressure configurations are achieved. The greatest amount of efficiency is derived by using rows of cylindrical electrodes. Observations were conducted on ultraviolet laser operation at 250 nm and 10 mW, and

H. J. Eichler; H. Koch; J. Paffenholz; J. Salk; C. Skrobol; G. Schaefer; W. Wittwer

1979-01-01

332

Insight into electronic mechanisms of nanosecond-laser ablation of silicon  

SciTech Connect

We present experimental and theoretical studies of nanosecond ArF excimer laser desorption and ablation of silicon with insight into material removal mechanisms. The experimental studies involve a comprehensive analysis of the laser-induced plume dynamics and measurements of the charge gained by the target during irradiation time. At low laser fluences, well below the melting threshold, high-energy ions with a narrow energy distribution are observed. When the fluence is increased, a thermal component of the plume is formed superimposing on the nonthermal ions, which are still abundant. The origin of these ions is discussed on the basis of two modeling approaches, thermal and electronic, and we analyze the dynamics of silicon target excitation, heating, melting, and ablation. An electronic model is developed that provides insight into the charge-carrier transport in the target. We demonstrate that, contrary to a commonly accepted opinion, a complete thermalization between the electron and lattice subsystems is not reached during the nanosecond-laser pulse action. Moreover, the charging effects can retard the melting process and have an effect on the overall target behavior and laser-induced plume dynamics.

Marine, Wladimir; Patrone, Lionel; Ozerov, Igor [Centre de Recherche en Matiere Condensee et Nanosciences, UPR 7251 CNRS Universite de la Mediterranee, Case 913, 163 Avenue de Luminy, 13288 Marseille Cedex 9 (France); Bulgakova, Nadezhda M. [Institute of Thermophysics SB RAS, 1 Lavrentyev Ave., 630090 Novosibirsk (Russian Federation)

2008-05-01

333

Laser ablation of phenylazide in an argon matrix: direct observation and chemical reactivity of ablated fragments  

NASA Astrophysics Data System (ADS)

Ablation of pentafluorophenylazide (FPA) in an Ar matrix at 8-10 K was carried out upon irradiation with ns-pulsed UV lasers in a vacuum. The plume of ablated products was monitored by a time-resolved imaging/spectroscopic technique using a gated and intensified CCD camera system. A large amount of pentafluorophenylnitrene (FPN) having a high kinetic energy ( 6 eV) was ejected as fragments from the matrix film during ablation. A quantitative formation of triplet FPN from the photolysis of the FPA was observed by spectroscopic measurements in the IR and UV-visible regions, and was confirmed by a theoretical IR spectrum calculated according to density functional theory. A FPN beam is useful for chemical surface modification of organic materials, such as aromatic polyester and alkylthiol. A surface analysis of these materials by X-ray photoelectron spectroscopy and Fourier transform infrared reflection absorption spectroscopy showed that the FPN was immobilized onto the surface through chemical bonds. This technique for the chemical surface modification of materials is made possible by a pulsed beam of reactive fragments with a high density in the laser ablation process.

Niino, H.; Sato, T.; Yabe, A.

334

Comparison of ablation stake measurements and Airborne Laser Scanning results  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

335

Production and acceleration of protons by Titanium Hydride solid disks via excimer laser ablation  

NASA Astrophysics Data System (ADS)

In this work we present the preliminary investigations about the production of proton beams by pulsed laser ablation of solid disks produced by compressed Titanium Hydride (TiH) powder. The laser we used was an excimer KrF, operating at low intensity and ns pulse duration. The ion emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. We performed initial studies on the produced plasma for different laser fluence values. In free expansion mode we obtained protons and titanium ions having kinetic energy of some hundred of eV; by applying a post-accelerating voltage we analyzed the beams up to 15 keV.

Delle Side, D.; Velardi, L.; Nassisi, V.

2013-05-01

336

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

PubMed

Beams of ions from the laser ablation method of solid materials into an electron cyclotron resonance ion source (ECRIS) plasma have been used for the first time in experiments at ATLAS. Initial accelerator mass spectroscopy experiments using laser ablation for actinides and samarium have been performed. Initial results of coupling the laser system to the ECR source have guided us in making a number of changes to the original design. The point of laser impact has been moved off axis from the center of the ECR injection side. Motor control of the laser positioning mirror has been replaced with a faster and more reliable piezo-electric system, and different raster scan patterns have been tested. The use of the laser system in conjunction with a multi-sample changer has been implemented. Two major problems that are being confronted at this time are beam stability and total beam intensity. The status of the development will be presented and ideas for further improvements will be discussed. PMID:24593480

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

2014-02-01

337

Laser ablation of silver and gold in liquid ammonia  

NASA Astrophysics Data System (ADS)

Laser ablation of a silver (Ag) and/or gold (Au) target was performed in liquid ammonia (l-NH3) at 233 K using nanosecond laser pulses of 1064, 532 and 355 nm wavelengths. An “in situ” monitoring of the ablation process by UV/vis/NIR spectroscopy has shown the evolution of the surface plasmon extinction band of silver or gold nanoparticles and thus confirmed their formation. While sols of Au nanoparticles in l-NH3 are quite stable in air, those of Ag nanoparticles undergo oxidation to Ag(I) complexes with NH3 ligands. On the other hand, formation of solvated electrons, namely of the (e-)NH3 solvates, has not been unequivocally confirmed under the conditions of our laser ablation/nanoparticle fragmentation experiment, since only very weak vis/NIR spectral features of these solvates were observed with a low reproducibility. Reference experiments have shown that the well-known chemical production of these solvates is hindered by the presence of Ag and Au plates. Ag and Au targets can thus possibly act as electron scavengers in our ablation experiments.

Šmejkal, Petr; Pfleger, Ji?í; Vl?ková, Blanka

2010-10-01

338

Ultraviolet laser ablation of polycarbonate and glass in air  

SciTech Connect

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

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

2009-02-01

339

Ripple formation in the chromium thin film during laser ablation  

NASA Astrophysics Data System (ADS)

The beam of a nanosecond pulse laser tightly focused to a line was applied for the back-side ablation of the chromium thin film on a glass substrate. The stripe ablated with a single laser pulse had sharp edges on both sides and ridges of the melted metal around it. The partially overlapping pulses formed a wide cleaned area with a complicated structure made of the metal remaining from the ridges. Regular structures, ripples, were developed when laser fluence was slightly above the single-pulse removal threshold and the shift between pulses was less than half width of the line ablated with a single laser pulse. The ripples were located periodically (˜4 ?m) and were orientated perpendicularly to the long axis of the beam spot. Their orientation did not depend on the laser beam polarization. Different models of the ripple formation in the thin metal film were considered, and instability of the moving vapor-liquid-solid contact line during evaporation of thin liquid films appears to be the most probable process responsible for the observed phenomena. Formation of regular gratings with the unlimited line length was experimentally implemented by using the above-mentioned technique.

Regelskis, K?stutis; Ra?iukaitis, Gediminas; Gedvilas, Mindaugas

2007-05-01

340

Ultrafast laser ablation of metal films on flexible substrates  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

341

Plasma study in laser ablation process for deposition  

NASA Astrophysics Data System (ADS)

In order to get a better inside in the reactive Pulsed Laser Deposition of nitride thin films, we performed time- and space-resolved plasma diagnostics during ablation of Ti, Al and C targets in low pressure nitrogen containing atmospheres using pulsed nanosecond UV lasers. In the case of carbon, thin films of CxNy were deposited on silicon substrates and characterized by Rutherford Backscattering Spectroscopy and Nuclear Reaction Analysis. With respect to irradiation of metal targets, during which a dense and highly ionized plasma was induced for laser intensities >= 100 MWcm-2, much higher values >= 1 GWcm-2 were necessary to induce significant plasma ionization on carbon. To increase the plasma reactivity in the case of carbon ablation, a radiofrequency discharge was added to excite and preionize the ambient gas. From correlation between the plasma characteristics and thin film analyses, conclusions could be made about the CxNy deposition process.

Vivien, C.; Hermann, Jorg; Boulmer-Leborgne, C.

1998-05-01

342

Effect of Laser Pulse Energy on the Gold Nanoparticles Produced by Laser Ablation Method  

NASA Astrophysics Data System (ADS)

Laser pulse energy is shown to influence characteristics of Au nanoparticles (NPs) produced by laser ablation. Au NPs were formed with spherical shape and different size depending on the laser pulse energy. UV-Vis-NIR spectroscopy revealed the changes of surface plasmon resonance features with respect to size and number of NPs.

Dorranian, D.; Ghamkhari, S. M.; Mirghasemzadeh, N.

2013-05-01

343

Dual-beam ablation of fused silica by multiwavelength excitation process using KrF excimer and F 2 lasers  

Microsoft Academic Search

A new technique of dual-beam laser ablation of fused silica by multiwavelength excitation process using a 248-nm KrF excimer laser (ablation beam) coupled with a 157-nm F2 laser (excitation beam) in dry nitrogen atmosphere is reported. The dual-beam laser ablation greatly reduced debris deposition and, thus, significantly improved the ablation quality compared with single-beam ablation of the KrF laser. High-quality

J. Zhang; K. Sugioka; T. Takahashi; K. Toyoda; K. Midorikawa

2000-01-01

344

Femtosecond laser ablation on dental hard tissues—Analysis of ablated profile near an interface using local effective intensity  

NASA Astrophysics Data System (ADS)

This study evaluated the process of ablation produced by a Ti:Sapphire femtosecond laser under different average powers taking place at the enamel/dentin interface. Based on the geometry of ablated microcavities the effective intensity for ablation was obtained. This study shows the validity for the local effective intensity analysis and allows a quantification of the variation in the ablation geometry taking place at the interface of two naturally different materials. It shows that the variation of the diameter of the ablated region as a function of the cavity depth comes essentially from a mechanism of effective intensity attenuation, as a result of a series of complex effects. Additionally, our data are sufficient to predict that a discontinuity on the ablation profile will occur on the interface between two biological media: enamel-dentin, showing a suddenly jump on the ablated cavity dimensions.

Dutra-Correa, M.; Nicolodelli, G.; Rodrigues, J. R.; Kurachi, C.; Bagnato, V. S.

2011-05-01

345

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

346

Elemental fractionation of glass using laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Three laser wavelengths (1064, 532, and 266 nm) were employed for laser ablation at varied laser pulse energies to study the effect of irradiance and wavelength upon analytical results for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Two important results were observed and are reported here: (1) the intensity of the MS signal came to a local minimum when

Deborah Figg; Michael S. Kahr

1997-01-01

347

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

348

Focusing of a tabletopsoft-x-ray laser beam and laser ablation  

Microsoft Academic Search

We focused the beam of a high-repetition-rate capillary-discharge tabletop laser operating at a wavelength of 46.9 nm, using a spherical SiSc multilayer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray-tracing computations to characterize the focused beam. The radiation intensity within the 2-mm-diameter central region of

B. R. Benware; A. Ozols; J. J. Rocca; I. A. Artioukov; V. V. Kondratenko; A. V. Vinogradov

1999-01-01

349

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

Microsoft Academic Search

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,

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

1994-01-01

350

Focusing of a tabletop soft-x-ray laser beam and laser ablation  

Microsoft Academic Search

We focused the beam of a high-repetition-rate capillary-discharge tabletop laser operating at a wavelength of 46.9 nm, using a spherical Si\\/Sc multilayer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray-tracing computations to characterize the focused beam. The radiation intensity within the 2-μm -diameter central region

B. R. Benware; A. Ozols; J. J. Rocca; I. A. Artioukov; V. V. Kondratenko; A. V. Vinogradov

1999-01-01

351

Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses.  

PubMed

This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps. PMID:23571876

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

2013-04-01

352

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

353

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

354

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

355

Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation.  

PubMed

Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures. PMID:24292197

Malskat, W S J; Stokbroekx, M A L; van der Geld, C W M; Nijsten, T E C; van den Bos, R R

2014-03-01

356

Damage mechanism and morphology characteristics of chromium film in femtosecond laser rear-side ablation  

Microsoft Academic Search

In this paper, damage mechanism and morphology characteristics of chromium film in femtosecond laser rear-side ablation are investigated. The film removing process includes two key sub-processes: the laser ablation dynamic process and subsequent breaking and ejecting dynamic process. Film morphology in rear-side ablation is determined by the interrelation between the laser energy and the film strength. When lower laser energy

Wenjun Wang; Gedong Jiang; Xuesong Mei; Kedian Wang; Jinyou Shao; Chengjuan Yang

2010-01-01

357

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

National Technical Information Service (NTIS)

Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ...

L. B. Da Silva B. C. Stuart P. M. Celliers M. D. Feit M. E. Glinsky

1996-01-01

358

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

SciTech Connect

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

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

2012-11-15

359

Excimer laser surface ablation: a review of recent literature.  

PubMed

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

O'Brart, David P S

2014-01-01

360

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

361

In-situ and ex-situ investigations of pulsed laser ablation of Y target  

Microsoft Academic Search

High purity yttrium was ablated by using frequency quadrupled ultra-violet pulses of a Nd:YAG laser (?=266nm, ?FWHM=7ns) with power density of about 1GW\\/cm2. Laser ablation process was studied using in-situ mass spectrometry of the ablated species in combination with ex-situ analyses of both target surface and deposited films. An increase on the Y ablation rate was found at the beginning,

A. Lorusso; F. Gontad; A. Perrone

2011-01-01

362

Study of polymer ablation products obtained by ultraviolet laser ablation — inductively coupled plasma atomic emission spectrometry  

NASA Astrophysics Data System (ADS)

A study of the nature of aerosols following polymer laser ablation was performed. A glass sample was used for comparison. Aerosol fractions were analyzed by using simple methods based on transport efficiency and filters. Three different tube lengths, i.e. 4, 29 and 54 m, were inserted between the ablation cell and the inductively coupled plasma atomic emission spectrometry (ICP-AES) injector. For the glass sample, 10 elements were studied. Only Na and K exhibited different results as the particle size, i.e. tube length, was varied. The polymers used were poly(vinyl chloride), PVC, and poly(ethylene), PE. Three elements (Ca, Ti and Sn) under different chemical forms were measured. Unlike Ti and Sn the ablated aerosol particle size (mass) seemed to depend on the Ca chemical form. Another PVC sample containing 11 elements was also studied. Na, Al and C exhibited a different behavior with particle size with respect to the remaining elements. Then, the carbon signal was studied after a 0.3 ?m pore size filter had been placed between the ablation cell and the ICP torch. The results indicated that carbon was mainly present under gaseous form and particles smaller than 0.3 ?m size. The analysis of the aerosol gaseous phase by thermal desorption GC-MS confirmed the presence of polymer volatile thermal degradation products. These results explained why carbon could not be applied as an efficient internal standard.

Todolí, J.-L.; Mermet, J.-M.

1998-10-01

363

Complete prostatic ablation using a two-stage laser  

NASA Astrophysics Data System (ADS)

Laser photoirradiation has been delivered endoscopically for the treatment of both benign prostatic hyperplasia and early localized prostatic carcinoma. In treating carcinoma, aggressive transurethral resection of the prostate has been followed with laser irradiation to the remnants of malignant capsular disease. No attempt has been made heretofore to completely destroy the glandular prostate using laser irradiation alone. We performed a two-stage endoscopic laser prostatectomy in 6 adult mongrel dogs in an attempt to completely destroy the glandular prostate. Although no complications developed, histologic evaluation of the prostate revealed viable glandular elements in the midst of necrosis and atrophy. We conclude that in order to accomplish total ablation of the glandular prostate using laser photoirradiation, more precise thermal telemetry is needed.

Sayer, Jeanie; Cromeens, Douglas M.; Price, Roger E.; Johnson, Douglas E.

1993-05-01

364

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

365

Laser ablated carbon plume flow dynamics under magnetic field  

NASA Astrophysics Data System (ADS)

The dynamics of a conducting laser ablated carbon plume flow in the ablation furnace typical for nanoparticle synthesis is investigated by numerical modeling. The effect of magnetic field on the flow is accounted through the Lorentz body force. The study begins with benchmark calculations of two simple test cases, the Kelvin-Helmholtz instability and Hartmann layer. The evolution of plume is then studied for longitudinal and transverse magnetic fields. It is observed that the transverse magnetic fields have more impact than longitudinal fields on plume evolution for this application. Ionization and heat capacity variation in the plume are accounted through the Saha equation and the Shomate equation, respectively. Multiple plume ejections typical for pulsed laser deposition of thin films are also discussed.

Pathak, Kedar A.; Chandy, Abhilash J.

2009-04-01

366

CdTe nanoparticles synthesized by laser ablation  

SciTech Connect

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

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

2009-07-20

367

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

368

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

SciTech Connect

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

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

1996-05-01

369

Excimer laser ablation based microlens fabrication in polymer materials  

Microsoft Academic Search

We demonstrate that excimer laser ablation can be applied successfully to fabricate microlenses and arrays of microlenses in an easy set-up allowing great flexibility in terms of size, shape and focal length of the lenses. Due to the non-contact and direct-write nature of the process, the technique allows easy insertion of micro-optics in a late phase of a heterogeneous optoelectronic

K. Naessens; P. Van Daele; R. Baets

2002-01-01

370

Selective non-ablative wrinkle reduction by laser  

Microsoft Academic Search

BACKGROUNDANDOBJECTIVES: Skin resurfacing and wrinkle removal is a large medical laser market. However, the rate of undesirable side effects is high andsometimes is not warrantedby the aesthetic improvement observed. The authors have evaluated the poten- tial bene®ts of an approach to selective non-ablative wrinkle reduction. MATERIALSANDMETHODS:Thistech- nique selectively targets the micro- vasculature which plays a key role in the stimulation

Peter Bjerring; Marc Clement; Lene Heickendorff; Henrik Egevist; Mike Kiernan

2000-01-01

371

Nanofibre fabrication by femtosecond laser ablation of silica glass  

NASA Astrophysics Data System (ADS)

: This article presents a fabrication technique for generating densely populated and randomly oriented silica nanofibres by direct ablation of silica glass using a femtosecond laser with 12.4 MHz repetition rate and a pulse width of 214 fs, under ambient conditions. Four types of nanofibres with diameters ranging from a few tens of nanometers to a few hundreds of nanometers were formed. Some fibers reach lengths of 10 mm. The possible mechanisms for fibre formation have been explored.

Venkatakrishnan, Krishnan; Vipparty, Dheeraj; Tan, Bo

2011-08-01

372

Nanofibre fabrication by femtosecond laser ablation of silica glass.  

PubMed

This article presents a fabrication technique for generating densely populated and randomly oriented silica nanofibres by direct ablation of silica glass using a femtosecond laser with 12.4 MHz repetition rate and a pulse width of 214 fs, under ambient conditions. Four types of nanofibres with diameters ranging from a few tens of nanometers to a few hundreds of nanometers were formed. Some fibers reach lengths of 10 mm. The possible mechanisms for fibre formation have been explored. PMID:21934939

Venkatakrishnan, Krishnan; Vipparty, Dheeraj; Tan, Bo

2011-08-15

373

Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Principles and Applications  

Microsoft Academic Search

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

N. S. Mokgalaka; J. Gardea-Torresdey

2006-01-01

374

Modeling of laser ablation and fragmentation of human calculi  

SciTech Connect

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

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

1989-01-01

375

High-throughput metal nanoparticle catalysis by pulsed laser ablation  

Microsoft Academic Search

A high-throughput pulsed laser ablation (HT-PLA) system was developed to rapidly prepare uniformly sized single- and multi-metallic nanoparticles with different diameters for catalytic applications. Catalytic materials containing Rh, bimetallic Rh\\/Pt and trimetallic Rh\\/Pt\\/Au nanoparticles were synthesized from targets prepared by blending, tableting and sintering powders of pure metals, and by directly collecting the nanoparticles created on support materials. Nanoparticles exhibited

Selim Senkan; Michael Kahn; Shici Duan; Anna Ly; Craig Leidholm

2006-01-01

376

Control over a phase state of the laser plume ablated by femtosecond laser: Spatial pulse shaping  

Microsoft Academic Search

The conditions for the formation of a fully atomized laser-ablated plume using subpicosecond laser pulses have been studied theoretically and implemented experimentally. It is shown that the low-intensity wings, which generally exist in the spatial distribution of laser intensity in the focal plane and can contain a substantial part of the incident laser energy, are responsible for low-threshold phase transformations

E. G. Gamaly; Australia A. V. Rode; O. Uteza; V. Kolev; B. Luther-Davies; T. Bauer; J. Koch; F. Korte; B. N. Chichkov

2004-01-01

377

Laser ablation of human atherosclerotic plaque without adjacent tissue injury  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

378

Nanosecond laser ablation and deposition of Ge films  

NASA Astrophysics Data System (ADS)

In this work, nanosecond-pulsed from ultra-violet to infrared lasers: KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) were employed for ablation and deposition of germanium films in background pressure of <10-6 Torr. Deposition was carried out at room temperature on Si, GaAs, sapphire and glass. The as-deposited films, characterized by using scanning electron microscopy (SEM) and atomic force microscopy (AFM), consist of nano to micron-sized droplets on nanostructured film. The dependence of film properties on laser wavelengths and fluence are discussed.

Yap, Seong Shan; Siew, Wee Ong; Ladam, Cécile; Dahl, Øystein; Reenaas, Turid W.; Tou, Teck Yong

2010-08-01

379

Ablation laser pour la microélectronique plastique  

NASA Astrophysics Data System (ADS)

La microélectronique plastique connaît un développement sans précédent dans le domaine de la recherche. Cette étude s'intéresse à l'utilisation des lasers impulsionnels pour la réalisation de composants organiques sur supports souples. Les deux aspects plus particulièrement étudiés sont d'une part la gravure de polymère pour réaliser un canal entre la source et le drain, et d'autre part le développement d'un procédéde dépôt appelé LIFT pour Laser Induced Forward Transfer. Ce dernier pourrait notamment permettre dedéposer des composés organiques non solubles.

Alloncle, A.-P.; Thomas, B.; Grojo, D.; Delaporte, Ph.; Sentis, M.; Sanaur, S.; Barret, M.; Collot, Ph.

2006-12-01

380

Size control of metal nanoparticles produced by femtosecond laser ablation in liquids  

Microsoft Academic Search

We discuss the production of metal nanoparticles by laser ablation in liquid environments. A femtosecond laser is used to ablate a solid target immersed in liquid environments, forming nanoparticles in the liquid. This results in a colloidal suspension of nanoparticles, whose growth and size distribution can be controlled by (1) physical mechanisms, such as the fluence of the laser radiation

Jean-Philippe Sylvestre; Andrei V. Kabashin; De-Quan Yang; Edward Sacher; Michel Meunier

2004-01-01

381

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

Microsoft Academic Search

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

Annemie Bogaerts; Zhaoyang Chen; Renaat Gijbels; Akos Vertes

2003-01-01

382

Dual-wavelength laser irradiation through hollow optical fiber for hard tissue ablation  

Microsoft Academic Search

Laser ablation experiments on hard tissues are performed by guiding combined beam of Ho:YAG and Er:YAG laser light with a hollow optical fiber. An alumina ball is used as a hard-tissue model and ablation phenomenon are observed by an ultra-high-speed camera. The result show that the two laser light give dissimilar ablation effects due to different absorption coefficients in water

Tomonori Watanabe; Katsumasa Iwai; Yuji Matsuura

2008-01-01

383

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

384

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

385

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

386

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

387

Excimer laser patterned dielectric masks for the fabrication of diffractive optical elements by laser ablation  

Microsoft Academic Search

Masks for laser processing are generated by laser ablation patterning of dielectric layer systems. The application of these masks for the rapid fabrication of diffractive optical elements (DOEs) is presented. The diffractive optical elements are designed as phase-only elements, assuming an illumination with a plane wave. A continuous phase function is calculated using an iterative Fourier transform algorithm (IFTA). This

D. Schäfer; J. Ihlemann; K. Mann; G. Marowsky

1999-01-01

388

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

Microsoft Academic Search

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

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

2001-01-01

389

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

390

Realtime study of plume ejection dynamics in silicon laser ablation under 5 ns pulses  

NASA Astrophysics Data System (ADS)

We present results of nanosecond laser ablation of silicon over a broad range of laser intensities, investigated by studying the time evolution of the ablation plume ejection, which, as measured by transmission of a probe beam, consists of a fast ejection phase followed by a delayed slow ejection phase. Experimental results indicate that different physical processes dominate at different ablation stages. The laser intensity threshold for the appearance of the slow ejection is ~30 GW/cm2. The plume kinetics parameters extracted from our experiments agree well with estimations based on blast wave and homogeneous nucleation theories, providing a physical explanation for the observed ablation rate dependence on the laser light intensity.

Ren, Jun; Yin, Xiaobo; Orlov, Sergei S.; Hesselink, Lambertus

2006-02-01

391

Investigation of ultrashort pulse laser ablation of solid targets by measuring the ablation-generated momentum using a torsion pendulum.  

PubMed

50 fs - 12 ps laser pulses are employed to ablate aluminum, copper, iron, and graphite targets. The ablation-generated momentum is measured with a torsion pendulum. Corresponding time-resolved shadowgraphic measurements show that the ablation process at the optimal laser fluence achieving the maximal momentum is primarily dominated by the photomechanical mechanism. When laser pulses with specific laser fluence are used and the pulse duration is tuned from 50 fs to 12 ps, the generated momentum firstly increases and then remains almost constant, which could be attributed to the change of the ablation mechanism involved from atomization to phase explosion. The investigation of the ablation-generated momentum also reveals a nonlinear momentum-energy conversion scaling law, namely, as the pulse energy increases, the momentum obtained by the target increases nonlinearly. This may be caused by the effective reduction of the dissipated energy into the surrounding of the ablation zone as the pulse energy increases, which indicates that for femtosecond laser the dissipated energy into the surrounding target is still significant. PMID:21643140

Zhang, Nan; Wang, Wentao; Zhu, Xiaonong; Liu, Jiansheng; Xu, Kuanhong; Huang, Peng; Zhao, Jiefeng; Li, Ruxin; Wang, Mingwei

2011-04-25

392

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

NASA Astrophysics Data System (ADS)

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

Phuoc, Tran X.; Chen, Ruey-Hung

2011-03-01

393

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

Microsoft Academic Search

An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots)

Kevin Kremeyer; John Lapeyre; Steven Hamann

2008-01-01

394

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

NASA Astrophysics Data System (ADS)

Influence of laser wavelength, laser irradiance and the buffer gas pressure were studied in high irradiance laser ablation and ionization source coupled with an orthogonal time-of-flight mass spectrometer. Collisional cooling effects of energetic plasma ions were proved to vary significantly with the elemental mass number. Effective dissociation of interferential polyatomic ions in the ion source, resulting from collision and from high laser irradiance, was verified. Investigation of relative sensitivity coefficients (RSC) of different elements performed on a steel standard GBW01396, which was ablated at 1064 nm, 532 nm, 355 nm, and 266 nm, has demonstrated that the thermal ablation mechanism could play a critical role with the first three wavelengths, while 266 nm induces non-thermal ablation principally. Experimental results also indicated that there is no evident discrepancy for most metal elements on RSCs and LODs among four wavelengths at high irradiance, except that high boiling point elements like Nb, Mo, and W have higher RSCs at higher irradiance regions of 1064 nm, 532 nm, and 355 nm due to thermal ablation. A geological standard and a garnet stone were also used in the experiment subsequently, and their RSCs and LODs for metal elements show nonsignificant dependence on wavelength at designated irradiances. All results reveal that relatively uniform sensitivity can be achieved at any wavelength for metal elements in the solids used in our experiments at an appropriate irradiance for the low pressure high irradiance laser ablation and ionization source.

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

2009-03-01

395

Preparation of nanofluids using laser ablation in liquid technique  

SciTech Connect

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

Tran, P.X.; Soong, Yee

2007-06-01

396

Femtosecond laser plasma plume characteristics in the nanojoule ablation regime  

SciTech Connect

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

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

2013-05-14

397

Femtosecond laser plasma plume characteristics in the nanojoule ablation regime  

NASA Astrophysics Data System (ADS)

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

Banerjee, S. P.; Chen, Zhijiang; Fedosejevs, R.

2013-05-01

398

Ablation and plasma emission produced by dual femtosecond laser pulses  

SciTech Connect

Pairs of 80 fs, 800 nm laser pulses were used to ablate Si, Cu, and CaF{sub 2} in air. The spectrally resolved plasma emission was measured as a function of laser fluence and pulse delay. After an initial dip, the fluorescence was found to increase monotonically with pulse delay, reaching a plateau after some tens of picoseconds, depending on the material and fluence. The enhancement ratio (defined as the ratio of the fluorescence produced by the pulse pair to that produced by a single pulse of the same total fluence) reaches a maximum value of 6 and 11 at a fluence of {approx}6 J/cm{sup 2} for Si and Cu, respectively, and declines to a value below 2 at higher fluences. In contrast, the enhancement for CaF{sub 2} increases slowly from zero near threshold to a broad maximum value of 2 near 50 J/cm{sup 2}. Using reflectivity and atomic force microscopy measurements as diagnostics, we interpret the Si and Cu behavior in terms of a two phase mechanism, in which the first pulse melts the surface of the crystal and the second pulse ablates the resulting liquid film. A qualitatively different mechanism initiated by multiphoton absorption is involved in CaF{sub 2} ablation.

Singha, Sima; Gordon, Robert J. [Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607-7061 (United States); Hu Zhan [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130021 (China)

2008-12-01

399

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

SciTech Connect

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/cm{sup 2}), 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/cm{sup 2}), 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/cm{sup 2}), we find large, faceted particles that are attributed to the drying of PtO{sub x} 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 [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

400

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

NASA Astrophysics Data System (ADS)

Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion. A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 ?m, 30 J pulse energy was used to ablate water contained in a quadrate quartz container. Net imparted impulse and coupling coefficients were derived from the force sensor data and relevant results were presented for various laser energy densities. ICCD imaging was used in conjunction with the dynamic force techniques to examine the dependencies on laser energy density. Results showed that the impulse coupling coefficient could reach a maximum value when laser energy density was about 105 J/m2, and it would increase before laser energy got to this point and would decrease after this point, and ICCD imaging supplied important phenomenon to explain this variation, which were water ablation before laser energy density got to 105 J/m2 and laser-induced air-breakdown with water as an induction when laser energy density was higher than 105 J/m2.

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

2011-04-01

401

Comparison of Ablation Performance in Laser Lightcraft and Standardized Mini-Thruster  

Microsoft Academic Search

Experiments on laser ablation of black and white Delrin® with a 10.6-micron laser beam from a CO2 electric discharge laser are reported. Mass ablation and thrust generation (impulse) were accurately measured as a function of input laser energy in single-shot experiments. The efficiency of conversion of laser energy to jet kinetic energy depended on the geometry of the energy absorption\\/conversion

Sean D. Knecht; C. William Larson; Franklin B. Mead

2006-01-01

402

Acoustic wave monitoring of cleaning and ablation during excimer laser interaction with copper surfaces  

Microsoft Academic Search

Acoustic wave generation during excimer laser interaction with copper substrates has been investigated. It is found that the amplitudes of acoustic waves depend on laser fluence, pulse number and surface condition of the substrate and can be used to determine the nature of laser-material interactions such as pulsed-laser-induced cleaning, surface roughening and ablation. When laser fluence is below the ablation

Y. F. Lu; Y. P. Lee; M. H. Hong; T. S. Low

1997-01-01

403

A meteor ablation-cluster ion atmospheric sodium theory  

NASA Technical Reports Server (NTRS)

Neutral and ionic forms of sodium form narrow, well-defined layers which peak in the 90-95 km altitude region at midlatitudes. A new theory for the sodium layer is presented, which is found to be in good agreement with existing atmospheric observations as well as available laboratory measurements of rate constants. The layer is believed to result naturally from a meteor ablation source over a chemical sink with vertical transport of Na(+) playing an important role in the layer shape and variation. While the neutral chemistry is believed to consist of chemical equilibrium between Na and NaO, the ion chemistry departs from earlier studies and considers a cluster ion scheme. It is possible that higher-order cluster ions of sodium play a role in the formation of aerosols, through attachment or ion-induced nucleation processes.

Richter, E. S.; Sechrist, C. F., Jr.

1979-01-01

404

Identification of pharmaceutical glasses by laser ablation ICP-MS.  

PubMed

The chemical composition of pharmaceutical glasses (ampoules, infusion bottles, plunger) has been determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). A Nd:YAG laser with 10 Hz repetition rate in the Q-switch mode at its fundamental wavelength (1064 nm) was used to identify common types of pharmaceutical glasses. The following isotopes were used for measurements: 7Li, 11B, 23Na, 24Mg, 27Al, 28Si, 29Si, 30Si, 39K, 42Ca, 47Ti, 57Fe, 90Zr, 121Sb, 137Ba. Each analysis included the measurement of 12 craters. Relative standard deviations between 1.8% and 8.0% of the quantitative results were obtained. 29Si was used as internal standard. Standard reference materials (soda-lime-, lead- and borosilicate glasses) were used for external calibration of laser sampling. Linear calibration functions for each isotope were found. All samples and standard materials were digested in a two-step-procedure by nitric/fluoric acid, then measured and externally calibrated by ICP-MS with multi-elemental standard solutions using 45Sc as internal standard. Digestion and laser ablation results agree within 8% (confidential interval 95%) with the certified values. Intensity ratios of most isotopes also agree sufficiently with the corresponding theoretical values (+/- 18%). The developed method allows to distinguish different types of pharmaceutical glasses. PMID:11817168

Schmidt, T; Surmann, J P; Stephanowitz, H; Hoffmann, E

2001-11-01

405

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

NASA Astrophysics Data System (ADS)

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

Tong, Huifeng; Yuan, Hong; Tang, Zhiping

2013-01-01

406

Surface topography (nano-sized hillocks) and particle emission of metals, dielectrics and semiconductors during ultra-short-laser ablation: Towards a coherent understanding of relevant processes  

NASA Astrophysics Data System (ADS)

By combining new studies of the surface topography and the emission characteristics of particles during interaction of ultra-short-laser radiation with surfaces, in particular during laser ablation, three different types of general processes (sub 100 fs electronic processes like Coulomb explosion (CE) or field ion emission by surface optical rectification (SOR), processes related to electronic plasma (FEP) formation (typically a few hundred fs time scale) and thermal ablation (TA)) could be identified to explain ultra-short-laser ablation of matter at laser intensities around the ablation threshold. In particular, the identification of the unique appearance of individual, localized nano-hillocks, typically a few nm in height and with a diameter below typically 50 nm, can be regarded as characteristic for a strong localized potential energy deposition to the electronic system resulting in CE or SOR. The observation and possibility of CE even on metals has implications beyond the field of laser ablation. A remarkable result observed concerns the similarities between laser ablation and sputtering with highly charged ions.

Bashir, S.; Rafique, M. S.; Husinsky, W.

2009-07-01

407

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

408

Testing of concrete by laser ablation  

DOEpatents

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

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

1997-01-01

409

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

410

MR Temperature Imaging of Nanoshell Mediated Laser Ablation  

PubMed Central

Minimally invasive thermal therapy using high-power diode lasers is an active area of clinical research. Gold nanoshells (AuNS) can be tuned to absorb light in the range used for laser ablation and may facilitate more conformal tumor heating and sparing of normal tissue via enhanced tumor specific heating. This concept was investigated in a xenograft model of prostate cancer (PC-3) using MR temperature imaging (MRTI) in a 1.5T scanner to characterize the spatiotemporal temperature distribution resulting from nanoparticle mediated heating . Tumors with and without intravenously injected AuNS were exposed to an external laser tuned to 808 nm for 180 sec at 4W/cm2 under real-time monitoring with proton resonance frequency shift based MRTI. Microscopy indicated that these nanoparticles (140–150 nm) accumulated passively in the tumor and remained close to the tumor microvasculature. MRTI measured a statistically significant (p<0.001) increase in maximum temperature in the tumor cortex (mean=21±7°C) in +AuNS tumors versus control tumors. Analysis of the temperature maps helped demonstrate that the overall distribution of temperature within +AuNS tumors was demonstrably higher versus control, and resulted in damage visible on histopathology. This research demonstrates that passive uptake of intravenously injected AuNS in PC-3 xenografts converts the tumor vasculature into a potent heating source for nanoparticle mediated ablation at power levels which do not generate significant damage in normal tissue. When used in conjunction with MRTI, this has implications for development and validation of more conformal delivery of therapy for interstitial laser ablations.

Stafford, R. Jason; Shetty, Anil; Elliott, Andrew M.; Schwartz, Jon A.; Goodrich, Glenn P.; Hazle, John .D.

2014-01-01

411

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

Microsoft Academic Search

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

Raimund Hibst; Roland Kaufmann

1991-01-01

412

Flyer Acceleration by Pulsed Ion Beam Ablation and Application for Space Propulsion  

Microsoft Academic Search

Flyer acceleration by ablation plasma pressure produced by irradiation of intense pulsed ion beam has been studied. Acceleration process including expansion of ablation plasma was simulated based on fluid model. And interaction between incident pulsed ion beam and a flyer target was considered as accounting stopping power of it. In experiments, we used ETIGO-II intense pulsed ion beam generator with

Nobuhiro Harada; Chainarong Buttapeng; Masaru Yazawa; Kenji Kashine; Weihua Jiang; Kiyoshi Yatsui

2004-01-01

413

Infrared laser ablation sample transfer for on-line liquid chromatography electrospray ionization mass spectrometry.  

PubMed

We have demonstrated an on-line laser ablation sampling system and coupling of the system to liquid chromatography (LC) using an infrared (IR) laser to ablate and transfer materials into a flowing solvent stream. With this approach, samples are deposited on a microscope slide mounted on a translation stage and ablated in transmission geometry using a pulsed mid-IR laser. The ablated material is captured in an exposed flowing solvent stream that carries the ablated material to the electrospray source. Post-ablation separation is accomplished using a capillary column downstream of the capture zone. The performance of the system was assessed using peptide and protein mixtures ablated from the target and analyzed with and without LC separation. PMID:23019163

Park, Sung-Gun; Murray, Kermit K

2012-10-01

414

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

415

Simultaneous multi-point laser ablation using a spatial light modulator  

NASA Astrophysics Data System (ADS)

Laser-microsurgery has emerged as a powerful technique for evaluating in vivo tissue mechanics; however, for incisions involving multiple pulses, only the very first pulse ablates tissue with unaltered mechanical stress; subsequent pulses ablate tissue that is recoiling from earlier ablations. To avoid this, we have developed a system for simultaneously ablating tissue at several points by using a single laser pulse shaped by a phase-only spatial light modulator (SLM). The ablating laser system is connected to a confocal microscope with a high-speed camera attachment. Using the high-speed camera and pulsed illumination, we have imaged the dynamics of multi-point ablation -- including the formation and interaction of multiple simultaneous plasmas and cavitation bubbles. We report preliminary results from simultaneous ablation of multiple spots and/or extended lines in aqueous solution, gels and fruit fly embryos.

Jayasinghe, Aroshan; Hutson, Shane

2010-03-01

416

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

Microsoft Academic Search

The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a

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

2007-01-01

417

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

418

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

SciTech Connect

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

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

2012-09-24

419

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

420

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

SciTech Connect

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

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

2003-09-30

421

Synchronized videography of plasma plume expansion during femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

Femtosecond lasers are gaining industrial interest for surface patterning and structuring because of the reduced heat effects to the surrounding material, resulting in a good quality product with a high aspect ratio. Analysis of the plasma plume generated during ablation can provide useful information about the laser-material interactions and thereby the quality of the resulting surface patterns. As a low-cost alternative to rather complicated ICCD camera setups, presented here is an approach based on filming the laser machining process with a high speed camera and tuning the frame rate of the camera to slightly lower than the laser pulse frequency. The delay in frequency between the laser and camera results in frames taken from sequential pulses. Each frame represents a later phase of plume expansion although taken from different pulses. Assuming equal plume evolution processes from pulse to pulse, the sequence of images obtained completes a plume expansion video. To test the assumption of homogeneity between sequential plumes, the camera can be tuned to the frequency of the laser, as to capture consecutive plumes at the same phase in their evolution. This approach enables a relatively low-cost, high resolution visualization of plasma plume evolution suitable for industrial micromachining applications with femtosecond lasers. Using this approach we illustrate differences in plume expansion at the example of machining homogeneous surface patterns in different liquid and gaseous processing environments.

Paolasini, Steven; Kietzig, Anne

2014-03-01

422

Thresholds of plasma formation in silicon identified by optimizing the ablation laser pulse form.  

PubMed

Using an evolutionary algorithm combined with pulse shaping, we have identified that rapid plasma formation in Silicon can occur already at a fluence of about 150 mJ/cm2 if a substantial part of the laser energy is deposited efficiently around 200 fs after an exciting laser pulse. Nonthermal solid-to-liquid phase transition leads to the increase of the deposited energy in the material. Highly charged ions have been observed in the mass spectrum. While the pulse optimization procedure allowed us to identify the plasma formation, further experiments where the influence of the laser pulse width on the ablation yield was studied and Two-Pulse-Correlation experiments provided additional proof for the appearance of rapid plasma formation. PMID:17025853