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Sample records for pulsed-laser weld pool

  1. Neural Network Modeling of Weld Pool Shape in Pulsed-Laser Aluminum Welds

    SciTech Connect

    Iskander, Y.S.; Oblow, E.M.; Vitek, J.M.

    1998-11-16

    A neural network model was developed to predict the weld pool shape for pulsed-laser aluminum welds. Several different network architectures were examined and the optimum architecture was identified. The neural network was then trained and, in spite of the small size of the training data set, the network accurately predicted the weld pool shape profiles. The neural network output was in the form of four weld pool shape parameters (depth, width, half-width, and area) and these were converted into predicted weld pool profiles with the use of the actual experimental poo1 profiles as templates. It was also shown that the neural network model could reliably predict the change from conduction-mode type shapes to keyhole-mode shapes.

  2. Optical penetration sensor for pulsed laser welding

    DOEpatents

    Essien, Marcelino; Keicher, David M.; Schlienger, M. Eric; Jellison, James L.

    2000-01-01

    An apparatus and method for determining the penetration of the weld pool created from pulsed laser welding and more particularly to an apparatus and method of utilizing an optical technique to monitor the weld vaporization plume velocity to determine the depth of penetration. A light source directs a beam through a vaporization plume above a weld pool, wherein the plume changes the intensity of the beam, allowing determination of the velocity of the plume. From the velocity of the plume, the depth of the weld is determined.

  3. Experimental and numerical investigation of temperature distribution and melt pool geometry during pulsed laser welding of Ti6Al4V alloy

    NASA Astrophysics Data System (ADS)

    Akbari, Mohammad; Saedodin, Seyfolah; Toghraie, Davood; Shoja-Razavi, Reza; Kowsari, Farshad

    2014-07-01

    This paper reports on a numerical and experimental investigation of laser welding of titanium alloy (Ti6Al4V) for modeling the temperature distribution to predict the heat affected zone (HAZ), depth and width of the molten pool. This is a transient three-dimensional problem in which, because of simplicity, the weld pool surface is considered flat. The complex physical phenomenon causing the formation of keyhole has not been considered. The temperature histories of welding process were studied. It was observed that the finite volume thermal model was in good agreement with the experimental data. Also, we predicted the temperature as a function of distance at different laser welding speeds and saw that at each welding speed, the temperature profile was decreased sharply in points close to the laser beam center, and then decreased slightly in the far region from the laser beam center. The model prediction error was found to be in the 2-17% range with most numerical values falling within 7% of the experimental values.

  4. Energy Losses Estimation During Pulsed-Laser Seam Welding

    NASA Astrophysics Data System (ADS)

    Sebestova, Hana; Havelkova, Martina; Chmelickova, Hana

    2014-06-01

    The finite-element tool SYSWELD (ESI Group, Paris, France) was adapted to simulate pulsed-laser seam welding. Besides temperature field distribution, one of the possible outputs of the welding simulation is the amount of absorbed power necessary to melt the required material volume including energy losses. Comparing absorbed or melting energy with applied laser energy, welding efficiencies can be calculated. This article presents achieved results of welding efficiency estimation based on the assimilation both experimental and simulation output data of the pulsed Nd:YAG laser bead on plate welding of 0.6-mm-thick AISI 304 stainless steel sheets using different beam powers.

  5. Investigation of Laser Parameters in Silicon Pulsed Laser Conduction Welding

    NASA Astrophysics Data System (ADS)

    Shayganmanesh, Mahdi; Khoshnoud, Afsaneh

    2016-03-01

    In this paper, laser welding of silicon in conduction mode is investigated numerically. In this study, the effects of laser beam characteristics on the welding have been studied. In order to model the welding process, heat conduction equation is solved numerically and laser beam energy is considered as a boundary condition. Time depended heat conduction equation is used in our calculations to model pulsed laser welding. Thermo-physical and optical properties of the material are considered to be temperature dependent in our calculations. Effects of spatial and temporal laser beam parameters such as laser beam spot size, laser beam quality, laser beam polarization, laser incident angle, laser pulse energy, laser pulse width, pulse repetition frequency and welding speed on the welding characteristics are assessed. The results show that how the temperature dependent thermo-physical and optical parameters of the material are important in laser welding modeling. Also the results show how the parameters of the laser beam influence the welding characteristics.

  6. Weld pool phenomena

    SciTech Connect

    David, S.A.; Vitek, J.M.; Zacharia, T.; DebRoy, T.

    1994-09-01

    During welding, the composition, structure and properties of the welded structure are affected by the interaction of the heat source with the metal. The interaction affects the fluid flow, heat transfer and mass transfer in the weld pool, and the solidification behavior of the weld metal. In recent years, there has been a growing recognition of the importance of the weld pool transport processes and the solid state transformation reactions in determining the composition, structure and properties of the welded structure. The relation between the weld pool transport processes and the composition and structure is reviewed. Recent applications of various solidification theories to welding are examined to understand the special problems of weld metal solidification. The discussion is focussed on the important problems and issues related to weld pool transport phenomena and solidification. Resolution of these problems would be an important step towards a science based control of composition, structure and properties of the weld metal.

  7. Surface separation investigation of ultrafast pulsed laser welding

    NASA Astrophysics Data System (ADS)

    Chen, Jianyong; Carter, Richard M.; Thomson, Robert R.; Hand, Duncan P.

    2016-03-01

    Techniques for joining materials, especially optical materials such as glass to structural materials such as metals, or to other optical materials, while maintaining their surface and optical properties are essential for a wide range of industrial applications. Adhesive bonding is commonly used but leads to many issues including optical surface contamination and outgassing. It is possible to generate welds using an ultra-short pulsed laser process, whereby two flat material surfaces are brought into close contact and the laser is focused through the optical material onto the interface. Highly localised melting and rapid resolidification form a strong bond between the two surfaces whilst avoiding significant heating of the surrounding material, which is important for joining materials with different thermal expansion coefficients. Previous reports on ultrafast laser welding have identified a requirement for the surface separation gap to be less than 500nm in order to avoid cracking or ablation at the interface. We have investigated techniques for increasing this gap (to reduce weld fit-up problems), and tested by bonding two surfaces with a weld-controlled gap. These gaps were generated either by a series of etched grooves on the surface of one of the substrates, or by using a cylindrical lens as a substrate. By careful optimisation of parameters such as laser power, process speed and focal position, we were able to demonstrate successful welding with a gap of up to 3μm.

  8. Monitoring of solidification crack propagation mechanism in pulsed laser welding of 6082 aluminum

    NASA Astrophysics Data System (ADS)

    von Witzendorff, P.; Kaierle, S.; Suttmann, O.; Overmeyer, L.

    2016-03-01

    Pulsed laser sources with pulse durations in the millisecond regime can be used for spot welding and seam welding of aluminum. Seam welds are generally produced with several overlapping spot welds. Hot cracking has its origin in the solidification process of individual spot welds which determines the cracking morphology along the seam welding. This study used a monitoring unit to capture the crack geometry within individual spot welds during seam welding to investigate the conditions for initiation, propagation and healing (re-melting) of solidification cracking within overlapping pulsed laser welds. The results suggest that small crack radii and high crack angles with respect to welding direction are favorable conditions for crack healing which leads to crack-free seam welds. Optimized pulse shapes were used to produce butt welds of 0.5 mm thick 6082 aluminum alloys. Tensile tests were performed to investigate the mechanical strength in the as-welded condition.

  9. Weld pool oscillation during pulsed GTA welding

    SciTech Connect

    Aendenroomer, A.J.R.; Ouden, G. den

    1996-12-31

    This paper deals with weld pool oscillation during pulsed GTA welding and with the possibility to use this oscillation for in-process control of weld penetration. Welding experiments were carried out under different welding conditions. During welding the weld pool was triggered into oscillation by the normal welding pulses or by extra current pulses. The oscillation frequency was measured both during the pulse time and during the base time by analyzing the arc voltage variation using a Fast Fourier Transformation program. Optimal results are obtained when full penetration occurs during the pulse time and partial penetration during the base time. Under these conditions elliptical overlapping spot welds are formed. In the case of full penetration the weld pool oscillates in a low frequency mode (membrane oscillation), whereas in the case of partial penetration the weld pool oscillates in a high frequency mode (surface oscillation). Deviation from the optimal welding conditions occurs when high frequency oscillation is observed during both pulse time and base time (underpenetration) or when low frequency oscillation is observed during both pulse time and base time (overpenetration). In line with these results a penetration sensing system with feedback control was designed, based on the criterion that optimal weld penetration is achieved when two peaks are observed in the frequency distribution. The feasibility of this sensing system for orbital tube welding was confirmed by the results of experiments carried out under various welding conditions.

  10. Electrochemistry Corrosion Properties of Pulsed Laser Welding Hastelloy C-276

    NASA Astrophysics Data System (ADS)

    Ma, G.; Niu, F.; Wu, D.; Qu, Y.

    Based on the welding quality requirement of Hastelloy C276 in the extreme environment, the electrochemistry corrosion property of laser welding Hastelloy C276 was evaluated in the neutral, acid and alkaline solutions, and the corroded surface was observed by the co-focal laser scanning microscope to confirm the corrosion mechanism. The results indicated, the corrosion trend of the weld was weaker than that of base metal in the neutral and acid solutions, but in the alkaline solutions, the corrosion trend of the base metal was weaker. However, the corrosion rate of the weld was much slower than that of base metal in all solutions. At the point of corrosion mechanism, in the acid and alkaline solutions, the base metal and weld showed the uniform corrosion. However, in the neutral solution, the selective corrosion and intergranular corrosion occurred in the base metal and the weld, respectively.

  11. Microstructure evolution and mechanical property of pulsed laser welded Ni-based superalloy

    NASA Astrophysics Data System (ADS)

    Ma, Guangyi; Wu, Dongjiang; Niu, Fangyong; Zou, Helin

    2015-09-01

    For evaluating the microstructure evolution and mechanical property of Ni-based Hastelloy C-276 weld joint by the pulsed laser welding, the influence of pulsed laser welding on the microstructure and mechanical property of the weld joint is investigated by the analysis of the microstructure morphology, microhardness, phase structure and tensile property. The results indicate that, in the fusion zone three sections are divided on the basis of the patterns of grain structures. In the weld joint, the element segregation is found, but the trend of brittle phase's formation is weakened. The weld microhardness presents just a little higher than that of base metal, and there is no obvious the softened heat affected zone. Meanwhile in the weld joint, the phase structure is still the face-center cubic with the tiny shift of peak positions and widened Full Width at Half-Maximum. The yield strength of weld joint is the same as that of base metal, and the tensile strength is nearly 90% of that of base metal. The decreased tensile strength is mainly attributed to the dislocation piling-up.

  12. Weld Bead Size, Microstructure and Corrosion Behavior of Zirconium Alloys Joints Welded by Pulsed Laser Spot Welding

    NASA Astrophysics Data System (ADS)

    Cai, Chuang; Li, Liqun; Tao, Wang; Peng, Genchen; Wang, Xian

    2016-07-01

    Pulsed laser spot welding of intersection points of zirconium alloys straps was performed. Weld bead size, microstructure and the corrosion behavior of weld bead were investigated. With the increasing laser peak power or number of shots, the weld width of the beads increased, the protrusion decreased and the dimple increased with further increase in heat input. The fusion zone consisted of a mixture of αZr and residual βZr phases. After annealing treatment, βNb and Zr(Fe, Nb)2 second phase particles were precipitated inter- and intragranular of αZr grains adequately. The oxide thickness of annealed weld bead was about 3.90 μm, decreased by about 18.1% relative to the 4.76 μm of as-welded specimen corroded at 400 °C and 10.3 MPa for 20 days. The corrosion resistance of annealed specimen was better than that of as-welded specimen, since the second phase particles exerted better corrosion resistance, and the content of Nb in βZr and the fraction of βZr decreased after the annealing treatment.

  13. Thin plate gap bridging study for Nd:YAG pulsed laser lap welds.

    SciTech Connect

    Roach, Robert Allen; Fuerschbach, Phillip William; Bernal, John E.; Norris, Jerome T.

    2006-01-01

    In an on going study of gap bridging for thin plate Nd:YAG laser lap welds, empirical data, high speed imaging, and computer modeling were utilized to better understand surface physics attributed to the formation and solidification of a weld pool. Experimental data indicates better gap bridging can be achieved through optimized laser parameters such as pulse length, duration, and energy. Long pulse durations at low energies generating low peak powers were found to create the highest percent of gap bridging ability. At constant peak power, gap-bridging ability was further improved by using a smaller spot diameter resulting in higher irradiances. Hence, welding in focus is preferable for bridging gaps. Gas shielding was also found to greatly impact gap-bridging ability. Gapped lap welds that could not be bridged with UHP Argon gas shielding, were easily bridged when left unshielded and exposed to only air. Incident weld angle and joint offset were also investigated for their ability to improve gap bridging. Optical filters and brightlight surface illumination enabled high-speed imaging to capture the fluid dynamics of a forming and solidifying weld pool. The effects of various laser parameters and the weld pool's interaction with the laser beam could also be observed utilizing the high-speed imaging. The work described is used to develop and validate a computer model with improved weld pool physics. Finite element models have been used to derive insight into the physics of gap bridging. The dynamics of the fluid motion within the weld pool in conjunction with the free surface physics have been the primary focus of the modeling efforts. Surface tension has been found to be a more significant factor in determining final weld pool shape than expected.

  14. Building A Simulation Model For The Prediction Of Temperature Distribution In Pulsed Laser Spot Welding Of Dissimilar Low Carbon Steel 1020 To Aluminum Alloy 6061

    SciTech Connect

    Yousef, Adel K. M.; Taha, Ziad A.; Shehab, Abeer A.

    2011-01-17

    This paper describes the development of a computer model used to analyze the heat flow during pulsed Nd: YAG laser spot welding of dissimilar metal; low carbon steel (1020) to aluminum alloy (6061). The model is built using ANSYS FLUENT 3.6 software where almost all the environments simulated to be similar to the experimental environments. A simulation analysis was implemented based on conduction heat transfer out of the key hole where no melting occurs. The effect of laser power and pulse duration was studied.Three peak powers 1, 1.66 and 2.5 kW were varied during pulsed laser spot welding (keeping the energy constant), also the effect of two pulse durations 4 and 8 ms (with constant peak power), on the transient temperature distribution and weld pool dimension were predicated using the present simulation. It was found that the present simulation model can give an indication for choosing the suitable laser parameters (i.e. pulse durations, peak power and interaction time required) during pulsed laser spot welding of dissimilar metals.

  15. Camera Would Monitor Weld-Pool Contours

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S.; Gutow, David A.

    1990-01-01

    Weld pool illuminated and viewed coaxially along welding torch. Proposed monitoring subsystem for arc welder provides image in which horizontal portions of surface of weld pool highlighted. Monitoring and analyzing subsystems integrated into overall control system of robotic welder. Control system sets welding parameters to adapt to changing conditions, maintaining surface contour giving desired pattern of reflections.

  16. Weld pool oscillation during GTA welding of mild steel

    SciTech Connect

    Xiao, Y.H.; Ouden, G. den . Dept. of Materials Science and Engineering)

    1993-08-01

    In this paper the results are reported of a study dealing with the oscillation behavior of weld pools in the case of GTA bead-on-plate welding of mild steel, Fe 360. During welding, the weld pool was brought into oscillation by applying short current pulses, and the oscillation frequency and amplitude were measured by monitoring the arc voltage. It was found that the oscillation of the partially penetrated weld pool is dominated by one of two different oscillation modes (Mode 1 and Mode 2) depending on the welding conditions, whereas the oscillation of the fully penetrated weld pool is characterized by a third oscillation mode (Mode 3). It is possible to maintain partially penetrated weld pool oscillation in Mode 1 by choosing appropriate welding conditions. Under these conditions, an abrupt decrease in oscillation frequency occurs when the weld pool transfers from partial penetration to full penetration. Thus, weld penetration can be in-process controlled by monitoring the oscillation frequency during welding.

  17. Control of Gas Tungsten Arc welding pool shape by trace element addition to the weld pool

    DOEpatents

    Heiple, C.R.; Burgardt, P.

    1984-03-13

    An improved process for Gas Tungsten Arc welding maximizes the depth/width ratio of the weld pool by adding a sufficient amount of a surface active element to insure inward fluid flow, resulting in deep, narrow welds. The process is especially useful to eliminate variable weld penetration and shape in GTA welding of steels and stainless steels, particularly by using a sulfur-doped weld wire in a cold wire feed technique.

  18. Microstructure and Mechanical Properties of Pulsed Laser Beam Welded Ti-2Al-1.5Mn Titanium Alloy Joints

    NASA Astrophysics Data System (ADS)

    Fang, Xiuyang; Liu, Hong; Zhang, Jianxun

    2014-06-01

    The microstructure and mechanical properties in the pulsed laser beam welded joints of Ti-2Al-1.5Mn titanium alloy thin sheet were investigated in this study. The results show that the original α + β-phases and the transformed α + α'-phases are found in the partially transformed heat-affected zone (HAZ) together with the remaining β-phase, and the microhardness gradually enhances in the region as the result of the increase of α'-phase. The martensitic α'-phase and the remaining β-phase are detected in the fully transformed HAZ and the fusion zone (FZ), and the highest microhardness is found in these regions in virtue of the dominant α'-phase structure. The fine α'-phase appeared in the FZ results in higher average microhardness at high welding speed. Moreover, similar to the results of microhardness test, the tensile test results mean that the HAZ and FZ are stronger than the base metal (BM). Therefore, pulsed laser beam welding is feasible for joining thin sheet of Ti-2Al-1.5Mn titanium alloy.

  19. Effect of focusing condition on molten area characteristics in micro-welding of borosilicate glass by picosecond pulsed laser

    NASA Astrophysics Data System (ADS)

    Nordin, I. H. W.; Okamoto, Y.; Okada, A.; Takekuni, T.; Sakagawa, T.

    2016-05-01

    The characteristics of the molten area are attributed not only by laser energy condition but also the focusing condition. In this study, a picosecond pulsed laser of 1064 nm in wavelength and 12.5 ps in pulse duration was used as a laser source for joining glass material. Influence of focusing condition on micro-welding of glasses was experimentally investigated by using an objective lens with and without spherical aberration correction, and its molten area was characterized. The usage of objective lens with spherical aberration correction led to a larger molten area inside the bulk material of glass even under the same pulse energy, which related to the efficient micro-welding of glass materials. In addition, an optical system with the spherical aberration correction led to a stable absorption of laser energy inside the bulk glass material, stabilizing the shape of molten area, which resulted in the reliable weld joint. On the other hand, breaking strength of the specimens with spherical aberration correction was higher than that without spherical aberration correction. Therefore, it is concluded that the focusing condition with spherical aberration correction led to the larger and stable molten area, which resulted in higher joining strength in micro-welding of glass materials.

  20. Weld Pool Stability in the Flat Position

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Coan, B.

    1999-01-01

    The Soft Plasma Arc (SPA) process was devised to avoid interactions between backshield and full penetration mode plasma jet in welding 2195 aluminum-lithium alloy. Occasional sudden and mysterious losses in penetration were encountered in flat position SPA welding. To understand what was happening a model of the dynamics of the molten metal meniscus at the root of the weld was worked out. When the power input to the weld P(sub in) exceeds the power leakage P(sub out) the difference in power is absorbed by an increase in the molten weld pool volume V, Rho X L(SUB m) X (d(V)/dt)) = P(sub in) - P(sub out) where rho is the density and L(sub m) the specific heat of the weld metal.

  1. Numerical Study for Gta Weld Shape Variation by Coupling Welding Arc and Weld Pool

    NASA Astrophysics Data System (ADS)

    Dong, Wenchao; Lu, Shanping; Li, Dianzhong; Li, Yiyi

    A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding currents. Numerical calculations to the weld pool development are carried out for moving GTA welding on SUS304 stainless steel with different oxygen contents 30 ppm and 220 ppm, respectively. The results show that the plasma drag force is another dominating driving force affecting the liquid pool flow pattern, except for the Marangoni force. The different welding currents will change the temperature distribution and plasma drag force on the pool surface, and affect the strength of Marangoni convection and the weld shape. The weld D/W ratio initially increases, followed by a constant value around 0.5 with the increasing welding current under high oxygen content. The weld D/W ratio under the low oxygen content slightly decreases with the increasing welding current. The predicted weld shape by simulation agrees well with experimental results.

  2. The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture

    NASA Astrophysics Data System (ADS)

    AlShaer, A. W.; Li, L.; Mistry, A.

    2014-12-01

    Laser welding of aluminium alloys typically results in porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation. This research focuses on porosity reduction in laser welding of aluminium alloy. Weld quality was investigated for two joints, fillet edge and flange couch joints. The effect of laser cleaning on porosity reduction after welding was investigated. It was found that laser cleaning reduced porosity less than 1% in both joints. Weld dimensions and strength were evaluated and discussed for both types of joints.

  3. 3D finite element simulation of TIG weld pool

    NASA Astrophysics Data System (ADS)

    Kong, X.; Asserin, O.; Gounand, S.; Gilles, P.; Bergheau, J. M.; Medale, M.

    2012-07-01

    The aim of this paper is to propose a three-dimensional weld pool model for the moving gas tungsten arc welding (GTAW) process, in order to understand the main factors that limit the weld quality and improve the productivity, especially with respect to the welding speed. Simulation is a very powerful tool to help in understanding the physical phenomena in the weld process. A 3D finite element model of heat and fluid flow in weld pool considering free surface of the pool and traveling speed has been developed for the GTAW process. Cast3M software is used to compute all the governing equations. The free surface of the weld pool is calculated by minimizing the total surface energy. The combined effects of surface tension gradient, buoyancy force, arc pressure, arc drag force to drive the fluid flow is included in our model. The deformation of the weld pool surface and the welding speed affect fluid flow, heat flow and thus temperature gradients and molten pool dimensions. Welding trials study is presented to compare our numerical results with macrograph of the molten pool.

  4. A unified model of coupled arc plasma and weld pool for double electrodes TIG welding

    NASA Astrophysics Data System (ADS)

    Wang, Xinxin; Fan, Ding; Huang, Jiankang; Huang, Yong

    2014-07-01

    A three-dimensional model containing tungsten electrodes, arc plasma and a weld pool is presented for double electrodes tungsten inert gas welding. The model is validated by available experimental data. The distributions of temperature, velocity and pressure of the coupled arc plasma are investigated. The current density, heat flux and shear stress over the weld pool are highlighted. The weld pool dynamic is described by taking into account buoyance, Lorentz force, surface tension and plasma drag force. The turbulent effect in the weld pool is also considered. It is found that the temperature and velocity distributions of the coupled arc are not rotationally symmetrical. A similar property is also shown by the arc pressure, current density and heat flux at the anode surface. The surface tension gradient is much larger than the plasma drag force and dominates the convective pattern in the weld pool, thus determining the weld penetration. The anodic heat flux and plasma drag force, as well as the surface tension gradient over the weld pool, determine the weld shape and size. In addition, provided the welding current through one electrode increases and that through the other decreases, keeping the total current unchanged, the coupled arc behaviour and weld pool dynamic change significantly, while the weld shape and size show little change. The results demonstrate the necessity of a unified model in the study of the arc plasma and weld pool.

  5. Role of welding parameters in determining the geometrical appearance of weld pool

    SciTech Connect

    Kovacevic, R.; Cao, Z.N.; Zhang, Y.M.

    1996-10-01

    A three-dimensional numerical model is developed to describe the fluid flow and heat transfer in weld pools. Both full penetration and free deformation of the top and bottom weld pool surfaces are considered. Temperature distribution and fluid flow field are obtained. In order to analyze the influence of welding parameters on the geometrical appearance of weld pools, a normalized model is developed to characterize the geometrical appearance of weld pools. It is found that welding current can significantly affect the geometrical shape. When welding current increases, the curvature of the pool boundary at the trailing end increases. The effect of the welding speed on the geometrical appearance is slight, although its influence on the pool size is great. In the interest range of arc length (from 1 mm to 4 mm), the arc length can affect both the size and the shape of the weld pool. However, compared with the welding current and speed, its influences are much weaker, GTA welding experiments are performed to verify the validity of the numerical models. The appearance of weld pools was obtained by using machine vision and a high-shutter speed camera. It is found that the calculated results have a good agreement with the experimental ones.

  6. An insight to the mechanism of weld penetration in dissimilar pulsed laser welding of niobium and Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Torkamany, M. J.; Malek Ghaini, F.; Poursalehi, R.

    2016-05-01

    In laser welding of Ti-6Al-4V to niobium, the interaction of laser with the two metals is such that at the investigated laser conditions there will be conduction mode on the Nb side and keyhole on the Ti side. Thus the weld pool is not developed symmetrically as there will not be sufficient penetration in the higher melting point higher conductivity niobium side. The mechanisms of energy absorption and effective melting in dissimilar laser welding are analyzed. It is shown that more penetration into niobium is obtained when the laser energy is absorbed by Ti-6Al-4V and then the molten Ti-6Al-4V dissolves the niobium metal.

  7. Influence of the arc plasma parameters on the weld pool profile in TIG welding

    NASA Astrophysics Data System (ADS)

    Toropchin, A.; Frolov, V.; Pipa, A. V.; Kozakov, R.; Uhrlandt, D.

    2014-11-01

    Magneto-hydrodynamic simulations of the arc and fluid simulations of the weld pool can be beneficial in the analysis and further development of arc welding processes and welding machines. However, the appropriate coupling of arc and weld pool simulations needs further improvement. The tungsten inert gas (TIG) welding process is investigated by simulations including the weld pool. Experiments with optical diagnostics are used for the validation. A coupled computational model of the arc and the weld pool is developed using the software ANSYS CFX. The weld pool model considers the forces acting on the motion of the melt inside and on the surface of the pool, such as Marangoni, drag, electromagnetic forces and buoyancy. The experimental work includes analysis of cross-sections of the workpieces, highspeed video images and spectroscopic measurements. Experiments and calculations have been performed for various currents, distances between electrode and workpiece and nozzle diameters. The studies show the significant impact of material properties like surface tension dependence on temperature as well as of the arc structure on the weld pool behaviour and finally the weld seam depth. The experimental weld pool profiles and plasma temperatures are in good agreement with computational results.

  8. Modeling of the Weld Shape Development During the Autogenous Welding Process by Coupling Welding Arc with Weld Pool

    NASA Astrophysics Data System (ADS)

    Dong, Wenchao; Lu, Shanping; Li, Dianzhong; Li, Yiyi

    2010-10-01

    A numerical model of the welding arc is coupled to a model for the heat transfer and fluid flow in the weld pool of a SUS304 stainless steel during a moving GTA welding process. The described model avoids the use of the assumption of the empirical Gaussian boundary conditions, and at the same time, provides reliable boundary conditions to analyze the weld pool. Based on the two-dimensional axisymmetric numerical modeling of the argon arc, the heat flux to workpiece, the input current density, and the plasma drag stress are obtained. The arc temperature contours, the distributions of heat flux, and current density at the anode are in fair agreement with the reported experimental results. Numerical simulation and experimental studies to the weld pool development are carried out for a moving GTA welding on SUS304 stainless steel with different oxygen content from 30 to 220 ppm. The calculated result show that the oxygen can change the Marangoni convection from outward to inward direction on the liquid pool surface and make the wide shallow weld shape become narrow deep one. The calculated result for the weld shape and weld D/W ratio agrees well with the experimental one.

  9. Dynamic behavior of the weld pool in stationary GMAW

    NASA Astrophysics Data System (ADS)

    Chapuis, J.; Romero, E.; Bordreuil, C.; Soulié, F.; Fras, G.

    2010-06-01

    Because hump formation limits welding productivity, better understanding of the humping phenomena during the welding process is needed to access to process modifications that decrease the tendency for hump formation and then allow higher productivity welding. From a physical point of view, the mechanism identified is the Rayleigh instability initiated by strong surface tension gradient which induces a variation of kinetic flow. But the causes of the appearance of this instability are not yet well explained. Because of the phenomena complex and multi-physics, we chose in first step to conduct an analysis of the characteristic times involved in weld pool in pulsed stationary GMAW. The goal is to study the dynamic behavior of the weld pool, using our experimental multi physics approach. The experimental tool and methodology developed to understand these fast phenomena are presented first: frames acquisition with high speed digital camera and specific optical devices, numerical library. The analysis of geometric parameters of the weld pool during welding operation are presented in the last part: we observe the variations of wetting angles (or contact lines angles), the base and the height of the weld pool (macro-drop) versus weld time.

  10. Real time polarization imaging of weld pool surface

    NASA Astrophysics Data System (ADS)

    Stolz, C.; Coniglio, N.; Mathieu, A.; Aubreton, O.

    2015-04-01

    The search for an efficient on-line monitoring system focused on the real-time analysis of arc welding quality is an active area of research. The topography and the superficial temperature field of the weld pool can provide important information which can be used to regulate the welding parameters for depositing consistent welds. One difficulty relies on accessing this information despite the bright dazzling welding arc. In the present work, Stokes polarimetry and associated shape-from-polarization methods are applied for the analysis of the weld pool through its 810 nm-wavelength infrared emissions. The obtained information can provide a better understanding of the process, such as the usage of the topography to seek Marangoni flows direction, or to have a denser 3D map to improve numerical simulation models.

  11. A study of arc force, pool depression and weld penetration during gas tungsten arc welding

    SciTech Connect

    Rokhlin, S.I.; Guu, A.C. . Dept. of Welding Engineering)

    1993-08-01

    Weld pool depression, arc force, weld penetration, and their interrelations have been studied as a function of welding current. Pool depression and welding arc force have been measured simultaneously using a recently developed technique. The authors found quadratic dependence of arc force on current, confirming similar findings in previous studies. Pool depression is essentially zero below a threshold level of current (200 A in this experiment) and then increases quadratically with current. A perfectly linear relation between arc force and pool depression was found in the current range from 200 to 350 A, with pool depression onset at about 0.35 g force (0.34 [center dot] 10[sup [minus]2]N). The total surface tension and gravitational forces were calculated, from the measured surface topography, and found to be about five times that required to balance the arc force at 300 A. Thus electromagnetic and hydrodynamic forces must be taken into account to explain the measured levels of pool depression. The relation between weld penetration and pool depression for different welding currents has been established. Three distinct regimes of weld penetration on weld current were found.

  12. Experimental and Numerical Investigation of an Electromagnetic Weld Pool Control for Laser Beam Welding

    NASA Astrophysics Data System (ADS)

    Bachmann, M.; Avilov, V.; Gumenyuk, A.; Rethmeier, M.

    The objective of this study was to investigate the influence of externally applied magnetic fields on the weld quality in laser beam welding. The optimization of the process parameters was performed using the results of computer simulations. Welding tests were performed with up to 20 kW laser beam power. It was shown that the AC magnet with 3 kW power supply allows for a prevention of the gravity drop-out for full penetration welding of 20 mm thick stainless steel plates. For partial penetration welding it was shown that an0.5 T DC magnetic field is enough for a suppression of convective flows in the weld pool. Partial penetration welding tests with 4 kW beam power showed that the application of AC magnetic fields can reduce weld porosity by a factor of 10 compared to the reference joints. The weld surface roughness was improved by 50%.

  13. Effects of surface active elements on weld pool fluid flow and weld penetration in gas metal arc welding

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Tsai, H. L.

    2001-06-01

    This article presents a mathematical model simulating the effects of surface tension (Maragoni effect) on weld pool fluid flow and weld penetration in spot gas metal arc welding (GMAW). Filler droplets driven by gravity, electromagnetic force, and plasma arc drag force, carrying mass, thermal energy, and momentum, periodically impinge onto the weld pool. Complicated fluid flow in the weld pool is influenced by the droplet impinging momentum, electromagnetic force, and natural convection due to temperature and concentration gradients, and by surface tension, which is a function of both temperature and concentration of a surface active element (sulfur in the present study). Although the droplet impinging momentum creates a complex fluid flow near the weld pool surface, the momentum is damped out by an “up-and-down” fluid motion. A numerical study has shown that, depending upon the droplet’s sulfur content, which is different from that in the base metal, an inward or outward surface flow of the weld pool may be created, leading to deep or shallow weld penetration. In other words, it is primarily the Marangoni effect that contributes to weld penetration in spot GMAW.

  14. High-power CW and long-pulse lasers in the green wavelength regime for copper welding

    NASA Astrophysics Data System (ADS)

    Pricking, Sebastian; Huber, Rudolf; Klausmann, Konrad; Kaiser, Elke; Stolzenburg, Christian; Killi, Alexander

    2016-03-01

    We report on industrial high-power lasers in the green wavelength regime. By means of a thin disk oscillator and a resonator-internal nonlinear crystal for second harmonic generation we are able to extract up to 8 kW pulse power in the few-millisecond range at a wavelength of 515 nm with a duty cycle of 10%. Careful shaping and stabilization of the polarization and spectral properties leads to a high optical-to-optical efficiency larger than 55%. The beam parameter product is designed and measured to be below 5 mm·mrad which allows the transport by a fiber with a 100 μm core diameter. The fiber and beam guidance optics are adapted to the green wavelength, enabling low transmission losses and stable operation. Application tests show that this laser is perfectly suited for copper welding due to the superior absorption of the green wavelength compared to IR, which allows us to produce weld spots with an unprecedented reproducibility in diameter and welding depth. With an optimized set of parameters we could achieve a splatter-free welding process of copper, which is crucial for welding electronic components. Furthermore, the surface condition does not influence the welding process when the green wavelength is used, which allows to skip any expensive preprocessing steps like tin-coating. With minor changes we could operate the laser in cw mode and achieved up to 1.7 kW of cw power at 515 nm with a beam parameter product of 2.5 mm·mrad. These parameters make the laser perfectly suitable for additional applications such as selective laser melting of copper.

  15. Welding pool measurement using thermal array sensor

    NASA Astrophysics Data System (ADS)

    Cho, Chia-Hung; Hsieh, Yi-Chen; Chen, Hsin-Yi

    2015-08-01

    Selective laser melting (SLM) is an additive manufacturing (AM) technology that uses a high-power laser beam to melt metal powder in chamber of inert gas. The process starts by slicing the 3D CAD data as a digital information source into layers to create a 2D image of each layer. Melting pool was formed by using laser irradiation on metal powders which then solidified to consolidated structure. In a selective laser melting process, the variation of melt pool affects the yield of a printed three-dimensional product. For three dimensional parts, the border conditions of the conductive heat transport have a very large influence on the melt pool dimensions. Therefore, melting pool is an important behavior that affects the final quality of the 3D object. To meet the temperature and geometry of the melting pool for monitoring in additive manufacturing technology. In this paper, we proposed the temperature sensing system which is composed of infrared photodiode, high speed camera, band-pass filter, dichroic beam splitter and focus lens. Since the infrared photodiode and high speed camera look at the process through the 2D galvanometer scanner and f-theta lens, the temperature sensing system can be used to observe the melting pool at any time, regardless of the movement of the laser spot. In order to obtain a wide temperature detecting range, 500 °C to 2500 °C, the radiation from the melting pool to be measured is filtered into a plurality of radiation portions, and since the intensity ratio distribution of the radiation portions is calculated by using black-body radiation. The experimental result shows that the system is suitable for melting pool to measure temperature.

  16. Stability of Full Penetration, Flat Position Weld Pools

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.; Coan, Al. B.

    1999-01-01

    The dynamics of the dropthrough distance of a full penetration, flat position weld pool is described. Close to incipient root side penetration the dropthrough is metastable, so that a small drop in power can cause a loss of penetration if not followed soon enough by a compensating rise in power. The SPA (Soft Plasma Arc) process with higher pressure on top of the weld pool loses penetration more quickly than the GTA (Gas Tungsten Arc) process. 2195 aluminum-lithium alloy with a lower surface tension loses penetration more quickly than 2219 aluminum alloy. An instance of loss of penetration of a SPA weld in 2195 aluminum-lithium alloy is discussed in the light of the model.

  17. RAPID COMMUNICATION: Observation of a dynamic specular weld pool surface

    NASA Astrophysics Data System (ADS)

    Zhang, Y. M.; Song, H. S.; Saeed, G.

    2006-06-01

    Observation and measurement of a weld pool surface is a key towards the development of next generation intelligent welding machines which can mimic a skilled human welder to a certain extent. However, the bright arc radiation and the specular surface complicate the observation and measurement task. This paper proposes a novel method to turn the difficulty of the specular surface into an advantage by exploiting the difference between propagation of an illumination laser and the arc plasma. The governing law is simply the reflection law which can provide the base for the computation of the weld pool surface. Experimental results verified the effectiveness of the proposed method in acquiring clear images in the presence of the bright arc.

  18. Reflection of illumination laser from gas metal arc weld pool surface

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoji; Zhang, Yu Ming

    2009-11-01

    The weld pool is the core of the welding process where complex welding phenomena originate. Skilled welders acquire their process feedback primarily from the weld pool. Observation and measurement of the three-dimensional weld pool surface thus play a fundamental role in understanding and future control of complex welding processes. To this end, a laser line is projected onto the weld pool surface in pulsed gas metal arc welding (GMAW) and an imaging plane is used to intercept its reflection from the weld pool surface. Resultant images of the reflected laser are analyzed and it is found that the weld pool surface in GMAW does specularly reflect the projected laser as in gas tungsten arc welding (GTAW). Hence, the weld pool surface in GMAW is also specular and it is in principle possible that it may be observed and measured by projecting a laser pattern and then intercepting and imaging the reflection from it. Due to high frequencies of surface fluctuations, GMAW requires a relatively short time to image the reflected laser.

  19. Electrochemical effects on weld pool chemistry in submerged arc and dc electroslag welding

    SciTech Connect

    Blander, M.; Olson, D.L.

    1986-01-01

    Electrochemical reactions could be an important factor governing the chemistry of weld pools in dc welding. The anodic reaction at the weld wire-slag interface leads to a relatively high Po/sub 2/ which leads to the formation of an oxide nO/sup 2 -/ + M(metal) ..-->.. MO/sub n/ + 2ne where M is a metal at the weld wire-slag interface and n is related to the valence of M in the oxide. After the molten weld wire forms a droplet which separates from the wire, the electrochemical reaction ceases and the oxide dissolves in the flux. The cathodic reactions at the weld pool lead to the electrodeposition of metals M/sup 2 +/(slag) + 2e ..-->.. M(metal); Si/sup 4 +/(slag) + 4e ..-->.. Si(metal) where M can be Fe/sup 2 +/, Mn/sup 2 +/. or other metals which are electrodeposited at the interface. The relative amounts of all these deposits wil be readjusted by chemical reactions such as Si(metal) + 2MO(slag) ..-->.. SiO/sub 2/(slag) + 2M(metal); Mn(metal) + FeO(slag) ..-->.. MnO(slag) + Fe(metal). The resultant changes in the compositions of the weld metal and the slag depend on the rates of the electrodeposition reactions relative to the rates of the back reactions. If the proposed mechanism is correct, experimental data would indicate that both the electrochemical and back reactions appear to be important. Analogous electrochemical reactions can occur at metal-plasma interfaces.

  20. Detectability of penetration depth based on weld pool geometry and process emission spectrum in laser welding of copper

    NASA Astrophysics Data System (ADS)

    Özmert, Alp; Neisser-Deiters, Paul; Drenker, Alexander

    2014-05-01

    Laser welding is a promising joining process for copper interconnections. A key criterion of quality for these welds is the penetration depth. The penetration depth is subject to intrinsic variation, i.e. by the nature of the welding process. Online detection of penetration depth enables quality assurance and furthermore welding of joint configurations with tighter tolerances via closed-loop control. Weld pool geometry and keyhole optical emission in the wavelength interval of 400-1100 nm are investigated with regard to how suitable they are for the detection of penetration depth in laser welding of copper Cu-ETP. Different penetration depths were induced by stepwise modulation of laser power in bead-on-plate welds. The welds have been monitored with illuminated high-speed videography of the work piece surface and spectrometry. Increase of the weld pool length (in direction of travel) corresponding to increase in penetration depth has been observed while no noticeable change was observed of the weld pool width (transverse to the direction of travel). No significant lines were observed in the spectrum. The radiant power in VIS-spectrum was observed to increase with increasing penetration depth as well. As future work, with increasing understanding and experimental data, online monitoring by indirectly measuring the penetration depth would be possible. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 260153 (QCOALA: Quality Control for Aluminium Laser-Welded Assemblies).

  1. Analysis of Bubble Flow in the Deep-Penetration Molten Pool of Vacuum Electron Beam Welding

    NASA Astrophysics Data System (ADS)

    Luo, Yi; Wan, Rui; Zhu, Yang; Xie, Xiaojian

    2015-03-01

    Based on the vacuum electron beam welding with deep-penetration process, the convection phenomenon of the bubble flow in partially penetrated and fully penetrated molten pool of AZ91D magnesium alloy was simulated under the unsteady-state conditions. At the same time, the distributions of the cavity-type defects in deep-penetration weld were studied. The results showed that the cavity-type defects are more prone to distribute at the bottom of the weld and accumulate along the axis of the weld for the partially penetrated weld seam; there is a high incidence of cavity-type defects in the middle of the weld for the fully penetrated weld seam. As a smooth escape channel for the gas phase is formed in the fully penetrated molten pool, the possibility of gas escaping is much higher than that in the partially penetrated molten pool. A high liquid convection velocity is more conducive to the escape of the gas in molten pool. The liquid convection velocity in the fully penetrated molten pool is higher than that in the partially penetrated molten pool. So, the final gas fraction in the fully penetrated molten pool is low. Therefore, the appearance of cavity-type defects in the fully penetrated weld seam is less than that in the partially penetrated weld seam.

  2. In situ observations of weld pool solidification using transparent metal-analog systems

    NASA Astrophysics Data System (ADS)

    Trivedi, R.; David, S. A.; Eshelman, M. A.; Vitek, J. M.; Babu, S. S.; Hong, T.; DebRoy, T.

    2003-04-01

    The dynamics of weld solidification were observed in situ using a laser welding process on transparent organic materials systems. Succinonitrile was used to simulate a pure metal system and succinonitrile with 1.2 wt. % acetone was used to simulate an alloy system. Observed weld pool shapes in succinonitrile were in good agreement with theoretical heat transfer calculations. The dynamics of weld pool shape in the succinonitrile-acetone system were related to complex interactions between grain orientation, grain selection, and dendrite orientations, which depend strongly on welding speed. An increase in welding speed leads to a transition from a steady-state to a nonsteady-state weld pool shape. Several other phenomena, including epitaxial growth, grain selection process, grain boundary melting, and porosity formation, were also observed.

  3. Analytical real-time measurement of a three-dimensional weld pool surface

    NASA Astrophysics Data System (ADS)

    Zhang, WeiJie; Wang, XueWu; Zhang, YuMing

    2013-11-01

    The ability to observe and measure weld pool surfaces in real-time is the core of the foundation for next generation intelligent welding that can partially imitate skilled welders who observe the weld pool to acquire information on the welding process. This study aims at the real-time measurement of the specular three-dimensional (3D) weld pool surface under a strong arc in gas tungsten arc welding (GTAW). An innovative vision system is utilized in this study to project a dot-matrix laser pattern on the specular weld pool surface. Its reflection from the surface is intercepted at a distance from the arc by a diffuse plane. The intercepted laser dots illuminate this plane producing an image showing the reflection pattern. The deformation of this reflection pattern from the projected pattern (e.g. the dot matrix) is used to derive the 3D shape of the reflection surface, i.e., the weld pool surface. Based on careful analysis, the underlying reconstruction problem is formulated mathematically. An analytic solution is proposed to solve this formulated problem resulting in the weld pool surface being reconstructed on average in 3.04 ms during welding experiments. A vision-based monitoring system is thus established to measure the weld pool surface in GTAW in real-time. In order to verify the effectiveness of the proposed reconstruction algorithm, first numerical simulation is conducted. The proposed algorithm is then tested on a spherical convex mirror with a priori knowledge of its geometry. The detailed analysis of the measurement error validates the accuracy of the proposed algorithm. Results from the real-time experiments verify the robustness of the proposed reconstruction algorithm.

  4. Simulation of metal transfer and weld pool development in gas metal arc welding of thin sheet metals

    NASA Astrophysics Data System (ADS)

    Wang, Fang

    Gas metal arc welding (GMAW) is the most commonly used arc welding method in industry for joining steels and aluminum alloys. But due to the mathematical difficulties associated with the free surface motion of the molten droplet and the weld pool, the process is not well understood and the development of new welding procedures in the manufacturing industry highly depends on expensive, time-consuming and experience-based trial and error. In this dissertation, numerical methods are developed to overcome the difficulties and to simulate the metal transfer and weld pool development in the GMAW of sheet metals. The simulations are validated by experiments and used to study an industrial welding process. A numerical procedure is first developed to model the free surface motion in fusion welding processes. Thermal and electromagnetic models are integrated with the fluid models. Recommendations are made on the selection and improvement of publicly available numerical algorithms, while alternative methods are also reviewed. A model combining the enthalpy, effective-viscosity and volume-of-fluid methods is then developed to simulate the metal transfer process in globular, spray and short-circuiting transfer modes. The model not only describes the influence of gravity, electromagnetic force and surface tension on droplet profile and transfer frequency, but also models the nonisothermal phenomena such as heat transfer and phase change. The melting front motion, the droplet detachment and oscillation, the satellite formation and the fluid convection within the droplet are analyzed. It has been found that the taper formation in spray transfer is closely related to the heat input on the unmelted portion of the welding wire, and the taper formation affects the globular-spray transition by decelerating the transfer process. Experiments with a high-speed motion analyzer validate the simulation results. The model is then extended to simulate the initiation, development and

  5. Experimental characterization of the weld pool flow in a TIG configuration

    NASA Astrophysics Data System (ADS)

    Stadler, M.; Masquère, M.; Freton, P.; Franceries, X.; Gonzalez, J. J.

    2014-11-01

    Tungsten Inert Gas (TIG) welding process relies on heat transfer between plasma and work piece leading to a metallic weld pool. Combination of different forces produces movements on the molten pool surface. One of our aims is to determine the velocity on the weld pool surface. This provides a set of data that leads to a deeper comprehension of the flow behavior and allows us to validate numerical models used to study TIG parameters. In this paper, two diagnostic methods developed with high speed imaging for the determination of velocity of an AISI 304L stainless steel molten pool are presented. Application of the two methods to a metallic weld pool under helium with a current intensity of 100 A provides velocity values around 0.70 m/s which are in good agreement with literature works.

  6. Use of Aria to simulate laser weld pool dynamics for neutron generator production.

    SciTech Connect

    Noble, David R.; Notz, Patrick K.; Martinez, Mario J.; Kraynik, Andrew Michael

    2007-09-01

    This report documents the results for the FY07 ASC Integrated Codes Level 2 Milestone number 2354. The description for this milestone is, 'Demonstrate level set free surface tracking capabilities in ARIA to simulate the dynamics of the formation and time evolution of a weld pool in laser welding applications for neutron generator production'. The specialized boundary conditions and material properties for the laser welding application were implemented and verified by comparison with existing, two-dimensional applications. Analyses of stationary spot welds and traveling line welds were performed and the accuracy of the three-dimensional (3D) level set algorithm is assessed by comparison with 3D moving mesh calculations.

  7. Welding deviation detection algorithm based on extremum of molten pool image contour

    NASA Astrophysics Data System (ADS)

    Zou, Yong; Jiang, Lipei; Li, Yunhua; Xue, Long; Huang, Junfen; Huang, Jiqiang

    2016-01-01

    The welding deviation detection is the basis of robotic tracking welding, but the on-line real-time measurement of welding deviation is still not well solved by the existing methods. There is plenty of information in the gas metal arc welding(GMAW) molten pool images that is very important for the control of welding seam tracking. The physical meaning for the curvature extremum of molten pool contour is revealed by researching the molten pool images, that is, the deviation information points of welding wire center and the molten tip center are the maxima and the local maxima of the contour curvature, and the horizontal welding deviation is the position difference of these two extremum points. A new method of weld deviation detection is presented, including the process of preprocessing molten pool images, extracting and segmenting the contours, obtaining the contour extremum points, and calculating the welding deviation, etc. Extracting the contours is the premise, segmenting the contour lines is the foundation, and obtaining the contour extremum points is the key. The contour images can be extracted with the method of discrete dyadic wavelet transform, which is divided into two sub contours including welding wire and molten tip separately. The curvature value of each point of the two sub contour lines is calculated based on the approximate curvature formula of multi-points for plane curve, and the two points of the curvature extremum are the characteristics needed for the welding deviation calculation. The results of the tests and analyses show that the maximum error of the obtained on-line welding deviation is 2 pixels(0.16 mm), and the algorithm is stable enough to meet the requirements of the pipeline in real-time control at a speed of less than 500 mm/min. The method can be applied to the on-line automatic welding deviation detection.

  8. Weld pool penetration measurement using ultrasound with thermal gradient correction factors

    NASA Astrophysics Data System (ADS)

    Anderton, John Martin

    Weld penetration is critical to final weld performance. There are many techniques for determining surface parameters of weld pools but the transient nature of the pools, high temperatures and intense electromagnetic energy make direct measurement of the penetration of weld pools difficult. In order to determine weld pool penetration ultrasonically from below the weld pool it is necessary to compensate for the variation in the time of flight of the ultrasound wave due to temperature gradients. This requires both a precise understanding of the location and magnitude of the temperature gradients and the time of flight of ultrasound at the range of temperatures seen in the gradients. Given this information it is possible to develop a correction factor to an ultrasonic time of flight reading that accurately represents the actual penetration of a weld pool. This research examines the electroslag surfacing (ESS) processing of AISI 1005 low carbon steel clad onto a ductile iron substrate. The high temperature cladding on low temperature substrate provides a deep weld penetration. Ultrasonic time of flight measurements were made from a piezoelectric transducer on the backside of the substrate to the solid/liquid interface of the weld pool during welding. The speed of ultrasound over a range of temperatures was determined from furnace heated ductile iron substrates. The sample was stepped and contact piezoelectric methods used to determine time of flight. A finite element model was developed and analyzed to predict thermal gradients in the substrate around the weld pool. The model was correlated to thermocouple data of substrate heating during welding. The predicted thermal gradients and speed/temperature curves are combined with the time of flight measurement to determine the location of the solid/liquid weld interface. An automated seam tracking system for ESS was also developed. This system utilizes a line laser at right angles to the view of a CCD camera which

  9. Pulsed laser microtomograph

    NASA Astrophysics Data System (ADS)

    Antonov, V. B.; Bonch-Bruevich, A. M.; Vasil'Ev, V. I.; Ionov, L. N.; Nikolaev, S. D.; Starobogatov, I. O.

    1994-12-01

    This paper describes a pulsed laser tomographic apparatus that has been implemented in practice and has a spatial resolution of 2-5 microns in the transverse direction and approximately 70 microns in the probe-radiation propagation direction. Experiments have been performed with model objects. Results have been obtained that confirm the possibility of early diagnosis of skin mycoses that cannot be diagnosed by existing methods.

  10. The influence of arc plasma parameters on the form of a welding pool

    NASA Astrophysics Data System (ADS)

    Frolov, V. Ya.; Toropchin, A. I.

    2015-07-01

    The influence of the Marangoni force on the form of a welding pool has been considered. Results of computer simulation of the processes of welding arc generation with a non-consumable tungsten electrode in inert gas are shown. The experimental results are reported and comparatively analyzed. The calculations were carried out in a package of applied programs at various currents.

  11. Gravitational effects on weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding on 304 stainless steel, nickel, and aluminum-4 wt.% copper alloy

    NASA Astrophysics Data System (ADS)

    Kang, Namhyun

    The objective of the present work was to investigate effects of gravitational (acceleration) level and orientation on Ni 200 alloy (99.5% Ni purity), 304 stainless steel, and Al-4 wt.% Cu alloy during gas tungsten arc welding (GTAW) and laser beam welding (LBW). Main characterization was focused on the weld pool shape, microstructure, and solute distribution as a function of gravitational level and orientation. The welds were divided into two classes, i.e., 'stable' and 'unstable' welds, in view of the variation of weld pool shape as a function of gravitational level and orientation. In general, higher arc current and translational GTAW produced more significant effects of gravitational orientation on the weld pool shape than the case of lower arc current and spot welding. Cross-sectional area (CSA) was a secondary factor in determining the stability of weld pool shape. For the 'stable' weld of 304 stainless steel GTAW, the II-U weld showed less convexity in the pool bottom and more depression of the free surface, therefore producing deeper penetration (10--20%) than the case of II-D weld. The II-D weld of 304 stainless steel showed 31% deeper penetration, 28% narrower width, and more hemispherical shape of the weld pool than the case of II-U weld. For GTAW on 304 stainless steel, gravitational level variation from low gravity (LG ≈ 1.2 go) to high gravity (HG ≈ 1.8 go) caused 10% increase in width and 10% decrease in depth while maintaining the overall weld pool volume. Furthermore, LBW on 304 stainless steels showed mostly constant shape of weld pool as a function of gravitational orientation. GTAW on Ni showed similar trends of weld pool shape compared with GTAW on 304 stainless steel, i.e., the weld pool became unstable by showing more penetration in the II-D weld for slower arc translational velocity (V a) and larger weld pool size. However, the Ni weld pool shape had greater stability of the weld pool shape with respect to the gravitational orientation

  12. Nanofabrication with Pulsed Lasers

    PubMed Central

    2010-01-01

    An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics. PMID:20672069

  13. Nanofabrication with Pulsed Lasers

    NASA Astrophysics Data System (ADS)

    Kabashin, A. V.; Delaporte, Ph.; Pereira, A.; Grojo, D.; Torres, R.; Sarnet, Th.; Sentis, M.

    2010-03-01

    An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser-matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.

  14. Reconstructing a three-dimensional P-GMAW weld pool shape from a two-dimensional visual image

    NASA Astrophysics Data System (ADS)

    Guangjun, Zhang; Zhihong, Yan; Lin, Wu

    2006-07-01

    The online detection of the three-dimensional (3D) shape of a weld pool is a key unsolved question for weld shape control. In this paper, a method to reconstruct the 3D shape of a weld pool boundary from a two-dimensional (2D) visual image is proposed. Firstly, a new 3D model was developed to describe the weld pool geometry in pulsed gas metal arc welding (P-GMAW). In this model, four parameters could be used to determine the weld pool shape: the maximum width W, the length of the pool tail L, the height of the rear of the pool H and the projection of the rear angle onto the work piece plane θL. Then, the clear weld pool images from the P-GMAW were captured from the upper side, and a series of algorithms were developed to extract the model geometrical parameters from these images. Finally, the 3D shape of the weld pool was reconstructed from the 2D images. The results were then validated with metallograph observations. The measurement error of this method was investigated, and methods for improvement were discussed.

  15. Effect of laser beam offset on microstructure and mechanical properties of pulsed laser welded BTi-6431S/TA15 dissimilar titanium alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Hu, Shengsun; Shen, Junqi; Li, Dalong; Bu, Xianzheng

    2015-11-01

    Laser beam welding was used to weld dissimilar joints in BTi-6431S/TA15 titanium alloys. The effect of laser beam offset on microstructural characterizations and mechanical properties of the joints were investigated. Microstructural evolution of the joints was characterized by optical microscopy (OM) and X-ray diffraction (XRD). Tensile testing was conducted at room temperature and at 550 °C. The results demonstrated that with the exception of some porosity, a good quality joint could be achieved. Martensite α' and acicular α structures were present in the fusion zone (FZ). The amount of martensite α' present with the -0.2 mm beam offset was less than that with the 0.2 mm beam offset. Acicular α and martensite α' transformations occurred in the high temperature heat-affected zone (HT-HAZ) of both the BTi-6431S and TA15 alloys. In the low-temperature heat-affected zone (LT-HAZ), the BTi-6431S and TA15 alloy microstructures exhibited a mixture of secondary α, primary α, and prior β phases. The microhardness values in the FZ followed the order: -0.2 mm> 0 mm> 0.2 mm. Tensile testing at room temperature and at 550 °C resulted in fracture of the TA15 alloy base metal. The fracture morphology exhibited a ductile dimple feature.

  16. A unified 3D model for an interaction mechanism of the plasma arc, weld pool and keyhole in plasma arc welding

    NASA Astrophysics Data System (ADS)

    Jian, Xiaoxia; Wu, ChuanSong; Zhang, Guokai; Chen, Ji

    2015-11-01

    A 3D model is developed to perform numerical investigation on the coupled interaction mechanism of the plasma arc, weld pool and keyhole in plasma arc welding. By considering the traveling of the plasma arc along the welding direction, unified governing equations are solved in the whole domain including the torch, plasma arc, keyhole, weld pool and workpiece, which involves different physical mechanisms in different zones. The local thermodynamic equilibrium-diffusion approximation is used to treat the interface between the plasma arc and weld pool, and the volume-of-fluid method is used to track the evolution of the keyhole wall. The interaction effects between the plasma arc, keyhole and weld pool as well as the heat, mass and pressure transport phenomena in the whole welding domain are quantitatively simulated. It is found that when the torch is moving along the joint line, the axis of the keyhole channel tilts backward, and the envelope of molten metal surrounding the keyhole wall inside the weld pool is unsymmetrical relative to the keyhole channel. The plasma arc welding tests are conducted, and the predicted keyhole dimensions and the fusion zone shape are in agreement with the experimentally measured results.

  17. 3D transient multiphase model for keyhole, vapor plume, and weld pool dynamics in laser welding including the ambient pressure effect

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Chen, Xin; Zhou, Jianxin; Shao, Xinyu; Wang, Chunming

    2015-11-01

    The physical process of deep penetration laser welding involves complex, self-consistent multiphase keyhole, metallic vapor plume, and weld pool dynamics. Currently, efforts are still needed to understand these multiphase dynamics. In this paper, a novel 3D transient multiphase model capable of describing a self-consistent keyhole, metallic vapor plume in the keyhole, and weld pool dynamics in deep penetration fiber laser welding is proposed. Major physical factors of the welding process, such as recoil pressure, surface tension, Marangoni shear stress, Fresnel absorptions mechanisms, heat transfer, and fluid flow in weld pool, keyhole free surface evolutions and solid-liquid-vapor three phase transformations are coupling considered. The effect of ambient pressure in laser welding is rigorously treated using an improved recoil pressure model. The predicated weld bead dimensions, transient keyhole instability, weld pool dynamics, and vapor plume dynamics are compared with experimental and literature results, and good agreements are obtained. The predicted results are investigated by not considering the effects of the ambient pressure. It is found that by not considering the effects of ambient pressure, the average keyhole wall temperature is underestimated about 500 K; besides, the average speed of metallic vapor will be significantly overestimated. The ambient pressure is an essential physical factor for a comprehensive understanding the dynamics of deep penetration laser welding.

  18. [Impact of introduction of O2 on the welding arc of gas pool coupled activating TIG].

    PubMed

    Huang, Yong; Wang, Yan-Lei; Zhang, Zhi-Guo

    2014-05-01

    In the present paper, Boltzmann plot method was applied to analyze the temperature distributions of the are plasma when the gas pool coupled activating TIG welding was at different coupling degrees with the outer gas being O2. Based on this study of temperature distributions, the changing regularities of are voltage and are appearance were studied. The result shows that compared with traditional TIG welding, the introduction of O2 makes the welding arc constricted slightly, the temperature of the are center build up, and the are voltage increase. When argon being the inner gas, oxygen serving as the outer gas instead of argon makes the are constricted more obviously. When the coupling degree increases from 0 to 2, the temperature of the are center and the are voltage both increase slightly. In the gas pool coupled activating TIG welding the are is constricted not obviously, and the reason why the weld penetration is improved dramatically in the welding of stainless steel is not are constriction. PMID:25095400

  19. Plasma diagnostics approach to welding heat source/molten pool interaction

    SciTech Connect

    Key, J.F.; McIlwain, M.E.; Isaacson, L.

    1980-01-01

    Plasma diagnostic techniques show that weld fusion zone profile and loss of metal vapors from the molten pool are strongly dependent on both the intensity and distribution of the heat source. These plasma properties, are functions of cathode vertex angle and thermal conductivity of the shielding gas, especially near the anode.

  20. Surface temperature distribution of GTA weld pools on thin-plate 304 stainless steel

    SciTech Connect

    Zacharia, T.; David, S.A.; Vitek, J.M.; Kraus, H.G.

    1995-11-01

    A transient multidimensional computational model was utilized to study gas tungsten arc (GTA) welding of thin-plate 304 stainless steel (SS). The model eliminates several of the earlier restrictive assumptions including temperature-independent thermal-physical properties. Consequently, all important thermal-physical properties were considered as temperature dependent throughout the range of temperatures experienced by the weld metal. The computational model was used to predict surface temperature distribution of the GTA weld pools in 1.5-mm-thick AISI 304 SS. The welding parameters were chosen so as to correspond with an earlier experimental study that produced high-resolution surface temperature maps. One of the motivations of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate excellent agreement, thereby verifying the model.

  1. Phase-correction algorithm of deformed grating images in the depth measurement of weld pool surface in gas tungsten arc welding

    NASA Astrophysics Data System (ADS)

    Wei, Yiqing; Liu, Nansheng; Hu, Xian; Ai, Xiaopu

    2011-05-01

    The principle and system structure of the depth measurement of weld pool surface in tungsten insert gas (TIG) welding are first introduced in the paper, then the problem of the common phase lines is studied. We analyze the causes and characteristics of the phase lines, and propose a phase correction method based on line ratio. The paper presents the principle and detail processing steps of this phase correction algorithm, and then the effectiveness and processing characteristics of the algorithm are verified by simulation. Finally, the algorithm is applied to phase processing in the depth measurement of the TIG weld pool surface and obtains satisfying results.

  2. Simultaneous vision image sensing of weld pool of pulsed GTAW in multi-orientation in a frame

    NASA Astrophysics Data System (ADS)

    Zhang, Guangjun; Chen, Shanben; Liu, Xiaodong; Wu, Lin

    2001-09-01

    Welding arc light spectrum in the range of 600nm~700nm basically composes of continuous spectrum without metal spectrum and argon spectrum. The radiation strength of this continuous spectrum is low and smooth, which is benefit for reducing process, and the response sensitivity of CCD camera is high at this wavelength range. So, choose a suitable imaging spectrum window, use the continuous spectrum of this window to illuminate the welding pool and use CCD camera to sample the pool image. The reflection of arc light from liquid metal pool surface is specular reflection, the reflection of arc light from the workpiece surface is diffuse reflection, which improves the contrast of the welding pool image. This kind of vision image sensing method takes full advantage of the arc light as a benefit factor, and realizes to acquire the comprehensive information of the pool only from a single sensing source. Based on the above principle, this paper develops a visual image sensing system for weld zone of pulsed GTAW. The system as a part of the control system for weld shape can realize simultaneous image sensing of front topside, back topside and bottom side weld pool in a frame. Both the topside and bottom images concentrate on the same target of the CCD camera through the visual sensing light path system. The composite filter technology with low sampling image current is used to overcome the influence of arc light. The high quality and clear images of weld zones are acquired, which supply plenty information to study the dynamic process of pulsed GTAW. In addition, in order to extract the actual size parameters of weld pool, the image sensing system is calibrated.

  3. Plasma effect on weld pool surface reconstruction by shape-from-polarization analysis

    SciTech Connect

    Coniglio, N.; Mathieu, A.

    2014-03-31

    The polarimetric state of the thermal radiations emitted by the weld metal contains geometric information about the emitting surface. Even though the analysed thermal radiation has a wavelength corresponding to a blind spectral window of the arc plasma, the physical presence of the arc plasma itself interferes with the rays radiated by the weld pool surface before attaining the polarimeter, thus modifying the geometric information transported by the ray. In the present work, the effect of the arc plasma-surrounding zone on the polarimetric state and propagation direction of the radiated ray is analyzed. The interaction with the arc plasma zone induces a drop in ray intensity and a refraction of ray optical path.

  4. Plasma effect on weld pool surface reconstruction by shape-from-polarization analysis

    NASA Astrophysics Data System (ADS)

    Coniglio, N.; Mathieu, A.; Aubreton, O.; Stolz, C.

    2014-03-01

    The polarimetric state of the thermal radiations emitted by the weld metal contains geometric information about the emitting surface. Even though the analysed thermal radiation has a wavelength corresponding to a blind spectral window of the arc plasma, the physical presence of the arc plasma itself interferes with the rays radiated by the weld pool surface before attaining the polarimeter, thus modifying the geometric information transported by the ray. In the present work, the effect of the arc plasma-surrounding zone on the polarimetric state and propagation direction of the radiated ray is analyzed. The interaction with the arc plasma zone induces a drop in ray intensity and a refraction of ray optical path.

  5. Ultra-fast in-situ X-ray studies of evolving columnar dendrites in solidifying steel weld pools

    NASA Astrophysics Data System (ADS)

    Mirihanage, W. U.; Di Michiel, M.; Mathiesen, R. H.

    2015-06-01

    High-brilliance polychromatic synchrotron radiation has been used to conduct in-situ studies of the solidification microstructure evolution during simulated welding. The welding simulations were realized by rapidly fusing ∼ 5 mm spot in Fe-Cr-Ni steel. During the solid- liquid-solid phase transformations, a section of the weld pool was placed in an incident 50-150 keV polychromatic synchrotron X-ray beam, in a near-horizontal position at a very low inclination angle. Multiple high-resolution 2D detectors with very high frame rates were utilized to capture time resolved X-ray diffraction data from suitably oriented solid dendrites evolving in the weld pool. Comprehensive analysis of the diffraction data revealed individual and overall dendritic growth characteristics and relevant melt and solid flow dynamics during weld pool solidification, which was completed within 1.5 s. Columnar dendrite tip velocities were estimated from the experimental data and during early stages of solidification were exceeded 4 mm/s. The most remarkable observation revealed through the time-resolved reciprocal space observations are correlated to significant tilting of columnar type dendrites at their root during solidification, presumably caused by convective currents in the weld pool. When the columnar dendrite tilting are transformed to respective metric linear tilting velocities at the dendrite tip; tilting velocities are found to be in the same order of magnitude as the columnar tip growth velocities, suggesting a highly transient nature of growth conditions.

  6. Effects of shielding gas composition on arc profile and molten pool dynamics in gas metal arc welding of steels

    NASA Astrophysics Data System (ADS)

    Wang, L. L.; Lu, F. G.; Wang, H. P.; Murphy, A. B.; Tang, X. H.

    2014-11-01

    In gas metal arc welding, gases of different compositions are used to produce an arc plasma, which heats and melts the workpiece. They also protect the workpiece from the influence of the air during the welding process. This paper models gas metal arc welding (GMAW) processes using an in-house simulation code. It investigates the effects of the gas composition on the temperature distribution in the arc and on the molten pool dynamics in gas metal arc welding of steels. Pure argon, pure CO2 and different mixtures of argon and CO2 are considered in the study. The model is validated by comparing the calculated weld profiles with physical weld measurements. The numerical calculations reveal that gas composition greatly affects the arc temperature profile, heat transfer to the workpiece, and consequently the weld dimension. As the CO2 content in the shielding gas increases, a more constricted arc plasma with higher energy density is generated as a result of the increased current density in the arc centre and increased Lorentz force. The calculation also shows that the heat transferred from the arc to the workpiece increases with increasing CO2 content, resulting in a wider and deeper weld pool and decreased reinforcement height.

  7. Gravitational effects on the development of weld-pool and solidification microstructures

    SciTech Connect

    Boatner, L.A.; David, S.A.; Workman, G.

    1994-09-01

    This research effort has as its objective the development of a quantitative understanding of the effects of both low- and high-g environments on the solidification microstructures and morphologies that are produced in alloy single crystals during a variety of melting and solidification processes. The overall goal of the effort is to delineate the nature of the roles played by natural convection, surface-tension-driven convection, and mass transport effects due to interactions associated with various heating methods that are used to form melt pools in practical, commercially important alloy systems. The experimental and theoretical investigations comprising this effort encompass the study of configurations in which stationary heat sources are employed as well as melt pools formed by moving heat sources like those frequently used in fusion-welding processes.

  8. Calorimeters for pulsed lasers: calibration.

    PubMed

    Thacher, P D

    1976-07-01

    A calibration technique is developed and tested in which a calorimeter used for single-shot laser pulse energy measurements is calibrated with reference to a cw power standard using a chopped cw laser beam. A pulsed laser is required only to obtain the relative time response of the calorimeter to a pulse. With precautions as to beam alignment and wavelength, the principal error of the technique is that of the cw standard. Calibration of two thermopiles with cone receivers showed -2.5% and -3.5% agreement with previous calibrations made by the National Bureau of Standards. PMID:20165270

  9. Towards and FVE-FAC Method for Determining Thermocapillary Effects on Weld Pool Shape

    NASA Technical Reports Server (NTRS)

    Canright, David; Henson, Van Emden

    1996-01-01

    Several practical materials processes, e.g., welding, float-zone purification, and Czochralski crystal growth, involve a pool of molten metal with a free surface, with strong temperature gradients along the surface. In some cases, the resulting thermocapillary flow is vigorous enough to convect heat toward the edges of the pool, increasing the driving force in a sort of positive feedback. In this work we examine this mechanism and its effect on the solid-liquid interface through a model problem: a half space of pure substance with concentrated axisymmetric surface heating, where surface tension is strong enough to keep the liquid free surface flat. The numerical method proposed for this problem utilizes a finite volume element (FVE) discretization in cylindrical coordinates. Because of the axisymmetric nature of the model problem, the control volumes used are torroidal prisms, formed by taking a polygonal cross-section in the (r, z) plane and sweeping it completely around the z-axis. Conservation of energy (in the solid), and conservation of energy, momentum, and mass (in the liquid) are enforced globally by integrating these quantities and enforcing conservation over each control volume. Judicious application of the Divergence Theorem and Stokes' Theorem, combined with a Crank-Nicolson time-stepping scheme leads to an implicit algebraic system to be solved at each time step. It is known that near the boundary of the pool, that is, near the solid-liquid interface, the full conduction-convection solution will require extremely fine length scales to resolve the physical behavior of the system. Furthermore, this boundary moves as a function of time. Accordingly, we develop the foundation of an adaptive refinement scheme based on the principles of Fast Adaptive Composite Grid methods (FAC). Implementation of the method and numerical results will appear in a later report.

  10. Analysis of Picosecond Pulsed Laser Melted Graphite

    DOE R&D Accomplishments Database

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

    1986-12-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

  11. Adaptive Neuro-Fuzzy Inference System (ANFIS)-Based Models for Predicting the Weld Bead Width and Depth of Penetration from the Infrared Thermal Image of the Weld Pool

    NASA Astrophysics Data System (ADS)

    Subashini, L.; Vasudevan, M.

    2012-02-01

    Type 316 LN stainless steel is the major structural material used in the construction of nuclear reactors. Activated flux tungsten inert gas (A-TIG) welding has been developed to increase the depth of penetration because the depth of penetration achievable in single-pass TIG welding is limited. Real-time monitoring and control of weld processes is gaining importance because of the requirement of remoter welding process technologies. Hence, it is essential to develop computational methodologies based on an adaptive neuro fuzzy inference system (ANFIS) or artificial neural network (ANN) for predicting and controlling the depth of penetration and weld bead width during A-TIG welding of type 316 LN stainless steel. In the current work, A-TIG welding experiments have been carried out on 6-mm-thick plates of 316 LN stainless steel by varying the welding current. During welding, infrared (IR) thermal images of the weld pool have been acquired in real time, and the features have been extracted from the IR thermal images of the weld pool. The welding current values, along with the extracted features such as length, width of the hot spot, thermal area determined from the Gaussian fit, and thermal bead width computed from the first derivative curve were used as inputs, whereas the measured depth of penetration and weld bead width were used as output of the respective models. Accurate ANFIS models have been developed for predicting the depth of penetration and the weld bead width during TIG welding of 6-mm-thick 316 LN stainless steel plates. A good correlation between the measured and predicted values of weld bead width and depth of penetration were observed in the developed models. The performance of the ANFIS models are compared with that of the ANN models.

  12. Welding.

    ERIC Educational Resources Information Center

    South Carolina State Dept. of Education, Columbia. Office of Vocational Education.

    This curriculum guide is designed for use by South Carolina vocational education teachers as a continuing set of lesson plans for a two-year course on welding. Covered in the individual sections of the guide are the following topics: an orientation to welding, oxyacetylene welding, advanced oxyacetylene welding, shielded metal arc welding, TIG…

  13. Smoothed particle hydrodynamics modelling of the fluid flow and heat transfer in the weld pool during laser spot welding

    NASA Astrophysics Data System (ADS)

    Tong, Mingming; Browne, David J.

    2012-01-01

    Smoothed particle hydrodynamics is employed, for the first time, to develop a numerical model for the melting and fluid flow during laser welding process. In this meshlessLagrangian method the gas-melt two phase flow, heat transfer, surface tension, and melting of solid parent material are considered. This model was used to study the evolution of temperature field and fluid flow in the case study of laser spot welding in 2D. The simulation results show a strong influence of the melting process on the flow of liquid metal and a clear influence of the Marangoni flow on the heat transfer is also found.

  14. Feedback control of pulsed laser deposition processes

    NASA Astrophysics Data System (ADS)

    Laube, S. J. P.; Stark, E. F.

    1993-10-01

    Implementation of closed loop feedback on PLD (pulsed laser deposition) requires actuators and sensors. Improvements in quality and reproducibility of material depositions are achieved by actuating the process towards desired operating regions. Empirical relationships are experimentally determined for describing the complex dynamical interactions of laser parameters. Feedback control based on this description can then be implemented to reduce process disorder.

  15. Mirrorlike pulsed laser deposited tungsten thin film

    SciTech Connect

    Mostako, A. T. T.; Khare, Alika; Rao, C. V. S.

    2011-01-15

    Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10{sup -5} Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness {approx}782 nm.

  16. Mirrorlike pulsed laser deposited tungsten thin film.

    PubMed

    Mostako, A T T; Rao, C V S; Khare, Alika

    2011-01-01

    Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10(-5) Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness ∼782 nm. PMID:21280810

  17. Pulsed Laser Ablation of Soft Biological Tissues

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Venugopalan, Vasan

    In this chapter we focus on the key elements that form our current understanding of the mechanisms of pulsed laser ablation of soft biological tissues. We present a conceptual framework providing mechanistic links between various ablation applications and the underlying thermodynamic and phase change processes [1]. We define pulsed laser ablation as the use of laser pulses with duration of ~1 ms or less for the incision or removal of tissue regardless of the photophysical or photochemical processes involved. However, we will confine this presentation to pulsed ablation performed on a tissue level that does not involve laser-induced plasma formation. Ablation processes within transparent tissues or cells resulting from non-linear absorption have been considered in reviews by Vogel and Venugopalan [1] and by Vogel and co-workers [2].

  18. Pulsed laser damage to optical fibers

    SciTech Connect

    Allison, S.W.; Gillies, G.T.; Magnuson, D.W.; Pagano, T.S.

    1985-10-01

    This paper describes some observations of pulsed laser damage to optical fibers with emphasis on a damage mode characterized as a linear fracture along the outer core of a fiber. Damage threshold data are presented which illustrate the effects of the focusing lens, end-surface preparation, and type of fiber. An explanation based on fiber-beam misalignment is given and is illustrated by a simple experiment and ray trace.

  19. Ultrashort pulsed laser technology development program

    NASA Astrophysics Data System (ADS)

    Manke, Gerald C.

    2014-10-01

    The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been published to promote and fund research that encompasses every critical component of a standard USPL system and enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize published topics and funded programs.

  20. Compact pulsed laser having improved heat conductance

    NASA Technical Reports Server (NTRS)

    Yang, L. C. (Inventor)

    1977-01-01

    A highly efficient, compact pulsed laser having high energy to weight and volume ratios is provided. The laser utilizes a cavity reflector that operates as a heat sink and is essentially characterized by having a high heat conductivity, by being a good electrical insulator and by being substantially immune to the deleterious effects of ultra-violet radiation. Manual portability is accomplished by eliminating entirely any need for a conventional circulating fluid cooling system.

  1. Welding and Lung Cancer in a Pooled Analysis of Case-Control Studies

    PubMed Central

    Kendzia, Benjamin; Behrens, Thomas; Jöckel, Karl-Heinz; Siemiatycki, Jack; Kromhout, Hans; Vermeulen, Roel; Peters, Susan; Van Gelder, Rainer; Olsson, Ann; Brüske, Irene; Wichmann, H.-Erich; Stücker, Isabelle; Guida, Florence; Tardón, Adonina; Merletti, Franco; Mirabelli, Dario; Richiardi, Lorenzo; Pohlabeln, Hermann; Ahrens, Wolfgang; Landi, Maria Teresa; Caporaso, Neil; Consonni, Dario; Zaridze, David; Szeszenia-Dabrowska, Neonila; Lissowska, Jolanta; Gustavsson, Per; Marcus, Michael; Fabianova, Eleonora; ‘t Mannetje, Andrea; Pearce, Neil; Tse, Lap Ah; Yu, Ignatius Tak-sun; Rudnai, Peter; Bencko, Vladimir; Janout, Vladimir; Mates, Dana; Foretova, Lenka; Forastiere, Francesco; McLaughlin, John; Demers, Paul; Bueno-de-Mesquita, Bas; Boffetta, Paolo; Schüz, Joachim; Straif, Kurt; Pesch, Beate; Brüning, Thomas

    2013-01-01

    Several epidemiologic studies have indicated an increased risk of lung cancer among welders. We used the SYNERGY project database to assess welding as a risk factor for developing lung cancer. The database includes data on 15,483 male lung cancer cases and 18,388 male controls from 16 studies in Europe, Canada, China, and New Zealand conducted between 1985 and 2010. Odds ratios and 95% confidence intervals between regular or occasional welding and lung cancer were estimated, with adjustment for smoking, age, study center, and employment in other occupations associated with lung cancer risk. Overall, 568 cases and 427 controls had ever worked as welders and had an odds ratio of developing lung cancer of 1.44 (95% confidence interval: 1.25, 1.67) with the odds ratio increasing for longer duration of welding. In never and light smokers, the odds ratio was 1.96 (95% confidence interval: 1.37, 2.79). The odds ratios were somewhat higher for squamous and small cell lung cancers than for adenocarcinoma. Another 1,994 cases and 1,930 controls had ever worked in occupations with occasional welding. Work in any of these occupations was associated with some elevation of risk, though not as much as observed in regular welders. Our findings lend further support to the hypothesis that welding is associated with an increased risk of lung cancer. PMID:24052544

  2. Welding.

    ERIC Educational Resources Information Center

    Lehigh County Area Vocational-Technical School, Schnecksville, PA.

    This curriculum guide provides materials for a 12-unit secondary course in welding. Purpose stated for the flexible entry and exit course is to help students master manipulative skills to develop successful welding techniques and to gain an understanding of the specialized tools and equipment used in the welding field. Units cover oxyacetylene…

  3. Robotic Vision for Welding

    NASA Technical Reports Server (NTRS)

    Richardson, R. W.

    1986-01-01

    Vision system for robotic welder looks at weld along axis of welding electrode. Gives robot view of most of weld area, including yet-unwelded joint, weld pool, and completed weld bead. Protected within welding-torch body, lens and fiber bundle give robot closeup view of weld in progress. Relayed to video camera on robot manipulator frame, weld image provides data for automatic control of robot motion and welding parameters.

  4. Pulsed laser deposition: Prospects for commercial deposition of epitaxial films

    SciTech Connect

    Muenchausen, R.E.

    1999-03-01

    Pulsed laser deposition (PLD) is a physical vapor deposition (PVD) technique for the deposition of thin films. The vapor source is induced by the flash evaporation that occurs when a laser pulse of sufficient intensity (about 100 MW/cm{sup 2}) is absorbed by a target. In this paper the author briefly defines pulsed laser deposition, current applications, research directed at gaining a better understanding of the pulsed laser deposition process, and suggests some future directions to enable commercial applications.

  5. Nanosecond pulsed laser blackening of copper

    NASA Astrophysics Data System (ADS)

    Tang, Guang; Hourd, Andrew C.; Abdolvand, Amin

    2012-12-01

    Nanosecond (12 ns) pulsed laser processing of copper at 532 nm resulted in the formation of homogenously distributed, highly organized microstructures. This led to the fabrication of large area black copper substrates with absorbance of over 97% in the spectral range from 250 nm to 750 nm, and a broadband absorbance of over 80% between 750 nm and 2500 nm. Optical and chemical analyses of the fabricated black metal are presented and discussed. The employed laser is an industrially adaptable source and the presented technique for fabrication of black copper could find applications in broadband thermal radiation sources, solar energy absorbers, irradiative heat transfer devices, and thermophotovoltaics.

  6. Quantifying pulsed laser induced damage to graphene

    SciTech Connect

    Currie, Marc; Caldwell, Joshua D.; Bezares, Francisco J.; Robinson, Jeremy; Anderson, Travis; Chun, Hayden; Tadjer, Marko

    2011-11-21

    As an emerging optical material, graphene's ultrafast dynamics are often probed using pulsed lasers yet the region in which optical damage takes place is largely uncharted. Here, femtosecond laser pulses induced localized damage in single-layer graphene on sapphire. Raman spatial mapping, SEM, and AFM microscopy quantified the damage. The resulting size of the damaged area has a linear correlation with the optical fluence. These results demonstrate local modification of sp{sup 2}-carbon bonding structures with optical pulse fluences as low as 14 mJ/cm{sup 2}, an order-of-magnitude lower than measured and theoretical ablation thresholds.

  7. Thomson scattering in short pulse laser experiments

    SciTech Connect

    Hill, E. G.; Rose, S. J.

    2012-08-15

    Thomson scattering is well used as a diagnostic in many areas of high energy density physics. In this paper, we quantitatively demonstrate the practicality of using Thomson scattering as a diagnostic of short-pulse laser-plasma experiments in the regime, where the plasmas probed are at solid density and have temperatures of many hundreds of eV using a backlighter produced with an optical laser. This method allows a diagnosis both spatially and temporally of the density and temperature distributions in high energy density laser-plasma interactions which is independent from, and would act as a useful complement to, the existing spectroscopic methods.

  8. Nonequilibrium Interlayer Transport in Pulsed Laser Deposition

    SciTech Connect

    Tischler, Jonathan Zachary; Eres, Gyula; Larson, Ben C; Rouleau, Christopher M; Zschack, P.; Lowndes, Douglas H

    2006-01-01

    We use time-resolved surface x-ray diffraction measurements with microsecond range resolution to study the growth kinetics of pulsed laser deposited SrTiO3. Time-dependent surface coverages corresponding to single laser shots were determined directly from crystal truncation rod intensity transients. Analysis of surface coverage evolution shows that extremely fast nonequilibrium interlayer transport, which occurs concurrently with the arrival of the laser plume, dominates the deposition process. A much smaller fraction of material, which is governed by the dwell time between successive laser shots, is transferred by slow, thermally driven interlayer transport processes.

  9. Pulsed laser deposition of zeolitic membranes

    SciTech Connect

    Peachey, N.M.; Dye, R.C.; Ries, P.D.

    1995-02-01

    The pulsed laser deposition of zeolites to form zeolitic thin films is described. Films were grown using both mordenite and faujasite targets and were deposited on various substrates. The optimal films were obtained when the target and substrate were separated by 5 cm. These films are comprised of small crystallites embedded in an amorphous matrix. Transmission electron microscopy reveals that the amorphous material is largely porous and that the pores appear to be close to the same size as the parent zeolite. Zeolotic thin films are of interest for sensor, gas separation, and catalytic applications.

  10. Chemically-Assisted Pulsed Laser-Ramjet

    SciTech Connect

    Horisawa, Hideyuki; Kaneko, Tomoki; Tamada, Kazunobu

    2010-10-13

    A preliminary study of a chemically-assisted pulsed laser-ramjet was conducted, in which chemical propellant such as a gaseous hydrogen/air mixture was utilized and detonated with a focused laser beam in order to obtain a higher impulse compared to the case only using lasers. CFD analysis of internal conical-nozzle flows and experimental measurements including impulse measurement were conducted to evaluate effects of chemical reaction on thrust performance improvement. From the results, a significant improvement in the thrust performances was confirmed with addition of a small amount of hydrogen to propellant air, or in chemically-augmented operation.

  11. Pulsed Laser Illumination of Photovoltaic Cells

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Lowe, Roland; Jenkins, Philip; Landis, Geoffrey A.

    1994-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. The induction FEL and the radio-frequency (RF) FEL both produce pulsed rather than continuous output. In this work, we investigate cell response to pulsed laser light which simulates the RF FEL format, producing 50 ps pulses at a frequency of 78 MHz. A variety of Si, GaAs, CaSb and CdInSe2 (CIS) solar cells are tested at average incident powers between 4 mW/sq cm and 425 mW/sq cm. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced by using a pulsed laser source compared to constant illumination at the same wavelength. Because the pulse separation is less than or approximately equal to the minority carrier lifetime, the illumination conditions are effectively those of a continuous wave laser. The time dependence of the voltage and current response of the cells are also measured using a sampling oscilloscope equipped with a high frequency voltage probe and current transformer. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments shows that the RF FEL pulse format yields much more efficient photovoltaic conversion of light than does an induction FEL pulse format.

  12. Modeling of pulsed lasers for remote sensing

    NASA Astrophysics Data System (ADS)

    Walsh, Brian M.; Barnes, Norman P.; Petros, Mulugeta; Yu, Jirong; Singh, Upendra N.

    2005-01-01

    Pulsed lasers are useful for remote sensing of wind and greenhouse gases to better understand the atmosphere and its impact on weather patterns and the environment. It is not always practical to develop and optimize new laser systems empirically due to the time and expense associated with such endeavors. A practical option is to use a laser model to predict various performance parameters and compare these with the needs required for a particular remote sensing application. This approach can be very useful in determining the efficacy of potential laser systems, saving both time and money before proceeding with the actual construction of a laser device. As a pedagogical example, the modeling of diode pumped Tm:Ho:YLF and Tm:Ho:LuLF lasers are examined. Tm:Ho lasers operating around 2.0 μm have been used for wind measurements such as clear air turbulence and wake vortices. The model predictions for the laser systems examined here are compared to the actual laser performance, validating the usefulness of the modeling approach. While Tm:Ho fluoride lasers are used as a pedagogical example, the model is applicable to any lanthanide series pulsed laser system. This provides a useful tool for investigating potential laser systems that meet the requirements desired for a variety of remote sensing applications.

  13. Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers

    PubMed Central

    2016-01-01

    tool for the controlled welding of plasmonic gold nanostructures by electromagnetic field enhancement at the hot spots of assembled Au NPs. The combination of such nanostructures with pulse lasers promises significant chemical and biochemical advances, including the structural determination of organic reaction intermediates, the investigation of phase transitions in inorganic nanomaterials at mild reaction conditions, or the efficient photothermal destruction of cancer cells avoiding damage of surrounding tissue. PMID:27035211

  14. Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers.

    PubMed

    González-Rubio, Guillermo; Guerrero-Martínez, Andrés; Liz-Marzán, Luis M

    2016-04-19

    controlled welding of plasmonic gold nanostructures by electromagnetic field enhancement at the hot spots of assembled Au NPs. The combination of such nanostructures with pulse lasers promises significant chemical and biochemical advances, including the structural determination of organic reaction intermediates, the investigation of phase transitions in inorganic nanomaterials at mild reaction conditions, or the efficient photothermal destruction of cancer cells avoiding damage of surrounding tissue. PMID:27035211

  15. Pulsed laser deposition: the road to hybrid nanocomposites coatings and novel pulsed laser adaptive technique.

    PubMed

    Serbezov, Valery

    2013-01-01

    The applications of Pulsed Laser Deposition (PLD) for producing nanoparticles, nanostructures and nanocomposites coatings based on recently developed laser ablating techniques and their convergence are being reviewed. The problems of in situ synthesis of hybrid inorganic-organic nanocomposites coatings by these techniques are being discussed. The novel modification of PLD called Pulsed Laser Adaptive Deposition (PLAD) technique is presented. The in situ synthesized inorganic/organic nanocomposites coatings from Magnesium (Mg) alloy/Rhodamine B and Mg alloy/ Desoximetasone by PLAD are described. The trends, applications and future development of discussed patented methods based on the laser ablating technologies for producing hybrid nanocomposite coatings have also been discussed in this review. PMID:22747717

  16. Pulsed laser illumination of photovoltaic cells

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1994-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. Both the radio-frequency (RF) and induction FEL provide FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL pulse format.

  17. Pulsed laser illumination of photovoltaic cells

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

  18. Heat accumulation during pulsed laser materials processing.

    PubMed

    Weber, Rudolf; Graf, Thomas; Berger, Peter; Onuseit, Volkher; Wiedenmann, Margit; Freitag, Christian; Feuer, Anne

    2014-05-01

    Laser materials processing with ultra-short pulses allows very precise and high quality results with a minimum extent of the thermally affected zone. However, with increasing average laser power and repetition rates the so-called heat accumulation effect becomes a considerable issue. The following discussion presents a comprehensive analytical treatment of multi-pulse processing and reveals the basic mechanisms of heat accumulation and its consequence for the resulting processing quality. The theoretical findings can explain the experimental results achieved when drilling microholes in CrNi-steel and for cutting of CFRP. As a consequence of the presented considerations, an estimate for the maximum applicable average power for ultra-shorts pulsed laser materials processing for a given pulse repetition rate is derived. PMID:24921828

  19. 25 years of pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

    It is our pleasure to introduce this special issue appearing on the occasion of the 25th anniversary of pulsed laser deposition (PLD), which is today one of the most versatile growth techniques for oxide thin films and nanostructures. Ever since its invention, PLD has revolutionized the research on advanced functional oxides due to its ability to yield high-quality thin films, multilayers and heterostructures of a variety of multi-element material systems with rather simple technical means. We appreciate that the use of lasers to deposit films via ablation (now termed PLD) has been known since the 1960s after the invention of the first ruby laser. However, in the first two decades, PLD was something of a 'sleeping beauty' with only a few publications per year, as shown below. This state of hibernation ended abruptly with the advent of high T c superconductor research when scientists needed to grow high-quality thin films of multi-component high T c oxide systems. When most of the conventional growth techniques failed, the invention of PLD by T (Venky) Venkatesan clearly demonstrated that the newly discovered high-T c superconductor, YBa2Cu3O7-δ , could be stoichiometrically deposited as a high-quality nm-thin film with PLD [1]. As a remarkable highlight of this special issue, Venkatesan gives us his very personal reminiscence on these particularly innovative years of PLD beginning in 1986 [2]. After Venky's first paper [1], the importance of this invention was realized worldwide and the number of publications on PLD increased exponentially, as shown in figure 1. Figure 1. Figure 1. Published items per year with title or topic PLD. Data from Thomson Reuters Web of Knowledge in September 2013. After publication of Venky's famous paper in 1987 [1], the story of PLD's success began with a sudden jump in the number of publications, about 25 years ago. A first PLD textbook covering its basic understanding was soon published, in 1994, by Chrisey and Hubler [3]. Within a

  20. Analysis of melt ejection during long pulsed laser drilling

    NASA Astrophysics Data System (ADS)

    Ting-Zhong, Zhang; Zhi-Chao, Jia; Hai-Chao, Cui; De-Hua, Zhu; Xiao-Wu, Ni; Jian, Lu

    2016-05-01

    In pulsed laser drilling, melt ejection greatly influences the keyhole shape and its quality as well, but its mechanism has not been well understood. In this paper, numerical simulation and experimental investigations based on 304 stainless steel and aluminum targets are performed to study the effects of material parameters on melt ejection. The numerical method is employed to predict the temperatures, velocity fields in the solid, liquid, and vapour front, and melt pool dynamics of targets as well. The experimental methods include the shadow-graphic technique, weight method, and optical microscope imaging, which are applied to real-time observations of melt ejection phenomena, measurements of collected melt and changes of target mass, observations of surface morphology and the cross-section of the keyhole, respectively. Numerical and experimental results show that the metallic material with high thermal diffusivity like aluminum is prone to have a thick liquid zone and a large quantity of melt ejection. Additionally, to the best of our knowledge, the liquid zone is used to illustrate the relations between melt ejection and material thermal diffusivity for the first time. The research result in this paper is useful for manufacturing optimization and quality control in laser-material interaction. Project supported by the Natural Science Foundation of Jiangsu Province, China (Grant No. KYLX_0341) and the National Natural Science Foundation of China (Grant No. 61405147).

  1. Pulsed laser deposition of pepsin thin films

    NASA Astrophysics Data System (ADS)

    Kecskeméti, G.; Kresz, N.; Smausz, T.; Hopp, B.; Nógrádi, A.

    2005-07-01

    Pulsed laser deposition (PLD) of organic and biological thin films has been extensively studied due to its importance in medical applications among others. Our investigations and results on PLD of a digestion catalyzing enzyme, pepsin, are presented. Targets pressed from pepsin powder were ablated with pulses of an ArF excimer laser ( λ = 193 nm, FWHM = 30 ns), the applied fluence was varied between 0.24 and 5.1 J/cm 2. The pressure in the PLD chamber was 2.7 × 10 -3 Pa. The thin layers were deposited onto glass and KBr substrates. Our IR spectroscopic measurements proved that the chemical composition of deposited thin films is similar to that of the target material deposited at 0.5 and 1.3 J/cm 2. The protein digesting capacity of the transferred pepsin was tested by adapting a modified "protein cube" method. Dissolution of the ovalbumin sections proved that the deposited layers consisted of catalytically active pepsin.

  2. Pulsed laser fluorometry for environmental monitoring

    NASA Astrophysics Data System (ADS)

    Saunders, G. C.; Martin, J. C.; Jett, J. H.; Wilder, M. E.; Martinez, A.; Bentley, B. F.; Lopez, J.; Hutson, L.

    A compact pulsed laser fluorometer has been incorporated into a continuous flow system developed to detect acetylcholinesterase (AChE) inhibitors and/or primary amine compounds in air and water. A pulsed nitrogen laser pumped dye laser excites fluorescent reactants which flow continuously through a quartz flow cell. Data are collected, analyzed, and displayed using a Macintosh II personal computer. For detection of cholinesterase inhibitors the fluorogenic substrate N methylindoxyl acetate is used to monitor the activity of immobilized enzyme. Presence of inhibitors results in a decrease of steady state fluorescence. Detection of compounds containing primary amines is based on their reaction with fluorescamine to rapidly produce intensely fluorescent products. Compounds of interest to our research were amino acids, peptides, and proteins. An increase in steady state fluorescence could be cause to evaluate the reasons for the change. The detection limit of the protein, bovine serum albumin (BSA) in water, is 10 ppT. Nebulized BSA concentrated by the LANL air sampler can be detected at sub ppT original air concentration.

  3. Pulsed laser fluorometry for environmental monitoring

    SciTech Connect

    Saunders, G. C.; Martin, J. C.; Jett, J. H.; Wilder, M. E.; Martinez, A.; Bentley, B. F.; Lopez, J.; Hutson, L.

    1990-01-01

    A compact pulsed laser fluorometer has been incorporated into a continuous flow system developed to detect acetylcholinesterase (AChE) inhibitors and/or primary amine compounds in air and water. A pulsed nitrogen laser pumped dye laser excites fluorescent reactants which flow continuously through a quartz flow cell. Data are collected, analyzed, and displayed using a Macintosh II personal computer. For detection of cholinesterase inhibitors the fluorogenic substrate N methylindoxyl acetate is used to monitor the activity of immobilized enzyme. Presence of inhibitors results in a decrease of steady state fluorescence. Detection of compounds containing primary amines is based on their reaction with fluorescamine to rapidly produce intensely fluorescent products. Compounds of interest to our research were amino acids, peptides, and proteins. An increase in steady state fluorescence could be cause to evaluate the reasons for the change. The detection limit of the protein, bovine serum albumin (BSA) in water is 10 ppT. Nebulized BSA concentrated by the LANL air sampler can be detected at sub ppT original air concentration. 16 refs., 14 figs., 3 tabs.

  4. Hemocompatible, pulsed laser deposited coatings on polymers.

    PubMed

    Lackner, Juergen M; Waldhauser, Wolfgang; Major, Roman; Major, Boguslaw; Bruckert, Franz

    2010-02-01

    State-of-the-art non-thrombogenic blood contacting surfaces are based on heparin and struggle with the problem of bleeding. However, appropriate blood flow characteristics are essential for clinical application. Thus, there is increasing demand to develop new coating materials for improved human body acceptance. Materials deposited by vacuum coating techniques would be an excellent alternative if the coating temperatures can be kept low because of the applied substrate materials of low temperature resistance (polymers). Most of the recently used plasma-based deposition techniques cannot fulfill this demand. However, adequate film structure and high adhesion can be reached by the pulsed laser deposition at room temperature, which was developed to an industrial-scaled process at Laser Center Leoben. Here, this process is described in detail and the resulting structural film properties are shown for titanium, titanium nitride, titanium carbonitride, and diamond-like carbon on polyurethane, titanium and silicon substrates. Additionally, we present the biological response of blood cells and the kinetic mechanism of eukaryote cell attachment. In conclusion, high biological acceptance and distinct differences for the critical delamination shear stress were found for the coatings, indicating higher adhesion at higher carbon contents. PMID:20128746

  5. Short-pulse laser interactions with disordered materials and liquids

    SciTech Connect

    Phinney, L.M.; Goldman, C.H.; Longtin, J.P.; Tien, C.L.

    1995-12-31

    High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regime in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.

  6. Welding.

    ERIC Educational Resources Information Center

    Baldwin, Harold; Whitney, Gregory

    This curriculum guide is intended to assist vocational instructors in preparing students for entry-level employment as welders and preparing them for advanced training in the workplace. The package contains an overview of new and emerging welding technologies, a competency/skill and task list, an instructor's guide, and an annotated bibliography.…

  7. Welding.

    ERIC Educational Resources Information Center

    Cowan, Earl; And Others

    The curriculum guide for welding instruction contains 16 units presented in six sections. Each unit is divided into the following areas, each of which is color coded: terminal objectives, specific objectives, suggested activities, and instructional materials; information sheet; transparency masters; assignment sheet; test; and test answers. The…

  8. A new pulsed laser deposition technique: scanning multi-component pulsed laser deposition method.

    PubMed

    Fischer, D; de la Fuente, G F; Jansen, M

    2012-04-01

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C. PMID:22559543

  9. A new pulsed laser deposition technique: Scanning multi-component pulsed laser deposition method

    SciTech Connect

    Fischer, D.; Jansen, M.; Fuente, G. F. de la

    2012-04-15

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 deg. C.

  10. Alloying elemental change of SS-316 and Al-5754 during laser welding using real time laser induced breakdown spectroscopy (LIBS) accompanied by EDX and PIXE microanalysis

    NASA Astrophysics Data System (ADS)

    Jandaghi, M.; Parvin, P.; Torkamany, M. J.; Sabbaghzadeh, J.

    Experimental studies of pulsed laser welding of stainless steel 316 in keyhole mode was done to examine a vaporization model based on the kinetic theory of gases and the thermodynamic laws. A long pulsed Nd:YAG laser with variable duration of 1-12 ms and 9-17 Gw/cm2 was employed. The undesirable loss of volatile elements affects on the weld metal compositions and the alloy properties. The model predicts that the loss of alloying elements strongly takes place at higher peak powers and longer pulse durations. On the other hand, the model shows the rapid migration of Mn and Cr based on the pressure and concentration gradients from the molten pool. Accordingly, the concentrations of iron, chromium, nickel and manganese were determined in the weld pool by means of the energy dispersive x-ray analysis (EDX) and proton induced X ray characteristics (PIXE) microanalysis. The change of weld metal composition of aluminium alloy 5754 in keyhole mode laser welding, was investigated using the model and was supported by the successive measurements. The model predicts that the concentration of magnesium in the weld metal decreases, while the aluminium concentration increases. Moreover, the real time concentrations of aluminium and magnesium elements in the weld metal were determined by laser induced breakdown spectroscopy (LIBS) at different conditions. We conclude that variation of the Al to Mg concentration ratio is negligible with various laser power densities while it is strongly correlated to the pulse duration.

  11. Pulsed Laser Deposition of Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Brodoceanu, D.; Scarisoreanu, N. D.; Filipescu, M. (Morar); Epurescu, G. N.; Matei, D. G.; Verardi, P.; Craciun, F.; Dinescu, M.

    2004-10-01

    Pulsed Laser Deposition (PLD) emerged as an attractive technique for growth of thin films with different properties as metals, semiconductors, ferroelectrics, biocompatibles, polymers, etc., due to its important advantages: (i) the stoichiometric transfer of a complex composition from target to film and film crystallization at lower substrate temperature respect to other techniques (due to the high energy of species in the laser plasma); (ii) single step process, synthesis and deposition; (iii) creation in plasma of species impossible to be obtained by other processes; (iv) possibility of "in situ" heterostructure deposition using a multi-target system, etc. Simple or complex oxides are between the materials widely studied for their applications. PMN is the most known relaxor ferroelectric material: it exhibits a high dielectric constant value around the (diffuse) maximum phase transition temperature, of more than 35 000 in bulk form. Other oxides as lead zirconate titanate, Pb(ZrxTi1-x)O3 simple or La doped exhibit exceptional properties as large remanent polarization, high dielectric permittivity, high piezoelectric coefficient. SrBi2Ta2O9 (SBT) is characterized by a high "fatigue resistance" (constant remanent polarization until 1012 switching cycles), low imprint, and low leakage current. The physical properties of zirconium oxide (or zirconia) -- high strength, stability at high temperatures -- make it useful for applications involving gas sensors, corrosion or heat resistant mechanical parts, high refractive index optical coatings. Of particular interest is its use as an alternative gate dielectric in metal-oxide-semiconductor (MOS) devices or capacitor in dynamic random access memory (DRAM) chips. All these oxides have been deposited by laser ablation in oxygen reactive atmosphere and some of their properties will be presented in this paper.

  12. 25 years of pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

    It is our pleasure to introduce this special issue appearing on the occasion of the 25th anniversary of pulsed laser deposition (PLD), which is today one of the most versatile growth techniques for oxide thin films and nanostructures. Ever since its invention, PLD has revolutionized the research on advanced functional oxides due to its ability to yield high-quality thin films, multilayers and heterostructures of a variety of multi-element material systems with rather simple technical means. We appreciate that the use of lasers to deposit films via ablation (now termed PLD) has been known since the 1960s after the invention of the first ruby laser. However, in the first two decades, PLD was something of a 'sleeping beauty' with only a few publications per year, as shown below. This state of hibernation ended abruptly with the advent of high T c superconductor research when scientists needed to grow high-quality thin films of multi-component high T c oxide systems. When most of the conventional growth techniques failed, the invention of PLD by T (Venky) Venkatesan clearly demonstrated that the newly discovered high-T c superconductor, YBa2Cu3O7-δ , could be stoichiometrically deposited as a high-quality nm-thin film with PLD [1]. As a remarkable highlight of this special issue, Venkatesan gives us his very personal reminiscence on these particularly innovative years of PLD beginning in 1986 [2]. After Venky's first paper [1], the importance of this invention was realized worldwide and the number of publications on PLD increased exponentially, as shown in figure 1. Figure 1. Figure 1. Published items per year with title or topic PLD. Data from Thomson Reuters Web of Knowledge in September 2013. After publication of Venky's famous paper in 1987 [1], the story of PLD's success began with a sudden jump in the number of publications, about 25 years ago. A first PLD textbook covering its basic understanding was soon published, in 1994, by Chrisey and Hubler [3]. Within a

  13. Microstructure and mechanical behavior of pulsed laser surface melted AISI D2 cold work tool steel

    NASA Astrophysics Data System (ADS)

    Yasavol, N.; Abdollah-zadeh, A.; Ganjali, M.; Alidokht, S. A.

    2013-01-01

    D2 cold work tool steel (CWTS) was subjected to pulse laser surface melting (PLSM) at constant frequency of 20 Hz Nd: YAG laser with different energies, scanning rate and pulse durations radiated to the surface. Characterizing the PLSM, with optical and field emission scanning electron microscopy, electron backscattered diffraction and surface hardness mapping technique was used to evaluate the microhardness and mechanical behavior of different regions of melting pool. Increasing laser energy and reducing the laser scanning rate results in deeper melt pool formation. Moreover, PLSM has led to entirely dissolution of the carbides and re-solidification of cellular/dendritic structure of a fine scale surrounded by a continuous interdendritic network. This caused an increase in surface microhardness, 2-4 times over that of the base metal.

  14. Pulse shaping effects on weld porosity in laser beam spot welds : contrast of long- & short- pulse welds.

    SciTech Connect

    Ellison, Chad M.; Perricone, Matthew J.; Faraone, Kevin M.; Norris, Jerome T.

    2007-10-01

    Weld porosity is being investigated for long-pulse spot welds produced by high power continuous output lasers. Short-pulse spot welds (made with a pulsed laser system) are also being studied but to a much small extent. Given that weld area of a spot weld is commensurate with weld strength, the loss of weld area due to an undefined or unexpected pore results in undefined or unexpected loss in strength. For this reason, a better understanding of spot weld porosity is sought. Long-pulse spot welds are defined and limited by the slow shutter speed of most high output power continuous lasers. Continuous lasers typically ramp up to a simmer power before reaching the high power needed to produce the desired weld. A post-pulse ramp down time is usually present as well. The result is a pulse length tenths of a second long as oppose to the typical millisecond regime of the short-pulse pulsed laser. This study will employ a Lumonics JK802 Nd:YAG laser with Super Modulation pulse shaping capability and a Lasag SLS C16 40 W pulsed Nd:YAG laser. Pulse shaping will include square wave modulation of various peak powers for long-pulse welds and square (or top hat) and constant ramp down pulses for short-pulse welds. Characterization of weld porosity will be performed for both pulse welding methods.

  15. The simulation of behaviors of photodetectors under pulsed laser irritation

    NASA Astrophysics Data System (ADS)

    Zheng, Xin; Cheng, Xiang-ai; Yu, Xiangyang; Qian, Le; Jiang, Tian

    2013-05-01

    Precise simulation of transient electrical behaviors of photodetectors under laser irradiation is becoming an increasingly concern. It not only can allow a detailed study and analysis of complex phenomena that cannot be carried out by experiments, but gives valuable information about the physical mechanisms which ultimately determine the response of the photodetectors. Finite difference numerical technique is adopted in the simulation to calculate the current response of photodetectors under pulsed laser irritation in this paper. To simulation the behaviors of photodetectors under pulsed laser irritation, the transport and trapping of carries and external circuit effects, including load resistance, junction capacitance, and parasitic capacitance, are considered. The basic equations governing the carrier behaviors are solved, including Poisson's equation, the carrier motion equations, and the carrier continuity equations. The simulated transient carrier density and velocities are present, as well as corresponding transient electric field distributions. The behaviors of electrons and holes and its contributions to the external current response are analyzed. Then a general and brief image of the transient progress of photodetectors under pulsed laser irritation is established. How the carrier is induced, transported, and trapped and whether they make any significant contribution to the external current response are discussed. Besides, bias dependent response is also studied. Higher bias will improver the behaviors of photodetectors under pulsed laser irritation. The simulated results and theory analysis will show valuable clue for future research on the behaviors of photodetectors irradiated by pulsed laser.

  16. Medical applications of ultra-short pulse lasers

    SciTech Connect

    Kim, B M; Marion, J E

    1999-06-08

    The medical applications for ultra short pulse lasers (USPLs) and their associated commercial potential are reviewed. Short pulse lasers offer the surgeon the possibility of precision cutting or disruption of tissue with virtually no thermal or mechanical damage to the surrounding areas. Therefore the USPL offers potential improvement to numerous existing medical procedures. Secondly, when USPLs are combined with advanced tissue diagnostics, there are possibilities for tissue-selective precision ablation that may allow for new surgeries that cannot at present be performed. Here we briefly review the advantages of short pulse lasers, examine the potential markets both from an investment community perspective, and from the view. of the technology provider. Finally nominal performance and cost requirements for the lasers, delivery systems and diagnostics and the present state of development will be addressed.

  17. Processing condition influence on the characteristics of gold nanoparticles produced by pulsed laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Nikov, R. G.; Nikolov, A. S.; Nedyalkov, N. N.; Atanasov, P. A.; Alexandrov, M. T.; Karashanova, D. B.

    2013-06-01

    A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental (λ = 1064 nm), second (λSHG = 532) and third (λTHG = 355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532 nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λirrad = 532 nm (laser energy 40 mJ) at different times up to 25 min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.

  18. Penetration in GTA welding

    SciTech Connect

    Heiple, C.R.; Burgardt, P.

    1990-01-01

    The size and shape of the weld bead produced in GTA welding depends on the magnitude and distribution of the energy incident on the workpiece surfaces as well as the dissipation of that energy in the workpiece. The input energy is largely controllable through the welding parameters selected, however the dissipation of that energy in the workpiece is less subject to control. Changes in energy dissipation can produce large changes in weld shape or penetration. Heat transport away from the weld pool is almost entirely by conduction, but heat transport in the weld pool is more complicated. Heat conduction through the liquid is an important component, but heat transport by convection (mass transport) is often the dominant mechanism. Convective heat transport is directional and changes the weld pool shape from that produced by conduction alone. Surface tension gradients are often the dominant forces driving fluid flow in GTA weld pools. These gradients are sensitive functions of weld pool chemistry and the energy input distribution to the weld. Experimental and theoretical work conducted primarily in the past decade has greatly enhanced our understanding of weld pool fluid flow, the forces which drive it, and its effects on weld pool shape. This work is reviewed here. While less common, changes in energy dissipation through the unmelted portion of the workpiece can also affect fusion zone shape or penetration. These effects are also described. 41 refs., 9 figs.

  19. Pulsed lasers in dentistry: sense or nonsense?

    NASA Astrophysics Data System (ADS)

    Koort, Hans J.; Frentzen, Matthias

    1991-05-01

    The great interest in the field of laser applications in dentistry provokes the question, if all these new techniques may really fulfill advantages, which are expected after initial in-vitro studies. Whereas laser surgery of soft oral tissues has been developed to a standard method, laser treatment of dental hard tissues and the bone are attended with many unsolved problems. Different laser types, especially pulsed lasers in a wide spectrum of wavelengths have been proofed for dental use. Today neither the excimer lasers, emitting in the far uv-range from 193 to 351 nm, nor the mid-infrared lasers like Nd:YAG (1,064 μm), Ho:YAG (2,1 μm) and Er:YAG (2,96 μm) or the C02-laser (10,6 μm) show mechanism of interaction more carefully and faster than a preparation of teeth with diamond drillers. The laser type with the most precise and considerate treatment effects in the moment is the short pulsed (15 ns) ArF-excimer laser with a wavelength of 193 nm. However this laser type has not yet the effectivity of mechanical instruments and it needs a mirror system to deliver the radiation. Histological results point out, that this laser shows no significant pathological alterations in the adjacent tissues. Another interesting excimer laser, filled with XeCI and emitting at a wavelength of 308 nm has the advantage to be good to deliver through quartz fibers. A little more thermal influence is to be seen according to the longer wavelength. Yet the energy density, necessary to cut dental hard tissues will not be reached with the laser systems available now. Both the pulsed Er:YAG- (2,94 μm, pulse duration 250 s) and the Ho:YAG -laser (2,1 μm, pulse duration 250 μs) have an effective coupling of the laser energy to hydrogeneous tissues, but they do not work sufficient on healthy enamel and dentine. The influence to adjacent healthy tissue is not tolerable, especially in regard of the thermal damage dentine and pulp tissues. Moreover, like the 193 nm ArF-excimer laser

  20. Development of pulse laser processing for mounting fiber Bragg grating

    SciTech Connect

    Nishimura, Aikihko; Shimada, Yukihiro; Yonemoto, Yukihiro; Suzuki, Hirokazu; Ishibashi, Hisayoshi

    2012-07-11

    Pulse laser processing has been developed for the application of industrial plants in monitoring and maintenance. Surface cleaning by nano-second laser ablation was demonstrated for decontamination of oxide layers of Cr contained steel. Direct writing by femtosecond processing induced a Bragg grating in optical fiber to make it a seismic sensor for structural health monitoring. Adhesive cement was used to fix the seismic sensor on the surface of reactor coolant pipe material. Pulse laser processing and its related technologies were presented to overcome the severe accidents of nuclear power plants.

  1. Development of pulse laser processing for mounting fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Nishimura, Aikihko; Shimada, Yukihiro; Yonemoto, Yukihiro; Suzuki, Hirokazu; Ishibashi, Hisayoshi

    2012-07-01

    Pulse laser processing has been developed for the application of industrial plants in monitoring and maintenance. Surface cleaning by nano-second laser ablation was demonstrated for decontamination of oxide layers of Cr contained steel. Direct writing by femtosecond processing induced a Bragg grating in optical fiber to make it a seismic sensor for structural health monitoring. Adhesive cement was used to fix the seismic sensor on the surface of reactor coolant pipe material. Pulse laser processing and its related technologies were presented to overcome the severe accidents of nuclear power plants.

  2. Pulse laser machining and particulate separation from high impact polystyrene

    NASA Astrophysics Data System (ADS)

    Arif, Saira; Kautek, Wolfgang

    2014-01-01

    Opaque high impact polystyrene (HIPS) contaminated with graphite particles and poly(styrene-co-divinyl benzene) spheres can only be removed efficiently with nanosecond-pulsed laser radiation of 532 nm while the substrate is preserved. The destruction thresholds are 1-2 orders of magnitude lower than that of other common technical polymers. The inhomogeneously distributed polybutadiene composite component led to enhanced light scattering in the polystyrene matrix so that increased light absorption and energy density causes a comparatively low ablation threshold. Due to this fact there is advantageous potential for pulse laser machining at comparatively low fluences.

  3. Local immunity in treating skin melanoma by neodymium pulsed laser

    NASA Astrophysics Data System (ADS)

    Moskalik, Konstantin G.

    1997-06-01

    The number and correlation of skin stroma cells was studied on mice C57B1 with the subcutaneously transplanted melanoma B16 which was exposed to neodymium pulsed laser radiation. Within 1-5 days after the exposure the total number of the free skin stroma cells was found to increase in the periphery from the radiation epicenter and the number of lymphocytes, macrophages and leucocytes tended to grow. Lymphoid infiltration was also revealed in the preparations of the epithelized wound and cicatrix on the skin melanoma sites in the patients who had undergone pulsed laser radiation therapy.

  4. Monitoring Weld Penetration Optically From Within Torch

    NASA Technical Reports Server (NTRS)

    Smith, Matthew A.; Gilbert, Jeffrey L.; Linsacum, Deron L.; Gutlow, David A.

    1993-01-01

    Photodetector or optical fiber leading to photodetector mounted inside gas/tungsten arc welding torch to monitor arc light reflected from oscillating surface of weld pool. Proposed optical monitoring components preserve compact profile of welding torch, maintained in fixed aim at weld-pool position at end of welding torch, and protected against bumping external objects.

  5. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    SciTech Connect

    Every, A. G.; Utegulov, Z. N.; Veres, I. A.

    2015-03-31

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green’s functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

  6. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    NASA Astrophysics Data System (ADS)

    Every, A. G.; Utegulov, Z. N.; Veres, I. A.

    2015-03-01

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

  7. Ultrashort-pulse laser generated nanoparticles of energetic materials

    DOEpatents

    Welle, Eric J.; Tappan, Alexander S.; Palmer, Jeremy A.

    2010-08-03

    A process for generating nanoscale particles of energetic materials, such as explosive materials, using ultrashort-pulse laser irradiation. The use of ultrashort laser pulses in embodiments of this invention enables one to generate particles by laser ablation that retain the chemical identity of the starting material while avoiding ignition, deflagration, and detonation of the explosive material.

  8. Model for nonequilibrium segregation during pulsed laser annealing

    SciTech Connect

    Wood, R.F.

    1980-08-01

    Highly nonequilibrium thermodynamic processes occur during the ultrarapid recrystallization characteristic of pulsed laser annealing. Values of interface segregation coefficients are observed to differ from equilibrium values by as much as three orders of magnitude and equilibrium solubility limits may be exceeded by similar magnitudes. In this letter, a model is developed which accounts quantitatively for these effects.

  9. Ultrashort pulse laser microsurgery system with plasma luminescence feedback control

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchik, A.M.; Gold, D.M.; Darrow, C.B.; Da Silva, L.B.

    1997-11-10

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue during ultrashort pulse laser (USPL) micro-spinal surgery. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  10. Numerical optimization approaches of single-pulse conduction laser welding by beam shape tailoring

    NASA Astrophysics Data System (ADS)

    Sundqvist, J.; Kaplan, A. F. H.; Shachaf, L.; Brodsky, A.; Kong, C.; Blackburn, J.; Assuncao, E.; Quintino, L.

    2016-04-01

    While circular laser beams are usually applied in laser welding, for certain applications tailoring of the laser beam shape, e.g. by diffractive optical elements, can optimize the process. A case where overlap conduction mode welding should be used to produce a C-shaped joint was studied. For the dimensions studied in this paper, the weld joint deviated significantly from the C-shape of the single-pulse laser beam. Because of the complex heat flow interactions, the process requires optimization. Three approaches for extracting quantitative indicators for understanding the essential heat flow contributions process and for optimizing the C-shape of the weld and of the laser beam were studied and compared. While integral energy properties through a control volume and temperature gradients at key locations only partially describe the heat flow behaviour, the geometrical properties of the melt pool isotherm proved to be the most reliable method for optimization. While pronouncing the C-ends was not sufficient, an additional enlargement of the laser beam produced the desired C-shaped weld joint. The approach is analysed and the potential for generalization is discussed.

  11. Evaluation of molten area in micro-welding of monocrystalline silicon and glass

    NASA Astrophysics Data System (ADS)

    Nordin, I. H. W.; Okamoto, Y.; Miyamoto, I.; Okada, A.

    2016-02-01

    Characteristics of the molten area in micro-welding of monocrystalline silicon and glass are described. In this study, 4 types of laser beam, which are nanosecond pulsed laser and picosecond pulsed laser of 532 nm and 1064 nm in wavelength were used for joining monocrystalline silicon and glass. Influence of wavelength and pulse duration on microwelding of monocrystalline silicon and glass was experimentally investigated under the same spot diameter, and the molten area of monocrystalline silicon and glass was characterized. A splash area of molten silicon with 532 nm wavelength was wider than that with 1064 nm in a nanosecond pulse laser. However, its splash area of molten silicon with 1064 nm changed drastically at certain pulse energy of 11 μJ in a nanosecond pulse laser. On the other hand, 12.5 ps pulsed laser still kept a stable molten area appearance even at pulse energy of 11 μJ. A splash area of molten silicon around the weld bead line was obvious in the nanosecond pulsed laser. On the other hand, there was no remarkable molten splash around the weld bead line in the picosecond pulsed laser. It is concluded that the combination of picosecond pulse duration and infrared wavelength leads to a stable molten area appearance of the weld bead.

  12. Automated and aluminum welding technology

    NASA Astrophysics Data System (ADS)

    Jones, Clyde S.

    1994-10-01

    Automated welding technology and techniques for welding advanced aluminum alloys with potential for industrial and commercial applications have been developed by the National Aeronautics and Space Administration at the Marshall Space Flight Center. These technologies are being offered to private companies for commercial development, and include: Variable polarity plasma arc welding, a welding process that produces high-quality aluminum welds for fabrication of the space shuttle external tank and space station common module structures. This process uses reverse polarity pulses to produce welds virtually free of internal defects. Advanced weld sensor technology, comprised of machine vision-based weld seam tracking that uses both structured and global laser illumination for finding weld joints, even those difficult to discern by the human eye. Weld pool feedback is accomplished with a vision system to measure arc symmetry and molten weld pool geometry. A weld bead profiler trails the welding torch. It provides feedback to the process control system, which records quality control data.

  13. Laser welding in space

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.; Workman, G. L.

    1991-01-01

    Autogenous welds in 304 stainless steel were performed by Nd-YAG laser heating in a simulated space environment. Simulation consists of welding on the NASA KC-135 aircraft to produce the microgravity and by containing the specimen in a vacuum chamber. Experimental results show that the microgravity welds are stronger, harder in the fusion zone, have deeper penetration and have a rougher surface rippling of the weld pool than one-g welds. To perform laser welding in space, a solar-pumped laser concept that significantly increases the laser conversion efficiency and makes welding viable despite the limited power availability of spacecraft is proposed.

  14. Solidification of underwater wet welds

    SciTech Connect

    Pope, A.M.; Medeiros, R.C. de; Liu, S.

    1995-12-31

    It is well known that the shape of a weld pool can influence the microstructure and segregation pattern of the final solidified weld metal. Mechanical properties and susceptibility to defects are consequently affected by the solidification mode of the weld. In this work the solidification behavior of weld beads deposited in air and underwater wet welding using rutile electrodes were compared. The welds were deposited by gravity feed, on low carbon, manganese steel plates using similar welding conditions. Macroscopic observation of the weld craters showed that welds deposited in air presented an elliptical weld pool. The underwater wet welds, on the other hand, solidified with a tear drop shape. Although the welds differed in shape, their lengths were approximately the same. Microscopic examinations carried out on transverse, normal and longitudinal sections revealed a coarser columnar grain structure in the underwater welds. These results suggest that the tear-drop shaped pool induced solidification in a preferred orientation with segregation more likely in welds deposited under wet conditions. This change in weld pool geometry can be explained by the surface heat loss conditions that occur in a wet weld: slower when covered by the steam bubble and faster in the region in contact with water behind the pool.

  15. Wavelength Effects In Femtosecond Pulsed Laser Ablation And Deposition

    SciTech Connect

    Castillejo, Marta; Nalda, Rebeca de; Oujja, Mohamed; Sanz, Mikel

    2010-10-08

    Ultrafast pulsed laser irradiation of solid materials is highly attractive for the micro-and nanostructuring of substrates and for the fabrication of nanostructured deposits. Femtosecond laser pulses promote efficient material removal with reduced heat transfer and high deposition rates of nanometer scale particles free of microscopic particulates. Most of the studies to date have been performed with light pulses centered around the peak wavelength of the Titanium:Sapphire laser, around 800 nm. Analysis of the process over a broader range of wavelengths can provide important information about the processes involved and serve as experimental tests for advanced theoretical models. We report on our current investigations on the effect that laser wavelength of femtosecond pulses has on the superficial nanostructuring induced on biopolymer substrates, and on the characteristics of nanostructured deposits grown by pulsed laser deposition from semiconductor targets.

  16. Pathogen reduction in human plasma using an ultrashort pulsed laser.

    PubMed

    Tsen, Shaw-Wei D; Kingsley, David H; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma. PMID:25372037

  17. Electroporation visualized under a multishot pulsed laser fluorescence microscope system

    NASA Astrophysics Data System (ADS)

    Itoh, Hiroyasu; Yu, Irene I. K.; Hibino, Masahiro; Hayakawa, Tsuyoshi; Kinosita, Kazuhiko, Jr.

    1993-10-01

    We describe a new fluorescence microscope system, which is the third generation of our pulsed-laser microscope systems developed for the purpose of capturing rapid cellular phenomena. Time resolution of this latest version is supported by the combination of a Q- switched Nd:YAG laser producing a burst of 4 pulses and a large format framing camera. We obtain series images at intervals on the order of 10 microsecond(s) with exposure times of 30 ns. With this multi-shot pulsed laser fluorescence microscope system, we examined the behavior of the transmembrane potential in a sea urchin egg under an intense electric field. Irreversible process of cell electroporation was revealed in serial images taken under a single electric pulse of microsecond duration.

  18. Optical modulation of astrocyte network using ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Yoon, Jonghee; Ku, Taeyun; Chong, Kyuha; Ryu, Seung-Wook; Choi, Chulhee

    2012-03-01

    Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

  19. Pathogen Reduction in Human Plasma Using an Ultrashort Pulsed Laser

    PubMed Central

    Tsen, Shaw-Wei D.; Kingsley, David H.; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M.; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma. PMID:25372037

  20. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.

    1992-01-01

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

  1. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.

    1992-10-01

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

  2. Self-directed control of pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Stark, E. F.; Laube, S. J. P.

    1993-10-01

    Implementation of self-directed control of pulsed laser deposition (PLD) requires actuators, sensors, and a materials and processing knowledge base. Improvements in quality and reproducibility of material deposits are achieved by driving the process toward desired operating regions. Empirical relationships are determined experimentally to describe the complex dynamical interactions of laser parameters. Feedback control based on this description can then be implemented to reduce process disorder and effectively produce consistent coatings with desired properties.

  3. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    SciTech Connect

    Shukui Zhang; Stephen Benson; John Hansknecht; David Hardy; George Neil; Michelle D. Shinn

    2006-08-27

    This paper describes phase noise measurements of several different laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on state-of-the-art short pulse lasers, especially drive lasers for photocathode injectors. Phase noise comparison of the FEL drive laser, electron beam and FEL laser output also will be presented.

  4. Phase Noise Comparision of Short Pulse Laser Systems

    SciTech Connect

    S. Zhang; S. V. Benson; J. Hansknecht; D. Hardy; G. Neil; Michelle D. Shinn

    2006-12-01

    This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.

  5. Pulse laser ablation at water-air interface

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000 m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy, and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history.

  6. Pulsed laser ablation and deposition of niobium carbide

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation-deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  7. Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

    SciTech Connect

    Liu, Chunyang Sui, Xin; Yang, Fang; Ma, Wei; Li, Jishun; Xue, Yujun; Fu, Xing

    2014-03-15

    A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of the microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.

  8. Effect of wavelength and pulse duration on laser micro-welding of monocrystalline silicon and glass

    NASA Astrophysics Data System (ADS)

    Nordin, I. H. W.; Okamoto, Y.; Okada, A.; Jiang, H.; Sakagawa, T.

    2016-04-01

    Micro-welding characteristics of silicon and glass by pulsed lasers are described. In this study, four types of laser beam, which are nanosecond pulsed laser and picosecond pulsed laser of 532 and 1064 nm in wavelength, were used for joining monocrystalline silicon and glass. Influence of wavelength and pulse duration on micro-welding of monocrystalline silicon and glass was experimentally investigated under the same spot diameter, and the molten area of monocrystalline silicon and glass was characterized. Finally, the breaking strength was evaluated for the overlap weld joint with different pulse duration and wavelength. A splash area of molten silicon around the weld bead line was obvious in the nanosecond pulsed laser. On the other hand, there was no remarkable molten splash around the weld bead line in the picosecond pulsed laser. Breaking strength of specimens with 1064 nm wavelength was higher than with 532 nm wavelength in nanosecond laser, whereas breaking strength of laser-irradiated specimen by picosecond pulse duration was higher than that by nanosecond pulse duration. It is concluded that the combination of picosecond pulse duration and infrared wavelength leads to the stable molten area appearance of the weld bead and higher breaking strength in micro-welding of glass and monocrystalline silicon.

  9. Optimizatin Of Pulsed Nd:YAG Laser Parameters For Titanium Seam-Welding

    SciTech Connect

    Akman, E.; Canel, T.; Demir, A.; Sinmazcelik, T.

    2007-04-23

    Titanium alloys are the most advantageous metals for the medical and aerospace industry because of their light weight and excellent corrosion resistance. Several techniques were investigated to achieve reliable welds with optimal distortion for the fabrication components used in industry. Laser welding is the most important joining technique because of its precision, rapid processing. For pulse mode Nd:YAG laser; pulse shape, energy, duration, repetition rate and peak power are the most important parameters effects the weld quality. And also the combinations of these parameters are very important for pulsed laser seam-welding. In this study, an experimental work has been done to determine the pulsed laser seam-welding parameters for 3mm thick titanium alloys using the Lumonics JK760TR Nd:YAG pulsed laser.

  10. Material processing with ultra-short pulse lasers working in 2μm wavelength range

    NASA Astrophysics Data System (ADS)

    Voisiat, B.; Gaponov, D.; Gečys, P.; Lavoute, L.; Silva, M.; Hideur, A.; Ducros, N.; Račiukaitis, G.

    2015-03-01

    New wavelengths of laser radiation are of interest for material processing. Results of application of the all-fiber ultrashort pulsed laser emitting in 2 µm range, manufactured by Novae, are presented. Average output power was 4.35 W in a single-spatial-mode beam centered at the 1950 nm wavelength. Pulses duration was 40 ps, and laser operated at 4.2 MHz pulse repetition rate. This performance corresponded to 25 kW of pulse peak power and almost 1 µJ in pulse energy. Material processing was performed using three different focusing lenses (100, 30 and 18 mm) and mechanical stages for the workpiece translation. 2 µm laser radiation is strongly absorbed by some polymers. Swelling of PMMA surface was observed for scanning speed above 5 mm/s using the average power of 3.45 W focused with the 30 mm lens. When scanning speed was reduced below 4 mm/s, ablation of PMMA took place. The swelling of PMMA is a consequence of its melting due to absorbed laser power. Therefore, experiments on butt welding of PMMA and overlapping welding of PMMA with other polymers were performed. Stable joint was achieved for the butt welding of two PMMA blocks with thickness of 5 mm. The laser was used to cut a Kapton film on a paper carrier with the same set-up as previous. The cut width depended on the cutting speed and focusing optics. A perfect cut with a width of 11 µm was achieved at the translation speed of 60 mm/s.

  11. Optically controlled welding system

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S. (Inventor)

    1989-01-01

    An optically controlled welding system (10) wherein a welding torch (12) having through-the-torch viewing capabilities is provided with an optical beam splitter (56) to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder (15) to make the welding torch responsive thereto. Other features includes an actively cooled electrode holder (26) which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm (28) and a weld pool contour detector (14) comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom being characteristic of a penetrated or unpenetrated condition of the weld pool.

  12. Optically controlled welding system

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S. (Inventor)

    1988-01-01

    An optically controlled welding system wherein a welding torch having through-the-torch viewing capabilities is provided with an optical beam splitter to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder to make the welding torch responsive thereto. Other features include an actively cooled electrode holder which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm, and a weld pool contour detector comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom, being characteristic of a penetrated or unpenetrated condition of the weld pool.

  13. Time-dependent calculations of molten pool formation and thermal plasma with metal vapour in gas tungsten arc welding

    NASA Astrophysics Data System (ADS)

    Tanaka, M.; Yamamoto, K.; Tashiro, S.; Nakata, K.; Yamamoto, E.; Yamazaki, K.; Suzuki, K.; Murphy, A. B.; Lowke, J. J.

    2010-11-01

    A gas tungsten arc (GTA) was modelled taking into account the contamination of the plasma by metal vapour from the molten anode. The whole region of GTA atmosphere including the tungsten cathode, the arc plasma and the anode was treated using a unified numerical model. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of the shielding gas and metal vapour. The transient two-dimensional distributions of temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the molten pool as a function of time for a 150 A arc current at atmospheric pressure, both for helium and argon gases. It was shown that the thermal plasma in the GTA was influenced by iron vapour from the molten pool surface and that the concentration of iron vapour in the plasma was dependent on the temperature of the molten pool. GTA on high sulfur stainless steel was calculated to discuss the differences between a low sulfur and a high sulfur stainless steel anode. Helium was selected as the shielding gas because a helium GTA produces more metal vapour than an argon GTA. In the GTA on a high sulfur stainless steel anode, iron vapour and current path were constricted. Radiative emission density in the GTA on high sulfur stainless steel was also concentrated in the centre area of the arc plasma together with the iron vapour although the temperature distributions were almost the same as that in the case of a low sulfur stainless steel anode.

  14. Electromagnetic Pulses at Short-Pulse Laser Facilities

    SciTech Connect

    Brown, Jr., C G; Throop, A; Eder, D; Kimbrough, J

    2007-08-28

    Electromagnetic Pulse (EMP) is a known issue for short-pulse laser facilities, and will also be an issue for experiments using the advanced radiographic capability (ARC) at the National Ignition Facility (NIF). The ARC diagnostic uses four NIF beams that are compressed to picosecond durations for backlighting ignition capsules and other applications. Consequently, we are working to understand the EMP due to high-energy (MeV) electrons escaping from targets heated by short-pulse lasers. Our approach is to measure EMP in the Titan short-pulse laser at Lawrence Livermore National Laboratory (LLNL) and to employ that data to establish analysis and simulation capabilities. We have installed a wide variety of probes inside and outside the Titan laser chamber. We have high-frequency B-dots and D-dots, a photodiode, and fast current-viewing and integrating current transformers. The probe outputs are digitized by 10 and 20 Gsample/s oscilloscopes. The cables and oscilloscopes are well shielded to reduce noise. Our initial measurement campaign has yielded data useful mainly from hundreds of MHz to several GHz. We currently are supplementing our high-frequency probes with lower-frequency ones to obtain better low-frequency data. In order to establish analysis and simulation capabilities we are modeling the Titan facility using various commercial and LLNL numerical electromagnetic codes. We have simulated EMP generation by having a specified number of electrons leave the target and strike the chamber wall and other components in the chamber. This short impulse of electrons has a corresponding broad spectrum, exciting high-frequency structure in the resulting EMP. In this paper, we present results of our initial measurement campaign and comparisons between the measurements and simulations.

  15. Electromagnetic Pulses at Short-Pulse Laser Facilities

    SciTech Connect

    Brown, C G; Throop, A; Eder, D; Kimbrough, J

    2008-02-04

    Electromagnetic Pulse (EMP) is a known issue for short-pulse laser facilities, and will also be an issue for experiments using the advanced radiographic capability (ARC) at the National Ignition Facility (NIF). The ARC diagnostic uses four NIF beams that are compressed to picosecond durations for backlighting ignition capsules and other applications. Consequently, we are working to understand the EMP due to high-energy (MeV) electrons escaping from targets heated by short-pulse lasers. Our approach is to measure EMP in the Titan short-pulse laser at Lawrence Livermore National Laboratory (LLNL) and to employ that data to establish analysis and simulation capabilities. We have installed a wide variety of probes inside and outside the Titan laser chamber. We have high-frequency B-dot and D-dot probes, a photodiode, and fast current-viewing and integrating current transformers. The probe outputs are digitized by 10 and 20 Gsample/s oscilloscopes. The cables and oscilloscopes are well shielded to reduce noise. Our initial measurement campaign has yielded data useful mainly from several hundreds of MHz to several GHz. We currently are supplementing our high-frequency probes with lower-frequency ones to obtain better low-frequency data. In order to establish analysis and simulation capabilities we are modeling the Titan facility using various commercial and LLNL numerical electromagnetics codes. We have simulated EMP generation by having a specified number of electrons leave the target and strike the chamber wall and other components in the chamber. This short impulse of electrons has a correspondingly broad spectrum, exciting high-frequency structure in the resulting EMP. In this paper, we present results of our initial measurement campaign and comparisons between the measurements and simulations.

  16. Resonant infrared pulsed laser deposition of cyclic olefin copolymer films

    SciTech Connect

    Singaravelu, Senthil R.; Klopf, John M.; Schriver, Kenneth E.; Park, HyeKyoung; Kelley, Michael J.; Haglund, Jr., Richard F.

    2013-08-01

    Barrier materials on thin-film organic optoelectronic devices inhibit the uptake of water, oxygen, or environmental contaminants, and fabricating them is a major challenge. By definition, these barrier layers must be insoluble, so the usual routes to polymer- or organic-film deposition by spin coating are not problematic. In this paper, we report comparative studies of pulsed laser deposition of cyclic olefin copolymer (COC), an excellent moisture barrier and a model system for a larger class of protective materials that are potentially useful in organic electronic devices, such as organic light-emitting diodes (OLEDs). Thin films of COC were deposited by resonant and nonresonant infrared pulsed laser ablation of solid COC targets, using a free-electron laser tuned to the 3.43 μm C–H stretch of the COC, and a high-intensity nanosecond Q-switched laser operated at 1064 nm. The ablation craters and deposited films were characterized by scanning-electron microscopy, Fourier-transform infrared spectrometry, atomic-force microscopy, high-resolution optical microscopy, and surface profilometry. Thermal-diffusion calculations were performed to determine the temperature rise induced in the film at the C–H resonant wavelength. The results show that resonant infrared pulsed laser deposition (RIR-PLD) is an effective, low-temperature thin-film deposition technique that leads to evaporation and deposition of intact molecules in homogeneous, smooth films. Nonresonant PLD, on the other hand, leads to photothermal damage, degradation of the COC polymers, and to the deposition only of particulates.

  17. Resonant infrared pulsed laser deposition of cyclic olefin copolymer films

    NASA Astrophysics Data System (ADS)

    Singaravelu, S.; Klopf, J. M.; Schriver, K. E.; Park, H. K.; Kelley, M. J.; Haglund, R. F.

    2014-03-01

    Barrier materials on thin-film organic optoelectronic devices inhibit the uptake of water, oxygen, or environmental contaminants, and fabricating them is a major challenge. By definition, these barrier layers must be insoluble, so the usual routes to polymer- or organic-film deposition by spin coating are not problematic. In this paper, we report comparative studies of pulsed laser deposition of cyclic olefin copolymer (COC), an excellent moisture barrier and a model system for a larger class of protective materials that are potentially useful in organic electronic devices, such as organic light-emitting diodes (OLEDs). Thin films of COC were deposited by resonant and nonresonant infrared pulsed laser ablation of solid COC targets, using a free-electron laser tuned to the 3.43 μm C-H stretch of the COC, and a high-intensity nanosecond Q-switched laser operated at 1064 nm. The ablation craters and deposited films were characterized by scanning-electron microscopy, Fourier-transform infrared spectrometry, atomic-force microscopy, high-resolution optical microscopy, and surface profilometry. Thermal-diffusion calculations were performed to determine the temperature rise induced in the film at the C-H resonant wavelength. The results show that resonant infrared pulsed laser deposition (RIR-PLD) is an effective, low-temperature thin-film deposition technique that leads to evaporation and deposition of intact molecules in homogeneous, smooth films. Nonresonant PLD, on the other hand, leads to photothermal damage, degradation of the COC polymers, and to the deposition only of particulates.

  18. Modeling of High-Energy Pulsed Laser Interactions with Coupons

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2003-02-06

    We describe a computational model of laser-materials interactions in the regime accessed by the solid state heat capacity lasers (SSHCLs) built at LLNL. We show that its predictions compare quite favorably with coupon experiments by the 10 kW SSHCL at LLNL. The body of this paper describes the following topics, listed by section number: (2) model in quiescent air, (3) comparison with experiments in quiescent air, (4) effects of air flow, (5) comparison with experiments involving air flow, (6) importance of material properties, (7) advantage of pulsed lasers over CW lasers, and (8) conclusions and recommendations.

  19. Acceleration Mechanism Of Pulsed Laser-Electromagnetic Hybrid Thruster

    SciTech Connect

    Horisawa, Hideyuki; Mashima, Yuki; Yamada, Osamu

    2011-11-10

    A fundamental study of a newly developed rectangular pulsed laser-electromagnetic hybrid thruster was conducted. Laser-ablation plasma in the thruster was induced through laser beam irradiation onto a solid target and accelerated by electrical means instead of direct acceleration only by using a laser beam. The performance of the thrusters was evaluated by measuring the ablated mass per pulse and impulse bit. As results, significantly high specific impulses up to 7,200 s were obtained at charge energies of 8.6 J. Moreover, from the Faraday cup measurement, it was confirmed that the speed of ions was accelerated with addition of electric energy.

  20. Plasma and Cavitation Dynamics during Pulsed Laser Microsurgery in vivo

    SciTech Connect

    Hutson, M. Shane; Ma Xiaoyan

    2007-10-12

    We compare the plasma and cavitation dynamics underlying pulsed laser microsurgery in water and in fruit fly embryos (in vivo)--specifically for nanosecond pulses at 355 and 532 nm. We find two key differences. First, the plasma-formation thresholds are lower in vivo --especially at 355 nm--due to the presence of endogenous chromophores that serve as additional sources for plasma seed electrons. Second, the biological matrix constrains the growth of laser-induced cavitation bubbles. Both effects reduce the disrupted region in vivo when compared to extrapolations from measurements in water.

  1. Defects in zinc oxide grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Ling, Francis C. C.; Wang, Zilan; Ping Ho, Lok; Younas, M.; Anwand, W.; Wagner, A.; Su, S. C.; Shan, C. X.

    2016-01-01

    ZnO films are grown on c-plane sapphire using the pulsed laser deposition method. Systematic studies on the effects of annealing are performed to understand the thermal evolutions of the defects in the films. Particular attention is paid to the discussions of the ZnO/sapphire interface thermal stability, the Zn-vacancy related defects having different microstructures, the origins of the green luminescence (∼2.4-2.5 eV) and the near band edge (NBE) emission at 3.23 eV.

  2. Pulsed laser deposition of ITO thin films and their characteristics

    SciTech Connect

    Zuev, D. A. Lotin, A. A.; Novodvorsky, O. A.; Lebedev, F. V.; Khramova, O. D.; Petuhov, I. A.; Putilin, Ph. N.; Shatohin, A. N.; Rumyanzeva, M. N.; Gaskov, A. M.

    2012-03-15

    The indium tin oxide (ITO) thin films are grown on quartz glass substrates by the pulsed laser deposition method. The structural, electrical, and optical properties of ITO films are studied as a function of the substrate temperature, the oxygen pressure in the vacuum chamber, and the Sn concentration in the target. The transmittance of grown ITO films in the visible spectral region exceeds 85%. The minimum value of resistivity 1.79 Multiplication-Sign 10{sup -4} {Omega} cm has been achieved in the ITO films with content of Sn 5 at %.

  3. Active weld control

    NASA Technical Reports Server (NTRS)

    Powell, Bradley W.; Burroughs, Ivan A.

    1994-01-01

    Through the two phases of this contract, sensors for welding applications and parameter extraction algorithms have been developed. These sensors form the foundation of a weld control system which can provide action weld control through the monitoring of the weld pool and keyhole in a VPPA welding process. Systems of this type offer the potential of quality enhancement and cost reduction (minimization of rework on faulty welds) for high-integrity welding applications. Sensors for preweld and postweld inspection, weld pool monitoring, keyhole/weld wire entry monitoring, and seam tracking were developed. Algorithms for signal extraction were also developed and analyzed to determine their application to an adaptive weld control system. The following sections discuss findings for each of the three sensors developed under this contract: (1) weld profiling sensor; (2) weld pool sensor; and (3) stereo seam tracker/keyhole imaging sensor. Hardened versions of these sensors were designed and built under this contract. A control system, described later, was developed on a multiprocessing/multitasking operating system for maximum power and flexibility. Documentation for sensor mechanical and electrical design is also included as appendices in this report.

  4. Nanosecond laser ablation for pulsed laser deposition of yttria

    NASA Astrophysics Data System (ADS)

    Sinha, Sucharita

    2013-09-01

    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.

  5. Epidermal cooling during pulsed laser treatment of selected dermatoses

    NASA Astrophysics Data System (ADS)

    Nelson, J. Stuart; Anvari, Bahman; Tanenbaum, B. S.; Milner, Thomas E.; Kimel, Sol; Svaasand, Lars O.

    1996-01-01

    The clinical objective in laser treatment of selected dermatoses such as port wine stain (PWS), hemangioma and telangiectasia is to maximize thermal damage to the blood vessels, while at the same time minimizing nonspecific injury to the normal overlying epidermis. 'Dynamic' cooling of skin, whereby a cryogen is sprayed onto the surface for an appropriately short period of time (on the order of tens of milliseconds), may offer an effective method for eliminating epidermal thermal injury during laser treatment. We present theoretical and experimental investigations of the thermal response of skin to dynamic cooling in conjunction with pulsed laser irradiation at 585 nm. Computed temperature distributions indicate that cooling the skin immediately prior to pulsed laser irradiation with a cryogen spurt of tetrafluoroethane is an effective method for eliminating epidermal thermal injury during laser treatment of PWS. Experimental results show rapid reduction of skin surface temperature is obtained when using tetrafluoroethane spurts of 20 - 100 ms duration. Successful blanching of PWS without thermal injury to the overlying epidermis is accomplished.

  6. Fundamentals and industrial applications of ultrashort pulsed lasers at Bosch

    NASA Astrophysics Data System (ADS)

    König, Jens; Bauer, Thorsten

    2011-03-01

    Fundamental results of ablation processes of metals with ultrashort laser pulses in the far threshold fluence regime are shown and discussed. Time-resolved measurements of the plasma transmission exhibit two distinctive minima. The minima occurring within the first nanoseconds can be attributed to electrons and sublimated material emitted from the target surface, whereas the subsequent minimum after several 10 ns is due to particles and droplets after a thermal boiling process. Industrial applications of ultrashort pulsed laser micro machining in the Bosch Group are also shown with the production of exhaust gas sensors and common rail diesel systems. Since 2007, ultrashort laser pulses are used at the BOSCH plant in Bamberg for producing lambda-probes, which are made of a special ceramic layer system and can measure the exhaust gas properties faster and more accurately. This enables further reduction of emissions by optimized combustion control. Since 2009, BOSCH uses ultrashort pulsed lasers for micro-structuring the injector of common rail diesel systems. A drainage groove allows a tight system even at increased pressures up to 2000 bar. Diesel injection is thus even more reliable, powerful and environment-friendly.

  7. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    NASA Astrophysics Data System (ADS)

    Aronne, Antonio; Bloisi, Francesco; Calabria, Raffaela; Califano, Valeria; Depero, Laura E.; Fanelli, Esther; Federici, Stefania; Massoli, Patrizio; Vicari, Luciano R. M.

    2015-05-01

    Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  8. A Bright Neutron Source Driven by a Short Pulse Laser

    NASA Astrophysics Data System (ADS)

    Roth, Markus

    2012-10-01

    Neutrons are a unique tool to alter and diagnose material properties, and to exciting nuclear reactions, for many applications. Accelerator based spallation sources provide high neutron fluxes for research, but there is a growing need for more compact sources with higher peak brightness, whether fast or moderated neutrons. Intense lasers promise such as source, readily linkable to other experimental facilities, or deployable outside a laboratory setting. We present experimental results on the first short-pulse laser-driven neutron source powerful enough for radiography. A novel laser-driven ion acceleration mechanism (Breakout Afterburner), operating in the relativistic transparency regime, is used. Based on the mechanism's advantages, a laser-driven deuteron beam is used to achieve a new record in laser-neutron production, in numbers, energy and directionality. This neutron beam is a highly directional pulse < 1 ns at ˜ 1 cm from the target, with a flux > 40/2̂, and thus suitable for imaging applications with high temporal resolution. The beam contained, for the first time, neutrons with energies of up to 150 MeV. Thus using short pulse lasers, it is now possible to use the resulting hard x-rays and neutrons of different energies to radiograph an unknown object and to determine its material composition. Our data matches the simulated data for our test samples.

  9. Test results from LAGEOS-2 optical characterization using pulsed lasers

    NASA Technical Reports Server (NTRS)

    Varghese, Thomas K.; Selden, Michael; Oldham, Thomas; Clarke, Christopher; Zagwodzki, Thomas

    1993-01-01

    The Laser Geodynamic Satellite-2 (LAGEOS-2) has undergone extensive optical testing at NASA Goddard Space Flight Center during 1989. The techniques included measuring the far field diffraction pattern using cw and pulsed lasers. In the pulsed measurement technique, response of the satellite was studied by measuring the far-field diffraction pattern (FFDP) as a function of pulsewidth, wavelength, polarization, position in the FFDP, detector/processing techniques, and satellite orientation. The purpose of the pulsed laser testing was two-fold: (1) to characterize the satellite optical response with the detector and signal processing electronics currently used in most SLR stations using the portable laser ranging standard, and (2) to characterize the satellite response for various conditions using the highest bandwidth optical detector (streak camera) available for the next generation of satellite laser ranging (SLR) technology. The portable ranging standard employed multiple measurement devices and an optical calibration scheme to eliminate range-dependent and amplitude-dependent systematics. These precautions were taken to eliminate/minimize instrumental errors and provide maximum accuracy. For LAGEOS orbit (6000 Km), ground stations are located 34 to 38 Mu radians off the axis of the return signal from the satellite; therefore, an optical mask was used to restrict the field of view (FOV) of detection to this annular region of the FFDP. The two measurement techniques were implemented using an aperture sharing scheme and complemented each other by providing mutual verification.

  10. Pulse laser assisted optical tweezers for biomedical applications.

    PubMed

    Sugiura, Tadao; Maeda, Saki; Honda, Ayae

    2012-01-01

    Optical tweezers which enables to trap micron to nanometer sized objects by radiation pressure force is utilized for manipulation of particles under a microscope and for measurement of forces between biomolecules. Weak force of optical tweezers causes some limitations such as particle adhesion or steric barrier like lipid membrane in a cell prevent further movement of objects. For biomedical applications we need to overcome these difficulties. We have developed a technique to exert strong instantaneous force by use of a pulse laser beam and to assist conventional optical tweezers. A pulse laser beam has huge instantaneous laser power of more than 1000 times as strong as a conventional continuous-wave laser beam so that the instantaneous force is strong enough to break chemical bonding and molecular force between objects and obstacles. We derive suitable pulse duration for pulse assist of optical tweezers and demonstrate particle manipulation in difficult situations through an experiment of particle removal from sticky surface of glass substrate. PMID:23366922

  11. Hybrid micromachining using a nanosecond pulsed laser and micro EDM

    NASA Astrophysics Data System (ADS)

    Kim, Sanha; Kim, Bo Hyun; Chung, Do Kwan; Shin, Hong Shik; Chu, Chong Nam

    2010-01-01

    Micro electrical discharge machining (micro EDM) is a well-known precise machining process that achieves micro structures of excellent quality for any conductive material. However, the slow machining speed and high tool wear are main drawbacks of this process. Though the use of deionized water instead of kerosene as a dielectric fluid can reduce the tool wear and increase the machine speed, the material removal rate (MRR) is still low. In contrast, laser ablation using a nanosecond pulsed laser is a fast and non-wear machining process but achieves micro figures of rather low quality. Therefore, the integration of these two processes can overcome the respective disadvantages. This paper reports a hybrid process of a nanosecond pulsed laser and micro EDM for micromachining. A novel hybrid micromachining system that combines the two discrete machining processes is introduced. Then, the feasibility and characteristics of the hybrid machining process are investigated compared to conventional EDM and laser ablation. It is verified experimentally that the machining time can be effectively reduced in both EDM drilling and milling by rapid laser pre-machining prior to micro EDM. Finally, some examples of complicated 3D micro structures fabricated by the hybrid process are shown.

  12. Computational Design of Short Pulse Laser Driven Iron Opacity Experiments

    NASA Astrophysics Data System (ADS)

    Martin, Madison E.; London, Richard A.; Goluoglu, Sedat; Whitley, Heather D.

    2015-11-01

    Opacity is a critical parameter in the transport of radiation in systems such as inertial confinement fusion capsules and stars. The resolution of current disagreements between solar models and helioseismological observations would benefit from experimental validation of theoretical opacity models. Short pulse lasers can be used to heat targets to higher temperatures and densities than long pulse lasers and pulsed power machines, thus potentially enabling access to emission spectra at conditions relevant to solar models. In order to ensure that the relevant plasma conditions are accessible and that an emission measurement is practical, we use computational design of experiments to optimize the target characteristics and laser conditions. Radiation-hydrodynamic modeling, using HYDRA, is used to investigate the effects of modifying laser irradiance, target dimensions, and dopant dilution on the plasma conditions and emission of an iron opacity target. Several optimized designs reaching temperatures and densities relevant to the radiative zone of the sun will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.

  13. Approaches to solar cell design for pulsed laser power receivers

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.; Landis, Geoffrey A.

    1993-01-01

    Using a laser to beam power from Earth to a photovoltaic receiver in space could be a technology with applications to many space missions. Extremely high average-power lasers would be required in a wavelength range of 700-1000 nm. However, high-power lasers inherently operate in a pulsed format. Existing solar cells are not well designed to respond to pulsed incident power. To better understand cell response to pulsed illumination at high intensity, the PC-1D finite-element computer model was used to analyze the response of solar cells to continuous and pulsed laser illumination. Over 50 percent efficiency was calculated for both InP and GaAs cells under steady-state illumination near the optimum wavelength. The time-dependent response of a high-efficiency GaAs concentrator cell to a laser pulse was modeled, and the effect of laser intensity, wavelength, and bias point was studied. Three main effects decrease the efficiency of a solar cell under pulsed laser illumination: series resistance, L-C 'ringing' with the output circuit, and current limiting due to the output inductance. The problems can be solved either by changing the pulse shape or designing a solar cell to accept the pulsed input. Cell design possibilities discussed are a high-efficiency, light-trapping silicon cell, and a monolithic, low-inductance GaAs cell.

  14. Growth of metal oxide nanoparticles using pulsed laser ablation technique

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    Nano particles exhibit physical and chemical properties distinctively different from that of bulk due to high number of surface atoms, surface energy and surface area to volume ratio. Laser is a unique source of radiation and has been applied in the synthesis of nano structured metal oxides. The pulsed laser ablation (PLA) technique in liquid medium has been proven an effective and simple technique for preparing nanoparticles of high purity. Pulsed laser deposition (PLD) is another way to fabricate nano structured single crystal thin films of metal oxides. PLA technique has been applied in our laboratory for the growth of metal oxides such as nano-ZnO, nano-ZnO2 nano- SnO2, nano-Bi2O3, nano-NiO and nano-MnO2. Different techniques such as AFM, UV, FT-IR, PL and XRD were applied to characterize these materials. We will present our latest development in the growth of nano metal oxides using PLA and PLD.

  15. Making relativistic positrons using ultraintense short pulse lasers

    SciTech Connect

    Chen Hui; Wilks, S. C.; Bonlie, J. D.; Chen, S. N.; Cone, K. V.; Elberson, L. N.; Price, D. F.; Schneider, M. B.; Shepherd, R.; Stafford, D. C.; Tommasini, R.; Van Maren, R.; Beiersdorfer, P.; Gregori, G.; Meyerhofer, D. D.; Myatt, J.

    2009-12-15

    This paper describes a new positron source using ultraintense short pulse lasers. Although it has been theoretically studied since the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at the Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2x10{sup 10} positrons/s ejected at the back of approximately millimeter thick gold targets were detected. The targets were illuminated with short (approx1 ps) ultraintense (approx1x10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser-based positron source with its unique characteristics may complement the existing sources based on radioactive isotopes and accelerators.

  16. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Chen, C; Chen, S; Cone, K; Elberson, L; Gregori, G; Liang, E; Price, D; Van Maren, R; Meyerhofer, D D; Mithen, J; Murphy, C V; Myatt, J; Schneider, M; Shepherd, R; Stafford, D; Tommasini, R; Beiersdorfer, P

    2009-08-24

    This paper describes a new positron source produced using ultra-intense short pulse lasers. Although it has been studied in theory since as early as the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets were detected. The targets were illuminated with short ({approx}1 ps) ultra-intense ({approx}1 x 10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process, and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser based positron source with its unique characteristics may complements the existing sources using radioactive isotopes and accelerators.

  17. Laser Beam Welding of Nitride Steel Components

    NASA Astrophysics Data System (ADS)

    Gu, Hongping; Yin, Guobin; Shulkin, Boris

    Laser beam welding is a joining technique that has many advantages over conventional GMAW welding, such as low heat input, short cycle time as well as good cosmetic welds. Laser beam welding has been widely used for welding powertrain components in automotive industry. When welding nitride steel components, however, laser beam welding faces a great challenge. The difficulty lies in the fact that the nitride layer in the joint releases the nitrogen into the weld pool, resulting in a porous weld. This research presents an industrial ready solution to prevent the nitrogen from forming gas bubbles in the weld.

  18. Studying the mechanism of micromachining by short pulsed laser

    NASA Astrophysics Data System (ADS)

    Gadag, Shiva

    The semiconductor materials like Si and the transparent dielectric materials like glass and quartz are extensively used in optoelectronics, microelectronics, and microelectromechanical systems (MEMS) industries. The combination of these materials often go hand in hand for applications in MEMS such as in chips for pressure sensors, charge coupled devices (CCD), and photovoltaic (PV) cells for solar energy generation. The transparent negative terminal of the solar cell is made of glass on one surface of the PV cell. The positive terminal (cathode) on the other surface of the solar cell is made of silicon with a glass negative terminal (anode). The digital watches and cell phones, LEDs, micro-lens, optical components, and laser optics are other examples for the application of silicon and or glass. The Si and quartz are materials extensively used in CCD and LED for digital cameras and CD players respectively. Hence, three materials: (1) a semiconductor silicon and transparent dielectrics,- (2) glass, and (3) quartz are chosen for laser micromachining as they have wide spread applications in microelectronics industry. The Q-switched, nanosecond pulsed lasers are most extensively used for micro-machining. The nanosecond type of short pulsed laser is less expensive for the end users than the second type, pico or femto, ultra-short pulsed lasers. The majority of the research work done on these materials (Si, SiO 2, and glass) is based on the ultra-short pulsed lasers. This is because of the cut quality, pin point precision of the drilled holes, formation of the nanometer size microstructures and fine features, and minimally invasive heat affected zone. However, there are many applications such as large surface area dicing, cutting, surface cleaning of Si wafers by ablation, and drilling of relatively large-sized holes where some associated heat affected zone due to melting can be tolerated. In such applications the nanosecond pulsed laser ablation of materials is very

  19. Studying the mechanism of micromachining by short pulsed laser

    NASA Astrophysics Data System (ADS)

    Gadag, Shiva

    The semiconductor materials like Si and the transparent dielectric materials like glass and quartz are extensively used in optoelectronics, microelectronics, and microelectromechanical systems (MEMS) industries. The combination of these materials often go hand in hand for applications in MEMS such as in chips for pressure sensors, charge coupled devices (CCD), and photovoltaic (PV) cells for solar energy generation. The transparent negative terminal of the solar cell is made of glass on one surface of the PV cell. The positive terminal (cathode) on the other surface of the solar cell is made of silicon with a glass negative terminal (anode). The digital watches and cell phones, LEDs, micro-lens, optical components, and laser optics are other examples for the application of silicon and or glass. The Si and quartz are materials extensively used in CCD and LED for digital cameras and CD players respectively. Hence, three materials: (1) a semiconductor silicon and transparent dielectrics,- (2) glass, and (3) quartz are chosen for laser micromachining as they have wide spread applications in microelectronics industry. The Q-switched, nanosecond pulsed lasers are most extensively used for micro-machining. The nanosecond type of short pulsed laser is less expensive for the end users than the second type, pico or femto, ultra-short pulsed lasers. The majority of the research work done on these materials (Si, SiO 2, and glass) is based on the ultra-short pulsed lasers. This is because of the cut quality, pin point precision of the drilled holes, formation of the nanometer size microstructures and fine features, and minimally invasive heat affected zone. However, there are many applications such as large surface area dicing, cutting, surface cleaning of Si wafers by ablation, and drilling of relatively large-sized holes where some associated heat affected zone due to melting can be tolerated. In such applications the nanosecond pulsed laser ablation of materials is very

  20. Fundamental Mechanisms of Pulsed Laser Ablation of Biological Tissue

    NASA Astrophysics Data System (ADS)

    Albagli, Douglas

    The ability to cut and remove biological tissue with short pulsed laser light, a process called laser ablation, has the potential to revolutionize many surgical procedures. Ablation procedures using short pulsed lasers are currently being developed or used in many fields of medicine, including cardiology, ophthalmology, dermatology, dentistry, orthopedics, and urology. Despite this, the underlying physics of the ablation process is not well understood. In fact, there is wide disagreement over whether the fundamental mechanism is primarily photothermal, photomechanical, or photochemical. In this thesis, both experimental and theoretical techniques are developed to explore this issue. The photothermal model postulates that ablation proceeds through vaporization of the target material. The photomechanical model asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. I have developed a three dimensional model of the thermoelastic response of tissue to short pulsed laser irradiation which allows the time dependent stress distribution to be calculated given the optical, thermal and mechanical properties of the target. A complimentary experimental technique has been developed to verify this model, measure the needed physical properties of the tissue, and record the thermoelastic response of the tissue at the onset of ablation. The results of this work have been widely disseminated to the international research community and have led to significant findings which support the photomechanical model of ablation of tissue. First, the energy deposited in tissue is an order of magnitude less than that required for vaporization. Second, unlike the one-dimensional thermoelastic model of laser-induced stress generation that has appeared in the literature, the full three-dimensional model predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to

  1. Experimental study on photodiode damage by millisecond pulse laser irradiation

    NASA Astrophysics Data System (ADS)

    Wei, Zhi; Jin, Guangyong; Tan, Yong; Wang, Di

    2015-10-01

    The photoelectric detector is a very significance part in laser and its application system, but when photoelectric detector irradiated by high energy laser, the laser may cause thermal damage to the photoelectric detector, when the temperature more than its melting point and vaporization point, there will be a permanent damage in PIN photodetector, leading to the failure of photoelectric detector. In order to study the photodiode damage mechanism by millisecond pulse laser irradiation, a set of experimental system has been built, choosing appropriate pulsed laser parameters to irradiate silicon-based PIN photodiode and monitoring the surface temperature in the process of irradiation, until the PIN photodiode complete failure. The measurement results of real-time temperature, responsivity change and damage morphology were analyzed to conclude the failure reason of the PIN photodiode. The results showed that with the increase of laser energy, the PIN photodiode surface temperature would be also increased accordingly. Before the laser irradiation, the responsivity of PIN photodiode was the same. But after the laser irradiation, the responsivity of the PIN photodiode would be changed and with the increase of laser energy, the decline extent of responsivity would be also increased. Judging from the ablation, crack and fold zone on the surface of PIN photodiode after the laser irradiation, the damage was for thermal stress effect. The continuity of material confined its free expansion. Therefore, the uneven thermal expansion induced the great thermal stress. At the same time, the silicon transited from brittle to ductile and the yield strength dramatically decreased. Once the maximum thermal stress exceeded the critical stress, the plastic deformation and the brittle cracks of silicon would be generated. With the increase of laser energy, the thermal stress damage extent of PIN photodiode would be also increased accordingly and the black area of laser ablation would be

  2. Laser beam welding of any metal.

    SciTech Connect

    Leong, K. H.

    1998-10-01

    The effect of a metal's thermophysical properties on its weldability are examined. The thermal conductivity, melting point, absorptivity and thermal diffusivity of the metal and the laser beam focused diameter and welding speed influence the minimum beam irradiance required for melting and welding. Beam diameter, surface tension and viscosity of the molten metal affect weld pool stability and weld quality. Lower surface tension and viscosity increases weld pool instability. With larger beam diameters causing wider welds, dropout also increases. Effects of focused beam diameter and joint fitup on weldability are also examined. Small beam diameters are sensitive to beam coupling problems in relation to fitup precision in addition to beam alignment to the seam. Welding parameters for mitigating weld pool instability and increasing weld quality are derived from the above considerations. Guidelines are presented for the tailoring of welding parameters to achieve good welds. Weldability problems can also be anticipated from the properties of a metal.

  3. Pulsed laser deposition and characterization of ZnO nanopores

    NASA Astrophysics Data System (ADS)

    Ghosh, Poulami; Sharma, Ashwini K.

    2016-04-01

    We report on the deposition and characterization of ZnO nanopore structures by pulsed laser deposition technique at a fixed substrate temperature and at different deposition times on a silicon (100) substrate. X-ray diffraction shows that ZnO nanopore structures are highly oriented along c-axis. Morphological analysis of the nanostructures studied by FESEM and AFM confirms the pores nature of the structures. The morphological evolution of the nanostructures as a function of deposition time is discussed on the basis of Stranski-Krastanov growth model. Optical properties of the nanostructures studied by photoluminescence spectra indicate that the observed transitions are from near band edge as well as from defect-related states.

  4. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    SciTech Connect

    Brendel', V M; Bukin, V V; Garnov, Sergei V; Bagdasarov, V Kh; Denisov, N N; Garanin, Sergey G; Terekhin, V A; Trutnev, Yurii A

    2012-12-31

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation. (laser technologies)

  5. Optodynamic aspect of a pulsed laser ablation process

    NASA Astrophysics Data System (ADS)

    Hrovatin, Rok; Možina, Janez

    1995-02-01

    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.

  6. Antimicrobial nanospheres thin coatings prepared by advanced pulsed laser technique

    PubMed Central

    Holban, Alina Maria; Grumezescu, Valentina; Vasile, Bogdan Ştefan; Truşcă, Roxana; Cristescu, Rodica; Socol, Gabriel; Iordache, Florin

    2014-01-01

    Summary We report on the fabrication of thin coatings based on polylactic acid-chitosan-magnetite-eugenol (PLA-CS-Fe3O4@EUG) nanospheres by matrix assisted pulsed laser evaporation (MAPLE). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) investigation proved that the homogenous Fe3O4@EUG nanoparticles have an average diameter of about 7 nm, while the PLA-CS-Fe3O4@EUG nanospheres diameter sizes range between 20 and 80 nm. These MAPLE-deposited coatings acted as bioactive nanosystems and exhibited a great antimicrobial effect by impairing the adherence and biofilm formation of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria strains. Moreover, the obtained nano-coatings showed a good biocompatibility and facilitated the normal development of human endothelial cells. These nanosystems may be used as efficient alternatives in treating and preventing bacterial infections. PMID:24991524

  7. Spatial filter pinhole for high-energy pulsed lasers.

    PubMed

    Celliers, P M; Estabrook, K G; Wallace, R J; Murray, J E; Da Silva, L B; Macgowan, B J; Van Wonterghem, B M; Manes, K R

    1998-04-20

    Spatial filters are essential components for maintaining high beam quality in high-energy pulsed laser systems. The long-duration (21 ns) high-energy pulses envisioned for future inertial-confinement fusion drive systems, such as the U.S. National Ignition Facility (NIF), are likely to lead to increased plasma generation and closure effects within the pinholes in the spatial filters. The design goal for the pinhole spatial filter for the NIF design is to remove small-angle scatter in the beam to as little as a ?100-murad divergence. It is uncertain whether this design requirement can be met with a conventional pinhole design. We propose a new pinhole architecture that addresses these issues by incorporating features intended to reduce the rate of plasma generation. Initial experiments with this design have verified its performance improvement relative to a conventional pinhole design. PMID:18273166

  8. Stimulated brillouin backscatter of a short-pulse laser

    SciTech Connect

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-11-03

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x{prime} = x {minus} V{sub g}t, t{prime} = t, where V{sub g} is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency).

  9. Pulsed laser deposition of anatase thin films on textile substrates

    NASA Astrophysics Data System (ADS)

    Krämer, André; Kunz, Clemens; Gräf, Stephan; Müller, Frank A.

    2015-10-01

    Pulsed laser deposition (PLD) is a highly versatile tool to prepare functional thin film coatings. In our study we utilised a Q-switched CO2 laser with a pulse duration τ ≈ 300 ns, a laser wavelength λ = 10.59 μm, a repetition frequency frep = 800 Hz and a peak power Ppeak = 15 kW to deposit crystalline anatase thin films on carbon fibre fabrics. For this purpose, preparatory experiments were performed on silicon substrates to optimise the anatase deposition conditions including the influence of different substrate temperatures and oxygen partial pressures. Processing parameters were then transferred to deposit anatase on carbon fibres. Scanning electron microscopy, X-ray diffraction analyses, Raman spectroscopy and tactile profilometry were used to characterise the samples and to reveal the formation of phase pure anatase without the occurrence of a secondary rutile phase. Methanol conversion test were used to prove the photocatalytic activity of the coated carbon fibres.

  10. Thermochromic VO2 on Zinnwaldite Mica by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Mathevula, L.; Ngom, B. D.; Kotsedi, L.; Sechogela, P.; Doyle, T. B.; Ghouti, M.; Maaza, M.

    2014-09-01

    VO2 thin films have been deposited by pulsed laser deposition on Zinnwaldite Mica substrates. The crystal structure, chemical composition, morphology were determined and the semiconductor/metal transition (SMT) properties of the deposited films were investigated. Without any post annealing, the films exhibit a textured nature with a VO2 (0 1 1) preferred crystallographic orientation and an elevated thermal variation of the electric resistance ratio RS/RM through the SMT at T ≈ 68 °C of the order of 104 and a narrow ∼7 °C hysteresis. In addition, the growth of the VO2 crystallites seem to be governed likely by a Volmer-Weber or Stranski-Krastanov mechanisms and certainly not a Frank-van Der Merwe process.

  11. Luminescent graphene quantum dots fabricated by pulsed laser synthesis

    PubMed Central

    Habiba, Khaled; Makarov, Vladimir I.; Avalos, Javier; Guinel, Maxime J.F.; Weiner, Brad R.; Morell, Gerardo

    2016-01-01

    Graphene has been the subject of intense research in recent years due to its unique electrical, optical and mechanical properties. Furthermore, it is expected that quantum dots of graphene would make their way into devices due to their structure and composition which unify graphene and quantum dots properties. Graphene quantum dots (GQDs) are planar nano flakes with a few atomic layers thick and with a higher surface-to-volume ratio than spherical carbon dots (CDs) of the same size. We have developed a pulsed laser synthesis (PLS) method for the synthesis of GQDs that are soluble in water, measure 2–6 nm across, and are about 1–3 layers thick. They show strong intrinsic fluorescence in the visible region. The source of fluorescence can be attributed to various factors, such as: quantum confinement, zigzag edge structure, and surface defects. Confocal microscopy images of bacteria exposed to GQDs show their suitability as biomarkers and nano-probes in high contrast bioimaging.

  12. Pulsed laser deposition and characterization of cellulase thin films

    NASA Astrophysics Data System (ADS)

    Cicco, N.; Morone, A.; Verrastro, M.; Viggiano, V.

    2013-08-01

    Thin films of cellulase were obtained by pulsed laser deposition (PLD) on an appropriate substrate. Glycoside hydrolase cellulase has received our attention because it emerges among the antifouling enzymes (enzymes being able to remove and prevent the formation of micro-organism biofilms) used in industry and medicine field. Pressed cellulase pellets, used as target material, were ablated with pulses of a Nd-YAG laser working at wavelength of 532 nm. In this work, we evaluated the impact of PLD technique both on molecular structure and hydrolytic activity of cellulase. Characteristic chemical bonds and morphology of deposited layers were investigated by FTIR spectroscopy and SEM respectively. The hydrolytic activity of cellulase thin films was detected by a colorimetric assay.

  13. Magnetotransport in Pulsed Laser Deposited Manganese Doped Lead Sulfide Films

    NASA Astrophysics Data System (ADS)

    Rimal, Gaurab; Sapkota, Keshab; Maksymov, Artur; Spinu, Leonard; Wang, Wenyong; Tang, Jinke

    Diluted magnetic semiconductors (DMS) have been proposed as promising candidates for spintronic applications. Most research in this field has been confined to III-V and II-VI semiconductor system. There are reports on IV-VI semiconductors, however reports on lead sulfide (PbS) based DMS is limited. We study the transport, magnetic and structural properties of manganese doped lead sulfide (Mn:PbS) films produced by pulsed laser deposition (PLD). The films are found to show hopping transport at low tempeature. Low temperature magnetoresistance (MR) studies show that the sign of MR can be changed by application of gate voltage. The magnetic properties of the films were also studied which showed ferromagnetic behavior at room temperature.

  14. Ultra-short Pulse Laser Structuring of Molding Tools

    NASA Astrophysics Data System (ADS)

    Conrad, Daniel; Richter, Lars

    The machining of highly filled abrasive polymer plastics in injection molding processes determines high resistant tools in the industrial production. One of the most important points is a long durability of the molding tools to reduce the costs of production. Thus, the adhesion force and abrasion will be reduced with the help of defined surface properties. To achieve appropriate surface conditions, an ultra-short pulse laser is used for a micro structuring. Additional a laser polishing of the micro-structured surfaces to optimize the frictional properties is presented. This paper shows the research results of investigations on the laser modification of steel surfaces, to generate high-quality and wear-resistant surfaces for injection molding tools.

  15. Testing of a femtosecond pulse laser in outer space

    PubMed Central

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo

    2014-01-01

    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future. PMID:24875665

  16. Thin nanocrystalline zirconia films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Dikovska, A. Og; Atanasova, G. B.; Avdeev, G. V.; Strijkova, V. Y.

    2016-03-01

    In the present work, thin zirconia films were prepared by pulsed laser deposition at different substrate temperatures and oxygen partial pressures. The substrate temperature was varied from 400 °C to 600 °C, and the oxygen pressure, from 0.01 to 0.05 mbar. The effect was investigated of the substrate temperature and oxygen pressure on the formation of m-zirconia and t-zirconia phases.The formation of a cubic phase of ZrO2 by using targets doped with 3 and 8 mol % content Y2O3 was also investigated. The variation in the optical properties was studied and discussed in relation with the zirconia films' microstructure.

  17. Pulsed laser linescanner for a backscatter absorption gas imaging system

    DOEpatents

    Kulp, Thomas J.; Reichardt, Thomas A.; Schmitt, Randal L.; Bambha, Ray P.

    2004-02-10

    An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle.

  18. Precision ablation of dental enamel using a subpicosecond pulsed laser.

    PubMed

    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

    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

  19. Monitoring interfacial dynamics by pulsed laser techniques. Final report

    SciTech Connect

    Richmond, G.

    1995-12-31

    The research is aimed at understanding the structural, electronic, and reactive properties of semiconductors in solutions. Focus is on Si and GaAs surfaces because they are used in photovoltaic devices, etc. The pulsed laser techniques used included surface second harmonic generation in Si and laser induced photoluminescence in GaAs. SHG can measure space charge effects in the semiconductor under various conditions, ie, immersed in electrolyte, in presence of oxide overlayers, and under UHV conditions. The Si studies demonstrated the sensitivity of the phase of the SH response to space charge effects. With GaAs, time-correlated single photon counting methods were used in the picosecond time regime to examine the recombination luminescence following above band gap excitation (surface trapping velocities).

  20. Soft X-Ray Optics by Pulsed Laser Deposition

    NASA Technical Reports Server (NTRS)

    Fernandez, Felix E.

    1996-01-01

    Mo/Si and C/Co multilayers for soft x-ray optics were designed for spectral regions of interest in possible applications. Fabrication was effected by Pulsed Laser Deposition using Nd:YAG (355 nm) or excimer (248 nm) lasers in order to evaluate the suitability of this technique. Results for Mo/Si structures were not considered satisfactory due mainly to problems with particulate production and target surface modification during Si ablation. These problems may be alleviated by a two-wavelength approach, using separate lasers for each target. Results for C/Co multilayers are much more encouraging, since indication of good layering was observed for extremely thin layers. We expect to continue investigating this possibility. In order to compete with traditional PVD techniques, it is necessary to achieve film coverage uniformity over large enough areas. It was shown that this is feasible, and novel means of achieving it were devised.

  1. History and current status of commercial pulsed laser deposition equipment

    NASA Astrophysics Data System (ADS)

    Greer, James A.

    2014-01-01

    This paper will review the history of the scale-up of the pulsed laser deposition (PLD) process from small areas ∼1 cm2 up to 10 m2 starting in about 1987. It also documents the history of commercialization of PLD as various companies become involved in selling fully integrated laser deposition tools starting in 1989. The paper will highlight the current state of the art of commercial PLD equipment for R&D that is available on the market today from mainstream vendors as well as production-oriented applications directed at piezo-electric materials for microelectromechanical systems and high-temperature superconductors for coated-conductor applications. The paper clearly demonstrates that considerable improvements have been made to scaling this unique physical vapour deposition process to useful substrate sizes, and that commercial deposition equipment is readily available from a variety of vendors to address a wide variety of technologically important thin-film applications.

  2. Formation of ultrasmooth thin silver films by pulsed laser deposition

    SciTech Connect

    Kuznetsov, I. A.; Garaeva, M. Ya.; Mamichev, D. A. Grishchenko, Yu. V.; Zanaveskin, M. L.

    2013-09-15

    Ultrasmooth thin silver films have been formed on a quartz substrate with a buffer yttrium oxide layer by pulsed laser deposition. The dependence of the surface morphology of the film on the gas (N{sub 2}) pressure in the working chamber and laser pulse energy is investigated. It is found that the conditions of film growth are optimal at a gas pressure of 10{sup -2} Torr and lowest pulse energy. The silver films formed under these conditions on a quartz substrate with an initial surface roughness of 0.3 nm had a surface roughness of 0.36 nm. These films can be used as a basis for various optoelectronics and nanoplasmonics elements.

  3. Epitaxial Electronic Oxides on Semiconductors Using Pulsed-Laser Deposition

    SciTech Connect

    Norton, D.P.; Budai, J.D.; Chisholm, M.F.

    1999-12-01

    We describe the growth and properties of epitaxial (OO1) CeO{sub 2} on a (001) Ge surface using a hydrogen-assisted pulsed-laser deposition method. Hydrogen gas is introduced during film growth to eliminate the presence of the GeOs from the semiconductor surface during the initial nucleation of the metal oxide film. The hydrogen partial pressure and substrate temperature are selected to be sufficiently high such that the germanium native oxides are thermodynamically unstable. The Gibbs free energy of CeO{sub 2} is larger in magnitude than that of the Ge native oxides, making it more favorable for the metal oxide to reside at the interface in comparison to the native Ge oxides. By satisfying these criteria. the metal oxide/semiconductor interface is shown to be atomically abrupt with no native oxide present. Preliminary structural and electrical properties are reported.

  4. Heteroepitaxial Growth of NSMO on Silicon by Pulsed Laser Deposition

    SciTech Connect

    Kolagani, R; Friedrich, S

    2008-06-25

    The following is the optimized pulsed laser deposition (PLD) procedure by which we prepared the final samples that were sent to LLNL. These samples are epitaxial multilayer structures of Si/YSZ/CeO/NSMO, where the abbreviations are explained in the following table. In this heterostructure, YSZ serves as a buffer layer to prevent deleterious chemical reactions, and also serves to de-oxygenate the amorphous SiO{sub 2} layer to generate a crystalline template for epitaxy. CeO and BTO serve as template layers to minimize the effects of thermal and lattice mismatch strains, respectively. More details on the buffer and template layer scheme are included in the manuscript [Yong et al., 2008] attached to this report.

  5. Pulsed laser deposition of amorphous carbon/silver nanocomposites

    NASA Astrophysics Data System (ADS)

    Matenoglou, G.; Evangelakis, G. A.; Kosmidis, C.; Foulias, S.; Papadimitriou, D.; Patsalas, P.

    2007-07-01

    Metal/amorphous carbon (a-C:M) composite films are emerging as a category of very important engineering materials for surface protection. We implement pulsed laser deposition (PLD) to grow pure a-C and a-C:Ag nanocomposites. Our PLD process is assisted by a static electric field. We investigate the structural features of the a-C:Ag nanocomposites and the bonding configuration of the a-C matrix with respect to the electric field and the composition of the PLD target. For this study we use Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and X-ray diffraction (XRD). We show that the Ag mean grain size and the sp 2 content of the a-C matrix are increasing with increasing Ag content in the films.

  6. Surface temperature transients from pulsed laser heating of UO 2

    NASA Astrophysics Data System (ADS)

    Yagnik, S. K.; Olander, D. R.

    1988-07-01

    Surface heating of UO 2 by a pulsed laser was investigated theoretically and experimentally. Targets of solid uranium dioxide in vacuum were rapidly heated to peak temperatures of 3700 K, as measured by a fast-response automatic optical pyrometer. The measured target surface temperatures were compared with a one-dimensional heat transport model that accounts for conduction and melting in the solid and ablation and radiation from the surface. Congruent vaporization of UO 2 was assumed. The measured temporal and spatial characteristics of the laser beam as well as temperature-dependent physical and thermodynamic properties of UO 2 are used as input to the calculations. Agreement of the theory with the measurements was further validated by post-irradiation microscopic examination of the target surface. Additional tests were performed to assess qualitatively the attenuation of laser light and thermal radiation from the surface by the vapor blow-off from the target. This effect was found to be insignificant.

  7. Response of silicon solar cell to pulsed laser illumination

    NASA Technical Reports Server (NTRS)

    Willowby, D.; Alexander, D.; Edge, T.; Herren, K.

    1993-01-01

    The response of silicon solar cell(s) to pulsed laser illumination is discussed. The motivation was due to the interest of Earth to space/Moon power beaming applications. When this work began, it was not known if solar cells would respond to laser light with pulse lengths in the nanosecond range and a repetition frequency in the kHz range. This is because the laser pulse would be shorter than the minority carrier lifetime of silicon. A 20-nanosecond (ns) full width half max (FWHM) pulse from an aluminum-gallium/arsenide (Al-Ga-As) diode laser was used to illuminate silicon solar cells at a wavelength of 885 nanometers (nm). Using a high-speed digital oscilloscope, the response of the solar cells to individual pulses across various resistive loads was observed and recorded.

  8. Testing of a femtosecond pulse laser in outer space

    NASA Astrophysics Data System (ADS)

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo

    2014-05-01

    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future.

  9. Experimental investigation of a unique airbreathing pulsed laser propulsion concept

    NASA Technical Reports Server (NTRS)

    Myrabo, L. N.; Nagamatsu, H. T.; Manka, C.; Lyons, P. W.; Jones, R. A.

    1991-01-01

    Investigations were conducted into unique methods of converting pulsed laser energy into propulsive thrust across a flat impulse surface under atmospheric conditions. The propulsion experiments were performed with a 1-micron neodymium-glass laser at the Space Plasma Branch of the Naval Research Laboratory. Laser-induced impulse was measured dynamically by ballistic pendulums and statically using piezoelectric pressure transducers on a stationary impulse surface. The principal goal was to explore methods for increasing the impulse coupling performance of airbreathing laser-propulsion engines. A magnetohydrodynamic thrust augmentation effect was discovered when a tesla-level magnetic field was applied perpendicular to the impulse surface. The impulse coupling coefficient performance doubled and continued to improve with increasing laser-pulse energies. The resultant performance of 180 to 200 N-s/MJ was found to be comparable to that of the earliest afterburning turbojets.

  10. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Brendel', V. M.; Bukin, V. V.; Garnov, Sergei V.; Bagdasarov, V. Kh; Denisov, N. N.; Garanin, Sergey G.; Terekhin, V. A.; Trutnev, Yurii A.

    2012-12-01

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation.

  11. Model of Layered Weld Formation Under Narrow Gap Pulse Welding

    NASA Astrophysics Data System (ADS)

    Krampit, A. G.

    2016-04-01

    The model parameters of narrow gap pulse welding can be divided into input, internal and output ones. The breadth of gap, that is, clearance breadth between upright edges is one of key parameters securing high quality of a weld joint. The paper presents theoretical outcomes for the model of layered weld formation under narrow gap pulse welding. Based on these studies is developed model of processes, which occur in the weld pool under pulse grove welding. It comprises the scheme of liquid metal motion in the weld pool, scheme of fusion with the side edge and in the bottom part, and the scheme of welding current impulse effect on the structure of a weld joint.

  12. Fluid Flow Phenomena during Welding

    SciTech Connect

    Zhang, Wei

    2011-01-01

    MOLTEN WELD POOLS are dynamic. Liquid in the weld pool in acted on by several strong forces, which can result in high-velocity fluid motion. Fluid flow velocities exceeding 1 m/s (3.3 ft/s) have been observed in gas tungsten arc (GTA) welds under ordinary welding conditions, and higher velocities have been measured in submerged arc welds. Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects. Moving liquid transports heat and often dominates heat transport in the weld pool. Because heat transport by mass flow depends on the direction and speed of fluid motion, weld pool shape can differ dramatically from that predicted by conductive heat flow. Temperature gradients are also altered by fluid flow, which can affect weld microstructure. A number of defects in GTA welds have been attributed to fluid flow or changes in fluid flow, including lack of penetration, top bead roughness, humped beads, finger penetration, and undercutting. Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds.

  13. Pulse laser processing of metal thin films on glass substrates

    NASA Astrophysics Data System (ADS)

    Mikheev, Gennady M.; Zonov, Ruslan G.; Kaluzhny, Dmitry G.

    2004-04-01

    The possibility of the pulse laser radiation treatment of thin metal films on glass substrates has been studied experimentally. On the glass substrates with sprayed coating the diffraction structures were obtained due to the selective evaporation of metal at the interference of the powerful pulse laser radiation. The experiments were conducted using copper, aluminum films and films from titanium oxides. The thickness of the films on the glass substrates was 0.1 - 0.12 μm. The regimes normally used during the film treatment with a laser beam were as follows: the wavelength was 1.06 μm, the pulse duration was 10 ns, and the enegy density of the beam was 10 mJ/mm2. To obtain an interference pattern on the treated surface the beam of the coherent radiation was preliminary split into two. In dependence on the convergence angle of the interference beams, the diffraction gratings had the lattice spacing in the range of 1 - 6 μm. They were used to produce diffraction lenses. These lenses are a plane device with a ring-shape zone of concentric grating grooves capable to focus a certain part of incident radiation. In dependence on the wavelength, the radiation is collected on the optic axis at different distances from the diffraction lens. This fact makes it possible to use the lens in production of a simple monochromator. The structure of the diffraction gratings obtained has been studied, and their main characteristics and main spheres of their application have been determined.

  14. Tempering rapidly solidified ductile cast iron by pulsed laser beam reprocessing

    SciTech Connect

    Wang, H.M. . Dept. of Materials Science and Engineering); Bergmann, H.W. . Materials Science Dept.)

    1994-08-15

    During laser surface rapid remelting of cast irons, the melt pool solidifies rapidly and metastably (i.e. according to the metastable Fe-Fe[sub 3]C system) producing an ultra-fine ledeburite hard surface which is much more abrasion resistant than the original substrate. Previous literature mainly focused on remelting various grey and ductile irons with high power CO[sub 2] lasers for improved wear resistance and other surface properties, and on studying the physical metallurgy of laser remelted surfaces. Unfortunately, the unstable nature and rapid tempering behavior of the rapidly solidified ledeburite were generally neglected, although some publications mentioned the tempering phenomenon during successive overlap remelting. In this paper, a laser remelted ductile case iron surface was tempered by rapid pulsed laser beam reprocessing. The rapidly solidified ductile iron was found to be rapidly graphitized, as a result, a layer of Fe-base alloy containing ultra-fine graphite particles was produced. The unusual rapid graphitization phenomenon was preliminarily discussed.

  15. Pulsed laser-induced evaporation of liquids and its applications

    NASA Astrophysics Data System (ADS)

    Kim, Dongsik

    The interaction of laser irradiation with materials is very important in a variety of laser-based manufacturing processes and scientific studies. Particularly, the interaction of a short laser pulse with absorbing liquids or solid materials in contact with liquid is central to a number of applications, including laser cleaning of microcontaminants, pulsed laser deposition of thin film materials, laser tissue removal, and laser surface texturing. In this dissertation, experimental and theoretical works on the following topics are summarized: (1) physical mechanisms of pulsed laser induced ablation of absorbing liquids at laser fluence below the plasma ignition threshold, (2) analysis of rapid vaporization at the absorbing solid/transparent liquid interface, (3) laser cleaning of surface contaminates. Concerning the first topic, the near-threshold ablation process at low laser fluences and the high power explosive vaporization process accompanying subsequent ablation plume dynamics are elucidated. Acoustic-wave detection by a piezoelectric pressure transducer, visualization by laser flash photography, and optical reflection/transmission measurements are carried out for the in-situ diagnosis of the process. Quantification of the acoustic-field generation and detection of the bubble-nucleation dynamics in the rapid vaporization at the solid liquid interface are performed by photoacoustic beam deflection technique and optical interferometry, respectively. Finally, experiments are carried out for the development of a practical laser cleaning tool and the analysis of the contaminant-removal mechanism. The results show that the near-threshold ablation by a short laser pulse is initiated by the tensile component of the thermoelastic stress without significant increase of liquid temperature at low laser fluences. On the other hand, if the heating rate is rapid enough to achieve high degree of superheating of the liquid, explosive vaporization takes place due to the abrupt

  16. The effect of welding parameters on penetration in GTA welds

    SciTech Connect

    Shirali, A.A. ); Mills, K.C. )

    1993-07-01

    The effect of various welding parameters on the penetration of GTA welds has been investigated. Increases in welding speed were found to reduce penetration; however, increases in welding current were observed to increase the penetration in high sulfur (HS) casts and decrease penetration in low sulfur (LS) steels. Plots of penetration as a function of increasing linear energy (the heat supplied per unit length of weld) revealed a similar trend with increased penetration in HS casts, but the penetration in LS casts was unaffected by increases in linear energy. These results support the Burgardt-Heiple proposition that changes in welding parameters on penetration can be explained in terms of their effect, sequentially, on the temperature gradient and the Marangoni forces operating in the weld pool. Increases in arc length were found to decrease weld penetration regardless of the sulfur concentration of the steel, and the effects of electrode geometry and welding position on weld penetration were also investigated.

  17. Welding Behavior of Free Machining Stainless Steel

    SciTech Connect

    BROOKS,JOHN A.; ROBINO,CHARLES V.; HEADLEY,THOMAS J.; MICHAEL,JOSEPH R.

    2000-07-24

    The weld solidification and cracking behavior of sulfur bearing free machining austenitic stainless steel was investigated for both gas-tungsten arc (GTA) and pulsed laser beam weld processes. The GTA weld solidification was consistent with those predicted with existing solidification diagrams and the cracking response was controlled primarily by solidification mode. The solidification behavior of the pulsed laser welds was complex, and often contained regions of primary ferrite and primary austenite solidification, although in all cases the welds were found to be completely austenite at room temperature. Electron backscattered diffraction (EBSD) pattern analysis indicated that the nature of the base metal at the time of solidification plays a primary role in initial solidification. The solid state transformation of austenite to ferrite at the fusion zone boundary, and ferrite to austenite on cooling may both be massive in nature. A range of alloy compositions that exhibited good resistance to solidification cracking and was compatible with both welding processes was identified. The compositional range is bounded by laser weldability at lower Cr{sub eq}/Ni{sub eq} ratios and by the GTA weldability at higher ratios. It was found with both processes that the limiting ratios were somewhat dependent upon sulfur content.

  18. Infrared antireflection DLC films by femtosecond pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Wang, Shuyun; Guo, Yanlong; Wang, Xiaobing; Cheng, Yong; Wang, Huisheng; Liu, Xu

    2009-05-01

    Diamond-like Carbon(DLC) films are deposited by Ti:Sapphire femtosecond pulsed laser(800nm, 120fs-2ps, 3.3W, 1-1000Hz) at room temperature. The substrate is n-type Si(100), and the target is 99.999%-purity graphite. After a great lot of experiments, optimal technical parameters, which are 1000Hz repetition frequency, 120fs pulse-width, 5cm-distance between target and underlay and 1014W/cm2 power-density, were used to deposite 443nm thick DLC film. Raman spectrum measurement shows a broad peak with a center at 1550 cm-1 for all films, similar to those of typical diamond-like carbon films prepared using other methods. And sp3-bond content reaches 67% analyzed by XPS. There is no nick on the film when scraped 105 times by a RS-5600 friction test machine under the pressure of 9.8N. The infrared transmittance increases along with the oxygen pressure when between 0.03 Pa and 2 Pa. The result shows that oxygen is effective in etching sp2-bond content. The extreme infrared transmittance of Si slice deposited DLC film on single surface is higher than 64% at 3-5μm, superior to 53% when being uncoated.

  19. Drastic deviations from stoichiometry transfer during pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Dittrich, Arne; Eberl, Christian; Schlenkrich, Susanne; Schlenkrich, Felix; Döring, Florian; Krebs, Hans-Ulrich

    2016-04-01

    In common, one of the most characteristic properties of pulsed laser deposition is the stoichiometry transfer between target and substrate, which has been used heavily for many complex systems. In this paper we show that it is yet possible to obtain drastic deviations from stoichiometry transfer in a binary system by just varying the fluence during laser deposition. In the W-Cu system, the W concentration of films grown from a composite W60Cu40 target (60 wt% W) was indeed continuously changed over an unprecedented large range of 0-70 wt% W. Close to the deposition threshold, pure Cu films are formed due to the much higher vapor pressure of Cu. At higher laser fluences, more and more W-rich W-Cu alloy samples are obtained, since ion implantation and intermixing processes occur. These alloys can reach W contents even higher than that of the target because of enhanced resputtering and reflection of the lighter Cu atoms at the film surface. Stoichiometric films with 60 wt% of W are only obtained at laser fluences around 2.7 J/cm2, when the strong Cu evaporation from the target and reflection and resputtering effects of Cu at the film surface are in balance.

  20. Pulsed Laser Synthesized Magnetic Cobalt Oxide Nanoparticles for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Bhatta, Hari; Gupta, Ram; Ghosh, Kartik; Kahol, Pawan; Delong, Robert; Wanekawa, Adam

    2011-03-01

    Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Biocompatible and chemically stable magnetic metal oxide nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication of magnetic cobalt oxide nanoparticles using a safe, cost effective, and easy to handle technique that is capable of producing nanoparticles free of any contamination. Cobalt oxide nanoparticles have been synthesized at room temperature using cobalt foil by pulsed laser ablation technique. These cobalt oxide nanoparticles were characterized using UV-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and dynamic laser light scattering (DLLS). The magnetic cobalt oxides nanoparticles were stabilized in glucose solutions of various concentrations in deionized water. The presence of UV-Vis absorption peak at 270 nm validates the nature of cobalt oxide nanoparticles. The DLLS size distributions of nanoparticles are in the range of 110 to 300 nm, which further confirms the presence nanoparticles. This work is partially supported by National Science Foundation (DMR- 0907037).

  1. Novel doped hydroxyapatite thin films obtained by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Duta, L.; Oktar, F. N.; Stan, G. E.; Popescu-Pelin, G.; Serban, N.; Luculescu, C.; Mihailescu, I. N.

    2013-01-01

    We report on the synthesis of novel ovine and bovine derived hydroxyapatite thin films on titanium substrates by pulsed laser deposition for a new generation of implants. The calcination treatment applied to produce the hydroxyapatite powders from ovine/bovine bones was intended to induce crystallization and to prohibit the transmission of diseases. The deposited films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Pull-off adherence and profilometry measurements were also carried out. X-ray diffraction ascertained the polycrystalline hydroxyapatite nature of the powders and films. Fourier transform infrared spectroscopy evidenced the vibrational bands characteristic to a hydroxyapatite material slightly carbonated. The micrographs of the films showed a uniform distribution of spheroidal particulates with a mean diameter of ∼2 μm. Pull-off measurements demonstrated excellent bonding strength values between the hydroxyapatite films and the titanium substrates. Because of their physical-chemical properties and low cost fabrication from renewable resources, we think that these new coating materials could be considered as a prospective competitor to synthetic hydroxyapatite used for implantology applications.

  2. Clutter discrimination algorithm simulation in pulse laser radar imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-mei; Li, Huan; Guo, Hai-chao; Su, Xuan; Zhu, Fule

    2015-10-01

    Pulse laser radar imaging performance is greatly influenced by different kinds of clutter. Various algorithms are developed to mitigate clutter. However, estimating performance of a new algorithm is difficult. Here, a simulation model for estimating clutter discrimination algorithms is presented. This model consists of laser pulse emission, clutter jamming, laser pulse reception and target image producing. Additionally, a hardware platform is set up gathering clutter data reflected by ground and trees. The data logging is as clutter jamming input in the simulation model. The hardware platform includes a laser diode, a laser detector and a high sample rate data logging circuit. The laser diode transmits short laser pulses (40ns FWHM) at 12.5 kilohertz pulse rate and at 905nm wavelength. An analog-to-digital converter chip integrated in the sample circuit works at 250 mega samples per second. The simulation model and the hardware platform contribute to a clutter discrimination algorithm simulation system. Using this system, after analyzing clutter data logging, a new compound pulse detection algorithm is developed. This new algorithm combines matched filter algorithm and constant fraction discrimination (CFD) algorithm. Firstly, laser echo pulse signal is processed by matched filter algorithm. After the first step, CFD algorithm comes next. Finally, clutter jamming from ground and trees is discriminated and target image is produced. Laser radar images are simulated using CFD algorithm, matched filter algorithm and the new algorithm respectively. Simulation result demonstrates that the new algorithm achieves the best target imaging effect of mitigating clutter reflected by ground and trees.

  3. Selective gold nanoparticles formation by pulsed laser interference

    NASA Astrophysics Data System (ADS)

    Peláez, R. J.; Baraldi, G.; Afonso, C. N.; Riedel, S.; Boneberg, J.; Leiderer, P.

    2012-09-01

    Discontinuous Au films are prepared on glass substrates by pulsed laser deposition with two different metal coverages that lead to a film being formed by irregular coalesced nanoparticles (NPs) and to another film close to the percolation limit. The films are exposed to three interfering beams at different intensities produced by the fourth harmonic of a Nd:YAG laser (266 nm, 10 ns). Scanning electron microscopy and extinction spectra are used respectively to study the structural and optical properties before and after the laser structuring. Round metal NPs appear in the laser transformed areas due to melting followed by rapid solidification that is reflected in the extinction spectra by the appearance of a surface plasmon resonance around 530-540 nm. The areas with NPs are surrounded by non-transformed areas forming a periodic pattern that evolves from a 2D array to parallel lines when local laser intensity increases to cover the whole sample at high intensity. The accumulation of several pulses at low fluence can also transform the metal film almost completely by creating alternating areas having different NP dimensions. The accumulation of metal in some areas of the pattern is consistent with mass transport towards the lower temperature regions.

  4. Modeling pulsed-laser melting of embedded semiconductor nanoparticles

    SciTech Connect

    Sawyer, C.A.; Guzman, J.; Boswell-Koller, C.N.; Sherburne, M.P.; Mastandrea, J.P.; Bustillo, K.C.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2011-05-18

    Pulsed-laser melting (PLM) is commonly used to achieve a fast quench rate in both thin films and nanoparticles. A model for the size evolution during PLM of nanoparticles confined in a transparent matrix, such as those created by ion-beam synthesis, is presented. A self-consistent mean-field rate equations approach that has been used successfully to model ion beam synthesis of germanium nanoparticles in silica is extended to include the PLM process. The PLM model includes classical optical absorption, multiscale heat transport by both analytical and finite difference methods, and melting kinetics for confined nanoparticles. The treatment of nucleation and coarsening behavior developed for the ion beam synthesis model is modified to allow for a non-uniform temperature gradient and for interacting liquid and solid particles with different properties. The model allows prediction of the particle size distribution after PLM under various laser fluences, starting from any particle size distribution including as-implanted or annealed simulated samples. A route for narrowing the size distribution of embedded nanoparticles is suggested, with simulated distribution widths as low as 15% of the average size.

  5. Laser Doppler and Pulsed Laser Velocimetry in Fluid Mechanics

    NASA Astrophysics Data System (ADS)

    Coupland, Jeremy M.

    Since the introduction of the laser in the late 1960s, optical metrology has made a major impact in many branches of engineering. This is nowhere more apparent than in the field of fluid mechanics where laser technology has revolutionised the way in which fluid flows are studied. The light scattered from small seeding particles following the flow contains information relating to the particle position and velocity. The coherence characteristics and high power densities achievable with a laser source allow well-defined regions of flow to be investigated in a largely non-intrusive manner and on a spatial and temporal scale commensurate with he flow field of interest. This review outlines the laser-based methods of velocimetry that are now available to the fluid dynamicist and discusses their practical application. Laser Doppler velocimetry provides a means to produce time-resolved measurements of fluid velocity at a single point in the flow. The optical design of instruments of this type is addressed with reference to spatial resolution and light gathering performance. Typical Doppler signals produced at both high and low particle concentrations are analysed and signal processing techniques are briefly discussed. Pulsed laser velocimeters use imaging optics to record the position of seeding particles at two or more instants and provide information concerning the instantaneous structure of the flow field. The optical configurations and analysis procedures used for planar velocity measurements are described and whole-field three-dimensional velocity measurements using holographic techniques are introduced.

  6. Industrial beam delivery system for ultra-short pulsed laser

    NASA Astrophysics Data System (ADS)

    Funck, Max C.; Wedel, Björn; Kayander, Ilya; Niemeyer, Jörg

    2015-03-01

    Beam delivery systems are an integral part of industrial laser equipment. Separating laser source and application fiber optic beam delivery is employed wherever great flexibility is required. And today, fiber optic beam delivery of several kW average power is available for continuous wave operation using multimode step index fibers with core diameters of several 100 μm. However, during short-pulse or even ultra-short pulse laser operation step index fibers fail due to high power density levels and nonlinear effects such as self-focusing and induced scattering. Hollow core photonic crystal fibers (HC-PCF) are an alternative to traditional fibers featuring light propagation mostly inside a hollow core, enabling high power handling and drastically reduced nonlinear effects. These fibers have become available during the past decade and are used in research but also for fiber laser systems and exhibit a growing popularity. We report on using HC-PCF fibers and their integration into an industrial beam delivery package comparable to today's fiber optic standards and will discuss power handling, beam quality and efficiency as well as future prospects of this technology. In a preliminary industrial beam delivery setup 300 fs pulses at 100 W average power could be delivered.

  7. Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

    PubMed Central

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-01-01

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions. PMID:25645258

  8. Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors

    SciTech Connect

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

    2010-10-08

    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.

  9. Properties of pulsed laser deposited fluorinated hydroxyapatite films on titanium

    SciTech Connect

    Rau, J.V.; Smirnov, V.V.; Laureti, S.; Generosi, A.; Varvaro, G.; Fosca, M.; Ferro, D.; Cesaro, S. Nunziante; Albertini, V. Rossi; Barinov, S.M.

    2010-09-15

    Fluorinated hydroxyapatite coated titanium was investigated for application as implant coating for bone substitute materials in orthopaedics and dentistry. Pulsed laser deposition technique was used for films preparation. Fluorinated hydroxyapatite target composition, Ca{sub 10}(PO{sub 4}){sub 6}F{sub 1.37}(OH){sub 0.63}, was maintained at 2 J/cm{sup 2} of laser fluence and 500-600 {sup o}C of the substrate temperature. Prepared films had a compact microstructure, composed of spherical micrometric-size aggregates. The average surface roughness resulted to be of 3 nm for the film grown at 500 {sup o}C and of 10 nm for that grown at 600 {sup o}C, showing that the temperature increase did not favour the growth of a more fine granulated surface. The films were polycrystalline with no preferential growth orientation. The films grown at 500-600 {sup o}C were about 8 {mu}m thick and possessed a hardness of 12-13 GPa. Lower or higher substrate temperature provides the possibility to obtain coatings with different fine texture and roughness, thus tayloring them for various applications.

  10. Pulsed laser annealing of Be-implanted GaN

    SciTech Connect

    Wang, H.T.; Tan, L.S.; Chor, E.F.

    2005-11-01

    Postimplantation thermal processing of Be in molecular-beam-epitaxy-grown GaN by rapid thermal annealing (RTA) and pulsed laser annealing (PLA) was investigated. It has been found that the activation of Be dopants and the repair of implantation-induced defects in GaN films cannot be achieved efficiently by conventional RTA alone. On the other hand, good dopant activation and surface morphology and quality were obtained when the Be-implanted GaN film was annealed by PLA with a 248 nm KrF excimer laser. However, observations of off-resonant micro-Raman and high-resolution x-ray-diffraction spectra indicated that crystal defects and strain resulting from Be implantation were still existent after PLA, which probably degraded the carrier mobility and limited the activation efficiency to some extent. This can be attributed to the shallow penetration depth of the 248 nm laser in GaN, which only repaired the crystal defects in a thin near-surface layer, while the deeper defects were not annealed out well. This situation was significantly improved when the Be-implanted GaN was subjected to a combined process of PLA followed by RTA, which produced good activation of the dopants, good surface morphology, and repaired bulk and surface defects well.

  11. Power neodymium-glass amplifier of a repetitively pulsed laser

    SciTech Connect

    Vinogradov, Aleksandr V; Gaganov, V E; Garanin, Sergey G; Zhidkov, N V; Krotov, V A; Martynenko, S P; Pozdnyakov, E V; Solomatin, I I

    2011-11-30

    A neodymium-glass diode-pumped amplifier with a zigzag laser beam propagation through the active medium was elaborated; the amplifier is intended for operation in a repetitively pulsed laser. An amplifier unit with an aperture of 20 Multiplication-Sign 25 mm and a {approx}40-cm long active medium was put to a test. The energy of pump radiation amounts to 140 J at a wavelength of 806 nm for a pump duration of 550 {mu}s. The energy parameters of the amplifier were experimentally determined: the small-signal gain per pass {approx}3.2, the linear gain {approx}0.031 cm{sup -1} with a nonuniformity of its distribution over the aperture within 15%, the stored energy of 0.16 - 0.21 J cm{sup -3}. The wavefront distortions in the zigzag laser-beam propagation through the active element of the amplifier did not exceed 0.4{lambda} ({lambda} = 0.63 {mu}m is the probing radiation wavelength).

  12. Studies of a repetitively-pulsed laser powered thruster

    NASA Astrophysics Data System (ADS)

    Rosen, D. I.; Kemp, N. H.; Miller, M.

    1982-01-01

    In this report we present results of continuing analytical and experimental investigations carried out to evaluate the concept of pulsed laser propulsion. This advanced propulsion scheme, which has been the subject of several previous studies, involves supplying propellant energy by beaming short, repetitive laser pulses to a thruster from a remote laser power station. The concept offers the advantages of a remote power source, high specific impulse, high payload to total mass ratio (a consequence of the first two features) and moderate to high thrust (limited primarily by the average laser power available). The present research addresses questions related to thruster performance and optical design. In the thruster scheme under consideration, parabolic nozzle walls focus the incoming laser beam to yield breakdown in a propellant at the focal point of the parabola. The resulting high pressure plasma is characteristic of a detonation wave initiation by high power laser-induced breakdown. With a short laser pulse, the detonation wave quickly becomes a blast wave which propagates to the nozzle exit plane converting the high pressure of the gas behind it to a force on the nozzle wall. Propellant is fed to the focal region from a plenum chamber. The laser-induced blast wave stops the propellant flow through the throat until the pressure at the throat decays to the sonic pressure; then the propellant flow restarts. The process is repeated with each successive laser pulse.

  13. Effects of pulsed lasers on hard biological tissue

    NASA Astrophysics Data System (ADS)

    Jahn, Renate; Bleckmann, Andreas; Duczynski, Edwin W.; von der Heide, Hans-Joachim; Huber, Guenter; Jungbluth, Karl-Heinz; Lierse, Werner; Neu, Walter; Struve, Bert

    1993-07-01

    The interaction of various pulsed lasers with meniscus and bone of freshly slaughtered bovines and pigs was examined. Our aim was to find lasers useful for accident surgical operations (e.g. bone or callus dystopy inside joints or nearby important vessels or nerves after fractures). Laser wavelengths of the UV- and infrared spectral range were investigated: XeCl- excimer lasers (wavelength 308 nm, pulse duration 28 ns, 60 ns, 300 ns) Nd:YAG (1.06 micrometers , 400 microsecond(s) ), Tm:YAG (2.01 micrometers , 400 microsecond(s) ), Ho:YAG (2.12 micrometers , 400 microsecond(s) ), CrEr:YSGG (2.79 micrometers , 400 microsecond(s) ), and Er:YAG (2.94 micrometers , 400 microsecond(s) ). The excimer laser radiation was guided by a tapered fused silica fiber, whereas for all other lasers the tissue samples were positioned in the focus of a lens with 100 mm focal length. Ablation rates were determined by perforating samples of defined thickness, and the effects of laser ablation on tissue were controlled macroscopically, by light microscopy and by scanning electron microscopy.

  14. Proton acceleration from short pulse lasers interacting with ultrathin foil

    NASA Astrophysics Data System (ADS)

    Petrov, George; McGuffey, Christopher; Thomas, Alec; Krushelnick, Karl; Beg, Farhat

    2015-11-01

    Two-dimensional particle-in-cell simulations using 50 nm Si3N4 and DLC foils are compared to published experimental data of proton acceleration from ultra-thin foils (<1 μm) irradiated by short pulse lasers (30-50 fs), and some underlying physics issues pertinent to proton acceleration have been addressed. 2D particle-in-cell simulations show that the maximum proton energy scales as I2/3, stronger than Target Normal Sheath Acceleration for thick foils (>1 μm), which is typically between I1/3 and I1/2. Published experimental data were found to depend primarily on the laser energy and scale as E2/3. The different scaling laws for thick (>1 μm) and ultra-thin (<1 μm) foils are explained qualitatively as transitioning from Target Normal Sheath Acceleration to more advanced acceleration schemes such as Radiation-Induced Transparency and Radiation Pressure Acceleration regimes. This work was performed with the support of the Air Force Office of Scientific Research under grant FA9550-14-1-0282.

  15. Recent progress in pulsed laser deposition of iron based superconductors

    NASA Astrophysics Data System (ADS)

    Haindl, Silvia; Molatta, Sebastian; Hiramatsu, Hidenori; Hosono, Hideo

    2016-09-01

    Pulsed laser deposition (PLD) is the most commonly used deposition technique for Fe-based superconductor thin films today. The number of grown compounds using PLD is still quite limited to so-called 11 compounds (FeTe x S y , FeSe1‑x Te x ) and 122 compounds (primarily Co- and P-substituted BaFe2As2). Especially in the growth of Fe-chalcogenides, PLD is challenged by the strong volatility of the elements and their non-negligible vapour pressure. In addition, in situ PLD of the high-temperature superconducting F-doped iron oxypnictides seemed to be feasible only under reactive deposition and stayed disregarded for some time. Here, we summarise the progress that was recently made in the growth of Fe-based superconducting thin films towards an improved control of thin film stoichiometry and the in situ growth of F-doped iron oxypnictides. The presented new ideas deviate from the standard approach of an adjustment of target composition. We first focus on the growth of FeSe1‑x Te x films, where the introduction of a buffer layer of same composition decreased surface roughness and allowed epitaxial film growth at reduced deposition temperatures with enhanced reproducibility. Second, we illustrate how F-doping in iron oxypnictide thin films can be obtained during in situ PLD using a diffusive reaction between substrate and the growing film.

  16. The efficiency of photovoltaic cells exposed to pulsed laser light

    NASA Technical Reports Server (NTRS)

    Lowe, R. A.; Landis, G. A.; Jenkins, P.

    1993-01-01

    Future space missions may use laser power beaming systems with a free electron laser (FEL) to transmit light to a photovoltaic array receiver. To investigate the efficiency of solar cells with pulsed laser light, several types of GaAs, Si, CuInSe2, and GaSb cells were tested with the simulated pulse format of the induction and radio frequency (RF) FEL. The induction pulse format was simulated with an 800-watt average power copper vapor laser and the RF format with a frequency-doubled mode-locked Nd:YAG laser. Averaged current vs bias voltage measurements for each cell were taken at various optical power levels and the efficiency measured at the maximum power point. Experimental results show that the conversion efficiency for the cells tested is highly dependent on cell minority carrier lifetime, the width and frequency of the pulses, load impedance, and the average incident power. Three main effects were found to decrease the efficiency of solar cells exposed to simulated FEL illumination: cell series resistance, LC 'ringing', and output inductance. Improvements in efficiency were achieved by modifying the frequency response of the cell to match the spectral energy content of the laser pulse with external passive components.

  17. Pulsed laser deposition of niobium nitride thin films

    SciTech Connect

    Farha, Ashraf Hassan Elsayed-Ali, Hani E.; Ufuktepe, Yüksel; Myneni, Ganapati

    2015-12-04

    Niobium nitride (NbN{sub x}) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbN{sub x} films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ∼40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbN{sub x} films from mixed β-Nb{sub 2}N and cubic δ-NbN phases to single hexagonal β-Nb{sub 2}N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbN{sub x} deposited on Si(100) were also investigated. The NbN{sub x} films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbN{sub x} film morphology and phase.

  18. Pulsed laser interactions with space debris: Target shape effects

    DOE PAGESBeta

    Liedahl, D. A.; Rubenchik, A.; Libby, S. B.; Nikolaev, S.; Phipps, C. R.

    2013-05-24

    Among the approaches to the proposed mitigation and remediation of the space debris problem is the de-orbiting of objects in low Earth orbit through irradiation by ground-based high-intensity pulsed lasers. Laser ablation of a thin surface layer causes target recoil, resulting in the depletion of orbital angular momentum and accelerated atmospheric re-entry. However, both the magnitude and direction of the recoil are shape dependent, a feature of the laser-based remediation concept that has received little attention. Since the development of a predictive capability is desirable, we have investigated the dynamical response to ablation of objects comprising a variety of shapes.more » We derive and demonstrate a simple analytical technique for calculating the ablation-driven transfer of linear momentum, emphasizing cases for which the recoil is not exclusively parallel to the incident beam. For the purposes of comparison and contrast, we examine one case of momentum transfer in the low-intensity regime, where photon pressure is the dominant momentum transfer mechanism, showing that shape and orientation effects influence the target response in a similar, but not identical, manner. As a result, we address the related problem of target spin and, by way of a few simple examples, show how ablation can alter the spin state of a target, which often has a pronounced effect on the recoil dynamics.« less

  19. A laser spectrometer and wavemeter for pulsed lasers

    NASA Technical Reports Server (NTRS)

    Mckay, J. A.; Laufer, P. M.; Cotnoir, L. J.

    1989-01-01

    The design, construction, calibration, and evaluation of a pulsed laser wavemeter and spectral analyzer are described. This instrument, called the Laserscope for its oscilloscope-like display of laser spectral structure, was delivered to NASA Langley Research Center as a prototype of a laboratory instrument. The key component is a multibeam Fizeau wedge interferometer, providing high (0.2 pm) spectral resolution and a linear dispersion of spectral information, ideally suited to linear array photodiode detectors. Even operating alone, with the classic order-number ambiguity of interferometers unresolved, this optical element will provide a fast, real-time display of the spectral structure of a laser output. If precise wavelength information is also desired then additional stages must be provided to obtain a wavelength measurement within the order-number uncertainty, i.e., within the free spectral range of the Fizeau wedge interferometer. A Snyder (single-beam Fizeau) wedge is included to provide this initial wavelength measurement. Difficulties in achieving the required wide-spectrum calibration limit the usefulness of this function.

  20. Laser-supported detonation waves and pulsed laser propulsion

    SciTech Connect

    Kare, J.T.

    1989-01-01

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10{sup 4} K, 10{sup 2} atmospheres, 10{sup 7} w/cm{sup 2}) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition if the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research questions still outstanding in this area. 16 refs., 7 figs.

  1. Laser-supported detonation waves and pulsed laser propulsion

    SciTech Connect

    Kare, J. )

    1990-07-30

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10{sup 4} K, 10{sup 2} atmospheres, 10{sup 7} w/cm{sup 2}) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition of the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the Program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research question still outstanding in this area.

  2. Er,Cr:YSGG Pulsed laser applied to medical dentistry

    NASA Astrophysics Data System (ADS)

    Beltrano, J. J.; Torrisi, L.; Campagna, E.; Rapisarda, E.; Finocchiaro, I.; Olivi, G.

    An erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) pulsed laser, operating at 2780 μ m wavelength, 300 mJ maximum pulse energy, 140 μ s pulse duration and 20 Hz repetition rate, was employed to irradiate human teeth. The photon energy is transmitted to the tooth through an optical fiber with a sapphire tip, which is dipped in an adjustable air/water atomizer spray. Extracted teeth were cleaned in an ultrasonic bath, stored in saline solution, and dried and weighed before each laser treatment. The laser irradiation was performed for 10 s using a 600 μ m focused beam. Each sample was irradiated varying the air/water ratio of the integrated nebulizer spray. After the treatment, the samples were again weighed and produced craters were analyzed with a profilometric system. The crater volume permitted to evaluate the laser ablation yield. Teeth treated with an air/water spray ratio of 95-80% resulted in greatest average quantity of tissue ablation. This investigation confirmed the high efficiency of the Er,Cr:YSGG laser in the ablation of dental hard tissues showing the fundamental role of the water spray, which plays a fundamental role in the quantitative and qualitative modifications of the hard tissue treated, as it will be discussed in detail.

  3. Synthesis of cubic ruthenium nitride by reactive pulsed laser ablation

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

    The recent synthesis of platinum nitride opens the possibility of novel platinum-group metal nitrides to exist. In this work we report the synthesis of ruthenium nitride by reactive pulsed laser ablation. Several plausible structures have been evaluated by ab initio calculations using the full potential linearized augmented plane wave method, in order to investigate the ruthenium nitride structural and electronic properties. In fact, the predicted symmetry of stoichiometric RuN matches the experimental diffraction data. RuN crystallizes with NaCl-type structure at room temperature with cell-parameter somewhat larger than predicted by calculations. However we found a marginal chemical strength in these nitrides. The material is destroyed by mild acid and basic solutions. Under annealing RuN decomposes abruptly for temperatures beyond 100 °C. Since the thermal stability correlates directly with the mechanical properties our finding cast doubts than the latter transition metal nitrides can be ultra-hard materials at ambient conditions.

  4. Adaptive optics for ultra short pulsed lasers in UHV environment

    NASA Astrophysics Data System (ADS)

    Deneuville, Francois; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-02-01

    ISP SYSTEM has developed an electro-mechanical deformable mirror compatible with Ultra High Vacuum environment, suitable for ultra short pulsed lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations. μ-AME actuators are driven by stepper motors, and their patented special design allows controlling the force with a very high accuracy. Materials and assembly method have been adapted to UHV constraints and the performances were evaluated on a first application for a beam with a diameter of 250mm. A Strehl ratio above 0.9 was reached for this application. Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for standard MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The deformable mirror design allows changing easily an actuator or even the membrane if needed, in order to improve the facility availability. They are designed for circular, square or elliptical aperture from 30mm up to 500mm or more, with incidence angle from 0° to 45°. They can be equipped with passive or active cooling for high power lasers with high repetition rate.

  5. Quantum Hooke's Law to classify pulse laser induced ultrafast melting

    DOE PAGESBeta

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-02-03

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes ofmore » materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.« less

  6. Soft x ray optics by pulsed laser deposition

    NASA Technical Reports Server (NTRS)

    Fernandez, Felix E.

    1994-01-01

    A series of molybdenum thin film depositions by PLD (Pulsed Laser Deposition) have been carried out, seeking appropriate conditions for multilayer fabrication. Green (532 nm) and UV (355 nm) light pulses, in a wide range of fluences, were used. Relatively large fluences (in comparison with Si) are required to cause evaporation of molybdenum. The optical penetration depths and reflectivities for Mo at these two wavelengths are comparable, which means that results should be, and do appear to be similar for equal fluences. For all fluences above threshold used, a large number of incandescent particles is ejected by the target (either a standard Mo sputtering target or a Mo sheet were tried), together with the plasma plume. Most of these particles are clearly seen to bounce off the substrate. The films were observed with light microscopy using Nomarski and darkfield techniques. There is no evidence of large debris. Smooth films plus micron-sized droplets are usually seen. The concentration of these droplets embedded in the film appears not to vary strongly with the laser fluence employed. Additional characterization with SEM and XRD is under way.

  7. Hardening of smooth pulsed laser deposited PMMA films by heating

    NASA Astrophysics Data System (ADS)

    Fuchs, Britta; Schlenkrich, Felix; Seyffarth, Susanne; Meschede, Andreas; Rotzoll, Robert; Vana, Philipp; Großmann, Peter; Mann, Klaus; Krebs, Hans-Ulrich

    2010-03-01

    Smooth poly(methyl methacrylate) (PMMA) films without any droplets were pulsed laser deposited at a wavelength of 248 nm and a laser fluence of 125 mJ/cm2. After deposition at room temperature, the films possess low universal hardness of only 3 N/mm2. Thermal treatments up to 200°C, either during deposition or afterwards, lead to film hardening up to values of 200 N/mm2. Using a combination of complementary methods, two main mechanisms could be made responsible for this temperature induced hardening effect well above the glass transition temperature of 102°C. The first process is induced by the evaporation of chain fragments and low molecular mass material, which are present in the film due to the ablation process, leading to an increase of the average molecular mass and thus to hardening. The second mechanism can be seen in partial cross-linking of the polymer film as soon as chain scission occurs at higher temperatures and the mobility and reactivity of the polymer material is high enough.

  8. Pulsed laser deposition of polymer-metal nanocomposites

    NASA Astrophysics Data System (ADS)

    Schlenkrich, Felix; Seyffarth, Susanne; Fuchs, Britta; Krebs, Hans-Ulrich

    2011-04-01

    Different polymer-metal nanocomposites, metal clusters on a polymer surface and for the first time also polymer/metal multilayers, were pulsed laser deposited at a wavelength of 248 nm. Poly(methyl methacrylate) (PMMA) and Bisphenol A dimeth-acrylate (BisDMA), which strongly differ in their hardness of 3 and 180 N/mm 2, respectively, were taken as polymer components. Metals Ag and Cu were chosen because of their different reactivity to polymers. When depositing Ag on PMMA, spherical clusters are formed due to high diffusion and total coalescence. For Cu, much smaller grains with partially elongated shapes occur because of lower diffusivity and incomplete coalescence. Compared to the results on the soft PMMA, the clusters formed on the harder BisDMA are much larger due to higher diffusivity on this underlayer. In PMMA/Cu multilayers, wavy layered structures and buckling is observed due to relaxation of compressive stress in the Cu layers. Smooth Cu layers with higher thicknesses can only be obtained, when the hardness of the polymer is sufficiently high, as in the case of BisDMA/Cu multilayers.

  9. An experimental investigation of underwater pulsed laser forming

    NASA Astrophysics Data System (ADS)

    Shen, Hong; Ran, Maoli; Hu, Jun; Yao, Zhenqiang

    2014-11-01

    Laser forming is a new forming technology, which deforms a metal sheet using laser-induced thermal stresses. This paper presents an experimental investigation of pulsed laser forming of stainless steel in water and air. The effects of cooling conditions on bending angle and morphology of the heat affected zone (HAZ) are studied. It is shown that the case of the top surface in air and the bottom surface immersed in water has the greatest bending angle based on the forming mechanism of TGM. The water layer above the sample decreases the coupling energy, leading to a small bending angle. For a thin water thickness (1 mm), the water effects on the HAZ are limited. As water layer thickness increases (5 mm), the concave shape of the HAZ is more remarkable and irregular because the shock waves by high laser energy heating water are fully developed. However, the area and the depth of the HAZ become less significant when water thickness is 10 mm due to the long pathway that laser undergoes.

  10. Submicro foaming in biopolymers by UV pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Oujja, Mohamed; Rebollar, Esther; Gaspard, Solenne; Abrusci, Concepción; Catalina, Fernando; Lazare, Sylvain; Castillejo, Marta

    2006-05-01

    Microstructuring of polymers and biopolymers is of application in medical technology and biotechnology. Using different fabrication techniques three-dimensionally shaped and micro structured constructs can be developed for drug release and tissue engineering. As an alternative method, laser microstructuring offers a series of advantages including high resolution capability, low heat deposition in the substrate and high level of flexibility. In this work we present evidence of laser microfoam formation in collagen and gelatine by nanosecond pulsed laser irradiation in the UV at 248 and 266 nm. Irradiation at 355 nm produces melting followed by resolidification of the substrate, whereas irradiation at 532 and 1064 nm induces the formation of craters of irregular contours. Single pulse irradiation of a collagen film with an homogenized KrF microbeam yields a 20 μm thick expanded layer, which displays the interesting features of a nanofibrous 3-dimensional network with open cells. In gelatine, irradiation at 248 and 266 nm produces similar morphological modifications. The effect of the structural properties of the substrate on the laser induced microfoam is studied by comparing gelatines differing in gel strength (Bloom values 225 and 75) and in crosslinking degree. While results are discussed on the basis of thermal and photomechanical mechanisms and of the role played by the water content of the substrates, it is thought that such structures could have a biomimic function in future 3D cell culture devices for research.

  11. Quantum Hooke's Law to classify pulse laser induced ultrafast melting

    SciTech Connect

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-02-03

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.

  12. Ferroelectric thin films deposited by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Dinu, Raluca; Vrejoiu, I.; Verardi, P.; Craciun, F.; Dinescu, Maria

    2001-06-01

    Influence of substrate and electrode on the properties of PbZr0.53Ti0.47O3 (PZT) thin films grown by pulsed laser deposition technique (1060 nm wavelength Nd:YAG laser light, 10 ns pulse duration, 10 Hz repetition rate, 0.35 J/pulse, 25 J/cm2 laser fluence, deposition rate about 1 angstrom/pulse) was studied. The substrate temperatures were in the range 380 degree(s)C-400 degree(s)C. Oriented crystalline PZT layers with 1-3 micrometers thickness were deposited on glass substrates plated with Au/Pt/NiCr electrodes, from a PZT commercial target in oxygen reactive atmosphere. The deposited PZT films with perovskite structure were preferentially oriented along the (111) direction as revealed from XRD spectra. Piezoelectric d33 coefficients up to 30 pC/N were obtained on as deposited films. Ferroelectric hysteresis loops at 100 Hz revealed a remanent polarization of 15 (mu) C/cm2 and a coercive field of 100 kV/cm. A comparison with properties of PZT films deposited using a KrF laser and with SrBi2Ta2O9 (SBT) films is reported.

  13. Pulsed laser interactions with space debris: Target shape effects

    SciTech Connect

    Liedahl, D. A.; Rubenchik, A.; Libby, S. B.; Nikolaev, S.; Phipps, C. R.

    2013-05-24

    Among the approaches to the proposed mitigation and remediation of the space debris problem is the de-orbiting of objects in low Earth orbit through irradiation by ground-based high-intensity pulsed lasers. Laser ablation of a thin surface layer causes target recoil, resulting in the depletion of orbital angular momentum and accelerated atmospheric re-entry. However, both the magnitude and direction of the recoil are shape dependent, a feature of the laser-based remediation concept that has received little attention. Since the development of a predictive capability is desirable, we have investigated the dynamical response to ablation of objects comprising a variety of shapes. We derive and demonstrate a simple analytical technique for calculating the ablation-driven transfer of linear momentum, emphasizing cases for which the recoil is not exclusively parallel to the incident beam. For the purposes of comparison and contrast, we examine one case of momentum transfer in the low-intensity regime, where photon pressure is the dominant momentum transfer mechanism, showing that shape and orientation effects influence the target response in a similar, but not identical, manner. As a result, we address the related problem of target spin and, by way of a few simple examples, show how ablation can alter the spin state of a target, which often has a pronounced effect on the recoil dynamics.

  14. Investigation of long pulse laser induced flame on Al in air using optical interferometry

    NASA Astrophysics Data System (ADS)

    Zhang, Hongchao; Lu, Jian; Shen, Zhonghua; Ni, Xiaowu

    2013-05-01

    The process of long pulse laser(1ms) interaction with the aluminum plate was analyzed using Mach-Zehnder interferometer in this paper. A continuous semiconductor laser with about 50mW power and 532nm wavelength was used to detect the flame which induced by long pulse laser interaction with the aluminum plate. A high speed camera was used to capture the interferograms. The exposure time of the high speed camera is about 2 microseconds. And the frame rate is 2130fps. The high-speed camera and the long pulse laser pulse was synchronously controlled by the four-channel digital delay (Stanford Research Systems DG535).The FFT(Fast Fourier transform ) analysis is applied to extract the phase of the interferograms. The results provide an understanding of the process of long pulse laser drilling of the Al target.

  15. The optical functions of silicon at elevated temperatures and their application to pulsed laser annealing

    SciTech Connect

    Jellison, G.E. Jr.; Lowndes, D.H.; Wood, R.F.

    1993-06-01

    The results of measurements of the optical functions of silicon at elevated temperatures are reviewed and the results applied to pulsed laser annealing of silicon. Several optical experiments which were performed to understand the physics of pulsed laser annealing are described, and related to detailed thermal modeling. The fabrication of silicon solar cells using both thermal and laser processing is described, both of which give very goods results.

  16. Numerical simulation of temperature field in K9 glass irradiated by ultraviolet pulse laser

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Fang, Xiaodong

    2015-10-01

    The optical component of photoelectric system was easy to be damaged by irradiation of high power pulse laser, so the effect of high power pulse laser irradiation on K9 glass was researched. A thermodynamic model of K9 glass irradiated by ultraviolet pulse laser was established using the finite element software ANSYS. The article analyzed some key problems in simulation process of ultraviolet pulse laser damage of K9 glass based on ANSYS from the finite element models foundation, meshing, loading of pulse laser, setting initial conditions and boundary conditions and setting the thermal physical parameters of material. The finite element method (FEM) model was established and a numerical analysis was performed to calculate temperature field in K9 glass irradiated by ultraviolet pulse laser. The simulation results showed that the temperature of irradiation area exceeded the melting point of K9 glass, while the incident laser energy was low. The thermal damage dominated in the damage mechanism of K9 glass, the melting phenomenon should be much more distinct.

  17. Enhanced 5-aminolevulinic acid-gold nanoparticle conjugate-based photodynamic therapy using pulse laser

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Yao, Cuiping; Wang, Jing; Chang, Zhennan; Zhang, Zhenxi

    2016-02-01

    The low bioavailability is a crucial limitation for the application of 5-aminolevulinic acid (ALA) in theranostics. In this research, 5-aminolevulinic acid and gold nanoparticle conjugates (ALA-GNPs) were synthesized to improve the bioavailability of ALA and to investigate the impact of ALA photodynamic therapy (ALA-PDT) in Hela cells. A 532 nm pulse laser and light-emitting diode (central wavelengths 502 nm) were jointly used as light sources in PDT research. The results show a 532 nm pulse laser can control ALA release from ALA-GNPs by adjusting the pulse laser dose. This laser control release may be attributed to the heat generation from GNPs under pulse laser irradiation, which indicates accurately adjusting the pulse laser dose to control the drug release in the cell interior can be considered as a new cellular surgery modality. Furthermore, the PDT results in Hela cells indicate the enhancement of ALA release by pulse laser before PDT can promote the efficacy of cell eradication in the light-emitting diode PDT (LED-PDT). This laser mediated drug release system can provide a new online therapy approach in PDT and it can be utilized in the optical monitor technologies based individual theranostics.

  18. Pulsed laser processing of electronic materials in micro/nanoscale

    NASA Astrophysics Data System (ADS)

    Hwang, David Jen

    2005-08-01

    Time-resolved pump-and-probe side-view imaging has been performed to investigate the energy coupling to the target specimen over a wide range of fluences. Plasmas generated during the laser ablation process are visualized and the decrease of the ablation efficiency in the high fluence regime (>10 J/cm2) is attributed to the strong interaction of the laser pulse with the laser-induced plasmas. The high intensity ultra-short laser pulses also trigger volumetric multi-photon absorption (MPA) processes that can be beneficial in applications such as three-dimensional bulk modification of transparent materials. Femtosecond laser pulses were used to fabricate straight and bent through-channels in the optical glass. Drilling was initiated from the rear surface to preserve consistent absorbing conditions of the laser pulse. Machining in the presence of a liquid solution assisted the debris ejection. Drilling process was further enhanced by introducing ultrasonic waves, thereby increasing the aspect ratio of drilled holes and improving the quality of the holes. In conventional lens focusing schemes, the minimum feature size is determined by the diffraction limit. Finer resolution is accomplished by combining pulsed laser radiation with Near-field Scanning Optical Microscopy (NSOM) probes. Short laser pulses are coupled to a fiber-based NSOM probes in order to ablate thin metal films. A detailed parametric study on the effects of probe aperture size, laser pulse energy, temporal width and environment gas is performed. The significance of lateral thermal diffusion is highlighted and the dependence of the ablation process on the imparted near-field distribution is revealed. As a promising application of laser ablation in nanoscale, laser induced breakdown spectroscopy (LIBS) system has been built up based on NSOM ablation configuration. NSOM-LIBS is demonstrated with nanosecond pulsed laser excitation on Cr sample. Far-field collecting scheme by top objective lens was chosen as

  19. Electrochromic lithium nickel oxide by pulsed laser deposition and sputtering

    SciTech Connect

    Rubin, M.; Wen, S.J.; Richardson, T.; Kerr, J.; Rottkay, K. von; Slack, J.

    1996-09-01

    Thin films of lithium nickel oxide were deposited by sputtering and pulsed laser deposition (PLD) from targets of pressed LiNiO{sub 2} powder. The composition and structure of these films were analyzed using a variety of techniques, such as nuclear-reaction analysis, Rutherford backscattering spectrometry (RBS), x-ray diffraction, infrared spectroscopy, and atomic force microscopy. Crystalline structure, surface morphology and chemical composition of Li{sub x}Ni{sub 1{minus}x}O thin films depend strongly on deposition oxygen pressure, temperature as well as substrate-target distance. The films produced at temperatures lower than 600 C spontaneously absorb CO{sub 2} and H{sub 2}O at their surface once they are exposed to the air. The films deposited at 600 C proved to be stable in air over a long period. Even at room temperature the PLD films are denser and more stable than sputtered films. RBS determined the composition of the best films to be Li{sub 0.5}Ni{sub 0.5}O deposited by PLD at 60 mTorr O{sub 2} pressure. Electrochemical tests show that the films exhibit excellent reversibility in the range 1.0 V to 3.4 V versus lithium. Electrochemical formatting which is used to develop electrochromism in other films is not needed for the stoichiometric films. The optical transmission range is almost 70% at 550 nm for 150-nm thick films. Devices made from these films were analyzed using novel reference electrodes and by disassembly after cycling.

  20. Nanostructuring and texturing of pulsed laser deposited hydroxyapatite thin films

    NASA Astrophysics Data System (ADS)

    Kim, Hyunbin; Catledge, Shane; Vohra, Yogesh; Camata, Renato; Lacefield, William

    2003-03-01

    Hydroxyapatite (HA) [Ca_10(PO_4)_6(OH)_2] is commonly deposited onto orthopedic and dental metallic implants to speed up bone formation around devices, allowing earlier stabilization in a patient. Pulsed laser deposition (PLD) is a suitable means of placing thin HA films on these implants because of its control over stoichiometry, crystallinity, and nanostructure. These characteristics determine the mechanical properties of the films that must be optimized to improve the performance of load-bearing implants and other devices that undergo bone insertion. We have used PLD to produce nanostructured and preferentially oriented HA films and evaluated their mechanical properties. Pure, highly crystalline HA films on Ti-6Al-4V substrates were obtained using a KrF excimer laser (248nm) with energy density of 4-8 J/cm^2 and deposition temperature of 500-700^rcC. Scanning electron and atomic force microscopies reveal that our careful manipulation of energy density and substrate temperature has led to films made up of HA grains in the nanometer scale. Broadening of x-ray diffraction peaks as a function of deposition temperature suggests it may be possible to control the film nanostructure to a great extent. X-ray diffraction also shows that as the laser energy density is increased in the 4-8 J/cm^2 range, the hexagonal HA films become preferentially oriented along the c-axis perpendicular to the substrate. Texture, nanostructure, and phase make-up all significantly influence the mechanical properties. We will discuss how each of these factors affects hardness and Young's modulus of the HA films as measured by nanoindentation.

  1. Femtosecond pulsed laser deposition of biological and biocompatible thin layers

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Smausz, T.; Kecskeméti, G.; Klini, A.; Bor, Zs.

    2007-07-01

    In our study we investigate and report the femtosecond pulsed laser deposition of biological and biocompatible materials. Teflon, polyhydroxybutyrate, polyglycolic-acid, pepsin and tooth in the form of pressed pellets were used as target materials. Thin layers were deposited using pulses from a femtosecond KrF excimer laser system (FWHM = 450 fs, λ = 248 nm, f = 10 Hz) at different fluences: 0.6, 0.9, 1.6, 2.2, 2.8 and 3.5 J/cm 2, respectively. Potassium bromide were used as substrates for diagnostic measurements of the films on a FTIR spectrometer. The pressure in the PLD chamber was 1 × 10 -3 Pa, and in the case of tooth and Teflon the substrates were heated at 250 °C. Under the optimized conditions the chemical structure of the deposited materials seemed to be largely preserved as evidenced by the corresponding IR spectra. The polyglycolic-acid films showed new spectral features indicating considerable morphological changes during PLD. Surface structure and thickness of the layers deposited on Si substrates were examined by an atomic force microscopy (AFM) and a surface profilometer. An empirical model has been elaborated for the description of the femtosecond PLD process. According to this the laser photons are absorbed in the surface layer of target resulting in chemical dissociation of molecules. The fast decomposition causes explosion-like gas expansion generating recoil forces which can tear off and accelerate solid particles. These grains containing target molecules without any chemical damages are ejected from the target and deposited onto the substrate forming a thin layer.

  2. Infrared Pulsed Laser Deposition: Applications in Photonics and Biomedical Technologies

    NASA Astrophysics Data System (ADS)

    Haglund, Richard

    2006-04-01

    Resonant infrared pulsed-laser deposition (RIR-PLD) shows significant promise for synthesizing thin films of small organic molecules, thermoplastic and thermosetting polymers and biopolymers, without compromising structure or functionality. This contrasts with most attempts at UV-PLD of organic materials, which have often been accompanied by severe photochemical or photothermal degradation of the ablated material. Representative recent successes in RIR-PLD include deposition of: polymers for light emission and hole transport; functionalized polymers and nanoparticles for chemical and biological sensing; and biocompatible polymers suitable for coating medical devices or drug-delivery vehicles. Plume imaging and various other optical- and mass-spectroscopy experiments appear to confirm that polymers or organic molecules ablated by resonant infrared laser irradiation experience a high spatial and temporal density of vibrational excitation, but tend to remain in the electronic ground state. The mechanism of RIR-PLD is observed to depend on the anharmonicity of the mid-infrared absorption modes, their finite relaxation time, mode-specific nonlinear absorption, and rapid changes in polymer viscosity as a function of temperature. Many of the RIR-PLD experiments to date were carried out using a tunable, mid-infrared, picosecond free-electron laser. However, if RIR-PLD is to become a practical tool for making organic thin films, it will be necessary to develop more conventional lasers that can achieve a similar combination of high pulse intensity, low pulse energy, high pulse-repetition frequency and moderate average power. In conclusion, the prospects for developing precisely such table-top RIR-PLD systems will be discussed.

  3. Pulsed Laser Deposition of High Temperature Protonic Films

    NASA Technical Reports Server (NTRS)

    Dynys, Fred W.; Berger, M. H.; Sayir, Ali

    2006-01-01

    Pulsed laser deposition has been used to fabricate nanostructured BaCe(0.85)Y(0.15)O3- sigma) films. Protonic conduction of fabricated BaCe(0.85)Y(0.15)O(3-sigma) films was compared to sintered BaCe(0.85)Y(0.15)O(3-sigma). Sintered samples and laser targets were prepared by sintering BaCe(0.85)Y(0.15)O(3-sigma) powders derived by solid state synthesis. Films 1 to 8 micron thick were deposited by KrF excimer laser on porous Al2O3 substrates. Thin films were fabricated at deposition temperatures of 700 to 950 C at O2 pressures up to 200 mTorr using laser pulse energies of 0.45 - 0.95 J. Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe(0.85)Y(0.15)O(3-sigma) films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C to 900 C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 oC; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied

  4. Short-pulse laser removal of organic coatings

    NASA Astrophysics Data System (ADS)

    Walters, Craig T.

    2000-08-01

    A major problem in the regular maintenance of aerospace systems is the removal of paint and other protective coatings from surfaces without polluting the atmosphere or endangering workers. Recent research has demonstrated that many organic coatings can be removed from surfaces efficiently using short laser pulses without the use of any chemical agents. The lasers employed in this study were repetitively-pulsed neodymium YAG devices operating at 1064 nm (15 - 30 ns, 10 - 20 Hz). The efficiency of removal can be cast in terms of an effective heat of ablation, Q* (kJ of laser energy incident per g of paint removed), although, for short pulses, the mechanism of removal is believed to be dominated more by thermo- mechanical or shock effects than by photo-ablation. Q* data were collected as a function of pulse fluence for several paint types. For many paint types, there was a fairly sharp threshold fluence per pulse near 1 J/cm2, above which Q* values dropped to levels which were a factor of four lower than those observed for long- pulse or continuous laser ablation of paint. In this regime, the coating is removed in fairly large particles or, in the case of one paint, the entire thickness of the coating was removed over the exposed area in one pulse. Hardware for implementing short-pulse laser paint stripping in the field is under development and will be highlighted in the presentation. Practical paint stripping rates achieved using the prototype hardware are presented for several paint types.

  5. Improvement of Weld Characteristics by Laser-Arc Double-Sided Welding Compared to Single Arc Welding

    NASA Astrophysics Data System (ADS)

    Lei, Zhenglong; Zhang, Kezhao; Hu, Xue; Yang, Yuhe; Chen, Yanbin; Wu, Yichao

    2015-11-01

    The single arc welding and laser-arc double-sided welding (LADSW) processes are investigated by virtue of test welds. The impacts of the laser beam during the LADSW process on the weld characteristics are studied from weld geometry, crystal morphology, and the mechanical properties of the joints. Compared with the single arc welding, the LADSW process improves the energy density and reduces the range of arc action, which together leads to a doubling of weld penetration depth. When penetrated by the laser beam, the liquid metal of the arc welding pool experiences severe fluctuations, leading to a finer grain size in the range of 17-26 μm in the LADSW weld, a reduction of nearly 63% compared to the grains in the single arc weld. The tensile strength and elongation-to-failure of the LADSW weld were increased by nearly 10 and 100% over the single arc welding, respectively.

  6. Flow Dynamics in Arc Welding

    SciTech Connect

    Lowke, John J.; Tanaka, Manabu

    2008-02-21

    The state of the art for numerical computations has now advanced so that the capability is within sight of calculating weld shapes for any arc current, welding gas, welding material or configuration. Inherent in these calculations is 'flow dynamics' applied to plasma flow in the arc and liquid metal flow in the weld pool. Examples of predictions which are consistent with experiment, are discussed for (1) conventional tungsten inert gas welding, (2) the effect of a fraction of a percent of sulfur in steel, which can increase weld depth by more than a factor of two through changes in the surface tension, (3) the effect of a flux, which can produce increased weld depth due to arc constriction, (4) use of aluminium instead of steel, when the much larger thermal conductivity of aluminium greatly reduces the weld depth and (5) addition of a few percent of hydrogen to argon, which markedly increases weld depth.

  7. New Technology In Laser Welding Of Thin Filaments

    NASA Astrophysics Data System (ADS)

    Li, Yongzeng; Zhang, Qiu'e.; Ma, Shulin; Li, Yongda; Tian, Fenggui

    1987-01-01

    It is difficult to get a good welding spot and nearly impossible to weld a 10 micron diameter filament (e.g. NiCr) onto a foreign workpiece over 1000 times larger in size. In this paper we introduce the laser powder-covered welding technique. The first step is to laser- weld a metal powder onto a small area of interest of a larger-sized workpiece. This changes the nature of the larger-sized material. The second step is to position the thin filament in contact with the larger workpiece and to apply the pulsed laser so a round and smooth welding spot forms. This should form a good alloy combination. This welding technique has a high success rate for welding minute electrical heat source, independent of the material of the larger workpiece. This technique also solves the problems of unstable quality in tin welding, burrs in pressure welding, and eliminates the problem of welding flux corrosion. This same technique is applied to the laser-welding of a super-thin piece to a foreign workpiece, where the welding spot forms a "micro-rivet': In the paper we present specific conditions required, the analysis data of the welding quality and the specific structure of the laser-welding workstation.

  8. Method for enhanced control of welding processes

    SciTech Connect

    Sheaffer, D.A.; Renzi, R.F.; Tung, D.M.; Schroder, K.

    2000-07-04

    Method and system for producing high quality welds in welding processes, in general, and gas tungsten arc (GTA) welding, in particular by controlling weld penetration are disclosed. Light emitted from a weld pool is collected from the backside of a workpiece by optical means during welding and transmitted to a digital video camera for further processing, after the emitted light is first passed through a short wavelength pass filter to remove infrared radiation. By filtering out the infrared component of the light emitted from the backside weld pool image, the present invention provides for the accurate determination of the weld pool boundary. Data from the digital camera is fed to an imaging board which focuses on a 100 x 100 pixel portion of the image. The board performs a thresholding operation and provides this information to a digital signal processor to compute the backside weld pool dimensions and area. This information is used by a control system, in a dynamic feedback mode, to automatically adjust appropriate parameters of a welding system, such as the welding current, to control weld penetration and thus, create a uniform weld bead and high quality weld.

  9. Method for enhanced control of welding processes

    DOEpatents

    Sheaffer, Donald A.; Renzi, Ronald F.; Tung, David M.; Schroder, Kevin

    2000-01-01

    Method and system for producing high quality welds in welding processes, in general, and gas tungsten arc (GTA) welding, in particular by controlling weld penetration. Light emitted from a weld pool is collected from the backside of a workpiece by optical means during welding and transmitted to a digital video camera for further processing, after the emitted light is first passed through a short wavelength pass filter to remove infrared radiation. By filtering out the infrared component of the light emitted from the backside weld pool image, the present invention provides for the accurate determination of the weld pool boundary. Data from the digital camera is fed to an imaging board which focuses on a 100.times.100 pixel portion of the image. The board performs a thresholding operation and provides this information to a digital signal processor to compute the backside weld pool dimensions and area. This information is used by a control system, in a dynamic feedback mode, to automatically adjust appropriate parameters of a welding system, such as the welding current, to control weld penetration and thus, create a uniform weld bead and high quality weld.

  10. Femtosecond pulsed laser ablation of GaAs

    NASA Astrophysics Data System (ADS)

    Trelenberg, T. W.; Dinh, L. N.; Saw, C. K.; Stuart, B. C.; Balooch, M.

    2004-01-01

    The properties of femtosecond-pulsed laser deposited GaAs nanoclusters were investigated. Nanoclusters of GaAs were produced by laser ablating a single crystal GaAs target in vacuum or in a buffer gas using a Ti-sapphire laser with a 150 fs minimum pulse length. For in-vacuum deposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) revealed that the average cluster size was approximately 7 nm for laser pulse lengths between 150 fs and 25 ps. The average cluster size dropped to approximately 1.5 nm at a pulse length of 500 ps. It was also observed that film thickness decreased with increasing laser pulse length. A reflective coating, which accumulated on the laser admission window during ablation, reduced the amount of laser energy reaching the target for subsequent laser shots and developed more rapidly at longer pulse lengths. This observation indicates that non-stoichiometric (metallic) ablatants were produced more readily at longer pulse lengths. The angular distribution of ejected material about the target normal was well fitted to a bi-cosine distribution of cos 47 θ+ cos 4 θ for ablation in vacuum using 150 fs pulses. XPS and AES revealed that the vacuum-deposited films contained excess amorphous Ga or As in addition to the stoichiometric GaAs nanocrystals seen with XRD. However, films containing only the GaAs nanocrystals were produced when ablation was carried out in the presence of a buffer gas with a pressure in excess of 6.67 Pa. At buffer gas pressure on the order of 1 Torr, it was found that the stoichiometry of the ablated target was also preserved. These experiments indicate that both laser pulse length and buffer gas pressure play important roles in the formation of multi-element nanocrystals by laser ablation. The effects of gas pressure on the target's morphology and the size of the GaAs nanocrystals formed will also be discussed.

  11. Short Pulse Laser Production of Diamond Thin Films

    SciTech Connect

    Banks, P.S.; Stuart, B.C.; Dinh, L.; Feit, M.D.; Rubenchik, A.M.; McLean, W.; Perry, M.D.

    1998-03-20

    The use of diamond thin films has the potential for major impact in many industrial and scientific applications. These include heat sinks for electronics, broadband optical sensors, windows, cutting tools, optical coatings, laser diodes, cold cathodes, and field emission displays. Attractive properties of natural diamond consist of physical hardness, high tensile yield strength, chemical inertness, low coefficient of friction, high thermal conductivity, and low electrical conductivity. Unfortunately, these properties are not completely realized in currently produced diamond thin films. Chemical vapor deposition, in its many forms, has been the most successful to this point in producing crystalline diamond films microns to millimeters in thickness which are made up of closely packed diamond crystals microns in physical dimension. However, high purity films are difficult to realize due to the use of hydrogen in the growth process which becomes included in the film matrix. These impurities are manifest in film physical properties which are inferior to those of pure crystalline diamond. In addition, the large density of grain boundaries due to the polycrystalline nature of the films reduce the films' diamond-like character. Finally, substrates must be heated to several hundred degrees Celsius which is not suitable for many materials. Pulsed laser deposition is attractive due to its ability to produce high purity films-limited only by the purity of the target. For diamond film production, high purity carbon can be ablated directly by lasers and deposited as thin films at ambient temperatures. However, lasers currently in use generally deliver long (>10 ns) pulses, and the generally explosive nature of laser ablation, in addition to the desired single-atom or single-ion carbon, liberates significant amounts of carbon clusters (C{sub n} where n=2-30) and macroscopic particles (> 1-10 pm) of carbon. These carbon particles interrupt the ordered deposition of crystalline

  12. Nanostructured polymer stable glasses via matrix assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Shepard, Kimberly B.

    Amorphous materials, or glasses, which lack a crystalline structure, are technologically ubiquitous with applications including structural components, pharmaceuticals, and electronic devices. Glasses are traditionally formed by rapid cooling from the melt state, where molecules become kinetically trapped into a non-equilibrium configuration. The temperature at which the material transforms from supercooled liquid to glass is the glass transition temperature. The glass transition temperature is the most important property of amorphous materials, as it determines the range of temperatures where they are fabricated, used and stored. Recent technological developments in which glasses are formed by alternative routes, such as physical vapor deposition and matrix assisted pulsed laser evaporation (MAPLE), enable tunability of Tg and related physical properties. High-Tg glasses formed by these techniques are termed "stable glasses" and exhibit a wide range of exceptional properties. This work focuses on the formation and characterization of stable polymer glasses fabricated via MAPLE. Bulk films (>1 microm thick) of glassy polymers fabricated by MAPLE at slow growth rates (<1 nm/s) and controlled substrate temperature (T sub = 0.85Tg,bulk) have greatly elevated Tg, low density, high enthalpy, increased kinetic stability and a spheroidal nanostructure. We focus on connecting the bulk and nanoscale properties of MAPLE-deposited polymer glasses. Building on molecular dynamics simulations from the literature on the MAPLE process, we experimentally study the origin of nanostructure in our MAPLE-deposited films. We measure the time-of-flight of MAPLE-deposited material, confirming that the velocity is sufficiently low for intact deposition of polymer nanoglobules. The size distribution of polymer nanoglobules fabricated in short MAPLE depositions provides insight into how nanostructured MAPLE films form. Using our atomic force microscopy-based nanoscale dilatometry technique

  13. Method for laser welding ultra-thin metal foils

    DOEpatents

    Pernicka, J.C.; Benson, D.K.; Tracy, C.E.

    1996-03-26

    A method for simultaneously cutting and welding ultra-thin foils having a thickness of less than 0.002 inches wherein two ultra-thin films are stacked and clamped together. A pulsed laser such as of the Neodymium: YAG type is provided and the beam of the laser is directed onto the stacked films to cut a channel through the films. The laser is moved relative to the stacked foils to cut the stacked foils at successive locations and to form a plurality of connected weld beads to form a continuous weld. 5 figs.

  14. Method for laser welding ultra-thin metal foils

    DOEpatents

    Pernicka, John C.; Benson, David K.; Tracy, C. Edwin

    1996-01-01

    A method for simultaneously cutting and welding ultra-thin foils having a thickness of less than 0.002 inches wherein two ultra-thin films are stacked and clamped together. A pulsed laser such as of the Neodymium: YAG type is provided and the beam of the laser is directed onto the stacked films to cut a channel through the films. The laser is moved relative to the stacked foils to cut the stacked foils at successive locations and to form a plurality of connected weld beads to form a continuous weld.

  15. Liquid atomization induced by pulse laser reflection at and beneath the liquid surface

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    In this paper, precision high speed imaging of the pulse laser ablation of liquid surface has been described. This study is based on our previous findings that appreciable reduction of pulse laser ablation threshold of transparent material in case the pulse laser beam is incident from the water side on the interface of the transparent material and air or water. We have performed a series of experiments to observe the ablation process for laser incidence on the interface of water and air. Whole processes were observed by shadowgraphy optics by using a ns pulse laser and a high-resolution film. Within the tested experimental conditions, minimum laser fluence for laser ablation at water-air interface is shown to be around 12-16 J/cm2. We have confirmed that laser ablation phenomena will take place only when laser beam is incident on the water-air interface from inside the water medium. Many slender liquid ligaments extend like milk crown and seem to be atomized at the tip of them. Jet tip is moving at supersonic velocity but is decelerated very rapidly. By changing the laser energy with keeping laser fluence at the interface, temporal evolution changes appreciably at least in the early stage of the process. These detailed structures can be resolved only by pulse laser photography by using high-resolution film.

  16. Polyethylene welding by pulsed visible laser irradiation

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Caridi, F.; Visco, A. M.; Campo, N.

    2011-01-01

    Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as “through transmission visible laser welding”. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part. In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

  17. Development of laser welding techniques for vanadium alloys

    SciTech Connect

    Strain, R.V.; Leong, K.H.; Smith, D.L.

    1996-04-01

    Laser welding is potentially advantageous because of its flexibility and the reduced amount of material affected by the weld. Lasers do not require a vacuum (as do electron beam welders) and the welds they produce high depth-to-width ratios. Scoping with a small pulsed 50 J YAG laser indicated that lasers could produce successful welds in vanadium alloy (V-5%Cr-5%Ti) sheet (1 mm thick) when the fusion zone was isolated from air. The pulsed laser required an isolating chamber filled with inert gas to produce welds that did not contain cracks and showed only minor hardness increases. Following the initial scoping tests, a series of tests were preformed with a 6 kW continuous CO{sub 2} laser. Successful bead-on-plate welds were made on V-4%Cr-4%Ti and V-5%Cr-5%Ti alloys to depths of about 4 mm with this laser.

  18. Pulsed laser interferometry with sub-picometer resolution using quadrature detection.

    PubMed

    Shao, Lei; Gorman, Jason J

    2016-07-25

    Femtosecond pulsed laser interferometry has important applications in measuring picometer-level displacements on sub-nanosecond time scales. In this paper, we experimentally examine its achievable displacement resolution, as well as the relationship between the laser's optical spectrum and the interferometer's effective wavelength. The resulting broadband displacement noise and noise floor of the pulsed laser Michelson interferometer are equivalent to that achieved with a stabilized continuous wave HeNe laser, where values of 1.01 nm RMS and 27.75 fm/√Hz have been demonstrated. It is also shown that a single effective wavelength can accurately describe the fringes of the pulsed laser interferometer but the effective wavelength value can only be determined from the optical spectrum under certain conditions. These results will be used for time-resolved displacement metrology with picosecond temporal resolution in the future. PMID:27464192

  19. Pulsed-Laser Deposition of Electronic Oxides: Superconductor and Semiconductor Applications

    SciTech Connect

    Norton, D.P.; Park, C.; Lee, Y.E.; Budai, J.D.; Chisholm, M.F.; Verebelyi, D.T.; Christen, D.K.; Kroeger, D.M.

    2000-01-24

    Over the past decade, pulsed-laser deposition (PLD) has proven to be one of the most versatile and effective methods for obtaining high-quality electronic oxide thin-film materials. Much of this success can be attributed to its initial use in depositing high temperature superconducting materials. However, pulsed-laser deposition is now a leading research tool in the development of various electronic oxide thin-film technologies, In this paper, recent progress in the deposition of oxide materials on dissimilar materials for both superconductor and semiconductor applications is discussed. Recent developments in the synthesis of superconducting wires via epitaxial growth of superconducting oxides on biaxially textured metal tapes is described. In addition, efforts to integrate high-k dielectric oxides on semiconductor surfaces using pulsed-laser deposition are highlighted.

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

    SciTech Connect

    Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun Wang, Kedian; Mei, Xuesong

    2014-03-15

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

  1. Understanding Femtosecond-Pulse Laser Damage through Fundamental Physics Simulations

    NASA Astrophysics Data System (ADS)

    Mitchell, Robert A., III

    It did not take long after the invention of the laser for the field of laser damage to appear. For several decades researchers have been studying how lasers damage materials, both for the basic scientific understanding of highly nonequilibrium processes as well as for industrial applications. Femtosecond pulse lasers create little collateral damage and a readily reproducible damage pattern. They are easily tailored to desired specifications and are particularly powerful and versatile tools, contributing even more industrial interest in the field. As with most long-standing fields of research, many theoretical tools have been developed to model the laser damage process, covering a wide range of complexities and regimes of applicability. However, most of the modeling methods developed are either too limited in spatial extent to model the full morphology of the damage crater, or incorporate only a small subset of the important physics and require numerous fitting parameters and assumptions in order to match values interpolated from experimental data. Demonstrated in this work is the first simulation method capable of fundamentally modeling the full laser damage process, from the laser interaction all the way through to the resolidification of the target, on a large enough scale that can capture the full morphology of the laser damage crater so as to be compared directly to experimental measurements instead of extrapolated values, and all without any fitting parameters. The design, implementation, and testing of this simulation technique, based on a modified version of the particle-in-cell (PIC) method, is presented. For a 60 fs, 1 mum wavelength laser pulse with fluences of 0.5 J/cm 2, 1.0 J/cm2, and 2.0 J/cm2 the resulting laser damage craters in copper are shown and, using the same technique applied to experimental crater morphologies, a laser damage fluence threshold is calculated of 0.15 J/cm2, consistent with current experiments performed under conditions similar

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

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kurosaki, Ryozo

    2011-03-01

    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, λ= 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.

  3. Modeling crater formation in femtosecond-pulse laser damage from basic principles.

    PubMed

    Mitchell, Robert A; Schumacher, Douglass W; Chowdhury, Enam A

    2015-05-15

    We present the first fundamental simulation method for the determination of crater morphology due to femtosecond-pulse laser damage. To this end we have adapted the particle-in-cell (PIC) method commonly used in plasma physics for use in the study of laser damage and developed the first implementation of a pair potential for PIC codes. We find that the PIC method is a complementary approach to modeling laser damage, bridging the gap between fully ab-initio molecular dynamics approaches and empirical models. We demonstrate our method by modeling a femtosecond-pulse laser incident on a flat copper slab for a range of intensities. PMID:26393696

  4. Pulsed laser induced switching of birefringence in nematic phase of photochromic molecules

    NASA Astrophysics Data System (ADS)

    Mysliwiec, J.; Czajkowski, M.; Bartkiewicz, S.; Zygadlo, K.; Galewski, Z.; Sahraoui, B.

    2011-02-01

    Fast and dynamic switching of liquid-crystalline photochromic system birefringence induced by pulsed laser has been observed. The system consisted of photochromic molecules of 4-heptyl-4'-methoxyazobenzene showing liquid-crystalline nematic state close to the room temperature. Experiment of dynamic birefringence switching was done in optical Kerr effect (OKE) set-up, where for the sample excitation picosecond pulsed laser was used. Simultaneously, HeNe laser was served as a probe beam source. Measurements were done for different voltages applied to the sample. Rise time constant was in the range of microseconds. Full reversibility of the OKE signal was observed.

  5. Stabilizing laser energy density on a target during pulsed laser deposition of thin films

    DOEpatents

    Dowden, Paul C.; Jia, Quanxi

    2016-05-31

    A process for stabilizing laser energy density on a target surface during pulsed laser deposition of thin films controls the focused laser spot on the target. The process involves imaging an image-aperture positioned in the beamline. This eliminates changes in the beam dimensions of the laser. A continuously variable attenuator located in between the output of the laser and the imaged image-aperture adjusts the energy to a desired level by running the laser in a "constant voltage" mode. The process provides reproducibility and controllability for deposition of electronic thin films by pulsed laser deposition.

  6. Space charge limited electron emission from a Cu surface under ultrashort pulsed laser irradiation

    SciTech Connect

    Wendelen, W.; Autrique, D.; Bogaerts, A.

    2010-10-08

    In this theoretical study, the electron emission from a copper surface under ultrashort pulsed laser irradiation is investigated using a one dimensional particle in cell model. Thermionic emission as well as multi-photon photoelectron emission were taken into account. The emitted electrons create a negative space charge above the target, consequently the generated electric field reduces the electron emission by several orders of magnitude. The simulations indicate that the space charge effect should be considered when investigating electron emission related phenomena in materials under ultrashort pulsed laser irradiation of metals.the word ''abstract,'' but do replace the rest of this text.

  7. Application of short pulsed laser systems for micro-scale processing.

    SciTech Connect

    Jared, Bradley Howell

    2010-03-01

    The relatively recent development of short (nsec) and ultra-short (fsec) pulsed laser systems has introduced process capabilities which are particularly suited for micro-manufacturing applications. Micrometer feature resolutions and minimal heat affected zones are commonly cited benefits, although unique material interactions also prove attractive for many applications. A background of short and ultra-short pulsed laser system capabilities and material interactions will be presented for micro-scale processing. Processing strengths and limitations will be discussed and demonstrated within the framework of applications related to micro-machining, material surface modifications, and fundamental material science research.

  8. The effect of the laser wavelength on collinear double pulse laser induced breakdown spectroscopy (DP-LIBS)

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Lin, Yanqing; Liu, Jing; Fan, Shuang; Xu, Zhuopin; Huang, Qing; Wu, Yuejin

    2016-05-01

    The pulsed lasers at wavelengths of 532 nm and 1064 nm were used as two beams of light for collinear double pulse laser induced breakdown spectroscopy (DP-LIBS). By changing the time sequence of two beams of different lasers, we studied the effect of the interval of two pulses of DP-LIBS on spectral signals compared with single pulsed (SP) LIBS.

  9. Welding wire pressure sensor assembly

    NASA Technical Reports Server (NTRS)

    Morris, Timothy B. (Inventor); Milly, Peter F., Sr. (Inventor); White, J. Kevin (Inventor)

    1994-01-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  10. Welding wire pressure sensor assembly

    NASA Astrophysics Data System (ADS)

    Morris, Timothy B.; Milly, Peter F.; White, J. Kevin

    1993-05-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  11. Welding wire pressure sensor assembly

    NASA Astrophysics Data System (ADS)

    Morris, Timothy B.; Milly, Peter F., Sr.; White, J. Kevin

    1994-04-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  12. Mapping Redistribution Of Metal In Welds

    NASA Technical Reports Server (NTRS)

    Barkhoudarian, Sarkis

    1988-01-01

    Radioactive-tracer technique applied to map redistribution of metal caused by welding process. Surfaces of parts welded irradiated by particle-beam generators to make them slightly radioactive. Used to verify predictions of computer codes for dynamics of fluids in weld pools.

  13. Three-Dimensional Coaxial Weld Monitoring

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S.

    1989-01-01

    Optical system for coaxial-viewing welding torch enables perception or measurement of depth. Light from welding area passes through beam splitter into two optical trains forming two images, each viewed along line making small angle with axis of torch. Two lines of sight intersect at weld pool. Parallax between two views provides sensation of depth over entire field view.

  14. Melting Efficiency During Plasma Arc Welding

    NASA Technical Reports Server (NTRS)

    McClure, J.C.; Evans, D. M.; Tang, W.; Nunes, A. C.

    1999-01-01

    A series of partial penetration Variable Polarity Plasma Arc welds were made at equal power but various combinations of current and voltage on 2219 aluminum. Arc Efficiency was measured calorimetrically and ranged between 48% and 66%. Melting efficiency depends on the weld pool shape. Increased current increases the melting efficiency as it increases the depth to width ratio of the weld pool. Higher currents are thought to raise arc pressure and depress the liquid at the bottom of the weld pool causing a more nearly two dimensional heat flow condition.

  15. Swimming Pools.

    ERIC Educational Resources Information Center

    Ministry of Housing and Local Government, London (England).

    Technical and engineering data are set forth on the design and construction of swimming pools. Consideration is given to site selection, pool construction, the comparative merits of combining open air and enclosed pools, and alternative uses of the pool. Guidelines are presented regarding--(1) pool size and use, (2) locker and changing rooms, (3)…

  16. On the Nd:YAG pulsed laser processing of rigid PVC

    NASA Astrophysics Data System (ADS)

    Hernández, L. C.; Arronte, M.; Ponce, L.; Flores, T.; Guerrero, J.; de Posada, E.; Rodríguez, E.

    2009-09-01

    The potential of Nd:YAG pulsed laser to processing PVC sheets minimizing HCl gases emission is investigated. We studied the gas emission when the PVC is cut by either CO2 or Nd:YAG pulsed laser by using FTIR Spectroscopy. Optical microscopy of laser treated PVC samples was performed in order to demonstrate the carbonization. On the other hand, LIBS spectroscopy for two different ranges of pulse duration was employed in order to investigate the plume composition during the Nd:YAG pulsed laser ablation process. The experiments shows that Cl atoms are emitted during the Nd:YAG pulsed laser ablation although the HCl gases are produced at low levels. In order to explain the sub-surface irregularities detected for Nd:YAG laser irradiation, a one-dimensional model is developed to study the temperature evolution inside the sample. We demonstrate that the ablation mechanisms prevail on thermally drive emission until 70 μm, afterwards the thermal expansion process is already observed.

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

    NASA Astrophysics Data System (ADS)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

    1998-05-01

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

  18. Wettability of oxide thin films prepared by pulsed laser deposition: New insights

    NASA Astrophysics Data System (ADS)

    Prakash, Saurav

    The objective of the thesis is to investigate the wettability of good quality oxide thin films prepared by pulsed laser deposition (PLD). In this work, many shortfalls in the water contact angle measurement of thin films of oxides, responsible for the wide scatter in the values reported in literature, have been addressed. (Abstract shortened by UMI.).

  19. Pulsed laser photolysis kinetics study of the O(3P) + ClO reaction

    NASA Technical Reports Server (NTRS)

    Nicovich, J. M.; Wine, P. H.; Ravishankara, A. R.

    1988-01-01

    A pulsed laser photolysis technique was used to investigate the kinetics of the important stratospheric reaction O + ClO yields Cl + O2 in buffer gas over the temperature and pressure ranges of 231-367 K and 25-500 torr. The results indicate a lack of pressure dependence at 298 K over the 25-500 torr range.

  20. Studies of Inactivation Mechanism of non-enveloped icosahedral viruses by a visible ultrashort pulsed laser

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The inactivation mechanism of ultrashort pulsed laser irradiation at a wavelength of 425 nm has been studied using two different-sized, non-enveloped icosahedral viruses, murine norovirus-1 (MNV-1) and human papillomavirus-16 (HPV-16) pseudovirions. Our experimental results are consistent with a mo...

  1. Ultrashort pulsed laser treatment inactivates viruses by inhibiting viral replication and transcription in the host nucleus

    PubMed Central

    Tsen, Shaw-Wei D.; Chapa, Travis; Beatty, Wandy; Xu, Baogang; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Ultrashort pulsed laser irradiation is a new method for virus reduction in pharmaceuticals and blood products. Current evidence suggests that ultrashort pulsed laser irradiation inactivates viruses through an impulsive stimulated Raman scattering process, resulting in aggregation of viral capsid proteins. However, the specific functional defect(s) in viruses inactivated in this manner have not been demonstrated. This information is critical for the optimization and the extension of this treatment platform to other applications. Toward this goal, we investigated whether viral internalization, replication, or gene expression in cells were altered by ultrashort pulsed laser irradiation. Murine Cytomegalovirus (MCMV), an enveloped DNA virus, was used as a model virus. Using electron and fluorescence microscopy, we found that laser-treated MCMV virions successfully internalized in cells, as evidenced by the detection of intracellular virions, which was confirmed by the detection of intracellular viral DNA via PCR. Although the viral DNA itself remained polymerase-amplifiable after laser treatment, no viral replication or gene expression was observed in cells infected with laser-treated virus. These results, along with evidence from previous studies, support a model whereby the laser treatment stabilizes the capsid, which inhibits capsid uncoating within cells. By targeting the mechanical properties of viral capsids, ultrashort pulsed laser treatment represents a unique potential strategy to overcome viral mutational escape, with implications for combatting emerging or drug-resistant pathogens. PMID:25086212

  2. Experiments of glucose solution measurement based on the tunable pulsed laser induced photoacoustic spectroscopy method

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Xiong, Zhihua; Huang, Zhen

    2015-07-01

    Photoacoustic spectroscopy (PAS) is a hybrid, well-established and promising detection technique that has widely applied into a lot of fields such as bio-medical, material and environment monitoring etc. PAS has high contrast and resolution because of combining the advantages of the pure-optical and the pure-acoustic. In this paper, a photoacoustic experiment of glucose solution induced by 532nm pumped Nd:YAG tunable pulsed laser with repetition rate of 20Hz and pulse width of 10ns is performed. The time-resolved photoacoustic signals of glucose solution induced by pulsed laser in the average time of 512 are obtained. And the photoacoustic experiments of different concentrations of glucose solutions and different wavelengths of pulsed laser are carried out in this paper. Experimental results demonstrate that the bipolar sine-wave profiles for the time-resolved photoacoustic signal of glucose solution are in good agreement with the past reported literatures. And the different absorbing coefficients of glucose solution can be gotten according to the slope of the first part of the time-resolved photoacoustic signals. In addition, the different acoustic velocities of glucose solution can also be gotten according to the shift change of the time-resolved photoacoustic peak values. Research results illustrate that the characteristic wavelengths, different optical and acoustic properties of glucose solution can be interpreted by the time-resolved and peak-to-peak photoacoustic signals induced by the pulsed laser.

  3. On-Line Wavelength Calibration of Pulsed Laser for CO2 Differential Absorption LIDAR

    NASA Astrophysics Data System (ADS)

    Xiang, Chengzhi; Ma, Xin; Han, Ge; Liang, Ailin; Gong, Wei

    2016-06-01

    Differential absorption lidar (DIAL) remote sensing is a promising technology for atmospheric CO2 detection. However, stringent wavelength accuracy and stability are required in DIAL system. Accurate on-line wavelength calibration is a crucial procedure for retrieving atmospheric CO2 concentration using the DIAL, particularly when pulsed lasers are adopted in the system. Large fluctuations in the intensities of a pulsed laser pose a great challenge for accurate on-line wavelength calibration. In this paper, a wavelength calibration strategy based on multi-wavelength scanning (MWS) was proposed for accurate on-line wavelength calibration of a pulsed laser for CO2 detection. The MWS conducted segmented sampling across the CO2 absorption line with appropriate number of points and range of widths by using a tunable laser. Complete absorption line of CO2 can be obtained through a curve fitting. Then, the on-line wavelength can be easily found at the peak of the absorption line. Furthermore, another algorithm called the energy matching was introduced in the MWS to eliminate the backlash error of tunable lasers during the process of on-line wavelength calibration. Finally, a series of tests was conducted to elevate the calibration precision of MWS. Analysis of tests demonstrated that the MWS proposed in this paper could calibrate the on-line wavelength of pulsed laser accurately and steadily.

  4. A New Kind of Laser Microphone Using High Sensitivity Pulsed Laser Vibrometer

    NASA Technical Reports Server (NTRS)

    Wang, Chen-Chia; Trivedi, Sudhir; Jin, Feng; Swaminathan, V.; Prasad, Narasimha S.

    2008-01-01

    We demonstrate experimentally a new kind of laser microphone using a highly sensitive pulsed laser vibrometer. By using the photo-electromotive-force (photo-EMF) sensors, we present data indicating the real-time detection of surface displacements as small as 4 pm.

  5. Gene transfer into mammalian cells by use of a nanosecond pulsed laser-induced stress wave

    NASA Astrophysics Data System (ADS)

    Terakawa, Mitsuhiro; Ogura, Makoto; Sato, Shunichi; Wakisaka, Hitoshi; Ashida, Hiroshi; Uenoyama, Maki; Masaki, Yoshinori; Obara, Minoru

    2004-06-01

    Plasmid DNA has been successfully delivered to mammalian cells by applying a nanosecond pulsed laser-induced stress wave (LISW). Cells exposed to a LISW were selectively transfected with plasmids coding for green fluorescent protein. It was also shown that transient, mild cellular heating (~43 °C) was effective in improving the transfection efficiency.

  6. Time differentiated nuclear resonance spectroscopy coupled with pulsed laser heating in diamond anvil cells.

    PubMed

    Kupenko, I; Strohm, C; McCammon, C; Cerantola, V; Glazyrin, K; Petitgirard, S; Vasiukov, D; Aprilis, G; Chumakov, A I; Rüffer, R; Dubrovinsky, L

    2015-11-01

    Developments in pulsed laser heating applied to nuclear resonance techniques are presented together with their applications to studies of geophysically relevant materials. Continuous laser heating in diamond anvil cells is a widely used method to generate extreme temperatures at static high pressure conditions in order to study the structure and properties of materials found in deep planetary interiors. The pulsed laser heating technique has advantages over continuous heating, including prevention of the spreading of heated sample and/or the pressure medium and, thus, a better stability of the heating process. Time differentiated data acquisition coupled with pulsed laser heating in diamond anvil cells was successfully tested at the Nuclear Resonance beamline (ID18) of the European Synchrotron Radiation Facility. We show examples applying the method to investigation of an assemblage containing ε-Fe, FeO, and Fe3C using synchrotron Mössbauer source spectroscopy, FeCO3 using nuclear inelastic scattering, and Fe2O3 using nuclear forward scattering. These examples demonstrate the applicability of pulsed laser heating in diamond anvil cells to spectroscopic techniques with long data acquisition times, because it enables stable pulsed heating with data collection at specific time intervals that are synchronized with laser pulses. PMID:26628151

  7. Time differentiated nuclear resonance spectroscopy coupled with pulsed laser heating in diamond anvil cells

    SciTech Connect

    Kupenko, I. Strohm, C.; McCammon, C.; Cerantola, V.; Petitgirard, S.; Dubrovinsky, L.; Glazyrin, K.; Vasiukov, D.; Aprilis, G.; Chumakov, A. I.; Rüffer, R.

    2015-11-15

    Developments in pulsed laser heating applied to nuclear resonance techniques are presented together with their applications to studies of geophysically relevant materials. Continuous laser heating in diamond anvil cells is a widely used method to generate extreme temperatures at static high pressure conditions in order to study the structure and properties of materials found in deep planetary interiors. The pulsed laser heating technique has advantages over continuous heating, including prevention of the spreading of heated sample and/or the pressure medium and, thus, a better stability of the heating process. Time differentiated data acquisition coupled with pulsed laser heating in diamond anvil cells was successfully tested at the Nuclear Resonance beamline (ID18) of the European Synchrotron Radiation Facility. We show examples applying the method to investigation of an assemblage containing ε-Fe, FeO, and Fe{sub 3}C using synchrotron Mössbauer source spectroscopy, FeCO{sub 3} using nuclear inelastic scattering, and Fe{sub 2}O{sub 3} using nuclear forward scattering. These examples demonstrate the applicability of pulsed laser heating in diamond anvil cells to spectroscopic techniques with long data acquisition times, because it enables stable pulsed heating with data collection at specific time intervals that are synchronized with laser pulses.

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

    SciTech Connect

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

    1998-01-01

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

  9. Method for laser welding a fin and a tube

    DOEpatents

    Fuerschbach, Phillip W.; Mahoney, A. Roderick; Milewski, John O

    2001-01-01

    A method of laser welding a planar metal surface to a cylindrical metal surface is provided, first placing a planar metal surface into approximate contact with a cylindrical metal surface to form a juncture area to be welded, the planar metal surface and cylindrical metal surface thereby forming an acute angle of contact. A laser beam, produced, for example, by a Nd:YAG pulsed laser, is focused through the acute angle of contact at the juncture area to be welded, with the laser beam heating the juncture area to a welding temperature to cause welding to occur between the planar metal surface and the cylindrical metal surface. Both the planar metal surface and cylindrical metal surface are made from a reflective metal, including copper, copper alloys, stainless steel alloys, aluminum, and aluminum alloys.

  10. The technology and welding joint properties of hybrid laser-tig welding on thick plate

    NASA Astrophysics Data System (ADS)

    Shenghai, Zhang; Yifu, Shen; Huijuan, Qiu

    2013-06-01

    The technologies of autogenous laser welding and hybrid laser-TIG welding are used on thick plate of high strength lower alloy structural steel 10CrNiMnMoV in this article. The unique advantages of hybrid laser-TIG welding is summarized by comparing and analyzing the process parameters and welding joints of autogenous laser welding laser welding and hybrid laser-TIG welding. With the optimal process parameters of hybrid welding, the good welding joint without visible flaws can be obtained and its mechanical properties are tested according to industry standards. The results show that the hybrid welding technology has certain advantages and possibility in welding thick plates. It can reduce the demands of laser power, and it is significant for lowering the aspect ratio of weld during hybrid welding, so the gas in the molten pool can rise and escape easily while welding thick plates. Therefore, the pores forming tendency decreases. At the same time, hybrid welding enhances welding speed, and optimizes the energy input. The transition and grain size of the microstructure of hybrid welding joint is better and its hardness is higher than base material. Furthermore, its tensile strength and impact toughness is as good as base material. Consequently, the hybrid welding joint can meet the industry needs completely.

  11. Ultrasonic vibration aided laser welding of Al alloys: Improvement of laser-welding quality

    SciTech Connect

    Kim, J.S.; Watanabe, T.; Yoshida, Y.

    1995-03-01

    Using a pulsed YAG laser, meltability of Al-Mg and Al-Mg-Si alloys were investigated by a single-pass irradiation. In order to improve the quality in laser welding, the effectiveness of the Ultrasonic Vibration Laser Welding (UVLW) method proposed in this paper was investigated experimentally. The proposed method was also compared with the traditional welding methods of Normal Laser Welding (NLW) and preHeating Laser Welding (HLW). The welding methods were evaluated from the geometry in the melt zone generated by a single pulse of the laser beam. It was suggested that ultrasonic vibration suppressed welding defects and improved the melt characteristics due to cavitation effects and dispersion of particles in the molten pool during laser welding. The influence on melt characteristics of the melt zone by preheating was also investigated. In these experiments, UVLW was the most useful laser welding method from the point of view of improving the laser welding quality of Al alloys.

  12. DESIGN NOTE: A video synchronization unit for capture of pulsed laser parameters

    NASA Astrophysics Data System (ADS)

    Oak, S. M.; Navathe, C. P.

    1996-04-01

    An electronic circuit called a video synchronization unit (VSU) is developed to synchronize TV grade CCTV cameras, CCTV monitors and video frame grabbers for the capture of pulsed laser parameters. The VSU accepts a video signal from the camera and generates triggers for the laser and frame grabber at required times. It also generates a trigger at any pre-set horizontal line in the video signal, so that the intensity profile of the selected line can be viewed on an oscilloscope. The unit can drive a laser or be driven by the laser either in single-shot or in repetitive mode of operation. With the help of this unit, a video system is built for the capture of pulsed laser beam profiles and fluorescence traces of a picosecond autocorrelator. It is an inexpensive and more readily available alternative to commercial asynchronous video systems.

  13. Ultra-short pulse laser deep drilling of C/SiC composites in air

    NASA Astrophysics Data System (ADS)

    Wang, Chunhui; Zhang, Litong; Liu, Yongsheng; Cheng, Guanghua; Zhang, Qing; Hua, Ke

    2013-06-01

    Ultra-short pulse laser machining is an important finishing technology for high hardness materials. In this study, it demonstrated that the ultra-short pulse laser can be used to drill the film cooling holes and square holes in aero-engine turbine blades made of C/SiC composites. Both the edges and bottoms of the drilling holes are covered with small particles. The following factors have a great effect on drilling holes according to this work: (1) circular holes can be processed only at a relative small helical lines spacing. (2) With the increase of laser scanning speed, the depth of holes reduces while the diameter rarely changes. (3) Through the holes of high aspect ratio can be obtained via high processing power.

  14. Comparison study of the charge density distribution induced by heavy ions and pulsed lasers in silicon

    NASA Astrophysics Data System (ADS)

    Tian, Kai; Cao, Zhou; Xue, Yu-Xiong; Yang, Shi-Yu

    2010-01-01

    Heavy ions and pulsed lasers are important means to simulate the ionization damage effects on semiconductor materials. The analytic solution of high-energy heavy ion energy loss in silicon has been obtained using the Bethe-Bloch formula and the Kobetich-Katz theory, and some ionization damage parameters of Fe ions in silicon, such as the track structure and ionized charge density distribution, have been calculated and analyzed according to the theoretical calculation results. Using the Gaussian function and Beer's law, the parameters of the track structure and charge density distribution induced by a pulsed laser in silicon have also been calculated and compared with those of Fe ions in silicon, which provides a theoretical basis for ionization damage effect modeling.

  15. Numerical modeling of pulsed laser-material interaction and of laser plume dynamics

    SciTech Connect

    Zhao, Qiang; Shi, Yina

    2015-03-10

    We have developed two-dimensional Arbitrary Lagrangian Eulerian (ALE) code which is used to study the physical processes, the plasma absorption, the crater profile, and the temperature distribution on metallic target and below the surface. The ALE method overcomes problems with Lagrangian moving mesh distortion by mesh smoothing and conservative quantities remapping from Lagrangian mesh to smoothed one. A new second order accurate diffusion solver has been implemented for the thermal conduction and radiation transport on distorted mesh. The results of numerical simulation of pulsed laser ablation are presented. The influences of different processes, such as time evolution of the surface temperature, interspecies interactions (elastic collisions, recombination-dissociation reaction), interaction with an ambient gas are examined. The study presents particular interest for the analysis of experimental results obtained during pulsed laser ablation.

  16. Comparison of threshold transient upset levels induced by flash x-rays and pulsed lasers

    SciTech Connect

    Raburn, W.D.; Buchner, S.P.; Kang, K.; Singh, R.; Sayers, S.

    1988-12-01

    The use of pulsed laser testing as a method of evaluating the transient radiation (..gamma..) upset thresholds of integrated circuits is discussed. By comparing upset levels using a pulsed laser with those obtained using a flash x-ray which has long been accepted ..gamma.. simulator, we show that the laser can be used as a reliable source for 100% screening and also as an efficient development tool. Differences in the responses of the two sources are pointed out, and we show that upset levels of CMOS SRAMs using the two sources are in good agreement when these factors are taken into account. Results for both wafer level and packaged parts testing are presented.

  17. Characterization of Environmental Stability of Pulsed Laser Deposited Oxide Ceramic Coatings

    SciTech Connect

    ADAMS, THADM

    2004-03-02

    A systematic investigation of candidate hydrogen permeation materials applied to a substrate using Pulsed Laser Deposition has been performed. The investigation focused on application of leading permeation-resistant materials types (oxide, carbides, and metals) on a stainless steel substrate. and evaluation of the stability of the applied coatings. Type 304L stainless steel substrates were coated with aluminum oxide, chromium oxide, and aluminum. Characterization of the coating-substrate system adhesion was performed using scratch adhesion testing and microindentation. Coating stability and environmental susceptibility were evaluated for two conditions-air at 350 degrees Celsius and Ar-H2 at 350 degrees Celsius for up to 100 hours. Results from this study have shown the pulsed laser deposition process to be an extremely versatile technology that is capable of producing a sound coating/substrate system for a wide variety of coating materials.

  18. Biomolecular papain thin films grown by matrix assisted and conventional pulsed laser deposition: A comparative study

    NASA Astrophysics Data System (ADS)

    György, E.; Pérez del Pino, A.; Sauthier, G.; Figueras, A.

    2009-12-01

    Biomolecular papain thin films were grown both by matrix assisted pulsed laser evaporation (MAPLE) and conventional pulsed laser deposition (PLD) techniques with the aid of an UV KrF∗ (λ =248 nm, τFWHM≅20 ns) excimer laser source. For the MAPLE experiments the targets submitted to laser radiation consisted on frozen composites obtained by dissolving the biomaterial powder in distilled water at 10 wt % concentration. Conventional pressed biomaterial powder targets were used in the PLD experiments. The surface morphology of the obtained thin films was studied by atomic force microscopy and their structure and composition were investigated by Fourier transform infrared spectroscopy. The possible physical mechanisms implied in the ablation processes of the two techniques, under comparable experimental conditions were identified. The results showed that the growth mode, surface morphology as well as structure of the deposited biomaterial thin films are determined both by the incident laser fluence value as well as target preparation procedure.

  19. Two-color short-pulse laser altimeter measurements of ocean surface backscatter.

    PubMed

    Abshire, J B; McGarry, J F

    1987-04-01

    The timing and correlation properties of pulsed laser backscatter from the ocean surface have been measured with a two-color short-pulse laser altimeter. The Nd: YAG laser transmitted 70-and 35-ps wide pulses simultaneously at 532 and 355 nm at nadir, and the time-resolved returns were recorded by a receiver with 800-ps response time. The time-resolved backscatter measured at both 330- and 1291-m altitudes showed little pulse broadening due to the submeter laser spot size. The differential delay of the 355- and 532-nm backscattered waveforms were measured with a rms error of ~75 ps. The change in aircraft altitudes also permitted the change in atmospheric pressure to be estimated by using the two-color technique. PMID:20454319

  20. Method for controlling energy density for reliable pulsed laser deposition of thin films

    SciTech Connect

    Dowden, P. C. E-mail: qxjia@lanl.gov; Bi, Z.; Jia, Q. X. E-mail: qxjia@lanl.gov

    2014-02-15

    We have established a methodology to stabilize the laser energy density on a target surface in pulsed laser deposition of thin films. To control the focused laser spot on a target, we have imaged a defined aperture in the beamline (so called image-focus) instead of focusing the beam on a target based on a simple “lens-focus.” To control the laser energy density on a target, we have introduced a continuously variable attenuator between the output of the laser and the imaged aperture to manipulate the energy to a desired level by running the laser in a “constant voltage” mode to eliminate changes in the lasers’ beam dimensions. This methodology leads to much better controllability/reproducibility for reliable pulsed laser deposition of high performance electronic thin films.

  1. Underwater pulsed laser range-gated imaging model and its effect on image degradation and restoration

    NASA Astrophysics Data System (ADS)

    Youwei, Huang; Fengmei, Cao; Weiqi, Jin; Su, Qiu

    2014-06-01

    The imaging of underwater objects illuminated by artificial light has been of long-standing interest to investigators working in oceanographic environments. Pulsed lasers together with range-gated technology have been widely used for underwater optical imaging applications. In order to describe the formation of underwater range-gated images, a pulsed laser underwater imaging model based on pulse spatial and temporal broadening is proposed. Experiments based on a self-assembled laser range-gated imaging system were implemented in our laboratory. Results show good agreements between experiments and simulations. Both results also confirm higher image contrast toward the tail region of the target-reflected light. Furthermore, experiments on underwater image blur and restoration are also implemented and show good image recovery results. The modulation transfer function-based restoration mechanism also implies a way to eliminate the blur effect caused by light forward scattering.

  2. Cytotoxical products formation on the nanoparticles heated by the pulsed laser radiation

    NASA Astrophysics Data System (ADS)

    Kogan, Boris Ya.; Titov, Andrey A.; Rakitin, Victor Yu.; Kvacheva, Larisa D.; Kuzmin, Sergey G.; Vorozhtsov, Georgy N.

    2006-02-01

    Cytotoxical effect of a pulsed laser irradiation in presence of nanoparticles of carbon black, sulphuretted carbon and fullerene-60 on death of human uterus nick cancer HeLa and mice lymphoma P 388 cells was studied in vitro. Bubbles formation as result of "microexplosions" of nanoparticles is one of possible mechanisms of this effect. Other possible mechanism is cytotoxical products formation in result of pyrolysis of nanoparticles and biomaterial which is adjoining. The cytotoxical effect of addition of a supernatant from the carbon nanoparticles suspensions irradiated by the pulsed laser was studied to test this assumption. Analysis using gas chromatograph determined that carbon monoxide is principal gaseous product of such laser pyrolysis. This is known as cytotoxical product. Efficiency of its formation is estimated.

  3. Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO2

    NASA Astrophysics Data System (ADS)

    Nakahara, Sho; Stauss, Sven; Kato, Toru; Sasaki, Takehiko; Terashima, Kazuo

    2011-06-01

    Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm2; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO2 with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3-hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography-mass spectrometry. Furthermore, gas chromatography-mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO2 during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO2 is proposed as a practical method for synthesizing diamondoids.

  4. Properties of defect-induced multiple pulse laser damage of transmission components.

    PubMed

    Ma, Bin; Zhang, Li; Lu, Menglei; Wang, Ke; Jiao, Hongfei; Zhang, Jinlong; Cheng, Xinbin; Yang, Liming; Wang, Zhanshan

    2016-09-01

    When the number of laser pulses increases, the laser-induced damage threshold of the optical components gradually declines. The magnitude and tendency of this reduced threshold are associated with various factors. Furthermore, this reduced threshold is conclusively determined by the limiting factors or defect characteristics that trigger damage to optical components. Then, fully understanding the damage properties of different kinds of defects will contribute to the optimization of the performance and lifetime of the optical components. In this study, the statistical and deterministic characterizations of the fatigue effect are used to evaluate the properties of the multiple pulse laser damage of transmission components. First, the influence of spot sizes and polishing materials on the properties of the multiple pulse laser damage of optical components is discussed. Then, the structural, absorptive, and mixed artificial defects are fabricated, and the damage characteristics are evaluated and analyzed. Finally, the damage mechanism of different factors has been clarified. PMID:27607284

  5. Fiber Bragg grating Fabry-Perot cavity sensor based on pulse laser demodulation technique

    NASA Astrophysics Data System (ADS)

    Gao, Fangfang; Chen, Jianfeng; Liu, Yunqi; Wang, Tingyun

    2011-12-01

    We demonstrate a fiber laser sensing technique based on fiber Bragg grating Fabry-Perot (FBG-FP) cavity interrogated by pulsed laser, where short pulses generated from active mode-locked erbium-doped fiber ring laser and current modulated DFB laser are adopted. The modulated laser pulses launched into the FBG-FP cavity produce a group of reflected pulses. The optical loss in the cavity can be determined from the power ratio of the first two pulses reflected from the cavity. This technique does not require high reflectivity FBGs and is immune to the power fluctuation of the light source. Two short pulse laser sources were compared experimentally with each other on pulse width, pulse stability, pulse chirp and sensing efficiency.

  6. Simulation studies of vapor bubble generation by short-pulse lasers

    SciTech Connect

    Amendt, P.; London, R.A.; Strauss, M.

    1997-10-26

    Formation of vapor bubbles is characteristic of many applications of short-pulse lasers in medicine. An understanding of the dynamics of vapor bubble generation is useful for developing and optimizing laser-based medical therapies. To this end, experiments in vapor bubble generation with laser light deposited in an aqueous dye solution near a fiber-optic tip have been performed. Numerical hydrodynamic simulations have been developed to understand and extrapolate results from these experiments. Comparison of two-dimensional simulations with the experiment shows excellent agreement in tracking the bubble evolution. Another regime of vapor bubble generation is short-pulse laser interactions with melanosomes. Strong shock generation and vapor bubble generation are common physical features of this interaction. A novel effect of discrete absorption by melanin granules within a melanosome is studied as a possible role in previously reported high Mach number shocks.

  7. Improved passivation of the ZnO/Si interface by pulsed laser deposition

    SciTech Connect

    Gluba, M. A.; Nickel, N. H.; Rappich, J.; Hinrichs, K.

    2013-01-28

    Zinc oxide thin-films were grown on crystalline silicon employing magnetron sputtering and pulsed laser deposition. Bulk and interface properties were investigated using scanning electron microscopy, Raman backscattering, photoluminescence, and infrared spectroscopic ellipsometry. Sputter deposited ZnO samples reveal a large degree of disorder and an interface defect density of Almost-Equal-To 10{sup 12} cm{sup -2}. A significant improvement of the structural quality is observed in samples grown by pulsed laser deposition. The bulk defect density is further reduced, when introducing monatomic oxygen during deposition. Simultaneously, the defect density at the ZnO/Si interface decreases by about a factor of five. Implications for devices containing ZnO/Si interfaces are discussed.

  8. Blue luminescent silicon nanocrystals prepared by short pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Švrček, Vladimir; Kondo, Michio

    2009-09-01

    The pulsed laser processing in liquid media is an attractive alternative to produce room temperature luminescent silicon nanocrystals (Si-ncs). We report on a blue luminescent Si-ncs preparation by using nanosecond pulsed laser (Nd:YAG, KrF excimer) processing in transparent polymer and water. The Si-ncs fabrication is assured by ablation of crystalline silicon target immersed in liquids. During the processing and following aging in liquids, oxide based liquid media, induce shell formation around fresh nanocrystals that provides a natural and stable form of surface passivation. The stable room temperature blue-photoluminescent Si-ncs are prepared with maxima located around ˜440 nm with corresponding optical band gap around ˜2.8 eV (˜430 nm). Due to the reduction of surface defects, the Si-ncs preparation in water, leads to a narrowing of full-width-half-maxima of the photoluminescence spectra.

  9. Electron acceleration in relativistic plasma waves generated by a single frequency short-pulse laser

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Decker, C.D.; Mori, W.B.; Tzeng, K.C., Clayton, C.E.; Marsh, K.A.; Joshi, C.

    1995-04-27

    Experimental evidence for the acceleration of electrons in a relativistic plasma wave generated by Raman forward scattering (SRS-F) of a single-frequency short pulse laser are presented. A 1.053 {mu}m, 600 fsec, 5 TW laser was focused into a gas jet with a peak intensity of 8{times}10{sup 17} W/cm{sup 2}. At a plasma density of 2{times}10{sup 19} cm{sup {minus}3}, 2 MeV electrons were detected and their appearance was correlated with the anti-Stokes laser sideband generated by SRS-F. The results are in good agreement with 2-D PIC simulations. The use of short pulse lasers for making ultra-high gradient accelerators is explored.

  10. Crystallization kinetics of GeTe phase-change thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Sun, Xinxing; Thelander, Erik; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd

    2015-07-01

    Pulsed laser deposition was employed to the growth of GeTe thin films on Silicon substrates. X-ray diffraction measurements reveal that the critical crystallization temperature lies between 220 and 240 °C. Differential scanning calorimetry was used to investigate the crystallization kinetics of the as-deposited films, determining the activation energy to be 3.14 eV. Optical reflectivity and in situ resistance measurements exhibited a high reflectivity contrast of ~21% and 3-4 orders of magnitude drop in resistivity of the films upon crystallization. The results show that pulsed laser deposited GeTe films can be a promising candidate for phase-change applications.

  11. How to optimize ultrashort pulse laser interaction with glass surfaces in cutting regimes?

    NASA Astrophysics Data System (ADS)

    Bulgakova, Nadezhda M.; Zhukov, Vladimir P.; Collins, Adam R.; Rostohar, Danijela; Derrien, Thibault J.-Y.; Mocek, Tomáš

    2015-05-01

    The interaction of short and ultrashort pulse laser radiation with glass materials is addressed. Particular attention is paid to regimes which are important in industrial applications such as laser cutting, drilling, functionalization of material surfaces, etc. Different factors influencing the ablation efficiency and quality are summarized and their importance is illustrated experimentally. The effects of ambient gas ionization in front of the irradiated target are also analyzed. A possibility to enhance laser coupling with transparent solids by bi-wavelength irradiation is discussed.

  12. Single-pulse, laser-saturated fluorescence measurements of OH in turbulent nonpremixed flames

    NASA Technical Reports Server (NTRS)

    Lucht, R. P.; Sweeney, D. W.; Laurendeau, N. M.; Drake, M. C.; Lapp, M.; Pitz, R. W.

    1984-01-01

    A single-pulse, laser-saturated fluorescence technique has been developed for absolute OH concentration measurements with a temporal resolution of 2 nsec, a spatial resolution of less than 0.1 cu mm, and an estimated accuracy of + or - 30 percent. It has been applied in laminar, transitional, and turbulent hydrogen-air diffusion flames, providing the first reported quantitative measurements of average values, rms fluctuations, and probability-density functions of OH-radical concentration in nonpremixed flames.

  13. Simulated electronic heterodyne recording and processing of pulsed-laser holograms

    NASA Technical Reports Server (NTRS)

    Decker, A. J.

    1979-01-01

    The electronic recording of pulsed-laser holograms is proposed. The polarization sensitivity of each resolution element of the detector is controlled independently to add an arbitrary phase to the image waves. This method which can be used to simulate heterodyne recording and to process three-dimensional optical images, is based on a similar method for heterodyne recording and processing of continuous-wave holograms.

  14. Enhanced localized superconductivity in Sr2RuO4 thin film by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Cao, J.; Massarotti, D.; Vickers, M. E.; Kursumovic, A.; Di Bernardo, A.; Robinson, J. W. A.; Tafuri, F.; MacManus-Driscoll, J. L.; Blamire, M. G.

    2016-09-01

    Superconducting c-axis-oriented Sr2RuO4 thin film has been fabricated using pulsed laser deposition. Although the superconductivity is localized, the onset critical temperature is enhanced over the bulk value. X-ray microstructural analysis of Sr2RuO4 superconducting and non-superconducting thin films suggests the existence of the localized stacking faults and an overall c-axis lattice expansion which may account for the locally enhanced superconductivity.

  15. Simple Laser-Ultrasonic System Using a Single-Frequency Pulsed Laser Oscillator

    NASA Astrophysics Data System (ADS)

    Blouin, A.; Carrion, L.; Padioleau, C.; Bouchard, P.; Monchalin, J.-P.

    2005-04-01

    We present a new pulsed laser oscillator and system for the optical detection of ultrasound in materials using a flashlamp-pumped dual Nd:YAG rod configuration. A single-frequency laser oscillator based on one rod inside a ring cavity is proposed. The second rod can be used as an amplifier for the oscillator or as a generation laser. Performance of the system is investigated with a two-wave mixing phase demodulator. Tests on metallic samples are presented.

  16. Propagating Properties of Cylindrical Rayleigh Waves Generated by a Pulsed Laser Line Source

    NASA Astrophysics Data System (ADS)

    Hu, Wen-Xiang; Qian, Meng-Lu

    2004-07-01

    A two-dimensional theoretical model is used to analyse the acoustic field of cylindrical surface waves generated by a pulsed laser line source in the ablation regime. The complete dispersive curves for cylindrical Rayleigh wave are presented. The laser-generated transient acoustic field of cylindrical Rayleigh waves is calculated and the corresponding laser ultrasonic experiments are carried out. Both the numerical and experimental results are in good agreement.

  17. Surface roughness and wettability of dentin ablated with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Lü, Peijun; Sun, Yuchun; Wang, Yong

    2015-05-01

    The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore, significantly alter dentin surface roughness and wettability.

  18. Laser cleaning of rust on ship steel using TEA CO2 pulsed laser

    NASA Astrophysics Data System (ADS)

    Ke, Linda; Zhu, Haihong; Lei, Wenjuan; Cheng, Zuhai

    2009-08-01

    Ship is easy to rust because of its special working condition. Removal of the rust from the ship surface is generally required for maintaining ship. The feasibility of removing rust using pulsed laser has been confirmed by the past researches. However, the general utilized laser, e.g., pulsed Nd: YAG laser with narrow pulse duration and high peak power, suffers very low average power and throughput. TEA CO2 laser, which also has narrow pulse duration and high peak power, is expected to obtain high throughout because it is easy to obtain high average power. This paper investigated the feasibility and the efficiency of removal of rust from the ship steel using TEA CO2 pulsed laser. The results show that TEA CO2 pulsed laser can effectively clean the rust by using suitable parameters without damage the substrate. A cleaning threshold for stripping rust of power density exists. Also, the effect of the process parameters on the efficiency and performance as well as the removal mechanism were studied in this paper.

  19. Quantitative analysis of arsenic in mine tailing soils using double pulse-laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Kwak, Ji-hyun; Lenth, Christoph; Salb, Christian; Ko, Eun-Joung; Kim, Kyoung-Woong; Park, Kihong

    2009-10-01

    A double pulse-laser induced breakdown spectroscopy (DP-LIBS) was used to determine arsenic (As) concentration in 16 soil samples collected from 5 different mine tailing sites in Korea. We showed that the use of double pulse laser led to enhancements of signal intensity (by 13% on average) and signal-to-noise ratio of As emission lines (by 165% on average) with smaller relative standard deviation compared to single pulse laser approach. We believe this occurred because the second laser pulse in the rarefied atmosphere produced by the first pulse led to the increase of plasma temperature and populations of exited levels. An internal standardization method using a Fe emission line provided a better correlation and sensitivity between As concentration and the DP-LIBS signal than any other elements used. The Fe was known as one of the major components in current soil samples, and its concentration varied not substantially. The As concentration determined by the DP-LIBS was compared with that obtained by atomic absorption spectrometry (AAS) to evaluate the current LIBS system. They are correlated with a correlation coefficient of 0.94. The As concentration by the DP-LIBS was underestimated in the high concentration range (>1000 mg-As/kg). The loss of sensitivity that occurred at high concentrations could be explained by self-absorption in the generated plasma.

  20. Electron-nucleus scattering at small angles in the field of a pulsed laser wave

    NASA Astrophysics Data System (ADS)

    Lebed', A. A.

    2016-04-01

    We study scattering of an electron by a screened potential of a nucleus in the field of a pulsed laser wave at small scattering angles. The interaction of an electron with the field of a nucleus is considered in the first Born approximation. An external field of a pulsed laser is accounted accurately as a quasimonochromatic wave. Analytical expressions are obtained for the transition amplitude and the cross section of the considered process. Scattering kinematics is defined at the minimal value of a transferred momentum. In this case the cross section contains a peak near the preferred scattering direction. It is shown that the maximum value of the cross section is determined by both the initial-electron energy and the energy of an external-field photon. Thus, the cross section of electron-nucleus scattering in a pulsed laser field can exceed in two orders of magnitude the cross section in absence of an external field in the case of ultrarelativistic energies and external field of a free-electron laser with keV-order photon energy.

  1. Nanoalloy Printed and Pulse-Laser Sintered Flexible Sensor Devices with Enhanced Stability and Materials Compatibility

    SciTech Connect

    Zhao, Wei; Rovore, Thomas; Weerawarne, Darshana; Osterhoudt, Gavin; Kang, Ning; Joseph, Pharrah; Luo, Jin; Shim, Bonggu; Poliks, Mark; Zhong, Chuan-Jian

    2015-06-02

    While conformal and wearable devices have become one of the most desired formats for printable electronics, it is challenging to establish a scalable process that produces stable conductive patterns but also uses substrates compatible with widely available wearable materials. Here, we describe findings of an investigation of a nanoalloy ink printed and pulsed laser sintered conductive patterns as flexible functional devices with enhanced stability and materials compatibility. While nanoparticle inks are desired for printable electronics, almost all existing nanoparticle inks are based on single-metal component, which, as an electronic element, is limited by its inherent stabilities of the metal such as propensity of metal oxidation and mobility of metal ions, especially in sintering processes. The work here has demonstrated the first example in exploiting plasmonic coupling of nanoalloys and pulsed-laser energy with controllable thermal penetration. The experimental and theoretical results have revealed clear correlation between the pulsed laser parameters and the nanoalloy structural characteristics. The superior performance of the resulting flexible sensor device, upon imparting nanostructured sensing materials, for detecting volatile organic compounds has significant implications to developing stable and wearable sensors for monitoring environmental pollutants and breath biomarkers. This simple “nanoalloy printing 'laser sintering' nanostructure printing” process is entirely general to many different sensor devices and nanostructured sensing materials, enabling the ability to easily construct sophisticated sensor array.

  2. Ultra-short pulsed laser tissue ablation using focused laser beam

    NASA Astrophysics Data System (ADS)

    Jaunich, Megan K.; Raje, Shreya; Mitra, Kunal; Grace, Michael S.; Fahey, Molly; Spooner, Greg

    2008-02-01

    Short pulse lasers are used for a variety of therapeutic applications in medicine. Recently ultra-short pulse lasers have gained prominence due to the reduction in collateral thermal damage to surrounding healthy tissue during tissue ablation. In this paper, ultra-short pulsed laser ablation of mouse skin tissue is analyzed by assessing the extent of damage produced due to focused laser beam irradiation. The laser used for this study is a fiber-based desktop laser (Raydiance, Inc.) having a wavelength of 1552 nm and a pulse width of 1.3 ps. The laser beam is focused on the sample surface to a spot size on the order of 10 microns, thus producing high peak intensity necessary for precise clean ablation. A parametric study is performed on in vitro mouse tissue specimens and live anaesthetized mice with mammary tumors through variation of laser parameters such as time-averaged laser power, repetition rate, laser scanning rate and irradiation time. Radial temperature distribution is measured using thermal camera to analyze the heat affected zone. Temperature measurements are performed to assess the peak temperature rise attained during ablation. A detailed histological study is performed using frozen section technique to observe the nature and extent of laser-induced damages.

  3. Targeted gene transfer into rat facial muscles by nanosecond pulsed laser-induced stress waves.

    PubMed

    Kurita, Akihiro; Matsunobu, Takeshi; Satoh, Yasushi; Ando, Takahiro; Sato, Shunichi; Obara, Minoru; Shiotani, Akihiro

    2011-09-01

    We investigate the feasibility of using nanosecond pulsed laser-induced stress waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis. PMID:21950944

  4. Experimental investigations and statistical analysis of pulsed laser bending of AISI 304 stainless steel sheet

    NASA Astrophysics Data System (ADS)

    Maji, Kuntal; Pratihar, D. K.; Nath, A. K.

    2013-07-01

    This paper presents experimental investigations on pulsed laser bending of sheet metal and statistical analysis to study the effects of process parameters. Laser power, scan speed, spot diameter and pulsed duration were taken as input variables and bending angle was considered as the output. Response surface methodology was used for modeling and optimization of the pulsed laser bending process. The performance of the developed model was validated through the experiments. All the input variables were found to have significant influence on the bending angle. Bending angle increased with the increase of laser power and pulse duration and decreased with the increase of scan speed and spot diameter. The optimum process parameters for the maximum bending angle were also found and verified with experimental data. The effects of pulse frequency, pulse width and pulse energy on bending angle were also investigated through experiments. Bending angle was found to be the maximum for a certain value of pulse frequency. With the increase of pulse width, bending angle increased at constant laser power but decreased at constant pulse energy. Bending angle was seen to increase with the increase of spatial overlapping and decrease with the increase of gap at constant laser power, but it showed optimal values for both the cases at constant line energy. A comparative study between continuous and pulsed laser bending was carried out to study the process efficiency in terms of energy input and produced deformation.

  5. Influence trend of temperature distribution in skin tissue generated by different exposure dose pulse laser

    NASA Astrophysics Data System (ADS)

    Shan, Ning; Wang, Zhijing; Liu, Xia

    2014-11-01

    Laser is widely applied in military and medicine fields because of its excellent capability. In order to effectively defend excess damage by laser, the thermal processing theory of skin tissue generated by laser should be carried out. The heating rate and thermal damage area should be studied. The mathematics model of bio-tissue heat transfer that is irradiated by laser is analyzed. And boundary conditions of bio-tissue are discussed. Three layer FEM grid model of bio-tissue is established. The temperature rising inducing by pulse laser in the tissue is modeled numerically by adopting ANSYS software. The changing trend of temperature in the tissue is imitated and studied under the conditions of different exposure dose pulse laser. The results show that temperature rising in the tissue depends on the parameters of pulse laser largely. In the same conditions, the pulse width of laser is smaller and its instant power is higher. And temperature rising effect in the tissue is very clear. On the contrary, temperature rising effect in the tissue is lower. The cooling time inducing by temperature rising effect in the tissue is longer along with pulse separation of laser is bigger. And the temperature difference is bigger in the pulse period.

  6. Nd:YAG Pulsed Laser based flaw imaging techniques for noncontact NDE of an aluminum plate

    NASA Astrophysics Data System (ADS)

    Park, Woong-Ki; Lee, Changgil; Park, Seunghee

    2012-04-01

    Recently, the longitudinal, shear and surface waves have been very widely used as a kind of ultrasonic wave exploration methods to identify internal defects of metallic structures. The ultrasonic wave-based non-destructive testing (NDT) is one of main non-destructive inspection techniques for a health assessment about nuclear power plant, aircraft, ships, and/or automobile manufacturing. In this study, a noncontact pulsed laser-based flaw imaging NDT technique is implemented to detect the damage of a plate-like structure and to identify the location of the damage. To achieve this goal, the Nd:YAG pulsed laser equipment is used to generate a guided wave and scans a specific area to find damage location. The Nd: YAG pulsed laser is used to generate Lamb wave and piezoelectric sensors are installed to measure structural responses. Ann aluminum plate is investigated to verify the effectiveness and the robustness of the proposed NDT approach. A notch is a target to detect, which is inflicted on the surface of an aluminum plate. The damagesensitive features are extracted by comparing the time of flight of the guided wave obtained from an acoustic emission (AE) sensor and make use of the flaw imaging techniques of the aluminum plate.

  7. Numerical simulation of different pulse width of long pulsed laser on aluminum alloy

    NASA Astrophysics Data System (ADS)

    Li, Mingxin; Jin, Guangyong; Zhang, Wei; Chen, Guibo; Bi, Juan

    2015-03-01

    Established a physical model to simulate the melt ejection induced by long pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. This simulation is based on the interaction between single pulsed laser with different pulse width and different peak energy and aluminum alloy material. By comparing the theoretical simulation data and the actual test data, we discover that: the theoretical simulation curve is well consistent with the actual experimental curve, this two-dimensional model is with high reliability; when the temperature at the center of aluminum alloy surface increases and evaporation happens after the surface temperature at the center of aluminum alloy surface reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium vaporization; the keyhole appears on the surface of the target, an increment of the keyhole, the maximum temperature at the center of aluminum alloy surface gradually moves inwardly. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.

  8. Targeted gene transfer into rat facial muscles by nanosecond pulsed laser-induced stress waves

    NASA Astrophysics Data System (ADS)

    Kurita, Akihiro; Matsunobu, Takeshi; Satoh, Yasushi; Ando, Takahiro; Sato, Shunichi; Obara, Minoru; Shiotani, Akihiro

    2011-09-01

    We investigate the feasibility of using nanosecond pulsed laser-induced stress waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis.

  9. Subtask 12B2: Development of laser welding techniques for vanadium alloys

    SciTech Connect

    Strain, R.V.; Leong, K.H.; Keppler, E.E.; Smith, D.L.

    1995-03-01

    The development of techniques for joining vanadium alloys will be required for the construction of fusion devices utilizing the desirable properties of these alloys. The primary objective of this program is to develop of laser welding techniques for vanadium alloys, particularly for the manufacture of welded materials testing specimens. Laser welding is potentially advantageous because of its flexibility and the reduced amount of material effected by the weld. Lasers do not require a vacuum (as does electron beam welders) and the welds they produce have large depth-to-width ratios. Results of scoping tests using a small, pulsed laser (50 joule, YAG laser) indicated that lasers could produce successful welds in vanadium alloy (V-5%Cr-5%Ti) sheet (1-mm thick) when the fusion zone was isolated from air. The pulsed laser required an isolating chamber filled with inert gas to produce welds that did not contain cracks and showed only minor hardness increases. Successful bead-on-plate welds have been made to depths of about 4-mm using a 6 kW continuous CO{sub 2} laser with argon purging. 2 figs.

  10. Simulation, part path correction, and automated process parameter selection for ultrashort pulsed laser micromachining of sapphire

    NASA Astrophysics Data System (ADS)

    Blood, Daniel A.

    This dissertation describes an ultrashort pulsed laser material removal simulator with X-Y stage acceleration profile consideration and part path compensation. Ultrashort pulsed lasers offer the advantage of single step processing of various materials with high repeatability. Over the past 30 years the laser repetition rate and power output have increased, and although this increases the material removal rate, it also introduces new challenges. The acceleration rates of the X-Y stages on a laser micromachining setup are finite, but this has been neglected. In the past the acceleration rate has been negligible due to low repetition rates; however, for high repetition rates the acceleration and deceleration regions introduce local variations in the material removal. A novel method is presented that accounts for the stage dynamics to produce a more robust simulated cut. In addition to the simulator, a technique for modifying the part path to reduce non-uniformity in the material removal is discussed. The laser operator has access to a variety of process parameters that ultimately affect the cost and quality of the machined component. Choosing the correct combination of these parameters requires knowledge of the machining process, and the wrong combination can result in a feature that is unsatisfactory and/or overly expensive. The modification of these parameters, and a correction of the part path allows for a more uniform depth of cut and higher feature quality. This dissertation contains three main contributions. The first contribution is to quantify the relationship between ultrashort pulsed laser machining parameters and the ablation depth of sapphire. The second is to produce a pulsed laser micromachining simulator that includes not only the laser-material interaction, but also the nuances of controlling the position of the laser beam on the workpiece. The final contribution is to produce a part path correction program with an automated process parameter routine

  11. Welding Research

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Welding fabrication and welding processes were studied. The following research projects are reported: (1) welding fabrication; (2) residual stresses and distortion in structural weldments in high strength steels; (3) improvement of reliability of welding by in process sensing and control (development of smart welding machines for girth welding of pipes); (4) development of fully automated and integrated welding systems for marine applications; (5) advancement of welding technology; (6) research on metal working by high power laser (7) flux development; (8) heat and fluid flow; (9) mechanical properties developments.

  12. Application of welding science to welding engineering: A lumped parameter gas metal arc welding dynamic process model

    SciTech Connect

    Murray, P.E.; Smartt, H.B.; Johnson, J.A.

    1997-12-31

    We develop a model of the depth of penetration of the weld pool in gas metal arc welding (GMAW) which demonstrates interaction between the arc, filler wire and weld pool. This model is motivated by the observations of Essers and Walter which suggest a relationship between droplet momentum and penetration depth. A model of gas metal arc welding was augmented to include an improved model of mass transfer and a simple model of accelerating droplets in a plasma jet to obtain the mass and momentum of impinging droplets. The force of the droplets and depth of penetration is correlated by a dimensionless linear relation used to predict weld pool depth for a range of values of arc power and contact tip to workpiece distance. Model accuracy is examined by comparing theoretical predictions and experimental measurements of the pool depth obtained from bead on plate welds of carbon steel in an argon rich shielding gas. Moreover, theoretical predictions of pool depth are compared to the results obtained from the heat conduction model due to Christensen et al. which suggest that in some cases the momentum of impinging droplets is a better indicator of the depth of the weld pool and the presence of a deep, narrow penetration.

  13. Evaluation of weld porosity in laser beam seam welds: optimizing continuous wave and square wave modulated processes.

    SciTech Connect

    Ellison, Chad M.; Perricone, Matthew; Faraone, Kevin M. (Honeywell FM&T, Kansas City, MO); Roach, Robert Allen; Norris, Jerome T.

    2007-02-01

    Nd:YAG laser joining is a high energy density (HED) process that can produce high-speed, low-heat input welds with a high depth-to-width aspect ratio. This is optimized by formation of a ''keyhole'' in the weld pool resulting from high vapor pressures associated with laser interaction with the metallic substrate. It is generally accepted that pores form in HED welds due to the instability and frequent collapse of the keyhole. In order to maintain an open keyhole, weld pool forces must be balanced such that vapor pressure and weld pool inertia forces are in equilibrium. Travel speed and laser beam power largely control the way these forces are balanced, as well as welding mode (Continuous Wave or Square Wave) and shielding gas type. A study into the phenomenon of weld pool porosity in 304L stainless steel was conducted to better understand and predict how welding parameters impact the weld pool dynamics that lead to pore formation. This work is intended to aid in development and verification of a finite element computer model of weld pool fluid flow dynamics being developed in parallel efforts and assist in weld development activities for the W76 and future RRW programs.

  14. Electrode formulation to reduce weld metal hydrogen and porosity

    SciTech Connect

    Liu, S.; Olson, D.L.; Ibarra, S.

    1994-12-31

    Residual weld metal hydrogen is a major concern in high strength steel welding, especially when the weld is performed under high cooling rate conditions. In the case of underwater wet welding, weld metal porosity is also of importance because of the water environment. The control of both problems can be achieved by means of pyrochemical reactions in the weld pool. The hydrogen-oxygen reaction and carbon-oxygen reaction are fundamental in the control of residual hydrogen in the weld metal and the amount of gas pores entrapped. A simple model was proposed to estimate weld metal residual hydrogen content by monitoring the weld pool deoxidation reactions. Potent deoxidizers such as aluminum will first react with oxygen in the liquid weld pool, followed by other elements present such as silicon and manganese. Carbon and hydrogen will be the last ones to react with oxygen prior to the iron atoms. The Ellingham-Richardson diagram frequently applied in describing steel and iron making processes was used in the modeling. Following the sequence of deoxidation, the chemical make-up of the gas pores and the amount of each chemical species in the pores could be estimated. Carbon monoxide and hydrogen were determined to be the major components in the weld pores. To minimize the amount of weld metal porosity and residual hydrogen content, specially designed consumables that will control the oxygen potential of the weld pool must be developed.

  15. Dependence of fracture toughness of molybdenum laser welds on processing parameters and in-situ oxygen gettering

    SciTech Connect

    Pope, L.E.; Jellison, J.L.

    1980-01-01

    Fracture toughness properties have been determined for laser welds in different grades of molybdenum. The fracture toughness of welds in sintered molybdenum was consistently less than the fracture toughness of welds in vacuum arc remelted molybdenum. These differences cannot be attributed to oxygen content, since the oxygen level was nominally the same for all grades of molybdenum examined in this program. Alloy additions of titanium by means of physically deposited coatings significantly improved the fracture toughness of welds in sintered molybdenum, whereas titanium additions to welds in vacuum arc remelted molybdenum decreased the fracture toughness slightly. Pulsed laser welds exhibited fine columnar structures and, in the case of sintered molybdenum, superior fracture toughness when compared with continuous wave laser welds. 6 figures, 3 tables.

  16. Welding Curriculum.

    ERIC Educational Resources Information Center

    Alaska State Dept. of Education, Juneau. Div. of Adult and Vocational Education.

    This competency-based curriculum guide is a handbook for the development of welding trade programs. Based on a survey of Alaskan welding employers, it includes all competencies a student should acquire in such a welding program. The handbook stresses the importance of understanding the principles associated with the various elements of welding.…

  17. Welding IV.

    ERIC Educational Resources Information Center

    Allegheny County Community Coll., Pittsburgh, PA.

    Instructional objectives and performance requirements are outlined in this course guide for Welding IV, a competency-based course in advanced arc welding offered at the Community College of Allegheny County to provide students with proficiency in: (1) single vee groove welding using code specifications established by the American Welding Society…

  18. Polyethylene laser welding based on optical absorption variations

    NASA Astrophysics Data System (ADS)

    Galtieri, G.; Visco, A.; Nocita, D.; Torrisi, L.; Ceccio, G.; Scolaro, C.

    2016-04-01

    Polymeric materials, both pure and containing nanostructures, can be prepared as thin sheets in order to produce joints with an interface between an optically transparent sheet and an optically absorbent substrate to be welded by infrared pulsed laser irradiation. The Laser Transmission Welding (LTW) technique has been successfully applied in order to join two or more thermoplastic polymeric sheets that must have a similar chemical composition. In this research work, polymeric joints of Ultra High Molecular Weight Polyethylene sheets were realized, characterized and welded. Some polymer sheets were doped, at different concentrations, with carbon nano-particles absorbent the laser radiation. A pulsed laser operating in the wavelength region 532 nm with intensity of the order of 109 Watt/cm2 was employed to be transmitted by the transparent polymer and to be absorbed by the carbon enriched surface. At the interface of the two polymers the released energy induces melting, that is assisted by pressure, producing a fast and resistant welding zone. Mechanical and optical characterizations and surface analyses are presented and discussed.

  19. The development of a pulsed laser imaging system for natural gas leak detection

    NASA Astrophysics Data System (ADS)

    Kulp, Thomas J.

    The detection of gas leaks represents a critical operation performed regularly by the gas industry to maintain the integrity and safety of its vast network of piping, both above and below the ground. We are developing a technology that allows the real-time imaging of gas plumes in a television format. Termed backscatter absorption gas imaging (BAGI), the technique operates by illuminating a scene with infrared laser radiation having a wavelength that is absorbed by the gas to be detected (in this case, methane). Backscattered laser radiation is used to create a video image of the scene. If a leak of the target gas is present in the field-of-view of the camera, it attenuates a portion of the backscatter and creates a dark cloud in the video picture. The specific purpose of this project is to investigate a new method of accomplishing BAGI using a pulsed laser source. The pulsed laser imager under development in this project is expected to have a range (greater than or equal to 40 m) and sensitivity (less than 10 ppm-m) that will surpass the respective attributes of a scanned continuous wave laser imager. The pulsed system will operate by flooding (rather than scanning) the imaged scene with pulses of laser radiation. Imaging will be accomplished using a focal-plane array camera that operates in a snapshot format. The higher power of the pulsed laser source and the more effective collection optics of the focal-plane array-based receiver will allow the performance enhancements to be achieved.

  20. Femtosecond pulse laser ablation of metallic, semiconducting, ceramic, and biological materials

    NASA Astrophysics Data System (ADS)

    Kautek, Wolfgang; Krueger, Joerg

    1994-09-01

    Production of holes and grooves of < 30 micrometers diameter with high aspect ratio value is a delicate task either for mechanical tools, or for conventional nanosecond pulse lasers like e.g. pulsed Nd:YAG or excimer lasers. They later tend to cause microcracks extending from an annular melting zone, or substantial disruption, respectively. Experimental results are presented which demonstrate that the development of intense ultrashort pulse laser systems (>> 1012 W cm-2, (tau) < 1 ps) opens up possibilities for materials processing by cold plasma generation and ablation of metals, semiconductors, ceramics, composites, and biological materials. A femtosecond and a nanosecond dye laser with pulse durations of 300 fs (< 200 (mu) J) and 7 ns (< 10 mJ), and center wavelengths at 612 and 600 nm, respectively, both focused on an area of the order of 10-5 cm2, have been applied either to absorbing substrates, like polycrystalline gold, silicon (111), aluminum nitride ceramics, or transparent materials, like synthetic and human dental hydroxyapatite composites, bone material, and human cornea transplants. The fs-laser generates its own absorption in transparent materials by a multiphoton absorption process, and thus forces the absorption of visible radiation. Because the time is too short (< ps) for significant transport of mass and energy, the beam interaction generally results in the formation of a thin plasma layer of approximately solid state density. Only after the end of the subpicosecond laser pulse, it expands rapidly away from the surface without any light absorption and further plasma heating. Therefore, energy transfer (heat and impulse) to the target material, and thermal and mechanical disruption are minimized. In contrast to heat- affected zones (HAZ's) generated by conventional nanosecond pulse lasers of the order of 1 - 10 micrometers , HAZ's of less than 0.02 micrometers were observed.

  1. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Joly, Alan G.; Tonkyn, Russell G.; Kay, Bruce D.; Kimmel, Greg A.

    2016-04-01

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ˜1010 K/s for temperature increases of ˜100-200 K are obtained. Subsequent rapid cooling (˜5 × 109 K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ˜±2.7% leading to a temperature uncertainty of ˜±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

  2. Development of a high magnetic field assisted pulsed laser deposition system

    NASA Astrophysics Data System (ADS)

    Zhang, Kejun; Dai, Jianming; Wu, Wenbin; Zhang, Peng; Zuo, Xuzhong; Zhou, Shu; Zhu, Xuebin; Sheng, Zhigao; Liang, Changhao; Sun, Yuping

    2015-09-01

    A high magnetic field assisted pulsed laser deposition (HMF-PLD) system has been developed to in situ grow thin films in a high magnetic field up to 10 T. In this system, a specially designed PLD cylindrical vacuum chamber is horizontally located in the bore configuration of a superconducting magnet with a bore diameter of 200 mm. To adjust the focused pulsed laser into the target in such a narrow PLD vacuum chamber, an ingeniously built-in laser leading-in chamber is employed, including a laser mirror with a reflection angle of 65° and a damage threshold up to 3.4 J/cm2. A laser alignment system consisting of a built-in video-unit leading-in chamber and a low-energy alignment laser is applied to monitor and align the pulsed laser propagation in the PLD vacuum chamber. We have grown La0.7Sr0.3MnO3 (LSMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates by HMF-PLD. The results show that the nanostructures of the LSMO films can be tuned from an epitaxially continuous film structure without field to a vertically aligned nanorod structure with an applied high magnetic field above 5 T, and the dimension size of the nanorods can be tuned by the strength of the magnetic field. The associated magnetic anisotropy is found to be highly dependent on the nanorod structures. We show how the HMF-PLD provides an effective route toward tuning the nanostructures and the physical properties of functional thin films, giving it an important role in development of nanodevices and their application.

  3. Development of a high magnetic field assisted pulsed laser deposition system.

    PubMed

    Zhang, Kejun; Dai, Jianming; Wu, Wenbin; Zhang, Peng; Zuo, Xuzhong; Zhou, Shu; Zhu, Xuebin; Sheng, Zhigao; Liang, Changhao; Sun, Yuping

    2015-09-01

    A high magnetic field assisted pulsed laser deposition (HMF-PLD) system has been developed to in situ grow thin films in a high magnetic field up to 10 T. In this system, a specially designed PLD cylindrical vacuum chamber is horizontally located in the bore configuration of a superconducting magnet with a bore diameter of 200 mm. To adjust the focused pulsed laser into the target in such a narrow PLD vacuum chamber, an ingeniously built-in laser leading-in chamber is employed, including a laser mirror with a reflection angle of 65° and a damage threshold up to 3.4 J/cm(2). A laser alignment system consisting of a built-in video-unit leading-in chamber and a low-energy alignment laser is applied to monitor and align the pulsed laser propagation in the PLD vacuum chamber. We have grown La0.7Sr0.3MnO3 (LSMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates by HMF-PLD. The results show that the nanostructures of the LSMO films can be tuned from an epitaxially continuous film structure without field to a vertically aligned nanorod structure with an applied high magnetic field above 5 T, and the dimension size of the nanorods can be tuned by the strength of the magnetic field. The associated magnetic anisotropy is found to be highly dependent on the nanorod structures. We show how the HMF-PLD provides an effective route toward tuning the nanostructures and the physical properties of functional thin films, giving it an important role in development of nanodevices and their application. PMID:26429478

  4. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum.

    PubMed

    Xu, Yuntao; Dibble, Collin J; Petrik, Nikolay G; Smith, R Scott; Joly, Alan G; Tonkyn, Russell G; Kay, Bruce D; Kimmel, Greg A

    2016-04-28

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ∼10(10) K/s for temperature increases of ∼100-200 K are obtained. Subsequent rapid cooling (∼5 × 10(9) K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ∼±2.7% leading to a temperature uncertainty of ∼±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces. PMID:27131543

  5. Pool Purification

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Caribbean Clear, Inc. used NASA's silver ion technology as a basis for its automatic pool purifier. System offers alternative approach to conventional purification chemicals. Caribbean Clear's principal markets are swimming pool owners who want to eliminate chlorine and bromine. Purifiers in Caribbean Clear System are same silver ions used in Apollo System to kill bacteria, plus copper ions to kill algae. They produce spa or pool water that exceeds EPA Standards for drinking water.

  6. The mechanism of penetration increase in A-TIG welding

    NASA Astrophysics Data System (ADS)

    Zhang, Rui-Hua; Pan, Ji-Luan; Katayama, Seiji

    2011-06-01

    The mechanism of the increasing of A-TIG welding penetration is studied by using the activating flux we developed for stainless steel. The effect of flux on the flow and temperature fields of weld pool is simulated by the PHOENICS software. It shows that without flux, the fluid flow will be outward along the surface of the weld pool and then down, resulting in a flatter weld pool shape. With the flux, the oxygen, which changes the temperature dependence of surface tension grads from a negative value to a positive value, can cause significant changes on the weld penetration. Fluid flow will be inward along the surface of the weld pool toward the center and then down. This fluid flow pattern efficiently transfers heat to the weld root and produces a relatively deep and narrow weld. This change is the main cause of penetration increase. Moreover, arc construction can cause the weld width to become narrower and the penetration to become deeper, but this is not the main cause of penetration increase. The effects of flux on fluid flow of the weld pool surface and arc profiles were observed in conventional TIG welding and in A-TIG welding by using high-speed video camera. The fluid flow behavior was visualized in realtime scale by micro focused X-ray transmission video observation system. The result indicated that stronger inward fluid flow patterns leading to weld beads with narrower width and deeper penetration could be apparently identified in the case of A-TIG welding. The flux could change the direction of fluid flow in welding pool. It has a good agreement with the simulation results.

  7. Behavior of pulsed laser deposited hydroxyapatite thin films under simulated biological conditions

    NASA Astrophysics Data System (ADS)

    Grigorescu, S.; Sima, F.; Axente, E.; Feugeas, F.; Mihailescu, I. N.

    2007-03-01

    In the present paper, a study concerning the in-vitro behaviour of Hydroxyapatite films obtained by Pulsed Laser Deposition technique on titanium under different conditions was performed. The structures were immersed in Hank's Solution for 21 days in accurately controlled environment conditions. Both film and immersion solution changes were analyzed by means of XRD, SEM, EDX and X-Ray fluorescence respectively. The obtained results point to an excellent behaviour of the obtained films as bioactive structures, recommending this type of covering for further analysis in view of its use in orthopedic and dental implantology.

  8. Resonant Infrared Pulsed-Laser Deposition of Polymers Using a Free-Electron Laser

    NASA Astrophysics Data System (ADS)

    Johnson, Stephen; Bellmont, Ron; Bubb, Daniel; Haglund, Richard; Schriver, Ken

    2004-11-01

    Thin films of polyethylene glycol and polystyrene have been produced using resonant infrared pulsed-laser deposition (RIR-PLD). The laser used for the experiments was a tunable, high pulse-repetition rate free-electron laser operating in the mid-IR (2.9 - 3.5 im). Transfer of polymers with molecular weights up to 13,000 was accomplished at resonant vibrational frequencies without concomitant fragmentation or other photochemical degradation, in contrast to PLD techniques using ultraviolet lasers. Potential applications for this technique include drug delivery coatings and chemical and biological sensor construction.

  9. Analysis of thermodynamic effect in Si irradiated by pulsed-laser

    NASA Astrophysics Data System (ADS)

    Guo, Ming; Jin, Guangyong; Li, Mingxin; Ma, Yao; Yuan, Boshi; Yu, Huadong

    2014-12-01

    According to the heat conduction equation, thermoelastic equation and boundary conditions of finite, using the finite element method(FEM), established the three-dimensional finite element calculation model of thermal elastic ,numerical simulation the transient temperature field and stress field distribution of the single crystal silicon materials by the pulsing laser irradiation, and analytic solution the temperature distribution and stress distribution of laser irradiation on the silicon material , and analyzes the different parameters such as laser energy, pulse width, pulse number influence on temperature and stress, and the intrinsic damage mechanism of pulsed laser irradiation on silicon were studied. The results show that the silicon material is mainly in hot melt under the action of ablation damage.According to the irradiation of different energy and different pulse laser ,we can obtain the center temperature distribution, then get the law of the change of temperature with the variation of laser energy and pulse width in silicon material; according to the principal stress and shear stress distribution in 110 direction with different energy and different pulse, we can get the law of the change of stress distribution with the variation of laser energy and pulse width ;according to the principal stress distribution of single pulse and pulse train in 110 direction, we can get the law of the change of stress with pulse numbers in silicon.When power density of laser on optical material surface (or energy density) is the damage threshold, the optical material surface will form a spontaneous, periodic, and permanent surface ripple, it is called periodic surface structure laser induced (LIPSS).It is the condensed optical field of work to generate low dimensional quantum structures by laser irradiation on Si samples. The pioneering work of research and development and application of low dimensional quantum system has important academic value.The result of this paper

  10. Pulsed laser triggered high speed microfluidic fluorescence activated cell sorter†‡

    PubMed Central

    Wu, Ting-Hsiang; Chen, Yue; Park, Sung-Yong; Hong, Jason; Teslaa, Tara; Zhong, Jiang F.; Di Carlo, Dino; Teitell, Michael A.

    2014-01-01

    We report a high speed and high purity pulsed laser triggered fluorescence activated cell sorter (PLACS) with a sorting throughput up to 20 000 mammalian cells s−1 with 37% sorting purity, 90% cell viability in enrichment mode, and >90% purity in high purity mode at 1500 cells s−1 or 3000 beads s−1. Fast switching (30 μs) and a small perturbation volume (~90 pL) is achieved by a unique sorting mechanism in which explosive vapor bubbles are generated using focused laser pulses in a single layer microfluidic PDMS channel. PMID:22361780

  11. Short spatial filters with spherical lenses for high-power pulsed lasers

    SciTech Connect

    Burdonov, K F; Soloviev, A A; Shaikin, A A; Potemkin, A K; Egorov, A S

    2013-11-30

    We report possible employment of short spatial filters based on spherical lenses in a pulsed laser source (neodymium glass, 300 J, 1 ns). The influence of the spherical aberration on the quality of output radiation and coefficient of conversion to the second harmonics is studied. The ultra-short aberration spatial filter of length 1.9 m with an aperture of 122 mm is experimentally tested. A considerable shortening of multi-cascade pump lasers for modern petawatt laser systems is demonstrated by the employment of short spatial filters without expensive aspherical optics. (elements of laser systems)

  12. Infrared Imaging of {ital In Vivo} Microvasculature Following Pulsed Laser Irradiation

    SciTech Connect

    Telenkov, S.A.; Milner, T.E.; Smithies, D.J.; Nelson, J.S.; Goodman, D.M.; Tanenbaum, B.S.

    1998-10-01

    Infrared emission images of the chick chorioallantoic membrane (CAM) microvasculature following pulsed laser irradiation were recorded using a high speed infrared focal plane array camera. A three-dimensional tomographic reconstruction algorithm was applied to compute the initial space-dependent temperature increase in discrete CAM blood vessels caused by light absorption. The proposed method may provide consistent estimates of the physical dimensions of subsurface blood vessels and may be useful in understanding a variety of biomedical engineering problems involving laser{endash}tissue interaction. {copyright} {ital 1998 Society of Photo-Optical Instrumentation Engineers.}

  13. Theory of suppressing avalanche process of carrier in short pulse laser irradiated dielectrics

    SciTech Connect

    Deng, Hongxiang; Zu, Xiaotao; Zheng, WG; Yuan, XD; Xiang, Xia; Sun, Kai; Gao, Fei

    2014-05-28

    A theory for controlling avalanche process of carrier during short pulse laser irradiation is proposed. We show that avalanche process of conduction band electrons (CBEs) is determined by the occupation number of phonons in dielectrics. The theory provides a way to suppress avalanche process and a direct judgment for the contribution of avalanche process and photon ionization process to the generation of CBEs. The obtained temperature dependent rate equation shows that the laser induced damage threshold of dielectrics, e.g., fused silica, increase nonlinearly with the decreases of temperature. Present theory predicts a new approach to improve the laser induced damage threshold of dielectrics.

  14. A Pulsed Laser-Electromagnetic Hybrid Accelerator For Space Propulsion Application

    SciTech Connect

    Shinohara, Tadaki; Horisawa, Hideyuki; Baba, Msahumi; Tei, Kazuyoku

    2010-05-06

    A fundamental study of a newly developed rectangular pulsed laser-electromagnetic hybrid thruster was conducted, in which laser-ablation plasma was induced through laser beam irradiation onto a solid target and accelerated by electrical means instead of direct acceleration only by using a laser beam. The performance of the thruster was evaluated by measuring the mass per shot and impulse bit. As results, significantly high specific impulse ranging from 5,000 approx6,000 sec were obtained at energies of 0.1 and 8.6 J, respectively. In addition, the typical thrust efficiency varied from 17% to 19% depending on the charge energy.

  15. High-Isp Mode Of Pulsed Laser-Electromagnetic Hybrid Accelerator For Space Propulsion Applications

    SciTech Connect

    Horisawa, Hideyuki; Kishida, Yoshiaki; Funaki, Ikkoh

    2010-10-08

    A fundamental study of a newly developed rectangular pulsed laser-electromagnetic hybrid thruster was conducted. Laser-ablation plasma in the thruster was induced through laser beam irradiation onto a solid target and accelerated by electrical means instead of direct acceleration only by using a laser beam. The performance of the thrusters was evaluated by measuring the mass shot and impulse bit. As results, significantly high specific impulses up to 7,200 sec were obtained at the charge energies of 8.6 J. In addition, typical thrust efficiency varied between 11.8% and 21.3% depending on the charge energy.

  16. Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition

    SciTech Connect

    Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Joerg K. N.; Stritzker, Bernd

    2006-04-15

    Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd{sub 3}Ga{sub 5}O{sub 12} substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 {mu}m showing good crystalline quality and epitaxial growth.

  17. Direct melt processing of pentacene at temperatures above 1000 °C by pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Goose, Joseph E.; Wong, Keith; Clancy, Paulette; Thompson, Michael O.

    2008-11-01

    Pentacene remains as a leading candidate for organic thin film transistors in applications such as sensor and flexible displays. Its processing, however, has been limited to relatively low temperatures and only in the solid phase. Liquid pentacene has never been experimentally observed, although the melting temperature is predicted to lie between 200 and 400 °C. We report a method of heating pentacene thin films to temperatures above 1000 °C using pulsed laser irradiation. This rapid heating induces morphological changes consistent with formation of a transient liquid phase. X-ray diffraction and Raman spectroscopy show that the pentacene remains intact after processing at these extreme temperatures.

  18. Pulsed laser deposition and investigation of antimony-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Puzikov, A. S.; Lyanguzov, N. V.; Kaidashev, E. M.

    2014-10-01

    We have investigated the influence of oxygen partial pressure, temperature of synthesis and annealing conditions on nanocsrystallineSb-doped thin films, grown by pulsed laser deposition. It is shown that the minimum resistivity (~8·10-3Ω·cm) and the maximum carriers density (~ 2·1019 cm-3) corresponds to the pressure range 5·10-3-7·10-3 mbar, to the temperature 550 ° C and in situ annealing at 700 °C.Also we show the features of the crystal lattice's dynamics, which are found in the Raman research.

  19. Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Athanasopoulos, G. I.; Giapintzakis, J.

    2013-08-01

    One-step growth of n-doped Si nanostructures by picosecond ultra fast pulsed laser deposition at 1064 nm is reported for the first time. The structure and morphology of the Si nanostructures were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Transmission electron microscopy studies revealed that the shape of the Si nanostructures depends on the ambient argon pressure. Fibrous networks, cauliflower formations and Si rectangular crystals grew when argon pressure of 300 Pa, 30 Pa and vacuum (10-3 Pa) conditions were used, respectively. In addition, the electrical resistance of the vacuum made material was investigated.

  20. Pulsed Laser Processing of Functionalized Polysaccharides for Controlled Release Drug Delivery Systems

    NASA Astrophysics Data System (ADS)

    Cristescu, R.; Popescu, C.; Popescu, A. C.; Socol, G.; Mihailescu, I.; Caraene, G.; Albulescu, R.; Buruiana, T.; Chrisey, D.

    We report on the deposition of triacetate-pullulan polysaccharide thin films on drug pellets (diclofenac sodium) by matrix assisted pulsed laser evaporation method. The radiation generated by a pulsed excimer KrF* laser source (λ = 248 nm, τ = 20 ns) operated at 2 Hz repetition rate was used for ice targets evaporation. The timed - controlled drug delivery was proved by spectroscopic in vitro studies and in vivo anti-inflammatory investigations on rabbits. We showed that the coating of drug pellets with triacetate-pullulan thin films resulted in the delayed delivery of the drug for up to 30 min.

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

    PubMed

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

    2011-02-22

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

  2. Effect of medium range order on pulsed laser crystallization of amorphous germanium thin films

    DOE PAGESBeta

    Li, T. T.; Bayu Aji, L. B.; Heo, T. W.; Santala, M. K.; Kucheyev, S. O.; Campbell, G. H.

    2016-06-03

    Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar+ ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the dynamic transmission electron microscope operated in the multi-frame movie mode. In conclusion, the propagation rate of the crystallization front for the irradiated material was lower; the changes were correlated to the MRO difference and formation of a thin liquid layer during crystallization.

  3. Third order nonlinearity in pulsed laser deposited LiNbO3 thin films

    NASA Astrophysics Data System (ADS)

    Tumuluri, Anil; Rapolu, Mounika; Rao, S. Venugopal; Raju, K. C. James

    2016-05-01

    Lithium niobate (LiNbO3) thin films were prepared using pulsed laser deposition technique. Structural properties of the same were examined from XRD and optical band gap of the thin films were measured from transmittance spectra recorded using UV-Visible spectrophotometer. Nonlinear optical properties of the thin films were recorded using Z-Scan technique. The films were exhibiting third order nonlinearity and their corresponding two photon absorption, nonlinear refractive index, real and imaginary part of nonlinear susceptibility were calculated from open aperture and closed aperture transmission curves. From these studies, it suggests that these films have potential applications in nonlinear optical devices.

  4. Fabrication of multiferroic GdMnO3 thin film by pulsed laser deposition technique

    NASA Astrophysics Data System (ADS)

    Negi, Puneet; Agrawal, H. M.; Srivastava, R. C.; Asokan, K.

    2012-06-01

    Here, we report the fabrication of GdMnO3 multiferroic thin film on SrTiO3 (110) substrate by pulsed laser deposition (PLD) technique. The target sample was synthesized using modified solgel route. The thickness of the film observed by Talystep profilometer, is about 200 nm. X-ray diffraction and Raman spectroscopic techniques were used to investigate the structure of the target as well as of the film. The surface topography of the film was investigated by atomic force microscopy.

  5. George E. Pake Prize Lecture: Pulsed Laser Deposition and the Oxide Electronics Revolution

    NASA Astrophysics Data System (ADS)

    Venkatesan, T.

    2012-02-01

    The discovery of the Pulsed Laser Deposition (PLD) Process at Bellcore was followed by a stream of advances in the epitaxial growth of oxides and a variety of heterostructures and interfaces. Today Oxide Electronics is a fascinating field with a great deal of new Science and potential for applications. Following a discussion of these events, my talk will focus on the adventure involved in creating a new company, Neocera, and, at the same time, pushing ahead in the evolving field of oxide electronics. There, electron spin, pairing, and alignment to create superconductivity and magnetism have opened up new frontiers for research and materials development.

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

    SciTech Connect

    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.; Chang, T.D.; Neev, J.

    1996-05-01

    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.

  7. DIAL monitoring of atmospheric climate-determining gases employing high-power pulsed laser diodes

    NASA Astrophysics Data System (ADS)

    Penchev, Stoyan P.; Naboko, Sergei V.; Naboko, Vassily N.; Pencheva, Vasilka H.; Donchev, T.; Pavlov, Lyubomir Y.; Simeonov, P.

    2003-11-01

    High-power pulsed laser diodes are employed for determining atmospheric humidity and methane. The proposed DIAL method optimizes the spectral properties of laser radiation within the molecular absorption bands of 0.86 - 0.9 μm of these major greenhouse gases. The explicit absorption spectrum is explored by computational convolution method based on reference data on spectral linestrengths modulated by the characteristic broad laser line of the selected laser diodes. The lidar scheme is ultimately compact, of low-energy consumption and suggests a large potential for ecological monitoring.

  8. X-ray absorption study of pulsed laser deposited boron nitride films

    SciTech Connect

    Chaiken, A.; Terminello, L.J.; Wong, J.; Doll, G.L.; Sato, T.

    1994-02-02

    B and N K-edge x-ray absorption spectroscopy measurements have been performed on three BN thin films grown on Si substrates using ion- assisted pulsed laser deposition. Comparison of the films` spectra to those of several single-phase BN powder standards shows that the films consist primarily of sp{sup 2} bonds. Other features in the films`s spectra suggest the presence of secondary phases, possibly cubic or rhombohedral BN. Films grown at higher deposition rates and higher ion-beam voltages are found to be more disordered, in agreement with previous work.

  9. Preparation and characterization of YBCO coating on metallic RABiT substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Gonal, M. R.; Prajapat, C. L.; Igalwar, P. S.; Maji, B. C.; Singh, M. R.; Krishnan, M.

    2016-05-01

    Superconducting YBCO films are coated on metallic Rolling Assisted Bi-axially Textured Substrates (RABiTS) Ni-5wt % W (NiW) (002) substrate using pulsed laser deposition (PLD) system. Targets of YBa2Cu3O7-δ (YBCO) and buffer layers of Ceria and 8 mole % Yttria Stabilized Zirconia (YSZ) of high density are synthesized. At each stage of deposition coatings are characterized by XRD. Transport studies show superconducting nature of YBCO only when two successive buffer layers of YSZ and CeO2 are used.

  10. Combinatorial pulsed laser deposition of doped yttrium iron garnet films on yttrium aluminium garnet

    SciTech Connect

    Sposito, A. Eason, R. W.; Gregory, S. A.; Groot, P. A. J. de

    2014-02-07

    We investigate the crystalline growth of yttrium iron garnet (YIG) films doped with bismuth (Bi) and cerium (Ce) by combinatorial pulsed laser deposition, co-ablating a YIG target and either a Bi{sub 2}O{sub 3} or a CeO{sub 2} target, for applications in microwave and optical communications. Substrate temperature is critical for crystalline growth of YIG with simultaneous inclusion of Bi in the garnet lattice, whereas Ce is not incorporated in the garnet structure, but forms a separate CeO{sub 2} phase.

  11. Contribution to study of heat transfer and fluid flow during GTA welding

    NASA Astrophysics Data System (ADS)

    Koudadje, Koffi; Delalondre, Clarisse; Médale, Marc; Carpreau, Jean-Michel

    2014-06-01

    In this paper, the effect of surface-active elements especially sulfur on weld pool shape has been reported. In our contribution, we analyze the influence of the weld pool chemical composition (Mn, Si, …), welding energy, sulphur gradient and electromagnetic effect. The computed results are in good agreement with the corresponding experimental results, indicating the validity of the modeling approach.

  12. Study on laser welding of fuel clad tubes and end plugs made of modified 9Cr-1Mo steel for metallic fuel of Fast Breeder Reactors

    NASA Astrophysics Data System (ADS)

    Harinath, Y. V.; Gopal, K. A.; Murugan, S.; Albert, S. K.

    2013-04-01

    A procedure for Pulsed Laser Beam Welding (PLBW) has been developed for fabrication of fuel pins made of modified 9Cr-1Mo steel for metallic fuel proposed to be used in future in India's Fast Breeder Reactor (FBR) programme. Initial welding trials of the samples were carried out with different average power using Nd-YAG based PLBW process. After analyzing the welds, average power for the weld was optimized for the required depth of penetration and weld quality. Subsequently, keeping the average power constant, the effect of various other welding parameters like laser peak power, pulse frequency, pulse duration and energy per pulse on weld joint integrity were studied and a procedure that would ensure welds of acceptable quality with required depth of penetration, minimum size of fusion zone and Heat Affected Zone (HAZ) were finalized. This procedure is also found to reduce the volume fraction delta-ferrite in the fusion zone.

  13. Variable-Polarity Plasma Arc Welding Of Alloy 2219

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.; Nunes, Arthur C., Jr.

    1989-01-01

    Report presents results of study of variable-polarity plasma arc (VPPA) welding of aluminum alloy 2219. Consists of two parts: Examination of effects of microsegregation and transient weld stress on macrosegregation in weld pool and, electrical characterization of straight- and reverse-polarity portions of arc cycle.

  14. Optical Monitoring of Weld Penetration

    NASA Technical Reports Server (NTRS)

    Maram, J.

    1986-01-01

    Robotic welding controlled by reliable, relatively-noise-free optoelectronic unit. Bounding off meniscus of pool of molten metal, laser beam impinges on position-sensitive photodetector. Beam diameter adjusted for width of weld. Optical filters screen out light from arc. Made from small, low-cost components and utilizing optical fibers to conduct signals, system immune to electromagnetic interference common in industrial environments. Aimed for automatic welders, robot welders in particular and also adaptable to other types of welding, including tungsten/inert-gas, laser, and electron-beam techniques.

  15. Fabrication of microgrooves on a curved surface by the confocal measurement system using pulse laser and continuous laser

    NASA Astrophysics Data System (ADS)

    Noh, Jiwhan; Cho, Ilhwan; Lee, Seungwoo; Na, Suckjoo; Lee, Jae-Hoon

    2012-03-01

    In order to fabricate microgrooves on a curved surface, the curved surface was measured with a confocal system and then it was used for laser microprocessing. This paper proposes a new method of using a pulse laser for the confocal system to measure the curved surface. It also compares the conventional way of using a continuous laser and a new way of using the pulse laser with the confocal system. Using the data measured with the pulse laser for fabrication, microgrooves were fabricated on a curved surface. The width of the fabricated microgroove was 10 μm and the depth was 27 μm. The microgroove fabricated on a curved surface as a part of this study can be used in injection molding to manufacture a micropatterned plastic surface at a low cost. This plastic surface can be applied for a superhydrophobic surface, a self-cleaning surface, or a biochip.

  16. In situ observation of self-organizing nanodot formation under nanosecond-pulsed laser irradiation on Si surface

    NASA Astrophysics Data System (ADS)

    Watanabe, S.; Yoshida, Y.; Kayashima, S.; Yatsu, S.; Kawai, M.; Kato, T.

    2010-11-01

    An in situ observation of the formation of a laser-irradiation-induced nanodot array on a Si surface was performed using a pulsed-laser-equipped high-voltage electron microscope (laser-HVEM). Under multiple nanosecond (ns) pulsed laser irradiation shots, atomic clusters were first formed and distributed on the surface in order to grow them epitaxially into protruded dots with diameters of ten nanometers or less. This is followed by their diffusion induced by successive laser shots to cannibalize and merge them into a ripple line with aligned, larger dots. We conclude that the present subwavelength two-dimensionally-ordered nanodot array is formed by self-organization under pulsed laser irradiation.

  17. Towards new binary compounds: Synthesis of amorphous phosphorus carbide by pulsed laser deposition

    SciTech Connect

    Hart, Judy N.; May, Paul W.; Allan, Neil L.; Hallam, Keith R.; Claeyssens, Frederik; Fuge, Gareth M.; Ruda, Michelle; Heard, Peter J.

    2013-02-15

    We have recently undertaken comprehensive computational studies predicting possible crystal structures of the as yet unknown phosphorus carbide as a function of composition. In this work, we report the synthesis of amorphous phosphorus-carbon films by pulsed laser deposition. The local bonding environments of carbon and phosphorus in the synthesised materials have been analysed by x-ray photoelectron spectroscopy; we have found strong evidence for the formation of direct P-C bonding and hence phosphorus carbide. There is a good agreement between the bonding environments found in this phosphorus carbide material and those predicted in the computational work. In particular, the local bonding environments are consistent with those found in the {beta}-InS-like structures that we predict to be low in energy for phosphorus:carbon ratios between 0.25 and 1. Highlights: Black-Right-Pointing-Pointer We have synthesised amorphous phosphorus-carbon films by pulsed laser deposition. Black-Right-Pointing-Pointer X-ray photoelectron spectroscopy results indicate formation of direct P-C bonds and hence phosphorus carbide. Black-Right-Pointing-Pointer Local bonding environments are consistent with those in predicted structures.

  18. Multi-beam pulsed laser deposition: new method of making nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Darwish, Abdalla M.; Wilson, Simeon; Blackwell, Ashely; Taylor, Keylantra; Sarkisov, Sergey; Patel, Darayas; Mele, Paolo; Koplitz, Brent

    2015-08-01

    Huge number of new photonic devices, including light emitters, chemical sensors, and energy harvesters, etc. can be made of the nanocomposite coatings produced by the new multi-beam pulsed laser deposition (MB-PLD) process. We provide a short review of the conventional single-beam PLD method and explain why it is poorly suitable for making nanocomposite coatings. Then we describe the new MB-PLD process and system, particularly the multiple-beam matrix assisted pulsed laser evaporation (MB-MAPLE) version with laser beam scanning and plume direction control. The latter one is particularly designed to make organic (polymer) - inorganic functionalized nanocomposite coatings. Polymer film serves as a host for inorganic nanoparticles that add a specific functionality to the film. We analyze the properties of such coatings using the examples of poly(methyl methacrylate) (PMMA) films impregnated with the nanoparticles of rare-earth (RE) upconversion phosphors. They demonstrated the preservation of microcrystalline structure and bright upconversion emission in visible region of the phosphor nanoparticles after they were transferred in the polymer matrix during the MB-MAPLE process. The proposed technology has thus proven to serve its purpose: to make functionalized polymer nanocomposite coatings for a various potential applications.

  19. Analytical study of pulsed laser irradiation on some materials used for photovoltaic cells on satellites

    NASA Astrophysics Data System (ADS)

    Abd El-Hameed, Afaf M.

    2015-12-01

    The present research concerns on the study of laser-powered solar panels used for space applications. A mathematical model representing the laser effects on semiconductors has been developed. The temperature behavior and heat flow on the surface and through a slab has been studied after exposed to nano-second pulsed laser. The model is applied on two different types of common active semiconductor materials that used for photovoltaic cells fabrication as silicon (Si), and gallium arsenide (GaAs). These materials are used for receivers' manufacture for laser beamed power in space. Various values of time are estimated to clarify the heat flow through the material sample and generated under the effects of pulsed laser irradiation. These effects are theoretically studied in order to determine the performance limits of the solar cells when they are powered by laser radiation during the satellite eclipse. Moreover, the obtained results are carried out to optimize conversion efficiency of photovoltaic cells and may be helpful to give more explanation for layout of the light-electricity space systems.

  20. Dynamics of ultrashort pulsed laser radiation induced non-thermal ablation of graphite

    NASA Astrophysics Data System (ADS)

    Reininghaus, M.; Kalupka, C.; Faley, O.; Holtum, T.; Finger, J.; Stampfer, C.

    2014-12-01

    We report on the dependence of a laser radiation induced ablation process of graphite on the applied pulse duration of ultrashort pulsed laser radiation smaller than 4 ps. The emerging so-called non-thermal ablation process of graphite has been confirmed to be capable to physically separate ultrathin graphitic layers from the surface of pristine graphite bulk crystal. This allows the deposition of ablated graphitic flakes on a substrate in the vicinity of the target. The observed ablation threshold determined at different pulse durations shows a modulation, which we ascribe to lattice motions along the c axis that are theoretically predicted to induce the non-thermal ablation process. In a simple approach, the ablation threshold can be described as a function of the energy penetration depth and the absorption of the applied ultrashort pulsed laser radiation. Based on the analysis of the pulse duration dependence of those two determining factors and the assumption of an invariant ablation process, we are able to reproduce the pulse duration dependence of the ablation threshold. Furthermore, the observed pulse duration dependences confirm the assumption of a fast material specific response of graphite target subsequent to optical excitation within the first 2 ps.

  1. Shock-wave measurements of solids using the long-pulsed laser

    NASA Astrophysics Data System (ADS)

    Uchino, Mazakazu; Kaetsu, Masahide; Mashimo, Tsutomu

    1997-05-01

    The optical measurement system using long-pulsed lasers were constructed for shock-wave measurements and spectroscopy under shock compression of solids. We have produced two types of long-pulsed lasers with no Q-switch for such purposes: Nd:YAG frequency-double laser using an intracavity KTP crystal, and dye laser using a rhodamine 6G. They consisted of doubled-elliptical pump cavity, two zenon flash lamps, and a high-voltage electrical-pulse source. The former one can be used as a light source for a Fabry-Perot type Interferometer (FPI), and the latter one can be used as a constant light source for a luminescence or an absorption spectroscopy and for the inclined-mirror method. The inclined-mirror Hugoniot measurements of some materials were performed by using the long-pulsed dye laser and the mirror- rotating type streak camera. The time resolution was increased by using a narrow width slit and the laser. The velocity-interferometer system for shock-wave measurements using a FPI and the time-resolved optical spectroscopy system using a spectrometer were constructed combined with the Nd:YAG frequency-doubled laser and the dye laser, respectively, and with an image-converter streak camera.

  2. Laser transfer of biomaterials: Matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE Direct Write

    NASA Astrophysics Data System (ADS)

    Wu, P. K.; Ringeisen, B. R.; Krizman, D. B.; Frondoza, C. G.; Brooks, M.; Bubb, D. M.; Auyeung, R. C. Y.; Piqué, A.; Spargo, B.; McGill, R. A.; Chrisey, D. B.

    2003-04-01

    Two techniques for transferring biomaterial using a pulsed laser beam were developed: matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE direct write (MDW). MAPLE is a large-area vacuum based technique suitable for coatings, i.e., antibiofouling, and MDW is a localized deposition technique capable of fast prototyping of devices, i.e., protein or tissue arrays. Both techniques have demonstrated the capability of transferring large (mol wt>100 kDa) molecules in different forms, e.g., liquid and gel, and preserving their functions. They can deposit patterned films with spatial accuracy and resolution of tens of μm and layering on a variety of substrate materials and geometries. MDW can dispense volumes less than 100 pl, transfer solid tissues, fabricate a complete device, and is computed aided design/computer aided manufacturing compatible. They are noncontact techniques and can be integrated with other sterile processes. These attributes are substantiated by films and arrays of biomaterials, e.g., polymers, enzymes, proteins, eucaryotic cells, and tissue, and a dopamine sensor. These examples, the instrumentation, basic mechanisms, a comparison with other techniques, and future developments are discussed.

  3. Planarization of Isolated Defects on ICF Target Capsule Surfaces by Pulsed Laser Ablation

    DOE PAGESBeta

    Alfonso, Noel; Carlson, Lane C.; Bunn, Thomas L.

    2016-08-09

    Demanding surface quality requirements for inertial confinement fusion (ICF) capsules motivated the development of a pulsed laser ablation method to reduce or eliminate undesirable surface defects. The pulsed laser ablation technique takes advantage of a full surface (4π) capsule manipulation system working in combination with an optical profiling (confocal) microscope. Based on the defect topography, the material removal rate, the laser pulse energy and its beam profile, a customized laser raster pattern is derived to remove the defect. The pattern is a table of coordinates and number of pulses that dictate how the defect will be vaporized until its heightmore » is level with the capsule surface. This paper explains how the raster patterns are optimized to minimize surface roughness and how surface roughness after laser ablation is simulated. The simulated surfaces are compared with actual ablated surfaces. Large defects are reduced to a size regime where a tumble finishing process produces very high quality surfaces devoid of high mode defects. The combined polishing processes of laser ablation and tumble finishing have become routine fabrication steps for National Ignition Facility capsule production.« less

  4. In Situ Mitigation of Subsurface and Peripheral Focused Ion Beam Damage via Simultaneous Pulsed Laser Heating.

    PubMed

    Stanford, Michael G; Lewis, Brett B; Iberi, Vighter; Fowlkes, Jason D; Tan, Shida; Livengood, Rick; Rack, Philip D

    2016-04-01

    Focused helium and neon ion (He(+)/Ne(+)) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+)/Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposure process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. These results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams. PMID:26864147

  5. Physics of laser fusion. Volume III. High-power pulsed lasers

    SciTech Connect

    Holzrichter, J.F.; Eimerl, D.; George, E.V.; Trenholme, J.B.; Simmons, W.W.; Hunt, J.T.

    1982-09-01

    High-power pulsed lasers can deliver sufficient energy on inertial-confinement fusion (ICF) time scales (0.1 to 10 ns) to heat and compress deuterium-tritium fuel to fusion-reaction conditions. Several laser systems have been examined, including Nd:glass, CO/sub 2/, KrF, and I/sub 2/, for their ICF applicability. A great deal of developmental effort has been applied to the Nd:glass laser and the CO/sub 2/ gas laser systems; these systems now deliver > 10/sup 4/ J and 20 x 10/sup 12/ W to ICF targets. We are constructing the Nova Nd:glass laser at LLNL to provide > 100 kJ and > 100 x 10/sup 12/ W of 1-..mu..m radiation for fusion experimentation in the mid-1980s. For ICF target gain > 100 times the laser input, we expect that the laser driver must deliver approx. 3 to 5 MJ of energy on a time scale of 10 to 20 ns. In this paper we review the technological status of fusion-laser systems and outline approaches to constructing high-power pulsed laser drivers.

  6. Growth mechanism of pulsed laser fabricated few-layer MoS₂ on metal substrates.

    PubMed

    Loh, Tamie A J; Chua, Daniel H C

    2014-09-24

    Pulsed laser deposition (PLD) on metal substrates has recently been discovered to present an alternative method for producing highly crystalline few-layer MoS2. However, not every metal behaves in the same manner during film growth, and hence, it is crucial that the ability of various metals to produce crystalline MoS2 be thoroughly investigated. In this work, MoS2 was deposited on metal substrates, Al, Ag, Ni, and Cu, using a pulsed laser. Highly crystalline few-layer MoS2 was successfully grown on Ag, but is absent in Al, Ni, and Cu under specific growth conditions. This discrepancy was attributed to either excessively strong or insufficient adlayer-substrate interactions. In the case of Al, the effects of the strong interface interactions can be offset by increasing the amount of source atoms supplied, thereby producing semicrystalline few-layer MoS2. The results show that despite PLD being a physical vapor deposition technique, both physical and chemical processes play an important role in MoS2 growth on metal substrates. PMID:25203278

  7. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    PubMed

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor. PMID:26165282

  8. Variable fidelity robust optimization of pulsed laser orbital debris removal under epistemic uncertainty

    NASA Astrophysics Data System (ADS)

    Hou, Liqiang; Cai, Yuanli; Liu, Jin; Hou, Chongyuan

    2016-04-01

    A variable fidelity robust optimization method for pulsed laser orbital debris removal (LODR) under uncertainty is proposed. Dempster-shafer theory of evidence (DST), which merges interval-based and probabilistic uncertainty modeling, is used in the robust optimization. The robust optimization method optimizes the performance while at the same time maximizing its belief value. A population based multi-objective optimization (MOO) algorithm based on a steepest descent like strategy with proper orthogonal decomposition (POD) is used to search robust Pareto solutions. Analytical and numerical lifetime predictors are used to evaluate the debris lifetime after the laser pulses. Trust region based fidelity management is designed to reduce the computational cost caused by the expensive model. When the solutions fall into the trust region, the analytical model is used to reduce the computational cost. The proposed robust optimization method is first tested on a set of standard problems and then applied to the removal of Iridium 33 with pulsed lasers. It will be shown that the proposed approach can identify the most robust solutions with minimum lifetime under uncertainty.

  9. Pulsed laser imaging of rapid Ca2+ gradients in excitable cells.

    PubMed Central

    Monck, J R; Robinson, I M; Escobar, A L; Vergara, J L; Fernandez, J M

    1994-01-01

    Excitable cells are thought to respond to action potentials by forming short lived and highly localized Ca2+ gradients near sites of Ca2+ entry or near the site of Ca2+ release by intracellular stores. However, conventional imaging techniques lack the spatial and temporal resolution to capture these gradients. Here we demonstrate the use of pulsed-laser microscopy to measure Ca2+ gradients with submicron spatial resolution and millisecond time resolution in two preparations where the Ca2+ signal is thought to be fast and highly localized: adrenal chromaffin cells, where the entry of Ca2+ through voltage dependent Ca2+ channels triggers exocytotic fusion; and skeletal muscle fibers, where intracellular Ca2+ release from the sarcoplasmic reticulum initiates contraction. In chromaffin cells, Ca2+ gradients developed over 10-100 ms and were initially restricted to discrete submembrane domains, or hot spots, before developing into complete rings of elevated Ca2+ concentration. In frog skeletal muscle large, short-lived (approximately 6 ms) Ca2+ gradients were observed within individual sarcomeres following induction of action potentials. The pulsed laser imaging approach permits, for the first time, the capture and critical examination of rapid Ca2+ signaling events such as those underlying excitation-secretion and excitation-contraction coupling. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:7948669

  10. Strip Velocity Measurements for Gated X-Ray Imagers Using Short Pulse Lasers

    SciTech Connect

    Ross, P. W.; Cardenas, M.; Griffin, M.; Mead, A.; Silbernagel, C. T.; Bell, P.; Haque, S. H.

    2013-09-01

    Strip velocity measurements of gated X-ray imagers are presented using an ultra-short pulse laser. Obtaining time-resolved X-ray images of inertial confinement fusion shots presents a difficult challenge. One diagnostic developed to address this challenge is the gated X-ray imagers. The gated X-ray detectors (GXDs) developed by Lawrence Livermore National Laboratory and Los Alamos National Laboratory use a microchannel plate (MCP) coated with a gold strip line, which serves as a photocathode. GXDs are used with an array of pinholes, which image onto various parts of the GXD image plane. As the pulse sweeps over the strip lines, it creates a time history of the event with consecutive images. In order to accurately interpret the timing of the images obtained using the GXDs, it is necessary to measure the propagation of the pulse over the strip line. The strip velocity was measured using a short pulse laser with a pulse duration of approximately 1-2 ps. The 200nm light from the laser is used to illuminate the GXD MCP. The laser pulse is split and a retroreflective mirror is used to delay one of the legs. By adjusting the distance to the mirror, one leg is temporally delayed compared to the reference leg. The retroreflective setup is calibrated using a streak camera with a 1 ns full sweep. Resolution of 0.5 mm is accomplished to achieve a temporal resolution of ~5 ps on the GXD strip line.

  11. AFM and pulsed laser ablation methods for Cultural Heritage: application to archeometric analysis of stone artifacts

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Veltri, S.; Stranges, F.; Bonanno, A.; Xu, F.; Antici, P.

    2015-09-01

    In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface's roughness is evaluated from very small artifact's fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

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

    SciTech Connect

    Geohegan, D.B.

    1994-09-01

    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.

  13. Pulsed laser activated cell sorter (PLACS) for high-throughput fluorescent mammalian cell sorting

    NASA Astrophysics Data System (ADS)

    Chen, Yue; Wu, Ting-Hsiang; Chung, Aram; Kung, Yu-Chung; Teitell, Michael A.; Di Carlo, Dino; Chiou, Pei-Yu

    2014-09-01

    We present a Pulsed Laser Activated Cell Sorter (PLACS) realized by exciting laser induced cavitation bubbles in a PDMS microfluidic channel to create high speed liquid jets to deflect detected fluorescent samples for high speed sorting. Pulse laser triggered cavitation bubbles can expand in few microseconds and provide a pressure higher than tens of MPa for fluid perturbation near the focused spot. This ultrafast switching mechanism has a complete on-off cycle less than 20 μsec. Two approaches have been utilized to achieve 3D sample focusing in PLACS. One is relying on multilayer PDMS channels to provide 3D hydrodynamic sheath flows. It offers accurate timing control of fast (2 m sec-1) passing particles so that synchronization with laser bubble excitation is possible, an critically important factor for high purity and high throughput sorting. PLACS with 3D hydrodynamic focusing is capable of sorting at 11,000 cells/sec with >95% purity, and 45,000 cells/sec with 45% purity using a single channel in a single step. We have also demonstrated 3D focusing using inertial flows in PLACS. This sheathless focusing approach requires 10 times lower initial cell concentration than that in sheath-based focusing and avoids severe sample dilution from high volume sheath flows. Inertia PLACS is capable of sorting at 10,000 particles sec-1 with >90% sort purity.

  14. Method of high precision interval measurement in pulse laser ranging system

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Lv, Xin-yuan; Mao, Jin-jin; Liu, Wei; Yang, Dong

    2013-09-01

    Laser ranging is suitable for laser system, for it has the advantage of high measuring precision, fast measuring speed,no cooperative targets and strong resistance to electromagnetic interference,the measuremen of laser ranging is the key paremeters affecting the performance of the whole system.The precision of the pulsed laser ranging system was decided by the precision of the time interval measurement, the principle structure of laser ranging system was introduced, and a method of high precision time interval measurement in pulse laser ranging system was established in this paper.Based on the analysis of the factors which affected the precision of range measure,the pulse rising edges discriminator was adopted to produce timing mark for the start-stop time discrimination,and the TDC-GP2 high precision interval measurement system based on TMS320F2812 DSP was designed to improve the measurement precision.Experimental results indicate that the time interval measurement method in this paper can obtain higher range accuracy. Compared with the traditional time interval measurement system,the method simplifies the system design and reduce the influence of bad weather conditions,furthermore,it satisfies the requirements of low costs and miniaturization.

  15. Photoacoustic measurement for glucose solution concentration based on tunable pulsed laser induced ultrasound

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Huang, Zhen; Zhao, Dengji

    2012-12-01

    Noninvasive measurement of blood glucose concentration (BGC) has become a research hotspot. BGC measurement based on photoacoustic spectroscopy (PAS) was employed to detect the photoacoustic (PA) signal of blood glucose due to the advantages of avoiding the disturbance of optical scattering. In this paper, a set of custom-built BGC measurement system based on tunable optical parametric oscillator (OPO) pulsed laser and ultrasonic transducer was established to test the PA response effect of the glucose solution. In the experiments, we successfully acquired the time resolved PA signals of distilled water and glucose aqueous solution, and the PA peak-to-peak values(PPV) were gotten under the condition of excitated pulsed laser with changed wavelength from 1340nm to 2200nm by increasing interval of 10nm, the optimal characteristic wavelengths of distilled water and glucose solution were determined. Finally, to get the concentration prediction error, we used the linear fitting of ordinary least square (OLS) algorithm to fit the PPV of 1510nm, and we got the predicted concentration error was about 0.69mmol/L via the fitted linear equation. So, this system and scheme have some values in the research of noninvasive BGC measurement.

  16. An experimental investigation of pulsed laser-assisted machining of AISI 52100 steel

    NASA Astrophysics Data System (ADS)

    Panjehpour, Afshin; Soleymani Yazdi, Mohammad R.; Shoja-Razavi, Reza

    2014-11-01

    Grinding and hard turning are widely used for machining of hardened bearing steel parts. Laser-assisted machining (LAM) has emerged as an efficient alternative to grinding and hard turning for hardened steel parts. In most cases, continuous-wave lasers were used as a heat source to cause localized heating prior to material removal by a cutting tool. In this study, an experimental investigation of pulsed laser-assisted machining of AISI 52100 bearing steel was conducted. The effects of process parameters (i.e., laser mean power, pulse frequency, pulse energy, cutting speed and feed rate) on state variables (i.e., material removal temperature, specific cutting energy, surface roughness, microstructure, tool wear and chip formation) were investigated. At laser mean power of 425 W with frequency of 120 Hz and cutting speed of 70 m/min, the benefit of LAM was shown by 25% decrease in specific cutting energy and 18% improvement in surface roughness, as compared to those of the conventional machining. It was shown that at constant laser power, the increase of laser pulse energy causes the rapid increase in tool wear rate. Pulsed laser allowed efficient control of surface temperature and heat penetration in material removal region. Examination of the machined subsurface microstructure and microhardness profiles showed no change under LAM and conventional machining. Continuous chips with more uniform plastic deformation were produced in LAM.

  17. Mechanical and physicochemical properties of AlN thin films obtained by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Cibert, C.; Tétard, F.; Djemia, P.; Champeaux, C.; Catherinot, A.; Tétard, D.

    2004-10-01

    AlN thin films have been deposited on Si(100) substrates by a pulsed laser deposition method. The deposition parameters (pressure, temperature, purity of target) play an important role in the mechanical and physicochemical properties. The films have been characterized using X-ray diffraction, atomic force microscopy, Brillouin light scattering, Fourier transform infrared spectroscopy and wettability testing. With a high purity target of AlN and a temperature deposition of 750 ∘C, the measured Rayleigh wave velocity is close to the one previously determined for AlN films grown at high temperature by metal-organic chemical vapour deposition. Growth of nanocrystalline AlN at low temperature and of AlN film with good crystallinity for samples deposited at higher temperature is confirmed by infrared spectroscopy, as it was by atomic force microscopy, in agreement with X-ray diffraction results. A high hydrophobicity has been measured with zero polar contribution for the surface energy. These results confirm that films made by pulsed laser deposition of pure AlN at relatively low temperature have good prospects for microelectromechanical systems applications.

  18. Determination of glucose concentration based on pulsed laser induced photoacoustic technique and least square fitting algorithm

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Huang, Zhen

    2015-08-01

    In this paper, a noninvasive glucose concentration monitoring setup based on the photoacoustic technique was established. In this setup, a 532nm pumped Q switched Nd: YAG tunable pulsed laser with repetition rate of 20Hz was used as the photoacoustic excitation light source, and a ultrasonic transducer with central response frequency of 9.55MHz was used as the detector of the photoacoustic signal of glucose. As the preliminary exploration of the blood glucose concentration, a series of in vitro photoacoustic monitoring of glucose aqueous solutions by using the established photoacoustic setup were performed. The photoacoustic peak-to-peak values of different concentrations of glucose aqueous solutions induced by the pulsed laser with output wavelength of 1300nm to 2300nm in interval of 10nm were obtained with the average times of 512. The differential spectral and the first order derivative spectral method were used to get the characteristic wavelengths. For the characteristic wavelengths of glucose, the least square fitting algorithm was used to establish the relationship between the glucose concentrations and photoacoustic peak-to-peak values. The characteristic wavelengths and the predicted concentrations of glucose solution were obtained. Experimental results demonstrated that the prediction effect of characteristic wavelengths of 1410nm and 1510nm were better than others, and this photoacoustic setup and analysis method had a certain potential value in the monitoring of the blood glucose concentration.

  19. Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO{sub 2}

    SciTech Connect

    Nakahara, Sho; Stauss, Sven; Kato, Toru; Terashima, Kazuo; Sasaki, Takehiko

    2011-06-15

    Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm{sup 2}; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO{sub 2} with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp{sup 3}-hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography-mass spectrometry. Furthermore, gas chromatography-mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO{sub 2} during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO{sub 2} is proposed as a practical method for synthesizing diamondoids.

  20. Effect of focus position of ns pulse laser on damage characteristics of K9 glass

    NASA Astrophysics Data System (ADS)

    Pan, Yunxiang; Zhang, Hongchao; Li, Mengmeng; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2015-05-01

    Laser-induced damage of optical glasses has been investigated for more than fifty years. Due to the residual scratches, inclusions and other forms of defects at surfaces of optical glasses after the processes of grinding and polishing, it is well known that the sample surface can be damaged more easily than bulk. In order to get the relationship between the damage threshold and the location of the laser spot, we carried out damage experiments on K9 glasses with a 7ns pulse laser. Since ns pulse laser-induced damage of optical glasses always accompanies with the generation of the plasma, a optical microscope connected with a CCD camera was used to observe the plasma flash, which can provide a real time detection of damage sites. The laser pulse was first focused into the bulk, then the spot was moved toward the direction of incident laser beam step by step until the beam was completely focused in ambient air. Damage threshold curves were measured for each focus position, and low thresholds and high thresholds were extracted from those curves. Finally, the relationship between damage thresholds and focus position was analyzed.

  1. Comparative study of pulsed laser cleaning applied to weathered marble surfaces

    NASA Astrophysics Data System (ADS)

    Ortiz, P.; Antúnez, V.; Ortiz, R.; Martín, J. M.; Gómez, M. A.; Hortal, A. R.; Martínez-Haya, B.

    2013-10-01

    The removal of unwanted matter from surface stones is a demanding task in the conservation of cultural heritage. This paper investigates the effectiveness of near-infrared (IR) and ultraviolet (UV) laser pulses for the cleaning of surface deposits, iron oxide stains and different types of graffiti (black, red and green sprays and markers, and black cutting-edge ink) on dolomitic white marble. The performance of the laser techniques is compared to common cleaning methods on the same samples, namely pressurized water and chemical treatments. The degree of cleaning achieved with each technique is assessed by means of colorimetric measurements and X-ray microfluorescence. Eventual morphological changes induced on the marble substrate are monitored with optical and electronic microscopy. It is found that UV pulsed laser ablation at 266 nm manages to clean all the stains except the cutting-edge ink, although some degree of surface erosion is produced. The IR laser pulses at 1064 nm can remove surface deposits and black spray acceptably, but a yellowing is observed on the stone surface after treatment. An economic evaluation shows that pulsed laser cleaning techniques are advantageous for the rapid cleaning of small or inaccessible surface areas, although their extensive application becomes expensive due to the long operating times required.

  2. In situ mitigation of subsurface and peripheral focused ion beam damage via simultaneous pulsed laser heating

    SciTech Connect

    Stanford, Michael G.; Lewis, Brett B.; Iberi, Vighter O.; Fowlkes, Jason Davidson; Tan, Shida; Livengood, Rick; Rack, Philip D.

    2016-01-01

    Focused helium and neon ion (He(+)/Ne(+) ) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+) /Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposure process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. In conclusion, these results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams.

  3. Fabricating functionally graded films with designed gradient profiles using pulsed laser deposition

    SciTech Connect

    Won, Yoo Jai; Ki, Hyungson

    2013-05-07

    A novel picosecond-laser pulsed laser deposition method has been developed for fabricating functionally graded films with pre-designed gradient profiles. Theoretically, the developed method is capable of precisely fabricating films with any thicknesses and any gradient profiles by controlling the laser beam powers for the two different targets based on the film composition profiles. As an implementation example, we have successfully constructed functionally graded diamond-like carbon films with six different gradient profiles: linear, quadratic, cubic, square root, cubic root, and sinusoidal. Energy dispersive X-ray spectroscopy is employed for investigating the chemical composition along the thickness of the film, and the deposition profile and thickness errors are found to be less than 3% and 1.04%, respectively. To the best of the authors' knowledge, this is the first method for fabricating films with designed gradient profiles and has huge potential in many areas of coatings and films, including multifunctional optical films. We believe that this method is not only limited to the example considered in this study, but also can be applied to all material combinations as long as they can be deposited using the pulsed laser deposition technique.

  4. In situ mitigation of subsurface and peripheral focused ion beam damage via simultaneous pulsed laser heating

    DOE PAGESBeta

    Stanford, Michael G.; Lewis, Brett B.; Iberi, Vighter O.; Fowlkes, Jason Davidson; Tan, Shida; Livengood, Rick; Rack, Philip D.

    2016-02-16

    Focused helium and neon ion (He(+)/Ne(+) ) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+) /Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposuremore » process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. In conclusion, these results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams.« less

  5. Effect of nanosecond pulse laser ablation on the surface morphology of Zr-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-09-01

    In this study, we investigated the ripple patterns formation on the surface of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass using a nanosecond pulse laser ablation in air with a wavelength of 1064 nm. The strong thermal ablation phenomenon could be observed on vit1 BMG surface at laser energy of 200 mJ as a result of the adhibition of confining overlay. Many periodic ripples had formed on the edge of the ablated area at laser energy of 400 mJ because of the high intensity pulsed laser beam. The underlying mechanism of the periodic ripples formation could be explained by the K-H hydrodynamic instability theory. It had been shown that laser ablation with 600 mJ and 200 pulses results in the formation of many micro-cracks on the ablated area. Further analysis showed that the spatial occupation of the laser ablated area and the spacing between two adjacent ripples increased as the laser energy and the number of incident laser pulses increasing. The surface ripples feature on the edge of ablated area became more obvious with increasing laser pulses, but it was not correlated closely with the laser energies variation.

  6. Shape-dependent magnetic properties of Co nanostructure arrays synthesized by pulsed laser melting

    NASA Astrophysics Data System (ADS)

    Shirato, N.; Sherrill, S.; Gangopadhyay, A. K.; Kalyanaraman, R.

    2016-06-01

    One dimensional (1D) magnetic nanowires show unique magnetic behaviors, such as large coercivity and high remanence, in comparison to the bulk and thin film materials. Here, planar arrays of Co nanowires, nanorods and nanoparticles were fabricated from thin Co films by a nanosecond pulsed laser interference irradiation technique. Magnetic force microscopy (MFM) and surface magneto-optic Kerr effect (SMOKE) techniques were used to study the individual and average magnetic properties of the nanostructures. Magnetic domain orientation was found to depend on the in-plane aspect ratio of the nanostructure. The magnetic orientation was out-of-plane for in-plane aspect ratio ranging from 1 to 1.4 and transitioned to an in-plane orientation for aspect ratios greater than 1.4 (such as in nanorods and nanowires). Our results also showed that polycrystalline Co nanowires showed much higher coercivity and remanence as compared to bulk and thin film materials, as well as shapes with smaller aspect ratio. This result was attributed mainly to the shape anisotropy. This study demonstrated that nanosecond pulsed laser synthesis is capable of fabricating various nanostructures in a simple, robust and rapid manner and SMOKE is a reliable technique to rapidly characterize such magnetic nanostructures.

  7. Monodispersed Nanoparticle Synthesis Using Pulsed Laser Ablation and Application to Opto-electronic Devices

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Suzuki, Nobuyasu; Makino, Toshiharu; Yamada, Yuka

    We report silicon (Si) nanoparticles prepared by pulsed laser ablation in constant pressure inert background gas (PLA-IBG). We demonstrate the synthesis of monodispersed, nonagglomerated Si nanocrystallites, using a novel integrated process system where a classification unit of a low-pressure-operating differential mobility analyzer (LP-DMA) was combined to the PLA-IBG unit. The LP-DMA has been designed to operate under pressures less than 5.0 Torr. We have successfully synthesized and deposited the nonagglomerated Si nanocrystallites of 3.8 nm mean diameter and 1.2 geometrical standard deviation. On the other hand, properties of indium oxide (In2O3) thin films prepared by pulsed laser deposition (PLD) in background gases were characterized in relation to the background gas pressures. Transparent crystalline In2O3 thin films could be obtained at background gas pressures above 1.0 Torr on unheated glass substrates. To develop a near-infrared-light-emitting diode with active materials of monodispersed Si nanocrystallites and with passivation layer of the In2O3 thin films that are highly compatible with ULSI technology. The near-infrared emission was sharp and showed a peak above the band-gap region (position: 1.17 eV, width: 0.15 eV); therefore, it presumably originates from spatial quantum confinement effects of the carriers.

  8. Grain growth of Ni-based superalloy IN718 coating fabricated by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yaocheng; Yang, Li; Dai, Jun; Huang, Zedong; Meng, Tao

    2016-06-01

    The pulsed laser deposited Ni-based superalloy coating was fabricated with successive 12 layers using single tracks. The microstructure of the deposited coating was observed by scanning electron microscopy (SEM). The grain growth and the grain boundary misorientation were investigated by electron backscatter diffraction (EBSD), the precipitation phase was determined by transmission electron microscope (TEM). The results showed that the dendrites were the most common microstructure in the coating, and the dendritic growth orientation was paralleled to the direction of the laser deposition. The dendrite got coarser and its space was increased with increasing laser deposited layers. Most grains grew along the preferential grain orientation <001> and formed anisotropy with grain boundaries misorientation angle about 2° in the pulsed laser deposited coating. The grain size along the texture orientation was 3-10 times larger than that in the transverse orientation. The cross section microhardness of the coating ranged between 240-280 HV, and decreased along the depositional direction due to the reasons of the variation of eutectic morphology, grain size distribution, grain misorientation and a small amounts of strengthening phase precipitation.

  9. Pulsed Laser Deposition Processing of Improved Titanium Nitride Coatings for Implant Applications

    NASA Astrophysics Data System (ADS)

    Haywood, Talisha M.

    Recently surface coating technology has attracted considerable attention of researchers to develop novel coatings with enhanced functional properties such as hardness, biocompatibility, wear and corrosion resistance for medical devices and surgical tools. The materials currently being used for surgical implants include predominantly stainless steel (316L), cobalt chromium (Co-Cr), titanium and its alloys. Some of the limitations of these implants include improper mechanical properties, corrosion resistance, cytotoxicity and bonding with bone. One of the ways to improve the performance and biocompatibility of these implants is to coat their surfaces with biocompatible materials. Among the various coating materials, titanium nitride (TiN) shows excellent mechanical properties, corrosion resistance and low cytotoxicity. In the present work, a systematic study of pulsed laser ablation processing of TiN coatings was conducted. TiN thin film coatings were grown on commercially pure titanium (Ti) and stainless steel (316L) substrates at different substrate temperatures and different nitrogen partial pressures using the pulsed laser deposition (PLD) technique. Microstructural, surface, mechanical, chemical, corrosion and biological analysis techniques were applied to characterize the TiN thin film coatings. The PLD processed TiN thin film coatings showed improvements in mechanical strength, corrosion resistance and biocompatibility when compared to the bare substrates. The enhanced performance properties of the TiN thin film coatings were a result of the changing and varying of the deposition parameters.

  10. A high performance constant fraction discriminator for pulsed laser proximity fuze

    NASA Astrophysics Data System (ADS)

    Yao, Ping-ping; Tu, Bi-hai; Wang, Xiang-jing; Zhang, Yi; Zhao, Ping-jian

    2015-04-01

    A novel high performance timing discrimination circuit architecture for a pulsed laser proximity fuze based on constant fraction discrimination technique is constructed and tested. A LC resonant circuit is designed to replace the traditional transmission delay-line to accommodate the special requirements of laser proximity fuze for low size, power consumption, weight and cost. The walk error of the improved constant fraction discriminator is analyzed with lots of detailed experiments. The experiment results indicate that the discriminator eliminates the dependency of the echo pulse amplitude from the timing result, the walk error caused by the amplitude variation and the noise variation of the received echo pulse is less than 125ps, when the SNR is more than 20 and the echo pulse is 0.2V to 2.134V (20.12dB dynamic range). The error is less than 100ps when the SNR more than 60. Furthermore, Detection on the whole system integrating the timing discrimination circuit verifies that, the laser repetition frequency can reach 10 KHz, the accuracy of the system with a measurement time of 0.1ms is 1.45cm in the case of a noncooperative target at a measurement range from 2m to 24m at room temperature, which improve greatly the fixed distance precision of pulsed laser proximity fuze.

  11. Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

    NASA Astrophysics Data System (ADS)

    Ilgner, Justus F. R.; Wehner, Martin M.; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

    2006-01-01

    We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10µm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20µm, pulse rate 10 kHz, power 160-1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 µJ, beam diameter 36 µm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mm/s. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

  12. Environmental resistance of oxide tags fabricated on 304L stainless steel via nanosecond pulsed laser irradiation

    DOE PAGESBeta

    Lawrence, Samantha Kay; Adams, David P.; Bahr, David F.; Moody, Neville R.

    2015-11-14

    Nanosecond pulsed laser irradiation was used to fabricate colored, mechanically robust oxide “tags” on 304L stainless steel. Immersion in simulated seawater solution, salt fog exposure, and anodic polarization in a 3.5% NaCl solution were employed to evaluate the environmental resistance of these oxide tags. Single layer oxides outside a narrow thickness range (~ 100–150 nm) are susceptible to dissolution in chloride containing environments. The 304L substrates immediately beneath the oxides corrode severely—attributed to Cr-depletion in the melt zone during laser processing. For the first time, multilayered oxides were fabricated with pulsed laser irradiation in an effort to expand the protectivemore » thickness range while also increasing the variety of film colors attainable in this range. Layered films grown using a laser scan rate of 475 mm/s are more resistant to both localized and general corrosion than oxides fabricated at 550 mm/s. Furthermore, in the absence of pre-processing to mitigate Cr-depletion, layered films can enhance environmental stability of the system.« less

  13. Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Melaibari, Ammar A.; Molian, Pal

    2012-11-01

    Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered "brick-bridge-mortar" nacre of AlMgB14 (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB14. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB14/Ti system revealed that the brick is to be 250 nm thick, 9 μm lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.

  14. Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers

    SciTech Connect

    Melaibari, Ammar A.; Molian, Pal

    2012-11-15

    Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered 'brick-bridge-mortar' nacre of AlMgB{sub 14} (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB{sub 14}. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB{sub 14}/Ti system revealed that the brick is to be 250 nm thick, 9 {mu}m lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.

  15. Evidence of superior ferroelectricity in structurally welded ZnSnO3 nanowire arrays.

    PubMed

    Datta, Anuja; Mukherjee, Devajyoti; Kons, Corisa; Witanachchi, Sarath; Mukherjee, Pritish

    2014-10-29

    Highly packed LN-type ZnSnO3 NW arrays are grown on ZnO:Al/Si substrates using a hybrid pulsed laser deposition and solvothermal process. Unique "welding" mechanism structurally joins adjacent ZnSnO3 NWs to form a nearly impervious 20 μm thick nanostructured film that shows high P r of 30 μC/cm(2) at a low E c of 25 kV/cm for the first time. PMID:24955557

  16. Advanced Welding Concepts

    NASA Technical Reports Server (NTRS)

    Ding, Robert J.

    2010-01-01

    Four advanced welding techniques and their use in NASA are briefly reviewed in this poster presentation. The welding techniques reviewed are: Solid State Welding, Friction Stir Welding (FSW), Thermal Stir Welding (TSW) and Ultrasonic Stir Welding.

  17. Implications of the spatial dependence of the single-event-upset threshold in SRAMs measured with a pulsed laser

    SciTech Connect

    Buchner, S. SFA Inc., Landover, MD ); Langworthy, J.B.; Stapor, W.J.; Campbell, A.B. ); Rivet, S. )

    1994-12-01

    Pulsed laser light was used to measure single event upset (SEU) thresholds for a large number of memory cells in both CMOS and bipolar SRAMs. Results showed that small variations in intercell upset threshold could not explain the gradual rise in the curve of cross section versus linear energy transfer (LET). The memory cells exhibited greater intracell variations implying that the charge collection efficiency within a memory cell varies spatially and contributes substantially to the shape of the curve of cross section versus LET. The results also suggest that the pulsed laser can be used for hardness-assurance measurements on devices with sensitive areas larger than the diameter of the laser beam.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  19. Pulsed laser ablation plasmas generated in CO{sub 2} under high-pressure conditions up to supercritical fluid

    SciTech Connect

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

    2012-11-26

    Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO{sub 2} at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

  20. Nanopatterns induced by pulsed laser irradiation on the surface of an Fe-Al alloy and their magnetic properties

    SciTech Connect

    Yoshida, Yutaka; Oosawa, Kazuya; Watanabe, Seiichi; Kaiju, Hideo; Kondo, Kenji; Ishibashi, Akira; Yoshimi, Kyosuke

    2013-05-06

    We have studied nanopatterns induced by nanosecond pulsed laser irradiation on (111) plane surfaces of a polycrystalline iron-aluminum alloy and evaluated their magnetic properties. Multiple nanosecond pulsed laser irradiation induces a wavelength-dependent surface transformation of the lattice structure from a B2-type to a supersaturated body centered cubic lattice. The selective formation of surface nanopatterns consisting of holes, stripes, polygonal networks, and dot-like nanoprotrusions can be observed. Furthermore, focused magneto-optical Kerr effect measurements reveal that the magnetic properties of the resultant nanostructured region changes from a paramagnetic to a ferromagnetic phase in accordance with the number of laser pulses.

  1. Infrared Pulse-laser Long-path Absorption Measurement of Carbon Dioxide Using a Raman-shifted Dye Laser

    NASA Technical Reports Server (NTRS)

    Minato, Atsushi; Sugimoto, Nobuo; Sasano, Yasuhiro

    1992-01-01

    A pulsed laser source is effective in infrared laser long-path absorption measurements when the optical path length is very long or the reflection from a hard target is utilized, because higher signal-to-noise ratio is obtained in the detection of weak return signals. We have investigated the performance of a pulse-laser long-path absorption system using a hydrogen Raman shifter and a tunable dye laser pumped by a Nd:YAG laser, which generates second Stokes radiation in the 2-micron region.

  2. Crystalline garnet Bragg reflectors for high power, high temperature, and integrated applications fabricated by multi-beam pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Sloyan, Katherine A.; May-Smith, Timothy C.; Zervas, Michalis N.; Eason, Robert W.

    2012-08-01

    Crystalline Bragg reflectors are of interest for high power, high temperature, and integrated applications. We demonstrate the automated growth of such structures by shuttered multi-beam pulsed laser deposition. Geometries include 145 layer stacks exhibiting >99.5% reflection and π phase-shifted designs. A crystalline grating strength-apodized sample was grown by mixing plumes to obtain layers with custom refractive indices. Peak reflection wavelength was tuneable with incident position, samples withstood temperatures of ˜750 °C, and film and substrate have been shown to withstand incident pulsed laser fluences of up to ˜33 J cm-2.

  3. Effects of electrode bevel angle on argon arc properties and weld shape

    NASA Astrophysics Data System (ADS)

    Dong, W. C.; Lu, S. P.; Li, D. Z.; Y Li, Y.

    2012-07-01

    A numerical modeling of coupled welding arc with weld pool is established using FLUENT software for moving shielded GTA welding to systematically investigate the effects of electrode bevel angle on the argon arc properties as well as the weld shape on SUS304 stainless steel. The calculated results show that the argon arc is constricted and the peak values of heat flux and shear stress on the weld pool decrease with increasing electrode bevel angle, while the radial distribution of heat flux and shear stress varying slightly. The weld shape is controlled by the pool flow patterns driving by the surface tension, gas shear stress, electromagnetic force and buoyancy. The Marangoni convection induced by surface tension plays an important role on weld shapes. All the weld shapes are wide and shallow with low weld metal oxygen content, while the narrow and deep weld shapes form under high weld metal oxygen content, which is related with the oxygen concentration in the shielding gas. The weld depth/width (D/W) ratio increases with increasing electrode bevel angle for high weld metal oxygen content and is not sensitive to the electrode bevel angle under low weld metal oxygen content. The calculated results for the weld shape, weld size and weld D/W ratio agree well with the experimental ones.

  4. Simulation of temperature fields in arc and beam welding

    NASA Astrophysics Data System (ADS)

    Mahrle, A.; Schmidt, J.; Weiss, D.

    Heat and mass transfer in arc and beam welding is considered. The main objectives are analysis of the heat transfer in the weld pool and the workpiece and to demonstrate how computer simulation can be used as a tool to predict the temperature distribution as the determining element of the heat effects of welding. Simulation results of two particular welding processes are compared and validated with measurements.

  5. Surface Engineering of Silicon and Carbon by Pulsed-Laser Ablation

    SciTech Connect

    Fowlkes, J.D.; Geohegan, D.B.; Jellison, G.E., Jr.; Lowndes, D.H.; Merkulov, V.I.; Pedraza, A.J.; Puretzky, A.A.

    1999-02-28

    Experiments are described in which a focused pulsed-excimer laser beam is used either to ablate a graphite target and deposit hydrogen-free amorphous carbon films, or to directly texture a silicon surface and produce arrays of high-aspect-ratio silicon microcolumns. In the first case, diamond-like carbon (or tetrahedral amorphous carbon, ta-C) films were deposited with the experimental conditions selected so that the masses and kinetic energies of incident carbon species were reasonably well controlled. Striking systematic changes in ta-C film properties were found. The sp{sup 3}-bonded carbon fraction, the valence electron density, and the optical (Tauc) energy gap ail reach their maximum values in films deposited at a carbon ion kinetic energy of {approximately}90 eV. Tapping-mode atomic force microscope measurements also reveal that films deposited at 90 eV are extremely smooth (rms roughness {approximately}1 {angstrom} over several hundred nm) and relatively free of particulate, while the surface roughness increases in films deposited at significantly lower energies. In the second set of experiments, dense arrays of high-aspect-ratio silicon microcolumns {approximately}20-40 {micro}m tall and {approximately}2 {micro}m in diameter were formed by cumulative nanosecond pulsed excimer laser irradiation of silicon wafers in air and other oxygen-containing atmospheres. It is proposed that microcolumn growth occurs through a combination of pulsed-laser melting of the tips of the columns and preferential redeposition of silicon on the molten tips from the ablated flux of silicon-rich vapor. The common theme in this research is that a focused pulsed-laser beam can be used quite generally to create an energetic flux, either the energetic carbon ions needed to form sp{sup 3} (diamond-like) bonds or the overpressure of silicon-rich species needed for microcolumn growth. Thus, new materials synthesis opportunities result from the access to nonequilibrium growth conditions

  6. Pulsed laser deposition of AlMgB14 thin films

    SciTech Connect

    Britson, Jason Curtis

    2008-11-18

    Hard, wear-resistant coatings of thin film borides based on AlMgB14 have the potential to be applied industrially to improve the tool life of cutting tools and pump vanes and may account for several million dollars in savings as a result of reduced wear on these parts. Past work with this material has shown that it can have a hardness of up to 45GPa and be fabricated into thin films with a similar hardness using pulsed laser deposition. These films have already been shown to be promising for industrial applications. Cutting tools coated with AlMgB14 used to mill titanium alloys have been shown to substantially reduce the wear on the cutting tool and extend its cutting life. However, little research into the thin film fabrication process using pulsed laser deposition to make AlMgB14 has been conducted. In this work, research was conducted into methods to optimize the deposition parameters for the AlMgB14 films. Processing methods to eliminate large particles on the surface of the AlMgB14 films, produce films that were at least 1m thick, reduce the surface roughness of the films, and improve the adhesion of the thin films were investigated. Use of a femtosecond laser source rather than a nanosecond laser source was found to be effective in eliminating large particles considered detrimental to wear reduction properties from the films. Films produced with the femtosecond laser were also found to be deposited at a rate 100 times faster than those produced with the nanosecond laser. However, films produced with the femtosecond laser developed a relatively high RMS surface roughness around 55nm. Attempts to decrease the surface roughness were largely unsuccessful. Neither increasing the surface temperature of the substrate during deposition nor using a double pulse to ablate the material was found to be extremely successful to reduce the surface roughness. Finally, the adhesion of the thin films to M2 tool steel

  7. Mathematical modeling and experimental validation of gas metal arc welding of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Guo, Hao

    2004-11-01

    Both mathematical modeling and experiments have been conducted on the GMAW of aluminum alloys. Transient weld shapes and distributions of temperature and velocity were calculated by a three-dimensional numerical model. The final weld bead shape and dimensions and peak temperature in the heat-affected zone (HAZ) were obtained. Metallurgical characterizations including microscopy and Knoop micro-hardness measurements were performed on experimental samples. The experimental weld bead shape and dimensions were in agreement with modeling predictions. It was found that a crater-shaped weld pool was formed as a result of weld pool dynamics. The combined effect of a series of droplet impingements and hydrostatic force caused the fluid level at the rear end of weld pool to vary periodically to form ripples on the weld bead. Also, the high peak temperature near the fusion line caused the HAZ softening. The lack of penetration in the cold weld is due to the lack of pre-heating by the welding arc. Three techniques were then proposed to increase the energy input at the initial stage of welding and improve cold weld penetration. The crater formation at the end of the welding process is due to the rapid solidification of the weld pool. The crater was filled and crater cracking was reduced by reducing welding current and reversing the welding direction at the same time before terminating the arc.

  8. Welding Technician

    ERIC Educational Resources Information Center

    Smith, Ken

    2009-01-01

    About 95% of all manufactured goods in this country are welded or joined in some way. These welded products range in nature from bicycle handlebars and skyscrapers to bridges and race cars. The author discusses what students need to know about careers for welding technicians--wages, responsibilities, skills needed, career advancement…

  9. Keyhole Welding: The Solid and Liquid Phases

    NASA Astrophysics Data System (ADS)

    Kaplan, Alexander

    Deep penetration laser welding relies on the evaporation of material by a high power laser beam in order to drill a vapour capillary, usually referred to as a keyhole. During continuous welding the keyhole is kept open by the pressure in the vapour which evaporates continuously from its wall; the pressure acts continuously against the surface tension pressure that favours contraction. In contrast to pulsed wave (pw-) laser welding, during continuous wave (cw-) laser welding quasi-steady state conditions of the accompanying temperature field, and thus of the shape of the keyhole and melt pool, are established. Nevertheless, in the keyhole and melt pool complex fluid mechanical mechanisms take place. The most important thermodynamic and melt flow phenomena in keyhole laser welding will be briefly discussed. For some of them mathematical models and calculation results will be presented, complementing a comprehensive survey that was published earlier [1].

  10. Red photoluminescence in praseodymium-doped titanate perovskite films epitaxially grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Takashima, Hiroshi; Ueda, Kazushige; Itoh, Mitsuru

    2006-12-01

    Intense red photoluminescence (PL) under ultraviolet (UV) excitation was observed in epitaxially grown Pr-doped Ca0.6Sr0.4TiO3 perovskite films. The films were grown on SrTiO3 (100) substrates by pulsed laser deposition, and their epitaxial growth was confirmed by x-ray diffraction and reflected high-energy electron diffraction. The observed sharp PL peak centered at 610nm was assigned to the transition of Pr3+ ions from the D21 state to the H43 state. The PL intensity was markedly enhanced by postannealing treatments at 1000°C, above the film-growth temperature of 600 or 800°C. Because the excitation and absorption spectra are similar to each other, it was suggested that the UV energy absorbed by the host lattice was transferred to the Pr ions, resulting in the red luminescence.

  11. Research Update: Stoichiometry controlled oxide thin film growth by pulsed laser deposition

    SciTech Connect

    Groenen, Rik; Smit, Jasper; Orsel, Kasper; Vailionis, Arturas; Bastiaens, Bert; Huijben, Mark; Boller, Klaus; Rijnders, Guus; Koster, Gertjan

    2015-07-01

    The oxidation of species in the plasma plume during pulsed laser deposition controls both the stoichiometry as well as the growth kinetics of the deposited SrTiO{sub 3} thin films, instead of the commonly assumed mass distribution in the plasma plume and the kinetic energy of the arriving species. It was observed by X-ray diffraction that SrTiO{sub 3} stoichiometry depends on the composition of the background gas during deposition, where in a relative small pressure range between 10{sup −2} mbars and 10{sup −1} mbars oxygen partial pressure, the resulting film becomes fully stoichiometric. Furthermore, upon increasing the oxygen (partial) pressure, the growth mode changes from 3D island growth to a 2D layer-by-layer growth mode as observed by reflection high energy electron diffraction.

  12. Electrochemical and electrochromic properties of niobium oxide thin films fabricated by pulsed laser deposition

    SciTech Connect

    Fu, Z.W.; Kong, J.J.; Qin, Q.Z.

    1999-10-01

    Niobium oxide thin films have been successfully fabricated on the indium-tin oxide coated glasses by pulsed laser deposition in an O{sub 3}/O{sub 2} gas mixture. Films are characterized by X-ray diffraction and Raman spectrometry. Electrochemical and electrochromic properties of Nb{sub 2}O{sub 5} films are examined by cyclic voltammogram and potential step coupled with an in situ charge-coupled device spectrophotometer. The unique characteristics of absorption spectra of Nb{sub 2}O{sub 5} films are observed for the first time, and the optical absorption from the trapped electrons in the surface states plays an important role in the electrochromic phenomenon.

  13. Permanent data recording in transparent materials by using a nanojoule-class pulse laser

    NASA Astrophysics Data System (ADS)

    Imai, Ryo; Shiozawa, Manabu; Watanabe, Takao; Umeda, Mariko; Mine, Toshiyuki; Kuretake, Satoshi; Watanabe, Koichi

    2014-09-01

    We investigated data recording for permanent data storage using an ultrafast pulse laser with nanojoule-class pulse energy and megahertz-class repetition rate in transparent materials, and driveless reading based on a simple imaging system. A transparent ceramics called Lumicera®, manufactured by Murata Mfg. Co., Ltd., was used as the recording medium. Lumicera® has a lower modification threshold and a higher recording sensitivity than those of silica glass, namely, the medium previously studied. Structural modification in Lumicera® occurs by light exposure for 10 μs, suggesting that Lumicera® has potential for a recording speed of over 100 kbps. Data recorded in Lumicera® resists heating for 2 h at 1000 °C and is expected to have a lifetime of over 300 million years. Moreover, the data recorded in Lumicera® was successfully read with a reading system based on a smart phone.

  14. Short-Pulse Laser Sintering of Multilayer Hard Metal Coatings: Structure and Wear Behavior

    NASA Astrophysics Data System (ADS)

    Kharanzhevskiy, Evgeny; Ipatov, Alexey; Nikolaeva, Irina; Zakirova, Raushaniya

    2015-06-01

    This paper reports on the phase composition and properties of multilayer hard metal coatings deposited on steel by a process variant of Selective laser melting (SLM). The process is based on layer-wise short-pulse laser sintering of high-dispersive WC-Co powder on a steel substrate. High temperature in the molten zone and chemical interaction with the substrate explain high level of adhesion strength between the coating and the substrate. The technique allows obtaining both high quality hard-metal multilayer gradient coatings with thickness up to 200 μm, density near to the theoretical density (TD), hardness up to 21 GPa and complex 3D objects by layer-wise powder based process such as SLM.

  15. Research of metallic materials irradiation with high energy pulsed laser impact

    NASA Astrophysics Data System (ADS)

    Blesman, A. I.; Postnikov, D. V.; Seropyan, G. M.; Tkachenko, E. A.; Teplouhov, A. A.; Polonyankin, D. A.

    2016-02-01

    In the process of metallic materials treatment by pulsed laser beams with nanosecond duration occurs extremely rapid and intensive heating of their surface. In this case a thin surface layer of material is heated to the boiling point and rapidly evaporates. This leads to arising substantial forces of reactive nature which significantly influence on the shape of the solidified melt and in some cases may cause deformation of the underlying layers. The considered question is relevant in the research of precision treatment of miniature products by laser beams. A metallic powder with microfine material structure was selected as the object of research and was exposed to laser irradiation with nanosecond duration. At the core of reactive forces calculation used the approach similar for laser rocket engines. The paper also presents the model and the results of the forces and the reactive recoil impulse calculation occurring during laser impact to the microfine metallic powder.

  16. Monochromatic short pulse laser produced ion beam using a compact passive magnetic device

    SciTech Connect

    Chen, S. N.; Gauthier, M.; Higginson, D. P.; Dorard, S.; Marquès, J.-R.; Fuchs, J.; Mangia, F.; Atzeni, S.; Riquier, R.; CEA, DAM, DIF, F-91297 Arpajon

    2014-04-15

    High-intensity laser accelerated protons and ions are emerging sources with complementary characteristics to those of conventional sources, namely high charge, high current, and short bunch duration, and therefore can be useful for dedicated applications. However, these beams exhibit a broadband energy spectrum when, for some experiments, monoenergetic beams are required. We present here an adaptation of conventional chicane devices in a compact form (10 cm × 20 cm) which enables selection of a specific energy interval from the broadband spectrum. This is achieved by employing magnetic fields to bend the trajectory of the laser produced proton beam through two slits in order to select the minimum and maximum beam energy. The device enables a production of a high current, short duration source with a reproducible output spectrum from short pulse laser produced charged particle beams.

  17. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel.

    PubMed

    Dmitrieva, O; Choi, P; Gerstl, S S A; Ponge, D; Raabe, D

    2011-05-01

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. PMID:21215524

  18. Photoresponse in thin films of WO{sub 3} grown by pulsed laser deposition

    SciTech Connect

    Roy Moulik, Samik; Samanta, Sudeshna; Ghosh, Barnali

    2014-06-09

    We report, the photoresponse behaviour of Tungsten trioxide (WO{sub 3}) films of different surface morphology, grown by using pulsed laser deposition (PLD). The Growth parameters for PLD were changed for two substrates SiO{sub 2}/Si (SO) and SrTiO{sub 3} (STO), such a way which, result nanocrystalline film on SO and needle like structured film on STO. The photoresponse is greatly modified in these two films because of two different surface morphologies. The nanocrystalline film (film on SO) shows distinct photocurrent (PC) ON/OFF states when light was turned on/off, the enhancement of PC is ∼27%. Whereas, the film with needle like structure (film on STO) exhibits significantly enhanced persistent photocurrent even in light off condition, in this case, the enhancement of PC ∼ 50% at room temperature at lowest wavelength (λ = 360 nm) at a nominal bias voltage of 0.1 V.

  19. Bismuth Oxide Thin Films Deposited on Silicon Through Pulsed Laser Ablation, for Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Condurache-Bota, Simona; Constantinescu, Catalin; Tigau, Nicolae; Praisler, Mirela

    2016-12-01

    Infrared detectors are used in many human activities, from industry to military, telecommunications, environmental studies and even medicine. Bismuth oxide thin films have proved their potential for optoelectronic applications, but their uses as infrared sensors have not been thoroughly studied so far. In this paper, pulsed laser ablation of pure bismuth targets within a controlled oxygen atmosphere is proposed for the deposition of bismuth oxide films on Si (100) substrates. Crystalline films were obtained, whose uniformity depends on the deposition conditions (number of laser pulses and the use of a radio-frequency (RF) discharge of the oxygen inside the deposition chamber). The optical analysis proved that the refractive index of the films is higher than 3 and that their optical bandgap is around 1eV, recommending them for infrared applications.

  20. Intensity evaluation using a femtosecond pulse laser for absolute distance measurement.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Li, Jianshuang; Cao, Shiying; Meng, Xiangsong; Qu, Xinghua

    2015-06-10

    In this paper, we propose a method of intensity evaluation based on different pulse models using a femtosecond pulse laser, which enables long-range absolute distance measurement with nanometer precision and large non-ambiguity range. The pulse cross-correlation is analyzed based on different pulse models, including Gaussian, Sech(2), and Lorenz. The DC intensity and the amplitude of the cross-correlation patterns are also demonstrated theoretically. In the experiments, we develop a new combined system and perform the distance measurements on an underground granite rail system. The DC intensity and amplitude of the interference fringes are measured and show a good agreement with the theory, and the distance to be determined can be up to 25 m using intensity evaluation, within 64 nm deviation compared with a He-Ne incremental interferometer, and corresponds to a relative precision of 2.7×10(-9). PMID:26192864

  1. Synthesis by pulsed laser ablation of 2D nanostructures for advanced biomedical sensing

    NASA Astrophysics Data System (ADS)

    Trusso, S.; Zanchi, C.; Bombelli, A.; Lucotti, A.; Tommasini, M.; de Grazia, U.; Ciusani, E.; Romito, L. M.; Ossi, P. M.

    2016-05-01

    Au nanoparticle arrays with controlled nanostructure were produced by pulsed laser ablation on glass. Such substrates were optimized for biomedical sensing by means of SERS keeping fixed all process parameters but the laser pulse (LP) number that is a key deposition parameter. It allows to fine-tune the Au surface nanostructure with a considerable improvement in the SERS response towards the detection of apomorphine in blood serum (3.3 × 10‑6 M), when LP number is increased from 1 × 104 to 2 × 104. This result is the starting point to correlate the intensity of selected SERS signals of apomorphine to its concentration in the blood of patients with Parkinson's disease.

  2. Applications of tunable high energy/pressure pulsed lasers to atmospheric transmission and remote sensing

    NASA Technical Reports Server (NTRS)

    Hess, R. V.; Seals, R. K.

    1974-01-01

    Atmospheric transmission of high energy C12 O2(16) lasers were improved by pulsed high pressure operation which, due to pressure broadening of laser lines, permits tuning the laser 'off' atmospheric C12 O2(16) absorption lines. Pronounced improvement is shown for horizontal transmission at altitudes above several kilometers, and for vertical transmission through the entire atmosphere. The atmospheric transmission of tuned C12 O2(16) lasers compares favorably with C12 O2(18) isotope lasers and CO lasers. The advantages of tunable, high energy, high pressure pulsed lasers over tunable diode lasers and waveguide lasers, in combining high energies with a large tuning range, are evaluated for certain applications to remote sensing of atmospheric constituents and pollutants. Pulsed operation considerably increases the signal to noise ratio without seriously affecting the high spectral resolution of signal detection obtained with laser heterodyning.

  3. Phase-selective vanadium dioxide (VO{sub 2}) nanostructured thin films by pulsed laser deposition

    SciTech Connect

    Masina, B. N. E-mail: slafane@cdta.dz; Lafane, S. E-mail: slafane@cdta.dz; Abdelli-Messaci, S.; Kerdja, T.; Wu, L.; Akande, A. A.; Mwakikunga, B.

    2015-10-28

    Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO{sub 2}) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ∼43 °C, without any doping, paving the way to switchable transparency in optical materials at room temperature.

  4. Pulsed laser micromachining of Mg-Cu-Gd bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Lin, Hsuan-Kai; Lee, Ching-Jen; Hu, Ting-Ting; Li, Chun-Han; Huang, J. C.

    2012-06-01

    Micromachining of Mg-based bulk metallic glasses (BMGs) is performed using two kinds of pulsed nanosecond lasers: a 355 nm ultraviolet (UV) laser and a 1064 nm infrared (IR) laser. Precision machining on the micrometer scale and the preservation of amorphous or short-range order characteristics are important for the application of BMGs in micro-electro-mechanical systems. A higher micromachining rate is achieved using the UV laser than using the IR laser due to a better absorption rate of the former by Mg-based BMGs and a higher photon energy. The cutting depth of Mg-based BMGs ranges from 1 to 80 μm depending on the laser parameters. By appropriate adjustment of the laser power and scan speed, successful machining of the Mg-based BMG with preservation of the amorphous phase is achieved after the laser irradiation process. Short-pulse laser cutting represents a suitable alternative for machining of micro components.

  5. Proton Transport and Microstructure Properties in Superlattice Thin Films Fabricated by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Kuwata, Naoaki; Sata, Noriko; Tsurui, Takao; Yugami, Hiroo

    2005-12-01

    Superlattice thin films of the perovskite-type oxide proton conductor SrZr0.95Y0.05O3/SrTiO3 was fabricated by pulsed laser deposition. Their structural and proton transport properties were reported. X-ray diffraction analysis and selected area electron diffraction revealed that the thin films were epitaxially grown on MgO(001) substrate. High-density edge dislocations and a columnar structure were observed in the films by high-resolution electron microscopy. The in-plane electrical conductivity of the thin films was determined by impedance spectroscopy. The contribution of proton transport to the total conductivity of the films was confirmed by H2O/D2O exchange measurement. The conductivity of superlattice films was increased by introducing heterointerfaces. The high activation energy (Ea=1.0 eV) was explained by the grain-boundary effect of the columnar structure in the films.

  6. Amorphous indium gallium zinc oxide thin film grown by pulse laser deposition technique

    NASA Astrophysics Data System (ADS)

    Mistry, Bhaumik V.; Joshi, U. S.

    2016-05-01

    Highly electrically conducting and transparent in visible light IGZO thin film were grown on glass substrate at substrate temperature of 400 C by a pulse laser deposition techniques. Structural, surface, electrical, and optical properties of IGZO thin films were investigated at room temperature. Smooth surface morphology and amorphous nature of the film has been confirmed from the AFM and GIXRD analysis. A resistivity down to 7.7×10-3 V cm was reproducibly obtained while maintaining optical transmission exceeding 70% at wavelengths from 340 to 780 nm. The carrier densities of the film was obtain to the value 1.9×1018 cm3, while the Hall mobility of the IGZO thin film was 16 cm2 V-1S-1.

  7. Combinatorial pulsed laser deposition of Fe/MgO granular multilayers

    NASA Astrophysics Data System (ADS)

    García-García, A.; Pardo, J. A.; Navarro, E.; Štrichovanec, P.; Vovk, A.; Morellón, L.; Algarabel, P. A.; Ibarra, M. R.

    2012-06-01

    Combinatorial pulsed laser deposition (PLD) makes use of the angular spread of laser-ablated material to prepare thin films with lateral compositional gradient. In this paper we have used combinatorial PLD to grow discontinuous Fe/MgO multilayers by alternate ablation from two separate Fe and MgO targets. Films of composition [Fe( t Fe)/MgO( t MgO)]15 were deposited on glass substrates. The thickness of Fe and MgO were varied in the vicinity of critical values determined in previous studies to maximize the tunneling magnetoresistance (TMR) in the current-in-plane configuration. Optimized multilayers show a substantial improvement of both TMR and field sensitivity at room temperature.

  8. Investigation on two magnon scattering processes in pulsed laser deposited epitaxial nickel zinc ferrite thin film

    NASA Astrophysics Data System (ADS)

    Roy, Debangsu; Sakshath, S.; Singh, Geetanjali; Joshi, Rajeev; Bhat, S. V.; Kumar, P. S. Anil

    2015-04-01

    Ferromagnetic resonance (FMR) measurements are employed to evaluate the presence of the two magnon scattering contribution in the magnetic relaxation processes of the epitaxial nickel zinc ferrite thin films deposited using pulsed laser deposition (PLD) on the (0 0 1) MgAl2O4 substrate. Furthermore, the reciprocal space mapping reveals the presence of microstructural defects which acts as an origin for the two magnon scattering process in this thin film. The relevance of this scattering process is further discussed for understanding the higher FMR linewidth in the in-plane configuration compared to the out-of-plane configuration. FMR measurements also reveal the presence of competing uniaxial and cubic anisotropy in the studied films.

  9. Ge1-xSnx alloys synthesized by ion implantation and pulsed laser melting

    NASA Astrophysics Data System (ADS)

    Gao, Kun; Prucnal, S.; Huebner, R.; Baehtz, C.; Skorupa, I.; Wang, Yutian; Skorupa, W.; Helm, M.; Zhou, Shengqiang

    2014-07-01

    The tunable bandgap and the high carrier mobility of Ge1-xSnx alloys stimulate a large effort for bandgap and strain engineering for Ge based materials using silicon compatible technology. In this Letter, we present the fabrication of highly mismatched Ge1-xSnx alloys by ion implantation and pulsed laser melting with Sn concentration ranging from 0.5 at. % up to 1.5 at. %. According to the structural investigations, the formed Ge1-xSnx alloys are monocrystalline with high Sn-incorporation rate. The shrinkage of the bandgap of Ge1-xSnx alloys with increasing Sn content is proven by the red-shift of the E1 and E1 + Δ1 critical points in spectroscopic ellipsometry. Our investigation provides a chip technology compatible route to prepare high quality monocrystalline Ge1-xSnx alloys.

  10. Li-rich Thin Film Cathode Prepared by Pulsed Laser Deposition

    PubMed Central

    Yan, Binggong; Liu, Jichang; Song, Bohang; Xiao, Pengfei; Lu, Li

    2013-01-01

    Li-rich layer-structured cathode thin films are prepared by pulsed laser deposition. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing in half battery cells are used to characterize crystal structure, surface morphology, chemical valence states and electrochemical performance of these thin films, respectively. It is observed that partial layer to spinel transformation takes place during post annealing, and the layered structure further gradually transforms to spinel during electrochemical cycling based on the analysis of dQ/dV. Electrochemical measurement shows that the thin film electrode deposited at 350 mTorr and post-annealed at 800°C possesses the best performance. PMID:24276678

  11. Optical properties of zinc phthalocyanine thin films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Novotny, M.; Bulir, J.; Bensalah-Ledoux, A.; Guy, S.; Fitl, P.; Vrnata, M.; Lancok, J.; Moine, B.

    2014-10-01

    ZnPc thin films were prepared by pulsed laser deposition (KrF laser, λ = 248 nm, τ = 5 ns, f = 50 Hz) on suprasil substrates in vacuum. Optical properties in UV-Vis spectral region were analyzed as functions of laser fluence from 40 to 100 mJ/cm2 by spectrophotometric and spectral ellipsometry measurements. The spectral ellipsometry data were treated using a three-layer model (substrate, film, roughness). The best results of data fitting were obtained when Q band was characterized by two Lorentz oscillators, while two Gaussian oscillators were used for B and C band fitting. We derived the band gap using Tauc plot considering ZnPc a direct band gap semiconductor. The band gap values were found decreasing from 3.13 to 3.09 eV with increasing laser fluence, which might be related with formation of trapping sites at higher fluence.

  12. D-shaped fiber grating refractive index sensor induced by an ultrashort pulse laser.

    PubMed

    Liao, Changrui; Wang, Qiao; Xu, Lei; Liu, Shen; He, Jun; Zhao, Jing; Li, Zhengyong; Wang, Yiping

    2016-03-01

    The fabrication of fiber Bragg gratings was here demonstrated using ultrashort pulse laser point-by-point inscription. This is a very convenient means of creating fiber Bragg gratings with different grating periods and works by changing the translation speed of the fiber. The laser energy was first optimized in order to improve the spectral properties of the fiber gratings. Then, fiber Bragg gratings were formed into D-shaped fibers for use as refractive index sensors. A nonlinear relationship was observed between the Bragg wavelength and liquid refractive index, and a sensitivity of ∼30  nm/RIU was observed at 1.450. This shows that D-shaped fiber Bragg gratings might be used to develop promising biochemical sensors. PMID:26974608

  13. Epithermal Neutron Source for Neutron Resonance Spectroscopy (NRS) using High Intensity, Short Pulse Lasers

    SciTech Connect

    Higginson, D P; McNaney, J M; Swift, D C; Bartal, T; Hey, D S; Pape, S L; Mackinnon, A; Mariscal, D; Nakamura, H; Nakanii, N; Beg, F N

    2010-04-22

    A neutron source for neutron resonance spectroscopy (NRS) has been developed using high intensity, short pulse lasers. This measurement technique will allow for robust measurements of interior ion temperature of laser-shocked materials and provide insight into equation of state (EOS) measurements. The neutron generation technique uses protons accelerated by lasers off of Cu foils to create neutrons in LiF, through (p,n) reactions with {sup 7}Li and {sup 19}F. The distribution of the incident proton beam has been diagnosed using radiochromic film (RCF). This distribution is used as the input for a (p,n) neturon prediction code which is compared to experimentally measured neutron yields. From this calculation, a total fluence of 1.8 x 10{sup 9} neutrons is infered, which is shown to be a reasonable amount for NRS temperature measurement.

  14. ZnSe and ZnO film growth by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Ryu, Y. R.; Zhu, S.; Han, S. W.; White, H. W.; Miceli, P. F.; Chandrasekhar, H. R.

    1998-05-01

    ZnSe and ZnO films have been deposited on (001) GaAs substrates under different pressures by pulsed-laser deposition (PLD) with a 193 nm laser beam. The ambient pressures were changed from 8×10 -6 to 5×10 -2 Torr with high-purity argon gas for ZnSe and oxygen gas for ZnO. X-ray diffraction (XRD) measurement was performed on these samples. The FWHM's of X-ray theta-rocking curves for the (004) peaks of ZnSe films were less than 0.5°. X-ray data show that high-quality ZnO films can be also synthesized by PLD.

  15. Ultrafast pulsed laser deposition of carbon nanostructures: Structural and optical characterization

    NASA Astrophysics Data System (ADS)

    Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Othonos, A.; Giapintzakis, J.

    2013-08-01

    Carbon nanostructured materials were obtained by high-repetition rate pulsed laser ablation of a graphite target using a train of 10-ps duration pulses at 1064 nm in different pressures of high-purity Ar gas. It is demonstrated that their microstructure and optical properties vary as a function of the argon pressure. High-resolution transmission electron microscopy revealed the existence of onion-like carbon nanostructures embedded in a matrix of amorphous carbon nanofoam for samples prepared at 300 Pa. In comparison samples prepared at 30 Pa show evidence of both onion-like and turbostratic carbon coexisting in a matrix of amorphous carbon nanofoam whereas samples prepared in vacuum are continuous films of amorphous carbon. Transient transmission spectroscopy measurements suggested that free carrier absorption is the dominant effect following photo-excitation for probing wavelengths in the range of 550-1000 nm and its magnitude varies among the materials investigated due to their different microstructures.

  16. Dynamics of a pulsed laser generated tin plasma expanding in an oxygen atmosphere

    NASA Astrophysics Data System (ADS)

    Barreca, F.; Fazio, E.; Neri, F.; Barletta, E.; Trusso, S.; Fazio, B.

    2005-10-01

    Semiconducting tin oxide can be successfully deposited by means of the laser ablation technique. In particular by ablating metallic tin in a controlled oxygen atmosphere, thin films of SnOx have been deposited. The partial oxygen pressure at which the films are deposited strongly influences both the stoichiometry and the structural properties of the films. In this work, we present a study of the expansion dynamics of the plasma generated by ablating a tin target by means of a pulsed laser using time and space resolved optical emission spectroscopy and fast photography imaging of the expanding plasma. Both Sn I and Sn II optical emission lines have been observed from the time-integrated spectroscopy. Time resolved-measurements revealed the dynamics of the expanding plasma in the ambient oxygen atmosphere. Stoichiometry of the films has been determined by means of X-ray photoelectron spectroscopy and correlated to the expansion dynamics of the plasma.

  17. Pulsed laser deposition of Mn doped CdSe quantum dots for improved solar cell performance

    SciTech Connect

    Dai, Qilin; Wang, Wenyong E-mail: jtang2@uwyo.edu; Tang, Jinke E-mail: jtang2@uwyo.edu; Sabio, Erwin M.

    2014-05-05

    In this work, we demonstrate (1) a facile method to prepare Mn doped CdSe quantum dots (QDs) on Zn{sub 2}SnO{sub 4} photoanodes by pulsed laser deposition and (2) improved device performance of quantum dot sensitized solar cells of the Mn doped QDs (CdSe:Mn) compared to the undoped QDs (CdSe). The band diagram of photoanode Zn{sub 2}SnO{sub 4} and sensitizer CdSe:Mn QD is proposed based on the incident-photon-to-electron conversion efficiency (IPCE) data. Mn-modified band structure leads to absorption at longer wavelengths than the undoped CdSe QDs, which is due to the exchange splitting of the CdSe:Mn conduction band by the Mn dopant. Three-fold increase in the IPCE efficiency has also been observed for the Mn doped samples.

  18. Vitroceramic interface deposited on titanium substrate by pulsed laser deposition method.

    PubMed

    Voicu, Georgeta; Miu, Dana; Dogaru, Ionut; Jinga, Sorin Ion; Busuioc, Cristina

    2016-08-30

    Pulsed laser deposition (PLD) method was used to obtain biovitroceramic thin film coatings on titanium substrates. The composition of the targets was selected from SiO2-CaO-P2O5-(CaF2) systems and the corresponding masses were prepared using the sol-gel method. The depositions were performed in oxygen atmosphere (100mTorr), while the substrates were heated at 400°C. The PLD deposited films were analysed through different experimental techniques: X-ray diffraction, scanning (SEM, EDX) and transmission (HRTEM, SAED) electron microscopy and infra-red spectroscopy coupled with optical microscopy. They were also biologically tested by in vitro cell culture and the contact angle was determined. The bioevaluation results indicate a high biocompatibilty of the obtained materials, demonstrating their potential use for biomedical applications. PMID:26546909

  19. Ferromagnetic semiconductor InMnAs layers grown by pulsed laser deposition on GaAs

    NASA Astrophysics Data System (ADS)

    Danilov, Yu A.; Kudrin, A. V.; Vikhrova, O. V.; Zvonkov, B. N.; Drozdov, Yu N.; Sapozhnikov, M. V.; Nicolodi, S.; Zhiteytsev, E. R.; Santos, N. M.; Carmo, M. C.; Sobolev, N. A.

    2009-02-01

    InMnAs layers were grown in a quartz reactor by YAG : Nd pulsed laser ablation of solid targets (InAs and Mn) in hydrogen and arsine flow. The crystal quality and the phase composition were analysed by x-ray diffraction. The electrical properties were derived from the Hall effect measurements. The InMnAs magneto-optical and magnetic properties were studied by means of the Kerr effect, alternating gradient field magnetometry and ferromagnetic (FM) resonance measurements. The dependence of the electrical and magnetic properties of the layers on the Mn content was investigated. The InMnAs layers exhibit FM properties at temperatures at least up to 300 K.

  20. Selective inactivation of human immunodeficiency virus with an ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Tsen, K. T.; Tsen, Shaw-Wei D.; Hung, Chien-Fu; Wu, T.-C.; Kibler, Karen; Jacobs, Bert; Kiang, Juliann G.

    2009-02-01

    Recently, femtosecond laser technology has been shown to be effective in the inactivation of non-pathogenic viruses. In this paper, we demonstrate for the first time that infectious numbers of pathogenic viruses such as Human Immunodeficiency Virus (HIV) can be reduced by irradiation with subpicosecond near infrared laser pulses at a moderate laser power density. By comparing the threshold laser power density for the inactivation of HIV with those of human red blood cells and mouse dendritic cells, we conclude that it is plausible to use the ultrashort pulsed laser to selectively inactivate blood-borne pathogens such as HIV while leaving the sensitive materials like human red blood cells unharmed. This finding has important implications in the development of a new laser technology for disinfection of viral pathogens in blood products and in the clinic.

  1. Preparation of strontium hexaferrite film by pulsed laser deposition with in situ heating and post annealing

    NASA Astrophysics Data System (ADS)

    Masoudpanah, S. M.; Seyyed Ebrahimi, S. A.; Ong, C. K.

    2012-09-01

    Strontium hexaferrite (SrFe12O19) films have been fabricated by pulsed laser deposition on Si(1 0 0) substrate with Pt(1 1 1) underlayer through in situ and post annealing heat treatments. C-axis perpendicular oriented SrFe12O19 films have been confirmed by X-ray diffraction patterns for both of the in situ heated and post annealed films. The cluster-like single domain structures are recognized by magnetic force microscopy. Higher coercivity in perpendicular direction than that for the in-plane direction shows that the films have perpendicular magnetic anisotropy. High perpendicular coercivity, around 3.8 kOe, has been achieved after post annealing at 500 °C. Higher coercivity of the post annealed SrFe12O19 films was found to be related to nanosized grain of about 50-80 nm.

  2. Magnetic properties of strontium hexaferrite films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Masoudpanah, S. M.; Seyyed Ebrahimi, S. A.; Ong, C. K.

    2012-08-01

    The magnetic properties of strontium hexaferrite (SrFe12O19) films fabricated by pulsed laser deposition on the Si(100) substrate with Pt(111) underlayer have been studied as a function of film thickness (50-700 nm). X-ray diffraction patterns confirm that the films have c-axis perpendicular orientation. The coercivities in perpendicular direction are higher than those for in-plane direction which indicates the films have perpendicular magnetic anisotropy. The coercivity was found to decrease with increasing of thickness, due to the increasing of the grain size and relaxation in lattice strain. The 200 nm thick film exhibits hexagonal shape grains of 150 nm and optimum magnetic properties of Ms=298 emu/cm3 and Hc=2540 Oe.

  3. Understanding the deposition mechanism of pulsed laser deposited B-C films using dual-targets

    SciTech Connect

    Zhang, Song; He, Zhiqiang; Wang, Chuanbin; Shen, Qiang; Zhang, Lianmeng; Ji, Xiaoli; Lu, Wenzhong

    2014-04-21

    Boron carbide thin films with stoichiometry (boron-carbon atomic ratio) range of 0.1 ∼ 8.9 were fabricated via pulsed laser deposition by using boron-carbon dual-targets. However, this experimental data on stoichiometry were smaller than the computer simulation values. The discrepancy was investigated by studies on composition and microstructure of the thin films and targets by scanning electron microscopy, excitation laser Raman spectroscopy, and X-ray photoelectron spectroscopy. The results indicate that the boron liquid droplets were formed by phase explosion after laser irradiation on boron sector. Part of the boron droplets would be lost via ejection in the direction of laser beam, which is tilted 45° to the surface of substrate.

  4. Characterization of a novel, short pulse laser-driven neutron sourcea)

    NASA Astrophysics Data System (ADS)

    Jung, D.; Falk, K.; Guler, N.; Deppert, O.; Devlin, M.; Favalli, A.; Fernandez, J. C.; Gautier, D. C.; Geissel, M.; Haight, R.; Hamilton, C. E.; Hegelich, B. M.; Johnson, R. P.; Merrill, F.; Schaumann, G.; Schoenberg, K.; Schollmeier, M.; Shimada, T.; Taddeucci, T.; Tybo, J. L.; Wender, S. A.; Wilde, C. H.; Wurden, G. A.; Roth, M.

    2013-05-01

    We present a full characterization of a short pulse laser-driven neutron source. Neutrons are produced by nuclear reactions of laser-driven ions deposited in a secondary target. The emission of neutrons is a superposition of an isotropic component into 4π and a forward directed, jet-like contribution, with energies ranging up to 80 MeV. A maximum flux of 4.4 × 109 neutrons/sr has been observed and used for fast neutron radiography. On-shot characterization of the ion driver and neutron beam has been done with a variety of different diagnostics, including particle detectors, nuclear reaction, and time-of-flight methods. The results are of great value for future optimization of this novel technique and implementation in advanced applications.

  5. Characterization of a novel, short pulse laser-driven neutron source

    SciTech Connect

    Jung, D.; Falk, K.; Guler, N.; Devlin, M.; Favalli, A.; Fernandez, J. C.; Gautier, D. C.; Haight, R.; Hamilton, C. E.; Hegelich, B. M.; Johnson, R. P.; Merrill, F.; Schoenberg, K.; Shimada, T.; Taddeucci, T.; Tybo, J. L.; Wender, S. A.; Wilde, C. H.; Wurden, G. A.; Deppert, O.; and others

    2013-05-15

    We present a full characterization of a short pulse laser-driven neutron source. Neutrons are produced by nuclear reactions of laser-driven ions deposited in a secondary target. The emission of neutrons is a superposition of an isotropic component into 4π and a forward directed, jet-like contribution, with energies ranging up to 80 MeV. A maximum flux of 4.4 × 10{sup 9} neutrons/sr has been observed and used for fast neutron radiography. On-shot characterization of the ion driver and neutron beam has been done with a variety of different diagnostics, including particle detectors, nuclear reaction, and time-of-flight methods. The results are of great value for future optimization of this novel technique and implementation in advanced applications.

  6. Dynamics of pulsed laser ablation in high-density carbon dioxide including supercritical fluid state

    NASA Astrophysics Data System (ADS)

    Urabe, Keiichiro; Kato, Toru; Stauss, Sven; Himeno, Shohei; Kato, Satoshi; Muneoka, Hitoshi; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

    2013-10-01

    To gain a better understanding of pulsed laser ablation (PLA) processes in high-density fluids, including gases, liquids, and supercritical fluids (SCFs), we have investigated the PLA dynamics in high-density carbon dioxide (CO2) using a time-resolved shadowgraph (SG) observation method. The SG images revealed that the PLA dynamics can be categorized into two domains that are separated by the gas-liquid coexistence curve and the Widom line, which forms a border between the gaslike and liquidlike domains of an SCF. Furthermore, a cavitation bubble observed in liquid CO2 near the critical point exhibited a particular characteristic: the formation of an inner bubble and an outer shell structure. The results indicate that the thermophysical properties of the reaction field generated by PLA can be dynamically tuned by controlling the solvent temperature and pressure, particularly near the critical point.

  7. Micrometric rods grown by nanosecond pulsed laser deposition of boron carbide

    NASA Astrophysics Data System (ADS)

    Lopez-Quintas, Ignacio; Oujja, Mohamed; Sanz, Mikel; Benitez-Cañete, Antonio; Chater, Richard J.; Cañamares, Maria Vega; Marco, José F.; Castillejo, Marta

    2015-02-01

    Micrometric size rods have been fabricated via pulsed laser deposition in vacuum from boron carbide targets using nanosecond pulses of 1064 and 266 nm and room temperature Si (1 0 0) substrates. Morphological, structural and chemical characterization of the microrods was made by applying scanning electron microscopy, focussed ion beam microscopy coupled to secondary ion mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Ablation at 1064 nm favours the formation of microrods with high aspect ratio, sharp edges and pyramidal tips, typically 10 μm long with a cross section of around 2 μm × 2 μm. Differently, at 266 nm the microrods are of smaller size and present a more globular aspect. The analyses of the microrods provide information about their crystalline nature and composition, based on a mixture which includes boron, boron oxide and boron carbide, and allows discussion of the wavelength dependent growth mechanisms involved.

  8. [Rigid ureteroscopy and the pulsed laser. Apropos of 325 treated calculi].

    PubMed

    Gautier, J R; Leandri, P; Rossignol, G; Quintens, H; Caissel, J

    1990-01-01

    A pulsed dye laser (Candela) was used in our lithiasis treatment center during the period 02/88-09/89 to remove 325 calculi in 278 patients, requiring 285 endoscopic instrumentations. The pulsed laser allowed to obtain fragmentation of 318 calculi, 238 of which were reduced to thin sand and 80 to coarser fragments. The latter were either cleared using a Dormia probe or further disintegrated by electrohydrolytic shock wave treatment or extracorporeal shock wave lithotripsy (ESWL). No complication imputable to laser stone fragmentation was noted. Failure of stone clearance was chiefly due to the nature and shape of the stone (black, smooth monohydrated calcium oxalate calculi). The thinness of the laser fiber has made it possible to use small caliber ureteroscopes, thereby increasing the reliability of ureteroscopy. Coupled with ESWL (EDAP LT01), this technique has caused the rate of open surgical removal of ureter confined calculi to fall from 11% to 1%. PMID:2212706

  9. Modulated pulse laser with pseudorandom coding capabilities for underwater ranging, detection, and imaging.

    PubMed

    Cochenour, Brandon; Mullen, Linda; Muth, John

    2011-11-20

    Optical detection, ranging, and imaging of targets in turbid water is complicated by absorption and scattering. It has been shown that using a pulsed laser source with a range-gated receiver or an intensity modulated source with a coherent RF receiver can improve target contrast in turbid water. A blended approach using a modulated-pulse waveform has been previously suggested as a way to further improve target contrast. However only recently has a rugged and reliable laser source been developed that is capable of synthesizing such a waveform so that the effect of the underwater environment on the propagation of a modulated pulse can be studied. In this paper, we outline the motivation for the modulated-pulse (MP) concept, and experimentally evaluate different MP waveforms: single-tone MP and pseudorandom coded MP sequences. PMID:22108874

  10. Pulsed laser deposition of air-sensitive hydride epitaxial thin films: LiH

    SciTech Connect

    Oguchi, Hiroyuki; Isobe, Shigehito; Kuwano, Hiroki; Shiraki, Susumu; Hitosugi, Taro; Orimo, Shin-ichi

    2015-09-01

    We report on the epitaxial thin film growth of an air-sensitive hydride, lithium hydride (LiH), using pulsed laser deposition (PLD). We first synthesized a dense LiH target, which is key for PLD growth of high-quality hydride films. Then, we obtained epitaxial thin films of [100]-oriented LiH on a MgO(100) substrate at 250 °C under a hydrogen pressure of 1.3 × 10{sup −2} Pa. Atomic force microscopy revealed that the film demonstrates a Stranski-Krastanov growth mode and that the film with a thickness of ∼10 nm has a good surface flatness, with root-mean-square roughness R{sub RMS} of ∼0.4 nm.

  11. Pulsed-laser micropatterned quantum-dot array for white light source

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Wen; Lin, Huang-Yu; Lin, Chien-Chung; Kao, Tsung Sheng; Chen, Kuo-Ju; Han, Hau-Vei; Li, Jie-Ru; Lee, Po-Tsung; Chen, Huang-Ming; Hong, Ming-Hui; Kuo, Hao-Chung

    2016-03-01

    In this study, a novel photoluminescent quantum dots device with laser-processed microscale patterns has been demonstrated to be used as a white light emitting source. The pulsed laser ablation technique was employed to directly fabricate microscale square holes with nano-ripple structures onto the sapphire substrate of a flip-chip blue light-emitting diode, confining sprayed quantum dots into well-defined areas and eliminating the coffee ring effect. The electroluminescence characterizations showed that the white light emission from the developed photoluminescent quantum-dot light-emitting diode exhibits stable emission at different driving currents. With a flexibility of controlling the quantum dots proportions in the patterned square holes, our developed white-light emitting source not only can be employed in the display applications with color triangle enlarged by 47% compared with the NTSC standard, but also provide the great potential in future lighting industry with the correlated color temperature continuously changed in a wide range.

  12. Pulsed laser deposition of high-quality thin films of the insulating ferromagnet EuS

    SciTech Connect

    Yang, Qi I.; Zhao, Jinfeng; Risbud, Subhash H.; Zhang, Li; Dolev, Merav; Fried, Alexander D.; Marshall, Ann F.; Kapitulnik, Aharon

    2014-02-24

    High-quality thin films of the ferromagnetic insulator europium(II) sulfide (EuS) were fabricated by pulsed laser deposition on Al{sub 2}O{sub 3} (0001) and Si (100) substrates. A single orientation was obtained with the [100] planes parallel to the substrates, with atomic-scale smoothness indicates a near-ideal surface topography. The films exhibit uniform ferromagnetism below 15.9 K, with a substantial component of the magnetization perpendicular to the plane of the films. Optimization of the growth condition also yielded truly insulating films with immeasurably large resistance. This combination of magnetic and electric properties opens the gate for future devices that require a true ferromagnetic insulator.

  13. Osteoblast behavior on various ultra short pulsed laser deposited surface coatings.

    PubMed

    Qu, Chengjuan; Myllymaa, Sami; Prittinen, Juha; Koistinen, Arto P; Lappalainen, Reijo; Lammi, Mikko J

    2013-04-01

    Ultra short pulsed laser deposition technique was utilized to create amorphous diamond, alumina and carbon nitride, and two different titania coatings on silicon wafers, thus producing five different surface deposited films with variable physico-chemical properties. The surface characterizations, including the roughness, the contact angle and the zeta potential measurements were performed before we tested the growth properties of human osteoblast-like Saos-2 cells on these surfaces (three separate experiments). The average roughness and hydrophobicity were the highest on titania-deposited surfaces, while carbon nitride was the most hydrophilic one. Osteoblasts on all surfaces showed a flattened, spread-out morphology, although on amorphous diamond the cell shape appeared more elongated than on the other surfaces. On rough titania, the area covered by the osteoblasts was smaller than on the other ones. Cell proliferation assay did not show any statistically significant differences. PMID:23827623

  14. Chromium carbide thin films deposited by ultra-short pulse laser deposition

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    Pulsed laser deposition performed by a laser with a pulse duration of 250 fs has been used to deposit films from a Cr 3C 2 target. Due to the different processes involved in the laser ablation when it is performed by an ultra-short pulse source instead of a conventional short pulse one, it has been possible to obtain in vacuum films containing only one type of carbide, Cr 3C 2, as shown by X-ray photoelectron spectroscopy. On the other hand, Cr 3C 2 is not the only component of the films, since a large amount of amorphous carbon is also present. The films, deposited at room temperature, are amorphous and seem to be formed by the coalescence of a large number of particles with nanometric size. The film composition can be explained in terms of thermal evaporation from particles ejected from the target.

  15. Mechanical and electrical properties of epitaxial Si nanowires grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Obi, D.; Nechache, R.; Harnagea, C.; Rosei, F.

    2012-11-01

    We report on the elastic and piezoresistive properties of individual epitaxial Si-NWs grown on n-doped Si(111) by pulsed laser deposition. Using scanning probe microscopy, we obtained a Young’s modulus between 82 and 900 GPa for the nanowires, unaffected by the nanowire shape. A relative resistivity change is observed in the prestrained (curved) Si-NWs, which we attribute to a large piezoresistance coefficient in the NW along its axis. Assuming that for the bent NWs the effect of longitudinal stress on resistivity is compensated, the piezoresistance coefficient originating in the shear strain alone, we found a piezoresistance gauge factor (GF) of 600, which is close to the values reported in literature for Si-NWs.

  16. Focal spot measurement in ultra-intense ultra-short pulse laser facility

    NASA Astrophysics Data System (ADS)

    Liu, Lanqin; Peng, Hansheng; Zhou, Kainan; Wang, Xiaodong; Wang, Xiao; Zeng, Xiaoming; Zhu, Qihua; Huang, Xiaojun; Wei, Xiaofeng; Ren, Huan

    2005-06-01

    A peak power of 286-TW Ti:sapphire laser facility referred to as SILEX-I was successfully built at China Academy of Engineering Physics, for a pulse duration of 30 fs in a three-stage Ti:sapphire amplifier chain based on chirped-pulse amplification. The beam have a wavefront distortion of 0.63μm PV and 0.09μm RMS, and the focal spot with an f/2.2 OAP is 5.7μm, to our knowledge, this is the best far field obtained for high-power ultra-short pulse laser systems with no deformable mirror wavefront correction. The peak focused intensity of ~1021W /cm2 were expected.

  17. Synthesis and characterization of Sb-doped ZnO microspheres by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Nagasaki, Fumiaki; Shimogaki, Tetsuya; Tanaka, Toshinobu; Ikebuchi, Tatsuya; Ueyama, Takeshi; Fujiwara, Yuki; Higashihata, Mitsuhiro; Nakamura, Daisuke; Okada, Tatsuo

    2016-08-01

    We succeeded in synthesizing antimony (Sb)-doped zinc oxide (ZnO) microspheres by ablating a sintered ZnO target containing Sb in air. The structural properties of the microspheres were investigated by Raman scattering studies. The Zn–Sb related local vibrational mode (LVM) was detected around 238 cm‑1. Room-temperature photoluminescence (PL) properties of the microspheres were investigated under cw and pulsed laser excitations, and ultraviolet (UV) emission and whispering-gallery-mode (WGM) lasing were observed from the microspheres. Furthermore, a p–n heterojunction was formed between a single Sb-doped ZnO microsphere and an n-Al-doped ZnO thin film, and a good rectifying property with a turn-on voltage of approximately 1.8 V was observed in the current–voltage (I–V) characteristics across the junction.

  18. Pulsed laser deposition of silicon substituted hydroxyapatite coatings from synthetical and biological sources

    NASA Astrophysics Data System (ADS)

    Solla, E. L.; González, P.; Serra, J.; Chiussi, S.; León, B.; López, J. García

    2007-12-01

    Silicon substituted hydroxyapatite (Si-HA) is a new material with an enhanced bioactibity and it can be produced by chemical synthesis. Nevertheless, the coating of metallic substrates with a bioactive material is a common method nowadays to improve its integration with the receptor bone. Si-HA films were deposited by pulsed laser deposition (PLD), using targets composed of mixtures of HA with different Si containing sources such as SiO 2 and diatomaceous earth. The Si-HA films were characterized in terms of structure and chemical composition by spectroscopic techniques (FTIR, XPS), and several ion beam techniques (RBS, PIXE). The analysis revealed that the Si is successfully incorporated into the HA structure, as well as traces of other elements such as Na, Fe or K.

  19. Nanoforest Nb2O5 Photoanodes for Dye-Sensitized Solar Cells by Pulsed Laser Deposition

    SciTech Connect

    Ghosh, Rudresh; Brennaman, Kyle M.; Uher, Tim; Ok, Myoung-Ryul; Samulski, Edward T.; McNeil, L. E.; Meyer, Thomas J.; Lopez, Rene

    2011-10-26

    Vertically aligned bundles of Nb₂O₅ nanocrystals were fabricated by pulsed laser deposition (PLD) and tested as a photoanode material in dye-sensitized solar cells (DSSC). They were characterized using scanning and transmission electron microscopies, optical absorption spectroscopy (UV–vis), and incident-photon-to-current efficiency (IPCE) experiments. The background gas composition and the thickness of the films were varied to determine the influence of those parameters in the photoanode behavior. An optimal background pressure of oxygen during deposition was found to produce a photoanode structure that both achieves high dye loading and enhanced photoelectrochemical performance. For optimal structures, IPCE values up to 40% and APCE values around 90% were obtained with the N₃ dye and I₃{sup –}/I{sup –} couple in acetonitrile with open circuit voltage of 0.71 V and 2.41% power conversion efficiency.

  20. The thermoelastic basis of short pulsed laser ablation of biological tissue.

    PubMed Central

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

    1995-01-01

    Strong evidence that short-pulse laser ablation of biological tissues is a photomechanical process is presented. A full three-dimensional, time-dependent solution to the thermoelastic wave equation is compared to the results of experiments using an interferometric surface monitor to measure thermoelastic expansion. Agreement is excellent for calibrations performed on glass and on acrylic at low laser fluences. For cortical bone, the measurements agree well with the theoretical predictions once optical scattering is included. The theory predicts the presence of the tensile stresses necessary to rupture the tissue during photomechanical ablation. The technique is also used to monitor the ablation event both before and after material is ejected. PMID:7892208