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The laser cavity dynamics in the active mode-locking model is characterized as a function of the gain pumping [g.sub.0] and the ratio of the period of the acoustooptic modulation to the cavity length. The studies have shown that enhanced performance is achieved with a high degree of localization in the modulator and for a modulation period commensurate with the round-trip cavity time.

A new approach for the electromagnetic control and propulsion of a current carrying electric arc plasma ring is described. The essence of the approach is to form and manipulate the arc plasma outside rather than inside an electromagnetic field (B-field) producing coil so that pulsed plasma thrusts can be produced in a choice of different directions. The interaction of the electric arc, formed in atmospheric pressure air, with such B-field has been investigated. It has been shown that a stable azimuthal plasma ring can rapidly be produced by the simple process of separating two annular contacts. Pulsed plasma propulsion is obtained when the arc plasma, and B-field sustaining current is automatically reduced to zero, whereby the constraining electromagnetic forces are removed and, as a consequence, the resulting plasma ring radially expands outwards. Several different measurement techniques have been deployed for investigating the behavior of the plasma ring. These include electrical probing, B-field probing, and high-speed plus video photography. Experimental results are shown to be in good agreement with theoretical estimates based upon a Sedov's self-similar model. Index Terms--Ablation, arc discharges, magnetic fields, plasma arc devices, plasma control.

This paper investigates the ablation of wires in two-wire tungsten X-pinches driven by an 80-kA current over 50 ns. High-resolution imaging using a Nomarski interferometer allows measurements close to the X-pinch cross point, where the ablation 'flare' structure is observed to dearly develop during the drive-current rise time. Electron density profiles are recovered as a function of both distance normal to the wire and of time. Results compare favorably to the rocket model of wire ablation. In addition, the density contrast over the ablation 'stream' and 'gap' structure is measured and compared to similar measurements made using quantitative radiography on the 1-MA 250-ns MAGPIE generator at Imperial College London, London, U.K. Index Terms--Precursor plasma, wire ablation, X-pinch.

Cyclopentadienyl dialuminum with a half sandwich structure is prepared in a pulsed laser ablation cluster beam source and identified with a time of flight photoionization mass spectrometer. The high resolution electron spectrum of this complex is obtained using pulsed field ionization zero electron kinetic energy photoelectron spectroscopy.

Several techniques are developed to improve the pinning in YBCO based quasi-multilayers prepared by the on- and off-axis pulsed laser deposition (PLD) technique. The off-axis deposited multilayers are found to exhibit very high values of the critical current density.

A new transition edge sensor with the titanium superconductor fabricated for single photon measurements which showed a fast response to pulsed laser illumination of 1.5 [mu]m wavelength with the fall time constant of 300 ns is reported.

The effects of liquid thickness on laser ablation efficiency are investigated. Ablation performance for Q-switched Nd:YAG (yttrium aluminum garnet) and free-running Er: YAG lasers were quantitatively measured by optical coherence tomography.

In this paper, we report analysis of various basaltic lunar samples including 14053 and 14072, KREEP basalt 15386, thirty basalt clasts from Apollo 14 breccia 14321, as well as impact-generated samples (matrix from breccia 14168, olivine vitrophyres 14321,1180 and 14321,1539, and impact melt 14310) using a combination of solution and laser ablation inductively coupled plasma mass spectrometry (ICP-MS). The basalt clast samples were previously analyzed by instrumental neutron activation. On plots of incompatible trace elements (ITEs) vs. compatible trace elements, the Apollo 14 high-Al basalts form three approximately subparallel trends that, on the basis of current data, are also separated by age. Plots of ITE ratios (i.e., Nb/Ce vs. Zr/Y) can be used to indicate source composition, and also divide the basalts into three groups: Group A (~4.3 Ga); Group B (~4.1 Ga); and Group C (~3.9 Ga). New data for 14072 suggest the sample does not fit with any of the three groups defined here, and may indicate the presence of a fourth group of high-Al basalts in the proximity of the Apollo 14 site. The Apollo 14 high-Al basalts are compositionally distinct from known Apollo 14 impact melts and impact-generated lithologies. The three groups cannot be related by varying degrees of partial melting of a single, KREEP-contaminated source and, therefore, require three separate source regions. The new data indicate that Group A basalts evolved through closed-system crystal fractionation. However, the new data from basalts forming Groups B and C require open-system evolution that involves combined assimilation and fractional crystallization (AFC). Unlike previous AFC modeling of the Apollo 14 high-Al basalts, an assimilant composed of KREEP is not sufficient to generate the compositional ranges of each basalt group. The modeling of both groups requires a mixture of KREEP and granite as the assimilant, which supports the notion of a genetic relationship between these two lunar components. Keywords: Moon, assimilation, basalt petrogenesis, Apollo 14 high-Al basalts, mare basalts, fractional crystallization, KREEP, granite

The laser-induced ablation of bovine bone is investigated assisted by a transparent liquid layer on top of the target surface. It is concluded that although the liquid layer on the target surface accompanies a limitation of plasma shielding, it facilitates the augmentation of bone ablation efficiency.

Experiments were conducted and a mathematical model was developed to investigate the heat transfer, fluid flow, and keyhole dynamics during a pulsed keyhole laser welding. The proposed model goes well with the experimental results and lays foundation for further study in keyhole laser welding.

Single femtosecond laser pulses at near infrared (IR) wavelength are focused on silicon wafers by high numerical aperture objective lens in order to fabricate ablated craters close to the diffraction limit in lateral feature size. The decrease of the ablation efficiency in the high influence regime is attributed to the strong interaction of the laser pulse with the laser-influenced plasma.

A laser irradiation technique has been explored to quantify visible as well as invisible degradation of housing materials used for nonceramic insulators. Nonceramic insulators that were removed from service and new samples of the housing that were subjected to accelerated testing in the laboratory have been evaluated. The method uses a constant power laser source for delivering the same energy to the test specimen. The proposed method is fairly quick and could be looked upon as an additional method for characterizing aging of nonceramic insulators, it has been shown that this method provides a better characterization of aging than is obtained from Fourier Transform Infrared Spectroscopy. The housing materials evaluated include silicone rubber, ethylene propylene diene monomer rubber and cycloaliphatic epoxy resin. Index Terms--Degradation, laser, ablation, depth of penetration, corona.

Computer simulation is performed in a whole breaking period except the region of current zero of gas circuit breaker. The Euler equation is solved using the finite volume fluid in cell method. In order to consider the effects of arc, electric field intensity and radiation transport are calculated using the finite element method and the method of partial characteristics, respectively. Also, the quantity and the electrical conductivity of ablated nozzle vapor are calculated, and its effects are investigated through computer simulation. Improved simulation results are obtained and compared with the experimental one. Index Terms--Ablation, arc discharges, gas circuit breakers (GCB), S[F.sub.6].

An experimental setup to study the pH dependence of standard ion-transfer potentials at the water/NPOE interface is presented. The system is composed of a micro-hole generated by laser photoablation in a 12-[micro]m polyethylene terephthalate film, the aqueous phase consisting of a commercial immobilized pH gradient gel reswelled in electrolyte solution and a droplet of organic solution. Two electrodes are used, an Ag/AgCl aqueous electrode and an Ag/AgTPBCI organic electrode. This setup is applied to the study of two ionizable compounds (pyridine, 2,4-dinitrophenol). Thermodynamic parameters such as the standard transfer potential, the Gibbs energy of transfer, and the partition coefficients of the ionized forms as well as the neutral forms of these drug compounds are evaluated by differential pulse voltammetry. The data obtained are summarized in ionic partition diagrams, which are a useful tool for predicting and interpreting the transfer behavior of ionized drugs at the liquid/liquid interfaces mimicking the biological membranes.

We report a study of the basic characteristics of laser polishing of fused silica with a protocol that is particularly suitable for surface smoothing of micro-optic elements fabricated by a laser ablation process. We describe a new, to our knowledge, approach based on scanning a highly controlled small size laser beam and melting areas of tens to hundreds of micrometers of glass using a computer-controlled raster scan process, which does not require beam shaping, substrate preheating, or special atmospheres. Special test samples of silica substrates with prescribed spatial frequency content were polished using a range of irradiation conditions with the beam from a well-controlled C[O.sub.2] laser operating at a wavelength of 10.59 [micro]m. An analysis is presented of the laser-generated reduction in surface roughness in terms of measurements of the spatial frequency characteristics, and the results are compared with the predictions of a simple model of surface-tension-driven mass flow within the laser-melted layer. This technique is shown to be capable of smoothing silica surfaces with ~1 [micro]m scale roughness down to levels < 1 nm with no net effect on the as-machined net surface shape, at realistic production rates without a preheating stage, and with noncritical residual stresses. OCIS codes: 000.2190, 220.4000, 220.5450, 120.4610, 120.5820, 350.3390.

Laser-beam-intensity fluctuations between an uplink (ground to satellite) and a downlink (satellite to ground) are described. The dependence of the beam radius on log-intensity variance in the uplink and the dependence of receiving-aperture diameter on the log-intensity variance in the downlink using a known theory were calculated. Statistical analysis of the experimental data on the laser links was performed, and high correlation coefficients of 0.94 between the normalized intensity variances of the uplink and those of the stellar scintillation were obtained. The beam-pointing error in the satelliteborne laser transmitter chiefly caused fluctuations in the downlink. 2005 Optical Society of America OCIS codes: 010.1300, 010.3310, 010.7060

Abstract: This work reports on our earnest effort to development a Pulsed Laser Ablation Deposition system for the production of carbon nanotubes (CNTs). The correct condition such as the pressure, [...]

Laser ablation--inductively coupled plasma--mass spectrometry (LA-ICP-MS) has become recognized as a sensitive, efficient, and cost-effective approach to measuring the major-, minor-, and trace-solute compositions of individual fluid inclusions in minerals. As a prerequisite for the routine analysis of natural inclusions in our laboratory, the precision and accuracy of the technique was assessed using sets of multi-element synthetic fluid inclusions. Five multi-element standard solutions were prepared, and incorporated as fluid inclusions in quartz crystals at 750 [degrees]C and 7 kbar. Fluid inclusions were ablated with a 193 nm ArF excimer laser and analyzed with a quadmpole ICP-MS, equipped with an octopole reaction cell for the removal of Ar-based interferences. The internal standard used in all cases was Na. Analytical precision for K, Rb, and Cs is typically better than 15% RSD, whereas Li, Mg, Ca, Sr, Ba, Mn, Fe, Cu, Zn, and Cl analyses are typically reproducible within 30% RSD. Measured concentrations approximate a Gaussian distribution, suggesting that analytical errors are random. Analyses for most elements are accurate within 15%. Limits of detection vary widely according to inclusion volume, but are 1 to 100 [micro]g/g for most elements. These figures of merit are in excellent agreement with previous studies. We also demonstrate that, over the range investigated, precision and accuracy are insensitive to inclusion size and depth. Finally, the combination of our LA-ICP-MS analyses with microthermometric data shows that charge-balancing to NaCl-[H.sub.2]O equivalent chloride molality is the most valid approach to LA-ICP-MS data reduction, where chloride-dominated fluid inclusions are concerned.

The photoluminescence (PL) behavior of pulsed laser deposition (PLD)-deposited Si-based nanoporous SiO(sub x)/Si, SiN(sub x), and SiO(sub x) thin films, having completely different chemistries and microstructures is investigated. The results demonstrate that the red PL peak at 1.5 eV is due to the localized states at the oxidized surfaces of these materials, while the green PL peak at 2.3 eV is due to oxygen-related defects in their local disordered nanostructures.

An investigation on the femtosecond laser ablation of Ti, Zr, and Hf is conducted by mean of in situ plasma diagnostics. The investigation shows that two plume components with different expansion velocities are generated by the interaction of ultrashort laser pulses with metals.

A study on a one-dimensional gas-dynamic model is presented for the laser ablation of Cu and the expansion of the Cu vapor in a background gas (He) at 1atm. The numerical results obtained from the study show that the consideration of ionization and laser absorption in the plume greatly influences the gas dynamics.

High-quality epitaxial thin films of EuTiO(sub 3) are grown on the (001) surface of SrTiO(sub 3) using pulsed laser deposition. The EuTiO(sub 3) thin films grow two dimensionally, epitaxially, and pseudomorphically, with no measurable in-plane lattice mismatch.

The optical properties of the laser-machined channel are affected by the residual ablated material remaining in the atmosphere of the channel during femtosecond-laser deep hole drilling. The interplay between hole drilling, beam propagation, and non-liner beam interactions are demonstrated.

A new plasma model to explain skin tissue ablation with nanosecond laser pulses from ultraviolet to near-infrared is presented. It is useful to understand the laser-tissue interaction and advancing surgical applications of lasers.

Melting and ablation of aluminum, chromiun, and nickel films by nanosecond laser pulses with fluences of 24-13 J/cm(super 2) were tracked by high-speed transmission electron microscopy and selected area (20 um[super Phi]) diffraction. At sufficiently high laser fluences, a plasma is produced with an ionization degree >20%, varying on the micrometer scale, as revealed by dark-field imaging.

We describe a simple and passive nanosecond-long laser-pulse stretcher using multiple optical ring cavities. We present a model of the pulse-stretching process for an arbitrary number of optical ring cavities. This new model explicitly includes the effects of cavity delay time, beam-splitter reflectivity, total number of optical cavities, and describes the effects of spatial profile sensitivity. Using the model, we optimize the design of a pulse stretcher for use in a spontaneous Raman-scattering excitation system that avoids laser-induced plasma spark problems. From the optimized design, we then experimentally demonstrate and verify the model with a three-cavity pulse-stretcher system that converts a 1000-mJ, 8.4-ns-long input laser pulse into an approximately 75-ns-long (FWHM) output laser pulse with a peak power reduction of 0.10x and an 83% efficiency. OCIS codes: 140.0140, 140.3550, 220.4830, 320.4240, 320.5540.

Studies of the interaction between a pulsed C[O.sub.2] laser and micrometer-sized aqueous and organic particles by use of light-scattering methods and step-scan Fourier-transform infrared (FTIR) spectroscopy are reported. Visible two-color extinction experiments indicate primary particle shattering, accompanied by a high fraction of vaporization, followed by secondary particle evaporation. The extent of the latter depends on the pulse intensity and particle composition. Angle-resolved light-scattering investigations provide insight into the aerosol size distribution and temperature following the pulsed heating event. The time dependence of the vapor plume, monitored with step-scan FTIR spectroscopy, confirms that a large fraction of the initial particle is quickly evaporated during the shattering event, followed by secondary fragment evaporation and thermal expansion.

PC-based arc modeling taking account of the effects of nozzle ablation and the mixing process of PTFE vapor with S[F.sub.6] has been carried out for a full-scale auto-expansion circuit breaker with a moving contact. An equation to calculate the PTFE concentration in the mixture is introduced together with overall mass, momentum, and energy conservation equations for the mixture. The thermodynamic and transport properties of S[F.sub.6]-PTFE vapor mixture calculated by the transport theory are given. An empirical relationship between radiation reabsorption factor and the relevant arcing parameters (nozzle size and instantaneous arcing current) has been employed to make predictions. The features of temperature, pressure, PTFE mass concentration, and flow fields during the whole arcing period are discussed. It is shown that the energy brought into the expansion volume by the hot PTFE vapor is mainly responsible for the pressure buildup. The propagation of the pressure wave in the expansion volume is responsible for the pressure peaks in the second loop of arcing. The predicted arc voltage and pressure variation are compared with the test results and with those predicted using the thermodynamic and transport properties of pure S[F.sub.6]. Results show that the use of the properties of S[F.sub.6]-PTFE vapor mixture substantially improves the agreement between the predicted and measured pressure rise in the expansion volume. Index Terms--Arc behavior, auto-expansion circuit breakers, computational investigation, nozzle ablation, transport coefficients.

Next to laser ablation (LA) also electrothermal vaporization (ETV) from a graphite furnace as a means of sample introduction opens possibilities for direct analysis of solid samples using inductively coupled plasma mass spectrometry (ICPMS). In this paper, it is demonstrated that solid sampling ETV-ICPMS is very well suited for the determination of metal traces in polyethylene. A limited multielement capability is often cited as an important drawback of ETV-ICPMS. However, by studying the effect of monitoring an increasing number of mass-to-charge ratios on the signal profile (integrated signal intensity and repeatability) of selected analyte elements, the multielement capability of (solid sampling) ETV-ICPMS was systematically evaluated, and the results obtained suggest that, with a quadrupole-based ICPMS instrument, at least 11 elements can be determined 'simultaneously' (from the same vaporization step), in essence without compromising the sensitivity or the precision of the results obtained. In this work, the 'simultaneous' determination of Al, Ba, Cd, Cu, Mn, Pb, and Ti in a polyethylene candidate reference material has been accomplished, despite the large variation in analyte concentration (from 5 ng/g for Mn to 500 (mu)/g for Ti) and in furnace behavior (volatility) they exhibit. To avoid premature losses of Cd during thermal pretreatment of the samples, Pd was used as a chemical modifier. Two different calibration methods - external calibration using an aqueous standard solution and single standard addition - were studied and the results obtained were compared with those obtained using neutron activation analysis (NAA) and/or with the corresponding (candidate) certified values (if available). Single standard addition was shown to be preferable (average deviation between ICPMS result and reference value < 3%), although - except for Ba - acceptable results could also be obtained with external calibration.

Research demonstrates that alloying additions to refractory metals improves the latter for their use at high temperatures. Data indicate that silicon and aluminum provide oxidation resistance either in the solid solution form or in their second phase configuration. The creep resistance depends on the morphology of the second phase.

The two-dimensional spatial distribution of the composition of the deposit was experimentally studied and analyzed by using the sorption approach. Results show a good agreement between the experimental and sorption analysis, and suggest a determining role of the plume-substrate interaction in the deposition process.

The surface treatment of sapphire is employed by using reactive ion beam (RIB) pretreatment as an alternative process for GaN growth in metal organic chemical vapor deposition (MOCVD) is investigated. Results show that due to RIB treatment, the etching of the sapphire surface and the formation of a very thin, disorders A1ON layer is observed which was partially crystallized during the main growth of GaN.

Monitoring the energy of ions ejected during pulsed excimer laser ablation of solid and molten silicon and germanium compounds was done through the use of a simple time-of-flight spectrometer. This detection system was equipped with a Faraday cup ion current detector and an electrostatic grid. Results revealed that time-of-flight spectrometer is effective in observing ion current and ion energy distributions during pulsed laser deposition even under varying barrier voltage.

A study is made of the conditions under which micrometeorites can enter the Earth's atmosphere without being melted or without having their nuclear tracks annealed. The two mechanisms studied are: (1) aerocapture followed by entry from a bound orbit; and (2) direct entry at large zenith angles. Mechanism (2) is generally more efficient if the maximum temperature is limited to 1600 K; some grains as large as 400 [[micro]meter] across can survive unmelted. Both mechanisms are competitive for maximum temperatures of 800 K. The estimated probabilities of entry (compared with the total flux to the Earth) are a few times [10.sup.-3] for unannealed particles and several percent for unmelted ones.

Short electrical discharges with high energy are a very promising tool for controlled ablation and deposition of materials. A source for pulsed discharges is the channel spark discharge. This channeled discharge can produce electron pulses of about 15 keV and 1 kA. Introducing the pulse energy in the target over a small area and a small penetration depth within a short time (100 ns), a very high energy density is produced in the surface region leading to very high instantaneous ablation rates. The energetic pulse parameters are comparable to the laser light pulses in PLD. Ablated material produced by the discharge is distinguished by its high degree of ionization and excitation. The development of the plasma has been characterized by the emitted optical radiation, spectrally resolved. Lines of ablated material and working gas (nitrogen) are observable in the emission spectrum. For reactive deposition of BN-films, for instance, the energy deposited in discharge gas may be used directly for the deposition process. Therefore, the channel spark discharge represents an effective and inexpensive source for highly excited and reactive deposition. Index Terms - Channel spark, electron beam, evaporation, high-speed observation, optical spectroscopy, plasma production, thin-film deposition.

The hydrodynamic response of thin plane targets to the action of the high-power proton beam of the Karlsruhe Light Ion Facility KALIF has been investigated using time-resolved one.dimensional (1-D) and two-dimensional (2-D) laser Doppler velocimetry with subnanosecond temporal resolution. A new method for shock compressibility (Hugoniot) measurements with micrometer-thick impactors and transparent barriers has been used. Experimental velocity histories have been compared to numerical simulations accounting for thermal conductivity, equation of state, and stopping power of dense strongly coupled plasma. Index Terms - Ablation plasma, computer simulation, equation of state, high-power ion beams, shockwaves.

A photothermal model to analyze the suitability of multilayer structures for he etch-stop process in the laser ablation of polyimide films reveals that optically thin foils are suitable for etch-stop in the laser ablation process. The penetration depth of middle layer has to be three-folds higher than that of surrounding layers for etch-stop. Selective use of impurities helps induce differences in the optical properties of the layers for their easy differentiation.

Triple-frame high-speed transmission electron microscopy facilitates imaging of ablation of free standing metal films by picosecond laser pulses. Capillary forces, recoiling evaporating atoms and continuous evaporation help determine the ablation mechanisms initiated by picosecond laser pulses of fluences ranging from 0.6 to 8 J per squared cm in Au and Al films. Enhanced laser fluence increases ablation, which continues by hole opening between 5 and 30 nanoseconds.

Analysis of epitaxially-crystallized BST films deposited on YBCO/MgO and Pt/MgO substrates by laser ablation reveals their electrical properties and chemical composition. BST thin films on YBCO/MgO exhibit greater leakage current density than those on Pt/MgO. BST thin films on YBCO/MgO substrates exhibit a dissipation factor of 0.02 and dielectric constant of 430 at 10 kHz. BST thin films on Pt/MgO substrates exhibit a stoichiometric composition and epitaxial development at 600 degrees C.

Laser ablation of LiCoO2 on heated substrates in oxygen causes in situ deposition and growth of the rock-salt phase between 22 and 250 degrees C, spinel or low temperature phase between 300 and 450 degrees C and standard hexagonal or high-temperature phase between 500 and 680 degrees C. In situ growth between 500 and 550 degrees C resulted in a mixed-phase layered and spinel LiCoO2. The lattice constant of the rock-salt phase depends on lithium concentration. Extended cation ordering and large grain sizes develop at constant oxygen pressure and high temperatures, while the HT-LiCoO2 phase occurs at low oxygen pressures.

ArF excimer laser-induced ablation helps deposit silicon oxynitride, oxide and nitride films at temperatures of less than 450 degrees Celsius from silicon nitride, fused silica, silica monoxide and fused silica targets in an oxygen atmosphere. The processes that initiate Si-based dielectric layer synthesis are related to the interaction of oxygen molecules with ionized and neutral laser emission products. All the silicon layers except silicon nitride exhibit stoichiometric properties.

Studies of plume generated from 193 nm irradiation of GeO2 targets by recording dispersed emission in the UV to visible regions reveal the presence of neutral and singly ionized atomic species in the plume and the emission intensities of the species vary according to O2 pressure and distance from the front surface of the target. The behavior of the emission intensities are linked to the concentration of excited oxygen atoms, produced from plume-O2 interactions at higher ambient gas pressures. The change in plume's concentration of excited species by ambient O2 affects film growth.

Quartz-crystal microbalance monitors the ablation in CuCl samples and derives the plot of single-pulse mass removal versus incident fluence. An Arrhenius-like exponential function is concordant with the ablation data. Curve shape and other data show the predominance of thermal process in the excimer laser ablation of CuCl.

One dimensional-imaging laser-induced fluorescence spectroscopy facilitated the study of propagation phase and diffusion phase of YO molecules in the ground state, when subjected to ArF excimer laser ablation in an ambient oxygen gas. The YO molecules belong to the compound YBa2Cu3O(7 - delta). Ambient pressure increase lowered the ablation fluence which shortened the propagation distance. A 1000 kelvin rotational temperature was observed in the diffusion phase.

PbZr0.52Ti0.48O3 (PZT), La0.5Sr0.5CoO3 (LSC) and MgO reveal ablated flux characteristics which depend on oxygen or noble gas pressure, laser energy and the ablation time. The deposition rates of PZT and LSC which influence ablated flux characteristics are represented as a function of oxygen pressure and laser energy.