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Sample records for alkali vapor lasers

  1. Alkali-vapor lasers

    NASA Astrophysics Data System (ADS)

    Zweiback, J.; Komashko, A.; Krupke, W. F.

    2010-02-01

    We report on the results from several of our alkali laser systems. We show highly efficient performance from an alexandrite-pumped rubidium laser. Using a laser diode stack as a pump source, we demonstrate up to 145 W of average power from a CW system. We present a design for a transversely pumped demonstration system that will show all of the required laser physics for a high power system.

  2. Diode pumped alkali vapor fiber laser

    DOEpatents

    Payne, Stephen A.; Beach, Raymond J.; Dawson, Jay W.; Krupke, William F.

    2007-10-23

    A method and apparatus is provided for producing near-diffraction-limited laser light, or amplifying near-diffraction-limited light, in diode pumped alkali vapor photonic-band-gap fiber lasers or amplifiers. Laser light is both substantially generated and propagated in an alkali gas instead of a solid, allowing the nonlinear and damage limitations of conventional solid core fibers to be circumvented. Alkali vapor is introduced into the center hole of a photonic-band-gap fiber, which can then be pumped with light from a pump laser and operated as an oscillator with a seed beam, or can be configured as an amplifier.

  3. Diode pumped alkali vapor fiber laser

    DOEpatents

    Payne, Stephen A.; Beach, Raymond J.; Dawson, Jay W.; Krupke, William F.

    2006-07-26

    A method and apparatus is provided for producing near-diffraction-limited laser light, or amplifying near-diffraction-limited light, in diode pumped alkali vapor photonic-band-gap fiber lasers or amplifiers. Laser light is both substantially generated and propagated in an alkali gas instead of a solid, allowing the nonlinear and damage limitations of conventional solid core fibers to be circumvented. Alkali vapor is introduced into the center hole of a photonic-band-gap fiber, which can then be pumped with light from a pump laser and operated as an oscillator with a seed beam, or can be configured as an amplifier.

  4. Alkali metal vapors - Laser spectroscopy and applications

    NASA Technical Reports Server (NTRS)

    Stwalley, W. C.; Koch, M. E.

    1980-01-01

    The paper examines the rapidly expanding use of lasers for spectroscopic studies of alkali metal vapors. Since the alkali metals (lithium, sodium, potassium, rubidium and cesium) are theoretically simple ('visible hydrogen'), readily ionized, and strongly interacting with laser light, they represent ideal systems for quantitative understanding of microscopic interconversion mechanisms between photon (e.g., solar or laser), chemical, electrical and thermal energy. The possible implications of such understanding for a wide variety of practical applications (sodium lamps, thermionic converters, magnetohydrodynamic devices, new lasers, 'lithium waterfall' inertial confinement fusion reactors, etc.) are also discussed.

  5. High power diode pumped alkali vapor lasers

    NASA Astrophysics Data System (ADS)

    Zweiback, J.; Krupke, B.

    2008-05-01

    Diode pumped alkali lasers have developed rapidly since their first demonstration. These lasers offer a path to convert highly efficient, but relatively low brightness, laser diodes into a single high power, high brightness beam. General Atomics has been engaged in the development of DPALs with scalable architectures. We have examined different species and pump characteristics. We show that high absorption can be achieved even when the pump source bandwidth is several times the absorption bandwidth. In addition, we present experimental results for both potassium and rubidium systems pumped with a 0.2 nm bandwidth alexandrite laser. These data show slope efficiencies of 67% and 72% respectively.

  6. Diode pumped alkali vapor lasers for high power applications

    NASA Astrophysics Data System (ADS)

    Zweiback, J.; Krupke, B.; Komashko, A.

    2008-02-01

    General Atomics has been engaged in the development of diode pumped alkali vapor lasers. We have been examining the design space looking for designs that are both efficient and easily scalable to high powers. Computationally, we have looked at the effect of pump bandwidth on laser performance. We have also looked at different lasing species. We have used an alexandrite laser to study the relative merits of different designs. We report on the results of our experimental and computational studies.

  7. Solar-powered alkali metal vapor lasers

    NASA Technical Reports Server (NTRS)

    Blount, Charles E.

    1989-01-01

    The emission spectrum of the A(1 Sigma u +) - X(1 Sigma g +) band of Na2 has been recorded following excitation by monochromatic radiation in the region of X-A and X-B absorption. The spectral profile has been investigated as a function of excitation wavelength, sodium vapor temperature and buffer gas pressure. Additionally, gain measurements were made for the satellite of the A-X band as a function of the sodium vapor temperature and buffer gas pressure.

  8. A Three Level Analytic Model for Alkali Vapor Lasers

    SciTech Connect

    Hager, Gordon D.; Perram, Glen P.

    2010-10-08

    A three level analytic model for optically pumped alkali metal vapor lasers is developed considering the steady-state rate equations for the longitudinally averaged number densities of the ground {sup 2}S{sub 1/2} and first excited {sup 2}P{sub 1/2} and {sup 2}P{sub 3/2} states. The threshold pump intensity includes both the requirements to fully bleach the pump transition and exceed optical losses, typically about 200 W/cm{sup 2}. Slope efficiency depends critically on the fraction of incident photons absorbed and the overlap of pump and resonator modes, approaching the quantum efficiency of 0.95-0.98, depending on alkali atom. For efficient operation, the collisional relaxation between the two upper levels should be fast relative to stimulated emission. By assuming a statistical distribution between the upper levels, the limiting analytic solution for the quasi-two level system is achieved. Application of the model and comparisons to recent laser demonstrations is presented.

  9. High-energy transversely pumped alkali vapor laser

    NASA Astrophysics Data System (ADS)

    Zweiback, J.; Komashko, A.

    2011-03-01

    We report on the results from our transversely pumped alkali laser. This system uses an Alexandrite laser to pump a stainless steel laser head. The system uses methane and helium as buffer gasses. Using rubidium, the system produced up to 40 mJ of output energy when pumped with 63 mJ. Slope efficiency was 75%. Using potassium as the lasing species the system produced 32 mJ and a 53% slope efficiency.

  10. Multimode-diode-pumped gas (alkali-vapor) laser

    SciTech Connect

    Page, R H; Beach, R J; Kanz, V K

    2005-08-22

    We report the first demonstration of a multimode-diode-pumped gas laser--Rb vapor operating on the 795 nm resonance transition. Peak output of {approx}1 Watt was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.

  11. Excimer-pumped alkali vapor lasers: a new class of photoassociation lasers

    NASA Astrophysics Data System (ADS)

    Readle, J. D.; Wagner, C. J.; Verdeyen, J. T.; Spinka, T. M.; Carroll, D. L.; Eden, J. G.

    2010-02-01

    Excimer-pumped alkali vapor lasers (XPALs) are a new class of photoassociation lasers which take advantage of the spectrally broad absorption profiles of alkali-rare gas collision pairs. In these systems, transient alkali-rare gas molecules are photopumped from the thermal continuum to a dissociative X2Σ+ 1/2 interaction potential, subsequently populating the n2P3/2 state of the alkali. The absorption profiles >=5 nm and quantum efficiencies >98% have been observed in oscillator experiments, indicating XPAL compatibility with conventional high power laser diode arrays. An alternative technique for populating the n2P3/2 state is direct photoexcitation on the n2P3/2<--n2S1/2 atomic transition. However, because the XPAL scheme employs an off-resonant optical pump, the strengths of resonantly-enhanced nonlinear processes are minimized. Additionally, the absorption coefficient may be adjusted by altering the number densities of the lasing species and/or perturbers, a valuable asset in the design of large volume, high power lasers. We present an overview of XPAL lasers and their operation, including the characteristics of recently demonstrated systems photopumped with a pulsed dye laser. Lasing has been observed in Cs at both 894 nm and 852 nm by pumping CsAr or CsKr pairs as well as in Rb at 795 nm by pumping RbKr. These results highlight the important role of the perturbing species in determining the strength and position of the excimer absorption profile. It is expected that similar results may be obtained in other gas mixtures as similar collision pair characteristics have historically been observed in a wide variety of transient diatomic species.

  12. Algorithm for evaluation of temperature distribution of a vapor cell in a diode-pumped alkali laser system (part II).

    PubMed

    Han, Juhong; Wang, You; Cai, He; An, Guofei; Zhang, Wei; Xue, Liangping; Wang, Hongyuan; Zhou, Jie; Jiang, Zhigang; Gao, Ming

    2015-04-01

    With high efficiency and small thermally-induced effects in the near-infrared wavelength region, a diode-pumped alkali laser (DPAL) is regarded as combining the major advantages of solid-state lasers and gas-state lasers and obviating their main disadvantages at the same time. Studying the temperature distribution in the cross-section of an alkali-vapor cell is critical to realize high-powered DPAL systems for both static and flowing states. In this report, a theoretical algorithm has been built to investigate the features of a flowing-gas DPAL system by uniting procedures in kinetics, heat transfer, and fluid dynamic together. The thermal features and output characteristics have been simultaneously obtained for different gas velocities. The results have demonstrated the great potential of DPALs in the extremely high-powered laser operation. PMID:25968778

  13. Blue satellites of absorption spectrum study of sodium based excimer-pumped alkali vapor laser

    NASA Astrophysics Data System (ADS)

    Hu, Shu; Gai, Baodong; Guo, Jingwei; Tan, Yannan; Liu, Jinbo; Li, Hui; Cai, Xianglong; Shi, Zhe; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2015-02-01

    Sodium based excimer-pump alkali laser (Na-XPAL) is expected to be an efficient method to generate sodium beacon light, but the information about the spectroscopic characters of Na-XPAL remains sparse so far. In this work, we utilized the relative fluorescence intensity to study the absorption spectrum of blue satellites of complexes of sodium with different collision partners. The yellow fluorescence of Na D1 and D2 line was clearly visible. After processing the fluorescence intensity and the input pumping laser relative intensity, we obtained the Na-CH4 system's blue satellites was from 553nm to 556nm. Meanwhile, we experimentally demonstrated the Na-Ar and Na-Xe system's wavelength range of blue satellites. Also, it was observed that the Na-Xe system's absorption was stronger than the other two systems.

  14. Definition and analysis of the lineshape matching coefficient in diode-pumped alkali vapor lasers

    NASA Astrophysics Data System (ADS)

    Shen, Binglin; Pan, Bailiang; Yang, Jing; Qian, Aiqing; Jiao, Jian

    2014-12-01

    For diode-pumped alkali lasers (DPALs), the matching of lineshape between D2 absorption line and pump light greatly affects the properties of laser output; however, there is rare theoretical study on the quantitative description of the lineshape matching coefficient. In this paper, we put forward a formula to describe the lineshape matching coefficient that represents the matching degree between D2 absorption line and pump light. Dependences of the matching coefficient and optical-optical efficiency on the linewidth ratio between D2 absorption line and pump light, and the center frequency shift of pump light caused by mode hopping are calculated and compared with experimental results in literatures. Results show the definition of lineshape matching coefficient can provide an effective way to improve the pump efficiency of DPALs.

  15. Power scaling of a wavelength-narrowed diode laser system for pumping alkali vapors

    NASA Astrophysics Data System (ADS)

    Hersman, F. W.; Distelbrink, J. H.; Ketel, J.; Wilson, J.; Watt, D. W.

    2016-03-01

    We report a method for locking the output wavelength and reducing the spectral linewidth of diode lasers by feeding back light to the emitters from a wavelength selective external optical cavity. Ten years ago our team developed a stepped-mirror that allowed a single external cavity to lock the wavelength of a stack of diode array bars by equalizing path lengths between each emitter and the grating. Here we report combining one such step-mirror external cavity with an array of power dividers, each sending a portion of this feedback power to a separate diode array bar stack.

  16. Integrating Sphere Alkali-Metal Vapor Cells

    NASA Astrophysics Data System (ADS)

    McGuyer, Bart; Ben-Kish, Amit; Jau, Yuan-Yu; Happer, William

    2010-03-01

    An integrating sphere is an optical multi-pass cavity that uses diffuse reflection to increase the optical path length. Typically applied in photometry and radiometry, integrating spheres have previously been used to detect trace gases and to cool and trap alkali-metal atoms. Here, we investigate the potential for integrating spheres to enhance optical absorption in optically thin alkali-metal vapor cells. In particular, we consider the importance of dielectric effects due to a glass container for the alkali-metal vapor. Potential applications include miniature atomic clocks and magnetometers, where multi-passing could reduce the operating temperature and power consumption.

  17. Spatial Polarization Profile in an Optically Pumped Alkali Vapor

    NASA Astrophysics Data System (ADS)

    Olsen, Ben; Patton, Brian; Jau, Yuan-Yu; Happer, Will

    2009-05-01

    Spin-Exchange Optical Pumping (SEOP) is a technique used to polarize nuclei in gases, and more recently in solids, in excess of their equilibrium limit. SEOP is achieved by optically pumping an alkali vapor which subsequently transfers angular momentum to the nuclei of interest. The efficiency of SEOP is governed by optical pumping and relaxation of the alkali atoms, relaxation of the target nuclei, and interactions between the alkali and target substance. In this work we investigate the relationship between optical pumping and relaxation in cesium vapor with absorption spectroscopy at high magnetic field (2.7 T). Cesium vapor within a cylindrical glass vapor cell is optically pumped with a strong laser resonant with a D2 transition. The ground-state population of the vapor is measured at various positions along a diameter of the cell with a small, weak D1 laser beam which translates mechanically. The resulting polarization profile elucidates the interplay between optical pumping, diffusion in the buffer gas, and relaxation at the walls of the vapor cell. We report measurements of the spatial polarization profile in vapor cells with bare Pyrex walls and cells coated with paraffin (an anti-relaxation coating) or CsH salt (a target substance for SEOP), and compare them to numerical simulations. Further investigation might yield a new method for characterizing surface relaxation in vapor cells.

  18. Diode pumped alkali lasers (DPALs): an overview

    NASA Astrophysics Data System (ADS)

    Krupke, William F.

    2008-05-01

    The concept of power-scalable, high beam-quality diode pumped alkali lasers was introduced in 2003 [Krupke, US Patent No. 6,643,311; Opt. Letters, 28, 2336 (2003)]. Since then several laboratory DPAL devices have been reported on, confirming many of the spectroscopic, kinetic, and laser characteristics projected from literature data. This talk will present an overview of the DPAL concept, summarize key relevant properties of the cesium, rubidium, and potassium alkali vapor gain media so-far examined, outline power scaling considerations, and highlight results of published DPAL laboratory experiments.

  19. Terahertz radiation in alkali vapor plasmas

    SciTech Connect

    Sun, Xuan; Zhang, X.-C.

    2014-05-12

    By taking advantage of low ionization potentials of alkali atoms, we demonstrate terahertz wave generation from cesium and rubidium vapor plasmas with an amplitude nearly one order of magnitude larger than that from nitrogen gas at low pressure (0.02–0.5 Torr). The observed phenomena are explained by the numerical modeling based upon electron tunneling ionization.

  20. Spill-Resistant Alkali-Metal-Vapor Dispenser

    NASA Technical Reports Server (NTRS)

    Klipstein, William

    2005-01-01

    A spill-resistant vessel has been developed for dispensing an alkali-metal vapor. Vapors of alkali metals (most commonly, cesium or rubidium, both of which melt at temperatures slightly above room temperature) are needed for atomic frequency standards, experiments in spectroscopy, and experiments in laser cooling. Although the present spill-resistant alkali-metal dispenser was originally intended for use in the low-gravity environment of outer space, it can also be used in normal Earth gravitation: indeed, its utility as a vapor source was confirmed by use of cesium in a ground apparatus. The vessel is made of copper. It consists of an assembly of cylinders and flanges, shown in the figure. The uppermost cylinder is a fill tube. Initially, the vessel is evacuated, the alkali metal charge is distilled into the bottom of the vessel, and then the fill tube is pinched closed to form a vacuum seal. The innermost cylinder serves as the outlet for the vapor, yet prevents spilling by protruding above the surface of the alkali metal, no matter which way or how far the vessel is tilted. In the event (unlikely in normal Earth gravitation) that any drops of molten alkali metal have been shaken loose by vibration and are floating freely, a mesh cap on top of the inner cylinder prevents the drops from drifting out with the vapor. Liquid containment of the equivalent of 1.2 grams of cesium was confirmed for all orientations with rubbing alcohol in one of the prototypes later used with cesium.

  1. Magnetic Resonance Reversals in Optically Pumped Alkali-Metal Vapor

    NASA Astrophysics Data System (ADS)

    Gong, Fei; Jau, Yuan-Yu; Happer, William

    2007-06-01

    We report an unusual new phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the ``zero-dip" resonance (Zeeman resonance at zero field) of optically-pumped, alkali-metal vapors. These anomalies occur when a ``weak" circular polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in simple, semi-quantitative way with reference to this distribution. uantitative computer simulations are in excellent greement with observations.

  2. Magnetic resonance reversals in optically pumped alkali-metal vapor

    NASA Astrophysics Data System (ADS)

    Gong, F.; Jau, Y.-Y.; Happer, W.

    2007-05-01

    We report an unusual phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the zero-dip resonance (Zeeman resonance at zero field) of optically pumped, alkali-metal vapors. These anomalies occur when a weak circularly polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in a simple, semiquantitative way with reference to the spin-temperature distribution. Quantitative computer simulations are in excellent agreement with observations.

  3. Advancements in flowing diode pumped alkali lasers

    NASA Astrophysics Data System (ADS)

    Pitz, Greg A.; Stalnaker, Donald M.; Guild, Eric M.; Oliker, Benjamin Q.; Moran, Paul J.; Townsend, Steven W.; Hostutler, David A.

    2016-03-01

    Multiple variants of the Diode Pumped Alkali Laser (DPAL) have recently been demonstrated at the Air Force Research Laboratory (AFRL). Highlights of this ongoing research effort include: a) a 571W rubidium (Rb) based Master Oscillator Power Amplifier (MOPA) with a gain (2α) of 0.48 cm-1, b) a rubidium-cesium (Cs) Multi-Alkali Multi-Line (MAML) laser that simultaneously lases at both 795 nm and 895 nm, and c) a 1.5 kW resonantly pumped potassium (K) DPAL with a slope efficiency of 50%. The common factor among these experiments is the use of a flowing alkali test bed.

  4. An electron diffraction study of alkali chloride vapors

    NASA Technical Reports Server (NTRS)

    Mawhorter, R. J.; Fink, M.; Hartley, J. G.

    1985-01-01

    A study of monomers and dimers of the four alkali chlorides NaCl, KCl, RbCl, and CsCl in the vapor phase using the counting method of high energy electron diffraction is reported. Nozzle temperatures from 850-960 K were required to achieve the necessary vapor pressures of approximately 0.01 torr. Using harmonic calculations for the monomer and dimer 1 values, a consistent set of structures for all four molecules was obained. The corrected monomer distances reproduce the microwave values very well. The experiment yields information on the amount of dimer present in the vapor, and these results are compared with thermodynamic values.

  5. Multi-photon processes in alkali metal vapors

    NASA Astrophysics Data System (ADS)

    Gai, Baodong; Hu, Shu; Li, Hui; Shi, Zhe; Cai, Xianglong; Guo, Jingwei; Tan, Yannan; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2015-02-01

    Achieving population inversion through multi-photon cascade pumping is almost always difficult, and most laser medium work under 1-photon excitation mechanism. But for alkali atoms such as cesium, relatively large absorption cross sections of several low, cascading energy levels enable them properties such as up conversion. Here we carried out research on two-photon excitation alkali fluorescence. Two photons of near infrared region are used to excite alkali atoms to n 2 D5/2, n 2 D3/2 or higher energy levels, then the blue fluorescence of (n+1) 2 P3/2,(n+1) 2 P1/2-->n 2 S1/2 are observed. Different pumping paths are tried and by the recorded spectra, transition routes of cesium are deducted and concluded. Finally the possibility of two-photon style DPALs (diode pumped alkali laser) are discussed, such alkali lasers can give output wavelengths in the shorter end of visual spectroscopy (400-460 nm) and are expected to get application in underwater communication and material laser processing.

  6. [The Measuring Method of Atomic Polarization of Alkali Metal Vapor Based on Optical Rotation and the Analysis of the Influence Factors].

    PubMed

    Shang, Hui-ning; Quan, Wei; Chen, Yao; Li, Yang; Li, Hong

    2016-02-01

    High sensitivity measurements of inertia and magnetic field could be achieved by utilizing a category of devices, which manipulate the atomic spins in the spin-exchange-relaxation-free regime. The alkali cell which contains the alkali metal vapor is used to sense magnetic field and inertia. The atomic number density of alkali vapor and the polarization of alkali metal vapor are two of the most important parameters of the cell. They play an important role in the research on atomic spins in the spin-exchange-relaxation-free regime. Besides, optical polarization plays an important role in quantum computing and atomic physics. We propose a measurement of alkali vapor polarization and alkali number density by detecting the optical rotation in one system. This method simplifies existing experimental equipment and processes. A constant bias magnetic field is applied and the Faraday rotation angle is detected by a bunch of the probe beam to deduce alkali-metal density. Then the magnetic field is closed and a bunch of the pump laser is utilized to polarize alkali-metal. Again, the probe beam is utilized to obtain the polarization of alkali metal. The alkali density obtained at first is used to deduce the polarization. This paper applies a numerical method to analyze the Faraday rotation and the polarization rotation. According to the numerical method, the optimal wavelength for the experiment is given. Finally, the fluctuation of magnetic field and wavelength on signal analysis are analyzed. PMID:27209720

  7. Plasma Formation During Operation of a Diode Pumped Alkali Laser (DPAL) in Cs

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu.; Zatsarinny, Oleg; Bartschat, Klaus; Kushner, Mark J.

    2014-10-01

    Diode pumped Alkali Lasers (DPALs) produce laser action on the resonant lines of alkali atoms. Diode lasers resonantly pump the 2P3/2 state of the alkali atom which is collisionally relaxed to the 2P3/2 state which then lases to the ground state 2S1/2. The low optical quality of high power semiconductor diode lasers is converted into high optical quality laser radiation from the alkali vapor. The Cs DPAL system using Ar/Cs/C2H6 mixtures has shown promising results. (C2H6 is the collisional relaxant.) In other studies, resonant excitation of alkali vapor by low power lasers has been used to produce highly ionized channels, initiated through associative ionization and superelastic electron heating. The issue then arises if plasma formation occurs during DPAL by similar mechanisms which would be detrimental to laser performance. In this paper, we report on results from a computational study of a DPAL using Cs vapor. The global model addresses quasi-cw pumping of the Cs(2P3/2) state by laser diodes, and includes a full accounting of the resulting electron kinetics. To enable this study, the B-spline R-matrix (BSR) with pseudostates method was employed to calculate electron impact cross sections for Cs. We found that for pump rates of many to 10 kW/cm2, plasma densities approaching 1013 cm-3 occur during laser oscillation with higher values in the absence of laser oscillation. Supported by DoD High Energy Laser Mult. Res. Initiative and NSF.

  8. Alkali-vapor cell with metal coated windows for efficient application of an electric field

    NASA Astrophysics Data System (ADS)

    Sarkisyan, D.; Sarkisyan, A. S.; Guéna, J.; Lintz, M.; Bouchiat, M.-A.

    2005-05-01

    We describe the implementation of a cylindrical T-shaped alkali-vapor cell for laser spectroscopy in the presence of a longitudinal electric field. The two windows are used as two electrodes of the high-voltage assembly, which is made possible by a metallic coating which entirely covers the inner and outer sides of the windows except for a central area to let the laser beams in and out of the cell. This allows very efficient application of the electric field, up to 2kV/cm in a rather dense superheated vapor, even when significant photoemission takes place at the windows during pulsed laser irradiation. The body of the cell is made of sapphire or alumina ceramic to prevent large currents resulting from surface conduction observed in cesiated glass cells. The technique used to attach the monocrystalline sapphire windows to the cell body causes minimal stress birefringence in the windows. In addition, reflection losses at the windows can be made very small. The vapor cell operates with no buffer gas and has no magnetic part. The use of this kind of cell has resulted in an improvement of the signal-to-noise ratio in the measurement of parity violation in cesium vapor underway at ENS, Paris. The technique can be applied to other situations where a brazed assembly would give rise to unacceptably large birefringence in the windows.

  9. (abstract) Fundamental Mechanisms of Electrode Kinetics and Alkali Metal Atom Transport at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kisor, A.; Kikkert, S. K.

    1993-01-01

    The mechanisms of electrode kinetics and mass transport of alkali metal oxidation and alkali metal cation reduction at the solid electrolyte/porous electrode boundary as well as alkali metal transport through porous metal electrodes has important applications in optimizing device performance in alkali metal thermal to electric converter (AMTEC) cells which are high temperature, high current density electrochemical cells. Basic studies of these processes also affords the opportunity to investigate a very basic electrochemical reaction over a wide range of conditions; and a variety of mass transport modes at high temperatures via electrochemical techniques. The temperature range of these investigations covers 700K to 1240K; the alkali metal vapor pressures range from about 10(sup -2) to 10(sup 2) Pa; and electrodes studied have included Mo, W, Mo/Na(sub 2)MoO(sub 4), W/Na(sub 2)WO(sub 4), WPt(sub x), and WRh(sub x) (1.0 < x < 6.0 ) with Na at Na-beta'-alumina, and Mo with K at K-beta'-alumina. Both liquid metal/solid electrolyte/alkali metal vapor and alkali metal vapor/solid electrolyte/vapor cells have been used to characterize the reaction and transport processes. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes.

  10. Ionic alkali halide XUV laser feasibility study

    SciTech Connect

    Yang, T.T.; Gylys, V.T.; Bower, R.D.; Harris, D.G.; Blauer, J.A.; Turner, C.E.; Hindy, R.N.

    1989-11-10

    The objective of this work is to assess the feasibility of a select set of ionic alkali halide XUV laser concepts by obtaining the relevant kinetic and spectroscopic parameters required for a proof-of-principle and conceptual design. The proposed lasers operate in the 80--200 nm spectral region and do not require input from outside radiation sources for their operation. Frequency up-conversion and frequency mixing techniques and therefore not considered in the work to be described. An experimental and theoretical study of a new type of laser operating in the extreme ultraviolet wavelength region has been conducted. The lasing species are singly ionized alkali halide molecules such as Rb{sup 2+}F{sub {minus}}, Rb{sup 2+}Br{sup {minus}} and Cs{sup 2+}F{sup {minus}}. These species are similar in electronic structure to the rare gas halide excimers, such as XeF and Krf, except that the ionic molecules emit at wavelengths of 80--200 nm, much shorter than the conventional rare-gas halide excimer laser. The radiative lifetime of these molecules are typically near 1 ns, which is about an order of magnitude shorter than that for rare-gas halide systems. The values of the cross section for stimulated emission are on the order of 1 {times} 10{sup {minus}16}cm{sup 2}. Because of the fundamental similarity to existing UV lasers, these systems show promise as a high power, efficient XUV lasers. 55 refs., 50 figs., 5 tabs.

  11. On-chip fabrication of alkali-metal vapor cells utilizing an alkali-metal source tablet

    NASA Astrophysics Data System (ADS)

    Tsujimoto, K.; Ban, K.; Hirai, Y.; Sugano, K.; Tsuchiya, T.; Mizutani, N.; Tabata, O.

    2013-11-01

    We describe a novel on-chip microfabrication technique for the alkali-metal vapor cell of an optically pumped atomic magnetometer (OPAM), utilizing an alkali-metal source tablet (AMST). The newly proposed AMST is a millimeter-sized piece of porous alumina whose considerable surface area holds deposited alkali-metal chloride (KCl) and barium azide (BaN6), source materials that effectively produce alkali-metal vapor at less than 400 °C. Our experiments indicated that the most effective pore size of the AMST is between 60 and 170 µm. The thickness of an insulating glass spacer holding the AMST was designed to confine generated alkali metal to the interior of the vapor cell during its production, and an integrated silicon heater was designed to seal the device using a glass frit, melted at an optimum temperature range of 460-490 °C that was determined by finite element method thermal simulation. The proposed design and AMST were used to successfully fabricate a K cell that was then operated as an OPAM with a measured sensitivity of 50 pT. These results demonstrate that the proposed concept for on-chip microfabrication of alkali-metal vapor cells may lead to effective replacement of conventional glassworking approaches.

  12. Atomic vapor laser isotope separation process

    DOEpatents

    Wyeth, R.W.; Paisner, J.A.; Story, T.

    1990-08-21

    A laser spectroscopy system is utilized in an atomic vapor laser isotope separation process. The system determines spectral components of an atomic vapor utilizing a laser heterodyne technique. 23 figs.

  13. Alkali element background reduction in laser ICP-MS

    NASA Astrophysics Data System (ADS)

    Magee, C. W., Jr.; Norris, C. A.

    2014-11-01

    Alkali backgrounds in laser ablation ICP-MS analyses can be enhanced by electron-induced ionization of alkali contamination on the skimmer cone, reducing effective detection limits for these elements. Traditionally, this problem is addressed by isolating analyses of high alkali materials onto a designated cone set, or by operating the ICP-MS in a "soft extraction" mode, which reduces the energy of electrons repelled into the potentially contaminated sampling cone by the extraction field. Here we present a novel approach, where we replace the traditional alkali glass tuning standards with synthetic low-alkali glass reference materials. Using this vitreous tuning solution, we find that this approach reduces the amount of alkali contamination produced, halving backgrounds for the heavy alkali elements without any change to analytical procedures. Using segregated cones is still the most effective method for reducing lithium backgrounds, but since the procedures are complimentary both can easily be applied to the routine operations of an analytical lab.

  14. Alkali element background reduction in laser ICP-MS

    NASA Astrophysics Data System (ADS)

    Magee, C. W., Jr.; Norris, C. A.

    2015-03-01

    Alkali backgrounds in laser ablation ICP-MS analyses can be enhanced by electron-induced ionisation of alkali contamination on the skimmer cone, reducing effective detection limits for these elements. Traditionally, this problem is addressed by isolating analyses of high-alkali materials onto a designated cone set, or by operating the ICP-MS in a "soft extraction" mode, which reduces the energy of electrons repelled into the potentially contaminated sampling cone by the extraction field. Here we present a novel approach, where we replace the traditional alkali glass tuning standards with synthetic low-alkali glass reference materials. Using this vitreous tuning solution, we find that this approach reduces the amount of alkali contamination produced, halving backgrounds for the heavy alkali elements without any change to analytical procedures. Using segregated cones is still the most effective method for reducing lithium backgrounds, but since the procedures are complimentary, both can easily be applied to the routine operations of an analytical lab.

  15. Faraday rotation density measurements of optically thick alkali metal vapors

    NASA Astrophysics Data System (ADS)

    Vliegen, E.; Kadlecek, S.; Anderson, L. W.; Walker, T. G.; Erickson, C. J.; Happer, William

    2001-03-01

    We investigate the measurement of alkali number densities using the Faraday rotation of linearly polarized light. We find that the alkali number density may be reliably extracted even in regimes of very high buffer gas pressure, and very high alkali number density. We have directly verified our results in potassium using absorption spectroscopy on the second resonance (4 2S→5 2P).

  16. High-temperature interactions of alkali vapors with solids during coal combustion and gasification

    SciTech Connect

    Punjak, W.A.

    1988-01-01

    A temperature and concentration programmed reaction method is used to investigate the mechanism by which organically bound alkali is released from carbonaceous substrates. Vaporization of the alkali is preceded by reduction of oxygen-bearing groups during which CO is generated. A residual amount of alkali remains after complete reduction. This residual level is greater for potassium, indicating that potassium has stronger interactions with graphitic substrates that sodium. Other mineral substrates were exposed to high temperature alkali chloride vapors under both nitrogen and simulated flue gas atmospheres to investigate their potential application as sorbents for the removal of alkali from coal conversion flue gases. The compounds containing alumina and silica are found to readily adsorb alkali vapors and the minerals kaolinite, bauxite and emathlite are identified as promising alkali sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite and emathlite are compared and analyzed both experimentally and through theoretical modeling. The experiments were performed in a microgravimetric reactor system; the sorbents were characterized before and after alkali adsorption using scanning Auger microscopy, X-ray diffraction analysis, mercury porosimetry and atomic emission spectrophotometry. The results show that the process is not a simple physical condensation, but a complex combination of several diffusion steps and reactions.

  17. Microfabricated alkali vapor cell with anti-relaxation wall coating

    SciTech Connect

    Straessle, R.; Pétremand, Y.; Briand, D.; Rooij, N. F. de; Pellaton, M.; Affolderbach, C.; Mileti, G.

    2014-07-28

    We present a microfabricated alkali vapor cell equipped with an anti-relaxation wall coating. The anti-relaxation coating used is octadecyltrichlorosilane and the cell was sealed by thin-film indium-bonding at a low temperature of 140 °C. The cell body is made of silicon and Pyrex and features a double-chamber design. Depolarizing properties due to liquid Rb droplets are avoided by confining the Rb droplets to one chamber only. Optical and microwave spectroscopy performed on this wall-coated cell are used to evaluate the cell's relaxation properties and a potential gas contamination. Double-resonance signals obtained from the cell show an intrinsic linewidth that is significantly lower than the linewidth that would be expected in case the cell had no wall coating but only contained a buffer-gas contamination on the level measured by optical spectroscopy. Combined with further experimental evidence this proves the presence of a working anti-relaxation wall coating in the cell. Such cells are of interest for applications in miniature atomic clocks, magnetometers, and other quantum sensors.

  18. Feasibility of supersonic diode pumped alkali lasers: Model calculations

    SciTech Connect

    Barmashenko, B. D.; Rosenwaks, S.

    2013-04-08

    The feasibility of supersonic operation of diode pumped alkali lasers (DPALs) is studied for Cs and K atoms applying model calculations, based on a semi-analytical model previously used for studying static and subsonic flow DPALs. The operation of supersonic lasers is compared with that measured and modeled in subsonic lasers. The maximum power of supersonic Cs and K lasers is found to be higher than that of subsonic lasers with the same resonator and alkali density at the laser inlet by 25% and 70%, respectively. These results indicate that for scaling-up the power of DPALs, supersonic expansion should be considered.

  19. Laser using lead chloride vapor

    NASA Technical Reports Server (NTRS)

    Chen, C. J.

    1975-01-01

    By applying electric discharge, lead chloride vapor in tube is dissociated into lead and chlorine atoms. Population inversion of lead atoms is attained subsequently by second discharge, before chemical recombination of lead and chlorine has occurred. Optimum time interval between two discharges is required for maximum laser output.

  20. Saturated vapor pressure above the amalgam of alkali metals in discharge lamps

    NASA Astrophysics Data System (ADS)

    Gavrish, S. V.

    2011-12-01

    A theoretical and numerical analysis of the evaporation process of two-component compounds in vapors of alkali metals in discharge lamps is presented. Based on the developed mathematical model of calculation of saturated vapor pressure of the metal above the amalgam, dependences of mass fractions of the components in the discharge volume on design parameters and thermophysical characteristics of the lamp are obtained.

  1. Wick for metal vapor laser

    DOEpatents

    Duncan, David B.

    1992-01-01

    An improved wick for a metal vapor laser is made of a refractory metal cylinder, preferably molybdenum or tungsten for a copper laser, which provides the wicking surface. Alternately, the inside surface of the ceramic laser tube can be metalized to form the wicking surface. Capillary action is enhanced by using wire screen, porous foam metal, or grooved surfaces. Graphite or carbon, in the form of chunks, strips, fibers or particles, is placed on the inside surface of the wick to reduce water, reduce metal oxides and form metal carbides.

  2. Alkali resistant optical coatings for alkali lasers and methods of production thereof

    DOEpatents

    Soules, Thomas F; Beach, Raymond J; Mitchell, Scott C

    2014-11-18

    In one embodiment, a multilayer dielectric coating for use in an alkali laser includes two or more alternating layers of high and low refractive index materials, wherein an innermost layer includes a thicker, >500 nm, and dense, >97% of theoretical, layer of at least one of: alumina, zirconia, and hafnia for protecting subsequent layers of the two or more alternating layers of high and low index dielectric materials from alkali attack. In another embodiment, a method for forming an alkali resistant coating includes forming a first oxide material above a substrate and forming a second oxide material above the first oxide material to form a multilayer dielectric coating, wherein the second oxide material is on a side of the multilayer dielectric coating for contacting an alkali.

  3. Diode-Pumped Alkali Atom Lasers 03-LW-024 Final Report

    SciTech Connect

    Page, R H; Beach, R J

    2005-02-16

    The recent work at LLNL on alkali-atom lasers has been remarkably successful and productive. Three main phases (so far) can be identified. First, the concept and demonstration of red lasers using (Ti:sapphire pumping) took place; during this time, Rubidium and Cesium resonance-line lasers were tested, and theoretical models were developed and shown to describe experimental results very reliably. Work done during this first phase has been well documented, and the models from that period are still in use for their predictions and for designing power-scaled lasers. [1 - 3] Second, attempts were made to produce a blue alkali-vapor laser using sequentially-resonant two-step pumping (again, using Ti:sapphire lasers.) Although a blue laser did not result, the physical limitations of our approach are now better-defined. Third, diode-pumped operation of a red laser (Rubidium) was attempted, and we eventually succeeded in demonstrating the world's first diode-pumped gas laser. [4] Because we have a defensible concept for producing an efficient, compact, lightweight, power-scaled laser (tens of kW,) we are in a position to secure outside funding, and would like to find a sponsor. For descriptions of work done during the ''first phase,'' see References [1 - 3] ''Phase two'' work is briefly described in the section ''Blue laser,'' and ''phase three'' work is presented in the section entitled ''Diode-pumped red laser.''

  4. Influence of energy pooling and ionization on physical features of a diode-pumped alkali laser.

    PubMed

    An, Guofei; Wang, You; Han, Juhong; Cai, He; Zhou, Jie; Zhang, Wei; Xue, Liangping; Wang, Hongyuan; Gao, Ming; Jiang, Zhigang

    2015-10-01

    In recent years, a diode-pumped alkali laser (DPAL) has become one of the most hopeful candidates to achieve the high power performance. A series of models have been established to analyze the DPAL's kinetic process and most of them were based on the algorithms in which only the ideal 3-level system was considered. In this paper, we developed a systematic model by taking into account the influence of excitation of neutral alkali atoms to even-higher levels and their ionization on the physical features of a static DPAL. The procedures of heat transfer and laser kinetics were combined together in our theoretical model. By using such a theme, the continuous temperature and number density distribution have been evaluated in the transverse section of a cesium vapor cell. The calculated results indicate that both energy pooling and ionization play important roles during the lasing process. The conclusions might deepen the understanding of the kinetic mechanism of a DPAL. PMID:26480154

  5. Spin Transfer from an Optically Pumped Alkali Vapor to a Solid

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Patton, B.; Jau, Y.-Y.; Happer, W.

    2007-05-01

    We report enhancement of the spin polarization of Cs133 nuclei in CsH salt by spin transfer from an optically pumped cesium vapor. The nuclear polarization was 4.0 times the equilibrium polarization at 9.4 T and 137°C, with larger enhancements at lower fields. This work is the first demonstration of spin transfer from a polarized alkali vapor to the nuclei of a solid, opening up new possibilities for research in hyperpolarized materials.

  6. Spin Transfer from an Optically Pumped Alkali Vapor to a Solid

    SciTech Connect

    Ishikawa, K.; Patton, B.; Jau, Y.-Y.; Happer, W.

    2007-05-04

    We report enhancement of the spin polarization of {sup 133}Cs nuclei in CsH salt by spin transfer from an optically pumped cesium vapor. The nuclear polarization was 4.0 times the equilibrium polarization at 9.4 T and 137 deg. C, with larger enhancements at lower fields. This work is the first demonstration of spin transfer from a polarized alkali vapor to the nuclei of a solid, opening up new possibilities for research in hyperpolarized materials.

  7. Intrinsic Impurities in Glass Alkali-Vapor Cells

    NASA Astrophysics Data System (ADS)

    Patton, B.; Ishikawa, K.; Jau, Y.-Y.; Happer, W.

    2007-07-01

    We report NMR measurements of metallic Cs133 in glass cells. The solid-liquid phase transition was studied by observing the NMR peaks arising from these two phases; surprisingly, many cells yielded two additional NMR peaks below the melting point. We attribute these signals to two distinct impurities which can dissolve in the liquid alkali metal and affect its chemical shift. Intentional contamination of cesium cells with O2 confirms this hypothesis for one peak. The other contaminant remains unknown but can appear in evacuated cells. Similar effects have been seen in Rb87 cells.

  8. Computation of three-dimensional temperature distribution in diode-pumped alkali vapor amplifiers

    NASA Astrophysics Data System (ADS)

    Shen, Binglin; Xu, Xingqi; Xia, Chunsheng; Pan, Bailiang

    2016-06-01

    Combining the kinetic and fluid dynamic processes in static and flowing-gas diode-pumped alkali vapor amplifiers, a comprehensive physical model with a cyclic iterative approach for calculating the three-dimensional temperature distribution of the vapor cell is established. Taking into account heat generation, thermal conductivity and convection, the excitation of the alkali atoms to high electronic levels, and their losses due to ionization in the gain medium, the thermal features and output characteristics have been simultaneously obtained. The results are in good agreement with those of the measurement in a static rubidium vapor amplifier. Influences of gas velocity on radial and axial temperature profiles are simulated and analyzed. The results have demonstrated that thermal problems in gaseous gain medium can be significantly reduced by flowing the gain medium with sufficiently high velocity.

  9. The direct observation of alkali vapor species in biomass combustion and gasification

    SciTech Connect

    French, R J; Dayton, D C; Milne, T A

    1994-01-01

    This report summarizes new data from screening various feedstocks for alkali vapor release under combustion conditions. The successful development of a laboratory flow reactor and molecular beam, mass spectrometer interface is detailed. Its application to several herbaceous and woody feedstocks, as well as a fast-pyrolysis oil, under 800 and 1,100{degrees}C batch combustion, is documented. Chlorine seems to play a large role in the facile mobilization of potassium. Included in the report is a discussion of relevant literature on the alkali problem in combustors and turbines. Highlighted are the phenomena identified in studies on coal and methods that have been applied to alkali speciation. The nature of binding of alkali in coal versus biomass is discussed, together with the implications for the ease of release. Herbaceous species and many agricultural residues appear to pose significant problems in release of alkali species to the vapor at typical combustor temperatures. These problems could be especially acute in direct combustion fired turbines, but may be ameliorated in integrated gasification combined cycles.

  10. Copper vapor laser modular packaging assembly

    DOEpatents

    Alger, T.W.; Ault, E.R.; Moses, E.I.

    1992-12-01

    A modularized packaging arrangement for one or more copper vapor lasers and associated equipment is disclosed herein. This arrangement includes a single housing which contains the laser or lasers and all their associated equipment except power, water and neon, and means for bringing power, water, and neon which are necessary to the operation of the lasers into the container for use by the laser or lasers and their associated equipment. 2 figs.

  11. Copper vapor laser modular packaging assembly

    DOEpatents

    Alger, Terry W.; Ault, Earl R.; Moses, Edward I.

    1992-01-01

    A modularized packaging arrangement for one or more copper vapor lasers and associated equipment is disclosed herein. This arrangement includes a single housing which contains the laser or lasers and all their associated equipment except power, water and neon, and means for bringing power, water, and neon which are necessary to the operation of the lasers into the container for use by the laser or lasers and their associated equipment.

  12. Calculation of transmittance of diode pumped alkali laser in atmosphere propagation

    NASA Astrophysics Data System (ADS)

    Que, Yiqin; Hua, Weihong; Wang, Hongyan; Yang, Zining; Xu, Xiaojun

    2013-05-01

    Diode pumped alkali vapor lasers (DPAL) is a rising high-energy laser. The wavelength of which is consistent with the response curve peak position of solar cell, and it has broad application prospects in laser directed energy transfer. The paper bases on the application of solar unmanned aerial vehicle (UAV) energy transfer in high altitude and longendurance conditions. For the first time by using the MODTRAN and FASCODE, we calculate the transmittance of Potassium, rubidium, cesium laser in the typical atmospheric conditions vertically and different angles of atmospheric slant path by the numbers, The result shows that DPAL has a very high atmospheric transmittance, and also a valuable reference in other applications with the atmospheric transmission.

  13. New Class of CW High-Power Diode-Pumped Alkali Lasers (DPALs)

    SciTech Connect

    Krupke, W F; Beach, R J; Kanz, V K; Payne, S A; Early, J T

    2004-03-23

    The new class of diode-pumped alkali vapor lasers (DPALs) offers high efficiency cw laser radiation at near-infrared wavelengths: cesium 895 nm, rubidium 795 nm, and potassium 770 nm. The working physical principles of DPALs will be presented. Initial 795 nm Rb and 895 nm Cs laser experiments performed using a titanium sapphire laser as a surrogate pump source demonstrated DPAL slope power conversion efficiencies in the 50-70% range, in excellent agreement with device models utilizing only literature spectroscopic and kinetic data. Using these benchmarked models for Rb and Cs, optimized DPALs with optical-optical efficiencies >60%, and electrical efficiencies of 25-30% are projected. DPAL device architectures for near-diffraction-limited power scaling into the high kilowatt power regime from a single aperture will be described. DPAL wavelengths of operation offer ideal matches to silicon and gallium arsenide based photovoltaic power conversion cells for efficient power beaming.

  14. (abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1993-01-01

    The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

  15. Ab Initio Molecular Dynamics of Dimerization and Clustering in Alkali Metal Vapors.

    PubMed

    Chaban, Vitaly V; Prezhdo, Oleg V

    2016-06-30

    Alkali metals are known to form dimers, trimers, and tetramers in their vapors. The mechanism and regularities of this phenomenon characterize the chemical behavior of the first group elements. We report ab initio molecular dynamics (AIMD) simulations of the alkali metal vapors and characterize their structural properties, including radial distribution functions and atomic cluster size distributions. AIMD confirms formation of Men, where n ranges from 2 to 4. High pressure sharply favors larger structures, whereas high temperature decreases their fraction. Heavier alkali metals maintain somewhat larger fractions of Me2, Me3, and Me4, relative to isolated atoms. A single atom is the most frequently observed structure in vapors, irrespective of the element and temperature. Due to technical difficulties of working with high temperatures and pressures in experiments, AIMD is the most affordable method of research. It provides valuable understanding of the chemical behavior of Li, Na, K, Rb, and Cs, which can lead to development of new chemical reactions involving these metals. PMID:27294399

  16. Wave optics simulation of diode pumped alkali laser (DPAL)

    NASA Astrophysics Data System (ADS)

    Endo, Masamori; Nagaoka, Ryuji; Nagaoka, Hiroki; Nagai, Toru; Wani, Fumio

    2016-03-01

    A numerical simulation code for a diode pumped alkali laser (DPAL) was developed. The code employs the Fresnel- Kirchhoff diffraction integral for both laser mode and pump light propagations. A three-dimensional rate equation set was developed to determine the local gain. The spectral divergence of the pump beam was represented by a series of monochromatic beams with different wavelengths. The calculated results showed an excellent agreements with relevant experimental results. It was found that the main channel of the pump power drain is the spontaneous emission from the upper level of the lasing transition.

  17. Laser synthesis of ultracold alkali metal dimers: optimization and control

    NASA Astrophysics Data System (ADS)

    Pazyuk, E. A.; Zaitsevskii, A. V.; Stolyarov, A. V.; Tamanis, M.; Ferber, R.

    2015-10-01

    The review concerns the potential of modern high-resolution laser spectroscopy and state-of-the-art ab initio electronic structure calculations used to obtain comprehensive information on the energy and radiative properties of strongly coupled rovibronic diatomic states. The possibility of deperturbation treatment of the intermediate electronically excited states at the experimental (spectroscopic) level of accuracy is demonstrated taking alkali metal dimers as examples. The deperturbation analysis is of crucial importance to optimize multistep laser synthesis and stabilization of ultracold molecular ensembles in their absolute ground level. The bibliography includes 227 references.

  18. Novel methods of copper vapor laser excitation

    SciTech Connect

    McColl, W.B.; Ching, H.; Bosch, R.; Brake, M.; Gilgenbach, R.

    1990-12-31

    Microwave and intense electron beam excitation of copper vapor are being investigated to be used in copper vapor lasers for isotope separation. Both methods use copper chloride vapor by heating copper chloride. Helium was used as the buffer gas at 2 to 100 torr. In the microwave system, intense copperlines at 510 nm and 578 nm were observed. Initial electron beam results indicate that light emission follows the beam current.

  19. Alkali element depletion by core formation and vaporization on the early Earth

    NASA Technical Reports Server (NTRS)

    Lodders, K.; Fegley, B., Jr.

    1994-01-01

    The depletion of Na, K, Rb, and Cs in the Earth's upper mantle and crust relative to their abundances in chondrites is a long standing problem in geochemistry. Here we consider two commonly invoked mechanisms, namely core formation, and vaporization, for producing the observed depletions. Our models predict that a significant percentage of the Earth's bulk alkali element inventory is in the core (30 percent for Na, 52 percent for K, 74 percent for Rb, and 92 percent for Cs). These predictions agree with independent estimates from nebular volatility trends and (for K) from terrestrial heat flow data. Our models also predict that vaporization and thermal escape during planetary accretion are unlikely to produce the observed alkali element depletion pattern. However, loss during the putative giant impact which formed the Moon cannot be ruled out. Experimental, observational, and theoretical tests of our predictions are also described. Alkali element partitioning into the Earth's core was modeled by assuming that alkali element partitioning during core formation on the aubrite parent body (APB) is analogous to that on the early Earth. The analogy is reasonable for three reasons. First, the enstatite meteorites are the only known meteorites with the same oxygen isotope systematics as the Earth-Moon system. Second, the large core size of the Earth and the V depletion in the mantle requires accretion from planetesimals as reduced as the enstatite chondrites. Third, experimental studies of K partitioning between silicate and metal plus sulfide show that more K goes into the metal plus sulfide at higher pressures than at one atmosphere pressure. Thus partitioning in the relatively low pressure natural laboratory of the APB is a good guide to alkali elemental partitioning during the growth of the Earth.

  20. Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

    SciTech Connect

    Zhivun, Elena; Wickenbrock, Arne; Patton, Brian; Budker, Dmitry

    2014-11-10

    We demonstrate an all-optical {sup 133}Cs scalar magnetometer, operating in nonzero magnetic field, in which the magnetic resonance is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. We achieve a projected shot-noise-limited sensitivity of 1.7fT/√(Hz) and measure a technical noise floor of 40fT/√(Hz). These results are essentially identical to a coil-driven scalar magnetometer using the same setup. This all-optical scheme offers advantages over traditional coil-driven magnetometers for use in arrays and in magnetically sensitive fundamental physics experiments, e.g., searches for a permanent electric dipole moment of the neutron.

  1. Optically pumped alkali laser and amplifier using helium-3 buffer gas

    DOEpatents

    Beach, Raymond J.; Page, Ralph; Soules, Thomas; Stappaerts, Eddy; Wu, Sheldon Shao Quan

    2010-09-28

    In one embodiment, a laser oscillator is provided comprising an optical cavity, the optical cavity including a gain medium including an alkali vapor and a buffer gas, the buffer gas including .sup.3He gas, wherein if .sup.4He gas is also present in the buffer gas, the ratio of the concentration of the .sup.3He gas to the .sup.4He gas is greater than 1.37.times.10.sup.-6. Additionally, an optical excitation source is provided. Furthermore, the laser oscillator is capable of outputting radiation at a first frequency. In another embodiment, an apparatus is provided comprising a gain medium including an alkali vapor and a buffer gas including .sup.3He gas, wherein if .sup.4He gas is also present in the buffer gas, the ratio of the concentration of the .sup.3He gas to the .sup.4He gas is greater than 1.37.times.10.sup.-6. Other embodiments are also disclosed.

  2. 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)

  3. 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.

  4. Copper vapor laser acoustic thermometry system

    DOEpatents

    Galkowski, Joseph J.

    1987-01-01

    A copper vapor laser (CVL) acoustic thermometry system is disclosed. The invention couples an acoustic pulse a predetermined distance into a laser tube by means of a transducer and an alumina rod such that an echo pulse is returned along the alumina rod to the point of entry. The time differential between the point of entry of the acoustic pulse into the laser tube and the exit of the echo pulse is related to the temperature at the predetermined distance within the laser tube. This information is processed and can provide an accurate indication of the average temperature within the laser tube.

  5. Sub-Shot-Noise Magnetometry with a Correlated Spin-Relaxation Dominated Alkali-Metal Vapor

    SciTech Connect

    Kominis, I. K.

    2008-02-22

    Spin noise sets fundamental limits to the precision of measurements using spin-polarized atomic vapors, such as performed with sensitive atomic magnetometers. Spin squeezing offers the possibility to extend the measurement precision beyond the standard quantum limit of uncorrelated atoms. Contrary to current understanding, we show that, even in the presence of spin relaxation, spin squeezing can lead to a significant reduction of spin noise, and hence an increase in magnetometric sensitivity, for a long measurement time. This is the case when correlated spin relaxation due to binary alkali-atom collisions dominates independently acting decoherence processes, a situation realized in thermal high atom-density magnetometers and clocks.

  6. Diffusion with chemical reaction: An attempt to explain number density anomalies in experiments involving alkali vapor

    NASA Technical Reports Server (NTRS)

    Snow, W. L.

    1974-01-01

    The mutual diffusion of two reacting gases is examined which takes place in a bath of inert gas atoms. Solutions are obtained between concentric spheres, each sphere acting as a source for one of the reactants. The calculational model is used to illustrate severe number density gradients observed in absorption experiments with alkali vapor. Severe gradients result when sq root k/D R is approximately 5 where k, D, and R are respectively the second order rate constant, the multicomponent diffusion constant, and the geometrical dimension of the experiment.

  7. Reviews of a Diode-Pumped Alkali Laser (DPAL): a potential high powered light source

    NASA Astrophysics Data System (ADS)

    Cai, He; Wang, You; Han, Juhong; An, Guofei; Zhang, Wei; Xue, Liangping; Wang, Hongyuan; Zhou, Jie; Gao, Ming; Jiang, Zhigang

    2015-03-01

    Diode pumped alkali vapor lasers (DPALs) were first developed by in W. F. Krupke at the beginning of the 21th century. In the recent years, DPALs have been rapidly developed because of their high Stokes efficiency, good beam quality, compact size and near-infrared emission wavelengths. The Stokes efficiency of a DPAL can achieve a miraculous level as high as 95.3% for cesium (Cs), 98.1% for rubidium (Rb), and 99.6% for potassium (K), respectively. The thermal effect of a DPAL is theoretically smaller than that of a normal diode-pumped solid-state laser (DPSSL). Additionally, generated heat of a DPAL can be removed by circulating the gases inside a sealed system. Therefore, the thermal management would be relatively simple for realization of a high-powered DPAL. In the meantime, DPALs combine the advantages of both DPSSLs and normal gas lasers but evade the disadvantages of them. Generally, the collisionally broadened cross sections of both the D1 and the D2 lines for a DPAL are much larger than those for the most conventional solid-state, fiber and gas lasers. Thus, DPALs provide an outstanding potentiality for realization of high-powered laser systems. It has been shown that a DPAL is now becoming one of the most promising candidates for simultaneously achieving good beam quality and high output power. With a lot of marvelous merits, a DPAL becomes one of the most hopeful high-powered laser sources of next generation.

  8. Spin-exchange frequency shift in alkali-metal-vapor cell frequency standards

    SciTech Connect

    Micalizio, Salvatore; Godone, Aldo; Levi, Filippo; Vanier, Jacques

    2006-03-15

    In this paper we calculate the effect of spin-exchange collisions in alkali-metal vapors. In the framework of the high-energy approximation, we evaluate the spin-exchange cross sections related to the line broadening and to the frequency shift of the ground state hyperfine transition. We do the calculation for the four isotopes, {sup 23}Na, {sup 39}K, {sup 87}Rb, and {sup 133}Cs. The results are used in particular to evaluate the spin-exchange frequency shift in Rb vapor cell frequency standards used in many applications. It turns out that, due to possible fluctuations in the atomic density, spin exchange may affect significantly the medium and long term frequency stability of the frequency standard.

  9. Supersonic diode pumped alkali lasers: Computational fluid dynamics modeling

    NASA Astrophysics Data System (ADS)

    Rosenwaks, Salman; Yacoby, Eyal; Waichman, Karol; Sadot, Oren; Barmashenko, Boris D.

    2015-10-01

    We report on recent progress on our three-dimensional computational fluid dynamics (3D CFD) modeling of supersonic diode pumped alkali lasers (DPALs), taking into account fluid dynamics and kinetic processes in the lasing medium. For a supersonic Cs DPAL with laser section geometry and resonator parameters similar to those of the 1-kW flowing-gas subsonic Cs DPAL [A.V. Bogachev et al., Quantum Electron. 42, 95 (2012)] the maximum achievable output power, ~ 7 kW, is 25% higher than that achievable in the subsonic case. Comparison between semi-analytical and 3D CFD models for Cs shows that the latter predicts much higher maximum achievable output power than the former. Optimization of the laser parameters using 3D CFD modeling shows that very high power and optical-to-optical efficiency, 35 kW and 82%, respectively, can be achieved in a Cs supersonic device pumped by a collimated cylindrical (0.5 cm diameter) beam. Application of end- or transverse-pumping by collimated rectangular (large cross section ~ 2 - 4 cm2) beam makes it possible to obtain even higher output power, > 250 kW, for ~ 350 kW pumping power. The main processes limiting the power of Cs supersonic DPAL are saturation of the D2 transition and large ~ 40% losses of alkali atoms due to ionization, whereas the influence of gas heating is negligibly small. For supersonic K DPAL both gas heating and ionization effects are shown to be unimportant and the maximum achievable power, ~ 40 kW and 350 kW, for pumping by ~ 100 kW cylindrical and ~ 700 kW rectangular beam, respectively, are higher than those achievable in the Cs supersonic laser. The power achieved in the supersonic K DPAL is two times higher than for the subsonic version with the same resonator and K density at the gas inlet, the maximum optical-to-optical efficiency being 82%.

  10. Metal vapor lasers with increased reliability

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Sabotinov, N. V.; Polunin, Yu. P.; Shumeiko, A. S.; Kostadinov, I. K.; Vasilieva, A. V.; Reimer, I. V.

    2015-12-01

    Results of investigation and development of an excitation pulse generator with magnetic pulse compression by saturation chokes for pumping of active media of CuBr, Sr, and Ca vapor lasers are presented. A high-power IGBT transistor is used as a commutator. The generator can operate at excitation pulse repetition frequencies up to 20 kHz. The total average power for all laser lines of the CuBr laser pumped by this generator is ~6.0 W; it is ~1.3-1.7 W for the Sr and Ca lasers.

  11. Absorption of solar radiation by alkali vapors. [for efficient high temperature energy converters

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.

    1978-01-01

    A theoretical study of the direct absorption of solar radiation by the working fluid of high temperature, high efficiency energy converters has been carried out. Alkali vapors and potassium vapor in particular were found to be very effective solar absorbers and suitable thermodynamically for practical high temperature cycles. Energy loss via reradiation from a solar boiler was shown to reduce the overall efficiency of radiation-heated energy converters, although a simple model of radiation transfer in a potassium vapor solar boiler revealed that self-trapping of the reradiation may reduce this loss considerably. A study was also made of the requirements for a radiation boiler window. It was found that for sapphire, one of the best solar transmitting materials, the severe environment in conjunction with high radiation densities will require some form of window protection. An aerodynamic shield is particularly advantageous in this capacity, separating the window from the absorbing vapor to prevent condensation and window corrosion and to reduce the radiation density at the window.

  12. New Medical Applications Of Metal Vapor Lasers

    NASA Astrophysics Data System (ADS)

    Anderson, Robert S.; McIntosh, Alexander I.

    1989-06-01

    The first medical application for metal vapor lasers has been granted marketing approval by the FDA. This represents a major milestone for this technology. Metalaser Technologies recently received this approval for its Vasculase unit in the treatment of vascular lesions such as port wine stains, facial telangiectasia and strawberry hemangiomas.

  13. Laser cooling of nuclear spin 0 alkali 78Rb

    NASA Astrophysics Data System (ADS)

    Behr, J. A.; Gorelov, A.; Anholm, M.

    2015-05-01

    The textbook example for sub-Doppler cooling is a J = 1/2 I = 0 alkali atom in lin ⊥ lin molasses. In the σ+ σ- configuration of a standard MOT, the main sub-Doppler cooling mechanism relies on changing alignment (MF2 population) with the summed linear polarization orientation, but there is no such variation in AC Stark shift for F = 1/2. We have nevertheless looked for signs of sub-Doppler cooling by trapping I = 0 78Rb in a standard MOT and measuring the cloud size as a function of laser detuning and intensity. The 78Rb cloud size does not change significantly with lowered intensity, and expands slightly with detuning, consistent with minimal to no sub-Doppler cooling. Our geometry does show the well-known substantially smaller cloud size with detuning and intensity for I = 3/2 87Rb. Maintaining an I = 0 alkali cloud size with lowered intensity will help our planned β- ν correlation experiments in 38mK decay by suppressing possible production of photoassisted dimers. Supported by NSERC and NRC Canada through TRIUMF.

  14. Alkali--rare gas photodissociation lasers: Applications to laser physics and atom-atom interactions

    NASA Astrophysics Data System (ADS)

    Hewitt, John Darby

    This dissertation describes several experiments in which alkali--rare gas laser systems are utilized as a simple platform with which to isolate and study atom-atom interactions and fundamental physical processes that are ill-understood or have never been investigated previously. Specifically, the minimum allowable energy separation between levels 2 and 3 in a three-level laser system has been investigated experimentally, as have two-photon absorption processes in atomic Rb and Cs.

  15. Investigation of anti-Relaxation coatings for alkali-metal vapor cells using surface science techniques

    SciTech Connect

    Seltzer, S. J.; Michalak, D. J.; Donaldson, M. H.; Balabas, M. V.; Barber, S. K.; Bernasek, S. L.; Bouchiat, M.-A.; Hexemer, A.; Hibberd, A. M.; Jackson Kimball, D. F.; Jaye, C.; Karaulanov, T.; Narducci, F. A.; Rangwala, S. A.; Robinson, H. G.; Shmakov, A. K.; Voronov, D. L.; Yashchuk, V. V.; Pines, A.; Budker, D.

    2010-10-11

    Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10?000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C=C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials.

  16. A fixed granular-bed sorber for measurement and control of alkali vapors in PFBC (pressurized fluidized-bed combustion)

    SciTech Connect

    Lee, S.H.D.; Swift, W.M.

    1990-01-01

    Alkali vapors (Na and K) in the hot flue gas from the pressurized fluidized-bed combustion (PFBC) of coal could cause corrosion problems with the gas turbine blades. In a laboratory-scale PFBC test with Beulah lignite, a fixed granular bed of activated bauxite sorbent was used to demonstrate its capability for measuring and controlling alkali vapors in the PFBC flue gas. The Beulah lignite was combusted in a bed of Tymochtee dolomite at bed temperatures ranging from 850 to 875{degrees}C and a system pressure of 9.2 atm absolute. The time-averaged concentration of sodium vapor in the PFBC flue gas was determined from the analysis of two identical beds of activated bauxite and found to be 1.42 and 1.50 ppmW. The potassium vapor concentration was determined to be 0.10 ppmW. The sodium material balance showed that only 0.24% of the total sodium in the lignite was released as vapor species in the PFBC flue gas. This results in an average of 1.56 ppmW alkali vapors in the PFBC flue gas. This average is more than 1.5 orders of magnitude greater than the currently suggested alkali specification limit of 0.024 ppm for an industrial gas turbine. The adsorption data obtained with the activated bauxite beds were also analyzed mathematically by use of a LUB (length of unused bed)/equilibrium section concept. Analytical results showed that the length of the bed, L{sub o} in centimeters, relates to the break through time, {theta}{sub b} in hours, for the alkali vapor to break through the bed as follows: L{sub o} = 33.02 + 1.99 {theta}{sub b}. This formula provides useful information for the engineering design of fixed-bed activated bauxite sorbers for the measurement and control of alkali vapors in PFBC flue gas. 26 refs., 4 figs., 4 tabs.

  17. Precision micro drilling with copper vapor lasers

    SciTech Connect

    Chang, J.J.; Martinez, M.W.; Warner, B.E.; Dragon, E.P.; Huete, G.; Solarski, M.E.

    1994-09-02

    The authors have developed a copper vapor laser based micro machining system using advanced beam quality control and precision wavefront tilting technologies. Micro drilling has been demonstrated through percussion drilling and trepanning using this system. With a 30 W copper vapor laser running at multi-kHz pulse repetition frequency, straight parallel holes with size varying from 500 microns to less than 25 microns and with aspect ratio up to 1:40 have been consistently drilled on a variety of metals with good quality. For precision trepanned holes, the hole-to-hole size variation is typically within 1% of its diameter. Hole entrance and exit are both well defined with dimension error less than a few microns. Materialography of sectioned holes shows little (sub-micron scale) recast layer and heat affected zone with surface roughness within 1--2 microns.

  18. Copper vapor laser prospects in glaucoma treatment

    NASA Astrophysics Data System (ADS)

    Egorov, E. A.; Nesterov, Arcady P.; Novoderezhkin, Vladimir I.; Egorov, Alexey E.; Shaban, Naim; Ponomarev, Igor V.

    1996-05-01

    New advances of copper vapor laser (CVL-laser) have been studied. Two wavelength radiation of the laser (511 nm and 578 nm) gives deeper permeability into organic tissues. Besides, the short pulse prevents the warm relaxation of small vessels. The technical data of CVL-laser: operating regime -- pulse, pulse duration -- 20 ns, pulse frequency 15000 pulse/sec. The shutter works in intervals from 0.05 to 2.0 sec. The power varies in accordance with wavelength: 511 nm (green) -- 1.5 W, 578 nm (yellow) -- 1, 2 W. The diameter of coagulate may be different: 100, 150, 400, 1000 mkm. We chose CVL-laser 'Femta,' created by P. N. Lebedev Physical Institute of RAS, for ophthalmological use. Thirty eight eyes of 37 patients with different types and stages of glaucoma were studied and treated with CVL-laser. The operations of photomydriasis, gonioplasty and trabeculoplasty have been performed. CVL- laser demonstrated efficient application in treatment of interior eye segment of glaucoma patients. The advantages and disadvantages of the CVL-laser application in glaucoma surgery were discussed.

  19. Injection locked oscillator system for pulsed metal vapor lasers

    DOEpatents

    Warner, Bruce E.; Ault, Earl R.

    1988-01-01

    An injection locked oscillator system for pulsed metal vapor lasers is disclosed. The invention includes the combination of a seeding oscillator with an injection locked oscillator (ILO) for improving the quality, particularly the intensity, of an output laser beam pulse. The present invention includes means for matching the first seeder laser pulses from the seeding oscillator to second laser pulses of a metal vapor laser to improve the quality, and particularly the intensity, of the output laser beam pulse.

  20. Metal vapor laser including hot electrodes and integral wick

    DOEpatents

    Ault, E.R.; Alger, T.W.

    1995-03-07

    A metal vapor laser, specifically one utilizing copper vapor, is disclosed herein. This laser utilizes a plasma tube assembly including a thermally insulated plasma tube containing a specific metal, e.g., copper, and a buffer gas therein. The laser also utilizes means including hot electrodes located at opposite ends of the plasma tube for electrically exciting the metal vapor and heating its interior to a sufficiently high temperature to cause the metal contained therein to vaporize and for subjecting the vapor to an electrical discharge excitation in order to lase. The laser also utilizes external wicking arrangements, that is, wicking arrangements located outside the plasma tube. 5 figs.

  1. Metal vapor laser including hot electrodes and integral wick

    DOEpatents

    Ault, Earl R.; Alger, Terry W.

    1995-01-01

    A metal vapor laser, specifically one utilizing copper vapor, is disclosed herein. This laser utilizes a plasma tube assembly including a thermally insulated plasma tube containing a specific metal, e.g., copper, and a buffer gas therein. The laser also utilizes means including hot electrodes located at opposite ends of the plasma tube for electrically exciting the metal vapor and heating its interior to a sufficiently high temperature to cause the metal contained therein to vaporize and for subjecting the vapor to an electrical discharge excitation in order to lase. The laser also utilizes external wicking arrangements, that is, wicking arrangements located outside the plasma tube.

  2. Controlling Metal-Halide Vapor Density in Lasers

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.

    1984-01-01

    Streams of buffer gas convect and dilute metal-halide vapor. Technique uses flow of buffer gas through reservoir, which contains heated metal halide, to convect vapors into discharge tube. Second stream of buffer gas dilutes vapor. Final vapor density in laser tube controlled and changed by adjusting either one or both of buffer gas flow rates.

  3. Laser demonstration and performance characterization of optically pumped Alkali Laser systems

    NASA Astrophysics Data System (ADS)

    Sulham, Clifford V.

    Diode Pumped Alkali Lasers (DPALs) offer a promising approach for high power lasers in military applications that will not suffer from the long logistical trails of chemical lasers or the thermal management issues of diode pumped solid state lasers. This research focuses on characterizing a DPAL-type system to gain a better understanding of using this type of laser as a directed energy weapon. A rubidium laser operating at 795 nm is optically pumped by a pulsed titanium sapphire laser to investigate the dynamics of DPALs at pump intensities between 1.3 and 45 kW/cm2. Linear scaling as high as 32 times threshold is observed, with no evidence of second order kinetics. Comparison of laser characteristics with a quasi-two level analytic model suggests performance near the ideal steady-state limit, disregarding the mode mis-match. Additionally, the peak power scales linearly as high as 1 kW, suggesting aperture scaling to a few cm2 is sufficient to achieve tactical level laser powers. The temporal dynamics of the 100 ns pump and rubidium laser pulses are presented, and the continually evolving laser efficiency provides insight into the bottlenecking of the rubidium atoms in the 2P3/2 state. Lastly, multiple excited states of rubidium and cesium were accessed through two photon absorption in the red, yielding a blue and an IR photon through amplified stimulated emission. Threshold is modest at 0.3 mJ/pulse, and slope efficiencies increase dramatically with alkali concentrations and peak at 0.4%, with considerable opportunity for improvement. This versatile system might find applications for IR countermeasures or underwater communications.

  4. Continuous wave Cs diode pumped alkali laser pumped by single emitter narrowband laser diode.

    PubMed

    Zhdanov, B V; Venus, G; Smirnov, V; Glebov, L; Knize, R J

    2015-08-01

    This paper presents results of cooperative efforts on development of a continuous wave Cs diode pumped alkali laser with moderate output power, which can be considered as a prototype of the commercial device. The developed system operates at 895 nm with output power about 4 W and slope efficiency 28%. Measured turn on time of this system from the standby mode is about a minute. PMID:26329171

  5. Tunable lasers for water vapor measurements and other lidar applications

    NASA Technical Reports Server (NTRS)

    Gammon, R. W.; Mcilrath, T. J.; Wilkerson, T. D.

    1977-01-01

    A tunable dye laser suitable for differential absorption (DIAL) measurements of water vapor in the troposphere was constructed. A multi-pass absorption cell for calibration was also constructed for use in atmospheric DIAL measurements of water vapor.

  6. Laboratory studies of the deposition of alkali sulfate vapors from combustion gases using a flash-evaporation technique

    NASA Technical Reports Server (NTRS)

    Rosner, Daniel E.; Liang, Baishen

    1986-01-01

    A relatively simple experimental technique is proposed and demonstrated for making measurements of absolute dewpoints and relative deposition rates from flowing combustion gases containing condensible inorganic vapors. The method involves first accumulating condensate on a Pt ribbon target maintained below the dewpoint and then flash-evaporating the condensate into the filament wake, where its alkali content is monitored by alkali-atom emission spectroscopy. The advantages of the method over others are demonstrated; in particular, the method can detect liquid condensate inventories which are small enough to be negligibly influenced by surface runoff produced by gas-side shear stress and liquid condensate surface tension gradients. Illustrative Na2SO4 and K2SO4 deposition rate data and corresponding dewpoint data obtained in a series of alkali-seeded propane/air atmospheric flames are presented and discussed.

  7. Alkali metal vapor removal from pressurized fluidized-bed combustor flue gas. Quarterly report, April-June 1980

    SciTech Connect

    Johnson, I.; Swift, W.M.; Lee, S.H.D.; Boyd, W.A.

    1980-07-01

    In the application of pressurized fluidized-bed combustors (PFBC) to the generation of electricity, hot corrosion of gas turbine components by alkali metal compounds is a potential problem. The objective of this investigation is to develop a method for removing these gaseous alkali metal compounds from the high-pressure high-temperature gas from a PFBC before the gas enters the gas turbine. A granular-bed filter, using either diatomaceous earth or activated bauxite as the bed material, is the concept currently being studied. Results are presented for the testing of diatomaceous earth for alkali vapor sorption at 800/sup 0/C and 9-atm pressure, using a simulated flue gas. Activated bauxite sorbent can be regenerated by leaching with water, and the kinetics of the leaching is under study.

  8. Effects of spin-exchange collisions in a high-density alkali-metal vapor in low magnetic fields

    SciTech Connect

    Savukov, I.M.; Romalis, M.V.

    2005-02-01

    Spin-exchange collisions often play a dominant role in the broadening of Zeeman resonances in an alkali-metal vapor. Contrary to intuitive expectations, at high alkali-metal densities this broadening can be completely eliminated by operating in a low magnetic field, allowing construction of ultrasensitive atomic magnetometers. We describe a detailed study of the Zeeman resonance frequencies and linewidths as a function of the magnetic field, alkali-metal density, and the degree of spin polarization of the atoms. Due to the nonlinear nature of the density matrix equations describing the spin-exchange collisions both the gyromagnetic ratio and the linewidth change as a function of the polarization. The results of experimental measurements are in excellent agreement with analytical and numerical solutions of the density matrix equations.

  9. Widefield microwave imaging in alkali vapor cells with sub-100 μm resolution

    NASA Astrophysics Data System (ADS)

    Horsley, Andrew; Du, Guan-Xiang; Treutlein, Philipp

    2015-11-01

    We report on widefield microwave vector field imaging with sub-100 μ {{m}} resolution using a microfabricated alkali vapor cell. The setup can additionally image dc magnetic fields, and can be configured to image microwave electric fields. Our camera-based widefield imaging system records 2D images with a 6 × 6 mm2 field of view at a rate of 10 Hz. It provides up to 50 μ {{m}} spatial resolution, and allows imaging of fields as close as 150 μ {{m}} above structures, through the use of thin external cell walls. This is crucial in allowing us to take practical advantage of the high spatial resolution, as feature sizes in near-fields are on the order of the distance from their source, and represent an order of magnitude improvement in surface-feature resolution compared to previous vapor cell experiments. We present microwave and dc magnetic field images above a selection of devices, demonstrating a microwave sensitivity of 1.4 μ {{T}} {{Hz}}-1/2 per 50× 50× 140 μ {{{m}}}3 voxel, at present limited by the speed of our camera system. Since we image 120 × 120 voxels in parallel, a single scanned sensor would require a sensitivity of at least 12 {nT} {{Hz}}-1/2 to produce images with the same sensitivity. Our technique could prove transformative in the design, characterization, and debugging of microwave devices, as there are currently no satisfactory established microwave imaging techniques. Moreover, it could find applications in medical imaging.

  10. Effects of atmospheric transmission of high power diode pumped alkali lasers

    NASA Astrophysics Data System (ADS)

    Rice, Christopher A.; Perram, Glen P.

    2013-03-01

    As diode pumped alkali lasers (DPAL) are scaled to powers exceeding 1 kW, the effects of atmospheric transmission, including thermal blooming, is explored. The cesium and rubidium lasers operate near 894 and 795 nm, respectively, in the vicinity of atmospheric water vapor absorption lines. The potassium laser line lies in the high rotational limit of the O2 X-b (0,0) band near 770 nm. We assess the effects of atmospheric transmission on high power propagation using the High Energy Laser End-to End Operational Simulation. HELEEOS uses the scaling laws of the Scaling the High energy laser And Relay Engagements (SHaRE) toolbox which is anchored to the wave optics code WaveTrain and all significant degradation effects, including thermal blooming due to molecular and aerosol absorption, scattering extinction, and optical turbulence, are represented in the model. The HELEEOS model enables the evaluation of uncertainty in low-altitude high energy laser engagements due to all major low altitude atmospheric effects to include physically-based representations of water clouds, fog, light rain, and aerosols. Worldwide seasonal, diurnal, and geographical spatial-temporal variability in key climatological parameters is organized into probability density function databases in HELEEOS using a variety of recently available resources to include the Extreme and Percentile Environmental Reference Tables (ExPERT) for 408 sites worldwide, the Surface Marine Gridded Climatology (SMGC) database which provides coverage over all ocean areas, the Master Database for Optical Turbulence Research in support of the Airborne Laser, and the Global Aerosol Data Set (GADS) used to provide worldwide aerosol densities. The spectral transmission model is anchored to field data from an open-path Tunable Diode Laser Absorption (TDLAS) system composed of narrow band (~300 kHz) diode laser fiber coupled to a 12" Ritchey-Chrétien transmit telescope. The ruggedized system has been field deployed and tested

  11. Low-temperature indium-bonded alkali vapor cell for chip-scale atomic clocks

    NASA Astrophysics Data System (ADS)

    Straessle, R.; Pellaton, M.; Affolderbach, C.; Pétremand, Y.; Briand, D.; Mileti, G.; de Rooij, N. F.

    2013-02-01

    A low-temperature sealing technique for micro-fabricated alkali vapor cells for chip-scale atomic clock applications is developed and evaluated. A thin-film indium bonding technique was used for sealing the cells at temperatures of ≤140 °C. These sealing temperatures are much lower than those reported for other approaches, and make the technique highly interesting for future micro-fabricated cells, using anti-relaxation wall coatings. Optical and microwave spectroscopy performed on first indium-bonded cells without wall coatings are used to evaluate the cleanliness of the process as well as a potential leak rate of the cells. Both measurements confirm a stable pressure inside the cell and therefore an excellent hermeticity of the indium bonding. The double-resonance measurements performed over several months show an upper limit for the leak rate of 1.5 × 10-13 mbar.l/s. This is in agreement with additional leak-rate measurements using a membrane deflection method on indium-bonded test structures.

  12. Development of standardized air-blown coal gasifier/gas turbine concepts for future electric power systems. Volume 3, Appendix B: NO{sub x} and alkali vapor control strategies: Final report

    SciTech Connect

    Not Available

    1990-07-01

    CRS Sirrine (CRSS) is evaluating a novel IGCC process in which gases exiting the gasifier are burned in a gas turbine combustion system. The turbine exhaust gas is used to generate additional power in a conventional steam generator. This results in a significant increase in efficiency. However, the IGCC process requires development of novel approaches to control SO{sub 2} and NO{sub x} emissions and alkali vapors which can damage downstream turbine components. Ammonia is produced from the reaction of coal-bound nitrogen with steam in the reducing zone of any fixed bed coal gasifier. This ammonia can be partially oxidized to NO{sub x} when the product gas is oxidized in a gas turbine combustor. Alkali metals vaporize in the high-temperature combustion zone of the gasifier and laser condense on the surface of small char or ash particles or on cooled metal surfaces. It these alkali-coated materials reach the gas turbine combustor, the alkali will revaporize condense on turbine blades and cause rapid high temperature corrosion. Efficiency reduction will result. PSI Technology Company (PSIT) was contracted by CRSS to evaluate and recommend solutions for NO{sub x} emissions and for alkali metals deposition. Various methods for NO{sub x} emission control and the potential process and economic impacts were evaluated. This included estimates of process performance, heat and mass balances around the combustion and heat transfer units and a preliminary economic evaluation. The potential for alkali metal vaporization and condensation at various points in the system was also estimated. Several control processes and evaluated, including an order of magnitude cost for the control process.

  13. Application of laser Doppler velocimeter to chemical vapor laser system

    NASA Technical Reports Server (NTRS)

    Gartrell, Luther R.; Hunter, William W., Jr.; Lee, Ja H.; Fletcher, Mark T.; Tabibi, Bagher M.

    1993-01-01

    A laser Doppler velocimeter (LDV) system was used to measure iodide vapor flow fields inside two different-sized tubes. Typical velocity profiles across the laser tubes were obtained with an estimated +/-1 percent bias and +/-0.3 to 0.5 percent random uncertainty in the mean values and +/-2.5 percent random uncertainty in the turbulence-intensity values. Centerline velocities and turbulence intensities for various longitudinal locations ranged from 13 to 17.5 m/sec and 6 to 20 percent, respectively. In view of these findings, the effects of turbulence should be considered for flow field modeling. The LDV system provided calibration data for pressure and mass flow systems used routinely to monitor the research laser gas flow velocity.

  14. Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating

    NASA Astrophysics Data System (ADS)

    Tretiak, O. Yu.; Blanchard, J. W.; Budker, D.; Olshin, P. K.; Smirnov, S. N.; Balabas, M. V.

    2016-03-01

    The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements compared to a bare glass surface by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene.

  15. Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating.

    PubMed

    Tretiak, O Yu; Blanchard, J W; Budker, D; Olshin, P K; Smirnov, S N; Balabas, M V

    2016-03-01

    The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements compared to a bare glass surface by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene. PMID:26957176

  16. Theoretical simulations of protective thin film Fabry-Pérot filters for integrated optical elements of diode pumped alkali lasers (DPAL)

    SciTech Connect

    Quarrie, L. E-mail: lindsay.o.quarrie@gmail.com

    2014-09-15

    The lifetime of Diode-Pumped Alkali Lasers (DPALs) is limited by damage initiated by reaction of the glass envelope of its gain medium with rubidium vapor. Rubidium is absorbed into the glass and the rubidium cations diffuse through the glass structure, breaking bridging Si-O bonds. A damage-resistant thin film was developed enhancing high-optical transmission at natural rubidium resonance input and output laser beam wavelengths of 780 nm and 795 nm, while protecting the optical windows of the gain cell in a DPAL. The methodology developed here can be readily modified for simulation of expected transmission performance at input pump and output laser wavelengths using different combination of thin film materials in a DPAL. High coupling efficiency of the light through the gas cell was accomplished by matching the air-glass and glass-gas interfaces at the appropriate wavelengths using a dielectric stack of high and low index of refraction materials selected to work at the laser energies and protected from the alkali metal vapor in the gain cell. Thin films as oxides of aluminum, zirconium, tantalum, and silicon were selected allowing the creation of Fabry-Perot optical filters on the optical windows achieving close to 100% laser transmission in a solid optic combination of window and highly reflective mirror. This approach allows for the development of a new whole solid optic laser.

  17. Laser beam interactions with vapor plumes during Nd:YAG laser welding on aluminum

    NASA Astrophysics Data System (ADS)

    Peebles, H. C.; Russo, A. J.; Hadley, G. R.; Akau, R. L.

    Welds produced on pure aluminum targets using pulsed Nd:YAG lasers can be accurately described using a relatively simple conduction mode heat transfer model provided that the fraction of laser energy absorbed is known and the amount of metal vaporized is smalled however at laser fluences commonly used in many production welding schedules significant aluminum vaporization does occur. The possible mechanisms have been identified which could result in laser beam attenuation by the vapor plume.

  18. PRR performance of Cu- and CuBr-vapor lasers

    NASA Astrophysics Data System (ADS)

    Fedorov, V. F.; Evtushenko, Gennadiy S.; Klimkin, Vladimir M.; Polunin, Yu. P.; Soldatov, Anatoly N.; Sukhanov, Viktor B.

    1998-06-01

    Results obtained from comparative analysis of the pulse repetition rate performance of Cu- and CuBr-vapor lasers operated at high pump pulse repetitions (approximately 100 kHz) are reported. For a CuBr laser with a 8 mm diameter discharge tube the laser pulse repetition rate as high as 270 kHz was realized.

  19. Laser Prostatectomy: Holmium Laser Enucleation and Photoselective Laser Vaporization of the Prostate

    PubMed Central

    Bostanci, Yakup; Kazzazi, Amir; Djavan, Bob

    2013-01-01

    Historically, transurethral resection of the prostate has been the gold standard for the treatment of benign prostatic hyperplasia (BPH). Laser technology has been used to treat BPH for > 15 years. Over the past decade, it has gained wide acceptance by experienced urologists. This review provides an evidence-based update on laser surgery for BPH with a focus on photoselective laser vaporization and holmium laser enucleation of the prostate surgeries and assesses the safety, efficacy, and durability of these techniques. PMID:23671400

  20. Analysis of organic vapors with laser induced breakdown spectroscopy

    SciTech Connect

    Nozari, Hadi; Tavassoli, Seyed Hassan; Rezaei, Fatemeh

    2015-09-15

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  1. Analysis of organic vapors with laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Nozari, Hadi; Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2015-09-01

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  2. Testing of candidate materials for their resistance to alkali-vapor adsorption in PFBC and gasification environments. Final report

    SciTech Connect

    Lee, S.H.D.; Natesan, K.; Swift, W.M.

    1995-08-01

    Laboratory-scale studies were performed to identify metallic material(s) having no, or limited, affinity for alkali vapors in an environment of either the off-gas from pressurized fluidized-bed combustion (PFBC) or the fuel gas from coal gasification. Such materials would be potential candidates for use as components in advanced coal-utilization systems. The following materials were tested for adsorption of NaCl vapor at 870--875 C and atmospheric pressure in a simulated PFBC off-gas (oxidizing) doped with 80 ppmW NaCl vapor: iron-based Type 304 stainless steel (304 SS), nickel-based Hastelloy C-276 and Hastelloy X alloys, cobalt-based Haynes No. 188 alloy, noble-metal-coated 304 SS, aluminized 304 SS, and ZrO{sub 2}-coated 304 SS. The Haynes No. 188 alloy and the aluminized 304 SS were also tested for their NaCl-vapor adsorption in a simulated gasification fuel gas (reducing) under the same test conditions as in the PFBC off-gas test. After 100 h of testing, the specimens were analyzed with a SEM equipped with an energy dispersive X-ray analyzer, and by an AES. The aluminized 304 SS had the least tendency to adsorb NaCl vapor, as well as an excellent resistance to corrosion as a result of the formation of a protective layer of Al{sub 2}O{sub 3} on its surface. In the reducing environment, however, the aluminized 304 SS was badly corroded by H{sub 2}S attack. The Haynes No. 188 showed virtually no NaCl-vapor adsorption and only limited H{sub 2}S attack. The authors recommend further long-term parametric studies to quantitate alkali-vapor adsorption as a function of operating variables for (1) the aluminized 304 SS in the PFBC off-gas environment and (2) the Haynes No. 188 in the gasification fuel gas environment.

  3. Computer simulated rate processes in copper vapor lasers

    NASA Technical Reports Server (NTRS)

    Harstad, K. C.

    1980-01-01

    A computer model for metal vapor lasers has been developed which places emphasis on the change of excited state populations of the lasant through inelastic collisions and radiative interaction. Also included are an energy equation for the pumping electrons and rate equations for laser photon densities. Presented are results of calculations for copper vapor with a neon buffer over a range of conditions. General agreement with experiments was obtained.

  4. New studies of optical pumping, spin resonances, and spin exchange in mixtures of inert gases and alkali-metal vapors

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu

    In this thesis, we present new studies of alkali-hyperfine resonances, new optical pumping of alkali-metal atoms, and the new measurements of binary spin-exchange cross-section between alkali-metal atoms and xenon atoms. We report a large light narrowing effect of the hyperfine end-resonance signals, which was predicted from our theory and observed in our experiments. By increasing the intensity of the circularly polarized pumping beam, alkali-metal atoms are optically pumped into a state of static polarization, and trapped into the hyperfine end-state. Spin exchange between alkali-metal atoms has minimal effect on the end-resonance of the highly spin-polarized atoms. This new result will possibly benefit the design of atomic clocks and magnetometer. We also studied the pressure dependence of the atomic-clock resonance linewidth and pointed out that the linewidth was overestimated by people in the community of atomic clock. Next, we present a series study of coherent population trapping (CPT), which is a promising technique with the same or better performance compared to the traditional microwave spectroscopy. For miniature atomic clocks, CPT method is thought to be particularly advantages. From our studies, we invented a new optical-pumping method, push-pull optical pumping, which can pump atoms into nearly pure 0-0 superposition state, the superposition state of the two ground-state hyperfine sublevels with azimuthal quantum number m = 0. We believe this new invention will bring a big advantage to CPT frequency standards, the quantum state preparation for cold atoms or hot vapor, etc. We also investigated the pressure dependence of CPT excitation and the line shape of the CPT resonance theoretically and experimentally. These two properties are important for CPT applications. A theoretical study of "photon cost" of optical pumping is also presented. Finally, we switch our attention to the problem of spin exchange between alkali-metal atoms and xenon gas. This

  5. A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium.

    PubMed

    McCarron, Daniel J; Hughes, Ifan G; Tierney, Patrick; Cornish, Simon L

    2007-09-01

    The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D(2) transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude. PMID:17902946

  6. Alexandrite laser transmitter development for airborne water vapor DIAL measurements

    NASA Technical Reports Server (NTRS)

    Chyba, Thomas H.; Ponsardin, Patrick; Higdon, Noah S.; DeYoung, Russell J.; Browell, Edward V.

    1995-01-01

    In the DIAL technique, the water vapor concentration profile is determined by analyzing the lidar backscatter signals for laser wavelengths tuned 'on' and 'off' a water vapor absorption line. Desired characteristics of the on-line transmitted laser beam include: pulse energy greater than or equal to 100 mJ, high-resolution tuning capability (uncertainty less than 0.25 pm), good spectral stability (jitter less than 0.5 pm about the mean), and high spectral purity (greater than 99 percent). The off-line laser is generally detuned less than 100 pm away from the water vapor line. Its spectral requirements are much less stringent. In our past research, we developed and demonstrated the airborne DIAL technique for water vapor measurements in the 720-nm spectral region using a system based on an alexandrite laser as the transmitter for the on-line wavelength and a Nd:YAG laser-pumped dye laser for the off-line wavelength. This off-line laser has been replaced by a second alexandrite laser. Diode lasers are used to injection seed both lasers for frequency and linewidth control. This eliminates the need for the two intracavity etalons utilized in our previous alexandrite laser and thereby greatly reduces the risk of optical damage. Consequently, the transmitted pulse energy can be substantially increased, resulting in greater measurement range, higher data density, and increased measurement precision. In this paper, we describe the diode injection seed source, the two alexandrite lasers, and the device used to line lock the on-line seed source to the water vapor absorption feature.

  7. Industrial applications of high-power copper vapor lasers

    SciTech Connect

    Warner, B.E.; Boley, C.D.; Chang, J.J.; Dragon, E.P.; Havstad, M.A.; Martinez, M.; McLean, W. II

    1995-08-01

    A growing appreciation has developed in the last several years for the copper vapor laser because of its utility in ablating difficult materials at high rates. Laser ablation at high rates shows promise for numerous industrial applications such as thin film deposition, precision hole drilling, and machining of ceramics and other refractories.

  8. Buffer-gas-induced shift and broadening of hyperfine resonances in alkali-metal vapors

    NASA Astrophysics Data System (ADS)

    Oreto, P. J.; Jau, Y.-Y.; Post, A. B.; Kuzma, N. N.; Happer, W.

    2004-04-01

    We review the shift and broadening of hyperfine resonance lines of alkali-metal atoms in buffer gases. We present a simple theory both for the shift and the broadening induced by He gas. The theory is parametrized by the scattering length of slow electrons on He atoms and by the measured hyperfine intervals and binding energies of the S states of alkali-metal atoms. The calculated shifts and their temperature dependence are in good agreement with the published experimental data. The calculated broadening is 1.6 times smaller than the recent measurements, and more than 20 times smaller than the earlier measurements. We attribute much of the linewidth in the earlier experiments to possible small temperature gradients and the resulting inhomogeneous line broadening from the temperature dependence of hyperfine frequency shift at constant buffer-gas pressure.

  9. Selective laser vaporization of polypropylene sutures and mesh

    NASA Astrophysics Data System (ADS)

    Burks, David; Rosenbury, Sarah B.; Kennelly, Michael J.; Fried, Nathaniel M.

    2012-02-01

    Complications from polypropylene mesh after surgery for female stress urinary incontinence (SUI) may require tedious surgical revision and removal of mesh materials with risk of damage to healthy adjacent tissue. This study explores selective laser vaporization of polypropylene suture/mesh materials commonly used in SUI. A compact, 7 Watt, 647-nm, red diode laser was operated with a radiant exposure of 81 J/cm2, pulse duration of 100 ms, and 1.0-mm-diameter laser spot. The 647-nm wavelength was selected because its absorption by water, hemoglobin, and other major tissue chromophores is low, while polypropylene absorption is high. Laser vaporization of ~200-μm-diameter polypropylene suture/mesh strands, in contact with fresh urinary tissue samples, ex vivo, was performed. Non-contact temperature mapping of the suture/mesh samples with a thermal camera was also conducted. Photoselective vaporization of polypropylene suture and mesh using a single laser pulse was achieved with peak temperatures of 180 and 232 °C, respectively. In control (safety) studies, direct laser irradiation of tissue alone resulted in only a 1 °C temperature increase. Selective laser vaporization of polypropylene suture/mesh materials is feasible without significant thermal damage to tissue. This technique may be useful for SUI procedures requiring surgical revision.

  10. Experimental study of the Cs diode pumped alkali laser operation with different buffer gases

    NASA Astrophysics Data System (ADS)

    Knize, Randall J.; Zhdanov, Boris V.; Rotondaro, Matthew D.; Shaffer, Michael K.

    2016-03-01

    Cs diode pumped alkali laser (DPAL) operation using ethane, methane, and mixtures of these hydrocarbons with the noble gases He and Ar as a buffer gas for spin-orbit relaxation was studied in this work. The best Cs DPAL performance in continuous wave operation with flowing gain medium was achieved using pure methane, pure ethane, or a mixture of ethane (minimum of 200 Torr) and He with a total buffer gas pressure of 300 Torr.

  11. Microprocessing with the assistance of copper vapor laser system

    NASA Astrophysics Data System (ADS)

    Azizbekian, G. A.; Grigorian, G. V.; Kazaryan, M. A.; Lyabin, N. A.; Morozova, E. A.; Pogosyan, L. A.; Tamanyan, A. G.

    2006-05-01

    Laser processing of materials always was the important field for laser applications. Copper vapor laser (CVL) system are widely used in micromechanical engineering where optical system may provide high image quality. That allows us to concentrate the energy on a small surface and to produce very tiny holes and very thin cutting edges. The possibility to use "generator-amplifier" laser system (copper vapor elements LT-5Cu and LT-30Cu) for processing material without mechanical movements was investigated. As the pumping generator was used the scheme with the current pulse duration about 80 - 100 ns and the laser pulse duration may vary up to 25 ns. In the unstable resonator scheme the special plane mirror with reflecting coating was used. With the help of this system a number of materials were processed, namely: copper, stainless steel, gold, aluminum and nonmetals: sapphire, ceramics, various rocks, plastics etc.

  12. Monitoring PVD metal vapors using laser absorption spectroscopy

    SciTech Connect

    Braun, D.G.; Anklam, T.M.; Berzins, L.V.; Hagans, K.G.

    1994-04-01

    Laser absorption spectroscopy (LAS) has been used by the Atomic Vapor Laser Isotope Separation (AVLIS) program for over 10 years to monitor the co-vaporization of uranium and iron in its separators. During that time, LAS has proven to be an accurate and reliable method to monitor both the density and composition of the vapor. It has distinct advantages over other rate monitors, in that it is completely non-obtrusive to the vaporization process and its accuracy is unaffected by the duration of the run. Additionally, the LAS diagnostic has been incorporated into a very successful process control system. LAS requires only a line of sight through the vacuum chamber, as all hardware is external to the vessel. The laser is swept in frequency through an absorption line of interest. In the process a baseline is established, and the line integrated density is determined from the absorption profile. The measurement requires no hardware calibration. Through a proper choice of the atomic transition, a wide range of elements and densities have been monitored (e.g. nickel, iron, cerium and gadolinium). A great deal of information about the vapor plume can be obtained from the measured absorption profiles. By monitoring different species at the same location, the composition of the vapor is measured in real time. By measuring the same density at different locations, the spatial profile of the vapor plume is determined. The shape of the absorption profile is used to obtain the flow speed of the vapor. Finally, all of the above information is used evaluate the total vaporization rate.

  13. Modelling of Laser-Enhanced Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Brown, R. A.

    1985-01-01

    Research is directed at development of a detailed model of mass and heat transfer and chemical reaction in the pyrolysis of silane for the growth of thin amorphous silicon substrates incorporating laser heating of the gas phase above the film. The model will be the basis for evaluation of the relative importances of the decomposition of SiH4 in the vapor phase, mass transfer of the intermediate species, e.g., SiH2, and the evolution of hydrogen gas. Plans are also underway for developing a model for homogeneous nucleation of Si in the vapor phase to model the rate limitations observed at high gas-phase temperatures and high partial pressures of silane. Work was concentrated on an almost one-dimensional model for the coupling of the CO2 laser beam for heat transfer of the vapor phase with simple kinetic models for SiH4 decomposition and subsequent absorption of Si vapor on the substrate. Mass transfer in the vapor phase is assumed to be solely by diffusion. The role of convection in the vapor phase caused by the large changes in density in and around the center of the laser beam will be analyzed to evaluate the potential of microgravity experiments for increasing the uniformity of the film and the deposition rate.

  14. Laser-induced contained-vaporization in tissue

    SciTech Connect

    Dingus, R.S.

    1992-03-01

    When a transparent liquid or solid medium is present in front of an opaque target being irradiated by an intense laser beam, then the expansion of hot vapors generated (at the interface between the medium and the target) by the irradiant heating of the target is restrained by the medium. The tamping effect of the overlying liquid or solid can cause a much larger fraction of the deposited energy to go into kinetic energy, which leads to enhanced tissue disruption, compared to when a gas or vacuum is in front of the target. Condensable vapors and high thermal conductivity in the surrounding material facilitate rapid energy transport out of the vapor, which can cause a major reduction in the tamping enhancements. This contained-vaporization process is likely important in laser-medical applications such as, for example, laser angioplasty and laser lithotripsy. The work enhancement by the process is probably advantageous for lithotripsy in providing the necessary energy to break urinary stones; however, for angioplasty, the enhancement may provide little aid in removing plaque but may cause significant damage to arterial walls. If gas could be introduced into the artery proceeding irradiation of the plaque, then the enhancements could be avoided. In summary, careful management of the tamping conditions during tissue irradiations in the clinical applications of lasers should lead to significant improvements in the overall desired outcome.

  15. Studies of the regeneration of activated bauxite used as granular sorbent for the control of alkali vapors from hot flue gas of coal combustion

    SciTech Connect

    Lee, S H.D.; Smith, S D; Swift, W M; Johnson, I

    1981-05-01

    Regeneration of activated bauxite was studied by water-leaching and thermal swing (high-temperature desorption) methods. Granular activated bauxite has been identified to be very effective when used as a filter medium (i.e., sorbent) in granular-bed filters to remove gaseous alkali metal compounds from simulated hot flue gas of PFBC. Activated bauxite that had captured alkali chloride vapors was demonstrated to be easily and effectively regenerated for reuse by a simple water-leaching method. Data were obtained on (1) the leaching rate of the adsorbed NaCl, (2) effects on the leaching rate of adsorbed NaCl loading, leaching temperature, and the amount of water, and (3) water retention in activated bauxite after leaching. Observed physical changes and particle attrition of activated bauxite as a result of regeneration are discussed. The sorption mechanisms of activated bauxite toward alkali chloride vapors are interpreted on the basis of (1) the chemical compositions of the leachates from alkali chloride-sorbed activated bauxite and (2) the desorption of adsorbed NaCl vapor from activated bauxite at high temperature.

  16. Alkali vapor pressure modulation on the 100 ms scale in a single-cell vacuum system for cold atom experiments

    SciTech Connect

    Dugrain, Vincent; Reichel, Jakob; Rosenbusch, Peter

    2014-08-15

    We describe and characterize a device for alkali vapor pressure modulation on the 100 ms timescale in a single-cell cold atom experiment. Its mechanism is based on optimized heat conduction between a current-modulated alkali dispenser and a heat sink at room temperature. We have studied both the short-term behavior during individual pulses and the long-term pressure evolution in the cell. The device combines fast trap loading and relatively long trap lifetime, enabling high repetition rates in a very simple setup. These features make it particularly suitable for portable atomic sensors.

  17. Low-pressure cesium and potassium diode pumped alkali lasers: pros and cons

    NASA Astrophysics Data System (ADS)

    Zhdanov, Boris V.; Rotondaro, Matthew D.; Shaffer, Michael K.; Knize, Randall J.

    2016-02-01

    This paper presents the results of our experiments on a comparative study of cesium and potassium diode pumped alkali lasers (DPALs) aimed to determine which of these two lasers has more potential to scale to high powers. For both lasers, we have chosen a "low-pressure DPAL approach," which uses buffer gas pressure of about 1 atm for spin-orbit mixing of the excited states of alkali atoms to provide population inversion in the gain medium. The goal of this study was to determine power-limiting effects, which affect the performance of these DPALs, and find out how these limiting effects can be mitigated. We studied the performance of both lasers in CW and pulsed modes using both static and flowing gain medium and pump with different pulse duration. We observed output power degradation in time from the initial value to the level corresponding to the CW mode of operation. As a result of this study, some essential positive and negative features of both DPALs were revealed, which should be taken into account for power-scaling experiments.

  18. Water vapor-nitrogen absorption at CO2 laser frequencies

    NASA Technical Reports Server (NTRS)

    Peterson, J. C.; Thomas, M. E.; Nordstrom, R. J.; Damon, E. K.; Long, R. K.

    1979-01-01

    The paper reports the results of a series of pressure-broadened water vapor absorption measurements at 27 CO2 laser frequencies between 935 and 1082 kaysers. Both multiple traversal cell and optoacoustic (spectrophone) techniques were utilized together with an electronically stabilized CW CO2 laser. Comparison of the results obtained by these two methods shows remarkable agreement, indicating a precision which has not been previously achieved in pressure-broadened studies of water vapor. The data of 10.59 microns substantiate the existence of the large (greater than 200) self-broadening coefficients determined in an earlier study by McCoy. In this work, the case of water vapor in N2 at a total pressure of 1 atm has been treated.

  19. A TUNABLE DIODE LASER STACK MONITOR FOR SULFURIC ACID VAPOR

    EPA Science Inventory

    A field prototype instrument for continuous in-situ monitoring of sulfuric acid vapor in industrial smoke stacks has been developed. The method of detection is dual wavelength differential absorption in the infrared. Two tunable diode lasers are locked to two specific frequencies...

  20. Modeling of static and flowing-gas diode pumped alkali lasers

    NASA Astrophysics Data System (ADS)

    Barmashenko, Boris D.; Auslender, Ilya; Yacoby, Eyal; Waichman, Karol; Sadot, Oren; Rosenwaks, Salman

    2016-03-01

    Modeling of static and flowing-gas subsonic, transonic and supersonic Cs and K Ti:Sapphire and diode pumped alkali lasers (DPALs) is reported. A simple optical model applied to the static K and Cs lasers shows good agreement between the calculated and measured dependence of the laser power on the incident pump power. The model reproduces the observed threshold pump power in K DPAL which is much higher than that predicted by standard models of the DPAL. Scaling up flowing-gas DPALs to megawatt class power is studied using accurate three-dimensional computational fluid dynamics model, taking into account the effects of temperature rise and losses of alkali atoms due to ionization. Both the maximum achievable power and laser beam quality are estimated for Cs and K lasers. The performance of subsonic and, in particular, supersonic DPALs is compared with that of transonic, where supersonic nozzle and diffuser are spared and high power mechanical pump (needed for recovery of the gas total pressure which strongly drops in the diffuser), is not required for continuous closed cycle operation. For pumping by beams of the same rectangular cross section, comparison between end-pumping and transverse-pumping shows that the output power is not affected by the pump geometry, however, the intensity of the output laser beam in the case of transverse-pumped DPALs is strongly non-uniform in the laser beam cross section resulting in higher brightness and better beam quality in the far field for the end-pumping geometry where the intensity of the output beam is uniform.

  1. Ion formation in laser-irradiated cesium vapor

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. A.; Gamal, Y. E. E.; Abd El-Rahman, H. A.

    2006-11-01

    We study theoretically the formation of Cs and Cs2+ during cw laser radiation resonant with 6s-7p transition of Cs atomic vapor. This is done by numerically solving rate equations for the evolution of atomic state and electron populations. The results of calculations for the atomic and molecular ions density at different values of laser power clarified that the associative ionization and Penning ionization process play an important role for producing the Cs2+ and Cs, respectively, during the plasma formation. Also, the results showed that laser power of the order of 150 mW and 40 50 ns irradiation time are optimal in producing a fully ionized plasma.

  2. Application of G criterion in metal vapor ion laser

    NASA Astrophysics Data System (ADS)

    Gang, Chen; Bailiang, Pan; Yi, Jin; Kun, Chen; Zhixin, Yao

    2003-09-01

    Application of G criterion to efficient operation of pulsed discharge-excited R-M transition metal vapor laser was successfully extended to univalent ionic lasing medium from neutral atomic lasing medium on the basis of analyzing the simulation results of 1.09 μm Sr + lasing process. All of the known 17 R-M transition laser lines of univalent ions follow the G criterion except one, to which an interpretation is given. Furthermore, we suggest that only 69 lines among 212 possible R-M transition laser lines predicted by S.V. Markova, which satisfy the G criterion, should be explored first.

  3. Simulation of deleterious processes in a static-cell diode pumped alkali laser

    NASA Astrophysics Data System (ADS)

    Oliker, Benjamin Q.; Haiducek, John D.; Hostutler, David A.; Pitz, Greg A.; Rudolph, Wolfgang; Madden, Timothy J.

    2014-02-01

    The complex interactions in a diode pumped alkali laser (DPAL) gain cell provide opportunities for multiple deleterious processes to occur. Effects that may be attributable to deleterious processes have been observed experimentally in a cesium static-cell DPAL at the United States Air Force Academy [B.V. Zhdanov, J. Sell, R.J. Knize, "Multiple laser diode array pumped Cs laser with 48 W output power," Electronics Letters, 44, 9 (2008)]. The power output in the experiment was seen to go through a "roll-over"; the maximum power output was obtained with about 70 W of pump power, then power output decreased as the pump power was increased beyond this point. Research to determine the deleterious processes that caused this result has been done at the Air Force Research Laboratory utilizing physically detailed simulation. The simulations utilized coupled computational fluid dynamics (CFD) and optics solvers, which were three-dimensional and time-dependent. The CFD code used a cell-centered, conservative, finite-volume discretization of the integral form of the Navier-Stokes equations. It included thermal energy transport and mass conservation, which accounted for chemical reactions and state kinetics. Optical models included pumping, lasing, and fluorescence. The deleterious effects investigated were: alkali number density decrease in high temperature regions, convective flow, pressure broadening and shifting of the absorption lineshape including hyperfine structure, radiative decay, quenching, energy pooling, off-resonant absorption, Penning ionization, photoionization, radiative recombination, three-body recombination due to free electron and buffer gas collisions, ambipolar diffusion, thermal aberration, dissociative recombination, multi-photon ionization, alkali-hydrocarbon reactions, and electron impact ionization.

  4. Hybrid Optical Pumping of Optically Dense Alkali-Metal Vapor without Quenching Gas

    SciTech Connect

    Romalis, M. V.

    2010-12-10

    Optical pumping of an optically thick atomic vapor typically requires a quenching buffer gas, such as N{sub 2}, to prevent radiation trapping of unpolarized photons which would depolarize the atoms. We show that optical pumping of a trace contamination of Rb present in K metal results in a 4.5 times higher polarization of K than direct optical pumping of K in the absence of N{sub 2}. Such spin-exchange polarization transfer from optically thin species is useful in a variety of areas, including spin-polarized nuclear scattering targets and electron beams, quantum-nondemolition spin measurements, and ultrasensitive magnetometry.

  5. Isotope separation using metallic vapor lasers

    NASA Technical Reports Server (NTRS)

    Russell, G. R.; Chen, C. J.; Harstad, K. G. (Inventor)

    1977-01-01

    The isotope U235 is separated from a gasified isotope mixture of U235 and U238 by selectively exciting the former from the ground state utilizing resonant absorption of radiation from precisely tuned lasers. The excited isotope is then selectively ionized by electron bombardment. It then is separated from the remaining isotope mixture by electromagnetic separation.

  6. Growth of Carbon Nanostructure Materials Using Laser Vaporization

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehozeky, S.

    2000-01-01

    Since the potential applications of carbon nanotubes (CNT) was discovered in many fields, such as non-structure electronics, lightweight composite structure, and drug delivery, CNT has been grown by many techniques in which high yield single wall CNT has been produced by physical processes including arc vaporization and laser vaporization. In this presentation, the growth mechanism of the carbon nanostructure materials by laser vaporization is to be discussed. Carbon nanoparticles and nanotubes have been synthesized using pulsed laser vaporization on Si substrates in various temperatures and pressures. Two kinds of targets were used to grow the nanostructure materials. One was a pure graphite target and the other one contained Ni and Co catalysts. The growth temperatures were 600-1000 C and the pressures varied from several torr to 500 torr. Carbon nanoparticles were observed when a graphite target was used, although catalysts were deposited on substrates before growing carbon films. When the target contains catalysts, carbon nanotubes (CNT) are obtained. The CNT were characterized by scanning electron microscopy, x-ray diffraction, optical absorption and transmission, and Raman spectroscopy. The temperature-and pressure-dependencies of carbon nanotubes' growth rate and size were investigated.

  7. Ambient Femtosecond Laser Vaporization and Nanosecond Laser Desorption Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Flanigan, Paul; Levis, Robert

    2014-06-01

    Recent investigations of ambient laser-based transfer of molecules into the gas phase for subsequent mass spectral analysis have undergone a renaissance resulting from the separation of vaporization and ionization events. Here, we seek to provide a snapshot of recent femtosecond (fs) duration laser vaporization and nanosecond (ns) duration laser desorption electrospray ionization mass spectrometry experiments. The former employs pulse durations of <100 fs to enable matrix-free laser vaporization with little or no fragmentation. When coupled to electrospray ionization, femtosecond laser vaporization provides a universal, rapid mass spectral analysis method requiring no sample workup. Remarkably, laser pulses with intensities exceeding 1013 W cm-2 desorb intact macromolecules, such as proteins, and even preserve the condensed phase of folded or unfolded protein structures according to the mass spectral charge state distribution, as demonstrated for cytochrome c and lysozyme. Because of the ability to vaporize and ionize multiple components from complex mixtures for subsequent analysis, near perfect classification of explosive formulations, plant tissue phenotypes, and even the identity of the manufacturer of smokeless powders can be determined by multivariate statistics. We also review the more mature field of nanosecond laser desorption for ambient mass spectrometry, covering the wide range of systems analyzed, the need for resonant absorption, and the spatial imaging of complex systems like tissue samples.

  8. Diode laser based water vapor DIAL using modulated pulse technique

    NASA Astrophysics Data System (ADS)

    Pham, Phong Le Hoai; Abo, Makoto

    2014-11-01

    In this paper, we propose a diode laser based differential absorption lidar (DIAL) for measuring lower-tropospheric water vapor profile using the modulated pulse technique. The transmitter is based on single-mode diode laser and tapered semiconductor optical amplifier with a peak power of 10W around 800nm absorption band, and the receiver telescope diameter is 35cm. The selected wavelengths are compared to referenced wavelengths in terms of random error and systematic errors. The key component of modulated pulse technique, a macropulse, is generated with a repetition rate of 10 kHz, and the modulation within the macropulse is coded according to a pseudorandom sequence with 100ns chip width. As a result, we evaluate both single pulse modulation and pseudorandom coded pulse modulation technique. The water vapor profiles conducted from these modulation techniques are compared to the real observation data in summer in Japan.

  9. ARTICLES: Thermal physics of transverse-discharge copper vapor lasers

    NASA Astrophysics Data System (ADS)

    Borovich, Boris L.; Grigoryan, R. A.; Kazeko, G. P.; Nikolaev, G. N.; Smirnov, V. M.

    1982-10-01

    One of the factors determining the ultimate characteristics of copper vapor lasers is the heating of the active medium by the pulse-periodic discharge providing the excitation. The gas temperature was measured on the axis of the discharge gap of a transversely excited copper vapor laser. Two methods were used: a spectroscopic method (based on the Doppler width of an emission line of the neon buffer gas) and an interferometric method (based on the fringe shift in a Mach-Zehnder interferometer at the instants when the discharge was switched abruptly on and off). Both methods yielded values close 2200 °K. The temperature distribution in the active zone with a rectangular cross section was computed numerically. The results of a theoretical calculation were used to estimate the efficiency of conversion of the discharge energy into heat, which was around 40%.

  10. Raman-shifted dye laser for water vapor DIAL measurements

    NASA Technical Reports Server (NTRS)

    Grossmann, B. E.; Singh, U. N.; Cotnoir, L. J.; Wilkerson, T. D.; Higdon, N. S.; Browell, E. V.

    1987-01-01

    For improved DIAL measurements of water vapor in the upper troposphere or lower stratosphere, narrowband (about 0.03/cm) laser radiation at 720- and 940-nm wavelengths was generated by stimulated Raman scattering (SRS), using the narrow linewidth (about 0.02/cm) output of a Nd:YAG-pumped dye laser. For a hydrogen pressure of 350 psi, the first Stokes conversion efficiencies to 940 nm were 20 percent and 35 percent, when using a conventional and waveguide Raman cell, respectively. The linewidth of the first Stokes line at high cell pressures, and the inferred collisional broadening coefficients, agree well with those previously measured in spontaneous Raman scattering.

  11. High average power magnetic modulator for metal vapor lasers

    DOEpatents

    Ball, Don G.; Birx, Daniel L.; Cook, Edward G.; Miller, John L.

    1994-01-01

    A three-stage magnetic modulator utilizing magnetic pulse compression designed to provide a 60 kV pulse to a copper vapor laser at a 4.5 kHz repetition rate is disclosed. This modulator operates at 34 kW input power. The circuit includes a step up auto transformer and utilizes a rod and plate stack construction technique to achieve a high packing factor.

  12. Scaling of strontium-vapor laser active volume

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Polunin, Yu. P.

    2008-01-01

    Variations in the energy performance of a self-terminating Sr-vapor laser (SrVL) are examined. The active laser volume is varied between 20 and 650 cm 3. A linear relation is revealed between the average power delivered by the SrVL and its active volume. The SrVL efficiency is found to increase with active volume and to be comparable with that of a copper-vapor laser for an active volume V = 650 cm 3 (0.45 %). As the volume is increased, the total lasing pulse duration increases from 30 to 120 ns. The beam divergence problems associated with the use of a Fabry-Perot cavity or an unstable resonator of the telescopic type are discussed. A total average power of 13.5 W is obtained from V = 650 cm 3 at a lasing PRR F = 19 kHz. The output power generated at different laser wavelengths is as follows: 10.4 W at λ = 6.456 μm, 2.6 W at λ = 3 μm, and 0.5 W at λ = 1 μm. The wavelength dependence of the lasing pulse duration is considered.

  13. Tm:germanate Fiber Laser for Planetary Water Vapor Atmospheric Profiling

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; De Young, Russell

    2009-01-01

    The atmospheric profiling of water vapor is necessary for finding life on Mars and weather on Earth. The design and performance of a water vapor lidar based on a Tm:germanate fiber laser is presented.

  14. Development of laser optogalvanic spectroscopy as a probe of alkali atoms in an MHD environment

    SciTech Connect

    Monts, D.L.; Qian, S.; Cook, R.L.; Shepard, W.S.

    1995-02-01

    Application of Laser Optogalvanic Spectroscopy (LOGS) to MHD combustion systems requires selection of an appropriate alkali atom electronic transition to monitor. These studies suggest that in MHD combustion systems, it is desirable to use cesium, which occurs as an impurity in potassium compounds, as a surrogate for potassium rather than to directly monitor potassium in order to obtain reliable determinations of seed concentration. Studies were also performed to investigate the effect of electrode corrosion on the normalized LOGS signal intensity at a fixed wavelength (578.238 nm). During six-hour experiments in a near-stoichiometric flame, the normalized LOGS signal intensity decreased by 40-50% for a -960 V rod electrode and by 10-20% for a -500 V rod electrode. These changes are attributed to buildup of an oxide coating on the electrode, reducing the collection efficiency of the electrode.

  15. Low pressure cesium and potassium Diode Pumped Alkali Lasers: pros and cons

    NASA Astrophysics Data System (ADS)

    Zhdanov, Boris V.; Rotondaro, Matthew D.; Shaffer, Michael K.; Knize, Randall J.

    2015-10-01

    This paper based on the talk presented at the Security plus Defence 2015 Conference held at Toulouse, France in September 2015. In this paper we present the results of our experiments on a comparative study of Cesium and Potassium based DPALs aimed to determine which of these two lasers has better potential for scaling to high powers. For both lasers we have chosen a so called "low pressure DPAL approach", which uses buffer gas pressure of about 1 Atm for spin-orbit mixing of the exited states of alkali atoms to provide population inversion in the gain medium. The goal of this study was to determine power limiting effects, which affect performance of these DPALs, and find out how these limiting effects can be mitigated. The experiments were performed using both static and flowing gain medium. In our experiments, we studied the performance of both lasers in CW and pulsed modes with different pulse duration and observed output power degradation in time from the initial value to the level corresponding to the CW mode of operation. As a result of this study, we revealed some essential positive and negative features of both DPALs, which should be taken into account for power scaling experiments.

  16. The optical pumping of alkali atoms using coherent radiation from semi-conductor injection lasers and incoherent radiation from resonance lamps

    NASA Technical Reports Server (NTRS)

    Singh, G.

    1973-01-01

    An experimental study for creating population differences in the ground states of alkali atoms (Cesium 133) is presented. Studies made on GaAs-junction lasers and the achievement of population inversions among the hyperfine levels in the ground state of Cs 133 by optically pumping it with radiation from a GaAs diode laser. Laser output was used to monitor the populations in the ground state hyperfine levels as well as to perform the hyperfine pumping. A GaAs laser operated at about 77 K was used to scan the 8521 A line of Cs 133. Experiments were performed both with neon-filled and with paraflint-coated cells containing the cesium vapor. Investigations were also made for the development of the triple resonance coherent pulse technique and for the detection of microwave induced hyperfine trasistions by destroying the phase relationships produced by a radio frequency pulse. A pulsed cesium resonance lamp developed, and the lamp showed clean and reproducible switching characteristics.

  17. From a metal vapor laser projection microscope to a laser monitor (by the 50 year-anniversary of metal vapor lasers)

    NASA Astrophysics Data System (ADS)

    Evtushenko, G. S.

    2015-12-01

    The paper presents the history of active optical systems development from a laser projection microscope to a laser monitor. The examples of object visualization and diagnostics of high speed processes hidden by the intense background radiation are discussed. These are the processes of laser-surface interaction, self-propagating high-temperature synthesis (SHS), the corona discharge in the air, the nanoparticle production process using a high-power fiber laser, and etc. The results obtained by different research groups suggest that high-speed metal vapor brightness amplifiers and active optical systems based on them need further research, development and novel applications.

  18. Analysis of temporal jitter in a copper vapor laser system.

    PubMed

    Durga Praveen Kumar, D; Gantayet, L M; Singh, Sunita; Rawat, A S; Rana, Paramjit; Rajasree, V; Agarwalla, Sandeep K; Chakravarthy, D P

    2012-02-01

    Temporal jitter in a magnetic pulse compression based copper vapor laser (CVL) system is analyzed by considering ripple present in the input dc power supply and ripple present in the magnetic core resetting power supply. It is shown that the jitter is a function of the ratio of operating voltage to the designed voltage, percentage ripple, and the total propagation delay of the magnetic pulse compression circuit. Experimental results from a CVL system operating at a repetition rate of 9 kHz are presented. PMID:22380123

  19. Atomic vapor laser isotope separation using resonance ionization

    SciTech Connect

    Comaskey, B.; Crane, J.; Erbert, G.; Haynam, C.; Johnson, M.; Morris, J.; Paisner, J.; Solarz, R.; Worden, E.

    1986-09-01

    Atomic vapor laser isotope separation (AVLIS) is a general and powerful technique. A major present application to the enrichment of uranium for light-water power-reactor fuel has been under development for over 10 years. In June 1985, the Department of Energy announced the selection of AVLIS as the technology to meet the nation's future need for enriched uranium. Resonance photoionization is the heart of the AVLIS process. We discuss those fundamental atomic parameters that are necessary for describing isotope-selective resonant multistep photoionization along with the measurement techniques that we use. We illustrate the methodology adopted with examples of other elements that are under study in our program.

  20. Explosive vaporization of metallic sodium microparticles by CW resonant laser radiation.

    PubMed

    Atutov, S N; Baldini, W; Biancalana, V; Calabrese, R; Guidi, V; Mai, B; Mariotti, E; Mazzocca, G; Moi, L; Pod'yachev, S P; Tomassetti, L

    2001-11-19

    Explosive vaporization of metallic Na microparticles stimulated by resonant cw laser radiation has been observed in a glass cell. Vaporization occurs at low laser-power density. The effect consists in the generation of optically thick and sharply localized Na vapor clouds propagating in the cell against the laser beam. The effect is explained by laser excitation of Na atoms, which collide onto the surface of the microparticles and transfer their internal energy. This causes other atoms to be vaporized and to continue the avalanche process. PMID:11736344

  1. Improved performance of the pulsed copper-vapor-laser CuCl-vapor-laser with a compact device by applying an ac continuous-glow-discharge

    NASA Astrophysics Data System (ADS)

    Saito, H.; Taniguchi, H.; Ohgami, K.

    1985-10-01

    An additional continuous-glow-discharge was applied to the aperiodic pulsed CuCl-vapor laser. The experimental results exhibited an increase of up to 60 percent the laser-output average power at the maximum point, an increase of 1.5 times the peak power and pulse repetition frequency, and twice the pulse width in the laser oscillation against the laser without the continuous-glow discharge. Further, the additional technique led the CuCl-vapor-laser to operate in the higher operating-temperature region.

  2. Femtosecond laser fluorescence and propagation in very dense potassium vapor.

    PubMed

    Makdisi, Y; Kokaj, J; Afrousheh, K; Nair, R; Mathew, J; Pichler, G

    2013-12-16

    Femtosecond (fs) laser propagation and fluorescence of dense potassium vapor was studied, and the spectral region around the first and the second doublets of the principal series lines of potassium atoms was investigated. In our search we did not observe the conical emission in the far field, although it was previously observed in the case of rubidium. We discuss the possible reason of this unexpected result. The fluorescence spectrum revealed Rb impurity resonance lines in emission due to the collisional redistribution from the K(4p) levels into the Rb(5p) levels. In the forward propagation of 400 nm femtosecond light we observed the molecular band red shifted from potassium second doublet. However, no molecular spectrum was observed when the mode-locked fs laser light was discretely tuned within the wings of the first resonance lines, at 770 nm. PMID:24514609

  3. Application of pulsed-uv laser Raman spectroscopy to chemical vapor deposition

    SciTech Connect

    Hargis, P.J. Jr.

    1981-01-01

    Raman detection limits obtained with a KrF laser excitation source were comparable to those obtained by laser-induced fluorescence and photofragment emission spectroscopy under chemical vapor deposition conditions.

  4. UV laser-induced desorption mechanism analyzed through two-layer alkali halide samples.

    PubMed

    Fernández-Lima, F A; Ponciano, C R; da Silveira, E F

    2008-05-01

    Time of flight-mass spectrometry (TOF-MS) is used to analyze positive and negative desorbed ions generated by UV laser ablation of several alkali (X) halide (Y) salts. Most of the observed desorbed cluster ions have the structure (XY)(n)X(+) or (XY)(n)Y(-). Their desorption yields decrease as exp(-kn), where k approximately 2 for both series, suggesting that the neutral component (XY)(n) plays the dominant role in the desorption process. Mass spectrum measurements were performed for compound samples in which two salts (out of CsI, RbI, KBr, KCl and KI) are homogeneously mixed or disposed in two superposed layers. The detection of small new ion species and large cluster ions of the original salts supports the scenario that the uppermost layers are completely atomized while deep layers are emitted colder and fragmented: It is proposed that ns-pulsed laser induced desorption of ionic salts occurs via two sequential mechanisms: (1) ejection of cations and anions in the hot plume, followed by recombination into new cluster ions and (2) ejection of relatively cold preformed species originated from deep layers or from periphery of the irradiated region. PMID:18095386

  5. Single frequency and wavelength stabilized near infrared laser source for water vapor DIAL remote sensing application

    NASA Astrophysics Data System (ADS)

    Chuang, Ti; Walters, Brooke; Shuman, Tim; Losee, Andrew; Schum, Tom; Puffenberger, Kent; Burnham, Ralph

    2015-02-01

    Fibertek has demonstrated a single frequency, wavelength stabilized near infrared laser transmitter for NASA airborne water vapor DIAL application. The application required a single-frequency laser transmitter operating at 935 nm near infrared (NIR) region of the water vapor absorption spectrum, capable of being wavelength seeded and locked to a reference laser source and being tuned at least 100 pm across the water absorption spectrum for DIAL on/off measurements. Fibertek is building a laser transmitter system based on the demonstrated results. The laser system will be deployed in a high altitude aircraft (ER-2 or UAV) to autonomously perform remote, long duration and high altitude water vapor measurements.

  6. Industrial aspects of precision machining with copper vapor lasers

    NASA Astrophysics Data System (ADS)

    Hartmann, Martin; Koch, Juergen; Lang, Adolf; Schutte, Karsten; Bergmann, Hans W.

    1997-08-01

    The applications of conventional infrared lasers running cw or quasi-sw for drilling, cutting and shaping are limited in the precision achievable due to the long interaction time which leads to heat affected zones. The necessity to use a gas jet to blow the molten material out of the cut kerf will damage fragile workpieces like thin foils. Short laser pulses of sufficient intensity remove the material directly by evaporation and minimize the amount of heat transferred into the solid. Classical infrared laser sources generate a shielding air plasma within some ns at power densities above some 107W/cm2. The optical breakdown threshold value in air can be shifted to higher intensities by using visible light as well as reducing the focal diameter. An alternative way is to shorten the pulse duration to less than 10 ps that a plasma is generated only after the pulse. Thus, the material removal process begins after the deposition of the pulse energy into the material. But such short pulses will generate a pressure wave due to the sudden thermal expansion and can damage or destroy microscopic components. For industrial production the productivity is a further aspect. Hence, a certain mean power is required in order to obtain the desired production rate. Considering the above aspects, copper vapor lasers (CVLs) with ns pulse duration are well suited for precision machining of metals and ceramics. Processing with CVLs is an advantage in that its wavelength is highly absorbed by metallic targets and the probability for the optical breakdown in air is low. CVLs in an oscillator-amplifier-setup incorporate diffraction limited beam quality and high average power. The present paper outlines the potential of the CVL for the industrial use regarding high processing speed and precision. Under these aspects the limiting mechanisms on the material removal process and the necessary processing strategies for scaling up the productivity are shown. The relevant laser parameters for

  7. Alexandrite laser characterization and airborne lidar developments for water vapor DIAL measurements

    NASA Technical Reports Server (NTRS)

    Ponsardin, P.; Higdon, N. S.; Grossmann, B. E.; Browell, E. V.

    1991-01-01

    The spectral characteristics of an Alexandrite laser used for making water vapor DIAL measurements have been evaluated. The optical servo-system used to lock the laser wavelength on a water vapor absorption line is described. A brief description of the DIAL system is given and the data obtained with this lidar during flight tests in March 1990 are also presented.

  8. Stabilization and spectral characterization of an alexandrite laser for water vapor lidar measurements

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Higdon, Noah S.; Grossman, Benoist E.; Browell, Edward V.

    1991-01-01

    A description of an optical system used to lock the alexandrite laser frequency on a water vapor absorption line is presented. The laser spectral characteristics, which include the spectral purity, the effect of the laser linewidth on the absorption, and the laser wavelength stability, are evaluated.

  9. Alkali metal vapor removal from pressurized fluidized-bed combustor flue gas. Quarterly report, October-December 1979

    SciTech Connect

    Johnson, I.; Swift, W.M.; Lee, S.H.D.; Jonke, A.A.

    1980-07-01

    This work supports the program to develop methods for the cleanup of combustion gases from pressurized fluidized-bed coal combustors so that the cleaned gases can be used for downstream gas turbines. This report presents the results of studies to develop granular sorbents for removing gaseous alkali metal compounds from high-temperature high-pressure combustion gases. Activated bauxite, one of the sorbents found to be effective, can be reused after removal of the alkali compound by a water-leaching process. Results of testing of this leaching process are reported. An experimental appartus for testing sorbents at high pressure has been built; results of preliminary tests are reported.

  10. Influence of the pump-to-laser beam overlap on the performance of optically pumped cesium vapor laser.

    PubMed

    Cohen, Tom; Lebiush, Eyal; Auslender, Ilya; Barmashenko, Boris D; Rosenwaks, Salman

    2016-06-27

    Experimental and theoretical study of the influence of the pump-to-laser beam overlap, a crucial parameter for optimization of optically pumped alkali atom lasers, is reported for Ti:Sapphire pumped Cs laser. Maximum laser power > 370 mW with an optical-to-optical efficiency of 43% and slope efficiency ~55% was obtained. The dependence of the lasing power on the pump power was found for different pump beam radii at constant laser beam radius. Non monotonic dependence of the laser power (optimized over the temperature of the Cs cell) on the pump beam radius was observed with a maximum achieved at the ratio ~0.7 between the pump and laser beam radii. The optimal temperature decreased with increasing pump beam radius. A simple optical model of the laser, where Gaussian spatial shapes of the pump and laser intensities in any cross section of the beams were assumed, was compared to the experiments. Good agreement was obtained between the measured and calculated dependence of the laser power on the pump power at different pump beam radii and also of the laser power, threshold pump power and optimal temperature on the pump beam radius. The model does not use empirical parameters such as mode overlap efficiency and can be applied to different Ti:Sapphire and diode pumped alkali lasers with arbitrary spatial distributions of the pump and laser beam widths. PMID:27410591

  11. High-repetition-rate tunable dye lasers pumped by copper vapor laser

    SciTech Connect

    Zherikin, A.N.; Letokhov, V.S.; Mishin, V.I.; Belyaev, V.P.; Evtyunin, A.N.; Lesnoi, M.A.

    1981-06-01

    A study was made of stimulated emission and amplification of light in lasers with active media consisting of alcohol solutions of rhodamines 110, 6G, and B, and of oxazine 17. The pulse repetition frequency was 10 kHz and pumping was provided by a mass-produced copper vapor laser of the ILGI-101 type. The dye lasers emitted in the range 530--720 nm. The efficiency of the oxazine 17 laser was 20% and the efficiency of the rhodamine 6G amplifier was 30% when the width of the laser emission spectrum was 0.8 cm/sup -1/. A Fabry--Perot interferometer was used to reduce the width of the spectrum to 0.04 cm/sup -1/, but this reduced the efficiency to 7%. The maximum output power was 0.6 W. The radiation was transformed to the second harmonic in the 265--360 nm range with an efficiency of 5%.

  12. BRIEF COMMUNICATIONS: High-repetition-rate tunable dye lasers pumped by copper vapor laser

    NASA Astrophysics Data System (ADS)

    Zherikin, A. N.; Letokhov, V. S.; Mishin, V. I.; Belyaev, V. P.; Evtyunin, A. N.; Lesnoĭ, M. A.

    1981-06-01

    A study was made of stimulated emission and amplification of light in lasers with active media consisting of alcohol solutions of rhodamines 110, 6G, and B, and of oxazine 17. The pulse repetition frequency was 10 kHz and pumping was provided by a mass-produced copper vapor laser of the ILGI-101 type. The dye lasers emitted in the range 530-720 nm. The efficiency of the oxazine 17 laser was 20% and the efficiency of the rhodamine 6G amplifier was 30% when the width of the laser emission spectrum was 0.8 cm-1. A Fabry-Perot interferometer was used to reduce the width of the spectrum to 0.04 cm-1, but this reduced the efficiency to 7%. The maximum output power was 0.6 W. The radiation was transformed to the second harmonic in the 265-360 nm range with an efficiency of 5%.

  13. [Vaporization of urethral stenosis using the KTP 532 laser].

    PubMed

    Schmidlin, F; Oswald, M; Iselin, C; Rohner, S; Jichlinski, P; Delacrétaz, G; Leisinger, H J; Graber, P

    1997-01-01

    The authors treated 16 patients presenting with a total of 20 anterior urethral strictures using the KTP 16 Laser. The aetiology was iatrogenic in 50% of cases, infectious in 20% of cases, traumatic in 20% of cases and unknown in 10% of cases. The stricture was situated in the bulbous urethra (80%), membranous urethra (10%) or penil urethra (10%). Laser vaporization of the urethral stricture was performed over the entire circumference of the urethra when necessary, followed by bladder drainage by urethral catheter for 24 hours. All patients were prospectively reviewed at 3 weeks, 3 months and 6 months (clinical symptoms, uroflowmetry, cystourethrography). A complete symptom and urodynamic success was obtained in 13 patients (81%) at 3 and 6 months. The stricture recurred in 4 patients, but only three of them (19%) required treatment (reoperation of repeat dilatations). The mean maximum flow rate increased from 6 mL/s to 20 mL/s at 3 months and was maintained at 19 mL/s at 6 months. No intraoperative or postoperative complications were observed. In conclusion, our results confirm that KTP 532 laser urethral strictures is a reliable and effective method in the medium term. These good results also suggest an advantage in terms of the recurrence rate in comparison with internal urethrotomy. However, our series needs to be evaluated with a longer follow-up and prospective, randomized trials comparing the two methods need to be conducted. PMID:9157820

  14. Detection of vapor phase mercury species by laser fluorescence methods

    NASA Astrophysics Data System (ADS)

    Tong, Xiaomei

    Several mercury species emissions have been identified in off-gases from industrial processes. At present, there is no commercial continuous emission monitoring (CEM) technique or instrumentation to reliably monitor volatile mercury species emissions from industrial stacks. Conventional measurement methods, such as cold vapor trap based techniques for elemental mercury, have difficulty in achieving both high sensitivity and the fast time resolution required for real-time monitoring. This doctoral research work gives a systematic study of potential methods for real-time trace detection of volatile elemental mercury and mercury compounds in industrial stack gases. It is based on laser-induced fluorescence techniques; photofragment fluorescence spectroscopy for detection of volatile mercury compounds, and resonance fluorescence for detection of elemental mercury. The capabilities and limitations of these detection techniques are investigated in this dissertation. Detection of mercury compounds is a challenge since they are non-fluorescent. With photofragment fluorescence spectroscopy, target compound concentrations are related to the fluorescence intensity from an excited fragment. In this doctoral research work, low concentrations of mercuric bromide vapor in an atmospheric pressure flow cell are irradiated by a focused laser beam at 222nm. Photofragment fluorescence is monitored at 253.7nm. Two detection schemes, Charge Coupled Device (CCD) and photomultiplier tube (PMT), are applied for the measurement of photofragment fluorescence. The performances of these two systems are compared in the dissertation. A supersonic jet is combined with resonance fluorescence for detection of elemental mercury vapor. With test gas expanded into a vacuum, fluorescence quenching and spectral broadening are reduced. In the experiment, the gas jet is crossed with a laser beam at 253.7nm to excite atomic fluorescence, which is distinguished from the elastic background by time gating

  15. PROCESS OF RECOVERING ALKALI METALS

    DOEpatents

    Wolkoff, J.

    1961-08-15

    A process is described of recovering alkali metal vapor by sorption on activated alumina, activated carbon, dehydrated zeolite, activated magnesia, or Fuller's earth preheated above the vaporization temperature of the alkali metal and subsequent desorption by heating the solvent under vacuum. (AEC)

  16. Endoscopic photodynamic therapy of tumors using gold vapor laser

    NASA Astrophysics Data System (ADS)

    Kuvshinov, Yury P.; Poddubny, Boris K.; Mironov, Andrei F.; Ponomarev, Igor V.; Shental, V. V.; Vaganov, Yu. E.; Kondratjeva, T. T.; Trofimova, E. V.

    1996-01-01

    Compact sealed-off gold vapor laser (GVL) with 2 W average power and 628 nm wavelength was used for endoscopic photodynamic therapy in 20 patients with different tumors in respiratory system and upper gastrointestinal tract. Russian-made hematoporphyrin derivative (Hpd) `Photohem' was used as a photosensitizer. It was given intravenously at a dose of 2 - 2.5 mg/kg body weight 48 hours prior to tumor illumination with 628 nm light from GVL. Intermittent irradiation with GVL was done through flexible endoscope always under local anaesthesia at a power of 200 - 400 mW/sm2 and a dose of 150 - 400 J/sm2. 80% patients showed complete or partial response depending on stage of tumor. In cases of early gastric cancer all patients had complete remission with repeated negative biopsies. No major complication occurred.

  17. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    SciTech Connect

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-15

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized {sup 208-210}Fr ion beams at beam energies of 5 keV and intensities of 10{sup 5} s{sup -1}. Efficient neutralization ({>=}80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  18. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    NASA Astrophysics Data System (ADS)

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized F208-210r ion beams at beam energies of 5 keV and intensities of 105 s-1. Efficient neutralization (≥80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  19. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers.

    PubMed

    Sell, J F; Gulyuz, K; Sprouse, G D

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized (208-210)Fr ion beams at beam energies of 5 keV and intensities of 10(5) s(-1). Efficient neutralization (> or = 80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate. PMID:20059132

  20. 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.

  1. Alkali metal vapor removal from pressurized fluidized-bed combustor flue gas. Annual report, October 1979-September 1980

    SciTech Connect

    Johnson, I.; Swift, W.M.; Lee, S.H.D.

    1980-10-01

    In the application of pressurized fluidized-bed combustion (PFBC) to the generation of electricity, hot corrosion of the gas turbine (downstream from the combustor) by alkali metal compounds is a potential problem. The objective of this investigation is to develop a method for the removal of gaseous alkali metal compounds from the high-pressure high-temperature gas from a PFBC before the gas enters the gas turbine. The use of a granular bed filter, with either diatomaceous earth or activated bauxite as the bed material, is under study. Breakthrough data are reported on the sorption of gaseous NaCl by activated bauxite. Results are reported for the regeneration of activated bauxite using water leaching and a thermal swing method.

  2. Determination of flue gas alkali concentrations in fluidized-bed coal combustion by excimer-laser-induced fragmentation fluorescence

    SciTech Connect

    Hartinger, K.T.; Monkhouse, P.B.; Wolfrum, J.; Baumann, H.; Bonn, B.

    1994-12-31

    Gas-phase sodium concentrations were measured for the first time in situ in the flue gas of a fluidized-bed reactor by the excimer-laser-induced fragmentation fluorescence (ELIF) technique. This method involves using ArF-excimer laser light at 193 nm to simultaneously photodissociate the alkali compounds of interest and excite electronically the alkali atoms formed. The resulting fluorescence from Na (3{sup 2}P) atoms can he readily detected at 589 nm. Measured signals were converted to absolute concentrations using a calibration system that monitors alkali compounds under known conditions of temperature, pressure, and composition and rising the same optical setup as at the reactor. Several different coals were investigated under a specific set of reactor conditions at total pressures close to 1 bar. Sodium concentrations ranging from the sub-ppb region to 20 ppb were obtained, and a detection limit for sodium of 0.1 ppb under the present conditions was estimated. Over the course of the reactor program, contrasting concentration histories were observed for the two lignites and the hard coal investigated. In particular, significantly higher sodium concentrations were found for the hard coal, consistent with both the higher chlorine and sodium contents determined in the corresponding coal analysis.

  3. The threshold of vapor channel formation in water induced by pulsed CO2 laser

    NASA Astrophysics Data System (ADS)

    Guo, Wenqing; Zhang, Xianzeng; Zhan, Zhenlin; Xie, Shusen

    2012-12-01

    Water plays an important role in laser ablation. There are two main interpretations of laser-water interaction: hydrokinetic effect and vapor phenomenon. The two explanations are reasonable in some way, but they can't explain the mechanism of laser-water interaction completely. In this study, the dynamic process of vapor channel formation induced by pulsed CO2 laser in static water layer was monitored by high-speed camera. The wavelength of pulsed CO2 laser is 10.64 um, and pulse repetition rate is 60 Hz. The laser power ranged from 1 to 7 W with a step of 0.5 W. The frame rate of high-speed camera used in the experiment was 80025 fps. Based on high-speed camera pictures, the dynamic process of vapor channel formation was examined, and the threshold of vapor channel formation, pulsation period, the volume, the maximum depth and corresponding width of vapor channel were determined. The results showed that the threshold of vapor channel formation was about 2.5 W. Moreover, pulsation period, the maximum depth and corresponding width of vapor channel increased with the increasing of the laser power.

  4. High-Efficiency 894-nm Laser Emission of Laser-Diode-Bar-Pumped Cesium-Vapor Laser

    NASA Astrophysics Data System (ADS)

    Zheng, Yujin; Niigaki, Minoru; Miyajima, Hirofumi; Hiruma, Teruo; Kan, Hirofumi

    2009-03-01

    We report a high-efficiency cesium-vapor laser with a high-gas-pressure (˜3-atm helium and 0.49-atm ethane) cell pumped by a high-power external-cavity laser-diode bar. Peak laser power of 12.1 W at 894 nm was obtained, when the absorbed peak pump power was 23.1 W. The achieved slope efficiencies with the incident pump power and the absorbed pump power were 33 and 81.7%, respectively.

  5. Single titanium crystals encapsulated in carbon nanocages obtained by laser vaporization of sponge titanium in benzene vapor

    NASA Astrophysics Data System (ADS)

    Chen, Hong; Huang, Rong-bin; Tang, Zi-chao; Zheng, Lan-sun; Zhou, Guang-wen; Zhang, Ze

    2000-07-01

    A technique, laser vaporization by ablating at a solid target in the vapor phase, is developed to produce encapsulated titanium nanocrystals. By vaporizing sponge titanium in benzene vapor, the single titanium crystals encapsulated in carbon nanocages have been synthesized in good yields. The sizes of the encapsulated crystals are around 5-15 nm and the numbers of the wrapped graphitic layers are on the order of 3-10 layers. Characteristic lattice spacings and angles observed by high-resolution transmission electron microscopy identify two phases of the nanocrystals inside the carbon onion cavities as α-Ti and β-Ti. The latter has never been stable below 850 °C until the experiment. The encapsulated titanium crystals adsorbed a large amount of hydrogen released in the synthesis.

  6. Characteristics of a dye laser amplifier transversely pumped by copper vapor lasers with a two-dimensional calculation model

    SciTech Connect

    Sugiyama, A.; Nakayama, T.; Kato, M.; Maruyama, Y.

    1997-08-01

    A two-dimensional rate equation model, taking into consideration the transverse absorption loss of pump laser power, is proposed to evaluate the characteristics of a dye laser amplifier with a large input laser beam diameter pumped by high average power copper vapor lasers. The calculations are in good agreement with the measurements taken with a Rhodamine 6G dye, and the model can be used for evaluation of the dye concentration at any wavelength. {copyright} 1997 Optical Society of America

  7. Method and apparatus for convection control of metallic halide vapor density in a metallic halide laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J. (Inventor)

    1982-01-01

    An apparatus is disclosed in which a reservoir containing copper chloride is heated so that the copper chloride is maintained in a liquid form. The apparatus includes a means for flowing a buffer gas (which in the exemplary embodiment is neon) over the liquid copper chloride to provide a mixture of copper chloride vapor and neon above the liquid copper chloride. A conduit provides fluid communication between the reservoir containing the copper chloride vapor/neon mixture and the laser. The copper chloride vapor density in the laser is related to the liquid copper chloride temperature and the neon flow rate through the reservoir. In accordance with a further feature of the exemplary embodiment, neon is also provided directly to the laser in order to provide a further means of controlling the copper chloride vapor density in the laser.

  8. Laser vaporization/ionization interface for coupling microscale separation techniques with mass spectrometry

    DOEpatents

    Yeung, Edward S.; Chang, Yu-chen

    1999-06-29

    The present invention provides a laser-induced vaporization and ionization interface for directly coupling microscale separation processes to a mass spectrometer. Vaporization and ionization of the separated analytes are facilitated by the addition of a light-absorbing component to the separation buffer or solvent.

  9. Laser vaporization/ionization interface for coupling microscale separation techniques with mass spectrometry

    DOEpatents

    Yeung, E.S.; Chang, Y.C.

    1999-06-29

    The present invention provides a laser-induced vaporization and ionization interface for directly coupling microscale separation processes to a mass spectrometer. Vaporization and ionization of the separated analytes are facilitated by the addition of a light-absorbing component to the separation buffer or solvent. 8 figs.

  10. Note: A novel and robust circuit for jitter reduction in copper vapor laser system

    NASA Astrophysics Data System (ADS)

    Mishra, R. K.; Raju, D. V. S.; Nakhe, S. V.

    2015-11-01

    A novel circuit scheme is presented to improve timing jitter performance of high voltage pulse power supply utilizing semiconductor switches and magnetic pulse compressors, for pumping pulsed copper vapor lasers. The circuit effectively handles reflected energy from the laser load and achieves better jitter performance. The proposed circuit scheme had typical jitter value of ±2 ns whereas the standard circuit used earlier had jitter of more than ±10 ns under similar conditions. Performance of the circuit scheme is studied on a copper vapor laser operating at average laser power of 40 W.

  11. Note: A novel and robust circuit for jitter reduction in copper vapor laser system.

    PubMed

    Mishra, R K; Raju, D V S; Nakhe, S V

    2015-11-01

    A novel circuit scheme is presented to improve timing jitter performance of high voltage pulse power supply utilizing semiconductor switches and magnetic pulse compressors, for pumping pulsed copper vapor lasers. The circuit effectively handles reflected energy from the laser load and achieves better jitter performance. The proposed circuit scheme had typical jitter value of ±2 ns whereas the standard circuit used earlier had jitter of more than ±10 ns under similar conditions. Performance of the circuit scheme is studied on a copper vapor laser operating at average laser power of 40 W. PMID:26628188

  12. Comparison of the treatment of vascular lesions with the copper-vapor laser and flashlamp-pumped dye laser

    NASA Astrophysics Data System (ADS)

    Flock, Stephen T.; Waner, Milton; McGrew, Ben; Colvin, G. B.; Montague, Donna

    1992-08-01

    Vascular lesions such as port-wine stains and telangiectases are sometimes treated with carbon-dioxide lasers, argon lasers or argon-pumped dye lasers; however these lasers are non- specific in their thermal effect on tissues and as a result often cause significant scarring. Recently, evidence has accumulated that the flashlamp-pumped dye (585 nm) and copper- vapor (578 nm) lasers, which produce pulsed light that is efficiently absorbed by hemoglobin, are more selective in coagulating abnormal vascular tissue and as a result give a superior clinical result. It is not yet clear what the most important physical and biological mechanisms are during the light-tissue interaction mediated by these two lasers. The post-treatment sequence of events is different for tissue irradiated by each laser; most significantly, the flashlamp-pumped dye laser causes significant transient purpura, whereas the copper vapor laser causes blanching and eschar formation. The clinical outcome, that is regression of the lesion, is equally successful with either laser although some evidence has accumulated showing that the flashlamp-pumped dye laser is best suited to the treatment of small vessel disease while the copper-vapor laser is better for the treatment of large vessel disease. In this paper, we will discuss our observations of the treatment of vascular lesions on humans with the copper-vapor and flashlamp-pumped dye lasers using empirically derived efficacious treatment parameters. Mathematical models of light and heat propagation and in vivo experiments involving mice ears and rat skin flaps will be used to elucidate what we feel are the important underlying mechanisms of this vascular lesion laser therapy.

  13. Laser-assisted chemical vapor deposition of nickel and laser cutting in integrated circuit restructuring

    NASA Astrophysics Data System (ADS)

    Remes, J.; Moilanen, H.; Leppävuori, S.

    1997-01-01

    Laser-assisted chemical vapor deposition (LCVD) of nickel from Ni(CO)4 has been utilised for the restructuring of integrated circuit (IC) interconnections. Nickel lines were deposited on a SiO2 passivated IC to achieve new local interconnections between integrated circuit structures. Depositions were carried out over the pressure range of 0.2 to 2.2 mbar of pure Ni(CO)4 buffered in 0 to 800 mbar He. Argon ion laser wavelengths of 488 and 514.5 nm, laser power of 50-150 mW and a laser scan speed of 80 μm/s were utilised for the deposition. The morphology and chemical contents of the deposited interconnection microstructures was examined by AFM, optical microscopy and LIMA. The resistivity of the deposited lines was found to be close to the nickel bulk resistivity. The utilisation of Nd: YAG and XeCl excimer lasers in the cutting of Al and Mo conductor lines for integrated circuit modification is also described.

  14. Gas dynamic effect in high energy fluid diode pumped alkali vapor laser

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Li, Wenyu; Wang, Hongyan; Yang, Zining; Xu, Xiaojun

    2012-11-01

    In this paper, a simple one dimensional heated flow analysis model and 3-D finite volume method (FVM) is set to discuss the real gas dynamic effect in FDPAL. We found that huge amount of waste heat deposited in extreme compact volume size will notably affect active medium's local velocity, temperature and the density distribution along flow direction, and would accordingly affect pump beam's absorption and change optimized lasing conditions, hence, a comprehensive model incorporate gas dynamic effect should be built for DPAL's next stage development. We further proposed that expanding fluid channel may be a choice to increase optical thickness along pumping direction and alleviate this effect.

  15. Vapor-melt Ratio in Laser Fine Cutting of Slot Arrays

    SciTech Connect

    Wang Xuyue; Meng Qingxuan; Kang Renke; Xu Wenji; Guo Dongming; Wang Lianji

    2011-05-04

    In order to improve cut quality for slot arrays, a new method of laser fine cutting under the consideration of the ratio of vapor to melt is presented. Laser cutting of 6063 aluminum alloy sheet, 0.5 mm in thickness, was carried out on a JK701H Nd:YAG pulse laser cutting system. The effects of vapor-melt ratio on kerf width, surface roughness and recast layer were studied which relate cutting qualities. Observation on the cut samples with different vapor-melt ratios (0.687, 1.574, 3.601 varied with laser power increasing, and 1.535, 3.601, 7.661 with decreasing of beam cutting speed) shows that high vapor-melt ratio improves laser cut quality clearly. Kerf width 0.2 mm of smooth area on kerf top area and thickness 2.03 {mu}m of recast layer are obtained. No dross was found on the kerf bottom and the percentage of the smooth area is up to 40% out of whole kerf side. The research on vapor-melt ratio provides a deeper understanding of laser cutting and improves laser cut quality effectively.

  16. Advances in Diode-Laser-Based Water Vapor Differential Absorption Lidar

    NASA Astrophysics Data System (ADS)

    Spuler, Scott; Repasky, Kevin; Morley, Bruce; Moen, Drew; Weckwerth, Tammy; Hayman, Matt; Nehrir, Amin

    2016-06-01

    An advanced diode-laser-based water vapor differential absorption lidar (WV-DIAL) has been developed. The next generation design was built on the success of previous diode-laser-based prototypes and enables accurate measurement of water vapor closer to the ground surface, in rapidly changing atmospheric conditions, and in daytime cloudy conditions up to cloud base. The lidar provides up to 1 min resolution, 150 m range resolved measurements of water vapor in a broad range of atmospheric conditions. A description of the instrument and results from its initial field test in 2014 are discussed.

  17. Recent progress in the development of electrically and optically pumped dye vapor lasers

    NASA Astrophysics Data System (ADS)

    Marowsky, G.

    1980-01-01

    This paper reviews new results in the field of organic dye vapor lasers. Gain studies of the scintillator dye POPOP in liquid solution and in the vapor phase show that a dye vapor exhibits optical gain nearly as high as in the solution case under excitation by a N2 laser. Superradiant emission has been observed from both optically excited POPOP vapor and electron-beam excited vapor. The optimum operating conditions of an electron-beam pumped dye vapor-buffer gas system with high purity argon as buffer are reported. Potential energy transfer processes from the rare-gas buffer to the dye vapor are discussed. The metastable ionic species Ar2(+) has been identified as the most likely POPOP excitation source after intense electron pumping of the dense Ar buffer gas at typically 4-5 atm. An estimate of the conversion efficiency from electronic energy deposited in the Ar buffer to stimulated emission of the dye yields 5 percent. These results suggest that an efficient tunable electron beam pumped dye vapor laser is feasible.

  18. New powerful metal vapor lasers oscillating in deep ultraviolet and middle infrared spectral ranges

    NASA Astrophysics Data System (ADS)

    Temelkov, K. A.; Vuchkov, N. K.; Sabotinov, N. V.

    2010-09-01

    Middle infrared and deep ultraviolet laser systems, which are based on high-power high-beam-quality stable-operating He-SrBr2 and Cu+ Ne-CuBr lasers excited in nanosecond pulsed longitudinal discharge, are developed, patented and studied. Optimal discharge conditions, such as active zone diameter, vapor pressure, buffer-gas pressure, electrical excitation scheme parameters, average input power, pulse repetition frequency, are found. The highest output laser parameters are obtained for the Sr atom and Cu+ lasers, respectively. These lasers equipped with optical systems for control of laser radiation parameters, such as laser beam divergence, laser intensity distribution, etc. are used in a large variety of applications, such as precise material microprocessing, including biological tissues, determination of linear optical properties of different materials newly developed, laser-induced modification of conductive polymers, laserinduced fluorescence in wide-gap semiconductors, instead of free electron and excimer lasers, respectively.

  19. Vaporization behavior of non-stoichiometric refractory carbide materials and direct observations of the vapor phase using laser diagnostics

    SciTech Connect

    Butt, D.P.; Wantuck, P.J.; Rehse, S.J.; Wallace, T.C. Sr.

    1993-09-01

    Transition metal and actinide carbides, such as ZrC or NbC and UC or ThC, exhibit a wide range of stoichiometry, and therefore vaporize incongruently. At long times, steady state vaporization can be achieved where relative concentrations of atomic species on solid surface equals that in the gas phase. The surface composition under these steady state conditions is termed the congruently vaporizing composition, (CVC). Modeling the vaporization or corrosion behavior of this dynamic process is complex and requires an understanding of how the surface composition changes with time and a knowledge of CVC, which is both temperature and atmosphere dependent. This paper describes vaporization and corrosion behavior of non-stoichiometric refractory carbide materials and, as an example, describes a thermokinetic model that characterizes the vaporization behavior of the complex carbide U{sub x}Zr{sub 1-x}C{sub y} in hydrogen at 2500 to 3200 K. This model demonstrates that steady state corrosion of U{sub x}Zr{sub l-x}C{sub y} is rate limited by gaseous transport of Zr where partial pressure of Zr is determined by CVC. This paper also briefly describes efforts to image and characterize the vapor phase above the surface of ZrC in static and flowing gas environments using planar laser induced fluorescence. We have developed the method for monitoring and controlling the corrosion behavior of nuclear fuels in nuclear thermal rockets. However, the techniques described can be used, to image boundary layers, and could be used verifying corrosion models.

  20. Histologic comparison of the pulsed dye laser and copper vapor laser effects on pig skin

    SciTech Connect

    Tan, O.T.; Stafford, T.J.; Murray, S.; Kurban, A.K. )

    1990-01-01

    Albino pig skin was exposed to the copper vapor (CVL) and flash-lamp pulsed dye (PDL) lasers at 578 nm with a 3 mm diameter spotsize over a range of fluences until purpura and whitening were first established. The total irradiation time was the parameter that was varied in order for the CVL to reach the desired fluence. The lowest fluence producing each clinical endpoint was designated the threshold fluence: 34 J/cm{sup 2} was required to produce purpura using the CVL compared to 7.5 J/cm{sup 2} with the PDL laser. Histologically, skin exposed to purpura fluences from the CVL revealed the presence of constricted, disrupted papillary dermal blood vessels with trapped RBC's within them which were unlike those exposed to PDL where the irradiated vessels were dilated and packed with masses of intravascular agglutinated RBC's. The whitening threshold fluences for the CVL and PDL lasers were 67 J/cm{sup 2} and 29 J/cm{sup 2}, respectively. Streaming of epidermal cells and dermal collagen denaturation were observed in CVL irradiated skin, compared to occasional dyskeratotic epidermal cells and focal dermal collagen denaturation following PDL exposure. The mechanisms responsible for the clinical and histologic changes produced by the two laser systems are discussed.

  1. Laser vaporization of cirrus-like ice particles with secondary ice multiplication

    PubMed Central

    Matthews, Mary; Pomel, François; Wender, Christiane; Kiselev, Alexei; Duft, Denis; Kasparian, Jérôme; Wolf, Jean-Pierre; Leisner, Thomas

    2016-01-01

    We investigate the interaction of ultrashort laser filaments with individual 90-μm ice particles, representative of cirrus particles. The ice particles fragment under laser illumination. By monitoring the evolution of the corresponding ice/vapor system at up to 140,000 frames per second over 30 ms, we conclude that a shockwave vaporization supersaturates the neighboring region relative to ice, allowing the nucleation and growth of new ice particles, supported by laser-induced plasma photochemistry. This process constitutes the first direct observation of filament-induced secondary ice multiplication, a process that strongly modifies the particle size distribution and, thus, the albedo of typical cirrus clouds. PMID:27386537

  2. Laser vaporization of cirrus-like ice particles with secondary ice multiplication.

    PubMed

    Matthews, Mary; Pomel, François; Wender, Christiane; Kiselev, Alexei; Duft, Denis; Kasparian, Jérôme; Wolf, Jean-Pierre; Leisner, Thomas

    2016-05-01

    We investigate the interaction of ultrashort laser filaments with individual 90-μm ice particles, representative of cirrus particles. The ice particles fragment under laser illumination. By monitoring the evolution of the corresponding ice/vapor system at up to 140,000 frames per second over 30 ms, we conclude that a shockwave vaporization supersaturates the neighboring region relative to ice, allowing the nucleation and growth of new ice particles, supported by laser-induced plasma photochemistry. This process constitutes the first direct observation of filament-induced secondary ice multiplication, a process that strongly modifies the particle size distribution and, thus, the albedo of typical cirrus clouds. PMID:27386537

  3. Transfer of spin angular momentum from Cs vapor to nearby Cs salts through laser-induced spin currents

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Patton, B.; Olsen, B. A.; Jau, Y.-Y.; Happer, W.

    2011-06-01

    Optical pumping of alkali-metal atoms in vapor cells causes spin currents to flow to the cell walls where excess angular momentum accumulates in the wall nuclei. Experiments reported here indicate that the substantial enhancement of the nuclear-spin polarization of salts at the cell walls is primarily due to the nuclear-spin current, with a lesser contribution from the electron-spin current of the vapor.

  4. Transfer of spin angular momentum from Cs vapor to nearby Cs salts through laser-induced spin currents

    SciTech Connect

    Ishikawa, K.; Patton, B.; Olsen, B. A.; Jau, Y.-Y.; Happer, W.

    2011-06-15

    Optical pumping of alkali-metal atoms in vapor cells causes spin currents to flow to the cell walls where excess angular momentum accumulates in the wall nuclei. Experiments reported here indicate that the substantial enhancement of the nuclear-spin polarization of salts at the cell walls is primarily due to the nuclear-spin current, with a lesser contribution from the electron-spin current of the vapor.

  5. Application of high-resolution laser spectroscopy to the monitoring of vapor-phase metals

    SciTech Connect

    Lipert, R.J.; Wang, Z.M.; Schuler, R.; Edelson, M.C.

    1992-10-01

    Research conducted in the Ames Laboratory Nuclear Safeguards and Security Program is reviewed. Progress in applying high-resolution laser spectroscopy to the monitoring of vapor-phase metals is described. The spectroscopic techniques employed include fluorescence excitation in an atomic beam, laser atomic absorption in a heat-pipe oven and atomic beam, Doppler-free saturated absorption in a heat-pipe oven, and Doppler-free polarization spectroscopy for the stabilization of the laser wavelength.

  6. A Linearly-Polarized Cesium Vapor Laser with Fundamental Mode Output and Low Threshold

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Yong; Tan, Rong-Qing; Huang, Wei; Xu, Cheng

    2014-04-01

    We report a cesium vapor laser with fundamental mode output and a wavelength of 894 nm. The laser is pumped by a laser diode array with an external cavity of a holographic grating by using Littrow's structure. A slope efficiency of 22.4% is obtained by using a pumping source with a linewidth of 0.26 nm and 80 kPa methane as the buffer gas. The threshold pumping power is 1.56 W.

  7. Space Debris-de-Orbiting by Vaporization Impulse using Short Pulse Laser

    SciTech Connect

    Early, J; Bibeau, C; Claude, P

    2003-09-16

    Space debris constitutes a significant hazard to low earth orbit satellites and particularly to manned spacecraft. A quite small velocity decrease from vaporization impulses is enough to lower the perigee of the debris sufficiently for atmospheric drag to de-orbit the debris. A short pulse (picosecond) laser version of the Orion concept can accomplish this task in several years of operation. The ''Mercury'' short pulse Yb:S-FAP laser being developed at LLNL for laser fusion is appropriate for this task.

  8. Ex vivo efficacy evaluation of laser vaporization for treatment of benign prostatic hyperplasia using a 300-W high-power laser diode with a wavelength of 980 nm

    PubMed Central

    Takada, Junya; Honda, Norihiro; Hazama, Hisanao

    2014-01-01

    Background and Objective: Laser vaporization of the prostate is considered to be a promising treatment for benign prostatic hyperplasia (BPH), and efficiency of vaporization and hemostasis are both important parameters for such treatment. In this study, we used a high-power laser diode with a wavelength of 980 nm to obtain high vaporization efficiency with good hemostasis. The objective of this study is to evaluate the efficacy of laser vaporization for treatment of BPH in ex vivo experiments using a 300-W high-power laser diode with a wavelength of 980 nm quantitatively. Materials and Methods: An ex vivo experimental setup simulating clinical treatment situation was constructed. Bovine prostate tissue was used as a sample. The power setting was 100, 150, 200, 250, or 300 W, and the irradiation time was 0.5, 1, or 2 s. After laser irradiation, vaporized and coagulated depths were measured. Results: The vaporized depth increased with the laser power and irradiation time, and the results confirmed that the high-power laser diode could efficiently vaporize the prostate tissue. Coagulated depth increased as the laser power became higher. Conclusions: Laser vaporization of prostate tissue using a high-power laser diode with a wavelength of 980 nm represents a promising treatment for BPH; this method exhibits high vaporization efficiency and good hemostasis. However, operators must be aware of the risk of postoperative perforation of the prostatic capsule caused by coagulation of deep regions that cannot be visualized by endoscopic observation. PMID:25368442

  9. Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

    DOEpatents

    Hagans, K.; Berzins, L.; Galkowski, J.; Seng, R.

    1996-08-27

    The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer`s law. 6 figs.

  10. Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

    DOEpatents

    Hagans, Karla; Berzins, Leon; Galkowski, Joseph; Seng, Rita

    1996-01-01

    The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer's law.

  11. Erbium:YAG-laser induced vapor bubbles as a function of the quartz fiber tip geometry

    NASA Astrophysics Data System (ADS)

    Mrochen, Michael; Riedel, Peter; Donitzky, Christof; Seiler, Theo

    2001-07-01

    Background. The use of modern erbium: yttrium-aluminum- garnet (YAG) laser systems in ophthalmic microsurgery requires a precise knowledge of the size and dynamics of the laser induced vapor bubbles. The aim of this work was to clarify the possibilities of controlling the vapor bubble shape and size by using an optimized fiber tip geometry for various ophthalmic applications with the erbium:YAG laser. Methods. The mid-infrared radiation of free-running erbium:YAG laser was coupled optically into means of different low OH- quartz fiber tips to investigate the vapor bubble formation in water by high-speed photography. The core diameter of four fiber tips ranged from 200 up to 940 micrometers . Fourteen fiber tips were polished at an angle graduated from 10 degree(s) to 70 degree(s) over the full core diameter (seven fiber tips) and over the half core diameter (seven fiber tips). Three fiber tips were produced to have a curvature at the distal end with curvature radii of 160, 230, and 420 micrometers . Results. The shape as well as the size of erbium:YAG laser induced vapor bubbles can be controlled systematically by using adequate fiber tip geometries. In detail, the used different angles and curvatures demonstrate that the propagation direction of the vapor bubbles can be estimated by optical modeling considering Snell's law and the Fresnel laws at a quartz-air boundary. Beside this, the size of a vapor bubble can be predetermined by choosing ideal fiber tip geometries to reduce or increase the radiant exposure at the distal end of the quartz fiber tip. Conclusions. The good possibility of controlling the shape and size of vapor bubbles offers a wider range of new applications, especially in ophthalmic microsurgery such as erbium YAG laser vitrectomy.

  12. Fixation of bioactive calcium alkali phosphate on Ti6Al4V implant material with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Symietz, Christian; Lehmann, Erhard; Gildenhaar, Renate; Koter, Robert; Berger, Georg; Krüger, Jörg

    2011-04-01

    Bone implants made of metal, often titanium or the titanium alloy Ti6Al4V, need to be surface treated to become bioactive. This enables the formation of a firm and durable connection of the prosthesis with the living bone. We present a new method to uniformly cover Ti6Al4V with a thin layer of ceramics that imitates bone material. These calcium alkali phosphates, called GB14 and Ca10, are applied to the metal by dip coating of metal plates into an aqueous slurry containing the fine ceramic powder. The dried samples are illuminated with the 790 nm radiation of a pulsed femtosecond laser. If the laser fluence is set to a value just below the ablation threshold of the ceramic (ca. 0.4 J/cm 2) the 30 fs laser pulses penetrate the partly transparent ceramic layer of 20-40 μm thickness. The remaining laser fluence at the ceramic-metal interface is still high enough to generate a thin metal melt layer leading to the ceramic fixation on the metal. The laser processing step is only possible because Ti6Al4V has a lower ablation threshold (between 0.1 and 0.15 J/cm 2) than the ceramic material. After laser treatment in a fluence range between 0.1 and 0.4 J/cm 2, only the particles in contact with the metal withstand a post-laser treatment (ultrasonic cleaning). The non-irradiated rest of the layer is washed off. In this work, we present results of a successful ceramic fixation extending over larger areas. This is fundamental for future applications of arbitrarily shaped implants.

  13. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells

    NASA Astrophysics Data System (ADS)

    Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

    2016-02-01

    Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1-xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber|buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells.

  14. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells.

    PubMed

    Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

    2016-01-01

    Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1-xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber(|)buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells. PMID:26916212

  15. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells

    PubMed Central

    Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

    2016-01-01

    Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1−xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber|buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells. PMID:26916212

  16. Ion Partitioning at the liquid/vapor interface of a multi-component alkali halidesolution: A model for aqueous sea salt aerosols

    SciTech Connect

    Ghosal, Sutapa; Brown, Matthew A.; Bluhm, Hendrik; Krisch, Maria J.; Salmeron, Miquel; Jungwirth, Pavel; Hemminger, John C.

    2008-12-22

    The chemistry of Br species associated with sea salt ice and aerosols has been implicated in the episodes of ozone depletion reported at Arctic sunrise. However, Br{sup -} is only a minor component in sea salt, which has a Br{sup -}/Cl{sup -} molar ratio of {approx}0.0015. Sea salt is a complex mixture of many different species, with NaCl as the primary component. In recent years experimental and theoretical studies have reported enhancement of the large, more polarizable halide ion at the liquid/vapor interface of corresponding aqueous alkali halide solutions. The proposed enhancement is likely to influence the availability of sea salt Br{sup -} for heterogeneous reactions such as those involved in the ozone depletion episodes. We report here ambient pressure x-ray photoelectron spectroscopy studies and molecular dynamics simulations showing direct evidence of Br{sup -} enhancement at the interface of an aqueous NaCl solution doped with bromide. The experiments were carried out on samples with Br{sup -}/Cl{sup -} ratios in the range 0.1% to 10%, the latter being also the ratio for which simulations were carried out. This is the first direct measurement of interfacial enhancement of Br{sup -} in a multi-component solution with particular relevance to sea salt chemistry.

  17. Electron collisions with cesium atoms - benchmark calculations and application to modeling an excimer-pumped alkali laser

    NASA Astrophysics Data System (ADS)

    Zatsarinny, Oleg; Bartschat, Klaus; Babaeva, Natalia; Kushner, Mark

    2014-10-01

    The B-spline R-matrix (BSR) with pseudostates method was employed to describe electron collisions with cesium atoms. Over 300 states were kept in the close-coupling expansion, including a large number of pseudostates to model the effect of the Rydberg spectrum and the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, excitation, and ionization for incident energies up to 200 eV are presented and compared to previous results [2,3] and experimental data. Our data were used to model plasma formation in the excimer-pumped alkali laser, XPAL, operating on the Cs (62P3 / 2 , 1 / 2 --> (62S1 / 2) (852nm and 894nm) transitions. At sufficiently high operating temperature, pump power, and repetition rate, plasma formation in excess of 1014--1015cm-3 occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels. Work supported by the NSF under PHY-1068140, PHY-1212450, and the XSEDE allocation PHY-090031 (OZ, KB), and by the DoD High Energy Laser Multidisciplinary Research Initiative (NYB, MJK).

  18. Dichroic atomic vapor laser lock with multi-gigahertz stabilization range.

    PubMed

    Pustelny, S; Schultze, V; Scholtes, T; Budker, D

    2016-06-01

    A dichroic atomic vapor laser lock (DAVLL) system exploiting buffer-gas-filled millimeter-scale vapor cells is presented. This system offers similar stability as achievable with conventional DAVLL system using bulk vapor cells, but has several important advantages. In addition to its compactness, it may provide continuous stabilization in a multi-gigahertz range around the optical transition. This range may be controlled either by changing the temperature of the vapor or by application of a buffer gas under an appropriate pressure. In particular, we experimentally demonstrate the ability of the system to lock the laser frequency between two hyperfine components of the (85)Rb ground state or as far as 16 GHz away from the closest optical transition. PMID:27370426

  19. Optoacoustic measurements of water vapor absorption at selected CO laser wavelengths in the 5-micron region

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1976-01-01

    Measurements of water vapor absorption were taken with a resonant optoacoustical detector (cylindrical pyrex detector, two BaF2 windows fitted into end plates at slight tilt to suppress Fabry-Perot resonances), for lack of confidence in existing spectral tabular data for the 5-7 micron region, as line shapes in the wing regions of water vapor lines are difficult to characterize. The measurements are required for air pollution studies using a CO laser, to find the differential absorption at the wavelengths in question due to atmospheric constituents other than water vapor. The design and performance of the optoacoustical detector are presented. Effects of absorption by ambient NO are considered, and the fixed-frequency discretely tunable CO laser is found suitable for monitoring urban NO concentrations in a fairly dry climate, using the water vapor absorption data obtained in the study.

  20. Dichroic atomic vapor laser lock with multi-gigahertz stabilization range

    NASA Astrophysics Data System (ADS)

    Pustelny, S.; Schultze, V.; Scholtes, T.; Budker, D.

    2016-06-01

    A dichroic atomic vapor laser lock (DAVLL) system exploiting buffer-gas-filled millimeter-scale vapor cells is presented. This system offers similar stability as achievable with conventional DAVLL system using bulk vapor cells, but has several important advantages. In addition to its compactness, it may provide continuous stabilization in a multi-gigahertz range around the optical transition. This range may be controlled either by changing the temperature of the vapor or by application of a buffer gas under an appropriate pressure. In particular, we experimentally demonstrate the ability of the system to lock the laser frequency between two hyperfine components of the 85Rb ground state or as far as 16 GHz away from the closest optical transition.

  1. Probing temperature during laser spot welding from vapor composition and modeling

    NASA Astrophysics Data System (ADS)

    He, X.; DebRoy, T.; fürschbach, P. W.

    2003-11-01

    Measurement of weld pool temperature during laser spot welding is a difficult task because of the short pulse duration, often lasting only a few milliseconds, highly transient nature of the process, and the presence of a metal vapor plume near the weld pool. This article describes recent research to estimate weld pool temperatures experimentally and theoretically. Composition of the metal vapor from the weld pool was determined by condensing a portion of the vapor on the inner surface of an open ended quartz tube which was mounted perpendicular to the sample surface and coaxial with the laser beam. It was found that iron, chromium, and manganese were the main metallic species in the vapor phase. The concentrations of Fe and Cr in the vapor increased slightly while the concentration of Mn in the vapor decreased somewhat with the increase in power density. The vapor composition was used to determine an effective temperature of the weld pool. A transient, three-dimensional numerical heat transfer and fluid flow model based on the solution of the equations of conservation of mass, momentum and energy was used to calculate the temperature and velocity fields in the weld pool as a function of time. The experimentally determined geometry of the spot welds agreed well with that determined from the computed temperature field. The effective temperature determined from the vapor composition was found to be close to the numerically computed peak temperature at the weld pool surface. Because of the short process duration and other serious problems in the direct measurement of temperature during laser spot welding, estimating approximate values of peak temperature from metal vapor composition is particularly valuable.

  2. Laser-induced fluorescence studies of polycyclic aromatic hydrocarbons (PAH) vapors at high temperatures.

    PubMed

    Chi, Z; Cullum, B M; Stokes, D L; Mobley, J; Miller, G H; Hajaligol, M R; Vo-Dinh, T

    2001-06-01

    In this work, we present the fluorescence spectra of anthracene and pyrene vapors at different elevated temperatures (from 150 to 650 degrees C) excited with the 337 nm line of a nitrogen laser. We describe the high temperature effects on the resulting spectral properties including spectral intensity, spectral bandwidth and spectral shift. We found that the PAH fluorescence spectral bandwidths become very broad as the temperature increases. The broadening is mainly due to thermal vibrational sequence congestion. We also have found that the fluorescence intensity of pyrene vapor increases with increasing temperature, which results from the increase of the pyrene vapor absorption cross section at 337 nm. PMID:11446693

  3. Development of Field-deployable Diode-laser-based Water Vapor Dial

    NASA Astrophysics Data System (ADS)

    Pham Le Hoai, Phong; Abo, Makoto; Sakai, Tetsu

    2016-06-01

    In this paper, a field-deployable diode-laser-based differential absorption lidar (DIAL) has been developed for lower-tropospheric water vapor observation in Tokyo, Japan. A photoacoustic cell is used for spectroscopy experiment around absorption peaks of 829.022 nm and 829.054 nm. The water vapor density extracted from the observational data agrees with the referenced radiosonde data. Furthermore, we applied modulated pulse technique for DIAL transmitter. It enables DIAL to measure water vapor profile for both low and high altitude regions.

  4. Nano structured physical vapor deposited coatings by means of picosecond laser radiation.

    PubMed

    Bobzin, K; Bagcivan, N; Ewering, M; Gillner, A; Beckemper, S; Hartmann, C; Theiss, S

    2011-10-01

    Molding of nano structures by injection molding leads to special requirements for the tools e.g., wear resistance and as low as possible release forces of the molded components. On the other hand it is not allowed to affect the replication precision. Physical vapor deposition is one of the promising technologies for applying coatings with adapted properties like high hardness, low roughness, low Young's modulus and less adhesion to the plastics melt. Although physical vapor deposition technology allows the deposition of films on micro structures without changing the structure significantly, film deposition on nano structures and small micro structures leads to a relevant change in surface topography. For this reason direct structuring of physical vapor deposition coatings might be beneficial. In this paper structuring was done using a picoseconds ultraviolet laser, Lumera Laser "Rapid," with a master oscillator power amplifier system at 355 nm. Two different coatings were deposited by magnetron sputter ion plating physical vapor deposition technology for laser structuring tests ((Cr, Al)N, (Cr, Al,Si)N). After deposition, the coatings were analyzed by common techniques regarding hardness, Young's modulus and morphology. The structures were analyzed by scanning electron microscopy. The results show a high potential for laser structuring of coatings deposited via physical vapor deposition. Linear structures with sizes between 400 nm and 10microm were realized. PMID:22400258

  5. Containerless laser-induced flourescence study of vaporization and optical properties for sapphire and alumina

    NASA Technical Reports Server (NTRS)

    Nordine, Paul C.; Schiffman, Robert A.

    1988-01-01

    Evaporation of aluminum oxide was studied from 1800 to 2327 K by laser-induced flourescence (LIF) detection of Al atom vapor over sapphire and alumina spheres that were levitated in an argon gas jet and heated with a continuous wave CO2 laser. Optical properties were determined from apparent specimen temperatures measured with an optical pyrometer and true temperatures deduced from the LIF intensity versus temperature measurements using the known temperature dependence of the Al atom vapor concentration in equilibrium with Al2O3. The effects of impurities and dissolved oxygen on the high-temperature optical properties of aluminum oxide were discussed.

  6. Investigation of SRS conversion of XeCl laser emission in lead vapor, methane, and hydrogen

    SciTech Connect

    Mel'chenko, S.V.; Panchenko, A.N.; Tarasenko, V.F.; Evtushenko, G.S. )

    1994-01-01

    The rapid advances in the development of electric-discharge exciplex lasers and powerful effective sources of UV coherent radiation have uncovered far-reaching prospects for their practical use in various fields of sciences and engineering, such as microelectronics, medicine, ecology (remote detection of contamination in the atmosphere), photochemistry, plasma diagnostics, and others. The wavelength range in which high-power coherent radiation is possible can be greatly expanded by using stimulated Raman scattering (SRS) in metal vapor and compressed gases. This paper is devoted to an investigation of the optimal conditions of SRS-conversion of XeCl-laser emission in lead vapor, methane, and hydrogen.

  7. Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment

    NASA Astrophysics Data System (ADS)

    Joulaei, A.; Moody, J.; Berti, N.; Kasparian, J.; Mirzanejhad, S.; Muggli, P.

    2016-09-01

    We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment.

  8. Electron collisions with cesium atoms—benchmark calculations and application to modeling an excimer-pumped alkali laser

    NASA Astrophysics Data System (ADS)

    Zatsarinny, Oleg; Bartschat, Klaus; Babaeva, Natalia Yu; Kushner, Mark J.

    2014-06-01

    The B-spline R-matrix (BSR) with pseudostates method is employed to describe electron collisions with cesium atoms. Over 300 states are kept in the close-coupling expansion, including a large number of pseudostates to model the effect of the Rydberg spectrum and, most importantly, the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, momentum transfer, excitation and ionization are presented for incident energies up to 200 eV and compared with results from previous calculations and available experimental data. In a second step, the results are used to model plasma formation in an excimer-pumped alkali laser operating on the Cs (62P3/2,1/2 → 62S1/2) (852 nm and 894 nm) transitions. At sufficiently high operating temperature of a Cs-Ar containing quartz cell, pump power, and repetition rate, plasma formation in excess of 1014-1015 cm-3 occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels.

  9. Localized planarization of optical damage using laser-based chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Matthews, Manyalibo J.; Elhadj, Selim; Guss, Gabe M.; Sridharan, Arun; Nielsen, Norman D.; Yoo, Jae-Hyuck; Lee, Daeho; Grigoropoulos, Costas

    2013-11-01

    We present a method to repair damaged optics using laser-based chemical vapor deposition (L-CVD). A CO2 laser is used to heat damaged silica regions and polymerize a gas precursor to form SiO2. Measured deposition rates and morphologies agree well with finite element modeling of a two-phase reaction. Along with optimizing deposition rates and morphology, we also show that the deposited silica is structurally identical to high-grade silica substrate and possesses high UV laser damage thresholds. Successful application of such a method could reduce processing costs, extend optic lifetime, and lead to more damage resistant laser optics used in high power applications.

  10. Measurement method for the nuclear anapole moment of laser-trapped alkali-metal atoms

    SciTech Connect

    Gomez, E.; Aubin, S.; Sprouse, G. D.; Orozco, L. A.; DeMille, D. P.

    2007-03-15

    Weak interactions within a nucleus generate a nuclear spin dependent, parity-violating electromagnetic moment, the anapole moment. We analyze a method to measure the nuclear anapole moment through the electric dipole transition it induces between hyperfine states of the ground level. The method requires tight confinement of the atoms to position them at the antinode of a standing wave Fabry-Perot cavity driving the anapole-induced microwave E1 transition. We explore the necessary limits in the number of atoms, excitation fields, trap type, interrogation method, and systematic tests necessary for such measurements in francium, the heaviest alkali.

  11. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, Sheldon H. D.

    1992-01-01

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases.

  12. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, S.H.D.

    1992-12-22

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases. 6 figs.

  13. Radial distribution of radiation in a CuBr vapor brightness amplifier used in laser monitors

    NASA Astrophysics Data System (ADS)

    Gubarev, F. A.; Trigub, M. V.; Klenovskii, M. S.; Li, Lin; Evtushenko, G. S.

    2016-01-01

    The paper presents a study of the effect of excitation conditions in a CuBr vapor brightness amplifier in a monostatic laser monitor on the radial non-uniformity of the radiation bearing the information about the object being visualized. A significant dependence of radial signal distribution on the concentrations of CuBr, HBr and pumping power has been demonstrated. In particular, an increase in CuBr vapor concentration causes the gain profile of the active medium to constrict and the axial gain to increase. The conditions for the most uniform radial distribution of the laser monitor signal are substantially different from those for the maximum radiated power. The paper demonstrates HBr doping to be usable as a tool to correct the non-uniformity of the radial distribution of laser monitor radiation. An addition of ~0.15 Torr HBr broadens and flattens the radiation profile, improving an important aspect of laser monitor image quality.

  14. Laser vaporization in treatment of superficial endometriosis of the uterine cervix

    NASA Astrophysics Data System (ADS)

    Wozniak, Jakub; Wilczak, Maciej; Opala, Tomasz; Pisarska-Krawczyk, Magdalena; Cwojdzinski, Marek; Pisarski, Tadeusz

    1996-03-01

    The study shows the treatment of superficial endometriosis of the uterine cervix in 79 patients. After first vaporization 74 patients were cured successfully. In two cases the laser procedure should be repeated and in 3 women the operation should be performed for the third time. All patients are still under control in our department and there is no recurrence observed. Carbon- dioxide laser vaporization under colposcopic control is an efficient method of treatment of superficial endometriosis of the uterine cervix that requires no anaesthesia. The healing process after laser procedures is fast and without complications. The number of recurrences is low. Use of carbon-dioxide laser under colposcopic control because of precise destruction of lesions, fast healing and a low number of recurrences seems to be the method of choice.

  15. Chemical speciation in laser-desorption and impact-induced vapor in minerals

    NASA Astrophysics Data System (ADS)

    Shen, A. H.; Dundas, C. M.; Ahrens, T. J.; Beauchamp, J. L.

    2002-12-01

    Knowledge of the chemical species in vapors produced by hypervelocity impact on spacecraft impact detectors as well as planetary surfaces have applications ranging from determination of the composition of cosmic dust to the effects on atmospheres and climates of large impactors. Direct study of resulting atomic, molecular and ionic species is best accomplished via mass spectrometry. Pulsed laser desorption can be used to approximate small impacts on solid surfaces. We conducted pulsed laser desorption-ionization experiments using two different instruments: (1) a Caltech-built Time-of-Flight Mass Spectrometer (TOFMS) similar to that on board the Cassini spacecraft and (2) a commercial Matrix Assisted Laser Desorption Ionization TOFMS made by Applied Biosystems (Model, Voyager-DE Pro). Minerals included in this study were calcite, dolomite, gypsum, anhydrite, olivine, kamacite, brucite, serpentine, and pyrrhotite. We collected only positive ions. A nitrogen laser (337 nm wavelength, 4 μsec pulse width, and 300 mJ) with power density ranging from 1.0x107 to 1.3x109 W/cm2 induced vaporization and ionization. The results can be summarized as: (1) from kamacite and pyrrhotite, only 54Fe+, 56Fe+, 57Fe+ (both kamacite and pyrrhotite) and 58Ni+, 60Ni+ (kamacite only) as well as contamination ions such as 23Na+ and 39K+, 41K+were observed; (2) Ca-containing minerals (calcite, dolomite, gypsum and anhydrite) produced vapors containing 40Ca+ ions, and, at higher laser power, both 40Ca+ as well as CaO+ ions; (3) Mg-containing minerals (dolomite, olivine, brucite and serpentine) produced vapors containing MgO+ ion; (4) for all hydrous minerals, neither H+ nor H3O+ were observed in the vapor; (5) in the vapors of silicate minerals (olivine and serpentine), SiO+ was observed only from serpentine but not from olivine.

  16. Interaction of wide band gap single crystals with 248 nm excimer laser radiation. XII. The emission of negative atomic ions from alkali halides

    SciTech Connect

    Kimura, Kenichi; Langford, S. C.; Dickinson, J. T.

    2007-12-01

    Many wide band gap materials yield charged and neutral emissions when exposed to sub-band-gap laser radiation at power densities below the threshold for optical breakdown and plume formation. In this work, we report the observation of negative alkali ions from several alkali halides under comparable conditions. We observe no evidence for negative halogen ions, in spite of the high electron affinities of the halogens. Significantly, the positive and negative alkali ions show a high degree of spatial and temporal overlap. A detailed study of all the relevant particle emissions from potassium chloride (KCl) suggests that K{sup -} is formed by the sequential attachment of two electrons to K{sup +}.

  17. Copper vapor laser machining of polyimide and polymethylmethacrylate in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Ventzek, P. L. G.; Gilgenbach, R. M.; Ching, C. H.; Lindley, R. A.; McColl, W. B.

    1992-10-01

    A repetitively pulsed copper vapor laser (510 and 578 nm) is used to machine an opaque polymer (polyimide-Vespel) and a transparent polymer (polymethylmethacrylate-Lucite). Lucite is machinable by coating the surface with an ink which is semi-opaque to the green and yellow laser light. The repetition rate of the laser was 10 kHz with approximately 0.35 mJ/pulse and 3.5 W average power at the copper vapor laser wavelengths for a pulse width of 40 ns. The copper vapor laser thermally loads the target, generating thermal waves and sound waves in the gas which are investigated using HeNe laser beam deflection. The gas adjacent to the target is heated to steady state on the order of 100-400 s. Above the etching threshold, at approximately 10 mJ/cm2/pulse, the target is rapidly machined: 2-mm-diam, 2-mm-deep holes are drilled in 300 s in Vespel. At higher fluences of 100-150 mJ/cm2/pulse in 760 Torr of air it takes 180 s to bore through a 2-mm-thick disk of Vespel. The machined surfaces of the two polymers are very different. Machined Vespel samples are charred and cratered, whereas the Lucite samples show evidence of melting with little charring. The machining of polymers by visible-light copper vapor lasers is being compared to UV photoablation by KrF excimer laser light in order to study thermal versus nonthermal etching mechanisms.

  18. Buffer gas effects on output power of a copper vapor laser

    NASA Astrophysics Data System (ADS)

    Behrouzinia, S.; Khorasani, K.; Farahmandjou, M.

    2016-05-01

    A copper vapor laser with an active medium length of 60 cm and bore of 16 mm was operated and optimized using different buffer gases to investigate the effect of pressure and gas flow rates on the laser output power. It was shown that a special interval of operational pressure and an optimum gas flow rate associated with the type of buffer gas were obtained.

  19. Spectral control of an alexandrite laser for an airborne water-vapor differential absorption lidar system

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Grossmann, Benoist E.; Browell, Edward V.

    1994-01-01

    A narrow-linewidth pulsed alexandrite laser has been greatly modified for improved spectral stability in an aircraft environment, and its operation has been evaluated in the laboratory for making water-vapor differential absorption lidar measurements. An alignment technique is described to achieve the optimum free spectral range ratio for the two etalons inserted in the alexandrite laser cavity, and the sensitivity of this ratio is analyzed. This technique drastically decreases the occurrence of mode hopping, which is commonly observed in a tunable, two-intracavity-etalon laser system. High spectral purity (greater than 99.85%) at 730 nm is demonstrated by the use of a water-vapor absorption line as a notch filter. The effective cross sections of 760-nm oxygen and 730-nm water-vapor absorption lines are measured at different pressures by using this laser, which has a finite linewidth of 0.02 cm(exp -1) (FWHM). It is found that for water-vapor absorption linewidths greater than 0.04 cm(exp -1) (HWHM), or for altitudes below 10 km, the laser line can be considered monochromatic because the measured effective absorption cross section is within 1% of the calculated monochromatic cross section. An analysis of the environmental sensitivity of the two intracavity etalons is presented, and a closed-loop computer control for active stabilization of the two intracavity etalons in the alexandrite laser is described. Using a water-vapor absorption line as a wavelength reference, we measure a long-term frequency drift (approximately 1.5 h) of less than 0.7 pm in the laboratory.

  20. Probing laser induced metal vaporization by gas dynamics and liquid pool transport phenomena

    SciTech Connect

    DebRoy, T.; Basu, S.; Mundra, K. )

    1991-08-01

    During laser beam welding of many important engineering alloys, an appreciable amount of alloying element vaporization takes place from the weld pool surface. As a consequence, the composition of the solidified weld pool is often significantly different from that of the alloy being welded. Currently there is no comprehensive theoretical model to predict, from first principles, laser induced metal vaporization rates and the resulting weld pool composition changes. The weld pool heat transfer and fluid flow phenomena have been coupled with the velocity distribution functions of the gas molecules at various locations above the weld pool to determine the rates of the laser induced element vaporization for pure metals. The procedure allows for calculations of the condensation flux based on the equations of conservation of mass, momentum and energy in both the vapor and the liquid phases. Computed values of the rates of vaporization of pure metals were found to be in good agreement with the corresponding experimentally determined values. The synthesis of the principles of gas dynamics and weld pool transport phenomena can serve as a basis for weld metal composition control.

  1. Micro-ablation with high power pulsed copper vapor lasers.

    PubMed

    Knowles, M

    2000-07-17

    Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser. PMID:19404369

  2. Ablation of biological tissues by radiation of strontium vapor laser

    SciTech Connect

    Soldatov, A. N. Vasilieva, A. V.

    2015-11-17

    A two-stage laser system consisting of a master oscillator and a power amplifier based on sources of self- contained transitions in pairs SrI and SrII has been developed. The radiation spectrum contains 8 laser lines generating in the range of 1 – 6.45 μm, with a generation pulse length of 50 – 150 ns, and pulse energy of ∼ 2.5 mJ. The divergence of the output beam was close to the diffraction and did not exceed 0.5 mrad. The control range of the laser pulse repetition rate varied from 10 to 15 000 Hz. The given laser system has allowed to perform ablation of bone tissue samples without visible thermal damage.

  3. Ablation of biological tissues by radiation of strontium vapor laser

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Vasilieva, A. V.

    2015-11-01

    A two-stage laser system consisting of a master oscillator and a power amplifier based on sources of self- contained transitions in pairs SrI and SrII has been developed. The radiation spectrum contains 8 laser lines generating in the range of 1 - 6.45 μm, with a generation pulse length of 50 - 150 ns, and pulse energy of ˜ 2.5 mJ. The divergence of the output beam was close to the diffraction and did not exceed 0.5 mrad. The control range of the laser pulse repetition rate varied from 10 to 15 000 Hz. The given laser system has allowed to perform ablation of bone tissue samples without visible thermal damage.

  4. Alkali metal ionization detector

    DOEpatents

    Bauerle, James E.; Reed, William H.; Berkey, Edgar

    1978-01-01

    Variations in the conventional filament and collector electrodes of an alkali metal ionization detector, including the substitution of helical electrode configurations for either the conventional wire filament or flat plate collector; or, the substitution of a plurality of discrete filament electrodes providing an in situ capability for transferring from an operationally defective filament electrode to a previously unused filament electrode without removing the alkali metal ionization detector from the monitored environment. In particular, the helical collector arrangement which is coaxially disposed about the filament electrode, i.e. the thermal ionizer, provides an improved collection of positive ions developed by the filament electrode. The helical filament design, on the other hand, provides the advantage of an increased surface area for ionization of alkali metal-bearing species in a monitored gas environment as well as providing a relatively strong electric field for collecting the ions at the collector electrode about which the helical filament electrode is coaxially positioned. Alternatively, both the filament and collector electrodes can be helical. Furthermore, the operation of the conventional alkali metal ionization detector as a leak detector can be simplified as to cost and complexity, by operating the detector at a reduced collector potential while maintaining the sensitivity of the alkali metal ionization detector adequate for the relatively low concentration of alkali vapor and aerosol typically encountered in leak detection applications.

  5. Laser Desorption of Explosives Traces with Low Vapors Pressure

    NASA Astrophysics Data System (ADS)

    Akmalov, A. E.; Chistyakov, A. A.; Kotkovskii, G. E.

    In this work comparison of the desorption effectiveness of picosecond and nanosecond laser sources (λ = 266, 532 nm) were carried out to investigate the possibility of creating a non-contact sampling device for detectors of explosives on the principles of ion mobility spectrometry (IMS) and field asymmetric ion mobility spectrometry (FAIMS). The results of mass spectrometric studies of TNT (2,4,6-Trinitrotoluene), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (1,3,5-Trinitro-1,3,5-triazacyclohexane) laser desorption from a quartz substrate are presented. It is shown that the most effective laser source is a Nd:YAG3+ laser (λ = 266 nm; E = 1 mJ; τ = 5-10 ns; q = 108 W/cm2). The typical desorbed mass is 2 ng for RDX, 4-6 ng for TNT and 0.02 ng HMX per single laser pulse. The results obtained make it possible to create a non-contact portable laser sampling device operating in frequency mode with high efficiency.

  6. Single Frequency, Pulsed Laser Diode Transmitter for Dial Water Vapor Measurements at 935nm

    NASA Technical Reports Server (NTRS)

    Switzer, Gregg W.; Cornwell, Donald M., Jr.; Krainak, Michael A.; Abshire, James B.; Rall, Johnathan A. R.

    1998-01-01

    We report a tunable, single frequency, narrow linewidth, pulsed laser diode transmitter at 935.68nm for remote sensing of atmospheric water vapor. The transmitter consists of a CW, tunable, external cavity diode laser whose output is amplified 2OdB using a tapered diode amplifier. The output is pulsed for range resolved DIAL lidar by pulsing the drive current to the diode amplifier at 4kHz with a .5% duty cycle. The output from the transmitter is 36OnJ/pulse and is single spatial mode. It maintains a linewidth of less than 25MHz as its wavelength is tuned across the water vapor absorption line at 935.68nm. The transmitter design and its use in a water vapor measurement will be discussed.

  7. Multi-wavelength metal vapor laser systems for solving applied problems of atmospheric spectroscopy

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Mirza, S. Y.; Polunin, Yu. P.; Shumeiko, A. S.; Kostadinov, I. K.

    2015-11-01

    Results of a cycle of experimental investigations of a multi-wavelength metal vapor laser system based on original configuration of a multi-medium metal vapor laser source are presented. Novelty of our approach consists in that two gas-discharge active elements (on copper bromide and strontium vapors) are arranged in a common cavity, and each of them is pumped by an independent power supply unit, which allows them to be optimized independently for excitation conditions and thereby the output set of lasing wavelengths and their relative power distribution to be regulated. This makes the above-described system promising for a number of scientific and technological applications. The total output power of 11 spectral components lying in the range 0.43-6.45 μm reached ~17 W.

  8. Modeling CO{sub 2} laser ablation impulse of polymers in vapor and plasma regimes

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.

    2009-09-28

    An improved model for CO{sub 2} laser ablation impulse in polyoxymethylene and similar polymers is presented that describes the transition effects from the onset of vaporization to the plasma regime in a continuous fashion. Several predictions are made for ablation behavior.

  9. Chemical vapor synthesis of nanocrystalline perovskites using laser flash evaporation of low volatility solid precursors

    NASA Astrophysics Data System (ADS)

    Winterer, Markus; Srdic, Vladimir V.; Djenadic, Ruzica; Kompch, Alexander; Weirich, Thomas E.

    2007-12-01

    One key requirement for the production of multinary oxide films by chemical vapor deposition (CVD) or nanocrystalline multinary oxides particles by chemical vapor synthesis (CVS) is the availability of precursors with high vapor pressure. This is especially the case for CVS where much higher production rates are required compared to thin films prepared by CVD. However, elements, which form low valent cations such as alkaline earth metals, are typically only available as solid precursors of low volatility, e.g., in form of β-diketonates. This study describes laser flash evaporation as precursor delivery method for CVS of nanocrystalline perovskites. Laser flash evaporation exploits the nonequilibrium evaporation of solid metal organic precursors of low vapor pressure by absorption of the infrared radiation of a CO2 laser. It is shown that stoichiometric, nanocrystalline particles consisting of SrZrO3 and SrTiO3 can be formed from corresponding mixtures of β-diketonates which are evaporated nonselectively and with high rates by laser flash evaporation.

  10. Chemical vapor synthesis of nanocrystalline perovskites using laser flash evaporation of low volatility solid precursors.

    PubMed

    Winterer, Markus; Srdic, Vladimir V; Djenadic, Ruzica; Kompch, Alexander; Weirich, Thomas E

    2007-12-01

    One key requirement for the production of multinary oxide films by chemical vapor deposition (CVD) or nanocrystalline multinary oxides particles by chemical vapor synthesis (CVS) is the availability of precursors with high vapor pressure. This is especially the case for CVS where much higher production rates are required compared to thin films prepared by CVD. However, elements, which form low valent cations such as alkaline earth metals, are typically only available as solid precursors of low volatility, e.g., in form of beta-diketonates. This study describes laser flash evaporation as precursor delivery method for CVS of nanocrystalline perovskites. Laser flash evaporation exploits the nonequilibrium evaporation of solid metal organic precursors of low vapor pressure by absorption of the infrared radiation of a CO(2) laser. It is shown that stoichiometric, nanocrystalline particles consisting of SrZrO(3) and SrTiO(3) can be formed from corresponding mixtures of beta-diketonates which are evaporated nonselectively and with high rates by laser flash evaporation. PMID:18163736

  11. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  12. High-power high-repetition-rate copper-vapor-pumped dye laser

    SciTech Connect

    Singh, S.; Dasgupta, K.; Kumar, S.; Manohar, K.G.; Nair, L.G.; Chatterjee, U.K. . Laser and Plasma Technology Div.)

    1994-06-01

    The design and development of an efficient high average power dye laser oscillator-amplifier system developed at the Laser and Plasma Technology Division, Bhabha Atomic Research Centre, is reported. The dye laser is pumped by a 6.5-kHz repetition rate copper vapor laser. The signal beam to the dye amplifier is obtained from an efficient narrow-band grazing incidence grating (GIG) dye laser oscillator incorporating a multiple prism beam expander. Amplifier extraction efficiency up to 40% was obtained in a single amplifier stage, using rhodamine 6G (Rh6G) in ethanol. The authors have also demonstrated simultaneous amplification of two laser beams at different wavelengths in the same dye amplifier cell.

  13. Signal correlation in the tandem of a spin oscillator and microwave frequency discriminator with laser-pumped alkali atoms

    NASA Astrophysics Data System (ADS)

    Baranov, A. A.; Ermak, S. V.; Sagitov, E. A.; Smolin, R. V.; Semenov, V. V.

    2016-02-01

    We have studied the influence of low-frequency noise on the stability of resonance frequency of a self-oscillating magnetometer on 87Rb vapor with simultaneous monitoring of the signal of radio-optical resonance on the magnetic-field-dependent microwave transition under laser pumping at the D 2 line of the head doublet. The difference of synchronous records of detected signals reduced to the same scale in magnetic field units was processed to determine the Allan variance as a function of the averaging time. The correlation coefficient characterizing the coupling of detected signals determined by the pumping rate and intensity of radio fields generated in the region of the absorption chamber. The self-oscillating magnetometer can only operate provided that there is laser tuning to the long-wavelength component of the electric-dipole transition.

  14. A tunable MWIR laser remote sensor for chemical vapor detection

    NASA Astrophysics Data System (ADS)

    Bunn, Thomas L.; Noblett, Patricia M.; Otting, William D.

    1998-01-01

    The Air Force vision for Global Virtual Presence suggests a need for active remote sensing systems that provide both global coverage and the ability to detect multiple gaseous chemical species at low concentration from a significant standoff distance. The system will need to have acceptable weight, volume, and power characteristics, as well as a long operating lifetime for integration with various surveillance platforms. Laser based remote sensing systems utilizing the differential absorption lidar (DIAL) technique are promising for long range chemical sensing applications. Recent advancements in pulsed, diode pumped solid state laser (DPSSL) technology and in tunable optical parametric oscillators (OPO) make broadly tunable laser transmitters possible for the DIAL system. Also the characteristic narrow spectral bandwidth of these laser devices provides high measurement sensitivity and spectral selectivity with the potential to avoid interfering species. Rocketdyne has built and tested a tunable, midwave infrared (MWIR) DIAL system using DPSSL/OPO technology. The key to the system is a novel tuning and line narrowing technology developed for the OPO. The tuning system can quickly adjust to the desired wavelength and precisely locate a narrow spectral feature of interest. Once the spectral feature is located, a rapid dither tuning technique is employed. The laser pulses are tuned ``on'' and ``off'' the spectral resonance of a molecule with precise and repeatable performance as required to make the DIAL measurement. To date, the breadboard system has been tested by measuring methane, ethane, and sulfur dioxide in a calibrated gas cell at a range of 60 meters.

  15. Laser surface modification of electroplated, physically vapor deposited and plasma sprayed coatings

    SciTech Connect

    Dini, J.W.

    1996-05-01

    Lasers are used to modify surface characteristics in order to improve properties for a variety of industrial applications. Typical surface alterations include: transformation hardening, melting, cladding, alloying, coating, and smoothing. This paper is a critical review that covers surface alloying. It concentrates on coatings applied by electroplating, plasma spraying or physical vapor deposition and the resultant properties obtained after laser treatment. In many cases, significant improvement in properties such as corrosion resistance, wear resistance, creep strength, porosity, and structure was noted after coatings were exposed to a laser treatment. 112 refs., 12 figs., 4 tabs.

  16. A new mass spectrometer system for investigating laser-induced vaporization phenomena

    NASA Technical Reports Server (NTRS)

    Lincoln, K. A.

    1974-01-01

    A laser has been combined with a mass spectrometer in a new configuration developed for studies of high-temperature materials. A vacuum-lock, solid-sample inlet is mounted at one end of a cylindrical, high-vacuum chamber one meter in length with a nude ion-source, time-of-flight mass spectrometer at the opposite end. The samples are positioned along the axis of the chamber at distances up to one meter from the ion source, and their surfaces are vaporized by a pulsed laser beam entering via windows on one side of the chamber. The instrumentation along with its capabilities is described, and results from laser-induced vaporization of several graphites are presented.

  17. Perspectives of transurethral robotic laser resection of the prostate: vaporization and coagulation effects with the Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Ho, Gideon; Teo, Ming Y.; Kwoh, Chee K.; Ng, Wan S.; Cheng, Wai S.

    2000-05-01

    A longer operating time and steeper learning curve in mastering the techniques for transurethral laser resection of the prostate are the main problems faced by surgeons compared to standard transurethral resection of the prostate (TURP). However, these disadvantages can be solved with the introduction of a treatment modality designed and developed based on an integrated system of computer, robotics and laser technology. In vitro experiments were carried out to determine variables affecting the vaporization and coagulation lesions, in order to identify the parameters that could optimize this modality. Human cadaveric prostate and fresh chicken breast tissues were irradiated with different parameters using continuous wave Nd:YAG laser fiber in contact with the tissue. The effects of irrigant flowrate, fiber/tissue angle of inclination, number of passes, direction, speed and power of lase on the volume of tissue vaporized and coagulated, were assessed. A non-contact optical coordinate measuring machine was used to measure the depth and width of the vaporized and coagulated lesion. Results reveal that for each directional vaporization path (forward, clockwise and counter-clockwise), power and speed of lase are the most significant parameters influencing the volume of the vaporized and coagulated lesion. Optimized values of the power and speed of lase at 100 W and 1 - 3 mm/s respectively were obtained from the experiments when the tissues were irradiated in the forward, clockwise and counter-clockwise directions. It was concluded from our study to quantify tissue removal and damage, optimized values of irradiation power and speed could be obtained and implemented in the procedure of transurethral robotic laser resection of the prostate.

  18. Infectious papillomavirus in the vapor of warts treated with carbon dioxide laser or electrocoagulation: Detection and protection

    SciTech Connect

    Sawchuk, W.S.; Weber, P.J.; Lowy, D.R.; Dzubow, L.M.

    1989-07-01

    Papillomavirus DNA has been reported recently in the vapor (smoke plume) derived from warts treated with carbon dioxide laser; this raises concerns for operator safety. We therefore have studied a group of human and bovine warts to define further the potential risk of wart therapy and to test whether a surgical mask could reduce exposure. Half of each wart was treated with carbon dioxide laser and the other half with electrocoagulation. The vapor produced by each form of therapy was collected with a dry filter vacuum apparatus and analyzed for the presence of papillomavirus. Vapor from human plantar warts was analyzed for the presence of human papillomavirus DNA, because there is no infectivity assay for human papillomavirus. Of plantar warts treated, five of eight laser-derived vapors and four of seven electrocoagulation-derived vapors were positive for human papillomavirus DNA. Greater amounts of papillomavirus DNA were usually recovered in the laser vapor than in the electrocoagulation vapor from the same wart. Bioassay readily detected infectious bovine papillomavirus in the vapor from bovine warts treated with either modality; more virus was present in laser-derived material. A surgical mask was found capable of removing virtually all laser- or electrocoagulation-derived virus, strongly suggesting that such masks can protect operators from potential inhalation exposure to papillomavirus.

  19. Delay of explosive vaporization in pulsed laser-heated droplets.

    PubMed

    Park, B S; Biswas, A; Armstrong, R L; Pinnick, R G

    1990-02-15

    Measurements of time delays for explosion of pulsed CO(2) laser-heated droplets are presented. A simple model based on classical nucleation theory in superheated liquids, which neglects heat and mass transport, is used to interpret the data. The model shows good agreement with the experimental observations. PMID:19759758

  20. Spectral characteristics of a ternary-mixture of dyes in a dye laser pumped by copper vapor laser

    NASA Astrophysics Data System (ADS)

    Khare, R.; Shukla, P. K.; Shrivastava, V. K.; Nakhe, S. V.

    2014-02-01

    The spectral characteristics of a ternary-mixture, composed of Rhodamine 640, Rhodamine 6G and DCM in ethanol and excited by copper vapor laser, are reported. The concentration of each dye in the ternary-mixture was optimized to provide peak emission at 633 nm and absorb both wavelengths of copper vapor laser, i.e. 510.6 and 578.2 nm. A fluorescence range of 612-679 nm with a relatively broad peak at 631-634 nm was obtained when concentrations of Rhodamine 640, Rhodamine 6G and DCM in the ternary-mixture were 0.90 mM, 0.30 mM and 0.90 mM respectively. This ternary-mixture of dyes in ethanol, when used as a gain medium in a narrowband, tunable dye laser oscillator, transversely pumped by both wavelengths of a copper vapor laser, provided a spectral tuning range of 620-665 nm with an almost flat peak at 630-634 nm.

  1. Laser light routing in an elongated micromachined vapor cell with diffraction gratings for atomic clock applications

    PubMed Central

    Chutani, Ravinder; Maurice, Vincent; Passilly, Nicolas; Gorecki, Christophe; Boudot, Rodolphe; Abdel Hafiz, Moustafa; Abbé, Philippe; Galliou, Serge; Rauch, Jean-Yves; de Clercq, Emeric

    2015-01-01

    This paper reports on an original architecture of microfabricated alkali vapor cell designed for miniature atomic clocks. The cell combines diffraction gratings with anisotropically etched single-crystalline silicon sidewalls to route a normally-incident beam in a cavity oriented along the substrate plane. Gratings have been specifically designed to diffract circularly polarized light in the first order, the latter having an angle of diffraction matching the (111) sidewalls orientation. Then, the length of the cavity where light interacts with alkali atoms can be extended. We demonstrate that a longer cell allows to reduce the beam diameter, while preserving the clock performances. As the cavity depth and the beam diameter are reduced, collimation can be performed in a tighter space. This solution relaxes the constraints on the device packaging and is suitable for wafer-level assembly. Several cells have been fabricated and characterized in a clock setup using coherent population trapping spectroscopy. The measured signals exhibit null power linewidths down to 2.23 kHz and high transmission contrasts up to 17%. A high contrast-to-linewidth ratio is found at a linewidth of 4.17 kHz and a contrast of 5.2% in a 7-mm-long cell despite a beam diameter reduced to 600 μm. PMID:26365754

  2. Laser light routing in an elongated micromachined vapor cell with diffraction gratings for atomic clock applications.

    PubMed

    Chutani, Ravinder; Maurice, Vincent; Passilly, Nicolas; Gorecki, Christophe; Boudot, Rodolphe; Abdel Hafiz, Moustafa; Abbé, Philippe; Galliou, Serge; Rauch, Jean-Yves; de Clercq, Emeric

    2015-01-01

    This paper reports on an original architecture of microfabricated alkali vapor cell designed for miniature atomic clocks. The cell combines diffraction gratings with anisotropically etched single-crystalline silicon sidewalls to route a normally-incident beam in a cavity oriented along the substrate plane. Gratings have been specifically designed to diffract circularly polarized light in the first order, the latter having an angle of diffraction matching the (111) sidewalls orientation. Then, the length of the cavity where light interacts with alkali atoms can be extended. We demonstrate that a longer cell allows to reduce the beam diameter, while preserving the clock performances. As the cavity depth and the beam diameter are reduced, collimation can be performed in a tighter space. This solution relaxes the constraints on the device packaging and is suitable for wafer-level assembly. Several cells have been fabricated and characterized in a clock setup using coherent population trapping spectroscopy. The measured signals exhibit null power linewidths down to 2.23 kHz and high transmission contrasts up to 17%. A high contrast-to-linewidth ratio is found at a linewidth of 4.17 kHz and a contrast of 5.2% in a 7-mm-long cell despite a beam diameter reduced to 600 μm. PMID:26365754

  3. Laser light routing in an elongated micromachined vapor cell with diffraction gratings for atomic clock applications

    NASA Astrophysics Data System (ADS)

    Chutani, Ravinder; Maurice, Vincent; Passilly, Nicolas; Gorecki, Christophe; Boudot, Rodolphe; Abdel Hafiz, Moustafa; Abbé, Philippe; Galliou, Serge; Rauch, Jean-Yves; de Clercq, Emeric

    2015-09-01

    This paper reports on an original architecture of microfabricated alkali vapor cell designed for miniature atomic clocks. The cell combines diffraction gratings with anisotropically etched single-crystalline silicon sidewalls to route a normally-incident beam in a cavity oriented along the substrate plane. Gratings have been specifically designed to diffract circularly polarized light in the first order, the latter having an angle of diffraction matching the (111) sidewalls orientation. Then, the length of the cavity where light interacts with alkali atoms can be extended. We demonstrate that a longer cell allows to reduce the beam diameter, while preserving the clock performances. As the cavity depth and the beam diameter are reduced, collimation can be performed in a tighter space. This solution relaxes the constraints on the device packaging and is suitable for wafer-level assembly. Several cells have been fabricated and characterized in a clock setup using coherent population trapping spectroscopy. The measured signals exhibit null power linewidths down to 2.23 kHz and high transmission contrasts up to 17%. A high contrast-to-linewidth ratio is found at a linewidth of 4.17 kHz and a contrast of 5.2% in a 7-mm-long cell despite a beam diameter reduced to 600 μm.

  4. Laser photoacoustic detection of the essential oil vapors of thyme, mint, and anise

    NASA Astrophysics Data System (ADS)

    El-Kahlout, A. M.; Al-Jourani, M. M.; Abu-Taha, M. I.; Laine, Derek C.

    1998-07-01

    Photoacoustic studies of the vapors of the essential oils of thyme, mint and anise have been made using a line-tunable waveguide CO2 laser in conjunction with a heat-pipe type of photoacoustic vapor sample cell operated over the temperature range 20 - 180 degree(s)C. Identifying spectral fingerprint features are found in the 9 - 10 micrometers spectral region for each of the three essential oils investigated. The principal features of the photoacoustic spectrum of each essential oil are associated with the dominant chemicals present i.e. thymol in thyme oil, menthol in mint and anethole in anise.

  5. Atomic vapor laser isotope separation of lead-210 isotope

    DOEpatents

    Scheibner, Karl F.; Haynam, Christopher A.; Johnson, Michael A.; Worden, Earl F.

    1999-01-01

    An isotopically selective laser process and apparatus for removal of Pb-210 from natural lead that involves a one-photon near-resonant, two-photon resonant excitation of one or more Rydberg levels, followed by field ionization and then electrostatic extraction. The wavelength to the near-resonant intermediate state is counter propagated with respect to the second wavelength required to populate the final Rydberg state. This scheme takes advantage of the large first excited state cross section, and only modest laser fluences are required. The non-resonant process helps to avoid two problems: first, stimulated Raman Gain due to the nearby F=3/2 hyperfine component of Pb-207 and, second, direct absorption of the first transition process light by Pb-207.

  6. Atomic vapor laser isotope separation of lead-210 isotope

    DOEpatents

    Scheibner, K.F.; Haynam, C.A.; Johnson, M.A.; Worden, E.F.

    1999-08-31

    An isotopically selective laser process and apparatus for removal of Pb-210 from natural lead that involves a one-photon near-resonant, two-photon resonant excitation of one or more Rydberg levels, followed by field ionization and then electrostatic extraction. The wavelength to the near-resonant intermediate state is counter propagated with respect to the second wavelength required to populate the final Rydberg state. This scheme takes advantage of the large first excited state cross section, and only modest laser fluences are required. The non-resonant process helps to avoid two problems: first, stimulated Raman Gain due to the nearby F=3/2 hyperfine component of Pb-207 and, second, direct absorption of the first transition process light by Pb-207. 5 figs.

  7. Modeling of laser-analyte-substrate interaction in photo-thermal infrared imaging and laser trace vaporization

    NASA Astrophysics Data System (ADS)

    Furstenberg, Robert; Großer, Jakob; Kendziora, Christopher A.; Papantonakis, Michael R.; Nguyen, Viet; McGill, R. Andrew

    2011-05-01

    We are developing two techniques for non-contact detection of explosives and other substances with low vapor pressure. In one approach, quantum cascade lasers (QCLs) at eye-safe power levels heat trace residues on surfaces at stand-off distances and the photo-thermal signal is imaged with an infrared camera. When using wavelengths corresponding to vibrational resonances specific to the trace molecules, the traces can be selectively heated and become visible in the infrared. In a second approach, a QCL or other IR laser of higher power is used to enhance the vapor signature of the analyte, thus facilitating vapor-based (e.g. ion mobility spectrometry) techniques. Details and advances in these techniques will be reported elsewhere. In this paper, we study the laser heating of analytes on substrates using the simulation software COMSOL. A model is validated with experimental results for particles of well characterized shape and size. The heat transfer between particle and substrate is of special interest, but not necessarily the dominant contributor to heat loss. Both air- and substrate-mediated heating of neighboring interferent particles is generally negligible. The presence of neighboring explosives particles affects the thermal kinetics via air-mediated heat transfer.

  8. Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

    SciTech Connect

    Tsai, C.

    1981-11-01

    Safety analyses of nuclear reactors require knowledge of the evaporation behavior of UO/sub 2/ at temperatures well above the melting point of 3140 K. In this study, rapid transient heating of a small spot on a UO/sub 2/ specimen was accomplished by a laser pulse, which generates a surface temperature excursion. This in turn vaporizes the target surface and the gas expands into vacuum. The surface temperature transient was monitored by a fast-response automatic optical pyrometer. The maximum surface temperatures investigated range from approx. 3700 K to approx. 4300 K. A computer program was developed to simulate the laser heating process and calculate the surface temperature evolution. The effect of the uncertainties of the high temperature material properties on the calculation was included in a sensitivity study for UO/sub 2/ vaporization. The measured surface temperatures were in satisfactory agreements.

  9. Upper Tropospheric and Lower Stratospheric Measurements of Water Vapor by the JPL Laser Hygrometer Mark 2

    NASA Astrophysics Data System (ADS)

    Troy, R. F.

    2015-12-01

    The concentration of water vapor in the upper troposphere and lower stratosphere has a significant impact on climate. Over the last sixteen years, the JPL Laser Hygrometers have collected a significant data record of atmospheric humidity from several platforms, including the NASA ER-2, WB-57, DC-8, and Global Hawk. Here, we describe the observed relation between atmospheric humidity and temperature in-cloud and out of cloud near the tropopause. The relation between cloud microphysical properties and humidity is also explored. We feature measurements of water vapor from a substantially improved instrument, JPL Laser Hygrometer Mark 2, made during the 2013 NASA SEAC4RS (Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys) field mission.

  10. Photodynamic therapy with gold vapor laser in the treatment of bladder cancer

    NASA Astrophysics Data System (ADS)

    Zhu, Qing; Zhang, Hui-Guo; Lu, Mei-er; Zhu, Bang-ji; Dai, Shen-guo; Jiang, Yu; Wu, Jia-Jun

    1993-03-01

    Vhe paper reports that 149 bladder tumors in 40 patients were treated by gold vapor laser photodynamic therapy in the period from June 1989 to August 1991. The light fiber output power of gold vapor laser is more than 2 W, that spread through a spherical diffuse light leading fiber. Focusing the irradiation on the tumor and the whole bladder the power density was 70.77 mw/cm2 to approximately 509.55 mw/cm2. After a follow-up of 4 to 24 months we found the following results: cured 28 cases (70%); good effect in 11 cases (27.5%); improved 1 case (2.5%); and regenerated 4 (10%).

  11. High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media

    NASA Astrophysics Data System (ADS)

    Todt, Michael A.; Albert, Daniel R.; Davis, H. Floyd

    2016-06-01

    A method is described for generating intense pulsed vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) laser radiation by resonance enhanced four-wave mixing of commercial pulsed nanosecond lasers in laser vaporized mercury under windowless conditions. By employing noncollinear mixing of the input beams, the need of dispersive elements such as gratings for separating the VUV/XUV from the residual UV and visible beams is eliminated. A number of schemes are described, facilitating access to the 9.9-14.6 eV range. A simple and convenient scheme for generating wavelengths of 125 nm, 112 nm, and 104 nm (10 eV, 11 eV, and 12 eV) using two dye lasers without the need for dye changes is described.

  12. Optical emission spectroscopy of metal vapor dominated laser-arc hybrid welding plasma

    SciTech Connect

    Ribic, B.; DebRoy, T.; Burgardt, P.

    2011-04-15

    During laser-arc hybrid welding, plasma properties affect the welding process and the weld quality. However, hybrid welding plasmas have not been systematically studied. Here we examine electron temperatures, species densities, and electrical conductivity for laser, arc, and laser-arc hybrid welding using optical emission spectroscopy. The effects of arc currents and heat source separation distances were examined because these parameters significantly affect weld quality. Time-average plasma electron temperatures, electron and ion densities, electrical conductivity, and arc stability decrease with increasing heat source separation distance during hybrid welding. Heat source separation distance affects these properties more significantly than the arc current within the range of currents considered. Improved arc stability and higher electrical conductivity of the hybrid welding plasma result from increased heat flux, electron temperatures, electron density, and metal vapor concentrations relative to arc or laser welding.

  13. Thin-layer chromatography combined with diode laser thermal vaporization inductively coupled plasma mass spectrometry.

    PubMed

    Bednařík, Antonín; Tomalová, Iva; Kanický, Viktor; Preisler, Jan

    2014-10-17

    Here we present a novel coupling of thin-layer chromatography (TLC) to diode laser thermal vaporization inductively coupled plasma mass spectrometry (DLTV ICP MS). DLTV is a new technique of aerosol generation which uses a diode laser to induce pyrolysis of a substrate. In this case the cellulose stationary phase on aluminum-backed TLC sheets overprinted with black ink to absorb laser light. The experimental arrangement relies on economic instrumentation: an 808-nm 1.2-W continuous-wave infrared diode laser attached to a syringe pump serving as the movable stage. Using a glass tubular cell, the entire length of a TLC separation channel is scanned. The 8-cm long lanes were scanned in ∼35 s. The TLC - DLTV ICP MS coupling is demonstrated on the separation of four cobalamins (hydroxo-; adenosyl-; cyano-; and methylcobalamin) with limits of detection ∼2 pg and repeatability ∼15% for each individual species. PMID:25193171

  14. High-power copper vapor lasers and their application to precision drilling and cutting

    SciTech Connect

    Warner, B.E.; Weber, P.D.

    1993-07-27

    High-power copper vapor lasers (CVLs) have been under development at Lawrence Livermore National Laboratory (LLNL) for more than 15 years in support of the DOE`s Program in Laser Isotope Separation. The technology is now quite mature, having met many of its goals in system architecture, power, reliability, and maintainability. Over the past several years we have begun an effort to utilize this technology in other industrial applications, such as metals processing, and have found a number of unique processes. In this paper we describe briefly the general characteristics of the CVL, our recent progress in developing the laser as an industrial tool, and our progress in using the laser in precision drilling and cutting.

  15. Production of pulsed atomic oxygen beams via laser vaporization methods

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Coulter, Daniel R.; Liang, Ranty H.; Gupta, Amitava

    1986-01-01

    The generation of energetic pulsed atomic oxygen beams by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin indium-tin oxide (ITO) films is reported. Mass spectroscopy is used in the mass and energy characterization of beams from the ozone/oxygen films, and a peak flux of 3 x 10 to the 20th/sq m per sec at 10 eV is found. Analysis of the time-of-flight data suggests that several processes contribute to the formation of the oxygen beam. Results show the absence of metastable states such as the 2p(3)3s(1)(5S) level of atomic oxygen blown-off from the ITO films. The present process has application to the study of the oxygen degradation problem of LEO materials.

  16. Laser/Plasma/Chemical-Vapor Deposition Of Diamond

    NASA Technical Reports Server (NTRS)

    Hsu, George C.

    1989-01-01

    Proposed process for deposition of diamond films includes combination of plasma induced in hydrocarbon feed gas by microwave radiation and irradiation of plasma and substrate by lasers. Deposition of graphite suppressed. Reaction chamber irradiated at wavelength favoring polymerization of CH2 radical into powders filtered out of gas. CH3 radicals, having desired sp3 configuration, remains in gas to serve as precursors for deposition. Feed gas selected to favor formation of CH3 radicals; candidates include CH4, C2H4, C2H2, and C2H6. Plasma produced by applying sufficient power at frequency of 2.45 GHz and adjusting density of gas to obtain electron kinetic energies around 100 eV in low-pressure, low-temperature regime.

  17. Modification and simulation of the power supply of a metal vapor laser

    NASA Astrophysics Data System (ADS)

    Ogorodnikov, D. N.; Trigub, M. V.; Torgaev, S. N.; Vasnev, N. A.; Evtushenko, T. G.

    2016-04-01

    The modification of a power supply circuit used for pumping metal vapor lasers is analyzed. The results of OrCAD simulation of the processes that occur in the power supply are presented. The effect of the capacitance ratio on the charging process of a storage capacitor is described. The mode which provides more time for the recovery of the thyratron is discussed. The results of the development of the small-size high pulse repetition frequency laser with up to 3 W average output power are presented.

  18. Spin-Exchange Optical Pumping of Alkali Salts

    NASA Astrophysics Data System (ADS)

    Olsen, Ben; Patton, Brian; Jau, Yuan-Yu; Happer, Will; Ishikawa, Kiyoshi

    2008-05-01

    Spin-Exchange Optical Pumping (SEOP) is a technique used to polarize nuclei in excess of their equilibrium limit. SEOP is achieved by optically pumping an alkali vapor which then transfers angular momentum to the nuclei of interest. We have recently hyperpolarized ^133Cs nuclei in solid CsH using SEOP, achieving magnetizations more than an order of magnitude larger than the thermal equilibrium value.ootnotetextIshikawa et. al., Phys. Rev. Lett. 98, 183004 (2007) In subsequent work, we investigate the mechanisms underlying this transfer of angular momentum. By optically pumping Cs vapor with laser light resonant with several optical transitions, each yielding different nuclear and electronic spin currents to the solid, we attempt to determine the source of transferred angular momentum. Early evidence suggests both electronic and nuclear spin polarization in the vapor contribute to ^133Cs nuclear polarization in the salt. The ^1H polarization is also mildly affected by optical pumping. We compare these results to numerical simulations and to results from other alkali salts. Further studies are warranted to discover if polarization can be transferred to other nuclei (e.g., alkali salts) on the cell walls.

  19. Numerical and experimental analysis of middle-bore copper-vapor laser discharge

    NASA Astrophysics Data System (ADS)

    Yu, Deli; Tao, Yongxiang; Yin, Xianhua; Chen, Lin; Yang, Yan; Li, Hailan; Wang, Runwen

    1998-08-01

    A single simulation model describing the discharge circuitry is introduced. First the differential equations are presented. In order to calculate the laser head discharge current, the thyratron resistance with a switching time coefficient (tau) s is investigated. The plasma conductivity used in these models is estimated using the available data on plasma parameters. Here 0.6 eV of the average electron temperature and 80 nH of thyratron inductance are assumed according to our previous model. The laser head discharge current of the differential equations is calculated with the method of Runge- Kutta. The discharge current profiles of the simulation are found to be in close agreement with the experimental data which come from 4.8-cm-diameter and 6.5-cm-diameter middle- bore Copper-Vapor Laser. In this way, the factors which effect the short rise time to increase lasing ability in the CVL (Copper-Vapor Laser) are studied on the bases of studying the storage capacitor's and the peaking capacitor's effect. As a calculation result, the inductance of the laser head takes an inferior effect to the thyratron circuit inductance on the discharge current rise time. Very good agreement exists between the calculated and measured results. This is a successful single discharge model.

  20. Synthesis of Cobalt Oxides Thin Films Fractal Structures by Laser Chemical Vapor Deposition

    PubMed Central

    Haniam, P.; Kunsombat, C.; Chiangga, S.; Songsasen, A.

    2014-01-01

    Thin films of cobalt oxides (CoO and Co3O4) fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures. PMID:24672354

  1. Synthesis of cobalt oxides thin films fractal structures by laser chemical vapor deposition.

    PubMed

    Haniam, P; Kunsombat, C; Chiangga, S; Songsasen, A

    2014-01-01

    Thin films of cobalt oxides (CoO and Co3O4) fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures. PMID:24672354

  2. Alkali metal for ultraviolet band-pass filter

    NASA Technical Reports Server (NTRS)

    Mardesich, Nick (Inventor); Fraschetti, George A. (Inventor); Mccann, Timothy A. (Inventor); Mayall, Sherwood D. (Inventor); Dunn, Donald E. (Inventor); Trauger, John T. (Inventor)

    1993-01-01

    An alkali metal filter having a layer of metallic bismuth deposited onto the alkali metal is provided. The metallic bismuth acts to stabilize the surface of the alkali metal to prevent substantial surface migration from occurring on the alkali metal, which may degrade optical characteristics of the filter. To this end, a layer of metallic bismuth is deposited by vapor deposition over the alkali metal to a depth of approximately 5 to 10 A. A complete alkali metal filter is described along with a method for fabricating the alkali metal filter.

  3. Production of pulsed atomic oxygen beams via laser vaporization methods

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Coulter, Daniel R.; Liang, Ranty H.; Gupta, Amitava

    1987-01-01

    Energetic pulsed atomic oxygen beams were generated by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin films of indium-tin oxide (ITO). Mass and energy characterization of beams from the ozone/oxygen films were carried out by mass spectrometry. The peak flux, found to occur at 10 eV, is estimated from this data to be 3 x 10(20) m(-2) s(-1). Analysis of the time-of-flight data indicates a number of processes contribute to the formation of the atomic oxygen beam. The absence of metastable states such as the 2p(3) 3s(1) (5S) level of atomic oxygen blown off from ITO films is supported by the failure to observe emission at 777.3 nm from the 2p(3) 3p(1) (5P sub J) levels. Reactive scattering experiments with polymer film targets for atomic oxygen bombardment are planned using a universal crossed molecular beam apparatus.

  4. Effect of surrounding gases and water vapor on the induced electric current associated with a laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Matsuta, Hideyuki

    2016-04-01

    The effect of surrounding gases and water vapor on the laser-induced electric current was investigated. Laser-induced plasma was generated on an aluminum alloy target. The laser-induced plasma was optically examined to estimate the excitation temperature and electron density in room air. There was a linear relationship between the maximum amplitude of the laser-induced current and the electron density. As the electron mean free path of the surrounding gas increased, the observed amplitude of the current increased. The amplitude of the induced current signal in dry air became maximum upon mixing with the optimum amount of water vapor. This enhancement of the induced current signal might be due to the large relative permittivity of water vapor. The laser-induced plasma as a whole seems to be a low-temperature plasma consisting of electrons, a large amount of cold surrounding gas, injected hot atoms, hot ions, and hot particles.

  5. Urethral stricture vaporization with the KTP laser provides evidence for a favorable impact of laser surgery on wound healing

    NASA Astrophysics Data System (ADS)

    Schmidlin, Franz R.; Venzi, Giordano; Jichlinski, Patrice; Oswald, Michael; Delacretaz, Guy P.; Gabbiani, Giulio; Leisinger, Hans-Juerg; Graber, Peter

    1997-12-01

    The objective of this study was to evaluate and compare the safety and efficacy of the KTP 532 laser to direct vision internal urethrotomy (DVIU) in the management of urethral strictures. A total of 32 patients were randomized prospectively in this study, 14 DVIU and 18 KTP 532 laser. Patients were evaluated postoperatively with flowmetry and in the case of recurrence with cystourethrography at 3, 12, 24 weeks. With the KTP 532 laser complete symptomatic and uredynamic success was achieved in 15 (83%) patients at 12 and 24 weeks. Success rate was lower in the DVIU group with 9 (64%) patients at 12 weeks and 8 (57%) patients at 24 weeks. Mean preoperative peak-flow was improved from 6 cc/s to 20 cc/s at 3, 12 and 24 weeks with the KTP laser. With DVIU mean preoperative peak-flow was improved from 5.5 cc/s to 20 cc/s at 3 weeks followed by a steady decrease to 13 cc/s at 12 weeks and to 12 cc/s 24 weeks. No complication was observed in either group of patients. Our results confirm that stricture vaporization with the KTP 532 laser is a safe and efficient procedure. The better results after laser surgery make it also a valuable alternative in the endoscopic treatment of urethral strictures. These findings suggest a favorable influence of laser surgery on wound healing with less wound contraction and scarring. The lack of contraction of laser wounds might be related to the absence and the lack of organization of myofibroblasts in laser induced lesions.

  6. Double resonance fequency light shift compensation in optically oriented laser-pumped alkali atoms

    SciTech Connect

    Baranov, A. A. Ermak, S. V.; Sagitov, E. A.; Smolin, R. V.; Semenov, V. V.

    2015-09-15

    The contributions of the vector and scalar components to the magnetically dependent microwave transition frequency light shift are analyzed and the compensation of these components is experimentally demonstrated for the {sup 87}Rb atoms optically oriented by a laser tuned to the D{sub 2} line of the head doublet. The Allan variance is studied as a function of the averaging time for a tandem of optically pumped quantum magnetometers (OPQMs), one of which is based on a low-frequency spin oscillator while another is based on a quantum microwave discriminator with a resonance frequency that corresponds to magnetically dependent transitions between HFS sublevels with the extremal value of the magnetic quantum number. It is shown that the compensation of the scalar and vector components of the light shift in OPQMs reduces the Allan variance at averaging times that exceed hundreds of seconds compared to a quantum discriminator based on the magnetically independent 0–0 transition. In this case, the minimal Allan variance in OPQMs at the end resonance is achieved at considerably longer averaging times than in the case of the quantum discriminator that is tuned to the 0–0 transition frequency.

  7. Subnatural linewidth in room-temperature Rb vapor using a control laser

    NASA Astrophysics Data System (ADS)

    Rapol, Umakant D.; Wasan, Ajay; Natarajan, Vasant

    2003-05-01

    We demonstrate two ways of obtaining subnatural linewidth for probe absorption through room-temperature Rb vapor. Both techniques use a control laser that drives the transition from a different ground state. The coherent drive splits the excited state into two dressed states (Autler-Townes doublet), which have asymmetric linewidths when the control laser is detuned from resonance. In the first technique, the laser has a large detuning of 1.18 GHz to reduce the linewidth to 5.1 MHz from the Doppler width of 560 MHz. In the second technique, we use a counterpropagating pump beam to eliminate the first-order Doppler effect. The unperturbed probe linewidth is about 13 MHz, which is reduced below 3 MHz (0.5Γ) at a detuning of 11.5 MHz.

  8. New multiplexed all solid state pulser for high power wide aperture kinetically enhanced copper vapor laser.

    PubMed

    Ghodke, D V; Muralikrishnan, K; Singh, Bijendra

    2013-11-01

    A novel multiplexed scheme is demonstrated to combine two or more pulsed solid state pulsers of moderate capabilities. Pulse power supply comprising of two solid state pulsers of ~6 kW rating each in multiplexed mode with common magnetic pulse compression stage was demonstrated and optimized for operating with a wide aperture kinetically enhanced copper vapor laser. Using this new configuration, the multiplexed pulsed power supply was capable of operating efficiently at net repetition-rate of ~13 kHz, 12 kW (wall plug average power), 18-20 kV discharge voltage and pulse rise-time of ~80 ns. The laser under multiplexed configuration delivered un-interrupted output power of about ~80 W with scope of further increase in laser output power in excess of 100 W. PMID:24289383

  9. Relationship between 578-nm (copper vapor) laser beam geometry and heat distribution within biological tissues

    NASA Astrophysics Data System (ADS)

    Ilyasov, Ildar K.; Prikhodko, Constantin V.; Nevorotin, Alexey J.

    1995-01-01

    Monte Carlo (MC) simulation model and the thermoindicative tissue phantom were applied for evaluation of a depth of tissue necrosis (DTN) as a result of quasi-cw copper vapor laser (578 nm) irradiation. It has been shown that incident light focusing angle is essential for DTN. In particular, there was a significant rise in DTN parallel to elevation of this angle up to +20 degree(s)C and +5 degree(s)C for both the MC simulation and tissue phantom models, respectively, with no further increase in the necrosis depth above these angles. It is to be noted that the relationship between focusing angles and DTN values was apparently stronger for the real target compared to the MC-derived hypothetical one. To what extent these date are applicable for medical practice can be evaluated in animal models which would simulate laser-assisted therapy for PWS or related dermatologic lesions with converged 578 nm laser beams.

  10. Differential absorption lidar measurements of atmospheric water vapor using a pseudonoise code modulated AlGaAs laser. Thesis

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.

    1994-01-01

    Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

  11. Elucidating the Structure of Sugars: MW Spectroscopy Combined with Ultrafast UV Laser Vaporization

    NASA Astrophysics Data System (ADS)

    Cocinero, Emilio J.; Ecija, Patricia; Basterretxea, Francisco J.; Fernandez, Jose A.; Castano, Fernando; Lesarri, Alberto; Grabow, Jens-Uwe; Cimas, Alvaro

    2013-06-01

    Carbohydrates are one of the most versatile biochemicalbuilding blocks, widely acting in energetic, structural or recognition processes. Even the small monosaccharides display unique structural and conformational freedom and may coexist in many open-chain or cyclic forms. We recently initiated the investigation of a series of monosaccharides using a combination of ultrafast laser vaporization and microwave spectroscopy in supersonic jet expansions. We present several structural studies on carbohydrates of aldoses and ketoses of five and six carbon sugars vaporized by UV ultrafast laser vaporization and stabilized in a jet expansion. The experimental evidence confirms that sugars exhibits a α-/β-pyranose conformation (6-membered ring), sharply contrasting with the furanose form (5-membered ring) found in the nature (as component of RNA, sucrose). In addition, thanks to the use of enriched samples, we have experimentally determined the substitution and effective structures. Finally, the structure of several monosaccharides was compared and common structural patterns of their conformational landscape will be showed. E. J. Cocinero, A. Lesarri, P. écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño Angew. Chem. Int. Ed. 51, 3119-3124, 2012. E. J. Cocinero, A. Lesarri, P. écija, Á. Cimas, B. G. Davis, F. J. Basterretxea, J. A. Fernández and F. Castaño J. Am. Chem. Soc. 135, 2845-2852, 2013.

  12. Physics of zinc vaporization and plasma absorption during CO{sub 2} laser welding

    SciTech Connect

    Dasgupta, A. K.; Mazumder, J.; Li, P.

    2007-09-01

    A number of mathematical models have been developed earlier for single-material laser welding processes considering one-, two-, and three-dimensional heat and mass transfers. However, modeling of laser welding of materials with multiple compositions has been a difficult problem. This paper addresses a specific case of this problem where CO{sub 2} laser welding of zinc-coated steel, commonly used in automobile body manufacturing, is mathematically modeled. The physics of a low boiling point material, zinc, is combined with a single-material (steel) welding model, considering multiple physical phenomena such as keyhole formation, capillary and thermocapillary forces, recoil and vapor pressures, etc. The physics of laser beam-plasma interaction is modeled to understand the effect on the quality of laser processing. Also, an adaptive meshing scheme is incorporated in the model for improving the overall computational efficiency. The model, whose results are found to be in close agreement with the experimental observations, can be easily extended for studying zinc-coated steel welding using other high power, continuous wave lasers such as Nd:YAG and Yb:YAG.

  13. Laser chemical vapor deposition of Cu and Ni in integrated circuit repair

    NASA Astrophysics Data System (ADS)

    Leppaevuori, Seppo; Remes, Janne; Moilanen, Hannu

    1996-09-01

    Laser-assisted chemical vapor deposition (LCVD) of nickel from Ni(CO)4 and copper from Cu(hfac)tmvs was utilized in the restructuring of an integrated circuit (IC) interconnection. Nickel and copper lines were deposited on passivated ICs by using a focused Ar+ laser beam to achieve new local rewirings on the chip. Nickel line depositions were carried out over the pressure range of 0.2 to 2.2 mbar of Ni(CO)4 buffered in 200 - 800 mbar He. The typical laser beam scan speed was 24 micrometers per second for both metals. The Cu(hfac)tmvs precursor gas partial pressure was 0.3 mbar buffered in 10 mbar He or H2 and typical laser scan speed was 24 micrometers per second. The morphology and chemical contents of the deposited interconnection microstructures was examined by atomic force microscopy (AFM), optical microscopy and laser ionization mass analysis (LIMA). The LIMA analysis indicated that the deposited copper surface was contaminated but the contamination level decreased when the layer was depth profiled. The deposited Ni lines were found to be pure Ni with only traces of carbon contamination. The utilization of XeCl excimer laser in the cutting of Al and Mo conductor lines and passivation contact via opening for IC modification is also described. LCVD method was successful in numerous different IC failure inspection and circuit modification cases.

  14. Reduction of degradation in vapor phase transported InP/InGaAsP mushroom stripe lasers

    SciTech Connect

    Jung, H.; Burkhardt, E.G.; Pfister, W.

    1988-10-03

    The rapid degradation rate generally observed in InP/InGaAsP mushroom stripe lasers can be considerably decreased by regrowing the open sidewalls of the active stripe with low-doped InP in a second epitaxial step using the hydride vapor phase transport technique. This technique does not change the fundamental laser parameters like light-current and current-voltage characteristics. Because of this drastic reduction in degradation, the vapor phase epitaxy regrown InP/InGaAsP mushroom laser seems to be an interesting candidate for application in optical communication.

  15. Theoretical studies of Resonance Enhanced Stimulated Raman Scattering (RESRS) of frequency-doubled Alexandrite laser wavelength in cesium vapor

    NASA Technical Reports Server (NTRS)

    Lawandy, Nabil M.

    1987-01-01

    The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for three different sets of relaxation rates. These rates correspond to: (1) Far Infrared (FIR) Raman lasers in the diabatic collision regime without consideration of coupled population decay in a closed system, (2) Raman FIR lasers in the diabatic collision regime with coupled population conserving decay, and (3) IR Raman gain in cesium vapor. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled Alexandrite laser-pumped cesium vapor gain cell.

  16. Gas phase versus surface contributions to photolytic laser chemical vapor deposition rates

    NASA Astrophysics Data System (ADS)

    Braichotte, D.; van den Bergh, H.

    1988-04-01

    The rate of cw photolytic laser chemical vapor deposition (LCVD) of platinum is measured for λ≈350 nm as a function of the light intensity and the metalorganic vapor pressure. The growth of the metal films is studied in situ and in real time by monitoring their optical transmission. At low intensities the transmitted light decreases monotonically with time, and the LCVD process is photolytic with its rate limiting step in the surface adlayer. At higher intensities we observe two distinct time domains: Relatively slow initial photolytic deposition with its rate limiting step in the gas phase, which is followed by much faster pyrolytic LCVD. An improved method for distinguishing between adlayer and gas-phase limiting processes is demonstrated. These observations are confirmed by studying the photolytic deposition rates while varying the thickness of the adlayer.

  17. Spectral and temporal features of the pumping of rhodamine 6G by radiation from a copper vapor laser

    SciTech Connect

    Soldatov, A.N.; Sukhanov, V.B.

    1983-01-01

    An experimental investigation was made of the influence of the relative delay time tau and of the intensity ratio R/sub 21/ of the spectral components emitted by a copper vapor laser on the energy and spectral characteristics of lasing in rhodamine 6G. For certain values of tau and P/sub 21/, lasing in the dye was disrupted. A clamping effect was discovered between the rhodamine 6G laser emission spectrum and the yellow line of the copper vapor laser. The results obtained were used to determine the parameters of an interference filter for suppressing the yellow line from the copper vapor laser, and this made it possible to raise the efficiency of conversion of the pump radiation into lasing in the dye.

  18. Carbon dioxide laser vaporization of the inferior turbinate for allergic rhinitis: short-term results.

    PubMed

    Imamura, Shun-ichi; Honda, Hideyuki

    2003-12-01

    Carbon dioxide laser vaporization of the turbinate has recently become accepted as a common treatment for allergic rhinitis. Usually, only a single procedure is applied to minimize trauma. However, repeated procedures on separate days are often required to achieve an adequate effect. Therefore, we attempted a new method of vaporization and evaluated the outcome, and also tried to determine which patients have good indications for laser treatment. To widely and deeply vaporize the inferior turbinate, we repeated the procedure 3 times in 1 session after removing the carbon coating from the previous vaporization under nasal endoscopic observation. After the procedure, most patients experienced complete nasal obstruction for 2 or 3 days, but there was no intraoperative or postoperative bleeding or severe pain. All patients obtained improvement of their chief complaints and were satisfied 2 months after the operation. In particular, 60% of the patients were completely relieved of refractory nasal obstruction. Most patients were more satisfied with the effects than are those treated by the usual methods. Completely successful cases (improvement in all symptoms and complete satisfaction obtained) were selected and were compared with other cases. Favorable prognostic factors are more severe complaints, longer symptomatic periods, stronger allergic reactions, and worse nasal resistance and its greater improvement with administration of decongestant nasal drops. This method may be especially accepted by patients with severe complaints, in particular nasal obstruction, who do not experience enough relief with conservative therapies or have enough time to make frequent visits to an outpatient clinic over a period of several weeks. PMID:14703108

  19. Evidence for two different shock induced high-pressure events and alkali-vapor metasomatism in Peace River and Tenham (L6) chondrites

    NASA Astrophysics Data System (ADS)

    El Goresy, A.; Wopenka, B.; Chen, M.; Weinbruch, S.; Sharp, T. G.

    1997-03-01

    Smooth grains in the Peace River shocked matrix previously described as maskelynite are not diaplectic glass but a crystalline phase with a stoichiometric composition. They formed upon decompression by inversion of a parental high-pressure polymorph that crystallized from a dense K-rich melt. They are surrounded by radiating cracks that have extensively shattered the neighboring minerals due to volume increase induced by decompression. Similar grains in Tenham turned out to be glass-quenched from a dense alkali-rich melt compositionally unrelated to plagioclase. Expansion of the alkali-bearing aluminosilicate in Peace River and the quenched dense glass in Tenham triggered the second high-pressure event. Neither Peace River nor Tenham contain any maskelynite.

  20. Short-term effects of extremely low-frequency pulsed electromagnetic field and pulsed low-level laser therapy on rabbit model of corneal alkali burn.

    PubMed

    Rezaei Kanavi, Mozhgan; Tabeie, Faraj; Sahebjam, Farzin; Poursani, Nima; Jahanbakhsh, Nazanin; Paymanpour, Pouya; AfsarAski, Sasha

    2016-04-01

    This study was conducted to investigate the effect of combining extremely low frequency-pulsed electromagnetic field (ELF-PEMF) and low-level laser therapy (LLLT) on alkali-burned rabbit corneas. Fifty alkali-burned corneas of 50 rabbits were categorized into five groups: ELF-PEMF therapy with 2 mT intensity (ELF 2) for 2 h daily; LLLT for 30 min twice daily; combined ELF-PEMF and LLLT (ELF + LLLT); medical therapy (MT); and control (i.e., no treatment). Clinical examination and digital photography of the corneas were performed on days 0, 2, 7, and 14. After euthanizing the rabbits, the affected eyes were evaluated by histopathology. The clinical and histopathologic results were compared between the groups. On days 7 and 14, no significant difference in the corneal defect area was evident between the ELF, LLLT, ELF + LLLT, and MT groups. Excluding the controls, none of the study groups demonstrated a significant corneal neovascularization in both routine histopathology and immunohistochemistry for CD31. Keratocyte loss was significantly higher in the MT group than in the ELF, LLLT, and ELF + LLLT groups. Moderate to severe stromal inflammation in the LLLT group was comparable with that in the MT group and was significantly lower than that in the other groups. In conclusion, combining LLLT and ELF was not superior to ELF alone or LLLT alone in healing corneal alkali burns. However, given the lower intensity of corneal inflammation and the lower rate of keratocytes loss with LLLT, this treatment may be superior to other proposed treatment modalities for healing alkali-burned corneas. PMID:26795389

  1. A single surgeon's experience with contact laser vaporization of the prostate

    NASA Astrophysics Data System (ADS)

    Mueller, Edward J.

    1995-05-01

    Herein, I report on my first 50 contact laser prostatectomies performed with the SLT Nd:YAG laser. The obstructed prostatic urethra is opened via contact laser vaporization of the obstructing adenoma. The average pre-op AUA symptom score was 22.9 (range 14 - 30). The average 3 month post-op AUA symptom score was 2.1 (range 0 -8). Eighteen of the patients had the foley catheter removed approximately 4 - 6 hours post-op and were discharged the same day. Thirty patients had the foley catheter removed the morning following surgery and were discharged. And two patients had the foley catheter removed the morning following surgery, but remained in the hospital for medical reasons unrelated to the TURP. Thus, 48 (96%) of the patients were discharged within 24 hours of admission. No patient had to be readmitted to the hospital for any reason. All patients were allowed to return to full activity within 24 hours of discharge. The average hospital cost for the 48 patients discharged within 24 hours was DOL4,694. This compares to the average hospital cost of an electrocautery TURP of DOL6-8000. In summary, contact laser TURP using the SLT Nd:YAG laser relived the symptoms of an obstructing prostate comparable to electrocautery TURP. However, these results were achieved with a much shorter hospitalization, a quicker return to full activity and at a lower cost.

  2. An investigation into the output characteristics of a discharge-heated copper vapor laser

    NASA Astrophysics Data System (ADS)

    Wang, Tieh C.; Yang, Ching Y.

    1989-11-01

    The laser output characteristics of a discharge-heated copper vapor laser (CVL) were investigated at a charging voltage of 14.5 kV, laser tube temperature of 1450 C, pulse repetition rate (PRR) range from 0.5 to 9.5 kHz, and buffer gas pressures of 20 and 75 Torr. Changing buffer gas pressure from 20 to 75 Torr causes no significant variation of the rates of relaxation of metastable atoms. Increase of the current rise of pumping pulse with increasing PRR is the predominant factor for improving the laser behavior when PRR is greater than 3.5 kHz with buffer gas pressure of 20 Torr and when PRR is less than 4.5 kHz with buffer gas pressure of 75 Torr. For short pulse applications, the CVL is preferably operated at high PRR and low buffer gas regime. For the 25-W CVL used here, the prepulse electron density should be higher than 10 to the 13th/cu cm for efficient laser operation. The output power of this CVL can be increased to much higher than 30 W if the thermal insulation is optimized and the PRR is increased.

  3. Schottky diodes and ohmic contacts formed by thermally assisted photolytic laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Braichotte, D.; van den Bergh, H.

    Thermally assisted photolytic laser chemical vapor deposition (LCVD) of platinum on n-doped gallium arsenide, a two-phase hybrid scheme for the production of Schottky diodes, is discussed. The low temperature photolytic deposits of the initial slow phase contain a nonnegligible fraction of organic ligand material and tend to be amorphous. In the second phase, light absorption of the photolytically deposited metal causes a temperature rise which facilitates the removal of ligand material from the deposit, and which is sufficient for fast pyrolytic LCVD. Measurements of the influence of light intensity, in addition to metalorganic and inert gas pressure, on the deposition rates in both phases are obtained.

  4. Fabrication of highly ultramicroporous carbon nanofoams by SF6-catalyzed laser-induced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hattori, Yoshiyuki; Shuhara, Ai; Kondo, Atsushi; Utsumi, Shigenori; Tanaka, Hideki; Ohba, Tomonori; Kanoh, Hirofumi; Takahashi, Kunimitsu; Vallejos-Burgos, Fernando; Kaneko, Katsumi

    2016-05-01

    We have developed a laser-induced chemical vapor deposition (LCVD) method for preparing nanocarbons with the aid of SF6. This method would offer advantages for the production of aggregates of nanoscale foams (nanofoams) at high rates. Pyrolysis of the as-grown nanofoams induced the high surface area (1120 m2 g-1) and significantly enhanced the adsorption of supercritical H2 (16.6 mg g-1 at 77 K and 0.1 MPa). We also showed that the pyrolized nanofoams have highly ultramicroporous structures. The pyrolized nanofoams would be superior to highly microporous nanocarbons for the adsorption of supercritical gases.

  5. Optimization of the alexandrite laser tuning elements for a water vapor lidar

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Grossmann, Benoist E.; Higdon, Noah S.; Browell, Edward V.

    1990-01-01

    An overview of some of the developments completed on an alexandrite laser for making water vapor DIAL measurements is presented in this paper. A computer control for active stabilization of the two intracavity etalons has been implemented and recently tested in an aircraft environment. Long-term frequency drift (i.e., 2 hours) of less than 0.7 pm has been observed in the laboratory. An alignment technique to get the optimum free spectral range ratio for the two etalons is also developed.

  6. Preliminary results on diode-laser assisted vaporization of prostate tissue

    NASA Astrophysics Data System (ADS)

    Sroka, Ronald; Seitz, Michael; Reich, Oliver; Bachmann, Alexander; Steinbrecher, Verena; Ackermann, Alexander; Stief, Christian

    2007-07-01

    Introduction and objectives: The aim was to identify the capability and the laser parameter of under water tissue vaporisation by means of a diode laser (1470 nm). Afterwards the feasibility and postoperative clinical outcome of vaporization of the prostate was investigated. Method: After acquiring suitable laser parameters in in-vitro experiments using a perfused tissue model patients (n=10) suffering from bladder outlet obstruction due to benign prostatic hyperplasia (BPH) were treated by diode laser. Their clinical outcome, in terms of acceptance and post-operatively voiding were evaluated. The diode laser emitted light of the wavelength of 1470 nm at 50 W (Biolitec GmbH) and delivered to the tissue by means of a side-fire fibre introduced through a 24F continuous-flow cystoscope. Normal saline was used for irrigation with an additive of 1% ethanol. The prostatic lobes (volume range 35-80ml) were vaporized within the prostatic capsular using sweeping and push and pull technique. The mean time of laser application was 2400 sec (1220-4000 sec) resulting in applied energies of 121 kJ in the mean (range: 61-200kJ). Results: During laser treatment none of the 10 patients showed any significant blood loss or any fluid absorption (no ethanol uptake). Foley catheters were removed between 18 and 168 hours postoperatively (mean: 49.8h+/-46h). After removal of the catheter the mean peak urine flow rate increased from 8.9ml/s +/- 2.9ml/s pre-operatively in comparison to 15.7ml/s +/- 5 ml/s (p=0.049) post-operatively. 8/10 patients were satisfied with their voiding outcome. None of the patients showed appearance of urgency, dysuria, hematuria, or incontinence but two patients required re-catheterization. After a follow-up of 1month, 8/10 patients showed evidence of good results and are satisfied with the outcome. Two patients required consecutive TUR-P. After a follow-up of 6-month the 8 patients are still satisfied. Conclusions: This very early and limited experience using

  7. Gas-dynamic acceleration of laser-ablation plumes: Hyperthermal particle energies under thermal vaporization

    SciTech Connect

    Morozov, A. A.; Evtushenko, A. B.; Bulgakov, A. V.

    2015-02-02

    The expansion of a plume produced by low-fluence laser ablation of graphite in vacuum is investigated experimentally and by direct Monte Carlo simulations in an attempt to explain hyperthermal particle energies for thermally vaporized materials. We demonstrate that the translation energy of neutral particles, ∼2 times higher than classical expectations, is due to two effects, hydrodynamic plume acceleration into the forward direction and kinetic selection of fast particles in the on-axis region. Both effects depend on the collision number within the plume and on the particles internal degrees of freedom. The simulations allow ablation properties to be evaluated, such as ablation rate and surface temperature, based on time-of-flight measurements. Available experimental data on kinetic energies of various laser-produced particles are well described by the presented model.

  8. Gas-dynamic acceleration of laser-ablation plumes: Hyperthermal particle energies under thermal vaporization

    NASA Astrophysics Data System (ADS)

    Morozov, A. A.; Evtushenko, A. B.; Bulgakov, A. V.

    2015-02-01

    The expansion of a plume produced by low-fluence laser ablation of graphite in vacuum is investigated experimentally and by direct Monte Carlo simulations in an attempt to explain hyperthermal particle energies for thermally vaporized materials. We demonstrate that the translation energy of neutral particles, ˜2 times higher than classical expectations, is due to two effects, hydrodynamic plume acceleration into the forward direction and kinetic selection of fast particles in the on-axis region. Both effects depend on the collision number within the plume and on the particles internal degrees of freedom. The simulations allow ablation properties to be evaluated, such as ablation rate and surface temperature, based on time-of-flight measurements. Available experimental data on kinetic energies of various laser-produced particles are well described by the presented model.

  9. Acoustic monitoring of carbon film formation by laser-induced chemical vapor deposition

    SciTech Connect

    Iida, Y.; Yeung, E.S. )

    1993-04-01

    Acoustic signals generated by the deposition of carbon thin films were monitored in situ by a microphone. Photolysis of benzene or adamantane vapor in the presence of helium buffer gas of 5 to 100 Torr by an ArF excimer laser formed several kinds of carbon films (e.g., polymeric, amorphous, and graphitic films), depending on the optical configuration, the ambient pressure, the laser fluence, and the reagent pressure. Analysis of the acoustic signal offers some insight into the mechanism of the deposition processes, which include the graphitization of the deposited films and the role of energetic particles, such as vibrationally excited benzene, in the deposition of amorphous hydrogenated carbon film. Also, the acoustic signal clearly showed the presence of surface-related processes in the course of film deposition. 26 refs., 6 figs., 1 tab.

  10. KTP laser selective vaporization of the prostate in the management of urinary retention due to BPH

    NASA Astrophysics Data System (ADS)

    Kleeman, M. W.; Nseyo, Unyime O.

    2003-06-01

    High-powered photoselective vaporization of the prostate (PVP) is a relatively new addition in the armamentarium against bladder outlet obstruction due to BPH. With BPH, the prostate undergoes stromal and epithelial hyperplasia, particularly in the transitional zone, mediated by dihydrotestosterone (DHT). This periurethral enlargement can compress the prostatic urethra leading to bladder outlet obstruction and eventually urinary retention. Treatment of uncomplicated symptomatic BPH has evolved from the standard transurethral resection of the prostate (TURP) to multiple medical therapies and the putative minimally invasive surgical procedures. These include microwave ablation, needle ablation, balloon dilation, stents, as well as fluid based thermo-therapy, ultrasound therapy and cryotherapy. Different forms of lasers have been applied to treat BPH with variable short and long term benefits of urinary symptoms. However, the controversy remains about each laser regarding its technical applicability and efficacy.

  11. Alkali-metal intercalation in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Béguin, F.; Duclaux, L.; Méténier, K.; Frackowiak, E.; Salvetat, J. P.; Conard, J.; Bonnamy, S.; Lauginie, P.

    1999-09-01

    We report on successful intercalation of multiwall (MWNT) and single wall (SWNT) carbon nanotubes with alkali metals by electrochemical and vapor phase reactions. A LiC10 compound was produced by full electrochemical reduction of MWNT. KC8 and CsC8-MWNT first stage derivatives were synthesized in conditions of alkali vapor saturation. Their identity periods and the 2×2 R 0° alkali superlattice are comparable to their parent graphite compounds. The dysonian shape of KC8 EPR line and the temperature-independent Pauli susceptibility are both characteristic of a metallic behavior, which was confirmed by 13C NMR anisotropic shifts. Exposure of SWNT bundles to alkali vapor led to an increase of the pristine triangular lattice from 1.67 nm to 1.85 nm and 1.87 nm for potassium and rubidium, respectively.

  12. Laser scattering diagnostics of an argon atmospheric-pressure plasma jet in contact with vaporized water

    NASA Astrophysics Data System (ADS)

    Seo, B. H.; Kim, J. H.; You, S. J.; Seong, D. J.

    2015-12-01

    The radial profiles of the electron density, electron temperature, and molecular rotational temperature are investigated in an argon atmospheric-pressure plasma jet in contact with vaporized water, which is driven by a 13.56 MHz radio frequency by means of the Thomson and Raman laser scattering methods. There is a distinct difference in the radial profiles of the plasma parameters between plasmas in contact with water and those without water contact. In the case of plasmas without vaporized water contact, all the parameters have a single-peak distribution with maximum values at the center of the discharge. In the case of plasmas in contact with vaporized water, all parameters have double-peak distributions; a neighboring peak appears beside the main peak. The new peak may have originated from the ripple of the water surface, which works as a cathode, and the peak of the ripple offers a sharp curvature point, playing the role of a pin. Our experimental results and the underlying physics are described in detail.

  13. Modeling of Laser Vaporization and Plume Chemistry in a Boron Nitride Nanotube Production Rig

    NASA Technical Reports Server (NTRS)

    Gnoffo, Peter A.; Fay, Catharine C.

    2012-01-01

    Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

  14. The melanosome: threshold temperature for explosive vaporization and internal absorption coefficient during pulsed laser irradiation.

    PubMed

    Jacques, S L; McAuliffe, D J

    1991-06-01

    The explosive vaporization of melanosomes in situ in skin during pulsed laser irradiation (pulse duration less than 1 microsecond) is observed as a visible whitening of the superficial epidermal layer due to stratum corneum disruption. In this study, the ruby laser (694 nm) was used to determine the threshold radiant exposure, H0 (J/cm2), required to elicit whitening for in vitro black (Negroid) human skin samples which were pre-equilibrated at an initial temperature, Ti, of 0, 20, or 50 degrees C. A plot of H0 vs Ti yields a straight line whose x-intercept indicates the threshold temperature of explosive vaporization to be 112 +/- 7 degrees C (SD, N = 3). The slope, delta H0/delta Ti, specifies the internal absorption coefficient, mua, within the melanosome: mua = -rho C/(slope(1 + 7.1 Rd)), where rho C is the product of density and specific heat, and Rd is the total diffuse reflectance from the skin. A summary of the absorption spectrum (mua) for the melanosome interior (351-1064 nm) is presented based on H0 data from this study and the literature. The in vivo absorption spectrum (380-820 nm) for human epidermal melanin was measured by an optical fiber spectrophotometer and is compared with the melanosome spectrum. PMID:1886936

  15. Kinetics of laser-pulse vaporization of uranium carbide by mass spectrometry. [LMFBR

    SciTech Connect

    Tehranian, F.

    1983-06-01

    The kinetics of uranium carbide vaporization in the temperature range 3000 K to 5200 K was studied using a Nd-glass laser with peak power densities from 1.6 x 10/sup 5/ to 4.0 x 10/sup 5/ watts/cm/sup 2/. The vapor species U, UC/sub 2/, C/sub 1/ and C/sub 3/ were detected and analyzed by a quadrupole mass spectrometer. From the mass spectrometer signals number densities of the various species in the ionizer were obtained as functions of time. The surface of the irradiated uranium carbide was examined by scanning electron microscope and the depth profile of the crater was obtained. In order to aid analysis of the data, the heat conduction and species diffusion equations for the solid (or liquid) were solved numerically by a computer code to obtain the temperature and composition transients during laser heating. A sensitivity analysis was used to study the effect of uncertainties in the input parameters on the computed surface temperatures.

  16. Alkali Bee

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The alkali bee, Nomia melanderi, is native to deserts and semi-arid desert basins of the western United States. It is a very effective and manageable pollinator for the production of seed in alfalfa (=lucerne) and some other crops, such as onion. It is the world’s only intensively managed ground-n...

  17. Critical Fluences And Modeling Of CO{sub 2} Laser Ablation Of Polyoxymethylene From Vaporization To The Plasma Regime

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.; Tsukiyama, Yosuke; Ogita, Naoya; Sasoh, Akihiro; Umehara, Noritsugu; Gregory, Don A.

    2010-05-06

    A CO{sub 2} laser was operated at pulse energies up to 10 J to ablate polyoxymethylene targets in air and vacuum conditions. Critical effects predicted by ablation models are discussed in relation to the experimental data, including specifically the threshold fluences for vaporization and critical plasma formation, and the fluence at which the optimal momentum coupling coefficient is found. Finally, we discuss a new approach for modeling polymers at long wavelengths, including a connection formula that links the vaporization and plasma regimes for laser ablation propulsion.

  18. Spectral diagnostics of a vapor-plasma plume produced during welding titanium with a high-power ytterbium fiber laser

    NASA Astrophysics Data System (ADS)

    Uspenskiy, S. A.; Petrovskiy, V. N.; Bykovskiy, D. P.; Mironov, V. D.; Prokopova, N. M.; Tret'yakov, E. V.

    2015-03-01

    This work is devoted to the research of welding plume during high power ytterbium fiber laser welding of a titanium alloy in the Ar shielding gas environment. High speed video observation of a vapor-plasma plume for visualization of processes occurring at laser welding was carried out. The coefficient of the inverse Bremsstrahlung absorption of laser radiation is calculated for a plasma welding plume by results of spectrometer researches. The conclusion deals with the impact of plasma on a high-power fiber laser radiation.

  19. Alkali metal sources for OLED devices

    NASA Astrophysics Data System (ADS)

    Cattaneo, Lorena; Longoni, Giorgio; Bonucci, Antonio; Tominetti, Stefano

    2005-07-01

    In OLED organic layers electron injection is improved by using alkali metals as cathodes, to lower work function or, as dopants of organic layer at cathode interface. The creation of an alkali metal layer can be accomplished through conventional physical vapor deposition from a heated dispenser. However alkali metals are very reactive and must be handled in inert atmosphere all through the entire process. If a contamination takes place, it reduces the lithium deposition rate and also the lithium total yield in a not controlled way. An innovative alkali metal dispensing technology has been developed to overcome these problems and ensure OLED alkali metal cathode reliability. The alkali Metal dispenser, called Alkamax, will be able to release up to a few grams of alkali metals (in particular Li and Cs) throughout the adoption of a very stable form of the alkali metal. Lithium, for example, can be evaporated "on demand": the evaporation could be stopped and re-activated without losing alkali metal yield because the metal not yet consumed remains in its stable form. A full characterization of dispensing material, dispenser configuration and dispensing process has been carried out in order to optimize the evaporation and deposition dynamics of alkali metals layers. The study has been performed applying also inside developed simulations tools.

  20. Internal Energy Deposition for Low Energy, Femtosecond Laser Vaporization and Nanospray Post-ionization Mass Spectrometry using Thermometer Ions

    NASA Astrophysics Data System (ADS)

    Flanigan, Paul M.; Shi, Fengjian; Archer, Jieutonne J.; Levis, Robert J.

    2015-05-01

    The internal energy of p-substituted benzylpyridinium ions after laser vaporization using low energy, femtosecond duration laser pulses of wavelengths 800 and 1042 nm was determined using the survival yield method. Laser vaporization of dried benzylpyridinium ions from metal slides into a buffered nanospray with 75 μJ, 800 nm laser pulses resulted in a higher extent of fragmentation than conventional nanospray due to the presence of a two-photon resonance fragmentation pathway. Using higher energy 800 nm laser pulses (280 and 505 μJ) led to decreased survival yields for the four different dried benzylpyridinium ions. Analyzing dried thermometer ions with 46.5 μJ, 1042 nm pulse-bursts resulted in little fragmentation and mean internal energy distributions equivalent to nanospray, which is attributable to the absence of a two-photon resonance that occurs with higher energy, 800 nm laser pulses. Vaporization of thermometer ions from solution with either 800 nm or 1042 nm laser pulses resulted in comparable internal energy distributions to nanospray ionization.

  1. Internal energy deposition for low energy, femtosecond laser vaporization and nanospray post-ionization mass spectrometry using thermometer ions.

    PubMed

    Flanigan, Paul M; Shi, Fengjian; Archer, Jieutonne J; Levis, Robert J

    2015-05-01

    The internal energy of p-substituted benzylpyridinium ions after laser vaporization using low energy, femtosecond duration laser pulses of wavelengths 800 and 1042 nm was determined using the survival yield method. Laser vaporization of dried benzylpyridinium ions from metal slides into a buffered nanospray with 75 μJ, 800 nm laser pulses resulted in a higher extent of fragmentation than conventional nanospray due to the presence of a two-photon resonance fragmentation pathway. Using higher energy 800 nm laser pulses (280 and 505 μJ) led to decreased survival yields for the four different dried benzylpyridinium ions. Analyzing dried thermometer ions with 46.5 μJ, 1042 nm pulse-bursts resulted in little fragmentation and mean internal energy distributions equivalent to nanospray, which is attributable to the absence of a two-photon resonance that occurs with higher energy, 800 nm laser pulses. Vaporization of thermometer ions from solution with either 800 nm or 1042 nm laser pulses resulted in comparable internal energy distributions to nanospray ionization. PMID:25724375

  2. Measurement of vapor/liquid distributions in a binary-component fuel spray using laser imaging of droplet scattering and vapor absorption

    NASA Astrophysics Data System (ADS)

    Li, Shiyan; Zhang, Yuyin; Wu, Shenqi; Xu, Bin

    2014-08-01

    Fuel volatility has a great effect on its evaporation processes and the mixture formation and thus combustion and emissions formation processes in internal combustion engines. To date, however, instead of the actual gasoline or diesel fuel, many researchers have been using single-component fuel in their studies, because the composition of the former is too complicated to understand the real physics behind the evaporation and combustion characteristics. Several research groups have reported their results on droplets evaporation in a spray of multi-component fuel, carried out both numerically and experimentally. However, there are plenty of difficulties in quantitative determination of vapor concentration and droplet distributions of each component in a multicomponent fuel spray. In this study, to determine the vapor phase concentration and droplet distributions in an evaporating binary component fuel spray, a laser diagnostics based on laser extinction by droplet scattering and vapor absorption was developed. In practice, measurements of the vapor concentration distributions of the lower (n-tridencane) and higher (n-octane) volatility components in the binary component fuel sprays have been carried out at ambient temperatures of 473K and 573K, by substituting p-xylene for noctane or α-methylnaphthalene for n-tridecane. p-Xylene and α-methylnaphthalene were selected as the substitutes is because they have strong absorption band near 266nm and transparent near 532nm and, their thermo-physical properties are similar to those of the original component. As a demonstration experiment, vapor/liquid distribution of the lower boiling point (LBP) and higher boiling point (HBP) components in the binary component fuel spray have been obtained.

  3. Efficient multiple time scale method for modeling compressible vapor plume dynamics inside transient keyhole during fiber laser welding

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Chen, Xin; Li, Wen; Shao, Xinyu; Gong, Shuili

    2016-03-01

    Efficient coupling modeling of multiple time scale interactions between keyhole, weld pool and compressible vapor plume during laser welding has long been limited. To address this problem, we present a highly efficient multiple time scale method combining a novel dual-time stepping and Ghost Fluid interpolation strategy with incompressible and compressible fluid solvers, which allows us predicting the compressible plume dynamics inside transient keyhole in fiber laser welding for the first time. In our method, the compressible dynamic vapor inside the transient keyhole is solved with a Roe scheme based algorithm and the incompressible molten liquid of weld pool is calculated by a Projection method. A novel temperature dependent boundary condition of vapor plume is also proposed for the consideration of the dynamic evaporation phenomena on the transient keyhole wall. It is found that the time dependent distributions of vapor plume characteristics, including temperature, pressure, velocity, density and Mach number distributions inside the transient keyhole induced by laser welding can be reasonably predicted by comparing to experimental and literature data. It is also shown that the proposed multiple time scale method is around 60 times faster than the vapor plume modeling method using a single nanosecond scale time step. For the vapor plume in a typical fiber laser welding process, the results indicate that the peak pressure can be greater than 2.0 atmospheric pressures; the average density is around 0.15-0.3 kg/m3 which is much smaller than the air density; and the local Mach number can be greater than 0.8 or even 1.0 Mach which demonstrates the necessity to treat the vapor plume as a compressible fluid.

  4. Dynamic characteristics and mechanisms of compressible metallic vapor plume behaviors in transient keyhole during deep penetration fiber laser welding

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Shao, Xinyu; Li, Wen; Chen, Xin; Gong, Shuili

    2016-07-01

    The compressible metallic vapor plume or plasma plume behaviors in the keyhole during deep penetration laser welding have significant effects on the joint quality. However, these behaviors and their responses to process parameter variations have not been well understood. In this paper, we first systematically study the dynamic characteristics and mechanisms of compressible metallic vapor plume behaviors in transient keyhole during fiber laser welding of 304 stainless steels based on a multiple timescale multiphase model. The time-dependent temperature, pressure, velocity and Mach number distributions of vapor plume under different process parameters are theoretically predicted. It is found that the distributions of the main physical characteristics of vapor plume such as pressure, velocity as well as Mach number in keyhole are usually highly uneven and highly time dependent. The peak difference of the velocity, pressure, temperature and Mach number of the vapor plume in a keyhole could be greater than 200 m/s, 20 kPa, 1000 K and 0.6 Mach, respectively. The vapor plume characteristics in a transient keyhole can experience significant changes within several hundreds of nanoseconds. The formation mechanisms of these dynamic characteristics are mainly due to the mesoscale keyhole hump (sized in several tens of microns) dynamics. It is also demonstrated that it is possible to suppress the oscillations of compressible vapor plume in the keyhole by improving the keyhole stability through decreasing the heat input. However, stabilizing the keyhole could only weaken, but not eliminate, the observed highly uneven and transient characteristics. This finding may pose new challenges for accurate experimental measurements of vapor plume induced by laser welding.

  5. Mid-IR laser absorption diagnostics for hydrocarbon vapor sensing in harsh environments

    NASA Astrophysics Data System (ADS)

    Klingbeil, Adam Edgar

    unburned fuel, engine performance can be characterized and future engine designs can be improved to utilize all of the fuel supplied to the engine. Simultaneous measurement of absorption at two wavelengths is used as a basis for hydrocarbon detection in severe environments. A novel wavelength-tunable mid-IR laser is modified to rapidly switch between two wavelengths, improving the versatility of this laser system. The two-wavelength technique is then exploited to measure vapor concentration while rejecting interferences such as scattering from liquid droplets and absorption from other species. This two-wavelength laser is also used to simultaneously determine temperature and vapor concentration. These techniques, in combination with the library of temperature-dependent hydrocarbon spectra, lay the groundwork necessary to develop fuel diagnostics for laboratory experiments and tests in pulse detonation engines and internal combustion engines. The temperature-dependent spectroscopy of gasoline is examined to develop a sensor for fuel/air ratio in an internal combustion engine. A wavelength was selected for good sensitivity to gasoline concentration. A spectroscopic model is developed that uses the relative concentrations of five structural classes to predict the absorption spectrum of gasoline samples with varying composition. The model is tested on 21 samples of gasoline for temperatures ranging from 300 to 1200 K, showing good agreement between model and measurements over the entire temperature range. Finally, a two-wavelength diagnostic was developed to measure the post-evaporation temperature and n-dodecane concentration in an aerosol-laden shock tube. The experimental data validate a model which calculates the effects of shock-wave compression on a two-phase mixture. The measured post-shock temperature and vapor concentration compare favorably for gas-phase and aerosol experiments. The agreement between the two fuel-loading techniques verifies that this aerosol shock

  6. High-speed microjet generation using laser-induced vapor bubbles

    NASA Astrophysics Data System (ADS)

    Oudalov, Nikolai; Tagawa, Yoshiyuki; Peters, Ivo; Visser, Claas-Willem; van der Meer, Devaraj; Prosperetti, Andrea; Sun, Chao; Lohse, Detlef

    2011-11-01

    The generation and evolution of microjets are studied both experimentally and numerically. The jets are generated by focusing a laser pulse into a microscopic capillary tube (~50 μm) filled with water-based red dye. A vapor bubble is created instantly after shooting the laser (<1 μs), sending out a shockwave towards the curved free surface at which the high-speed microjet forms. The process of jet formation is captured using high-speed recordings at 1.0 × 106 fps. The velocity of the microjets can reach speeds of ~850 m/s while maintaining a very sharp geometry. The high-speed recordings enable us to study the effect of several parameters on the jet velocity, e.g. the absorbed energy and the distance between the laser spot and the free surface.The results show a clear dependence on these variables, even for supersonic speeds. Comparisons with numerical simulations confirm the nature of these dependencies.

  7. Laser induced chemical vapor phase epitaxial growth of III-V semiconductor films

    NASA Astrophysics Data System (ADS)

    Chu, Shirley S.; Chu, Ting L.

    1991-05-01

    The objective of this project is to investigate the homo- and hetero-epitaxial growth of device quality III-V semiconductor films by the free electron laser (FEL) induced growth at lower temperatures. An ArF excimer laser was used in this investigation. Metalorganic vapor phase epitaxy (MOVPE) is the commonly used technique in the growth of III-V compounds and alloys. The major concern to the use of MOVPE is the hazard involved in using highly toxic arsine and phosphine gases as the group V source materials. Efforts during this period have been focused to the homoepitaxial growth of GaAs and heteroepitaxial growth of InP on GaAs using alternate sources to eliminate the use of arsine and phosphine. Good quality epitaxial GaAs films have been prepared from elemental arsenic for the first time by either conventional substrate heating or laser enhanced processes. The epitaxial GaAs films grown from elemental arsenic are suitable for many GaAs based devices, particularly for large area devices such as solar cells. Significant cost reduction and less stringent safety requirements are major advantages.

  8. High-speed photography of energetic materials and components with a copper vapor laser

    SciTech Connect

    Dosser, L.R.; Reed, J.W.; Stark, M.A.

    1988-01-01

    The evaluation of the properties of energetic materials, such as burn rate and ignition energy, is of primary importance in understanding their reactions and the functioning of devices containing them. One method for recording such information is high-speed photography at rates of up to 20,000 images per second. When a copper vapor laser is synchronized with the camera, laser-illuminated images can be recorded that detail the performance of a material and/or component in a manner never before possible. The laser can also be used for ignition of the energetic material, thus eliminating the need for bridgewires or electric squibs that can interfere with photography. Details of such ignitions are readily observable, and the burn rate of a material can be determined directly from the film. There are indications that information useful for the modeling of pyrotechnic reactions will become available as well. Recent results from high-speed photography of several pyrotechnic materials and devices will be presented. 9 figs.

  9. A three-beam water vapor sensor system for combustion diagnostics using a 1390 nm tunable diode laser

    SciTech Connect

    Wang, L.G.; Vay, S.

    1995-12-31

    H{sub 2}O(v) is an important species in combustion and hypersonic flow measurements because it is a primary combustion product. Measurements of water vapor can be used to determine performance parameters, such as extent and efficiency of combustion in propulsion and aerodynamics facilities. Water vapor concentration measurement in these high-temperature hypervelocity combustion conditions requires very high sensitivity and fast time response. A three-beam diode laser H{sub 2}O(v) measurement system for nonintrusive combustion diagnostics has been developed at NASA Langley Research Center and successfully tested and installed at GASL NASA HYPULSE facility for routine operation. The system was built using both direct laser absorption spectroscopy and frequency modulation laser spectroscopy. The output beam from a distributed feedback (DFB) InGaAsP diode laser (emitting around 1.39 {micro}m) is split into three equal-powered equal-distanced parallel beams with separation of 9 mm. With three beams, the authors are able to obtain water vapor number densities at three locations. Frequency modulation spectroscopy technique is used to achieve high detection sensitivity. The diode laser is modulated at radio frequency (RF), while the wavelength of the diode laser is tuned to scan over a strong water vapor absorption line. The detected RF signal is then demodulated at the fundamental frequency of the modulation (one-F demodulation). A working model and a computer software code have been developed for data process and data analysis. Water vapor number density measurements are achieved with consideration of temperature dependence. Experimental results and data analysis will be presented.

  10. Diode-laser-based water vapor differential absorption lidar (DIAL) profiler evaluation

    NASA Astrophysics Data System (ADS)

    Spuler, S.; Weckwerth, T.; Repasky, K. S.; Nehrir, A. R.; Carbone, R.

    2012-12-01

    We are in the process of evaluating the performance of an eye-safe, low-cost, diode-laser-based, water vapor differential absorption lidar (DIAL) profiler. This class of instrument may be capable of providing continuous water vapor and aerosol backscatter profiles at high vertical resolution in the atmospheric boundary layer (ABL) for periods of months to years. The technology potentially fills a national long term observing facility gap and could greatly benefit micro- and meso-meteorology, water cycle, carbon cycle and, more generally, biosphere-hydrosphere-atmosphere interaction research at both weather and climate variability time scales. For the evaluation, the Montana State University 3rd generation water vapor DIAL was modified to enable unattended operation for a period of several weeks. The performance of this V3.5 version DIAL was tested at MSU and NCAR in June and July of 2012. Further tests are currently in progress with Howard University at Beltsville, Maryland; and with the National Weather Service and Oklahoma University at Dallas/Fort Worth, Texas. The presentation will include a comparison of DIAL profiles against meteorological "truth" at the aforementioned locations including: radiosondes, Raman lidars, microwave and IR radiometers, AERONET and SUOMINET systems. Instrument reliability, uncertainty, systematic biases, detection height statistics, and environmental complications will be evaluated. Performance will be judged in the context of diverse scientific applications that range from operational weather prediction and seasonal climate variability, to more demanding climate system process studies at the land-canopy-ABL interface. Estimating the extent to which such research and operational applications can be satisfied with a low cost autonomous network of similar instruments is our principal objective.

  11. Growth of vertical-cavity surface emitting lasers by metalorganic vapor phase epitaxy

    SciTech Connect

    Hou, H.Q.; Hammons, B.E.; Crawford, M.H.; Lear, K.L.; Choquette, K.D.

    1996-10-01

    We present growth and characterization of visible and near-infrared vertical-cavity surface emitting lasers (VCSELs) grown by metalorganic vapor phase epitaxy. Discussions on the growth issue of VCSEL materials include growth rate and composition control using an {ital in}{ital situ} normal-incidence reflectometer, comprehensive p- and n-type doping study in AlGaAs by CCl{sub 4} and Si{sub 2}H{sub 6} over the entire composition range, and optimization of ultra-high material uniformity. We also demonstrate our recent achievements of all-AlGaAs VCSELs which include the first room-temperature continuous- wave demonstration of 700-nm red VCSELs and high-efficiency and low- threshold voltage 850-nm VCSELs.

  12. Laser Physical Vapor Deposition of Nanocrystalline Boron Carbide Films to Enhance Cutting Tool Performance

    SciTech Connect

    Jagannadham, K.; Watkins, Thomas R; Lance, Michael J; Riester, Laura; Lemaster, Robert A

    2009-01-01

    Laser physical vapor deposition was used to deposit thin films of boron carbide on Si (100) and WC-Co substrates at 550 C under different pressures of methane atmosphere. Grazing incidence X-ray diffraction was used to identify a boron carbide phase, which exhibited weak peaks. The presence of particulates in the size range of 50 nm-3 {micro}m embedded in an amorphous matrix was observed by scanning electron microscopy. Raman spectroscopy indicated that as methane partial pressure was increased during deposition, the amount of disorder with the boron carbide structure also increased. Also, the nanoindentation hardness decreased, while the coefficient of friction and scratch adhesion strength increased. These effects are attributed to an increase in amorphous phase/disorder in the films. Wear tests conducted by machining particleboard using boron carbide coated WC-Co tools in the absence of methane showed the same wear rate as tools coated under higher methane pressures.

  13. Droplet sizes and velocities in vaporizing sprays. [using laser Doppler anemometry

    NASA Technical Reports Server (NTRS)

    Yule, A. J.; Ereaut, P. R.; Ungut, A.

    1983-01-01

    A pulse height laser Doppler anemometer particle sizing technique has been refined to permit simultaneous particle size and velocity measurements in sprays. The improvements include (1) the use of a specially tailored 'top hat' light distribution, to provide unambiguous particle diameter-signal amplitude relations, (2) the use of back scattered light collection, and (3) the utilization of Mie theory to compute the relations between signal amplitude and particle diameter, in the backscatter mode. Twin-fluid atomized kerosene sprays have been investigated using the new technique. In these sprays distributions have been mapped of mean droplet diameters, droplet size distributions, and the local correlations between droplet diameters and velocities. The data show the variation of spray structure with atomizer input parameters, the preferential vaporization of smaller droplets, and the differing trajectories of the large and small droplets.

  14. Performance of hybrid, diffraction, and continuously coupled cat-eye resonators with kinetically enhanced copper vapor lasers

    NASA Astrophysics Data System (ADS)

    Singh, Bijendra; Subramaniam, V. V.; Daultabad, Shankar; Ghodke, Dharmraj; Chakraborty, Ashim

    2010-09-01

    New resonators, namely the hybrid cat-eye resonator (HCER), diffraction-coupled cat-eye resonator (DCCER), and continuously coupled cat-eye resonator (CCCER) are demonstrated for the first time here in a kinetically enhanced copper vapor laser with high optical extraction of 70 to 80%, low beam divergence ~0.15 mrad (approximately five times the diffraction limit), and high misalignment tolerance ~5 to 6 mrad achieved simultaneously from each of these configurations. The laser used in the experiment is a 45- to 47-mm bore, 50-W kinetically enhanced copper vapor laser. In the case of HCER, the laser beam divergence reduces to about 0.12 mrad (~30-fold reduction) in an unstable direction and about 0.5 mrad (approximately seven-fold reduction) in a stable direction with average beam power of about 35 W, which is ~70% of 50-W maximum set power of the laser. In the DCCER configuration, laser power achieved is about ~37 W (75% of 50-W laser power) with beam divergence of about 0.17 mrad and misalignment tolerance of ~5 mrad. In CCCER, the output power of about 40 W (80% of 50-W laser power) is achieved with beam divergence of about 0.1 mrad (approximately three to four times the diffraction limit).

  15. Copper vapor laser fragmentation of gallstones: in vitro measurements of wall heat transmission.

    PubMed

    Dayton, M T; Decker, D L; McClane, R; Dixon, J A

    1988-07-01

    Laser fragmentation is a promising new modality in management of retained CBD stones. Recent reports demonstrate the feasibility of lasers for this, but few studies have evaluated their safety (e.g., thermal injury may occur at greater than 43 degrees C). This study was conducted to measure heat transmission from lased bilirubinate and mixed stones to a simulated CBD wall. Four welded thermocouples were passed to the inside wall of 6-mm polyvinyl tubing 90 degrees apart to surround the lumen stone. The thermocouples were interfaced to a computer and temperatures were recorded every 270 msec. The tubing was submerged in a 37 degrees C water bath for all lasing work. A copper vapor laser (wavelength, 510 nm; 5.6 W; 5 kHz; pulse length, 30 ns) was attached to a 650-micron quartz fiber. A stone was "impacted" in the tubing and the laser fiber was pushed against the stone while making multiple passes to fragment it. Thirty mixed gallstones (mean size, 6.9 X 5.1 mm) and 20 bilirubinate gallstones (mean size, 7.1 X 5.2 mm) were fragmented during the study. Maximum temperature (Tmax), duration of Tmax (TmaxD), interval to stone piercing (TiP), and interval to fragmentation (TiF) were measured and comparisons were carried out with the SPSS statistical package using the t test procedure. The Tmax generated during fragmentation of bilirubinate stones (43.4 +/- 1.7 degrees C) was significantly less (P less than 0.002) than the Tmax for mixed stones (54.0 +/- 2.7 degrees C) but both Tmax values represented potentially injurious temperature levels.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3392997

  16. Species-resolved laser-probing investigations of the hydrodynamics of KrF excimer and copper vapor laser ablation processing of materials

    NASA Astrophysics Data System (ADS)

    Ventzek, Peter L. G.; Gilgenbach, Ronald M.; Ching, Chi H.; Lindley, R. A.

    1993-06-01

    Hydrodynamic phenomena from KrF excimer laser ablation (10-3-20 J/cm2) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by laser beam deflection, schlieren photography, shadowgraphy, laser-induced-fluorescence and dye-laser- resonance absorption photography (DLRAP). Experiments were performed in vacuum and gaseous environments (10-5 to 760 Torr). In vacuum, the DLRAP diagnostic shows species-resolved plume expansion which is consistent with that of a reflected rarefaction wave. Increasing the background gas pressure reveals the formation of sound/shock compared to CN in the laser-ablated polyimide (Vespel) plume/shock in inert (e.g. argon) and reactive (e.g. air) gases. At low pressures (less than 10 Torr) Al and CN species are in close contact with the shock front. As the pressure increases, the species front tends to recede, until at high pressures (over 200 Torr) the species are restrained to only a few mm above the target surface. After sufficient expansion, Al and CN are no longer detectable; only the shadowgraph of the hot gas plume remains. Since CN is observable in both inert and reactive environments, it can be concluded that CN is not a reaction product between the background gas and the ablated species. By way of comparison to excimer laser ablation processing of materials, copper vapor laser machined polyimide and polymethylmethacrylate (transparent to green and yellow copper vapor laser light) are also investigated. The two polymers are observed to have markedly different machined surfaces. Hydrodynamic effects for the copper vapor laser machined materials are investigated using HeNe laser beam deflection.

  17. Homogeneity of bismuth-distribution in bismuth-doped alkali germanate laser glasses towards superbroad fiber amplifiers.

    PubMed

    Zhao, Yanqi; Wondraczek, Lothar; Mermet, Alain; Peng, Mingying; Zhang, Qinyuan; Qiu, Jianrong

    2015-05-01

    Compared to rare-earth doped glasses, bismuth-doped glasses hold promise for super-broadband near-infrared (NIR) photoemission and potential applications in optical amplification. However, optically active bismuth centers are extremely sensitive to the properties of the surrounding matrix, and also to processing conditions. This is strongly complicating the exploitation of this class of materials, because functional devices require a very delicate adjustment of the redox state of the bismuth species, and its distribution throughout the bulk of the material. It also largely limits some of the conventional processing routes for glass fiber, which start from gas phase deposition and may require very high processing temperature. Here, we investigate the influence of melting time and alkali addition on bismuth-related NIR photoluminescence from melt-derived germanate glasses. We show that the effect of melting time on bismuth-related absorption and NIR photoemission is primarily through bismuth volatilization. Adding alkali oxides as fluxing agents, the melt viscosity can be lowered to reduce either the glass melting temperature, or the melting time, or both. At the same time, however, alkali addition also leads to increasing mean-field basicity, what may reduce the intensity of bismuth-related NIR emission. Preferentially using Li2O over Na2O or K2O presents the best trade-off between those above factors, because its local effect may be adverse to the generally assumed trend of the negative influence of more basic matrix composition. This observation provides an important guideline for the design of melt-derived Bi-doped glasses with efficient NIR photoemission and high optical homogeneity. PMID:25969328

  18. Collimated, single-pass atom source from a pulsed alkali metal dispenser for laser-cooling experiments

    SciTech Connect

    Moore, Kevin L.; Purdy, Thomas P.; Murch, Kater W.; Leslie, Sabrina; Gupta, Subhadeep; Stamper-Kurn, Dan M.

    2005-02-01

    We have developed an improved scheme for loading atoms into a magneto-optical trap (MOT) from a directed rubidium alkali metal dispenser in <10{sup -10} Torr ultrahigh vacuum conditions. A current-driven dispenser was surrounded with a cold absorbing 'shroud' held at {<=}0 deg. C, pumping rubidium atoms not directed into the MOT. This nearly eliminates background atoms and reduces the detrimental rise in pressure normally associated with these devices. The system can be well-described as a current-controlled, rapidly switched, two-temperature thermal beam, and was used to load a MOT with 3x10{sup 8} atoms.

  19. Distribution of sodium and potassium within individual human erythrocytes by pulsed-laser vaporization in a sheath flow

    SciTech Connect

    Cheung, N.H.; Yeung, E.S. )

    1994-04-01

    Simultaneous determination of the amounts of Na and K inside single human erythrocytes was accomplished by laser vaporization and monitoring the atomic emission produced. By using a modified sheath-flow arrangement, detection of 8 fg (0.35 fmol) of Na is possible with one laser pulse. By using Poisson statistics, one can obtain single-cell information even when multiple cells are vaporized per laser pulse. The intracellular contents for a given individual were found to vary significantly. The [+-]55% and [+-]155% variations for Na and K, respectively, cannot be explained by changes in cell volume. There is only a weak correlation between the Na and K contents in single cells. The results reflect the age distribution of erythrocytes in the sample. Presumably, the enzymes regulating ion transport lose their activities in the older cells. 28 refs., 11 figs., 2 tabs.

  20. Alkali metal intercalates of molybdenum disulfide.

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.

    1973-01-01

    Study of some of the physicochemical properties of compounds obtained by subjecting natural molybdenite and single crystals of molybdenum disulfide grown by chemical vapor transport to intercalation with the alkali group of metals (Li, Na, K, Rb, and Cs) by means of the liquid ammonia technique. Reported data and results include: (1) the intercalation of the entire alkali metal group, (2) stoichiometries and X-ray data on all of the compounds, and (3) superconductivity data for all the intercalation compounds.

  1. Effects of carrier gas dynamics on single wall carbon nanotube chiral distributions during laser vaporization synthesis.

    PubMed

    Landi, Brian J; Raffaelle, Ryne P

    2007-03-01

    We report on the utility of modifying the carrier gas dynamics during laser vaporization synthesis to alter the single wall carbon nanotube (SWNT) chiral distribution. SWNTs produced from an Alexandrite laser using conventional Ni/Co catalysts demonstrate marked differences in chiral distributions due to effects of helium gas and reactor chamber pressure, in comparison to conventional subambient pressures and argon gas. Optical absorption and Raman spectroscopies confirm that the SWNT diameter distribution decreases under higher pressure and with helium gas as opposed to argon. Fluorescence mapping of the raw soots in sodium dodecylbenzene sulfonate (SDBS)-D2O was used to estimate the relative (n, m)-SWNT content of the semiconducting types. A predominance of type II structures for each synthesis condition was observed. The distribution of SWNT chiral angles was observed to shift away from near-armchair configurations under higher pressure and with helium gas. These results illustrate the importance of gas type and pressure on the condensation/cooling rate, which allows for synthesis of specific SWNT chiral distributions. PMID:17450850

  2. Spherical silicon-shell photonic band gap structures fabricated by laser-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, H.; Yang, Z. Y.; Lu, Y. F.

    2007-02-01

    Laser-assisted chemical vapor deposition was applied in fabricating three-dimensional (3D) spherical-shell photonic band gap (PBG) structures by depositing silicon shells covering silica particles, which had been self-assembled into 3D colloidal crystals. The colloidal crystals of self-assembled silica particles were formed on silicon substrates using the isothermal heating evaporation approach. A continuous wave Nd:YAG laser (1064nm wavelength) was used to deposit silicon shells by thermally decomposing disilane gas. Periodic silicon-shell/silica-particle PBG structures were obtained. By removing the silica particles enclosed in the silicon shells using hydrofluoric acid, hollow spherical silicon-shell arrays were produced. This technique is capable of fabricating structures with complete photonic band gaps, which is predicted by simulations with the plane wave method. The techniques developed in this study have the potential to flexibly engineer the positions of the PBGs by varying both the silica particle size and the silicon-shell thickness. Ellipsometry was used to investigate the specific photonic band gaps for both structures.

  3. Hydrocarbon-free resonance transition 795-nm rubidium laser

    SciTech Connect

    Wu, S Q; Soules, T F; Page, R H; Mitchell, S C; Kanz, V K; Beach, R J

    2008-01-09

    An optical resonance transition rubidium laser (5{sup 2}P{sub 1/2} {yields} 5{sup 2}S{sub 1/2}) is demonstrated with a hydrocarbon-free buffer gas. Prior demonstrations of alkali resonance transition lasers have used ethane as either the buffer gas or a buffer gas component to promote rapid fine-structure mixing. However, our experience suggests that the alkali vapor reacts with the ethane producing carbon as one of the reaction products. This degrades long term laser reliability. Our recent experimental results with a 'clean' helium-only buffer gas system pumped by a Ti:sapphire laser demonstrate all the advantages of the original alkali laser system, but without the reliability issues associated with the use of ethane.

  4. High rate, large area laser-assisted chemical vapor deposition of nickel from nickel carbonyl

    NASA Astrophysics Data System (ADS)

    Paserin, Vlad

    High-power diode lasers (HPDL) are being increasingly used in industrial applications. Deposition of nickel from nickel carbonyl (Ni(CO)4 ) precursor by laser-induced chemical vapor deposition (CVD) was studied with emphasis on achieving high deposition rates. An HPDL system was used to provide a novel energy source facilitating a simple and compact design of the energy delivery system. Nickel deposits on complex, 3-dimensional polyurethane foam substrates were prepared and characterized. The resulting "nickel foam" represents a novel material of high porosity (>95% by volume) finding uses, among others, in the production of rechargeable battery and fuel cell electrodes and as a specialty high-temperature filtration medium. Deposition rates up to ˜19 mum/min were achieved by optimizing the gas precursor flow pattern and energy delivery to the substrate surface using a 480W diode laser. Factors affecting the transition from purely heterogeneous decomposition to a combined hetero- and homogeneous decomposition of nickel carbonyl were studied. High quality, uniform 3-D deposits produced at a rate more than ten times higher than in commercial processes were obtained by careful balance of mass transport (gas flow) and energy delivery (laser power). Cross-flow of the gases through the porous substrate was found to be essential in facilitating mass transport and for obtaining uniform deposits at high rates. When controlling the process in a transient regime (near the onset of homogenous decomposition), unique morphology features formed as part of the deposits, including textured surface with pyramid-shape crystallites, spherical and non-spherical particles and filaments. Operating the laser in a pulsed mode produced smooth, nano-crystalline deposits with sub-100 nm grains. The effect of H2S, a commonly used additive in nickel carbonyl CVD, was studied using both polyurethane and nickel foam substrates. H2S was shown to improve the substrate coverage and deposit

  5. Computer modeling of the sensitivity of a laser water vapor sensor to variations in temperature and air speed

    NASA Technical Reports Server (NTRS)

    Tucker, George F.

    1994-01-01

    Currently, there is disagreement among existing methods of determining atmospheric water vapor concentration at dew-points below -40 C. A major source of error is wall effects which result from the necessity of bringing samples into the instruments. All of these instruments also have response times on the order of seconds. NASA Langley is developing a water vapor sensor which utilizes the absorption of the infrared radiation produced by a diode laser to estimate water vapor concentration. The laser beam is directed through an aircraft window to a retroreflector located on an engine. The reflected beam is detected by an infrared detector located near the laser. To maximize signal to noise, derivative signals are analyzed. By measuring the 2f/DC signal and correcting for ambient temperature, atmospheric pressure and air speed (which results in a Doppler shifting of the laser beam), the water vapor concentration can be retrieved. Since this is an in situ measurement there are no wall effects and measurements can be made at a rate of more than 20 per second. This allows small spatial variations of water vapor to be studied. In order to study the sensitivity of the instrument to variations in temperature and air speed, a computer program which generated the 2f, 3f, 4f, DC and 2f/DC signals of the instrument as a function of temperature, pressure and air speed was written. This model was used to determine the effect of errors in measurement of the temperature and air speed on the measured water vapor concentration. Future studies will quantify the effect of pressure measurement errors, which are expected to be very small. As a result of these studied, a retrieval algorithm has been formulated, and will be applied to data taken during the PEM-West atmospheric science field mission. Spectroscopic studies of the water vapor line used by the instrument will be used to refine this algorithm. To prepare for these studies, several lasers have been studied to determine their

  6. Zirconia nanoparticles prepared by laser vaporization as fillers for dental adhesives.

    PubMed

    Lohbauer, Ulrich; Wagner, Andrea; Belli, Renan; Stoetzel, Christian; Hilpert, Andrea; Kurland, Heinz-Dieter; Grabow, Janet; Müller, Frank A

    2010-12-01

    Zirconia nanoparticles prepared by laser vaporization were incorporated into the primer or into the adhesive of a commercial adhesive system in order to evaluate its effect on bond strength to dentin. Zirconia nanoparticles (20-50nm) were prepared using a particular laser vaporization technique and incorporated into the primer (P) or into the adhesive (A) of the Adper Scotchbond Multi-Purpose (SBMP) system at 5, 10, 15 and 20wt.% by means of mechanical mixing (stirring) and ultrasonication. Control (unfilled) and experimental groups (filled) were applied, according to the manufacturer's instructions, onto flat mid-coronal human dentin. Composite crowns were built up, stored in distilled water for 24h at 37°C and cut into 0.65±0.05mm² beams following a non-trimming microtensile technique. Specimens were fractured in tension using a universal testing machine (Zwick) and examined by scanning electron microscopy for fractographic analysis. Microtensile bond strength (μTBS) data were analyzed using a two-way ANOVA and modified LSD test at α=0.05. Analysis of the nanofiller distribution and ultramorphological characterization of the interface were performed by transmission electron microscopy (TEM). Zirconia nanoparticle incorporation into the primer or into the adhesive of SBMP significantly increased μTBS to dentin. Filler concentration only affected μTBS significantly in the P group. Statistically significant differences between groups P and A occurred only at 20wt.% filler content, with a significantly higher μTBS in group P. TEM micrographs revealed nanoparticle deposition on top of a hybrid layer when incorporated into the primer, whereas they remained dispersed through the adhesive layer in group A. Zirconia nanoparticles incorporation into SBMP increased bond strength to dentin by reinforcing the interface adhesive layer. Nanofiller incorporation into the primer solution showed a tendency of increasing bond strength with increasing concentration. At high

  7. Process development for the manufacture of an integrated dispenser cathode assembly using laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Johnson, Ryan William

    2005-07-01

    Laser Chemical Vapor Deposition (LCVD) has been shown to have great potential for the manufacture of small, complex, two or three dimensional metal and ceramic parts. One of the most promising applications of the technology is in the fabrication of an integrated dispenser cathode assembly. This application requires the deposition of a boron nitride-molybdenum composite structure. In order to realize this structure, work was done to improve the control and understanding of the LCVD process and to determine experimental conditions conducive to the growth of the required materials. A series of carbon fiber and line deposition studies were used to characterize process-shape relationships and study the kinetics of carbon LCVD. These studies provided a foundation for the fabrication of the first high aspect ratio multi-layered LCVD wall structures. The kinetics studies enabled the formulation of an advanced computational model in the FLUENT CFD package for studying energy transport, mass and momentum transport, and species transport within a forced flow LCVD environment. The model was applied to two different material systems and used to quantify deposition rates and identify rate-limiting regimes. A computational thermal-structural model was also developed using the ANSYS software package to study the thermal stress state within an LCVD deposit during growth. Georgia Tech's LCVD system was modified and used to characterize both boron nitride and molybdenum deposition independently. The focus was on understanding the relations among process parameters and deposit shape. Boron nitride was deposited using a B3 N3H6-N2 mixture and growth was characterized by sporadic nucleation followed by rapid bulk growth. Molybdenum was deposited from the MoCl5-H2 system and showed slow, but stable growth. Each material was used to grow both fibers and lines. The fabrication of a boron nitride-molybdenum composite was also demonstrated. In sum, this work served to both advance the

  8. Analysis of Amphiphilic Lipids and Hydrophobic Proteins Using Nonresonant Femtosecond Laser Vaporization with Electrospray Post-Ionization

    NASA Astrophysics Data System (ADS)

    Brady, John J.; Judge, Elizabeth J.; Levis, Robert J.

    2011-04-01

    Amphiphilic lipids and hydrophobic proteins are vaporized at atmospheric pressure using nonresonant 70 femtosecond (fs) laser pulses followed by electrospray post-ionization prior to being transferred into a time-of-flight mass spectrometer for mass analysis. Measurements of molecules on metal and transparent dielectric surfaces indicate that vaporization occurs through a nonthermal mechanism. The molecules analyzed include the lipids 1-monooleoyl-rac-glycerol, 1,2-dihexanoyl- sn-glycero-3-phosphocholine, 1,2-dimyristoyl- sn-glycero-3-phosphocholine, and the hydrophobic proteins gramicidin A, B, and C. Vaporization of lipids from blood and milk are also presented to demonstrate that lipids in complex systems can be transferred intact into the gas phase for mass analysis.

  9. Nonlinear infrared generation in alkali metal vapors: Steady state susceptibilities and dynamic behavior. Effective relaxation rates and preliminary Raman gain predictions for the Cs system

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.

    1986-01-01

    Effective relaxation rates for atomic cesium pumped by doubled Alexandrite radiation are presented. Laser radiation levels are 8S 1/2 and 9S 1/2; resonance levels 3 = 8P 1/2 and 8P 1/2, respectively. In addition, Raman gain is represented in two graphs which plot chi per atom (10 to the -13 power) at Raman peak versus the infrared wave number per centimeter and the corresponding doubled Alexandrite wave number. One graph covers resonance level 8P, the other 9P; in both cases cesium is pumped with a peak pulse height of 0.5 MW in a 200 micron diameter spot size.

  10. PHYSICAL PHENOMENA ACCOMPANYING THE GENERATION AND AMPLIFICATION OF LASER RADIATION: Ionization-recombination mechanism of growth of the losses due to triplet-triplet absorption in vapor dye lasers

    NASA Astrophysics Data System (ADS)

    Abakumov, G. A.; Simonov, Alexander P.; Yaroslavtsev, V. T.

    1989-05-01

    Internal losses in vapor dye lasers are attributed to preferential formation of triplet-state molecules as a result of the volume recombination of electrons and cations formed by multistage photoionization of active molecules under the action of the pump radiation. Calculations for a longitudinal pumping variant are used to show that this loss mechanism causes a severe deterioration in the lasing energy characteristics of vapor dye lasers compared with liquid dye lasers.

  11. Optical coatings of variable refractive index and high laser-resistance from physical-vapor-deposited perfluorinated amorphous polymer

    DOEpatents

    Chow, R.; Loomis, G.E.; Thomas, I.M.

    1999-03-16

    Variable index optical single-layers, optical multilayer, and laser-resistant coatings were made from a perfluorinated amorphous polymer material by physical vapor deposition. This was accomplished by physically vapor depositing a polymer material, such as bulk Teflon AF2400, for example, to form thin layers that have a very low refractive index (ca. 1.10--1.31) and are highly transparent from the ultra-violet through the near infrared regime, and maintain the low refractive index of the bulk material. The refractive index can be varied by simply varying one process parameter, either the deposition rate or the substrate temperature. The thus forming coatings may be utilized in anti-reflectors and graded anti-reflection coatings, as well as in optical layers for laser-resistant coatings at optical wavelengths of less than about 2000 nm. 2 figs.

  12. Optical coatings of variable refractive index and high laser-resistance from physical-vapor-deposited perfluorinated amorphous polymer

    DOEpatents

    Chow, Robert; Loomis, Gary E.; Thomas, Ian M.

    1999-01-01

    Variable index optical single-layers, optical multilayer, and laser-resistant coatings were made from a perfluorinated amorphous polymer material by physical vapor deposition. This was accomplished by physically vapor depositing a polymer material, such as bulk Teflon AF2400, for example, to form thin layers that have a very low refractive index (.about.1.10-1.31) and are highly transparent from the ultra-violet through the near infrared regime, and maintain the low refractive index of the bulk material. The refractive index can be varied by simply varying one process parameter, either the deposition rate or the substrate temperature. The thus forming coatings may be utilized in anti-reflectors and graded anti-reflection coatings, as well as in optical layers for laser-resistant coatings at optical wavelengths of less than about 2000 nm.

  13. Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing

    NASA Astrophysics Data System (ADS)

    Ringleb, F.; Eylers, K.; Teubner, Th.; Boeck, T.; Symietz, C.; Bonse, J.; Andree, S.; Krüger, J.; Heidmann, B.; Schmid, M.; Lux-Steiner, M.

    2016-03-01

    A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Based on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.

  14. Production of dense vapor targets for laser-plasma interaction studies with intense, ultra-short pulses

    SciTech Connect

    Bolton, P.R.; Eder, D.C.; Guethlein, G.; Stewart, R.E.; Young, P.E.

    1993-03-19

    The technique of laser-induced ablation of thin films from glass slide substrates has been investigated as a candidate vapor target production method for studies of both tunneling-driven x-ray/xuv recombination lasers and relativistic propagation using intense, ultra-short laser pulses. It is shown by simultaneous two-wavelength interferometry that particle densities of order 10{sup 19}/cm{sup 3} are readily achieved and that some intrinsic ionization accompanies the plume formation. Absorption measurements with both 100 picosecond and 125 femtosecond pulses are consistent with observed edge velocities near 10{sup 6} cm/sec. The level of ionization driven by the intense 125 femtosecond laser pulse has been coarsely estimated. Averaged estimates from spectral blue shifting of spectra transmitted through the plume are consistently lower than those obtained from evaluation of saturation intensity thresholds based on the sequential nonresonant optical field ionization (OFI) process.

  15. Instantaneous Measurement of Local Concentration and Vapor Fraction in Liquid-Gas Mixtures by Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kido, Akihiro; Hoshi, Kenji; Kusaka, Hiroto; Ogawa, Hideyuki; Miyamoto, Noboru

    Laser-induced breakdown spectroscopy (LIBS) with atomic emission excited with a focused high-energy ND: YAG laser was applied to quantify the concentration and the vapor fraction of liquid-gas mixtures. With LIBS it is possible to quantify local concentrations accurately even in liquid-gas mixtures as the ratio of the number of fuel-borne hydrogen atoms to nitrogen or oxygen atoms in the ambient gas. The ratio has a strong linear relation with the ratio of the peak emission intensities regardless of phase of the fuel. As the full width at half maximum (FWHM) of the emission peak from the fuel-borne hydrogen increases linearly with the liquid fraction due to the Doppler shift with micro-explosions, the FWHM yields the fuel vapor fraction. Simultaneous, high-resolution measurements of equivalence ratios and vapor fractions in an intermittent fuel spray in a pressurized atmosphere were obtained with this method. The results showed that the tip of the intermittent spray has a richer mixture with a lower vapor fraction.

  16. Laser-drilled micro-hole arrays on polyurethane synthetic leather for improvement of water vapor permeability

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Wang, A. H.; Zheng, R. R.; Tang, H. Q.; Qi, X. Y.; Ye, B.

    2014-06-01

    Three kinds of lasers at 1064, 532 and 355 nm wavelengths respectively were adopted to construct micro-hole arrays on polyurethane (PU) synthetic leather with an aim to improve water vapor permeability (WVP) of PU synthetic leather. The morphology of the laser-drilled micro-holes was observed to optimize laser parameters. The WVP and slit tear resistance of the laser-drilled leather were measured. Results show that the optimized pulse energy for the 1064, 532 and 355 nm lasers are 0.8, 1.1 and 0.26 mJ, respectively. The diameters of the micro-holes drilled with the optimized laser pulse energy were about 20, 15 and 10 μm, respectively. The depths of the micro-holes drilled with the optimized pulse energy were about 21, 60 and 69 μm, respectively. Compared with the untreated samples, the highest WVP growth ratio was 38.4%, 46.8% and 53.5% achieved by the 1064, 532 and 355 nm lasers, respectively. And the highest decreasing ratio of slit tear resistance was 11.1%, 14.8%, and 22.5% treated by the 1064, 532 and 355 nm lasers, respectively. Analysis of the interaction mechanism between laser beams at three kinds of laser wavelengths and the PU synthetic leather revealed that laser micro-drilling at 355 nm wavelength displayed both photochemical ablation and photothermal ablation, while laser micro-drilling at 1064 and 532 nm wavelengths leaded to photothermal ablation only.

  17. Progress in Understanding Alkali-Alkali Spin Relaxation

    NASA Astrophysics Data System (ADS)

    Erickson, Christopher J.; Happer, William; Chann, Bien; Kadlecek, Stephen; Anderson, L. W.; Walker, Thad G.

    2000-06-01

    In extensive experiments we have shown that a spin interaction with a relatively long correlation time causes much of the spin relaxation in very dense alkali-metal vapors. The spin relaxation is affected by the pressure of the helium or nitrogen buffer gas, although there is little dependence at pressures above one atmosphere. There are substantial differences in the relaxation rates for different isotopes of the same element, for example ^87Rb and ^85Rb. We have completed extensive modeling of how singlet and triplet dimers and doublet trimers of the alkali-metal atoms could cause spin relaxation in dense alkali-metal vapors. In the case of doublet trimers or triplet dimers, we assume the main coupling to the nuclear spins is through the Fermi Contact interaction with the unpaired electrons. Spin loss to the rotation of the molecule is assumed to occur through the electronic spin-rotation and spin-axis (dipole-dipole) interactions for the triplet dimers. For the singlet dimers, we assume that the nuclear spins couple directly to the rotational angular momentum of the molecule through the electric quadrupole interaction. We account for all of the total nuclear spin states that occur for the dimers and trimers. We have also considered the possibility that the collisional breakup and formation rates of the dimers or trimers could saturate with increasing buffer gas pressure. Such saturation occurs in many other unimolecular reactions and is often ascribed to breakup through activated states.

  18. MW Spectroscopy Coupled with Ultrafast UV Laser Vaporization: Succinic Acid in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Mendez, Estibaliz; Ecija, Patricia; Cocinero, Emilio J.; Castano, Fernando; Basterretxea, Francisco J.; Godfrey, Peter D.; McNaughton, Don; Jahn, Michaela K.; Nair, K. P. Rajappan; Grabow, Jens-Uwe

    2013-06-01

    Recent lab and field measurements have indicated critical roles of organic acids in enhancing new atmospheric aerosol formation. In order to understand the nucleation process, here we report an experimental and theoretical investigation of chemical structure of succinic acid. We have used the technique of Fourier Transform Microwave Spectroscopy (FTMW). Succinic acid was vaporized by UV ultrafast laser ablation to suppress thermal decomposition processes^a and seeded into an expanding stream of Ne forming a supersonic jet. The rotational spectrum detected the presence of a single most stable conformation in the cm- mm- wave regions for which accurate rotational and centrifugal distortion parameters have been determined. The study was extended to all monosubstituted isotopic species (^{13}C, ^{18}O, D(O)), which were positively identified, leading to an accurate determination of the effective and substitution structures of the molecule. The experimental study was supplemented by ab initio (MP2) and DFT (M06-2X and B3LYP) calculations. ^{a} E. J. Cocinero, A. Lesarri, P. écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño, Angew. Chem. Int. Ed., 51, 3119-3124, 2012.

  19. Vaporization of the Prostate with 150-W Thulium Laser: Complications with 6-Month Follow-Up

    PubMed Central

    García-Larrosa, Alejandro; Capdevila, Santiago; Laborda, Ainhoa

    2014-01-01

    Abstract Purpose: To analyze the efficacy and safety of vaporization of the prostate (VP) with the 150-W thulium:yttrium-aluminum-garnet (Tm:YAG) laser. Patients and Methods: In a prospective series of 55 patients with small- and medium-size prostates undergoing major outpatient surgery (MOS), the primary objectives were to analyze changes in maximum flow (Qmax) and International Prostate Symptom Score (IPSS) after 6 months. Immediate (<30 days) and late (>30 days) complications were subsequently recorded. Results: An increase in mean Qmax of 9.33 mL/s (95% confidence interval [CI] of the mean difference 6.73–11.93; P<0.001) was recorded, and mean IPSS was reduced by 16.88 points (95% CI 14.22–19.54; P<0.001). The immediate complications recorded were acute urinary retention (one patient), urinary tract infection without fever (two patients), and macroscopic hematuria (two patients). The only late complication observed was bladder neck sclerosis (one patient). Conclusion: After 6 months, VP with 150-W Tm:YAG presents promising results in the clinical improvement of patients with small- and medium-size prostates. Its complication rate is low and it offers excellent hemostasis. The data from our study provide the basis for the design of clinical trials to compare this technique with other procedures. PMID:24521152

  20. [Atomic Vapor Laser Isotope Separation (AVLIS) program]. Final report, [January--July 1992

    SciTech Connect

    Not Available

    1992-12-04

    This report summarizes work performed for the Atomic Vapor Laser Isotope Separation (AVLIS) program from January through July, 1992. Each of the tasks assigned during this period is described, and results are presented. Section I details work on sensitivity matrices for the UDS relay telescope. These matrices show which combination of mirror motions may be performed in order to effect certain changes in beam parameters. In Section II, an analysis is given of transmission through a clipping aperture on the launch telescope deformable mirror. Observed large transmission losses could not be simulated in the analysis. An EXCEL spreadsheet program designed for in situ analysis of UDS optical systems is described in Section III. This spreadsheet permits analysis of changes in beam first-order characteristics due to changes in any optical system parameter, simple optimization to predict mirror motions needed to effect a combination of changes in beam parameters, and plotting of a variety of first-order data. Optical systems may be assembled directly from OSSD data. A CODE V nonsequential model of the UDS optical system is described in Section IV. This uses OSSD data to build the UDS model; mirror coordinates may thus be verified. Section V summarizes observations of relay telescope performance. Possible procedures which allow more accurate assessment of relay telescope performance are given.

  1. Treatment of bladder cancer by HPD and gold vapor laser in seventy patients

    NASA Astrophysics Data System (ADS)

    Jiang, Yu; Dai, Shen-guo

    1994-05-01

    Seventy patients with 316 tumors of urinary bladder have been treated by high power gold vapor laser with HPD photodynamic therapy in this hospital. All cases were histopathologically diagnosed as transitional cell carcinoma, T1-T3 stage and all are recurrent ones. HPD was administered intravenously 48 hours before the treatment (5 mg per kg of patient weight) and irrigated into bladder 2 to 4 hours (2.5 mg per kg of patient weight) before the treatment. The power calculated was 70.8 - 509.6 mw/cm per pulse. The pulse energy was 0.5 mJ per pulse and the repetition rate was 6000 - 9000 Hz. Both the tumors and whole bladder were irradiated through the fiber inserted in the bladder by cystoscope. The results of a follow-up from 4 to 46 months are as follows: cured 54 (77.14%); good effect 12 (17.14%); improved 4 (5.7%). Regrowth occurred in only 8 cases (11.43%) between 3 to 14 months.

  2. Field-deployable diode-laser-based differential absorption lidar (DIAL) for profiling water vapor

    NASA Astrophysics Data System (ADS)

    Spuler, S. M.; Repasky, K. S.; Morley, B.; Moen, D.; Hayman, M.; Nehrir, A. R.

    2015-03-01

    A field-deployable water vapor profiling instrument that builds on the foundation of the preceding generations of diode-laser-based differential absorption lidar (DIAL) laboratory prototypes was constructed and tested. Significant advances are discussed, including a unique shared telescope design that allows expansion of the outgoing beam for eye-safe operation with optomechanical and thermal stability; multistage optical filtering enabling measurement during daytime bright-cloud conditions; rapid spectral switching between the online and offline wavelengths enabling measurements during changing atmospheric conditions; and enhanced performance at lower ranges by the introduction of a new filter design and the addition of a wide field-of-view channel. Performance modeling, testing, and intercomparisons are performed and discussed. In general, the instrument has a 150 m range resolution with a 10 min temporal resolution; 1 min temporal resolution in the lowest 2 km of the atmosphere is demonstrated. The instrument is shown capable of autonomous long-term field operation - 50 days with a > 95% uptime - under a broad set of atmospheric conditions and potentially forms the basis for a ground-based network of eye-safe autonomous instruments needed for the atmospheric sciences research and forecasting communities.

  3. Field deployable diode-laser-based differential absorption lidar (DIAL) for profiling water vapor

    NASA Astrophysics Data System (ADS)

    Spuler, S. M.; Repasky, K. S.; Morley, B.; Moen, D.; Hayman, M.; Nehrir, A. R.

    2014-11-01

    A field deployable water vapor profiling instrument that builds on the foundation of the preceding generations of diode-laser-based differential absorption lidar (DIAL) laboratory prototypes has been constructed and tested. Significant advances are discussed, including: a unique shared telescope design that allows expansion of the outgoing beam for eye-safe operation with opto-mechanical and thermal stability, multi-stage optical filtering enabling measurement during daytime bright-cloud conditions, rapid spectral switching between the online and offline wavelengths enabling measurements during changing atmospheric conditions, and enhanced performance at lower ranges by the introduction of a new filter design and the addition of a wide field-of-view channel. Performance modeling, testing and intercomparisons have been performed and are discussed. In general, the instrument has 150 m range resolution with 10 min temporal resolution - 1 min temporal resolution in the lowest 2 km of the atmosphere is demonstrated. The instrument was shown capable of autonomous long term field operation - 50 days with a >95% uptime - under a broad set of atmospheric conditions and potentially forms the basis for a ground-based network of eye-safe autonomous instruments needed for the atmospheric sciences research and forecasting communities.

  4. Fast growth of branched nickel monosilicide nanowires by laser-assisted chemical vapor deposition.

    PubMed

    Gao, Y; Zhou, Y S; Qian, M; Xie, Z Q; Xiong, W; Luo, H F; Jiang, L; Lu, Y F

    2011-06-10

    Branched nickel monosilicide (NiSi) nanowires (NWs), for the first time, have been synthesized on Ni foams by laser-assisted chemical vapor deposition using disilane precursor molecules. Studies indicate that 600 °C is the threshold temperature for the growth of a large number of branched NiSi NWs with 100-500 nm long branches extending from the main stems. Below the threshold temperature, unbranched NiSi NWs were obtained. The density of the branched NiSi NWs is relatively higher in comparison to that of the unbranched ones. The growth rate of the branched NiSi NWs at 700 °C is estimated up to 10 µm min(-1). High-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy of the branched NiSi NWs suggest that the formation of these branched nanostructures is ascribed to the Ni-dominant diffusion process. These NiSi NWs with branched nanostructures could bring them new opportunities in nanodevices. PMID:21474870

  5. Fast growth of branched nickel monosilicide nanowires by laser-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Zhou, Y. S.; Qian, M.; Xie, Z. Q.; Xiong, W.; Luo, H. F.; Jiang, L.; Lu, Y. F.

    2011-06-01

    Branched nickel monosilicide (NiSi) nanowires (NWs), for the first time, have been synthesized on Ni foams by laser-assisted chemical vapor deposition using disilane precursor molecules. Studies indicate that 600 °C is the threshold temperature for the growth of a large number of branched NiSi NWs with 100-500 nm long branches extending from the main stems. Below the threshold temperature, unbranched NiSi NWs were obtained. The density of the branched NiSi NWs is relatively higher in comparison to that of the unbranched ones. The growth rate of the branched NiSi NWs at 700 °C is estimated up to 10 µm min - 1. High-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy of the branched NiSi NWs suggest that the formation of these branched nanostructures is ascribed to the Ni-dominant diffusion process. These NiSi NWs with branched nanostructures could bring them new opportunities in nanodevices.

  6. Atmospheric remote sensing of water vapor, HCl and CH4 using a continuously tunable Co:MgF2 laser

    NASA Technical Reports Server (NTRS)

    Menyuk, Norman; Killinger, Dennis K.

    1987-01-01

    A differential-absorption lidar system has been developed which uses a continuously tunable (1.5-2.3 micron) cobalt-doped magnesium fluoride laser as the radiation source. Preliminary atmospheric measurements of water vapor, HCl, and CH4 have been made with this system, including both path-averaged and ranged-resolved DIAL measurements at ranges up to 6 and 3 km, respectively.

  7. Comparison of Water Vapor Measurements by Airborne Sun Photometer and Diode Laser Hygrometer on the NASA DC-8

    SciTech Connect

    Livingston, J. M.; Schmid, Beat; Russell, P. B.; Podolske, James R.; Redemann, Jens; Diskin, G. S.

    2008-10-29

    In January-February 2003 the 14-channel NASA Ames Airborne Tracking Sunphotometer 30 (AATS) and the NASA Langley/Ames Diode Laser Hygrometer (DLH) were flown on the NASA DC-8 aircraft. AATS measured column water vapor on the aircraft-to-sun path, while DLH measured local water vapor in the free stream between the aircraft fuselage and an outboard engine cowling. The AATS and DLH measurements were compared for two DC-8 vertical profiles by differentiating the AATS column measurement and/or integrating the DLH local measurement over the altitude range of each profile (7.7-10 km and 1.2-12.5 km). These comparisons extend, for the first time, tests of AATS water vapor retrievals to altitudes >~6 km and column contents <0.1 g cm-2. To our knowledge this is the first time suborbital spectroscopic water vapor measurements using the 940-nm band have been tested in conditions so high and dry. For both profiles layer water vapor (LWV) from AATS and DLH were highly correlated, with r2 0.998, rms difference 7.2% and bias (AATS minus DLH) 0.9%. For water vapor densities AATS and DLH had r2 0.968, rms difference 27.6%, and bias (AATS minus DLH) -4.2%. These results compare favorably with previous comparisons of AATS water vapor to in situ results for altitudes <~6 km, columns ~0.1 to 5 g cm-2 and densities ~0.1 to 17 g m-3.

  8. Rock Degradation by Alkali Metals: A Possible Lunar Erosion Mechanism.

    PubMed

    Naughton, J J; Barnes, I L; Hammond, D A

    1965-08-01

    When rocks melt under ultrahigh-vacuum conditions, their alkali components volatilize as metals. These metal vapors act to comminute polycrystalline rocks to their component minerals. The resultant powder is porous and loosely packed and its characteristics may be compatible with the lunar surface as revealed by the Ranger photographs. If meteorite impact or lunar volcanism has produced vaporization or areas of molten lava, alkali erosion may have given dust of this character in adjacent solid areas. PMID:17747570

  9. Biodiversity Mapping via Natura 2000 Conservation Status and Ebv Assessment Using Airborne Laser Scanning in Alkali Grasslands

    NASA Astrophysics Data System (ADS)

    Zlinszky, A.; Deák, B.; Kania, A.; Schroiff, A.; Pfeifer, N.

    2016-06-01

    Biodiversity is an ecological concept, which essentially involves a complex sum of several indicators. One widely accepted such set of indicators is prescribed for habitat conservation status assessment within Natura 2000, a continental-scale conservation programme of the European Union. Essential Biodiversity Variables are a set of indicators designed to be relevant for biodiversity and suitable for global-scale operational monitoring. Here we revisit a study of Natura 2000 conservation status mapping via airbone LIDAR that develops individual remote sensing-derived proxies for every parameter required by the Natura 2000 manual, from the perspective of developing regional-scale Essential Biodiversity Variables. Based on leaf-on and leaf-off point clouds (10 pt/m2) collected in an alkali grassland area, a set of data products were calculated at 0.5 ×0.5 m resolution. These represent various aspects of radiometric and geometric texture. A Random Forest machine learning classifier was developed to create fuzzy vegetation maps of classes of interest based on these data products. In the next step, either classification results or LIDAR data products were selected as proxies for individual Natura 2000 conservation status variables, and fine-tuned based on field references. These proxies showed adequate performance and were summarized to deliver Natura 2000 conservation status with 80% overall accuracy compared to field references. This study draws attention to the potential of LIDAR for regional-scale Essential Biodiversity variables, and also holds implications for global-scale mapping. These are (i) the use of sensor data products together with habitat-level classification, (ii) the utility of seasonal data, including for non-seasonal variables such as grassland canopy structure, and (iii) the potential of fuzzy mapping-derived class probabilities as proxies for species presence and absence.

  10. Soft-Bake Purification of SWCNTs Produced by Pulsed Laser Vaporization

    NASA Technical Reports Server (NTRS)

    Yowell, Leonard; Nikolaev, Pavel; Gorelik, Olga; Allada, Rama Kumar; Sosa, Edward; Arepalli, Sivaram

    2013-01-01

    The "soft-bake" method is a simple and reliable initial purification step first proposed by researchers at Rice University for single-walled carbon nanotubes (SWCNT) produced by high-pressure carbon mon oxide disproportionation (HiPco). Soft-baking consists of annealing as-produced (raw) SWCNT, at low temperatures in humid air, in order to degrade the heavy graphitic shells that surround metal particle impurities. Once these shells are cracked open by the expansion and slow oxidation of the metal particles, the metal impurities can be digested through treatment with hydrochloric acid. The soft-baking of SWCNT produced by pulsed-laser vaporization (PLV) is not straightforward, because the larger average SWCNT diameters (.1.4 nm) and heavier graphitic shells surrounding metal particles call for increased temperatures during soft-bake. A part of the technology development focused on optimizing the temperature so that effective cracking of the graphitic shells is balanced with maintaining a reasonable yield, which was a critical aspect of this study. Once the ideal temperature was determined, a number of samples of raw SWCNT were purified using the soft-bake method. An important benefit to this process is the reduced time and effort required for soft-bake versus the standard purification route for SWCNT. The total time spent purifying samples by soft-bake is one week per batch, which equates to a factor of three reduction in the time required for purification as compared to the standard acid purification method. Reduction of the number of steps also appears to be an important factor in improving reproducibility of yield and purity of SWCNT, as small deviations are likely to get amplified over the course of a complicated multi-step purification process.

  11. Study of Doped ZnO Films Synthesized by Combining Vapor Gases and Pulsed Laser Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, Sandor L.; George, M. A.

    2000-01-01

    The properties and structure of the ZnO material are similar to those of the GaN. Since an excitonic binding energy of ZnO is about 60 meV, it has strong potential for excitonic lasing at the room temperature. This makes synthesizing ZnO films for applications attractive. However, there are several hurdles in fabricating electro-optical devices from ZnO. One of those is in growing doped p-type ZnO films. Although techniques have been developed for the doping of both p-type and n-type ZnO, this remains an area that can be improved. In this presentation, we will report the experimental results of using both thermal vapor and pulsed laser deposition to grow doped ZnO films. The films are deposited on (0001) sapphire, (001) Si and quartz substrates by ablating a ZnO target. The group III and V elements are introduced into the growth chamber using inner gases. Films are characterized by x-ray diffraction, scanning probe microscopy, energy dispersive spectroscopy, Auger electron spectroscopy, and electrical measurements. The full width at half maximum of theta rocking curves for epitaxial films is less than 0.5 deg. In textured films, it rises to several degrees. Film surface morphology reveals an island growth pattern, but the size and density of these islands vary with the composition of the reactive gases. The electrical resistivity also changes with the doped elements. The relationship between the doping elements, gas composition, and film properties will be discussed.

  12. Flux correction for closed-path laser spectrometers without internal water vapor measurements

    NASA Astrophysics Data System (ADS)

    Hiller, R. V.; Zellweger, C.; Knohl, A.; Eugster, W.

    2012-01-01

    Recently, instruments became available on the market that provide the possibility to perform eddy covariance flux measurements of CH4 and many other trace gases, including the traditional CO2 and H2O. Most of these instruments employ laser spectroscopy, where a cross-sensitivity to H2O is frequently observed leading to an increased dilution effect. Additionally, sorption processes at the intake tube walls modify and delay the observed H2O signal in closed-path systems more strongly than the signal of the sampled trace gas. Thereby, a phase shift between the trace gas and H2O fluctuations is introduced that dampens the H2O flux observed in the sampling cell. For instruments that do not provide direct H2O measurement in the sampling cell, transfer functions from externally measured H2O fluxes are needed to estimate the effect of H2O on trace gas flux measurements. The effects of cross-sensitivity and the damping are shown for an eddy covariance setup with the Fast Greenhouse Gas Analyzer (FGGA, Los Gatos Research Inc.) that measures CO2, CH4, and H2O fluxes. This instrument is technically identical with the Fast Methane Analyzer (FMA, Los Gatos Research Inc.) that does not measure H2O concentrations. Hence, we used measurements from a FGGA to derive a modified correction for the FMA accounting for dilution as well as phase shift effects in our instrumental setup. With our specific setup for eddy covariance flux measurements, the cross-sensitivity counteracts the damping effects, which compensate each other. Hence, the new correction only deviates very slightly from the traditional Webb, Pearman, and Leuning density correction, which is calculated from separate measurements of the atmospheric water vapor flux.

  13. 650-nm AlGaInP multiple-quantum-well lasers grown by metalorganic chemical vapor deposition using tertiarybutylphosphine

    NASA Astrophysics Data System (ADS)

    Dong, Jian-Rong; Teng, Jing-Hua; Chua, Soo-Jin; Foo, Boon-Chin; Wang, Yan-Jun; Yuan, Hai-Rong; Yuan, Shu

    2003-07-01

    Using tertiarybutylphosphine (TBP) as phosphorus precursor, high-quality AlGaInP epilayers and AlGaInP/GaInP multiple-quantum-well (MQW) structures have been grown by metalorganic chemical vapor deposition. The photoluminescence results indicate that the AlGaInP materials are as good as those grown using PH3 in terms of optical quality. Finally, AlGaInP MQW red laser structures have been grown, and the electrically pumped AlGaInP red lasers grown by TBP have been demonstrated with the emission wavelength of 647 nm, indicating that TBP can be used to grow high-quality AlGaInP epilayers and AlGaInP-based red lasers, which presently is dominated by the highly toxic gas source PH3.

  14. Alkali metal nitrate purification

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1986-02-04

    A process is disclosed for removing contaminants from impure alkali metal nitrates containing them. The process comprises heating the impure alkali metal nitrates in solution form or molten form at a temperature and for a time sufficient to effect precipitation of solid impurities and separating the solid impurities from the resulting purified alkali metal nitrates. The resulting purified alkali metal nitrates in solution form may be heated to evaporate water therefrom to produce purified molten alkali metal nitrates suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of purified alkali metal nitrates.

  15. Tissue ablation after 120W greenlight laser vaporization and bipolar plasma vaporization of the prostate: a comparison using transrectal three-dimensional ultrasound volumetry

    NASA Astrophysics Data System (ADS)

    Kranzbühler, Benedikt; Gross, Oliver; Fankhauser, Christian D.; Hefermehl, Lukas J.; Poyet, Cédric; Largo, Remo; Müntener, Michael; Seifert, Hans-Helge; Zimmermann, Matthias; Sulser, Tullio; Müller, Alexander; Hermanns, Thomas

    2012-02-01

    Introduction and objectives: Greenlight laser vaporization (LV) of the prostate is characterized by simultaneous vaporization and coagulation of prostatic tissue resulting in tissue ablation together with excellent hemostasis during the procedure. It has been reported that bipolar plasma vaporization (BPV) of the prostate might be an alternative for LV. So far, it has not been shown that BPV is as effective as LV in terms of tissue ablation or hemostasis. We performed transrectal three-dimensional ultrasound investigations to compare the efficiency of tissue ablation between LV and BPV. Methods: Between 11.2009 and 5.2011, 50 patients underwent pure BPV in our institution. These patients were matched with regard to the pre-operative prostate volume to 50 LV patients from our existing 3D-volumetry-database. Transrectal 3D ultrasound and planimetric volumetry of the prostate were performed pre-operatively, after catheter removal, 6 weeks and 6 months. Results: Median pre-operative prostate volume was not significantly different between the two groups (45.3ml vs. 45.4ml; p=1.0). After catheter removal, median absolute volume reduction (BPV 12.4ml, LV 6.55ml) as well as relative volume reduction (27.8% vs. 16.4%) were significantly higher in the BPV group (p<0.001). After six weeks (42.9% vs. 33.3%) and six months (47.2% vs. 39.7%), relative volume reduction remained significantly higher in the BPV group (p<0.001). Absolute volume reduction was non-significantly higher in the BPV group after six weeks (18.4ml, 13.8ml; p=0.051) and six months (20.8ml, 18ml; p=0.3). Clinical outcome parameters improved significantly in both groups without relevant differences between the groups. Conclusions: Both vaporization techniques result in efficient tissue ablation with initial prostatic swelling. BPV seems to be superior due to a higher relative volume reduction. This difference had no clinical impact after a follow-up of 6M.

  16. Investigation on 447.3 nm blue-violet laser by extra-cavity frequency doubling of a diode-pumped cesium vapor laser

    NASA Astrophysics Data System (ADS)

    Xu, Dongdong; Chen, Fei; Guo, Jin; Shao, Mingzhen; Xie, Jijiang

    2016-09-01

    447.3 nm blue-violet lasers are investigated by extra-cavity single-pass second harmonic generation (SHG) of diode-pumped cesium vapor lasers (Cs-DPALs) using a LBO crystal. Two types of 894.6 nm Cs-DPAL are constructed, and the beam quality factors are Mx2=1.02, My2=1.13 and Mx2=2.13, Mx2=2.66, respectively. The maximum output powers for the two types of Cs-DPAL operating in pulsed mode are 0.692 W and 2.6 W, and the corresponding maximum second harmonics (SH) powers are 9.5 μW and 11.2 μW at optimal focusing parameter of 1.68, respectively. The relative insensitivity of SH power to the LBO crystal temperature and the influence of Cs laser beam quality on the SHG efficiency are analyzed qualitatively.

  17. Theoretical studies of Resonance Enhanced Stimulated Raman Scattering (RESRS) of frequency-doubled Alexandrite laser wavelength in cesium vapor. Progress report, January-June 1987

    SciTech Connect

    Lawandy, N.M.

    1987-01-01

    The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for three different sets of relaxation rates. These rates correspond to: (1) Far Infrared (FIR) Raman lasers in the diabatic collision regime without consideration of coupled population decay in a closed system, (2) Raman FIR lasers in the diabatic collision regime with coupled population conserving decay, and (3) IR Raman gain in cesium vapor. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled Alexandrite laser-pumped cesium vapor gain cell.

  18. Milk-alkali syndrome

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000332.htm Milk-alkali syndrome To use the sharing features on this page, please enable JavaScript. Milk-alkali syndrome is a condition in which there ...

  19. Stimulated Raman scattering in lead vapor heat pipe for tunable and narrow-linewidth XeCl excimer laser

    SciTech Connect

    Rieger, H.

    1989-05-01

    Narrow-linewidth and high-efficiency conversion of stimulated Raman scattering (SRS) in a lead vapor heat pipe was observed using a narrow-linewidth and injection-locked XeCl excimer laser system as the pump source. The XeCl laser was continuously tuned over its entire B-X gain curve, from the (0-0) transition to the (0-3) transition, giving it a range of 0.8 nm (307.65-308.45 nm). The laser linewidth was narrowed down to 0.002 A (0.02 cm/sup -1/). The output energy was 310 mJ/pulse, with a repetition rate up to 50 pps and good beam quality. A lead vapor heat pipe operating at 1225/sup 0/C was used as a single-pass stimulated Raman converter, shifting the radiation from 308 to 459 nm. Photon conversion efficiency as high as 80 percent was achieved, using a pump linewidth of 0.01 A.

  20. Ex vivo evaluation of safety and efficacy of vaporization of the prostate using a 300 W high-power laser diode with the wavelength of 980 nm

    NASA Astrophysics Data System (ADS)

    Takada, Junya; Honda, Norihiro; Hazama, Hisanao; Awazu, Kunio

    2014-03-01

    Laser vaporization of the prostate is one of the promising technique for less-invasive treatment of benign prostatic hyperplasia. However, shorter operative duration and higher hemostatic ability are expected. The wavelength of 980 nm offers a high simultaneous absorption by water and hemoglobin, so that it combines the efficient vaporization with good hemostasis. Therefore, we have evaluated the safety and efficacy of vaporization of the prostate using a recently developed 300 W high-power laser diode with the wavelength of 980 nm. First, validity of bovine prostate tissue as the sample was confirmed by measuring the optical properties of bovine and human prostate tissue using a double integrating sphere optical system. Next, contact and non-contact ex vivo irradiations were performed for various irradiation powers and times, and vaporized and coagulated depths were measured. In the contact irradiation, the vaporized depth at the power of 300 W was significantly deeper than that at the power of 100 W, while the difference was relatively smaller for the coagulated depths at 300 and 100 W. In the non-contact irradiation, coagulation as thick as that in the contact irradiation was observed almost without vaporization. Therefore, it is suggested that the treatment in the contact irradiation using the high-power laser diode can vaporize the prostate more efficiently without increasing the risk of perforation. Hemostasis with the coagulation would be possible in both irradiation methods. To prevent the postoperative perforation, operators need to understand the relationship between the coagulated depth and the irradiation conditions.

  1. Spatial dynamics of laser-induced fluorescence in an intense laser beam: An experimental and theoretical study with alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Auzinsh, M.; Berzins, A.; Ferber, R.; Gahbauer, F.; Kalnins, U.

    2016-03-01

    We show that it is possible to model accurately optical phenomena in intense laser fields by taking into account the intensity distribution over the laser beam. We present an extension of an earlier theoretical model that divides an intense laser beam into concentric regions, each with a Rabi frequency that corresponds to the intensity in that region, and solve a set of coupled optical Bloch equations for the density matrix in each region. Experimentally obtained magneto-optical resonance curves for the Fg=2 ⟶Fe=1 transition of the D1 line of 87Rb agree very well with the theoretical model up to a laser intensity of around 200 mW/cm2 for a transition whose saturation intensity is around 4.5 mW/cm2. We examine the spatial dependence of the fluorescence intensity in an intense laser beam experimentally and theoretically. We present and discuss the results of an experiment in which a broad, intense pump laser excites the Fg=4 ⟶Fe=4 transition of the D2 line of cesium while a narrow probe beam scans the atoms within the pump beam and excites the D1 line of cesium, whose fluorescence is recorded as a function of probe beam position. Experimentally obtained spatial profiles of the fluorescence intensity agree qualitatively with the predictions of the model.

  2. Mw Spectroscopy Coupled with Ultrafast UV Laser Vaporization: {RIBOSE} Found in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Cocinero, Emilio J.; Ecija, Patricia; Basterretxea, Francisco J.; Fernandez, Jose A.; Castano, Fernando; Lesarri, Alberto; Grabow, Jens-Uwe

    2012-06-01

    Sugars are aldoses or ketoses with multiple hydroxy groups which have been elusive to spectroscopic studies. Here we report a rotational study of the aldopentose ribose. According to any standard textbook aldopentoses can exhibit either linear forms, cyclic five-membered (furanose) structures or six-membered (pyranose) rings, occurring either as α- or β- anomers depending on the orientation of the hydroxy group at C-1 (anomeric carbon). β-Furanose is predominant in ribonucleosides, RNA, ATP and other biochemically relevant derivatives, but is β-furanose the native form also of free ribose? Recent condensed-phase X-ray and older NMR studies delivered conflicting results. In order to solve this question we conducted a microwave study on D-ribose that, owing to ultrafast UV laser vaporization, has become the first C-5 sugar observed with rotational resolution. The spectrum revealed six conformations of free ribose, preferentially adopting β-pyranose chairs as well as higher-energy α-pyranose forms. The method also allowed for unambiguous distinction between different orientations of the hydroxy groups, which stabilize the structures by cooperative hydrogen-bond networks. No evidence was observed of the α-/β-furanoses or linear forms found in the biochemical derivatives. i) D. Šišak, L. B. McCusker, G. Zandomeneghi, B. H. Meier, D. Bläser, R. Boese, W. B. Schweizer, R. Gylmour and J. D. Dunitz Angew. Chem. Int. Ed. 49, 4503, 2010. ii) W. Saenger Angew. Chem. Int. Ed. 49, 6487, 2010. i) M. Rudrum, and D. F. Shaw, J. Chem. Soc. 52, 1965. ii) R. U. Lemieux and J. D. Stevens Can. J. Chem. 44, 249, 1966. iii) E. Breitmaier and U. Hollstein Org. Magn. Reson. 8, 573, 1976. E. J. Cocinero, A. Lesarri, P. Écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño Angew. Chem. Int. Ed. in press: DOI: 10.1002/anie.201107973, 2012.

  3. Subscale Ship Airwake Studies Using Novel Vortex Flow Devices with Smoke, Laser-Vapor-Screen and Particle Image Velocimetry

    NASA Technical Reports Server (NTRS)

    Lamar, John E.; Landman, Drew; Swift, Russell S.; Parikh, Paresh C.

    2007-01-01

    Ships produce vortices and air-wakes while either underway or stationary in a wind. These flow fields can be detrimental to the conduction of air operations in that they can adversely impact the air vehicles and flight crews. There are potential solutions to these problems for both frigates/destroyers and carriers through the use of novel vortex flow or flow control devices. This appendix highlights several devices which may have application and points out that traditional wind-tunnel testing using smoke, laser-vapor screen, and Particle Image Velocimetry can be useful in sorting out the effectiveness of different devices.

  4. Temporal compression of cw diode-laser output into short pulses with cesium-vapor group-velocity dispersion.

    PubMed

    Choi, K; Menders, J; Ross, D; Korevaar, E

    1993-11-15

    Using a technique similar to chirped pulse compression, we have compressed the 50-mW cw output of a diode laser into pulses of greater than 500-mW peak power and less than 400-ps duration. By applying a small current modulation to the diode, we induced a small wavelength modulation in the vicinity of the 6s(1/2)-to-6p(3/2) cesium resonance transition at 852 nm. Group-velocity dispersion on propagation through a cesium vapor cell then led to pulse compression. We developed a simple model to make predictions of output pulse shapes by using different modulation waveforms. PMID:19829441

  5. Identification of vapor-phase chemical warfare agent simulants and rocket fuels using laser-induced breakdown spectroscopy

    SciTech Connect

    Stearns, Jaime A.; McElman, Sarah E.; Dodd, James A.

    2010-05-01

    Application of laser-induced breakdown spectroscopy (LIBS) to the identification of security threats is a growing area of research. This work presents LIBS spectra of vapor-phase chemical warfare agent simulants and typical rocket fuels. A large dataset of spectra was acquired using a variety of gas mixtures and background pressures and processed using partial least squares analysis. The five compounds studied were identified with a 99% success rate by the best method. The temporal behavior of the emission lines as a function of chamber pressure and gas mixture was also investigated, revealing some interesting trends that merit further study.

  6. Stimulated Raman scattering in lead vapor pumped by a long-pulse 1-J XeCl excimer laser

    SciTech Connect

    Lou, Q.; Huo, Y.

    1988-08-15

    The parametric dependence of the output energies and efficiencies for the Raman conversion of the radiation from a long-pulse 1-J XeCl excimer laser in Pb vapor was investigated. The effects of atom depletion and buffer gas on the stimulated Raman scattering output were discussed in detail. Multipeak structures of the waves of the Raman-shifted pulses were observed which could be attributed to the coherent effects in Raman scattering. A computer model was introduced to explain the multipeak structures of the stimulated Raman scattering waveforms.

  7. Laser-Atomic Oscillator

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu; Happer, William

    2008-05-01

    We report a newly developed technique, laser-atomic oscillator, for simultaneously generating stable optical and electrical modulations with a very few components. It requires only a semiconductor laser, a vapor cell, and a few optical components. No photodetector and electronic feedback are needed. In this new system, the ground-state hyperfine coherence of alkali-metal atoms is spontaneously generated. The modulated laser light with a spectrum of a small optical comb is automatically produced, and the spacing between the comb peaks is photonically locked to the hyperfine frequency. The charge carriers in the semiconductor laser are also modulated at the hyperfine frequency. Laser-atomic oscillator is purely optical. Its simple structure allows the system to be very compact. We believe this new technique will bring some advantages in the applications of atomic chronometry, atomic magnetometry, and generation of multi-coherent light.

  8. Highly Forbidden Transitions in Alkalis: Preparations for a Parity Violation Experiment

    NASA Astrophysics Data System (ADS)

    Oliveira, Claudia

    Preparatory steps for the experimental investigation of the highly forbidden 5s → 6s transition in rubidium using an atom trap and laser cooling are reported. A magneto-optical trap (MOT) has been assembled including saturation spectroscopy and a dichroic vapor laser lock. A frequency-doubled diode laser system has been installed to perform the spectroscopy of the forbidden transition with cold Rb atoms in the trap. The properties of the ns → n's transition in the presence of an external electric field have been investigated theoretically. A first measurement will be exploring the Stark-induced transition amplitude and the very faint magnetic dipole amplitude. The rubidium experiment is a precursor study for a long-term project at TRIUMF, Canada's National Laboratory for nuclear and particle physics, to measure atomic parity violation in the equivalent 7s → 8s transition in francium, the heaviest alkali atom which has no stable isotopes.

  9. Simultaneous visualization of water and hydrogen peroxide vapor using two-photon laser-induced fluorescence and photofragmentation laser-induced fluorescence.

    PubMed

    Larsson, Kajsa; Johansson, Olof; Aldén, Marcus; Bood, Joakim

    2014-01-01

    A concept based on a combination of photofragmentation laser-induced fluorescence (PF-LIF) and two-photon laser-induced fluorescence (LIF) is for the first time demonstrated for simultaneous detection of hydrogen peroxide (H2O2) and water (H2O) vapor. Water detection is based on two-photon excitation by an injection-locked krypton fluoride (KrF) excimer laser (248.28 nm), which induces broadband fluorescence (400-500 nm) from water. The same laser simultaneously photodissociates H2O2, whereupon the generated OH fragments are probed by LIF after a time delay of typically 50 ns, by a frequency-doubled dye laser (281.91 nm). Experiments in six different H2O2/H2O mixtures of known compositions show that both signals are linearly dependent on respective species concentration. For the H2O2 detection there is a minor interfering signal contribution from OH fragments created by two-photon photodissociation of H2O. Since the PF-LIF signal yield from H2O2 is found to be at least ∼24,000 times higher than the PF-LIF signal yield from H2O at room temperature, this interference is negligible for most H2O/H2O2 mixtures of practical interest. Simultaneous single-shot imaging of both species was demonstrated in a slightly turbulent flow. For single-shot imaging the minimum detectable H2O2 and H2O concentration is 10 ppm and 0.5%, respectively. The proposed measurement concept could be a valuable asset in several areas, for example, in atmospheric and combustion science and research on vapor-phase H2O2 sterilization in the pharmaceutical and aseptic food-packaging industries. PMID:25358016

  10. A real time Monte Carlo simulation of thin film nucleation in localized-laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kotecki, David E.; Herman, Irving P.

    1988-11-01

    A real time Monte Carlo simulation is used to model the nucleation and initial stages of thin film growth during localized-laser chemical vapor deposition (LLCVD). This model includes the effects of laser-substrate heating, heterogeneous pyrolytic decomposition of parent molecules on the laser-heated region of the surface, and adatom migration and desorption dynamics. The amount of material deposited as a function of time is obtained over a surface area of 150×150 Å for various values of the substrate temperature, parent gas pressure, and adsorbate-substrate binding energy. Additional information is obtained about the cluster density, and the role of surface defects and two-atom cluster dynamics on the initial growth rate. The deposition of silicon by heterogeneous pyrolytic decomposition of silane (SiH4) is used as a base case for the simulation. Predictions of the initial thin film morphology and its temporal evolution during static laser heating of micron-dimensional regions of the surface are presented. Simulation results indicate that for a given silane pressure and adsorbate-substrate binding energy, there is a critical temperature Tc such that for laser-induced peak temperatures Tplaser-heated region, while for Tp>Tc, nucleation occurs initially in an annulus region centered with respect to the incident laser irradiation. The inclusion of two-atom cluster dynamics in the simulation is shown to increase the value of Tc and alter the initial morphology for low adsorbate-substrate binding energies. The simulation results are extended to scanning LLCVD to predict the maximum scan speed at which nucleation will occur.

  11. 1. 55-. mu. m InGaAsP distributed feedback vapor phase transported buried heterostructure lasers

    SciTech Connect

    Koch, T.L.; Bridges, T.J.; Burkhardt, E.G.; Corvini, P.J.; Coldren, L.A.; Linke, R.A.; Tsang, W.T.; Logan, R.A.; Johnson, L.F.; Kazarinov, R.F.; Yen, R.; Wilt, D.P.

    1985-07-01

    1.55-..mu..m single longitudinal mode InGaAsP distributed feedback (DFB) lasers have been fabricated using a vapor phase transported (VPT) buried heterostructure geometry on a liquid phase epitaxially grown broad area DFB base. Lasing thresholds in the 35--65-mA range were obtained, with side mode suppression ratios as high as 39 dB under modulation. The VPT DFB laser has both a good high-speed modulation capability and low wavelength chirping under high-speed modulation, making it an attractive candidate for high bit rate, long-haul optical fiber systems applications, with demonstrated record system performance at both 2 and 4 Gbit/s.

  12. Water-vapor absorption line measurements in the 940-nm band by using a Raman-shifted dye laser

    NASA Technical Reports Server (NTRS)

    Chu, Zhiping; Wilkerson, Thomas D.; Singh, Upendra N.

    1993-01-01

    We report water-vapor absorption line measurements that are made by using the first Stokes radiation (930-982 nm) with HWHM 0.015/cm generated by a narrow-linewidth, tunable dye laser. Forty-five absorption line strengths are measured with an uncertainty of 6 percent and among them are fourteen strong lines that are compared with previous measurements for the assessment of spectral purity of the light source. Thirty air-broadened linewidths are measured with 8 percent uncertainty at ambient atmospheric pressure with an average of 0.101/cm. The lines are selected for the purpose of temperature-sensitive or temperature-insensitive lidar measurements. Results for these line strengths and linewidths are corrected for broadband radiation and finite laser linewidth broadening effects and compared with the high-resolution transmission molecular absorption.

  13. Combination of thermocoagulation and vaporization using an Nd:YAG/KTP laser versus TURP in BPH treatment: results of a multicenter prospective study

    NASA Astrophysics Data System (ADS)

    Jichlinski, Patrice; Oswald, Michael; Schmidlin, Franz R.; Graber, Peter; Leisinger, Hans-Juerg

    1998-07-01

    Laser treatment of BPH as minimally invasive therapy has found wide employment in the last few years. The objective here was to study the effects of combined technique of coagulation and vaporization with an Nd:YAG/KTP laser on BPH compared to TURP. Thirty-eight patients presenting symptomatic BPH were randomized and treated either by a laser coagulation/vaporization using an ADD fiber at settings of 40 - 60 W for the Nd:YAG and of 36 W for the KTP alike in 21 cases or by TURP in 17 cases. Symptom score, uroflow and residual urine were assessed preoperatively at 1, 3, 6 and 12 months. No transfusion in any group. Similar postoperative catheterization time. Treatment failure in 2 TURP patients and in 2 laser patients. Comparing AUA score, Qmax and residual urine, both forms of treatment were similar at 1 year. Nd:YAG/KTP laser is equivalent to TURP at 1 year for around 40 g prostates.

  14. Effect of temperature and CO 2 concentration on laser-induced breakdown spectroscopy measurements of alkali fume

    NASA Astrophysics Data System (ADS)

    Molina, Alejandro; Shaddix, Christopher R.; Sickafoose, Shane M.; Walsh, Peter M.; Blevins, Linda G.

    2005-08-01

    Laser-induced breakdown spectroscopy (LIBS) was used in the evaluation of aerosol concentration in the exhaust of an oxygen/natural-gas glass furnace. Experiments showed that for a delay time of 10 μs and a gate width of 50 μs, the presence of CO 2 and changes in gas temperature affect the intensity of both continuum emission and the Na D lines. The intensity increased for the neutral Ca and Mg lines in the presence of 21% CO 2 when compared to 100% N 2, whereas the intensity of the Mg and Ca ionic lines decreased. An increase in temperature from 300 to 730 K produced an increase in both continuum emission and Na signal. These laboratory measurements were consistent with measurements in the glass furnace exhaust. Time-resolved analysis of the spark radiation suggested that differences in continuum radiation resulting from changes in bath composition are only apparent at long delay times. The changes in the intensity of ionic and neutral lines in the presence of CO 2 are believed to result from higher free electron number density caused by lower ionization energies of species formed during the spark decay process in the presence of CO 2. For the high Na concentration observed in the glass furnace exhaust, self-absorption of the spark radiation occurred. Power law regression was used to fit laboratory Na LIBS calibration data for sodium loadings, gas temperatures, and a CO 2 content representative of the furnace exhaust. Improvement of the LIBS measurement in this environment may be possible by evaluation of Na lines with weaker emission and through the use of shorter gate delay times.

  15. Direct analysis of intact biological macromolecules by low-energy, fiber-based femtosecond laser vaporization at 1042 nm wavelength with nanospray postionization mass spectrometry.

    PubMed

    Shi, Fengjian; Flanigan, Paul M; Archer, Jieutonne J; Levis, Robert J

    2015-03-17

    A fiber-based laser with a pulse duration of 435 fs and a wavelength of 1042 nm was used to vaporize biological macromolecules intact from the condensed phase into the gas phase for nanospray postionization and mass analysis. Laser vaporization of dried standard protein samples from a glass substrate by 10 Hz bursts of 20 pulses having 10 μs pulse separation and <50 μJ pulse energy resulted in signal comparable to a metal substrate. The protein signal observed from an aqueous droplet on a glass substrate was negligible compared to either a droplet on metal or a thin film on glass. The mass spectra generated from dried and aqueous protein samples by the low-energy, fiber laser were similar to the results from high-energy (500 μJ), 45-fs, 800-nm Ti:sapphire-based femtosecond laser electrospray mass spectrometry (LEMS) experiments, suggesting that the fiber-based femtosecond laser desorption mechanism involves a nonresonant, multiphoton process, rather than thermal- or photoacoustic-induced desorption. Direct analysis of whole blood performed without any pretreatment resulted in features corresponding to hemoglobin subunit-heme complex ions. The observation of intact molecular ions with low charge states from protein, and the tentatively assigned hemoglobin α subunit-heme complex from blood suggests that fiber-based femtosecond laser vaporization is a "soft" desorption source at a laser intensity of 2.39 × 10(12) W/cm(2). The low-energy, turnkey fiber laser demonstrates the potential of a more robust and affordable laser for femtosecond laser vaporization to deliver biological macromolecules into the gas phase for mass analysis. PMID:25688836

  16. MoXy fiber with active cooling cap for bovine prostate vaporization with high power 200W 532 nm laser

    NASA Astrophysics Data System (ADS)

    Peng, Steven Y.; Kang, Hyun Wook; Pirzadeh, Homa; Stinson, Douglas

    2011-03-01

    A novel MoXyTM fiber delivery device with Active Cooling Cap (ACCTM) is designed to transmit up to 180W of 532 nm laser light to treat benign prostatic hyperplasia (BPH). Under such high power tissue ablation, effective cooling is key to maintaining fiber power transmission and ensuring the reliability of the fiber delivery device To handle high power and reduce fiber degradation, the MoXy fiber features a larger core size (750 micrometer) and an internal fluid channel to ensure better cooling of the fiber tip to prevent the cap from burning, detaching, or shattering during the BPH treatment. The internal cooling channel was created with a metal cap and tubing that surrounds the optical fiber. In this study MoXy fibers were used to investigate the effect of power levels of 120 and 200 W on in-vitro bovine prostate ablation using a 532 nm XPSTM laser system. For procedures requiring more than 100 kJ, the MoXy fiber at 200W removed tissue at twice the rate of the current HPS fiber at 120W. The fiber maintained a constant tissue vaporization rate during the entire tissue ablation process. The coagulation at 200W was about 20% thicker than at 120W. In conclusion, the new fibers at 200W doubled the tissue removal rate, maintained vaporization efficiency throughout delivery of 400kJ energy, and induced similar coagulation to the existing HPS fiber at 120W.

  17. Effect of laser power on orientation and microstructure of Ba2TiO4 film prepared by laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Guo, Dongyun; Goto, Takashi; Wang, Chuanbin; Shen, Qiang; Zhang, Lianmeng

    2012-08-01

    Ba2TiO4 films were prepared on Pt/Ti/SiO2/Si substrates by laser chemical vapor deposition method. The effect of laser power (PL) on orientation and microstructure was investigated. With increasing PL from 52 to 93 W, the deposition temperature (Tdep) increased from 845 to 946 K. With increasing Tdep from 845 to 927 K, the preferred orientation of Ba2TiO4 films changed from (0 9 1) to (1 0 3), the surface morphologies changed from faceted to rectangular, and the columnar cross-section became thicker. The films prepared at high Tdep (931-946 K) had the porous cross-section consisted of powder-like grains. Ba2TiO4 film prepared at 881 K had high deposition rate (Rdep) of 51.4 μm h-1, which was advantageous to industrial production.

  18. AMTEC vapor-vapor series connected cells

    NASA Technical Reports Server (NTRS)

    Underwood, Mark L. (Inventor); Williams, Roger M. (Inventor); Ryan, Margaret A. (Inventor); Nakamura, Barbara J. (Inventor); Oconnor, Dennis E. (Inventor)

    1995-01-01

    An alkali metal thermoelectric converter (AMTEC) having a plurality of cells structurally connected in series to form a septum dividing a plenum into two chambers, and electrically connected in series, is provided with porous metal anodes and porous metal cathodes in the cells. The cells may be planar or annular, and in either case a metal alkali vapor at a high temperature is provided to the plenum through one chamber on one side of the wall and returned to a vapor boiler after condensation at a chamber on the other side of the wall in the plenum. If the cells are annular, a heating core may be placed along the axis of the stacked cells. This arrangement of series-connected cells allows efficient generation of power at high voltage and low current.

  19. 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.

  20. The influence of water vapor on atmospheric exchange measurements with an ICOS* based Laser absorption analyzer

    NASA Astrophysics Data System (ADS)

    Bunk, Rüdiger; Quan, Zhi; Wandel, Matthias; Yi, Zhigang; Bozem, Heiko; Kesselmeier, Jürgen

    2014-05-01

    Carbonyl sulfide and carbon monoxide are both atmospheric trace gases of high interest. Recent advances in the field of spectroscopy have enabled instruments that measure the concentration of the above and other trace gases very fast and with good precision. Increasing the effective path length by reflecting the light between two mirrors in a cavity, these instruments reach impressive sensitivities. Often it is possible to measure the concentration of more than one trace gas at the same time. The OCS/CO2 Analyzer by LGR (Los Gatos Research, Inc.) measures the concentration of water vapor [H2O], carbonyl sulfide [COS], carbon dioxide [CO2] and carbon monoxide [CO] simultaneously. For that the cavity is saturated with light, than the attenuation of light is measured as in standard absorption spectroscopy. The instrument proved to be very fast with good precision and to be able to detect even very low concentrations, especially for COS (as low as 30ppt in the case of COS). However, we observed a rather strong cross sensitivity to water vapor. Altering the water vapor content of the sampled air with two different methods led to a change in the perceived concentration of COS, CO and CO2. This proved especially problematic for enclosure (cuvette) measurements, where the concentrations of one of the above species in an empty cuvette are compared to the concentration of another cuvette containing a plant whose exchange of trace gases with the atmosphere is of interest. There, the plants transpiration leads to a large difference in water vapor content between the cuvettes and that in turn produces artifacts in the concentration differences between the cuvettes for the other above mentioned trace gases. For CO, simultaneous measurement with a UV-Emission Analyzer (AL 5002, Aerolaser) and the COS/CO Analyzer showed good agreement of perceived concentrations as long as the sample gas was dry and an increasing difference in perceived concentration when the sample gas was

  1. Open-path atmospheric transmission for a diode-pumped cesium laser.

    PubMed

    Rice, Christopher A; Lott, Gordon E; Perram, Glen P

    2012-12-01

    A tunable diode laser absorption spectroscopy device was developed to study atmospheric propagation for emerging high-energy laser weapons. The cesium diode-pumped alkali laser operates near 895 nm in the vicinity of several water-vapor absorption lines. Temperature, pressure, and water vapor concentration were determined for 150 m and 1 km open paths with statistical errors of ∼0.2%. Comparison with meteorological instruments yields agreement for the 1 km path to within 0.6% for temperature, 3.7% for pressure, and 2.4% for concentration. PMID:23207380

  2. Structure and Dynamics of Tunneling and Laser - Defects in Alkali Halides as Studied by a Behavior Type Analysis of the Polarized Raman Scattering.

    NASA Astrophysics Data System (ADS)

    Joosen, Wim M. C.

    It is demonstrated that proper analysis of polarized Raman spectra of defects in alkali halides by means of the Behavior Type (BT) method allows a detailed description of defect dynamics. The recently developed BT method provides a systematic procedure to distinguish, among the 125 Raman -active modes of the 33 possible point groups of a defect in a cubic lattice, the Raman modes which are consistent with the polarized Raman data, from those which are not. The efficiency of the BT method was shown in the interpretation of the low frequency Raman mode at 43 cm ^{-1} of the Li ^+ off-center impurity in KCl, which was attributed to a collective motion of the surrounding chlorine ions. This experimental finding inspired us to calculate the time dependent phonon autocorrelation function of a coupled spin-phonon system, which explains the anomalous isotope shift of the low frequency mode. We also studied the hydrogen-tagged Li ^+ center in KCl, which performs a correlated tunneling motion and put forward a defect model, in which the Li^+ ion and the hydrogen atom are both accommodated on the same cation site and displaced along <111> in opposite directions. There is no preferential molecular bond of any consequence between them. Our picture modifies the model based on electron spin resonance measurements, in which the H^{0}Li ^+ center is considered as a (LiH) ^+ molecular system. The Tl^0(1) defect is the first laser-center of the atomic type investigated with the Raman technique. The polarized Raman spectra, were excited in the third optical band of Tl^0 (1) and show that this transition is broadened by A_1-modes of the C_ {rm 4v} defect symmetry. We distinguished an induced first order spectrum, shown to be characteristic for the KCl lattice, and a low frequency vibration at about 30 cm^{-1}, which reflects the motion of the thallium atom along the fourfold axis. The Tl^+Tl^0 (1) center provided a first test-case for the extended BT method for resonant Raman

  3. Optically pumped gas laser using electronic transitions in the NaRb molecule

    SciTech Connect

    Kaslin, V.M.; Yakushev, O.F.

    1983-12-01

    Laser superradiance was achieved for the first time as a result of an electronic transition in a diatomic heteronuclear molecule as a result of direct optical pumping. This superradiance was observed in the region of 670 nm due to a transition to the ground state X/sup 1/..sigma../sup +/ of the intermetallic alkali molecule NaRb pumped by radiation from a pulsed copper vapor laser (lambda = 510.6 nm).

  4. Dynamics of vapor plume in transient keyhole during laser welding of stainless steel: Local evaporation, plume swing and gas entrapment into porosity

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Chen, Xin; Shao, Xinyu; Gong, Shuili; Xiao, Jianzhong

    2016-07-01

    In order to better understand the local evaporation phenomena of keyhole wall, vapor plume swing above the keyhole and ambient gas entrapment into the porosity defects, the 3D time-dependent dynamics of the metallic vapor plume in a transient keyhole during fiber laser welding is numerically investigated. The vapor dynamical parameters, including the velocity and pressure, are successfully predicted and obtain good agreements with the experimental and literature data. It is found that the vapor plume flow inside the keyhole has complex multiple directions, and this various directions characteristic of the vapor plume is resulted from the dynamic evaporation phenomena with variable locations and orientations on the keyhole wall. The results also demonstrate that because of this dynamic local evaporation, the ejected vapor plume from the keyhole opening is usually in high frequency swinging. The results further indicate that the oscillation frequency of the plume swing angle is around 2.0-8.0 kHz, which is of the same order of magnitude with that of the keyhole depth (2.0-5.0 kHz). This consistency clearly shows that the swing of the ejected vapor plume is closely associated with the keyhole instability during laser welding. Furthermore, it is learned that there is usually a negative pressure region (several hundred Pa lower than the atmospheric pressure) of the vapor flow around the keyhole opening. This pressure could lead to a strong vortex flow near the rear keyhole wall, especially when the velocity of the ejected metallic vapor from the keyhole opening is high. Under the effect of this flow, the ambient gas is involved into the keyhole, and could finally be entrapped into the bubbles within a very short time (<0.2 ms) due to the complex flow inside the keyhole.

  5. Ambient Molecular Analysis of Biological Tissue Using Low-Energy, Femtosecond Laser Vaporization and Nanospray Postionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Shi, Fengjian; Flanigan, Paul M.; Archer, Jieutonne J.; Levis, Robert J.

    2016-03-01

    Direct analysis of plant and animal tissue samples by laser electrospray mass spectrometry (LEMS) was investigated using low-energy, femtosecond duration laser vaporization at wavelengths of 800 and 1042 nm followed by nanospray postionization. Low-energy (<50 μJ), fiber-based 1042 nm LEMS (F-LEMS) allowed interrogation of the molecular species in fresh flower petal and leaf samples using 435 fs, 10 Hz bursts of 20 pulses from a Ytterbium-doped fiber laser and revealed comparable results to high energy (75-1120 μJ), 45 fs, 800 nm Ti:Sapphire-based LEMS (Ti:Sapphire-LEMS) measurements. Anthocyanins, sugars, and other metabolites were successfully detected and revealed the anticipated metabolite profile for the petal and leaf samples. Phospholipids, especially phosphatidylcholine, were identified from a fresh mouse brain section sample using Ti:Sapphire-LEMS without the application of matrix. These lipid features were suppressed in both the fiber-based and Ti:Sapphire-based LEMS measurements when the brain sample was prepared using the optimal cutting temperature compounds that are commonly used in animal tissue cryosections.

  6. Ambient Molecular Analysis of Biological Tissue Using Low-Energy, Femtosecond Laser Vaporization and Nanospray Postionization Mass Spectrometry.

    PubMed

    Shi, Fengjian; Flanigan, Paul M; Archer, Jieutonne J; Levis, Robert J

    2016-03-01

    Direct analysis of plant and animal tissue samples by laser electrospray mass spectrometry (LEMS) was investigated using low-energy, femtosecond duration laser vaporization at wavelengths of 800 and 1042 nm followed by nanospray postionization. Low-energy (<50 μJ), fiber-based 1042 nm LEMS (F-LEMS) allowed interrogation of the molecular species in fresh flower petal and leaf samples using 435 fs, 10 Hz bursts of 20 pulses from a Ytterbium-doped fiber laser and revealed comparable results to high energy (75-1120 μJ), 45 fs, 800 nm Ti:Sapphire-based LEMS (Ti:Sapphire-LEMS) measurements. Anthocyanins, sugars, and other metabolites were successfully detected and revealed the anticipated metabolite profile for the petal and leaf samples. Phospholipids, especially phosphatidylcholine, were identified from a fresh mouse brain section sample using Ti:Sapphire-LEMS without the application of matrix. These lipid features were suppressed in both the fiber-based and Ti:Sapphire-based LEMS measurements when the brain sample was prepared using the optimal cutting temperature compounds that are commonly used in animal tissue cryosections. PMID:26667178

  7. Laser Velocimeter for Studies of Microgravity Combustion Flowfields

    NASA Technical Reports Server (NTRS)

    Varghese, P. L.; Jagodzinski, J.

    2001-01-01

    We are currently developing a velocimeter based on modulated filtered Rayleigh scattering (MFRS), utilizing diode lasers to make measurements in an unseeded gas or flame. MFRS is a novel variation of filtered Rayleigh scattering, utilizing modulation absorption spectroscopy to detect a strong absorption of a weak Rayleigh scattered signal. A rubidium (Rb) vapor filter is used to provide the relatively strong absorption and semiconductor diode lasers generate the relatively weak Rayleigh scattered signal. Alkali metal vapors have a high optical depth at modest vapor pressures, and their narrow linewidth is ideally suited for high-resolution velocimetry; the compact, rugged construction of diode lasers makes them ideally suited for microgravity experimentation. Molecular Rayleigh scattering of laser light simplifies flow measurements as it obviates the complications of flow-seeding. The MFRS velocimeter should offer an attractive alternative to comparable systems, providing a relatively inexpensive means of measuring velocity in unseeded flows and flames.

  8. Carbon dioxide laser vaporization: Relationship of scar formation to power density

    SciTech Connect

    Dobry, M.M.; Padilla, R.S.; Pennino, R.P.; Hunt, W.C.

    1989-07-01

    A direct relationship exists between the power density of a carbon dioxide laser and the thickness of scars it produces in rat skin. Statistically significant positive relationships were noted between laser power and scar thickness at days 14, 21, and 32. The slope of the curve increased as the number of days elapsed. At day 32, the ratio of scar thickness to CO/sub 2/ laser power density delivered was 0.3 microns/W-cm/sup 2/. Scar formation took longer for completion at higher wattages of irradiation.

  9. A computational model for transient temperature rise in a dye laser gain medium pumped by a copper vapor laser

    NASA Astrophysics Data System (ADS)

    Rawat, V. S.; Gantayet, L. M.; Sridhar, G.; Singh, S.

    2014-02-01

    Spectrally stable dye lasers play an important role in techniques based on high resolution spectroscopy and atomic spectroscopy. The spectral purity of a dye laser is affected when the pump power to it is increased beyond the threshold. When the pump power is increased beyond the threshold, two mode oscillations occur which decrease the spectral purity of the dye laser. The effect of higher pump pulse energies on transient thermal effects has been studied using a computational fluid dynamics (CFD) model and the disturbances to the laser cavity have been studied using commercially available ray tracing software. The change in the cavity length was determined from the CFD model for several dye concentrations and pump powers. The results of the CFD model have been verified by published results and experimental results from our system. Our study shows that in the longitudinally pumped single mode laser change in the cavity length is a more dominant disturbance than thermal blooming. Our model is useful for the design of the dye cell.

  10. Efficient laser systems for 935 and 942 nm for water vapor lidar

    NASA Astrophysics Data System (ADS)

    Eichler, Hans Joachim; Kallmeyer, Frank; Rhee, Hanjo; Riesbeck, Thomas; Strohmaier, Stephan

    2007-05-01

    Water vapour absorption wavelengths have been directly generated by diode pumped Nd:YGG crystals emitting at 935 nm and with Nd:GSAG crystals emitting at 942 nm in cw and pulsed operation. In addition the 1064 nm fundamental wavelength from Nd:YAG pump lasers with pulse lengths of 10 or 20 ns was shifted using Stimulated Raman Scattering (SRS) or Ti:Sapphire (TiSa) lasers. The potential of Nd:GSAG, Nd:YGG, SRS and TiSa laser systems is compared for future incorporation into a satellite based Lidar system. High output energies are possible by recent advances of fiber coupled diode sources allowing pulsed longitudinal pumping of Q-switched solid state lasers.

  11. Laser induced chemical vapor deposition of Ni by decomposition of Ni(CO)4

    NASA Astrophysics Data System (ADS)

    Kräuter, W.; Bäuerle, D.; Fimberger, F.

    1983-05-01

    Polycrystalline Ni has been grown by decomposition of Ni(CO)4 using different wavelengths of the visible radiation of a Kr+ laser. The influence of laser irradiance, substrate material and scanning velocity on deposition rate and widths of patterns has been investigated. The deposition rates achieved are typically several μm/s, and the lateral dimensions of the deposits can be as small as 1 μm.

  12. A Comparison of the Effects of RF Plasma Discharge and Ion Beam Supply on the Growth of Cubic Boron Nitride Films Formed by Laser Physical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Kaneda, Kayo; Shibata, Kimihiro

    1994-01-01

    This paper presents a comparison of the effects of RF plasma discharge and ion beam supply on the growth of cubic boron nitride films formed by excimer laser physical vapor deposition (laser PVD). The film structure was analyzed by fourier transformation infrared region (FT-IR) spectroscopy and thin-film X-ray diffraction analysis. The structure of the film deposited with an RF plasma discharge provided between the substrate and target was hexagonal BN. On the other hand, that of the film deposited by irradiating the substrate directly with an ion beam was hexagonal BN (hBN) and cubic BN (cBN). It is thought that direct irradiation of the vapor generated from the target by accelerated ions increased the activation energy of the vapor, with the result that the film structure was changed. Besides irradiating the substrate directly with the ion beam resulted primarily in the etching of hBN while cBN remained.

  13. Self-generating magnetometer with laser pumping employment in “end resonance” wall coated vapor cell atomic clocks

    NASA Astrophysics Data System (ADS)

    Baranov, A. A.; Ermak, S. V.; Smolin, R. V.; Semenov, V. V.

    2016-06-01

    This paper presents the results of two double resonance signals correlation investigation. These signals were observed synchronously in optically oriented Rb87 vapors with laser pumping in a dual scheme: low frequency Mx-magnetometer and microwave frequency discriminator. Analytical studies of the scalar and vector light shift components contribution to the frequency instability of the end resonance microwave transitions are presented. An experimental demonstration of the light shift components mutual compensation in optically pumped Rb87 atoms was provided. The results were processed in terms of Allan variance, which demonstrated an effect of decreasing frequency variation at averaging times more than 100 s for a joint scheme of the end resonance microwave transition and selfgenerating (Mx) magnetometer.

  14. Operational efficiency increase in a copper vapor laser due to the replacement of vacuum jacket brewster windows with flat windows

    NASA Technical Reports Server (NTRS)

    Estep, Lee; Witherspoon, Ned; Holloway, John; Price, Brian; Miller, Robert

    1989-01-01

    The vacuum integrity of the discharge tube of a copper vapor laser (CVL) is normally protected by Brewster angled windows. In an attempt to increase the operating efficiency of the CVL, flat windows were used to replace the Brewster windows. Experimental data confirm that the overall efficiency of the CVL does increase when such windows are used. The experimental results are discussed in terms of a computer model found in the literature. The cause of the efficiency increase appears due to a double optical cavity set up by the flat windows. However, the variation of the efficiency due to changes in the pulse repetition frequency (PRF) and buffer gas pressure are less well understood.

  15. Measurements of the divergence evolution of a copper-vapor laser output by using a cylindrical imaging technique.

    PubMed

    Coutts, D W; Brown, D J; Piper, J A

    1993-04-20

    The temporal evolution of divergence of the output of a copper-vapor laser (CVL) operating with a high-magnification (M = 26.5) unstable resonator is measured by using a one-dimensional imaging system together with a fast gated linear diode array detector. The CVL output is found to consist of several temporally resolved components, with each successive component having lower divergence. The final component of the output has essentially diffraction-limited divergence. The divergence behavior is modeled by using an unfolded resonator-equivalent lens guide, with geometric constraints on the propagation of spontaneous emission within the lens guide, and is found to match the experimentally determined behavior. PMID:20820343

  16. Computational study of collisional energy transfer and quasi-continuous population inversions in laser-pumped Ca vapor

    NASA Astrophysics Data System (ADS)

    Khan, M. A.; Rafique, M.

    1995-12-01

    A computational study of population inversion between several pairs of excited states viz 3 d4 p 3 F-4 s3 d 3 D, 4 s5 s 3 S-4 s4 p 3 P and 4 s3 d 3 D-4 s4 p 3 P in Ca vapor pumped on the 4 s 2 1 S 0-4 s4 p 3 P 1 transition is presented. The main aim is to investigate the influence of various atomic processes in creating and sustaining the population inversion for long times after the excitation pulse. The delicate interplay between superelastic energy transfer to free electrons, energy pooling collisions and cascaded recombination is particulary examined. It is noted that quasi-continuous population inversion can be readily excited on the 4 s3 d 3 D-4 s4 p 3 P transitions; and under some conditions, also on the 4 s5 s 3 S-4 s4 p 3 P transitions. Furthermore, inversion on the 3 d4 p 3 F-4 s3 d 3 D transitions can also be excited for a considerable length of time. The results may be useful in designing and developing quasi-cw metal vapor lasers.

  17. Ultrasonic coal washing to leach alkali elements from coals.

    PubMed

    Balakrishnan, S; Reddy, V Midhun; Nagarajan, R

    2015-11-01

    Deposition of fly ash particles onto heat-transfer surfaces is often one of the reasons for unscheduled shut-downs of coal-fired boilers. Fouling deposits encountered in convective sections of a boiler are characterized by arrival of ash particles in solidified (solid) state. Fouling is most frequently caused by condensation and chemical reaction of alkali vapors with the deposited ash particles creating a wet surface conducive to collect impacting ash particles. Hence, the amount of alkali elements present in coals, which, in turn, is available in the flue gas as condensable vapors, determines the formation and growth of fouling deposits. In this context, removal of alkali elements becomes vital when inferior coals having high-ash content are utilized for power generation. With the concept of reducing alkali elements present in a coal entering the combustor, whereby the fouling deposits can either be minimized or be weakened due to absence of alkali gluing effect, the ultrasonic leaching of alkali elements from coals is investigated in this study. Ultrasonic water-washing and chemical-washing, in comparison with agitation, are studied in order to estimate the intensification of the alkali removal process by sonication. PMID:26186840

  18. Effects of copper vapor laser (CVL) on mice skin: histologic evaluation of damage and tissue stimulation

    NASA Astrophysics Data System (ADS)

    Nunes, Syllene; Moreno, E.; Oliveira, H.; Osaka, J.; Salvador, G.; Michalany, N.; Tolosa, E.

    2002-10-01

    This study was to evaluate the effects of the CVL with low energy and short pulse widths. 18 female mice, C57BL/6 (9-11 weeks old) were distributed into four groups. The control group (CG) wasn't exposed to laser beam . Group L1 had 2 laser expositions with 24 hours gap between them (0.5W). Group L2 had 3 expositions (0.5W and 0.25W) and group L3 had 4 expositions (0.25 W). It was used a CVL prototype (5lOnm, 13 Khz, pulse width of 20 ms and spot size of 0.8cm). 7 days after last laser pulse no groups presented actinic keratosis, tumors or collagen changes. CVL had effective action on pilosebaceous units. High energy with few short pulses induced hair follicles proliferation while low energy with many repetitive short pulses showed increased and specific tissue damage besides hair plugging.

  19. Fiber optic-based laser vapor screen flow visualization systems for aerodynamic research in larger-scale subsonic and transonic wind tunnels

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.; Inenaga, Andrew S.

    1992-01-01

    The design, installation, and application of the NASA laser vapor screen (LVS) flow visualization systems developed by 10-foot high speed tunnel and 8-foot transonic pressure tunnel are discussed. Sufficient quantity of water is injected into the wind tunnel diffuser section to increase the relative humidity and promote condensation of the water vapor in the flow field about the model. Vortex-dominated flows are illuminated with an intense sheet of laser light. Fiber optics are used to deliver the laser beam through the plenum shell that surrounds the test section of each facility and to the light sheet-generating optics positioned in the ceiling window of the test section. Operational experience indicates that fiber optic-based systems are safe, reliable, and capable of proving high-quality off-surface flow visualization in larger scale subsonic and transonic wind tunnels.

  20. Development of Solid State Laser Materials for Application in Lasers for Atmospheric Ozone and Water Vapor Sensing

    NASA Technical Reports Server (NTRS)

    Noginov, Makhail A.; Loutts, G. B.

    2002-01-01

    We have grown neodymium doped mixed apatite crystals, (Sr(x)Ba(l-x)5(PO4)3F, Sr5(P(1-x)V(x)O4)3F, and Ba5(P(1-x)V(x)O4)3F, and spectroscopically studied them as potential gain media for a laser source for atmospheric water sensing operating at 944.11 nm0. We conclude that an appropriate apatite host material for a 944.11 nm laser should be a mixture of Sr5(PO4)3F with a small fraction of Ba5(PO4)3F. The precise wavelength tuning around 944.11 nm can be accomplished by varying the host composition, temperature, and threshold population inversion. In apatite crystals of mixed composition, the Amplified Spontaneous Emission (ASE) loss at 1.06 microns is predicted to be significantly smaller than that in the end members.

  1. Simultaneous atmospheric nitrous oxide, methane and water vapor detection with a single continuous wave quantum cascade laser.

    PubMed

    Cao, Yingchun; Sanchez, Nancy P; Jiang, Wenzhe; Griffin, Robert J; Xie, Feng; Hughes, Lawrence C; Zah, Chung-en; Tittel, Frank K

    2015-02-01

    A continuous wave (CW) quantum cascade laser (QCL) based absorption sensor system was demonstrated and developed for simultaneous detection of atmospheric nitrous oxide (N(2)O), methane (CH(4)), and water vapor (H(2)O). A 7.73-µm CW QCL with its wavelength scanned over a spectral range of 1296.9-1297.6 cm(-1) was used to simultaneously target three neighboring strong absorption lines, N(2)O at 1297.05 cm(-1), CH(4) at 1297.486 cm(-1), and H(2)O at 1297.184 cm(-1). An astigmatic multipass Herriott cell with a 76-m path length was utilized for laser based gas absorption spectroscopy at an optimum pressure of 100 Torr. Wavelength modulation and second harmonic detection was employed for data processing. Minimum detection limits (MDLs) of 1.7 ppb for N(2)O, 8.5 ppb for CH(4), and 11 ppm for H(2)O were achieved with a 2-s integration time for individual gas detection. This single QCL based multi-gas detection system possesses applications in environmental monitoring and breath analysis. PMID:25836083

  2. Highly uniform and reproducible vertical-cavity surface emitting lasers grown by metalorganic chemical vapor deposition

    SciTech Connect

    Hou, H.Q.; Chui, H.C.; Choquette, K.D.; Hammons, B.E.; Breiland, W.G.; Geib, K.M.

    1996-01-01

    We show that the uniformity of the lasing wavelength of vertical-cavity surface emitting lasers (VCSELs) can be as good as {plus_minus}0.3% across a entire 3 in. wafer in MOCVD growth with a similar run-to-run reproducibility.

  3. Laser-induced vapor nanobubbles for efficient delivery of macromolecules in live cells

    NASA Astrophysics Data System (ADS)

    Xiong, Ranhua; Raemdonck, Koen; Peynshaert, Karen; Lentacker, Ine; De Cock, Ine; Demeester, Jo; De Smedt, Stefaan C.; Skirtach, Andre G.; Braeckmans, Kevin

    2015-03-01

    Macromolecular agents such as nucleic acids and proteins need to be delivered into living cells for therapeutic purposes. Among physical methods to deliver macromolecules across the cell membrane, laser-induced photoporation using plasmonic nanoparticles is a method that is receiving increasing attention in recent years. By irradiating gold nanoparticles bound to the cell membrane with laser light, nanosized membrane pores can be created. Pores are formed by localized heating or by vapour nanobubbles (VNBs) depending on the incident laser energy. Macromolecules in the surrounding cell medium can then diffuse through the transiently formed pores into the cytoplasm. While both heating and VNBs have been reported before for permeabilization of the cell membrane, it remains unclear which of both methods is more efficient in terms of cell loading with minimal cytotoxicity. In this study we report that under condition of a single 7 ns laser pulse VNBs are substantially more efficient for the cytosolic delivery of macromolecules. We conclude that VNB formation is an interesting photoporation mechanism for fast and efficient macromolecular delivery in live cells.

  4. Laser photochemical growth of amorphous silicon at low temperatures and comparison with thermal chemical vapor deposition

    SciTech Connect

    Eres, D.; Lowndes, D.H.; Geohegan, D.B.; Mashburn, D.N.

    1987-01-01

    Pulsed ArF (193 nm) excimer laser radiation has been used to dissociate disilane (Si/sub 2/H/sub 6/, resulting in photochemically controlled deposition of amorphous Si thin films. A high stability HeNe (6328 A) laser was used for precise in situ monitoring of film deposition rates, under varying deposition conditions. A helium window purge nearly eliminated Si film deposition on the chamber windows. With the excimer laser beam parallel to the substrate, deposition of amorphous Si can be controlled entirely by the photon fluence (negligible background thermal growth) at temperatures from room temperature up to /approximately/400/degree/C. Reasonable photolytic deposition rate (>1 A/sec) are combined with 'digital' control of film thickness (/approx gt/0.02 A/laser pulse). Activation energies of 1.50 (+-0.1) eV and 0.09 (+-0.02) eV were found for pyrolytic and photolytic deposition, respectively. 15 refs., 3 figs.

  5. Suitability of laser-induced breakdown spectroscopy in screening potential additives to mitigate fouling deposits

    NASA Astrophysics Data System (ADS)

    Balakrishnan, S.; Midhun Reddy, V.; Mehta, A.; Vasa, N. J.; Nagarajan, R.

    2016-04-01

    Alkali vapors present in the flue gas generated during coal-based combustion form fouling deposits as they condense. An additive added to coal can trap alkali elements in ash, therefore suppress the growth rate of fouling deposits, and increase thermal efficiency of a coal-fired thermal power plant. Laser-induced breakdown spectroscopy (LIBS) technique is proposed and demonstrated to screen potential additives to trap alkali elements in ash. Five additives—namely, kaolinite, alumina, silica, magnesia, and pumice—were analyzed for their effectiveness on four Indian coals for retaining/confining alkali elements in ash during coal combustion. Ratio analysis based on LIBS emission intensity values clearly shows that kaolinite and pumice are promising additives to trap sodium. Similarly, kaolinite, pumice, and silica exhibited good potassium retention.

  6. Systematics of Alkali and PB Abundances in Meteoritic and Lunar Samples

    NASA Astrophysics Data System (ADS)

    Kita, N. T.

    1996-03-01

    The alkali depletion is not a unique characteristic of the moon, but is common to eucrites, angrites, and the earth. Because the moon and the earth are depleted in more volatile Pb in a similar degree to both chondrites and achondrites, it is hard to assume that alkali depletion was caused by vaporization loss during the giant impact event. Alkali and volatile depletion might have originated from their source material which accreted to the planets.

  7. Far wing depolarization of light - Generalized absorption profiles. [in laser fluorescence spectroscopy of Sr vapor

    NASA Technical Reports Server (NTRS)

    Thomann, P.; Burnett, K.; Cooper, J.

    1981-01-01

    An absorption (and/or emission) event which takes place during a strong collision is called a 'correlated event'. It is discussed how correlated events affect the far red wing depolarization of fluorescence. Attention is given to an atomic vapor which is irradiated by linearly polarized light of a frequency on the red side of the resonance line. Two limiting cases are considered, corresponding to excitation in the impact region and in the quasi-static wing. In the quasi-static wing, absorption of a photon followed by fluorescence (rather than Rayleigh scattering), occurs mostly during a collision. Correlated events dominate the scattering process. Expressions derived for the polarization of the fluorescent light are applied to far red wing depolarization. It is found that the polarization of the fluorescent light does not go to zero in the far wing, but depends crucially on the detailed nature of the anisotropy in the long-range part of the interatomic potential.

  8. A search for chemical laser action in low pressure metal vapor flames. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Zwillenberg, M. L.

    1975-01-01

    Optical emissions were studied from low pressure (approximately 1 torr) dilute diffusion flames of Ca and Mg vapor with O2, N2O and mixtures of CCl4 and O2. The Ca flames with O2 and N2O revealed high vibrational excitation of the product CaO molecule (up to v=30). The flames with CCl4 revealed extreme nonequilibrium metal atom electronic excitation, up to the metal atom ionization limit (6.1 eV for Ca, 7.6 eV for Mg). The metal atom excited electronic state populations did not follow a Boltzmann distribution, but the excitation rates ('pumping rate') were found to obey an Arrhenius-type expression, with the electronic excitation energy playing the role of activation energy and a temperature of about 5000 K for triplet excited states and 2500 K for singlets (vs. approximately 500 K translational temperature).

  9. Progress Toward an Autonomous Field Deployable Diode Laser Based Differential Absorption Lidar (DIAL) for Profiling Water Vapor in the Lower Troposphere

    NASA Astrophysics Data System (ADS)

    Repasky, K. S.; Spuler, S.; Nehrir, A. R.; Moen, D.

    2013-12-01

    Water vapor is the most dominant greenhouse gas in the atmosphere and plays an important role in many key atmospheric processes associated with both weather and climate. Water vapor is highly variable in space and time due to large scale transport and biosphere-atmosphere interactions. Having long-term, high-resolution, vertical profiles of water vapor will help to better understand the water vapor structure and variability and its associated impact on weather and climate. A diode laser based differential absorption lidar (DIAL) for full-time water vapor and aerosol profiling in the lower troposphere has been demonstrated at Montana State University. This prototype instrument has the potential to form the basis of a ground based network of eye-safe autonomous instruments that can provide important information on the spatial and temporal variability of water vapor in the lower troposphere. To achieve this potential, major improvements to the prototype instrument need to be implemented and demonstrated including developing a laser transmitter capable of long term operation and modifying the optical receiver to make measurement below 0.5 km. During the past year, work on incorporating a new laser transmitter based on two distributed Bragg reflector (DBR) diode lasers, one operating at the on-line/side-line wavelength and the second operating at the off-line wavelength to injection seed a tapered semiconductor optical amplifier (TSOA) in a master oscillator power amplifier (MOPA) configuration has been completed. Recent work on the optical receiver is driven by the fact that the majority of the atmospheric water vapor resides below 2 km. The current single channel DIAL receiver has a narrow field of view and does not come in to full overlap until approximately 2 km. A two channel DIAL receiver has been designed that will allow the DIAL to achieve full overlap at ranges of less the 0.5 km providing significant improvement to the instrument performance. A discussion of

  10. Influence of laser power on the orientation and microstructure of CeO 2 films deposited on Hastelloy C276 tapes by laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Ito, Akihiko; Tu, Rong; Goto, Takashi

    2010-08-01

    CeO 2 films were prepared on LaMnO 3/MgO/Gd 2Zr 2O 7 multi-coated Hastelloy C276 tapes by laser chemical vapor deposition at different laser power ( PL) from 46 to 101 W. Epitaxial (1 0 0) CeO 2 films were prepared at PL = 46-93 W (deposition temperature, Tdep = 705-792 K). Epitaxial CeO 2 films had rectangular-shaped grains at PL = 46-77 W ( Tdep = 705-754 K), while square-shaped grains were obtained at PL = 85-93 W ( Tdep = 769-792 K). CeO 2 films showed a columnar microstructure. Epitaxial (1 0 0) CeO 2 films with rectangular grains exhibited full width at half maximum of ω-scan on (2 0 0) reflection and ϕ-scan on (2 2 0) reflection of 3.4-3.2° and 6.0-7.2°, respectively. The deposition rate of the epitaxial (1 0 0) CeO 2 films had a maximum of 4.6 μm h -1 at PL = 77 W ( Tdep = 754 K).

  11. Performance comparison of nonlinear crystals for frequency doubling of an 894nm Cs vapor laser

    NASA Astrophysics Data System (ADS)

    Zhdanov, B. V.; Shaffer, M. K.; Lu, Y.; Naumann, B.; Genda, T.; Knize, R. J.

    2010-11-01

    An examination of the efficiencies of three commonly used nonlinear crystals (PPKTP, LBO, and BiBO) when generating second harmonic of a Cesium laser is presented. The experiment investigates both the intracavity and single pass second harmonic generation of 895 nm Cs laser light when operating in quasi-CW and in CW modes and pumped by several watts. A degradation of the conversion efficiencies for each crystal was observed when high fundamental powers or a high duty cycle of the pump were used. For a Cs laser operating at 894nm, PPKTP is found to be the optimal crystal for intracavity SHG in both pulsed and CW modes when operating at SHG powers of several watts. At higher powers, however, the increased absorption coefficient of PPKTP at 447nm, compared to that of BiBO or LBO, may become significant to where another crystal will be more appropriate for this application. Maximum blue light power obtained with PPKTP crystal was about 1.5W in CW mode and 2.5W in QCW.

  12. Kr/sup +/ laser-induced chemical vapor deposition of W

    SciTech Connect

    Zhang, G.Q.; Szoerenyi, T.; Baeuerle, D.

    1987-07-15

    Kr/sup +/ laser-induced pyrolytic direct writing of W stripes by H/sub 2/ reduction of WF/sub 6/ has been investigated. The reproducibility of the process and the morphology and electrical properties of deposits depend heavily on the partial pressures of both WF/sub 6/ and H/sub 2/; the best results have been obtained with p(WF/sub 6/) = 5 mbar and 100 mbarless than or equal top(H/sub 2/)less than or equal to800 mbar. For a laser focus of 2w/sub 0/ = 7 ..mu..m and laser powers between 30 and 200 mW, the widths of stripes varied between 1.5 and 15 ..mu..m with corresponding thicknesses between 0.1 to 3 ..mu..m. The width of stripes is independent of the scanning speed within the range 20 ..mu..m/sless than or equal toV/sub s/ less than or equal to400 ..mu..m/s. The electrical resistivities of these stripes were about a factor of 1.3--2.3 larger than the bulk value.

  13. [Measurement of Mole Ratio for Alkali Metal Mixture by Using Spectral Absorption Method].

    PubMed

    Zou, Sheng; Zhang, Hong; Chen, Yao; Chen, Xi-yuan

    2015-08-01

    The ratio of alkali metal mixture is one of the most important parameters in gauge head belonging to the ultra-sensitivity inertial measurement equipment, which is required to detect precisely. According to the feature that ratio of alkali metal is related to alkali metal vapor density, the theory of optical depth is used to detect the ratio of alkali metal in the present article. The result shows that the data got by the theory of optical depth compared with empirical formula differs at three orders of magnitude, which can't ensure the accuracy. By changing the data processing method, model between spectral absorption rate and temperature in cell is established. The temperature in alkali metal cell is calibrated by spectral absorption rate. The ratio of alkali metal atoms in the cell is analyzed by calculating the alkali density with empirical formula. The computational error is less than 10%. PMID:26672309

  14. Lasing on the electronic B--X transition of the I/sub 2/ molecule optically pumped by a copper-vapor laser

    SciTech Connect

    Kaslin, V.M.; Petrash, G.G.; Yakushev, O.F.

    1980-04-01

    It is proposed to use pulsed metal-vapor lasers for optical pumping of gas lasers based on electronic transitions of molecules. This uncovers prospects for the development of effective lasers with high average and peak power, which are tunable in the visible and in the infrared. The first step in this direction are experiments on optical pumping of molecular iodine by a copper-vapor laser (lambda=5106 and 5782 A). Results of spectroscopic investigations are reported. It was found that the pumping is by five absorption lines of the X/sup 1/..sigma../sub g//sup +/-B/sup 3/Pi/sub 0//sup +//sub u/ system of the I/sub 2/ molecule, three of which give rise to lasing. The principal pumping was by the 5782 A line. Lasing was obtained on 14 vibrational transitions of the B/sup 3/Pi/sub 0//sup +//sub u/X/sup 1/..sigma../sub g//sup +/ system in the region 1.016--1.342 ..mu..m region. The average generation power in the multifrequency regime was 7 mW at an optical-energy conversion efficiency 4%. It was observed that a noticeable competition takes place between the pump channels of the 5106 and 5782 A lines, and leads to a decrease in the total lasing power. Prospects are discussed of using gas lasers on electronic transitions of molecules optically pumped by metal-vapor vapors, particularly for the development of frequency-tunable optical systems with intensity amplifiers.

  15. Chemical models for simulating single-walled nanotube production in arc vaporization and laser ablation processes

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.

    2004-01-01

    Chemical kinetic models for the nucleation and growth of clusters and single-walled carbon nanotube (SWNT) growth are developed for numerical simulations of the production of SWNTs. Two models that involve evaporation and condensation of carbon and metal catalysts, a full model involving all carbon clusters up to C80, and a reduced model are discussed. The full model is based on a fullerene model, but nickel and carbon/nickel cluster reactions are added to form SWNTs from soot and fullerenes. The full model has a large number of species--so large that to incorporate them into a flow field computation for simulating laser ablation and arc processes requires that they be simplified. The model is reduced by defining large clusters that represent many various sized clusters. Comparisons are given between these models for cases that may be applicable to arc and laser ablation production. Solutions to the system of chemical rate equations of these models for a ramped temperature profile show that production of various species, including SWNTs, agree to within about 50% for a fast ramp, and within 10% for a slower temperature decay time.

  16. A quantum cascade laser-based water vapor isotope analyzer for environmental monitoring.

    PubMed

    Wang, W E; Michel, A P M; Wang, L; Tsai, T; Baeck, M L; Smith, J A; Wysocki, G

    2014-09-01

    A field-deployable mid-infrared quantum cascade laser-based spectrometer was designed and developed for measurements of H2(16)O and H2(18)O at 7.12 μm. H2(16)O and H2(18)O absorption features at 1390.52 cm(-1) and 1389.91 cm(-1), respectively, accessible within current tuning range of the laser, were targeted. The target lines were carefully selected to assure similar absorption levels and similar temperature sensitivities of the line strength due to comparable lower state energies. A real-time spectral fitting algorithm was implemented for isotopic concentration retrieval. Detection limits for H2(16)O and H2(18)O of 2.2 ppm and 7.0 ppb, respectively, were achieved at a dew point of 14 °C (volume mixing ratio of 15,766 ppm) in 1 s integration time, which resulted in a δ(18)O isotopic ratio measurement precision of 0.25‰. The ultimate minimum detection limits obtained after 160 s integration time for H2(16)O and H2(18)O, and δ(18)O measurements were 0.6 ppm, 1.7 ppb, and 0.05‰, respectively. PMID:25273703

  17. A quantum cascade laser-based water vapor isotope analyzer for environmental monitoring

    SciTech Connect

    Wang, W. E.; Tsai, T.; Wysocki, G.; Michel, A. P. M.; Wang, L.; Baeck, M. L.; Smith, J. A.

    2014-09-15

    A field-deployable mid-infrared quantum cascade laser-based spectrometer was designed and developed for measurements of H{sub 2}{sup 16}O and H{sub 2}{sup 18}O at 7.12 μm. H{sub 2}{sup 16}O and H{sub 2}{sup 18}O absorption features at 1390.52 cm{sup −1} and 1389.91 cm{sup −1}, respectively, accessible within current tuning range of the laser, were targeted. The target lines were carefully selected to assure similar absorption levels and similar temperature sensitivities of the line strength due to comparable lower state energies. A real-time spectral fitting algorithm was implemented for isotopic concentration retrieval. Detection limits for H{sub 2}{sup 16}O and H{sub 2}{sup 18}O of 2.2 ppm and 7.0 ppb, respectively, were achieved at a dew point of 14 °C (volume mixing ratio of 15 766 ppm) in 1 s integration time, which resulted in a δ{sup 18}O isotopic ratio measurement precision of 0.25‰. The ultimate minimum detection limits obtained after 160 s integration time for H{sub 2}{sup 16}O and H{sub 2}{sup 18}O, and δ{sup 18}O measurements were 0.6 ppm, 1.7 ppb, and 0.05‰, respectively.

  18. Heat Transfer And Vapor Dynamics Induced By Nanosecond Laser Ablation Of Titanium Target

    SciTech Connect

    Hamadi, F.; Amara, E. H.; Mezaoui, D.

    2008-09-23

    A numerical modelling describing a pulsed nanosecond laser interaction with a titanium target is presented, resulting in the study of the plume expansion in vacuum or in background gas, using the species transport model available in Fluent computational fluid dynamics code. The heat transfers in the solid target and the molten material are modeled using an enthalpy formulation for the solid-liquid phase changing. The effect of laser fluences is investigated, and results are presented as a function of time. Moreover, the plasma or the vapour dynamics is calculated by solving a set of Navier-Stokes equations. The plasma absorption by inverse Bremsstrahlung, the ionization states and the density profiles of the Titanium ions and electrons in the plume are interactively included in the Fluent calculation process by the mean of User Defined Functions (UDFs) used in order to take into account the specificity of our problem. The ionization is computed by solving the Saha-Eggert equation assuming local thermodynamic equilibrium (LTE) conditions.

  19. Growth dynamics of carbon-metal particles and nanotubes synthesized by CO2 laser vaporization

    NASA Astrophysics Data System (ADS)

    Kokai, F.; Takahashi, K.; Yudasaka, M.; Iijima, S.

    To study the growth of carbon-Co/Ni particles and single-wall carbon nanotubes (SWNTs) by 20 ms CO2 laser-pulse irradiation of a graphite-Co/Ni (1.2 at.%) target in an Ar gas atmosphere (600 Torr), we used emission imaging spectroscopy and shadowgraphy with a temporal resolution of 1.67 ms. Wavelength-selected emission images showed that C2 emission was strong in the region close to the target (within 2 cm), while for the same region the blackbody radiation from the large clusters or particles increased with increasing distance from the target. Shadowgraph images showed that the viscous flow of carbon and metal species formed a mushroom or a turbulent cloud spreading slowly into the Ar atmosphere, indicating that particles and SWNTs continued to grow as the ejected material cooled. In addition, emission imaging spectroscopy at 1200 °C showed that C2 and hot clusters and particles with higher emission intensities were distributed over much wider areas. We discuss the growth dynamics of the particles and SWNTs through the interaction of the ambient Ar with the carbon and metal species released from the target by the laser pulse.

  20. 975nm high-peak power ns-diode laser based MOPA system suitable for water vapor DIAL applications

    NASA Astrophysics Data System (ADS)

    Sumpf, Bernd; Klehr, Andreas; Vu, Thi Nghiem; Erbert, Götz; Tränkle, Günther

    2015-03-01

    Micro-DIAL (differential absorption LIDAR) systems require light sources with peak powers in the range of several 10 W together with a spectral line width smaller than the width of absorption lines under study. For water vapor at atmospheric pressure this width should be smaller than 10 pm at 975 nm. In this paper, an all semiconductor master oscillator power amplifier system at an emission wavelength of 975 nm will be presented. This spectral range was selected with respect to a targeted absorption path length of 5000 m and H2O line strengths. A distributed feedback (DFB) ridge waveguide diode laser operated in continuous wave is used as master oscillator whereas a tapered amplifier consisting of a RW section and a flared section is implemented as power amplifier. The RW section acts as optical gate. The current pulses injected into the RW part have a length of 8 ns and the tapered part is driven with 15 ns long pulses. The delay between the pulses is adjusted for optimal pulse shape. The repetition rate is in both cases 25 kHz. A maximal pulse output power of about 16 W limited by the available current supply is achieved. The spectral line width of the system determined by the properties of the DFB laser is smaller than 10 pm. The tuning range amounts 0.9 nm and a SMSR of 40 dB is observed. From the dependence of the peak power on the power injected into the tapered amplifier, the saturation power is determined to 5.3 mW.

  1. Comparison of Photoselective Vaporization versus Holmium Laser Enucleation for Treatment of Benign Prostate Hyperplasia in a Small Prostate Volume

    PubMed Central

    Kim, Kang Sup; Choi, Jin Bong; Bae, Woong Jin; Kim, Su Jin; Cho, Hyuk Jin; Hong, Sung-Hoo; Lee, Ji Youl; Kim, Sang Hoon; Kim, Hyun Woo; Cho, Su Yeon; Kim, Sae Woong

    2016-01-01

    Objective Photoselective vaporization of the prostate (PVP) using GreenLight and Holmium laser enucleation of the prostate (HoLEP) is an important surgical technique for management of benign prostate hyperplasia (BPH). We aimed to compare the effectiveness and safety of PVP using a 120 W GreenLight laser with HoLEP in a small prostate volume. Methods Patients who underwent PVP or HoLEP surgery for BPH at our institutions were reviewed from May 2009 to December 2014 in this retrospective study. Among them, patients with prostate volumes < 40 mL based on preoperative trans-rectal ultrasonography were included in this study. Peri-operative and post-operative parameters—such as International Prostate Symptom Score (IPSS), quality of life (QoL), maximum urinary flow rate (Qmax), post-void residual urine volume (PVR), and complications—were compared between the groups. Results PVP was performed in 176 patients and HoLEP in162 patients. Preoperative demographic data were similar in both groups, with the exception of PVR. Operative time and catheter duration did not show significant difference. Significant improvements compared to preoperative values were verified at the postoperative evaluation in both groups in terms of IPSS, QoL, Qmax, and PVR. Comparison of the postoperative parameters between the PVP and HoLEP groups demonstrated no significant difference, with the exception of IPSS voiding subscore at 1 month postoperatively (5.9 vs. 3.8, P< 0.001). There was no significant difference in postoperative complications between the two groups. Conclusion Our data suggest that PVP and HoLEP are efficient and safe surgical treatment options for patients with small prostate volume. PMID:27227564

  2. Hydrogen isotope correction for laser instrument measurement bias at low water vapor concentration using conventional isotope analyses: application to measurements from Mauna Loa Observatory, Hawaii.

    PubMed

    Johnson, L R; Sharp, Z D; Galewsky, J; Strong, M; Van Pelt, A D; Dong, F; Noone, D

    2011-03-15

    The hydrogen and oxygen isotope ratios of water vapor can be measured with commercially available laser spectroscopy analyzers in real time. Operation of the laser systems in relatively dry air is difficult because measurements are non-linear as a function of humidity at low water concentrations. Here we use field-based sampling coupled with traditional mass spectrometry techniques for assessing linearity and calibrating laser spectroscopy systems at low water vapor concentrations. Air samples are collected in an evacuated 2 L glass flask and the water is separated from the non-condensable gases cryogenically. Approximately 2 µL of water are reduced to H(2) gas and measured on an isotope ratio mass spectrometer. In a field experiment at the Mauna Loa Observatory (MLO), we ran Picarro and Los Gatos Research (LGR) laser analyzers for a period of 25 days in addition to periodic sample collection in evacuated flasks. When the two laser systems are corrected to the flask data, they are strongly coincident over the entire 25 days. The δ(2)H values were found to change by over 200‰ over 2.5 min as the boundary layer elevation changed relative to MLO. The δ(2)H values ranged from -106 to -332‰, and the δ(18)O values (uncorrected) ranged from -12 to -50‰. Raw data from laser analyzers in environments with low water vapor concentrations can be normalized to the international V-SMOW scale by calibration to the flask data measured conventionally. Bias correction is especially critical for the accurate determination of deuterium excess in dry air. PMID:21290447

  3. Answer to Critical Remarks or one More Time About the Mechanism of Limitation on the Energy Characteristics of a Copper Vapor Laser

    NASA Astrophysics Data System (ADS)

    Yudin, N. A.

    2014-05-01

    This work presents an additional analysis of the main positions of the publication by N. A. Yudin, M. R. Tret'yakova, and N. N. Yudin, "Influence of electrophysical processes in the discharge circuit on the energy characteristics of a copper vapor laser" (Russ. Phys. J., 55, No. 9, 1080 - 1090 (2013)) in response to the conclusion drawn in the work of P. A. Bokhan "On the question of the existence of high-frequency oscillations in the power supply circuits of a copper vapor laser and their influence on the lasing mechanism" (Russ. Phys. J., 57, No. 1, 124 - 127 (2014)) that the main positions of the given publication are in error. The analysis performed here confirms the validity of the main positions of publication [2].

  4. Continuous-wave operation of AlGaInP/GaInP quantum-well lasers grown by metalorganic chemical vapor deposition using tertiarybutylphosphine

    NASA Astrophysics Data System (ADS)

    Dong, Jian-Rong; Teng, Jing-Hua; Chua, Soo-Jin; Foo, Boon-Chin; Wang, Yan-Jun; Zhang, Lian-Wen; Yuan, Hai-Rong; Yuan, Shu

    2004-05-01

    Strained AlGaInP/GaInP multiple-quantum-well laser structures have been grown by metalorganic chemical vapor deposition using teriarybutylphosphine as the phosphorus precursor and ridge waveguide lasers of 4 μm wide have been fabricated. Room temperature continuous-wave lasing has been obtained with an emission wavelength of about 670 nm. A single-facet output power of more than 18 mW has been achieved for an as-cleaved laser chip. It can be concluded that it is feasible to fabricate AlGaInP red lasers using less toxic metalorganic source tertiarybutylphosphine in parallel with conventionally used highly toxic PH3.

  5. Room-temperature continuous operation of GaAs/AlGaS lasers grown on Si by organometallic vapor-phase epitaxy

    SciTech Connect

    Choi, H.K.; Wang, C.A.; Fan, J.C.

    1990-08-15

    Graded-index separate-confinement heterostructure single-quantum-well GaAs/AlGaAs diode lasers exhibiting continuous (cw) operation at room temperature have been grown on a Si substrate by organometallic vapor-phase epitaxy, without the use of molecular-beam epitaxy. To improve the quality of the laser structure, a defect-filtering layer was incorporated between this structure and a GaAs buffer layer about 1.5 micron thick grown on the substrate. Of four types of defect-filtering layers investigated, the most effective was one grown with thermal cycling, which made it possible to obtain pulsed threshold current densities as low as 350 A/cm2 for broad-stripe lasers with a cavity length of 500 microns. Ridge-waveguide lasers with this type of defect-filtering layer have exhibited cw threshold currents as low as 25 mA and a differential quantum efficiency of 55%.

  6. Simultaneous imaging of fuel vapor mass fraction and gas-phase temperature inside gasoline sprays using two-line excitation tracer planar laser-induced fluorescence.

    PubMed

    Zigan, Lars; Trost, Johannes; Leipertz, Alfred

    2016-02-20

    This paper reports for the first time, to the best of our knowledge, on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine-relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the nonfluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for two-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF signals. The measurements are conducted in a high-temperature, high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the existing database. A detailed error analysis for both calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations. PMID:26906600

  7. Laser-induced chemical vapor deposition of SiO2

    NASA Astrophysics Data System (ADS)

    Boyer, P. K.; Roche, G. A.; Ritchie, W. H.; Collins, G. J.

    1982-04-01

    We have demonstrated rapid (3000 Å/min) photochemical deposition of silicon dioxide from gas phase donor molecules. An ArF (193 nm) laser was used to excite and dissociate gas phase SiH4 and N2O molecules in contrast to earlier work with incoherent mercury lamps. We have achieved 20 times the deposition rate, limited the dissociation volume to a localized region, and minimized the direct impingement of UV photons on the substrate. Although the SiO2 deposition rate was insensitive to substrate temperature from 20 to 600 °C, film quality noticeably improved above 200 °C. Metal-oxide-semiconductor capacitors were fabricated and characterized in order to measure SiO2 electrical properties. Film composition was investigated using Auger and infrared spectroscopy techniques and showed that the SiO2 is stoichiometric and contains less than 5% nitrogen.

  8. Forced convection and transport effects during hyperbaric laser chemical vapor deposition

    SciTech Connect

    Maxwell, James L; Chavez, Craig A; Espinoza, Miguel; Black, Marcie; Maskaly, Karlene; Boman, Mats

    2009-01-01

    This work explores mass transport processes during HP-LCYD, including the transverse forced-flow of precursor gases through a nozzle to enhance fiber growth rates. The use of laser trapping and suspension of nano-scale particles in the precursor flow is also described, providing insights into the nature of the gas flow, including jetting from the fiber tip and thermodiffusion processes near the reaction zone. The effects of differing molecular-weight buffer gases is also explored in conjunction with the Soret effect, and it is found that nucleation at the deposit surface (and homogeneous nucleation in the gas phase) can be enhanced/ retarded, depending on the buffer gas molecular weight. To demonstrate that extensive microstructures can be grown simultaneously, three-dimensional fiber arrays are also grown in-parallel using diffractive optics--without delatory effects from neighboring reaction sites.

  9. On the Question of the Existence of High-Frequency Oscillations in the Power Supply Circuits of a Copper Vapor Laser and Their Influence on the Lasing Mechanism

    NASA Astrophysics Data System (ADS)

    Bokhan, P. A.

    2014-05-01

    The statement of the problem and conclusions in the publication by N. A. Yudin, M. R. Tret'yakova, and N. N. Yudin "Influence of electrophysical processes in the discharge circuit on the energy characteristics of a copper vapor laser" (Russ. Phys. J., 55, No. 9, 1080 - 1090 (2013)) is considered. It is shown that the main positions of the publication touching on relaxation of the populations of metastable states in the afterglow and their influence on the frequency-energy characteristics of lasers are mistaken.

  10. Investigation of vaporization and condensation processes of thin layers of CdHgTe from laser erosion plasma in Hg atmosphere

    NASA Astrophysics Data System (ADS)

    Kotlyarchuk, B. K.; Popovych, D. I.; Savchuk, V. K.; Savitsky, V. G.

    1996-04-01

    The article sets out to investigate spatial-time and spectral characteristics of laser erosive vapour-plasma torch (EVT), formed at the time of vaporization of mercury chalcogenides targets. Its influence on the synthesis processes and electrophysical properties of HgTe and CdHgTe layers, condensed in mercury vapour, is described. It is shown, that the laser radiation flux density and Hg vapour pressure in the reaction chamber are dominating factors, which determine the character of gas-dynamic spread, EVT composition and electrophysical characteristics of condensed mercury chalcogenides layers.

  11. Laser induced fluorescence monitoring of the transport of small organic molecules in an organic vapor phase deposition system

    NASA Astrophysics Data System (ADS)

    Rolin, Cedric; Vartanian, Garen; Forrest, Stephen R.

    2012-12-01

    Laser-induced fluorescence is employed for the accurate and real-time in-situ monitoring of the concentration of organic molecules in an organic vapor phase deposition (OVPD) chamber. We investigate the transport dynamics of organic species in a hot N2 carrier gas from the evaporation source to the substrate. Based on the time-dependent concentration of organic molecules obtained from their fluorescence intensity near the substrate, we find that carrier gas transport is accurately described by Poiseuille flow. The interplay between convective and diffusive forces gives rise to dispersion of organic molecules in the carrier gas, resulting in the development of plug flow as described by Taylor-Aris theory. Retention of molecules in chamber dead volumes delays transport and introduces tailing of the concentration transients. Our study indicates how OVPD system design and operating conditions can be optimized to limit the duration of transport transients, ultimately leading to precise control over the growth of complex multilayer thin film structures.

  12. Detection of carbon-fluorine bonds in organofluorine compounds by Raman spectroscopy using a copper-vapor laser

    NASA Astrophysics Data System (ADS)

    Sharts, Clay M.; Gorelik, Vladimir S.; Agoltsov, A. M.; Zlobina, Ludmila I.; Sharts, Olga N.

    1999-02-01

    The Raman spectra of fluoro-organic compounds show specific emission bands for carbon-fluorine bonds in the range 500- 800 wave numbers (cm-1)). With very limited exceptions, biological materials do not contain carbon- fluorine bonds. Fluoro-organic compounds introduced into biological samples can be detected by a Raman emission signal. Normal mode C-F bond bands are observed: (1) at 710- 785 cm -1 for trifluoromethyl groups; (2) at 530-610 cm -1 for aromatic organofluorine bonds; (3) a range centered at 690 cm -1 for difluoromethylene groups. Specific examples of normal mode C-F bond emissions for organofluorine compounds containing trifluoromethyl groups are: 1-bromoperfluorooctane, 726 cm -1; perfluorodecanoic acid, 730 cm -1; triperfluoropropylamine, 750 cm -1; 1,3,5-tris- (trifluoromethyl)-benzene, 730 cm -1; Fluoxetine (Prozac) commercial powdered pill at 782 cm -1. Compounds containing aromatic C-F bonds are: hexafluorobenzene, 569 cm MIN1; pentafluoropyridine, 589 cm -1. Difluoromethylene groups: perfluorodecalin, 692 cm-1; perfluorocyclohexane, 691 cm -1. Raman spectra were observed with a standard single monochromator. The 510.8 nm light source was a copper-vapor laser operated at 3-10 watts with 10-12 nanosecond pulses at 10 kHz repetition rate. Detection was made with a time-gated photomultiplier tube. Resonance Raman spectra were also observed at 255.4 nm, using a frequency doubling crystal. Observed spectra were free of fluorescence with very sharp strong C-F lines.

  13. High Temperature Nanocomposites For Nuclear Thermal Propulsion and In-Space Fabrication by Hyperbaric Pressure Laser Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Maxwell, J. L.; Webb, N. D.; Espinoza, M.; Cook, S.; Houts, M.; Kim, T.

    Nuclear Thermal Propulsion (NTP) is an indispensable technology for the manned exploration of the solar system. By using Hyperbaric Pressure Laser Chemical Vapor Deposition (HP-LCVD), the authors propose to design and build a promising next-generation fuel element composed of uranium carbide UC embedded in a latticed matrix of highly refractory Ta4HfC5 for an NTP rocket capable of sustaining temperatures up to 4000 K, enabling an Isp of up to 1250 s. Furthermore, HP-LCVD technology can also be harnessed to enable 3D rapid prototyping of a variety of materials including metals, ceramics and composites, opening up the possibility of in-space fabrication of components, replacement parts, difficult-to-launch solar sails and panels and a variety of other space structures. Additionally, rapid prototyping with HP-LCVD makes a feasible "live off the land" strategy of interplanetary and interstellar exploration ­ the precursors commonly used in the technology are found, often in abundance, on other solar system bodies either as readily harvestable gas (e.g. methane) or as a raw material that could be converted into a suitable precursor (e.g. iron oxide into ferrocene on Mars).

  14. Laser-induced fluorescence measurements and kinetic analysis of Si atom formation in a rotating disk chemical vapor deposition reactor

    SciTech Connect

    Ho, P.; Coltrin, M.E.; Breiland, W.G. )

    1994-10-06

    An extensive set of laser-induced fluorescence (LIF) measurements of Si atoms during the chemical vapor deposition (CVD) of silicon from silane and disilane in a research rotating disk reactor are presented. The experimental results are compared in detail with predictions from a numerical model of CVD from silane and disilane that treats the fluid flow coupled to gas-phase and gas-surface chemistry. The comparisons showed that the unimolecular decomposition of SiH[sub 2] could not account for the observed gas-phase Si atom density profiles. The H[sub 3]SiSiH [leftrightarrow] Si + SiH[sub 4] and H[sub 3]SiSiH + SiH[sub 2] [leftrightarrow] Si + Si[sub 2]H[sub 6] reactions are proposed as the primary Si atom production routes. The model is in good agreement with the measured shapes of the Si atom profiles and the trends in Si atom density with susceptor temperature, pressure, and reactant gas mixture. 33 refs., 12 figs., 3 tabs.

  15. Improvement of the antifungal activity of Litsea cubeba vapor by using a helium-neon (He-Ne) laser against Aspergillus flavus on brown rice snack bars.

    PubMed

    Suhem, Kitiya; Matan, Narumol; Matan, Nirundorn; Danworaphong, Sorasak; Aewsiri, Tanong

    2015-12-23

    The aim of this study was to improve the antifungal activity of the volatile Litsea cubeba essential oil and its main components (citral and limonene) on brown rice snack bars by applying He-Ne laser treatment. Different volumes (50-200 μL) of L. cubeba, citral or limonene were absorbed into a filter paper and placed inside an oven (18 L). Ten brown rice snack bars (2 cm wide × 4 cm long × 0.5 cm deep) were put in an oven and heated at 180 °C for 20 min. The shelf-life of the treated snack bars at 30 °C was assessed and sensory testing was carried out to investigate their consumer acceptability. A count of total phenolic content (TPC) and Fourier transform infrared spectroscopy (FTIR) on the properties of essential oil, citral, and limonene before and after the laser treatment was studied for possible modes of action. It was found that the laser treatment improved the antifungal activity of the examined volatile L. cubeba and citral with Aspergillus flavus inhibition by 80% in comparison with those of the control not treated with the laser. L. cubeba vapor at 100 μL with the laser treatment was found to completely inhibit the growth of natural molds on the snack bars for at least 25 days; however, without essential oil vapor and laser treatment, naturally contaminating mold was observed in 3 days. Results from the sensory tests showed that the panelists were unable to detect flavor and aroma differences between essential oil treatment and the control. Laser treatment caused an increase in TPC of citral oil whereas the TPC in limonene showed a decrease after the laser treatment. These situations could result from the changing peak of the aliphatic hydrocarbons that was revealed by the FTIR spectra. PMID:26433461

  16. Fiber-optic-based laser vapor screen flow visualization system for aerodynamic research in larger scale subsonic and transonic wind tunnels

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.; Inenaga, Andrew S.

    1994-01-01

    Laser vapor screen (LVS) flow visualization systems that are fiber-optic based were developed and installed for aerodynamic research in the Langley 8-Foot Transonic Pressure Tunnel and the Langley 7- by 10-Foot High Speed Tunnel. Fiber optics are used to deliver the laser beam through the plenum shell that surrounds the test section of each facility and to the light-sheet-generating optics positioned in the ceiling window of the test section. Water is injected into the wind tunnel diffuser section to increase the relative humidity and promote condensation of the water vapor in the flow field about the model. The condensed water vapor is then illuminated with an intense sheet of laser light to reveal features of the flow field. The plenum shells are optically sealed; therefore, video-based systems are used to observe and document the flow field. Operational experience shows that the fiber-optic-based systems provide safe, reliable, and high-quality off-surface flow visualization in smaller and larger scale subsonic and transonic wind tunnels. The design, the installation, and the application of the Langley Research Center (LaRC) LVS flow visualization systems in larger scale wind tunnels are highlighted. The efficiency of the fiber optic LVS systems and their insensitivity to wind tunnel vibration, the tunnel operating temperature and pressure variations, and the airborne contaminants are discussed.

  17. Optically pumped metal vapor lasers. Final technical report, 15 Apr 1978-15 Jul 1980

    SciTech Connect

    Mandl, A.; Hyman, H.

    1980-09-01

    The properties of optically-excited Hg/NH/sub 3/ and Hg/ND/sub 3/ mixtures have been studied as a function of mercury pressure in the range 1 to 40 torr. At low mercury pressures, less than or equal to 1 torr, the well-known uv emission band due to HgNH/sub 3/* is dominant; this regime has been investigated extensively over the past ten years. However, at higher pressures the uv band disappears and is replaced by a strong green emission band, centered near 500 nm. From a detailed study of the spectral and temporal characteristics of the green band, it is concluded that it arises from the formation of the Hg/sub 2/NH/sub 3/* (or Hg/sub 2/ND/sub 3/*) excited molecular complex. The lifetime of this exciplex has been measured and is found to be 3.8 ..mu..sec (+- 25%). Because of interest in the system as a potential energy storage laser medium, optical transmission measurements have been carried out at selected wavelengths. Net absorption has been observed across the green band at high mercury density, as well as in the uv band in the low density regime.

  18. Apparatus enables accurate determination of alkali oxides in alkali metals

    NASA Technical Reports Server (NTRS)

    Dupraw, W. A.; Gahn, R. F.; Graab, J. W.; Maple, W. E.; Rosenblum, L.

    1966-01-01

    Evacuated apparatus determines the alkali oxide content of an alkali metal by separating the metal from the oxide by amalgamation with mercury. The apparatus prevents oxygen and moisture from inadvertently entering the system during the sampling and analytical procedure.

  19. Raman-Ramsey multizone spectroscopy in a pure rubidium vapor cell

    SciTech Connect

    Failache, H.; Lenci, L.; Lezama, A.

    2010-02-15

    In view of application to a miniaturized spectroscopy system, we consider an optical setup that splits a laser beam into several parallel narrow light sheets allowing an effective beam expansion and consequently longer atom-light interaction times. We analyze the multizone coherent population trapping (MZCPT) spectroscopy of alkali-metal-vapor atoms, without buffer gas, in the presence of a split light beam. We show that the MZCPT signal is largely insensitive to intensity broadening. Experimentally observed spectra are in qualitative agreement with the predictions of a simplified model that describes each spectrum as an integral over the atomic velocity distribution of Ramsey multizone spectra.

  20. Alkalis and Skin.

    PubMed

    Greenwood, John E; Tan, Jin Lin; Ming, Justin Choong Tzen; Abell, Andrew D

    2016-01-01

    The aim of this editorial is to provide an overview of the chemical interactions occurring in the skin of our patients on contact with alkaline agents. Strongly basic alkali is highly aggressive and will readily hydrolyze (or cleave) key biological molecules such as lipids and proteins. This phenomenon is known as saponification in the case of lipids and liquefactive denaturation for peptides and proteins. A short section on current first-aid concepts is included. A better understanding of the basic science behind alkali burns will make us better teachers and provide an insight into the urgency needed in treating these common and dangerous chemical injuries. PMID:26182072

  1. Alkali metal ion battery with bimetallic electrode

    SciTech Connect

    Boysen, Dane A; Bradwell, David J; Jiang, Kai; Kim, Hojong; Ortiz, Luis A; Sadoway, Donald R; Tomaszowska, Alina A; Wei, Weifeng; Wang, Kangli

    2015-04-07

    Electrochemical cells having molten electrodes having an alkali metal provide receipt and delivery of power by transporting atoms of the alkali metal between electrode environments of disparate chemical potentials through an electrochemical pathway comprising a salt of the alkali metal. The chemical potential of the alkali metal is decreased when combined with one or more non-alkali metals, thus producing a voltage between an electrode comprising the molten the alkali metal and the electrode comprising the combined alkali/non-alkali metals.

  2. Methods of recovering alkali metals

    DOEpatents

    Krumhansl, James L; Rigali, Mark J

    2014-03-04

    Approaches for alkali metal extraction, sequestration and recovery are described. For example, a method of recovering alkali metals includes providing a CST or CST-like (e.g., small pore zeolite) material. The alkali metal species is scavenged from the liquid mixture by the CST or CST-like material. The alkali metal species is extracted from the CST or CST-like material.

  3. Excess-electron and excess-hole states of charged alkali halide clusters

    NASA Astrophysics Data System (ADS)

    Honea, Eric C.; Homer, Margie L.; Whetten, R. L.

    1990-12-01

    Charged alkali halide clusters from a He-cooled laser vaporization source have been used to investigate two distinct cluster states corresponding to the excess-electron and excess-hole states of the crystal. The production method is UV-laser vaporization of an alkali metal rod into a halogen-containing He flow stream, resulting in variable cluster composition and cooling sufficient to stabilize weakly bound forms. Detection of charged clusters is accomplished without subsequent ionization by pulsed-field time-of-flight mass spectrometry of the skimmed cluster beam. Three types of positively charged sodium fluoride cluster are observed, each corresponding to a distinct physical situation: NanF+n-1 (purely ionic form), Nann+1F+n-1 (excess-electron form), and NanF+n (excess-hole form). The purely ionic clusters exhibit an abundance pattern similar to that observed in sputtering and fragmentation experiments and are explained by the stability of completed cubic microlattice structures. The excess-electron clusters, in contrast, exhibit very strong abundance maxima at n = 13 and 22, corresponding to the all-odd series (2n + 1 = jxkxl;j,k,l odd). Their high relative stability is explained by the ease of Na(0) loss except when the excess electron localizes in a lattice site to complete a cuboid structure. These may correspond to the internal F-center state predicted earlier. A localized electron model incorporating structural simulation results as account for the observed pattern. The excess-hole clusters, which had been proposed as intermediates in the ionization-induced fragmentation of neutral AHCs, exhibit a smaller variation in stability, indicating that the hole might not be well localized.

  4. IR and UV laser-induced chemical vapor deposition: Chemical mechanism for a-Si:H and Cr (O,C) film formation

    NASA Astrophysics Data System (ADS)

    Hess, Peter

    The characteristic features of laser-induced chemical vapor deposition in the parallel and perpendicular laser beam/surface configurations are discussed. Low temperature chemical processing with directed and spatially localized energy deposition in the system is investigated. Results obtained for the deposition of hydrogenated amorphous silicon (a-Si:H) films in the parallel configuration employing CO 2 and KrFlasers and SiH 4 and Si 2H 6 as precursors are presented. As a second example, the growth of oxygen- and carbon-containing chromium films Cr(O,C) from chromium hexacarbonyl as the precursor using cw and pulse uv lasers is discussed. The chemical pathways leasing to film formation are investigated in detail.

  5. Optically pumped laser oscillation at about 2.9 microns of a HgCdTe layer grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ravid, A.; Zussman, A.; Cinader, G.; Oron, A.

    1989-12-01

    Photopumped pulsed stimulated emission at 2.9 microns in an HgCdTe layer grown by metalorganic chemical vapor deposition on a CdTe substrate was studied as a function of temperature. The threshold power of the HgCdTe laser (photoexcited by a GaAs diode laser) increased from 0.04 W at 12 K to 1.58 W at 150 K. Above 50 K, the temperature dependence of the threshold is exponential, yielding a T0 of 31 K. From the observed laser emission wavelength a Cd mole fraction of x = 0.422 was determined. The far-field angular full width at e exp -2 of peak intensity was 5.5 and 9.5 deg perpendicular and parallel to the film plane, respectively.

  6. Experiment and simulation study on alkalis transfer characteristic during direct combustion utilization of bagasse.

    PubMed

    Liao, Yanfen; Cao, Yawen; Chen, Tuo; Ma, Xiaoqian

    2015-10-01

    Bagasse is utilized as fuel in the biggest biomass power plant of China, however, alkalis in the fuel created severe agglomeration and slagging problems. Alkalis transfer characteristic, agglomeration causes in engineering practice, additive improvement effects and mechanism during bagasse combustion were investigated via experiments and simulations. Only slight agglomeration occurs in ash higher than 800°C. Serious agglomeration in practical operation should be attributed to the gaseous alkalis evaporating at high temperature and condensing on the cooler grain surfaces in CFB. It can be speculated that ash caking can be avoided with temperature lower than 750°C and heating surface corrosion caused by alkali metal vapor can be alleviated with temperature lower than 850°C. Kaolin added into the bagasse has an apparent advantage over CaO additive both in enhancing ash fusion point and relieving alkali-chloride corrosion by locking alkalis in dystectic solid compounds over the whole temperature range. PMID:26196420

  7. Chlor-Alkali Technology.

    ERIC Educational Resources Information Center

    Venkatesh, S.; Tilak, B. V.

    1983-01-01

    Chlor-alkali technology is one of the largest electrochemical industries in the world, the main products being chlorine and caustic soda (sodium hydroxide) generated simultaneously by the electrolysis of sodium chloride. This technology is reviewed in terms of electrochemical principles and manufacturing processes involved. (Author/JN)

  8. Spin-Exchange Optical Pumping of Solid Alkali Compounds

    NASA Astrophysics Data System (ADS)

    Patton, Brian; Ishikawa, Kiyoshi; Jau, Yuan-Yu; Happer, William

    2007-03-01

    Spin-exchange optical pumping of noble gases has been used for many years to create highly non-equilibrium spin populations, with applications ranging from fundamental physics[1] to medical imaging[2]. In this procedure, angular momentum is transferred from circularly-polarized laser light to the electron spins of an alkali vapor and ultimately to the nuclei of a gas such as ^3He or ^129Xe. Here we show experimentally that a similar process can be used to polarize the nuclei of a solid film of cesium hydride which coats the walls of an optical pumping cell. We present nuclear magnetic resonance (NMR) data which demonstrate that the nuclear polarization of ^133Cs in CsH can be enhanced above the Boltzmann limit in a 9.4-Tesla magnetic field. Possible spin-exchange mechanisms will be discussed, as well as the extension of this technique to other compounds. [1] T. W. Kornack, R. K. Ghosh, and M. V. Romalis, Phys. Rev. Lett. 95, 23080 (2005). [2] M. S. Conradi, D. A. Yablonskiy, et al., Acad. Radiol. 12, 1406 (2005).

  9. Strong Turbulence in Alkali Halide Negative Ion Plasmas

    NASA Astrophysics Data System (ADS)

    Sheehan, Daniel

    1999-11-01

    Negative ion plasmas (NIPs) are charge-neutral plasmas in which the negative charge is dominated by negative ions rather than electrons. They are found in laser discharges, combustion products, semiconductor manufacturing processes, stellar atmospheres, pulsar magnetospheres, and the Earth's ionosphere, both naturally and man-made. They often display signatures of strong turbulence^1. Development of a novel, compact, unmagnetized alkali halide (MX) NIP source will be discussed, it incorporating a ohmically-heated incandescent (2500K) tantulum solenoid (3cm dia, 15 cm long) with heat shields. The solenoid ionizes the MX vapor and confines contaminant electrons, allowing a very dry (electron-free) source. Plasma densities of 10^10 cm-3 and positive to negative ion mass ratios of 1 <= fracm_+m- <= 20 are achievable. The source will allow tests of strong turbulence theory^2. 1 Sheehan, D.P., et al., Phys. Fluids B5, 1593 (1993). 2 Tsytovich, V. and Wharton, C.W., Comm. Plasma Phys. Cont. Fusion 4, 91 (1978).

  10. A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Sargent, M. R.; Sayres, D. S.; Smith, J. B.; Witinski, M.; Allen, N. T.; Demusz, J. N.; Rivero, M.; Tuozzolo, C.; Anderson, J. G.

    2013-07-01

    We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT/LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT/LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons, in

  11. A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere.

    PubMed

    Sargent, M R; Sayres, D S; Smith, J B; Witinski, M; Allen, N T; Demusz, J N; Rivero, M; Tuozzolo, C; Anderson, J G

    2013-07-01

    We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT∕LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT∕LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons

  12. High resolution pore water delta2H and delta18O measurements by H2O(liquid)-H2O(vapor) equilibration laser spectroscopy.

    PubMed

    Wassenaar, L I; Hendry, M J; Chostner, V L; Lis, G P

    2008-12-15

    A new H2O(liquid)-H2O(vapor) pore water equilibration and laser spectroscopy method provides a fast way to obtain accurate high resolution deltaD and delta18O profiles from single core samples from saturated and unsaturated geologic media. The precision and accuracy of the H2O(liquid)-H2O(vapor) equilibration method was comparable to or better than conventional IRMS-based methods, and it can be conducted on geologic cores that contain volumetric water contents as low as 5%. Significant advantages of the H2O(liquid)-H2O(vapor) pore water equilibration method and laser isotopic analysis method include dual hydrogen- and oxygen-isotope assays on single small core samples, low consumable and instrumentation costs, and the potential for field-based hydrogeologic profiling. A single core is sufficient to obtain detailed vertical isotopic depth profiles in geologic, soil, and lacustrine pore water, dramatically reducing the cost of obtaining pore water by conventional wells or physical water extraction methods. In addition, other inherent problems like contamination of wells by leakage and drilling fluids can be eliminated. PMID:19174902

  13. Evaluation of excess In during metal organic vapor-phase epitaxy growth of InGaN by monitoring via in situ laser scattering

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tetsuya; Tamura, Akira; Usami, Shigeyoshi; Mitsunari, Tadashi; Nagamatsu, Kentaro; Nitta, Shugo; Honda, Yoshio; Amano, Hiroshi

    2016-05-01

    Using an in situ laser absorption and scattering method, the surface roughness and incorporation of In in InGaN layers grown by metal organic vapor-phase epitaxy (MOVPE) were monitored. We observed that the laser light with energy higher than the GaN bandgap was fully absorbed in a GaN layer with a smooth film surface. On the other hand, we observed that the scattering laser light from the surface when the roughness of the InGaN surface increased owing to the formation of In droplets. Laser light with energy lower than the GaN bandgap was weakly absorbed by the GaN layer and was scattered at the back surface of the wafer. Furthermore, laser light intensity decreased during InGaN growth because of In incorporation. The threshold of trimethyl-In (TMIn) for the formation of In droplets as a function of growth temperature was determined using our in situ system. Moreover, we observed that the In droplets were removed by thermal or H2 treatment. The results indicate that multiwavelength laser absorption and scattering enable the optimization of the growth conditions for In-rich InGaN.

  14. Optical Properties of Tm(3+) Ions in Alkali Germanate Glass

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Barnes, Norman P.; Reichle, Donald J.; Jiang, Shibin

    2006-01-01

    Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.

  15. Synergistic capture mechanisms for alkali and sulfur species from combustion

    SciTech Connect

    Peterson, T.W.; Shadman, F.; Wendt, J.O.L.; Wu, Baochun.

    1992-01-10

    Due to the generation of a wide variety of pollutants during coal combustion, research on the development of a multifunction sorbent for adsorbing SO{sub 2} and alkali compounds simultaneously is ongoing at the University of Arizona. The current work focuses on the thermodynamic behavior of the reacting system for alkali adsorption especially in gas phase. The temperature and pressure effects on sodium species and on the system are intensively investigated under the simulated flue gas composition condition. The interaction of sulfur dioxide with sodium chloride vapor and some other system elements is also explored.

  16. Hydrothermal alkali metal recovery process

    DOEpatents

    Wolfs, Denise Y.; Clavenna, Le Roy R.; Eakman, James M.; Kalina, Theodore

    1980-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by treating them with a calcium or magnesium-containing compound in the presence of water at a temperature between about 250.degree. F. and about 700.degree. F. and in the presence of an added base to establish a pH during the treatment step that is higher than would otherwise be possible without the addition of the base. During the treating process the relatively high pH facilitates the conversion of water-insoluble alkali metal compounds in the alkali metal residues into water-soluble alkali metal constituents. The resultant aqueous solution containing water-soluble alkali metal constituents is then separated from the residue solids, which consist of the treated particles and any insoluble materials formed during the treatment step, and recycled to the gasification process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. Preferably, the base that is added during the treatment step is an alkali metal hydroxide obtained by water washing the residue solids produced during the treatment step.

  17. High-power Ti:sapphire laser at 820 nm for scanning ground-based water-vapor differential absorption lidar.

    PubMed

    Wagner, Gerd; Behrendt, Andreas; Wulfmeyer, Volker; Späth, Florian; Schiller, Max

    2013-04-10

    The Ti:sapphire (TISA) laser transmitter of the mobile, three-dimensional-scanning water-vapor differential absorption lidar (DIAL) of the University of Hohenheim is described in detail. The dynamically-stable, unidirectional ring resonator contains a single Brewster-cut TISA crystal, which is pumped from both sides with 250 Hz using a diode-pumped frequency-doubled Nd:YAG laser. The resonator is injection seeded and actively frequency-stabilized using a phase-sensitive technique. The TISA laser is operating near 820 nm, which is optimum for ground-based water-vapor DIAL measurements. An average output power of up to 6.75 W with a beam quality factor of M2<2 is reached. The pointing stability is <13 μrad (rms), the depolarization <1%. The overall optical-optical conversion efficiency is up to 19%. The pulse length is 40 ns with a pulse linewidth of <157 MHz. The short- and long-term frequency stabilities are 10 MHz (rms). A spectral purity of 99.9% was determined by pointing to a stratus cloud in low-elevation scanning mode with a cloud bottom height of ≈2.4 km. PMID:23670775

  18. Enhancing vapor generation at a liquid-solid interface using micro/nanoscale surface structures fabricated by femtosecond laser surface processing

    NASA Astrophysics Data System (ADS)

    Anderson, Troy P.; Wilson, Chris; Zuhlke, Craig A.; Kruse, Corey; Gogos, George; Ndao, Sidy; Alexander, Dennis

    2015-03-01

    Femtosecond Laser Surface Processing (FLSP) is a versatile technique for the fabrication of a wide variety of micro/nanostructured surfaces with tailored physical and chemical properties. Through control over processing conditions such as laser fluence, incident pulse count, polarization, and incident angle, the size and density of both micrometer and nanometer-scale surface features can be tailored. Furthermore, the composition and pressure of the environment both during and after laser processing have a substantial impact on the final surface chemistry of the target material. FLSP is therefore a powerful tool for optimizing interfacial phenomena such as wetting, wicking, and phasetransitions associated with a vapor/liquid/solid interface. In the present study, we utilize a series of multiscale FLSPgenerated surfaces to improve the efficiency of vapor generation on a structured surface. Specifically, we demonstrate that FLSP of stainless steel 316 electrode surfaces in an alkaline electrolysis cell results in increased efficiency of the water-splitting reaction used to generate hydrogen. The electrodes are fabricated to be superhydrophilic (the contact angle of a water droplet on the surface is less than 5 degrees). The overpotential of the hydrogen evolution reaction (HER) is measured using a 3-electrode configuration with a structured electrode as the working electrode. The enhancement is attributed to several factors including increased surface area, increased wettability, and the impact of micro/nanostructures on the bubble formation and release. Special emphasis is placed on identifying and isolating the relative impacts of the various contributions.

  19. Novel developments in laser diode Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Claps, Ricardo Javier

    2000-11-01

    This thesis presents the last developments of a laser diode Raman spectrometer for gases, gas flows and vapors, at medium-low pressures. Results are shown for atmospheric gases under STP conditions, and also gas flows from nozzles in subsonic-sonic regimes. The system is unique in that it uses a high power laser diode passively locked by an external grating cavity in Littman/Metcalf configuration, with side-band modes suppressed by 1:10-5, and a reduced bandwidth of <500MHz. The use of Rb vapor cells as notch filters with unprecedented narrow bandwidth (<7 cm-1), allow to collect Stokes and a-Stokes rotational Raman spectra simultaneously. The spectrometer is used to perform studies of thermodynamic equilibrium of gas flows; further studies of samples seeded in the flow (alkali- halides) are discussed, together with potential applications for environmental and industrial monitoring.

  20. Insights in the laser-induced breakdown spectroscopy signal generation underwater using dual pulse excitation — Part I: Vapor bubble, shockwaves and plasma

    NASA Astrophysics Data System (ADS)

    Lazic, V.; Laserna, J. J.; Jovicevic, S.

    2013-04-01

    Plasma and vapor bubble formation and evolution after a nanosecond laser pulse delivered to aluminum targets inside water were studied by fast photography. This technique was also applied to monitor the plasma produced by a second laser pulse and for different interpulse delays. The bubble growth was evident only after 3 μs from the first laser pulse and the bubble shape changed during expansion and collapse cycles. The evolution and propagation of the initial shockwave and its reflections both from the back sample surface and cell walls were detected by Schlieren photography. The primary plasma develops in two phases: violent particle expulsion and ionization during the first μs, followed by slow plasma growth from the ablation crater into the evolving vapor bubble. The shape of the secondary plasma strongly depends on the inner bubble pressure whereas the particle expulsion into the expanded bubble is much less evident. Both the primary and secondary plasma have similar duration of about 30 μs. Detection efficiency of the secondary plasma is much reduced by light refraction at the curved bubble-water interface, which behaves as a negative lens; this leads to an apparent reduction of the plasma dimensions. Defocusing power of the bubble lens increases with its expansion due to the lowering of the vapor's refraction index with respect to that of the surrounding liquid (Lazic et al., 2012 [1]). Smell's reflections of secondary plasma radiation at the expanded bubble wall redistribute the detected intensity on a wavelength-dependent way and allow gathering of the emission also from the external plasma layer that otherwise, would not enter into the optical system.

  1. Developments in alkali-metal atomic magnetometry

    NASA Astrophysics Data System (ADS)

    Seltzer, Scott Jeffrey

    Alkali-metal magnetometers use the coherent precession of polarized atomic spins to detect and measure magnetic fields. Recent advances have enabled magnetometers to become competitive with SQUIDs as the most sensitive magnetic field detectors, and they now find use in a variety of areas ranging from medicine and NMR to explosives detection and fundamental physics research. In this thesis we discuss several developments in alkali-metal atomic magnetometry for both practical and fundamental applications. We present a new method of polarizing the alkali atoms by modulating the optical pumping rate at both the linear and quadratic Zeeman resonance frequencies. We demonstrate experimentally that this method enhances the sensitivity of a potassium magnetometer operating in the Earth's field by a factor of 4, and we calculate that it can reduce the orientation-dependent heading error to less than 0.1 nT. We discuss a radio-frequency magnetometer for detection of oscillating magnetic fields with sensitivity better than 0.2 fT/ Hz , which we apply to the observation of nuclear magnetic resonance (NMR) signals from polarized water, as well as nuclear quadrupole resonance (NQR) signals from ammonium nitrate. We demonstrate that a spin-exchange relaxation-free (SERF) magnetometer can measure all three vector components of the magnetic field in an unshielded environment with comparable sensitivity to other devices. We find that octadecyltrichlorosilane (OTS) acts as an anti-relaxation coating for alkali atoms at temperatures below 170°C, allowing them to collide with a glass surface up to 2,000 times before depolarizing, and we present the first demonstration of high-temperature magnetometry with a coated cell. We also describe a reusable alkali vapor cell intended for the study of interactions between alkali atoms and surface coatings. Finally, we explore the use of a cesium-xenon SERF comagnetometer for a proposed measurement of the permanent electric dipole moments (EDMs

  2. Simple model potential and model wave functions for (H-alkali)+ and (alkali-alkali)+ ions

    NASA Astrophysics Data System (ADS)

    Patil, S. H.; Tang, K. T.

    2000-07-01

    A simple model potential is proposed to describe the interaction of a valence electron with the alkali core, which incorporates the correct asymptotic behavior in terms of dipolar polarizabilities, and the short-range exchange effects in terms of a hard core adjusted to give the correct energy for the valence electron. Based on this potential, simple wave functions are developed to describe the (H-alkali)+ and (alkali-alkali)+ ions. These wave functions exhibit some important structures of the ions, and provide a universal description of the properties of all (H-alkali)+ and (alkali-alkali)+ ions, in particular, the equilibrium separations of the nuclei and the corresponding dissociation energies. They also allow us to calculate the dipolar polarizabilities of Li2+, Na2+, K2+, Rb2+, and Cs2+.

  3. FAR-INFRARED SPECTROSCOPY OF CATIONIC POLYCYCLIC AROMATIC HYDROCARBONS: ZERO KINETIC ENERGY PHOTOELECTRON SPECTROSCOPY OF PENTACENE VAPORIZED FROM LASER DESORPTION

    SciTech Connect

    Zhang Jie; Han Fangyuan; Pei Linsen; Kong Wei; Li Aigen

    2010-05-20

    The distinctive set of infrared (IR) emission bands at 3.3, 6.2, 7.7, 8.6, and 11.3 {mu}m are ubiquitously seen in a wide variety of astrophysical environments. They are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. However, not a single PAH species has yet been identified in space, as the mid-IR vibrational bands are mostly representative of functional groups and thus do not allow one to fingerprint individual PAH molecules. In contrast, the far-IR (FIR) bands are sensitive to the skeletal characteristics of a molecule, hence they are important for chemical identification of unknown species. With an aim to offer laboratory astrophysical data for the Herschel Space Observatory, Stratospheric Observatory for Infrared Astronomy, and similar future space missions, in this work we report neutral and cation FIR spectroscopy of pentacene (C{sub 22}H{sub 14}), a five-ring PAH molecule. We report three IR active modes of cationic pentacene at 53.3, 84.8, and 266 {mu}m that may be detectable by space missions such as the SAFARI instrument on board SPICA. In the experiment, pentacene is vaporized from a laser desorption source and cooled by a supersonic argon beam. We have obtained results from two-color resonantly enhanced multiphoton ionization and two-color zero kinetic energy photoelectron (ZEKE) spectroscopy. Several skeletal vibrational modes of the first electronically excited state of the neutral species and those of the cation are assigned, with the aid of ab initio and density functional calculations. Although ZEKE is governed by the Franck-Condon principle different from direct IR absorption or emission, vibronic coupling in the long ribbon-like molecule results in the observation of a few IR active modes. Within the experimental resolution of {approx}7 cm{sup -1}, the frequency values from our calculation agree with the experiment for the cation, but differ for the electronically excited intermediate state. Consequently, modeling of the

  4. 4.7-W, 255-nm source based on second-harmonic generation of a copper-vapor laser in cesium lithium borate.

    PubMed

    Trickett, R I; Withford, M J; Brown, D J

    1998-02-01

    We have generated 4.7 W of UV (255-nm) radiation with wall plug efficiency of 0.12% by frequency doubling the green (511-nm) output of a kinetically enhanced medium-scale copper-vapor laser (CVL) in cesium lithium borate (CLBO). Frequency doubling in beta -barium borate produced 3.9 W of UV radiation with wall plug efficiency of 0.1%. We found that conversion was better with CLBO because of the reduced constraints on CVL beam quality, less UV absorption, and smaller UV walk-off. PMID:18084455

  5. Fabrication of photonic crystal structures by tertiary-butyl arsine-based metal–organic vapor-phase epitaxy for photonic crystal lasers

    NASA Astrophysics Data System (ADS)

    Yoshida, Masahiro; Kawasaki, Masato; De Zoysa, Menaka; Ishizaki, Kenji; Hatsuda, Ranko; Noda, Susumu

    2016-06-01

    The fabrication of air/semiconductor two-dimensional photonic crystal structures by air-hole-retained crystal regrowth using tertiary-butyl arsine-based metal–organic vapor-phase epitaxy for GaAs-based photonic crystal lasers is investigated. Photonic crystal air holes with filling factors of 10–13%, depths of ∼280 nm, and widths of 120–150 nm are successfully embedded. The embedded air holes exhibit characteristic shapes due to the anisotropy of crystal growth. Furthermore, a low lasing threshold of ∼0.5 kA/cm2 is achieved with the fabricated structures.

  6. High-Jc YBa2Cu3O7-δ superconducting film grown by laser-assisted chemical vapor deposition using a single liquid source and its microstructure

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Ito, Akihiko; Kato, Takeharu; Yokoe, Daisaku; Hirayama, Tsukasa; Goto, Takashi

    2013-09-01

    A YBa2Cu3O7-δ (YBCO) film was prepared on a multilayer-coated Hastelloy C276 substrate by laser-assisted metalorganic chemical vapor deposition using a single liquid source precursor. A c-axis-oriented YBCO film was grown epitaxially on a (100) CeO2 layer at a deposition rate of 11 μm h-1. A screw dislocation and stacking faults were observed in the cross-section of the YBCO film. The critical current density of the YBCO film reached 2.7 MA cm-2.

  7. Preparation of the c-axis oriented AlN film by laser chemical vapor deposition using a newly proposed Al(acac)3 precursor

    NASA Astrophysics Data System (ADS)

    You, Yu; Ito, Akihiko; Tu, Rong; Goto, Takashi

    2013-02-01

    Highly oriented AlN film was prepared on a c-plane sapphire substrate by laser chemical vapor deposition using a newly proposed aluminum acetylacetonate precursor and ammonia gas as source reactants. The c-axis oriented AlN films were obtained on the c-plane sapphire substrate at deposition temperatures from 900 to 1230 K. AlN film prepared at 1047 K showed an epitaxial relation as (//( [//[. The full width at half maximum (FWHM) of the X-ray rocking curve for AlN (0002) plane increased with increasing deposition temperature. The c-axis lattice parameter decreased with increasing deposition temperature.

  8. Heterodyne laser spectroscopy system

    DOEpatents

    Wyeth, Richard W.; Paisner, Jeffrey A.; Story, Thomas

    1990-01-01

    A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency, and provides spectral analysis of a laser beam.

  9. Heterodyne laser spectroscopy system

    DOEpatents

    Wyeth, Richard W.; Paisner, Jeffrey A.; Story, Thomas

    1989-01-01

    A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency and the like, and provides spectral analysis of a laser beam.

  10. Interpretation of Absolute Laser Reflectance During Optical Monitoring of Polycrystalline GaAs Deposition on Quartz Using Metalorganic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Clayton, Andrew J.; Irvine, Stuart J. C.

    2011-06-01

    Gallium arsenide (GaAs) was deposited by metalorganic chemical vapor deposition in a horizontal quartz reactor tube using trimethylgallium and arsine at 400°C to 500°C. Nucleation time and deposition rate were monitored using in situ laser reflectometry. This allowed differentiation between film and parasitic growth, which was not possible with other optical techniques. An absolute reflectance model was developed using measurements prior to GaAs deposition, and then employed to calculate values for GaAs on quartz. Detected reflectance intensities during experimental GaAs deposition were low compared with the model due to three-dimensional island growth, causing scattering of the incident laser radiation.

  11. Laser-Induced Fluorescence Measurements of Translational Temperature and Relative Cycle Number by use of Optically Pumped Trace-Sodium Vapor

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.

    1999-01-01

    Sodium fluorescence induced by a narrow-bandwidth tunable laser has been used to measure temperature, pressure, axial velocity, and species concentrations in wind tunnels, rocket engine exhausts, and the upper atmosphere. Optical pumping of the ground states of the sodium, however, can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating such measurements. Here a straightforward extension of rate equations originally proposed to account for the features of the pumped spectrum is used to make temperature measurements from spectra taken in pumped vapor. Also determined from the spectrum is the relative fluorescence cycle number, which has application to measurement of diffusion rate and transverse flow velocity, The accuracy of both the temperature and the cycle-number measurements is comparable with that of temperature measurements made in the absence of pumping.

  12. Laser-Induced Fluorescence Measurements of Translational Temperature and Relative Cycle Number by use of Optically Pumped Trace-Sodium Vapor

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.

    1998-01-01

    Sodium fluorescence induced by a narrow bandwidth tunable laser has been used to measure temperature, pressure, axial velocity and species concentrations in wind tunnels, rocket engine exhausts and the upper atmosphere. Optical pumping of the ground states of the sodium, however, can radically alter the shape of the laser induced fluorescence excitation spectrum, complicating such measurements. Here a straightforward extension of rate equations originally proposed to account for the features of the pumped spectrum is to make temperature measurements from spectra taken in pumped vapor. Also determined from the spectrum is the relative fluorescence cycle number, which has application to measurement of diffusion rate and transverse flow velocity. The accuracy of both the temperature and cycle-number measurements is comparable with that of temperature measurements made in the absence of pumping.

  13. Laser-induced fluorescence measurements of translational temperature and relative cycle number by use of optically pumped trace-sodium vapor.

    PubMed

    Dobson, C C

    1999-06-20

    Sodium fluorescence induced by a narrow-bandwidth tunable laser has been used to measure temperature, pressure, axial velocity, and species concentrations in wind tunnels, rocket engine exhausts, and the upper atmosphere. Optical pumping of the ground states of the sodium, however, can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating such measurements. Here a straightforward extension of rate equations originally proposed to account for the features of the pumped spectrum is used to make temperature measurements from spectra taken in pumped vapor. Also determined from the spectrum is the relative fluorescence cycle number, which has application to measurement of diffusion rate and transverse flow velocity. The accuracy of both the temperature and the cycle-number measurements is comparable with that of temperature measurements made in the absence of pumping. PMID:18320000

  14. Release and sorption of alkali metals in coal conversion

    SciTech Connect

    Witthohn, A.; Oeltjen, L.; Hilpert, K.

    1998-07-01

    Released as gaseous species during coal combustion and gasification, alkali metal compounds cause high temperature corrosion especially at the gas turbine blading of coal-fired combined cycle power plants. Experimental and theoretical basic investigations are presented, which contribute to the understanding of the release and sorption of these contaminants. Knudsen effusion mass spectrometry was used to study the vaporization of coal ashes and slags at temperatures between 200 and 1,800 C and to determine the released alkali species and their partial pressures. The data base system FACT and the modified quasi-chemical model for non-ideal solutions were applied to model the thermodynamic behavior of coal slags and to determine material compositions of maximum alkali sorption capacity.

  15. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1991-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  16. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1990-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neturons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  17. Environmental site description for a Uranium Atomic Vapor Laser Isotope Separation (U-AVLIS) production plant at the Paducah Gaseous Diffusion Plant site

    SciTech Connect

    Marmer, G.J.; Dunn, C.P.; Moeller, K.L.; Pfingston, J.M.; Policastro, A.J.; Yuen, C.R.; Cleland, J.H.

    1991-09-01

    Uranium enrichment in the United States has utilized a diffusion process to preferentially enrich the U-235 isotope in the uranium product. The U-AVLIS process is based on electrostatic extraction of photoionized U-235 atoms from an atomic vapor stream created by electron-beam vaporization of uranium metal alloy. The U-235 atoms are ionized when precisely tuned laser light -- of appropriate power, spectral, and temporal characteristics -- illuminates the uranium vapor and selectively photoionizes the U-235 isotope. A programmatic document for use in screening DOE site to locate a U-AVLIS production plant was developed and implemented in two parts. The first part consisted of a series of screening analyses, based on exclusionary and other criteria, that identified a reasonable number of candidate sites. These sites were subjected to a more rigorous and detailed comparative analysis for the purpose of developing a short list of reasonable alternative sites for later environmental examination. This environmental site description (ESD) provides a detailed description of the PGDP site and vicinity suitable for use in an environmental impact statement (EIS). The report is based on existing literature, data collected at the site, and information collected by Argonne National Laboratory (ANL) staff during a site visit. 65 refs., 15 tabs.

  18. Nonlinear infrared generation in alkali metal vapors: steady state susceptibilities and dynamic behavior. Effective relaxation rates and preliminary Raman gain predictions for the Cs system. Technical progress report, 1 July-31 December 1986

    SciTech Connect

    Lawandy, N.M.

    1986-12-01

    Effective relaxation rates for atomic cesium pumped by doubled Alexandrite radiation are presented. Laser radiation levels are 8S 1/2 and 9S 1/2; resonance levels 3 = 8P 1/2 and 8P 1/2, respectively. In addition, Raman gain is represented in two graphs which plot chi per atom (10 to the -13 power) at Raman peak versus the infrared wave number per centimeter and the corresponding doubled Alexandrite wave number. One graph covers resonance level 8P, the other 9P; in both cases cesium is pumped with a peak pulse height of 0.5 MW in a 200 micron diameter spot size.

  19. Pulsed hybrid dual wavelength Y-branch-DFB laser-tapered amplifier system suitable for water vapor detection at 965 nm with 16 W peak power

    NASA Astrophysics Data System (ADS)

    Vu, Thi N.; Klehr, Andreas; Sumpf, Bernd; Hoffmann, Thomas; Liero, Armin; Tränkle, Günther

    2016-03-01

    A master oscillator power amplifier system emitting alternatingly at two neighbored wavelengths around 965 nm is presented. As master oscillator (MO) a Y-branch DFB-laser is used. The two branches, which can be individually controlled, deliver the two wavelengths needed for a differential absorption measurement of water vapor. Adjusting the current through the DFB sections, the wavelength can be adjusted with respect to the targeted either "on" or "off" resonance, respectively wavelength λon or wavelength λoff. The emission of this laser is amplified in a tapered amplifier (TA). The ridge waveguide section of the TA acts as optical gate to generate short pulses with duration of 8 ns at a repetition rate of 25 kHz, the flared section is used for further amplification to reach peak powers up to 16 W suitable for micro-LIDAR (Light Detection and Ranging). The necessary pulse current supply user a GaN-transistor based driver electronics placed close to the power amplifier (PA). The spectral properties of the emission of the MO are preserved by the PA. A spectral line width smaller than 10 pm and a side mode suppression ratio (SMSR) of 37 dB are measured. These values meet the demands for water vapor absorption measurements under atmospheric conditions.

  20. Measurement of water vapor line strengths in the 1.4-2.7 μm range by tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Pogány, Andrea; Klein, Alexander; Ebert, Volker

    2015-11-01

    Line strengths of nine water vapor absorption lines in the wavelength range between 1.37 and 2.71 μm with line strengths of 10-23-10-20 cm/molecule have been measured using direct tunable diode laser absorption spectroscopy (dTDLAS). Four different light sources were used: three distributed feedback (DFB) diode lasers with wavelengths of 1.37 μm, 2.55 μm and 2.71 μm for measuring one application-specifically selected absorption line with each laser, and a vertical-cavity surface-emitting laser (VCSEL) radiating around 1.39 μm for the measurement of six further absorption lines. Despite the different light sources and line strengths, a uniform measurement and data evaluation method was developed and applied to all lines, and the experimental set-up was kept as similar as possible. This allows a thorough and uniform uncertainty analysis and evaluation of the contributions of the individual experimental parameters to the uncertainty of the derived line strengths. A comprehensive and transparent uncertainty analysis is given for the measurements. Uncertainties of our measured line strengths are in the 1.1-2.5% range (k=2, 95% confidence level). Our measured line strength values agree well with line strengths in the HITRAN 2012 database and other literature sources, we realized lower uncertainties up to a factor of 5-10.

  1. Water vapor isotopes measurements at Mauna Loa, Hawaii: Comparison of laser spectroscopy and remote sensing with traditional methods, and the need for ongoing monitoring

    NASA Astrophysics Data System (ADS)

    Galewsky, J.; Noone, D.; Sharp, Z.; Worden, J.

    2009-04-01

    The isotopic composition of water vapor (2H/1H and 18O/16 ratios) provides unique information on the transport pathways that link water sources to regional sinks, and thus proves useful in understanding large scale atmospheric humidity budgets. Recent advances in measurement technology allow the monitoring of water vapor isotope composition in ways which has can revolutionize investigations of atmospheric hydrology. Traditional measurement of isotopic composition requires trapping of samples with either large volume vacuum flasks or by trapping liquid samples with cryogens for later analyses using mass spectrometry, and are laborious and seldom span more than just short dedicated observational periods. On the other hand, laser absorption spectroscopy can provide almost continuous and autonomous in situ measurements of isotope abundances with precision almost that of traditional mass spectrometry, and observations from spacecraft can make almost daily maps of the global isotope distributions. In October of 2008 three laser based spectrometers were deployed at the Mauna Loa Laboratory in Hawaii to make continuous measurement of the 2H and 18O abundance of free tropospheric water vapor. These results are compared with traditional measurements and with measurements from two satellite platforms. While providing field validation of the new methodologies, the data show variability which captures the transport processes in the region. The data are used to characterize the role of large scale mixing of dry air, the influence of the boundary layer and the importance of moist convection in controlling the low humidity of subtropical air near Hawaii. Although the record is short, it demonstrates the usefulness of using robust isotope measurements to understand the budgets of the most important greenhouse gas. This work motivates establishing a continuous record of isotopes measurement at baseline sites, like Mauna Loa, such that the changes in water cycle can be understood and

  2. Water vapor isotopes measurements at Mauna Loa, Hawaii: Comparison of laser spectroscopy and remote sensing with traditional methods, and the need for ongoing monitoring

    NASA Astrophysics Data System (ADS)

    Noone, D.; Galewsky, J.; Sharp, Z.; Worden, J.

    2008-12-01

    The isotopic composition of water vapor (2H/1H and 18O/16 ratios) provides unique information on the transport pathways that link the water sources to regional sinks, and thus proves useful in understanding the large scale humidity budgets. Recent advances in measurement technology allow the monitoring of water vapor isotope composition in ways which has can revolutionize investigations of atmospheric hydrology. Traditional measurement of isotopic composition requires trapping of samples with either large volume vacuum flasks or by trapping liquid samples with cryogens for later analyses using mass spectrometry, and are laborious and seldom span more than just short dedicated observational periods. On the other hand, laser absorption spectroscopy can provide almost continuous and autonomous in situ measurements of isotope abundances with precision almost that of traditional mass spectrometry, and observations from spacecraft can make almost daily maps of the global isotope distributions. In October of 2008 three laser based spectrometers were deployed at the Mauna Loa Laboratory in Hawaii to make continuous measurement of the 2H and 18O abundance of free tropospheric water vapor. These results are compared with traditional measurements and with measurements from two satellite platforms. While providing field validation of the new methodologies, the data show variability which captures the transport processes in the region. The data are used to characterize the role of large scale mixing of dry air, the influence of the boundary layer and the importance of moist convection in controlling the low humidity of subtropical air near Hawaii. Although the record is short, it demonstrates the usefulness of using robust isotope measurements to understand the budgets of the most important greenhouse gas. This work motivates establishing a continuous record of isotopes measurement at baseline sites, like Mauna Loa, such that the changes in water cycle can be understood and

  3. Coherent coupling of alkali atoms by random collisions.

    PubMed

    Katz, Or; Peleg, Or; Firstenberg, Ofer

    2015-09-11

    Random spin-exchange collisions in warm alkali vapor cause rapid decoherence and act to equilibrate the spin state of the atoms in the vapor. In contrast, here we demonstrate experimentally and theoretically a coherent coupling of one alkali species to another species, mediated by these random collisions. We show that the minor species (potassium) inherits the magnetic properties of the dominant species (rubidium), including its lifetime (T_{1}), coherence time (T_{2}), gyromagnetic ratio, and spin-exchange relaxation-free magnetic-field threshold. We further show that this coupling can be completely controlled by varying the strength of the magnetic field. Finally, we explain these phenomena analytically by mode mixing of the two species via spin-exchange collisions. PMID:26406827

  4. Adsorption on Alkali Halides.

    NASA Astrophysics Data System (ADS)

    Urzua Duran, Gilberto Antonio

    1995-01-01

    Using a variety of interionic potentials, I have computed the configurations of adsorbed alkali halides monomers on the (001) surface of selected alkali halides crystals. In the majority of cases studied it is found that the monomer adsorbs perpendicular to the surface with the cation sitting nearly on top of the surface anion. In about ten percent of the cases though the monomer adsorbs tilted from the vertical. In these cases the ion that is closer to the surface can be the cation or the anion. The effect of polarization forces is found to be important. In order to discuss the effects of surface retaxation with adsorbates, I have evaluated the surface relaxation of the alkali halide crystals, using a shell model for the interionic forces. It is found that surface relaxation and rumpling are generally small, especially when the van der Waals forces are included. A theory of the effect of substrate vibrations on the binding of an adsorbed atom is developed. At T = 0 the binding energy is D_0-E, where D_0 is the surface well depth (classical binding energy) and E is the quantum correction. For several simple models, it is found that E is surprisingly model-independent. We compare D _0-E with the binding energies to a rigid substrate, D_0-E_{rs}, and to a vibrationally averaged substrate, D _0-E_{va}. We prove that E_{va}>=q E>=q E_ {rs} and that similar relations hold at finite temperature for the free energy of binding. In most cases E_{rs} is better than E_{va} as an approximation to E.

  5. Pulsed laser photolysis and quantum chemical-statistical rate study of the reaction of the ethynyl radical with water vapor.

    PubMed

    Carl, Shaun A; Nguyen, Hue Minh Thi; Elsamra, Rehab M I; Nguyen, Minh Tho; Peeters, Jozef

    2005-03-15

    The rate coefficient of the gas-phase reaction C(2)H + H(2)O-->products has been experimentally determined over the temperature range 500-825 K using a pulsed laser photolysis-chemiluminescence (PLP-CL) technique. Ethynyl radicals (C(2)H) were generated by pulsed 193 nm photolysis of C(2)H(2) in the presence of H(2)O vapor and buffer gas N(2) at 15 Torr. The relative concentration of C(2)H radicals was monitored as a function of time using a CH* chemiluminescence method. The rate constant determinations for C(2)H + H(2)O were k(1)(550 K) = (2.3 +/- 1.3) x 10(-13) cm(3) s(-1), k(1)(770 K) =(7.2 +/- 1.4) x 10(-13) cm(3) s(-1), and k(1)(825 K) = (7.7 +/- 1.5) x 10(-13) cm(3) s(-1). The error in the only other measurement of this rate constant is also discussed. We have also characterized the reaction theoretically using quantum chemical computations. The relevant portion of the potential energy surface of C(2)H(3)O in its doublet electronic ground state has been investigated using density functional theory B3LYP6-311 + + G(3df,2p) and molecular orbital computations at the unrestricted coupled-cluster level of theory that incorporates all single and double excitations plus perturbative corrections for the triple excitations, along with the 6-311 + + G(3df,2p) basis set [(U)CCSD(T)6-311 + + G(3df,2p)] and using UCCSD(T)6-31G(d,p) optimized geometries. Five isomers, six dissociation products, and sixteen transition structures were characterized. The results confirm that the hydrogen abstraction producing C(2)H(2)+OH is the most facile reaction channel. For this channel, refined computations using (U)CCSD(T)6-311 + + G(3df,2p)(U)CCSD(T)6-311 + + G(d,p) and complete-active-space second-order perturbation theory/complete-active-space self-consistent-field theory (CASPT2/CASSCF) [B. O. Roos, Adv. Chem. Phys. 69, 399 (1987)] using the contracted atomic natural orbitals basis set (ANO-L) [J. Almlof and P. R. Taylor, J. Chem. Phys.86, 4070 (1987)] were performed, yielding zero

  6. Use of precalciners to remove alkali from raw materials in the cement industry. Final report, July 1978-July 1980

    SciTech Connect

    Gartner, E.M.

    1980-07-01

    The objective of this work was to develop an efficient means of removing alkali metal compounds (alkalies) from high-alkali aluminosilicate raw materials of the type commonly used as part of cement raw mixes in order to increase the energy efficiency of cement manufacture. The intention of this project was to determine whether the high-alkali raw materials could be pyroprocessed separately to remove the alkalies before they entered the rotary kiln, where they would be mixed with the other raw feed components. If this could be achieved, considerable savings could be made in the energy required to remove alkalies, compared to conventional methods in which the cement raw mix must be treated as a whole. Two different methods of alkali removal were examined, namely, vaporization of alkalies at relatively low temperatures; and alkali-rich melt separation at relativey high temperatures. The results showed that the removal of alkalies by pyroprocessing of high-alkali raw feed components separate from the other cement raw mix components is not likely to be a practical alternative to the best available conventional precalciner technology. (LCL)

  7. Preparation of alkali metal dispersions

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Landel, R. F. (Inventor)

    1968-01-01

    A method is described for producing alkali metal dispersions of high purity. The dispersions are prepared by varying the equilibrium solubility of the alkali metal in a suitable organic solvent in the presence of aromatic hydrocarbons. The equilibrium variation is produced by temperature change. The size of the particles is controlled by controlling the rate of temperature change.

  8. Development of high-performance alkali-hybrid polarized 3He targets for electron scattering

    NASA Astrophysics Data System (ADS)

    Singh, Jaideep T.; Dolph, P. A. M.; Tobias, W. A.; Averett, T. D.; Kelleher, A.; Mooney, K. E.; Nelyubin, V. V.; Wang, Yunxiao; Zheng, Yuan; Cates, G. D.

    2015-05-01

    , the K to Rb alkali vapor density ratio should be about 5 ±2 and the line width of the optical pumping lasers should be no more than 0.3 nm. Our measurements of the X -factors under these conditions seem to indicate the 3He polarization is limited to ≈90 %. The simulation results, now benchmarked against experimental data, are useful for the design of future targets. Further work is required to better understand the temperature dependence of the X -factor spin-relaxation mechanism and the limitations of our optical pumping simulation.

  9. Purification of alkali metal nitrates

    DOEpatents

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

    A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

  10. Push-Pull Laser-Atomic Oscillator

    NASA Astrophysics Data System (ADS)

    Jau, Y.-Y.; Happer, W.

    2007-11-01

    A vapor of alkali-metal atoms in the external cavity of a semiconductor laser, pumped with a time-independent injection current, can cause the laser to self-modulate at the “field-independent 0-0 frequency” of the atoms. Push-pull optical pumping by the modulated light drives most of the atoms into a coherent superposition of the two atomic sublevels with an azimuthal quantum number m=0. The atoms modulate the optical loss of the cavity at the sharply defined 0-0 hyperfine frequency. As in a maser, the system is not driven by an external source of microwaves, but a very stable microwave signal can be recovered from the modulated light or from the modulated voltage drop across the laser diode. Potential applications for this new phenomenon include atomic clocks, the production of long-lived coherent atomic states, and the generation of coherent optical combs.

  11. Push-Pull Laser-Atomic Oscillator

    SciTech Connect

    Jau, Y.-Y.; Happer, W.

    2007-11-30

    A vapor of alkali-metal atoms in the external cavity of a semiconductor laser, pumped with a time-independent injection current, can cause the laser to self-modulate at the 'field-independent 0-0 frequency' of the atoms. Push-pull optical pumping by the modulated light drives most of the atoms into a coherent superposition of the two atomic sublevels with an azimuthal quantum number m=0. The atoms modulate the optical loss of the cavity at the sharply defined 0-0 hyperfine frequency. As in a maser, the system is not driven by an external source of microwaves, but a very stable microwave signal can be recovered from the modulated light or from the modulated voltage drop across the laser diode. Potential applications for this new phenomenon include atomic clocks, the production of long-lived coherent atomic states, and the generation of coherent optical combs.

  12. Initial Experiences with a 980 nm Diode Laser for Photoselective Vaporization of the Prostate for the Treatment of Benign Prostatic Hyperplasia

    PubMed Central

    Yang, Ki Su; Kim, In Gon; Han, Bo Hyun; Kong, Geun Soo

    2011-01-01

    Purpose This study was conducted to analyze the efficacy of photoselective vaporization of the prostate (PVP) with the use of a 980 nm diode laser for benign prostatic hyperplasia (BPH) according to postoperative period. Materials and Methods Data were collected from 96 patients who were diagnosed with BPH and who underwent PVP with the 980 nm K2 diode laser. Postoperative parameters, including International Prostate Symptom Score (IPSS), quality of life (QoL) score, maximum urinary flow rate (Qmax), and post-void residual volume (PVR), were assessed and compared with preoperative baseline values. Results The mean prostate volume was 45.3±15.6 g, the mean operative time (lasing time) was 22.9±18.3 minutes, the total amount of energy was 126±84 kJ, and the Foley catheter maintenance period after PVP was 24.8±5.6 hours. At 1 month, significant improvements were noted in IPSS (11.7±6.6), QoL score (2.3±1.1), Qmax (12.7±6.1 ml/sec), and PVR (41.9±30.5 ml). After 3 months, all follow-up parameters showed significant improvements that were sustained throughout a period of 6 months after PVP. Conclusions PVP using a K2 diode laser is a minimally invasive and effective surgical method for improvement of BPH and is associated with minimal morbidity. PMID:22195264

  13. High-speed assembly language (80386/80387) programming for laser spectra scan control and data acquisition providing improved resolution water vapor spectroscopy

    NASA Technical Reports Server (NTRS)

    Allen, Robert J.

    1988-01-01

    An assembly language program using the Intel 80386 CPU and 80387 math co-processor chips was written to increase the speed of data gathering and processing, and provide control of a scanning CW ring dye laser system. This laser system is used in high resolution (better than 0.001 cm-1) water vapor spectroscopy experiments. Laser beam power is sensed at the input and output of white cells and the output of a Fabry-Perot. The assembly language subroutine is called from Basic, acquires the data and performs various calculations at rates greater than 150 faster than could be performed by the higher level language. The width of output control pulses generated in assembly language are 3 to 4 microsecs as compared to 2 to 3.7 millisecs for those generated in Basic (about 500 to 1000 times faster). Included are a block diagram and brief description of the spectroscopy experiment, a flow diagram of the Basic and assembly language programs, listing of the programs, scope photographs of the computer generated 5-volt pulses used for control and timing analysis, and representative water spectrum curves obtained using these programs.

  14. A two-channel, tunable diode laser-based hygrometer for measurement of water vapor and cirrus cloud ice water content in the upper troposphere and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Thornberry, T. D.; Rollins, A. W.; Gao, R. S.; Watts, L. A.; Ciciora, S. J.; McLaughlin, R. J.; Fahey, D. W.

    2014-08-01

    The recently developed NOAA Water instrument is a two-channel, closed-path, tunable diode laser absorption spectrometer designed for the measurement of water vapor and enhanced total water (vapor + inertially enhanced condensed-phase) in the upper troposphere/lower stratosphere from the NASA Global Hawk unmanned aircraft system (UAS) or other high-altitude research aircraft. The instrument utilizes wavelength-modulated spectroscopy with second harmonic detection near 2694 nm to achieve high precision with a 79 cm double-pass optical path. The detection cells are operated under constant temperature, pressure and flow conditions to maintain a constant sensitivity to H2O independent of the ambient sampling environment. An on-board calibration system is used to perform periodic in situ calibrations to verify the stability of the instrument sensitivity during flight. For the water vapor channel, ambient air is sampled perpendicular to the flow past the aircraft in order to reject cloud particles, while the total water channel uses a heated, forward-facing inlet to sample both water vapor and cloud particles. The total water inlet operates subisokinetically, thereby inertially enhancing cloud particle number in the sample flow and affording increased cloud water content sensitivity. The NOAA Water instrument was flown for the first time during the second deployment of the Airborne Tropical TRopopause EXperiment (ATTREX) in February-March 2013 on board the Global Hawk UAS. The instrument demonstrated a typical in-flight precision (1 s, 1σ) of better than 0.17 parts per million (ppm, 10-6 mol mol-1), with an overall H2O vapor measurement uncertainty of 5% ± 0.23 ppm. The inertial enhancement for cirrus cloud particle sampling under ATTREX flight conditions ranged from 33-48 for ice particles larger than 8 μm in diameter, depending primarily on aircraft altitude. The resulting ice water content detection limit (2σ) was 0.023-0.013 ppm, corresponding to approximately 2

  15. The NOAA Water Instrument: A Two-Channel, Tunable Diode Laser-Based Hygrometer for Measurement of Water Vapor and Cirrus Cloud Ice Water Content

    NASA Astrophysics Data System (ADS)

    Fahey, D. W.; Thornberry, T. D.; Rollins, A. W.; Gao, R. S.; Watts, L. A.; Ciciora, S. J.; McLaughlin, R. J.

    2014-12-01

    The recently developed NOAA Water instrument is a two-channel, closed-path, tunable diode laser absorption spectrometer designed for the measurement of water vapor and enhanced total water (vapor + inertially enhanced condensed-phase) from the NASA Global Hawk unmanned aircraft system (UAS) or other high-altitude research aircraft. Combining the measurements from the two channels allows the determination of cloud ice water content (IWC), an important metric for evaluating the radiative properties of cirrus clouds. The instrument utilizes wavelength-modulated spectroscopy with second harmonic detection near 2694 nm to achieve high precision with a 79 cm double-pass optical path. The detection cells are operated under constant temperature, pressure and flow conditions to maintain a constant sensitivity to H2O independent of the ambient sampling environment. An on-board calibration system is used to perform periodic in situ calibrations to verify the stability of the instrument sensitivity during flight. For the water vapor channel, ambient air is sampled perpendicular to the flow past the aircraft in order to reject cloud particles, while the total water channel uses a heated, forward-facing inlet to sample both water vapor and cloud particles. The total water inlet operates subisokinetically, thereby inertially enhancing cloud particle number in the sample flow and affording increased cirrus IWC sensitivity. The NOAA Water instrument was flown for the first time during the second deployment of the Airborne Tropical TRopopause EXperiment (ATTREX) in February-March 2013 on board the Global Hawk UAS. The instrument demonstrated a typical in-flight precision (1 s, 1 σ) of better than 0.17 parts per million (ppm, 10-6 mol/mol), with an overall H2O vapor measurement uncertainty of 5% ± 0.23 ppm. The inertial enhancement for cirrus cloud particle sampling under ATTREX flight conditions ranged from 33-48 for ice particles larger than 8 µm in diameter, depending primarily

  16. A two-channel, tunable diode laser-based hygrometer for measurement of water vapor and cirrus cloud ice water content in the upper troposphere and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Thornberry, T. D.; Rollins, A. W.; Gao, R. S.; Watts, L. A.; Ciciora, S. J.; McLaughlin, R. J.; Fahey, D. W.

    2015-01-01

    The recently developed NOAA Water instrument is a two-channel, closed-path, tunable diode laser absorption spectrometer designed for the measurement of upper troposphere/lower stratosphere water vapor and enhanced total water (vapor + inertially enhanced condensed phase) from the NASA Global Hawk unmanned aircraft system (UAS) or other high-altitude research aircraft. The instrument utilizes wavelength-modulated spectroscopy with second harmonic detection near 2694 nm to achieve high precision with a 79 cm double-pass optical path. The detection cells are operated under constant temperature, pressure, and flow conditions to maintain a constant sensitivity to H2O independent of the ambient sampling environment. An onboard calibration system is used to perform periodic in situ calibrations to verify the stability of the instrument sensitivity during flight. For the water vapor channel, ambient air is sampled perpendicular to the flow past the aircraft in order to reject cloud particles, while the total water channel uses a heated, forward-facing inlet to sample both water vapor and cloud particles. The total water inlet operates subisokinetically, thereby inertially enhancing cloud particle number in the sample flow and affording increased cloud water content sensitivity. The NOAA Water instrument was flown for the first time during the second deployment of the Airborne Tropical TRopopause EXperiment (ATTREX) in February-March 2013 on the NASA Global Hawk UAS. The instrument demonstrated a typical in-flight precision (1 s, 1σ) of better than 0.17 parts per million (ppm, 10-6 mol mol-1), with an overall H2O vapor measurement uncertainty of 5% ± 0.23 ppm. The inertial enhancement for cirrus cloud particle sampling under ATTREX flight conditions ranged from 33 to 48 for ice particles larger than 8 μm in diameter, depending primarily on aircraft altitude. The resulting ice water content detection limit (2σ) was 0.023-0.013 ppm, corresponding to approximately 2 μg m

  17. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  18. Alkali differentiation in LL-chondrites

    NASA Astrophysics Data System (ADS)

    Wlotzka, F.; Palme, H.; Spettel, B.; Wanke, H.; Fredriksson, K.; Noonan, A. F.

    1983-04-01

    The Kraehenberg and Bhola LL-group chondrites are heterogeneous agglomerates which contain a variety of lithic fragments and chondrules as well as crystal fragments. Both meteorites contain large, cm-sized fragments with high K enrichments. The K-rich inclusions are fragments of larger rock bodies which crystallized from melts of chondritic parent material that had previously been enriched in K and in heavier alkalies,while also being depleted in Na and metal. It is suggested that the K enrichment occurred as an exchange for Na in feldspars via a vapor phase, whose presence on the chondrite parent body (or bodies) is supported by the recent finding of fluid inclusions in chondritic silicates. Cooling rate considerations indicate that the K-rich rock units could not have been very large, implying that the K-rich materials were locally molten by, for example, impact.

  19. Water vapor lidar

    NASA Technical Reports Server (NTRS)

    Ellingson, R.; Mcilrath, T.; Schwemmer, G.; Wilkerson, T. D.

    1976-01-01

    The feasibility was studied of measuring atmospheric water vapor by means of a tunable lidar operated from the space shuttle. The specific method evaluated was differential absorption, a two-color method in which the atmospheric path of interest is traversed by two laser pulses. Results are reported.

  20. Environmental site description for a Uranium Atomic Vapor Laser Isotope Separation (U-AVLIS) production plant at the Oak Ridge Gaseous Diffusion Plant Site

    SciTech Connect

    Not Available

    1991-09-01

    In January 1990, the Secretary of Energy approved a plan for the demonstration and deployment of the Uranium Atomic Vapor Laser Isotope Separation (U-AVLIS) technology, with the near-term goal to provide the necessary information to make a deployment decision by November 1992. The U-AVLIS process is based on electrostatic extraction of photoionized U-235 atoms from an atomic vapor stream created by electron-beam vaporization of uranium metal alloy. A programmatic document for use in screening DOE sites to locate the U-AVLIS production plant was developed and implemented in two parts (Wolsko et al. 1991). The first part consisted of a series of screening analyses, based on exclusionary and other criteria, that identified a reasonable number of candidate sites. These sites were then subjected to a more rigorous and detailed comparative analysis for the purpose of developing a short list of reasonable alternative sites for later environmental examination. This environmental site description (ESD) provides a detailed description of the ORGDP site and vicinity suitable for use in an environmental impact statement (EIS). The report is based on existing literature, data collected at the site, and information collected by Argonne National Laboratory (ANL) staff during a site visit. The organization of the ESD is as follows. Topics addressed in Sec. 2 include a general site description and the disciplines of geology, water resources, biotic resources, air resources, noise, cultural resources, land use, socioeconomics, and waste management. Identification of any additional data that would be required for an EIS is presented in Sec. 3. Following the site description and additional data requirements, Sec. 4 provides a short, qualitative assessment of potential environmental issues. 37 refs., 20 figs., 18 tabs.