WorldWideScience

Sample records for gas visible laser

  1. Electron-beam pumping of visible and ultraviolet gas lasers

    International Nuclear Information System (INIS)

    Bradley, L.P.

    1975-01-01

    Several techniques for using direct electron-pumping of gas lasers are reviewed. The primary objective is to categorize pump geometries and to give guidelines for gun selection and pulser design. Examples and application of pump technology are given

  2. Visible Solid State Lasers

    NARCIS (Netherlands)

    Hikmet, R.A.M.

    2007-01-01

    Diode lasers can be found in various applications most notably in optical communication and optical storage. Visible lasers were until recently were all based on IR diode lasers. Using GaN, directly blue and violet emitting lasers have also been introduced to the market mainly in the area of optical

  3. Chemical lasers in the visible

    International Nuclear Information System (INIS)

    Jones, C.R.; Broida, H.P.

    1974-01-01

    Since the beginning of the laser era in 1960, a continuing search for chemical lasers has been carried out. This quest has been influenced by the knowledge that many chemical reactions produce visible chemiluminescence and, therefore, partition some of the reaction products into emitting, electronically excited states. Such luminescence has been observed not only from low-pressure, gas-phase reactions, notably those of alkali metals and halogens, but also from a limited number of liquid-phase reactions. (U.S.)

  4. Visible laser dazzle

    Science.gov (United States)

    Eberle, B.; Forster, D.

    2016-10-01

    The presented work gives an overview on the efforts of the NATO SET-198 research task group. It comprises nonrestricted material, which is already published or is to be published in journals. Main topics are the development and validation of computer models in order to understand the impact of laser dazzling on the detection of objects in a scene but also on the accomplishment of visual-based tasks. The work includes laboratory and field dazzling tests on sensors and humans, computer eye-dazzle modeling, automatic character recognition and laboratory observer trials for validation purposes of the used algorithms. The impact of dazzling is studied in dependence of laser wavelength, laser power and camera type.

  5. Waveguide gas laser

    Science.gov (United States)

    Zedong, C.

    1982-05-01

    Waveguide gas lasers are described. Transmission loss of hollow tube light waveguides, coupling loss, the calculation of output power, and the width of the oscillation belt are discussed. The structure of a waveguide CO2 laser is described.

  6. Reactive pulsed laser deposition with gas jet

    International Nuclear Information System (INIS)

    Rakowski, R.; Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Szczurek, M.

    2001-01-01

    Different metal (Sn, Al, steel, Cu, W) thin films were synthesized by reactive pulsed laser deposition on steel, copper and glass wafers. In our work pulsed Nd:glass (10 J, 800μs) laser system was used. Jet of gas was created by electromagnetic valve perpendicularly to the laser beam. Nitrogen, oxygen and argon were used. We used several to tens laser shots to obtain visible with the naked eye layers. Thin layers were observed under an optical microscope. (author)

  7. High visibility reflective laser eye protection visor

    Science.gov (United States)

    Harasaki, Akiko; Sato, Koji; Sasaki, Tetsu; Tsunoda, Haruhiko; Sohara, Yoshio

    2005-09-01

    A combination of dielectric thin film and laser absorption dye technologies was introduced to fabricate a clear reflective aircrew's laser eye protection (LEP) visor. The interlayer and thin film layer materials for the high and low refractive indices are optimized. A clear visor with 26 % visibility was achieved for more than four optical densities (OD) LEP. In addition, an oxide compound film coating was explored to seek extra protection for the delaminating of the fragile multilayer dielectric thin film coating. As a side effect, applying surface-active agents on the oxide compound film resulted in good dustproof and anti-fog properties.

  8. Gas dynamic laser device

    International Nuclear Information System (INIS)

    Born, G.

    1975-01-01

    The gas dynamic laser device is provided with an expansion chamber arranged between a heating chamber for the CO-gas and the resonance chamber. The expansion chamber is initially evacuated for producing a rarefaction wave. Between the heating chamber and the expansion chamber there are arranged rapid release means such as a valve or a diaphragm. Pressure recovering means are connected to the other side of the resonance chamber

  9. Electrically Injected UV-Visible Nanowire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  10. High power diode lasers converted to the visible

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Hansen, Anders Kragh; Andersen, Peter E.

    2017-01-01

    High power diode lasers have in recent years become available in many wavelength regions. However, some spectral regions are not well covered. In particular, the visible spectral range is lacking high power diode lasers with good spatial quality. In this paper, we highlight some of our recent...... results in nonlinear frequency conversion of high power near infrared diode lasers to the visible spectral region....

  11. Emerging technologies for compact visible laser sources

    International Nuclear Information System (INIS)

    Forrest, G.T.

    1988-01-01

    A number of laser and non-linear optical technologies and converging on commercial designs. High power laser diodes and non-linear materials are being incorporated in prototype lasers, many of which will become commercially available products during the next 1-5 years. This paper reviews the output characteristics of such lasers. Lasers which are discussed include direct doubling of laser diodes based on proton exchanged lithium niobate, fiber lasers, frequency doubled diode pumped Nd:YAG lasers, and sum frequency mixed Nd:YAG lasers. Such lasers are capable of providing milliwatt output powers in the green and/or blue spectral regions

  12. Laser anemometer signals: visibility characteristics and application to particle sizing.

    Science.gov (United States)

    Adrian, R J; Orloff, K L

    1977-03-01

    The signal visibility characteristics of a dual beam laser anemometer operated in a backscatter mode have been investigated both experimentally and analytically. The analysis is based on Mie's electromagnetic scattering theory for spherical particles and is exact within the limitations of the scattering theory. It is shown that the signal visibility is a function of the ratio of the particle diameter to the fringe spacing in a certain, restricted case; but more generally it also depends on the Mie scattering size parameter, refractive index, the illuminating beam polarization, and the size, shape, and location of the light collecting aperture. The character of backscatter signal visibility differs significantly from the forward scatter case, and it is concluded that backscatter measurements of particle diameters using the visibility sizing technique may not always be possible. Restrictions on the forward scatter application of the visibility sizing method are also discussed.

  13. Visible Lasers and Emerging Color Converters for Lighting and Visible Light Communications

    KAUST Repository

    Shen, Chao

    2017-10-30

    GaN-based lasers are promising for white lighting and visible-light communication (VLC). The advances of III-nitride photonic integration, and the application of YAG crystal and perovskite-based phosphors to lighting and VLC will be discussed.

  14. Laser and gas centrifuge enrichment

    Science.gov (United States)

    Heinonen, Olli

    2014-05-01

    Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future.

  15. Laser-induced gas plasma machining

    Energy Technology Data Exchange (ETDEWEB)

    Elhadj, Selim; Bass, Isaac Louis; Guss, Gabriel Mark; Matthews, Manyalibo J.

    2017-10-17

    Techniques for removing material from a substrate are provided. A laser beam is focused at a distance from the surface to be treated. A gas is provided at the focus point. The gas is dissociated using the laser energy to generate gas plasma. The substrate is then brought in contact with the gas plasma to enable material removal.

  16. Gas-ion laser with gas pressure maintenance means

    International Nuclear Information System (INIS)

    Thatcher, J.B.

    1975-01-01

    A gas-ion laser is described including means to maintain the ionizable gas in the laser cavity at a rather constant pressure over an extended period of time to significantly increase the useful life of the gas-ion laser. The gas laser includes a gas makeup system having a high pressure source or storage container and a regulating valve. The valve has a permeable solid state orifice member through which the gas flows from the high pressure source to the laser cavity to replenish the gas in the laser cavity and maintain the gas pressure in the cavity rather constant. The permeable orifice member is selected from a solid state material having a permeability that is variable in relation to the magnitude of the energy applied to the orifice member. The gas-ion laser has a valve operating means such as a heater for varying the applied energy such as thermal energy to the member to regulate the gas flow. Additionally, the gas-ion laser has a valve control means that is responsive to the gas pressure in the laser cavity for controlling the valve control means to maintain the pressure at a desired level. (U.S.)

  17. Multielectron effects in the photoelectron momentum distribution of noble-gas atoms driven by visible-to-infrared-frequency laser pulses: A time-dependent density-functional-theory approach

    Science.gov (United States)

    Murakami, Mitsuko; Zhang, G. P.; Chu, Shih-I.

    2017-05-01

    We present the photoelectron momentum distributions (PMDs) of helium, neon, and argon atoms driven by a linearly polarized, visible (527-nm) or near-infrared (800-nm) laser pulse (20 optical cycles in duration) based on the time-dependent density-functional theory (TDDFT) under the local-density approximation with a self-interaction correction. A set of time-dependent Kohn-Sham equations for all electrons in an atom is numerically solved using the generalized pseudospectral method. An effect of the electron-electron interaction driven by a visible laser field is not recognizable in the helium and neon PMDs except for a reduction of the overall photoelectron yield, but there is a clear difference between the PMDs of an argon atom calculated with the frozen-core approximation and TDDFT, indicating an interference of its M -shell wave functions during the ionization. Furthermore, we find that the PMDs of degenerate p states are well separated in intensity when driven by a near-infrared laser field, so that the single-active-electron approximation can be adopted safely.

  18. Visible and ultraviolet light sources based nonlinear interaction of lasers

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Tidemand-Lichtenberg, Peter; Jain, Mayank

    Different light sources can be used for optically stimulated luminescence measurements and usually a halogen lamp in combination with filters or light emitting diodes (LED’s) are used to provide the desired stimulation wavelength. However lasers can provide a much more well-defined beam, very nar...... for synthesizing any wavelength in the visible and ultraviolet light based sum frequency generation between two lasers is presented.......Different light sources can be used for optically stimulated luminescence measurements and usually a halogen lamp in combination with filters or light emitting diodes (LED’s) are used to provide the desired stimulation wavelength. However lasers can provide a much more well-defined beam, very...

  19. High power visible diode laser for the treatment of eye diseases by laser coagulation

    Science.gov (United States)

    Heinrich, Arne; Hagen, Clemens; Harlander, Maximilian; Nussbaumer, Bernhard

    2015-03-01

    We present a high power visible diode laser enabling a low-cost treatment of eye diseases by laser coagulation, including the two leading causes of blindness worldwide (diabetic retinopathy, age-related macular degeneration) as well as retinopathy of prematurely born children, intraocular tumors and retinal detachment. Laser coagulation requires the exposure of the eye to visible laser light and relies on the high absorption of the retina. The need for treatment is constantly increasing, due to the demographic trend, the increasing average life expectancy and medical care demand in developing countries. The World Health Organization reacts to this demand with global programs like the VISION 2020 "The right to sight" and the following Universal Eye Health within their Global Action Plan (2014-2019). One major point is to motivate companies and research institutes to make eye treatment cheaper and easily accessible. Therefore it becomes capital providing the ophthalmology market with cost competitive, simple and reliable technologies. Our laser is based on the direct second harmonic generation of the light emitted from a tapered laser diode and has already shown reliable optical performance. All components are produced in wafer scale processes and the resulting strong economy of scale results in a price competitive laser. In a broader perspective the technology behind our laser has a huge potential in non-medical applications like welding, cutting, marking and finally laser-illuminated projection.

  20. GAS LASERS FOR STRONG-FIELD APPLICATIONS.

    Energy Technology Data Exchange (ETDEWEB)

    POGORELSKY,I.V.

    2004-09-15

    Atomic-, molecular- and excimer-gas lasers employ variety of pumping schemes including electric discharge, optical, or chemical reactions and cover a broad spectral range from UV to far-IR. Several types of gas lasers can produce multi-kilojoule pulses and kilowatts of average power. Among them, excimer- and high-pressure molecular lasers have sufficient bandwidth for generating pico- and femtosecond pulses. Projects are underway and prospects are opening up to bring ultrafast gas laser technology to the front lines of advanced accelerator applications.

  1. Closed cycle gas dynamic laser

    International Nuclear Information System (INIS)

    Pinsley, E.A.

    1975-01-01

    The device includes a closed cycle gasdynamic laser wherein the lasing fluid is recirculated in a closed loop. The closed loop includes a nozzle array, a lasing cavity and a diffuser. The exit of the diffuser is connected to the inlet to the nozzle array with a fuel heat exchanger located in the lasing flow and a pumping means located between the heat exchanger and the nozzle array. To provide for cooling of the pumping means and to improve diffuser performance, gas bled from the diffuser is cooled by two heat exchangers and pumped into cooling passages in the pumping means. The heat exchangers for cooling the flow to the pumping means are located in series and carry fuel from a supply to an injector in said combustor and the heat exchanger in the lasing flow cools the fluid and carries the fuel from a supply to an injector in said combustor. (U.S.)

  2. The high frequency characteristics of laser reflection and visible light during solid state disk laser welding

    International Nuclear Information System (INIS)

    Gao, Xiangdong; You, Deyong; Katayama, Seiji

    2015-01-01

    Optical properties are related to weld quality during laser welding. Visible light radiation generated from optical-induced plasma and laser reflection is considered a key element reflecting weld quality. An in-depth analysis of the high-frequency component of optical signals is conducted. A combination of a photoelectric sensor and an optical filter helped to obtain visible light reflection and laser reflection in the welding process. Two groups of optical signals were sampled at a high sampling rate (250 kHz) using an oscilloscope. Frequencies in the ranges 1–10 kHz and 10–125 kHz were investigated respectively. Experimental results showed that there was an obvious correlation between the high-frequency signal and the laser power, while the high-frequency signal was not sensitive to changes in welding speed. In particular, when the defocus position was changed, only a high frequency of the visible light signal was observed, while the high frequency of the laser reflection signal remained unchanged. The basic correlation between optical features and welding status during the laser welding process is specified, which helps to provide a new research focus for investigating the stability of welding status. (letter)

  3. Introduction to gas lasers with emphasis on selective excitation processes

    CERN Document Server

    Willett, Colin S

    1974-01-01

    Introduction to Gas Lasers: Population Inversion Mechanisms focuses on important processes in gas discharge lasers and basic atomic collision processes that operate in a gas laser. Organized into six chapters, this book first discusses the historical development and basic principles of gas lasers. Subsequent chapters describe the selective excitation processes in gas discharges and the specific neutral, ionized and molecular laser systems. This book will be a valuable reference on the behavior of gas-discharge lasers to anyone already in the field.

  4. Power stabilized CO2 gas transport laser

    International Nuclear Information System (INIS)

    Foster, J.D.; Kirk, R.F.; Moreno, F.E.; Ahmed, S.A.

    1975-01-01

    The output power of a high power (1 kW or more) CO 2 gas transport laser is stabilized by flowing the gas mixture over copper plated baffles in the gas channel during operation of the laser. Several other metals may be used instead of copper, for example, nickel, manganese, palladium, platinum, silver and gold. The presence of copper in the laser gas circuit stabilizes output power by what is believed to be a compensation of the chemical changes in the gas due to the cracking action of the electrical discharge which has the effect of diminishing the capactiy of the carbon dioxide gas mixture to maintain the rated power output of the laser. (U.S.)

  5. Novel gas target for laser wakefield accelerators

    Science.gov (United States)

    Aniculaesei, C.; Kim, Hyung Taek; Yoo, Byung Ju; Oh, Kyung Hwan; Nam, Chang Hee

    2018-02-01

    A novel gas target for interactions between high power lasers and gaseous medium, especially for laser wakefield accelerators, has been designed, manufactured, and characterized. The gas target has been designed to provide a uniform density profile along the central gas cell axis by combining a gas cell and slit nozzle. The gas density has been tuned from ˜1017 atoms/cm3 to ˜1019 atoms/cm3 and the gas target length can be varied from 0 to 10 cm; both changes can be made simultaneously while keeping the uniform gas profile. The gas density profile inside the gas cell has been measured using interferometry and validated using computational fluid dynamics.

  6. Multitube coaxial closed cycle gas laser system

    International Nuclear Information System (INIS)

    Davis, J.W.; Walch, A.P.

    1975-01-01

    A gas laser design capable of long term reliable operation in a commercial environment is disclosed. Various construction details which insulate the laser optics from mechanical distortions and vibrations inevitably present in the environment are developed. Also, a versatile optical cavity made up of modular units which render the basic laser configuration adaptable to alternate designs with different output capabilities is shown in detail. The system built around a convection laser operated in a closed cycle and the working medium is a gas which is excited by direct current electric discharges. (auth)

  7. Compact electron accelerator for pumping gas lasers

    International Nuclear Information System (INIS)

    Duncan, C.V.; Bradley, L.P.

    1976-01-01

    A description is given of the design and application of a simple e-beam generator for the repetitive pulse pumping of gas lasers. The circuit uses a low inductance Marx and series tuned pulse forming elements

  8. Singly-resonant sum frequency generation of visible light in a semiconductor disk laser

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Schlosser, P.J.; Hastie, J.E.

    2009-01-01

    In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a singlepass of the solid......-state laser light. This exploits the good beam quality and high intra-cavity power present in the semiconductor disk laser to achieve high conversion efficiency. Combining sum frequency mixing and semiconductor disk lasers in this manner allows in principle for generation of any wavelength within the visible...

  9. Kinetic studies of gas mixtures and their application to gas lasers and pollutant detection

    International Nuclear Information System (INIS)

    Chen, C.H.; Judish, J.P.; Payne, M.G.

    1978-01-01

    A 2-MeV proton beam with a 10-ns pulse width was used to excite various gas mixtures. The emitted vacuum ultraviolet (500 A to 2000 A) and ultraviolet visible (2000 A to 8000 A) photons passing through separate monochromators were detected by using single photon counting techniques. Time-resolved and time-integrated fluorescent spectroscopy was used to study the detailed mechanism of excitation energy transfer, Penning ionization, charge transfer, and ion-ion recombination processes. The energy precursors of various excited species in a number of gas mixtures were identified, and the quenching rates of excited atoms and ions by numerous small molecules were measured. Relative fluorescence efficiencies and energy pathways of proton-excited gas mixtures were used to study the kinetics of high power gas lasers. An ultrasensitive method for the detection of certain pollutants utilizing energy or charge transfer processes in proton-excited gas mixtures has been developed

  10. Laser Additive Manufacturing of Gas Permeable Structures

    Science.gov (United States)

    Klahn, C.; Bechmann, F.; Hofmann, S.; Dinkel, M.; Emmelmann, C.

    Laser additive manufacturing offers a variety of new design possibilities. In mold making laser additive manufactured inserts with conformal cooling channels are already state of the art. Pneumatic ejectors for injection molds are a new application for laser additive manufacturing. The pneumatic ejectors require a durable gas permeable material. This material is produced by placing the scan vectors for the laser additive manufacturing process in a defined pattern. Trials with different plastics proofed the function and reliability of the pneumatic ejector concept in the injection molding cycle.

  11. Optically pumped microplasma rare gas laser.

    Science.gov (United States)

    Rawlins, W T; Galbally-Kinney, K L; Davis, S J; Hoskinson, A R; Hopwood, J A; Heaven, M C

    2015-02-23

    The optically pumped rare-gas metastable laser is a chemically inert analogue to three-state optically pumped alkali laser systems. The concept requires efficient generation of electronically excited metastable atoms in a continuous-wave (CW) electric discharge in flowing gas mixtures near atmospheric pressure. We have observed CW optical gain and laser oscillation at 912.3 nm using a linear micro-discharge array to generate metastable Ar(4s, 1s(5)) atoms at atmospheric pressure. We observed the optical excitation of the 1s(5) → 2p(9) transition at 811.5 nm and the corresponding fluorescence, optical gain and laser oscillation on the 2p(10) ↔ 1s(5) transition at 912.3 nm, following 2p(9)→2p(10) collisional energy transfer. A steady-state kinetics model indicates efficient collisional coupling within the Ar(4s) manifold.

  12. Two-laser induced selective infrared-visible fluorescence for thin film analysis

    International Nuclear Information System (INIS)

    Richardson, J.H.; Dering, J.P.; Johnson, D.C.; Hrubesh, L.W.

    1980-01-01

    A laser technique has been developed to enhance its sensitivity for thin film analysis of mixtures. A c-w visible or uv laser was used to stimulate visible fluorescence from a thin fluorophor film, and a chopped low-power infrared laser was used to selectively excite characteristic infrared absorption bands in the sample. The resulting modulated visible fluorescence signal was monitored by an optical detection system. The technqiue has been applied to the quantitative determination of mixtures of coumarin 7, rubene, and rhodamine 6G; however, quantitative analysis has been impossible due to the difficulty in obtaining a uniform thin film

  13. Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

    International Nuclear Information System (INIS)

    Danilov, P A; Zayarnyi, D A; Ionin, A A; Kudryashov, S I; Makarov, S V; Rudenko, A A; Saraeva, I N; Yurovskikh, V I; Lednev, V N; Pershin, S M

    2015-01-01

    The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fields and their applications)

  14. FAST TRACK COMMUNICATION: Inactivation of viruses with a very low power visible femtosecond laser

    Science.gov (United States)

    Tsen, K. T.; Tsen, Shaw-Wei D.; Chang, Chih-Long; Hung, Chien-Fu; Wu, T.-C.; Kiang, Juliann G.

    2007-08-01

    We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. By using a very low power visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW cm-2. The inactivation of M13 phages was determined by plaque counts and depended on the pulse width as well as power density of the excitation laser.

  15. Inactivation of viruses with a very low power visible femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Tsen, K T [Department of Physics, Arizona State University, Tempe, AZ 85287 (United States); Tsen, Shaw-Wei D [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Chang, C.-L. [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Hung, C.-F. [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Wu, T-C [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Kiang, Juliann G [Scientific Research Department, Armed Forces Radiobiology Research Institute, Uniformed Services University of The Health Sciences, Bethesda, MD 20889-5603 (United States)

    2007-08-15

    We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. By using a very low power visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW cm{sup -2}. The inactivation of M13 phages was determined by plaque counts and depended on the pulse width as well as power density of the excitation laser. (fast track communication)

  16. Gas lasers applied atomic collision physics, v.3

    CERN Document Server

    McDaniel, E W

    1982-01-01

    Applied Atomic Collision Physics, Volume 3: Gas Lasers describes the applications of atomic collision physics in the development of many types of gas lasers. Topics covered range from negative ion formation in gas lasers to high-pressure ion kinetics and relaxation of molecules exchanging vibrational energy. Ion-ion recombination in high-pressure plasmas is also discussed, along with electron-ion recombination in gas lasers and collision processes in chemical lasers.Comprised of 14 chapters, this volume begins with a historical summary of gas laser developments and an overview of the basic ope

  17. Visible and ultraviolet spectroscopy of gas phase protein ions.

    Science.gov (United States)

    Antoine, Rodolphe; Dugourd, Philippe

    2011-10-06

    Optical spectroscopy has contributed enormously to our knowledge of the structure and dynamics of atoms and molecules and is now emerging as a cornerstone of the gas phase methods available for investigating biomolecular ions. This article focuses on the UV and visible spectroscopy of peptide and protein ions stored in ion traps, with emphasis placed on recent results obtained on protein polyanions, by electron photodetachment experiments. We show that among a large number of possible de-excitation pathways, the relaxation of biomolecular polyanions is mainly achieved by electron emission following photo-excitation in electronically excited states. Electron photodetachment is a fast process that occurs prior to relaxation on vibrational degrees of freedom. Electron photodetachment yield can then be used to record gas phase action spectra for systems as large as entire proteins, without the limitation of system size that would arise from energy redistribution on numerous modes and prevent fragmentation after the absorption of a photon. The optical activity of proteins in the near UV is directly related to the electronic structure and optical absorption of aromatic amino acids (Trp, Phe and Tyr). UV spectra for peptides and proteins containing neutral, deprotonated and radical aromatic amino acids were recorded. They displayed strong bathochromic shifts. In particular, the results outline the privileged role played by open shell ions in molecular spectroscopy which, in the case of biomolecules, is directly related to their reactivity and biological functions. The optical shifts observed are sufficient to provide unambiguous fingerprints of the electronic structure of chromophores without the requirement of theoretical calculations. They constitute benchmarks for calculating the absorption spectra of chromophores embedded in entire proteins and could be used in the future to study biochemical processes in the gas phase involving charge transfer in aromatic amino acids

  18. Infrared laser spectroscopic trace gas sensing

    Science.gov (United States)

    Sigrist, Markus

    2016-04-01

    Chemical sensing and analyses of gas samples by laser spectroscopic methods are attractive owing to several advantages such as high sensitivity and specificity, large dynamic range, multi-component capability, and lack of pretreatment or preconcentration procedures. The preferred wavelength range comprises the fundamental molecular absorption range in the mid-infared between 3 and 15 μm, whereas the near-infrared range covers the (10-100 times weaker) higher harmonics and combination bands. The availability of near-infrared and, particularly, of broadly tunable mid-infrared sources like external cavity quantum cascade lasers (EC-QCLs), interband cascade lasers (ICLs), difference frequency generation (DFG), optical parametric oscillators (OPOs), recent developments of diode-pumped lead salt semiconductor lasers, of supercontinuum sources or of frequency combs have eased the implementation of laser-based sensing devices. Sensitive techniques for molecular absorption measurements include multipass absorption, various configurations of cavity-enhanced techniques such as cavity ringdown (CRD), or of photoacoustic spectroscopy (PAS) including quartz-enhanced (QEPAS) or cantilever-enhanced (CEPAS) techniques. The application requirements finally determine the optimum selection of laser source and detection scheme. In this tutorial talk I shall discuss the basic principles, present various experimental setups and illustrate the performance of selected systems for chemical sensing of selected key atmospheric species. Applications include an early example of continuous vehicle emission measurements with a mobile CO2-laser PAS system [1]. The fast analysis of C1-C4 alkanes at sub-ppm concentrations in gas mixtures is of great interest for the petrochemical industry and was recently achieved with a new type of mid-infrared diode-pumped piezoelectrically tuned lead salt vertical external cavity surface emitting laser (VECSEL) [2]. Another example concerns measurements on short

  19. Optical Material Researches for Frontier Optical Ceramics and Visible Fiber Laser Technologies

    Science.gov (United States)

    2016-07-07

    Optics) were used. The beam spot size dependence on the z-axis, which is defined as the laser propagation direction, was measured by a micro -beam...profiler (MBP-100- USB ; Newport). Fig. 5 Experimental setup for visible fiber laser oscillator in Pr:DC-WPFGF. a) Measurem ent for input-output

  20. Rotational temperature determinations in molecular gas lasers

    International Nuclear Information System (INIS)

    Weaver, L.A.; Taylor, L.H.; Denes, L.J.

    1975-01-01

    The small-signal gain expressions for vibrational-rotational transitions are examined in detail to determine possible methods of extracting the rotational temperature from experimental gain measurements in molecular gas lasers. Approximate values of T/subr/ can be deduced from the rotational quantum numbers for which the P- and R-branch gains are maximum. Quite accurate values of T/subr/ and the population inversion density (n/subv//sub prime/-n/subv//sub double-prime/) can be determined by fitting data to suitably linearized gain relationships, or by performing least-squares fits of the P- and R-branch experimental data to the full gain expressions. Experimental gain measurements for 15 P-branch and 12 R-branch transitions in the 10.4-μm CO 2 band have been performed for pulsed uv-preionized laser discharges in CO 2 : N 2 : He=1 : 2 : 3 mixtures at 600 Torr. These data are subjected to the several gain analyses described herein, yielding a rotational temperature of 401plus-or-minus10 degreeK and an inversion density of (3.77plus-or-minus0.07) times10 17 cm -3 for conditions of maximum gain. These techniques provide accurate values of the gas temperature in molecular gas lasers with excellent temporal and spatial resolution, and should be useful in extending the conversion efficiency and arcing limits of high-energy electrically exc []ted lasers

  1. Optical Material Researches for Frontier Optical Ceramics and Visible Fiber Laser Technologies

    Science.gov (United States)

    2016-07-07

    are very useful for scientific and industrial applications. 15. SUBJECT TERMS Fibre Lasers, Laser Dynamics, Nonlinear Optical Materials 16. SECURITY...AFRL-AFOSR-JP-TR-2016-0059 Optical material researches for frontier optical ceramics and visible fiber laser technologies Yasushi Fujimoto Osaka...07-2016 2. REPORT TYPE Final 3. DATES COVERED (From - To) 18 Apr 2013 to 17 Apr 2016 4. TITLE AND SUBTITLE Optical material researches for frontier

  2. Two-Laser Interference Visible to the Naked Eye

    Science.gov (United States)

    Kawalec, Tomasz; Bartoszek-Bober, Dobroslawa

    2012-01-01

    An experimental setup allowing the observation of two-laser interference by the naked eye is described. The key concept is the use of an electronic phase lock between two external cavity diode lasers. The experiment is suitable both for undergraduate and graduate students, mainly in atomic physics laboratories. It gives an opportunity for…

  3. Cutting and drilling studies using high power visible lasers

    International Nuclear Information System (INIS)

    Kautz, D.D.; Dragon, E.P.; Werve, M.E.; Hargrove, R.S.; Warner, B.E.

    1993-01-01

    High power and radiance laser technologies developed at Lawrence Livermore National Laboratory such as copper-vapor and dye lasers show great promise for material processing tasks. Evaluation of models suggests significant increases in welding, cutting, and drilling capabilities, as well as applications in emerging technologies such as micromachining, surface treatment, and stereolithography. Copper lasers currently operate at 1.8 kW output at approximately three times the diffraction limit and achieve mean time between failures of more than 1,000 hours. Dye lasers have near diffraction limited beam quality at greater than 1.0 kW. Results from cutting and drilling studies in titanium and stainless steel alloys show that cuts and holes with extremely fine features can be made with dye and copper-vapor lasers. High radiance beams produce low distortion and small heat-affected zones. The authors have accomplished very high aspect ratios (> 60:1) and features with micron scale (5-50 μm) sizes. The paper gives a description of the equipment; discusses cutting theory; and gives experimental results of cutting and drilling studies on Ti-6Al-4V and 304 stainless steel

  4. All-fiber femtosecond Cherenkov laser at visible wavelengths

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe Visbech

    2013-01-01

    -matching condition [1]. The resonant ultrafast wave conversion via the fiber-optic CR mechanism is instrumental for applications in biophotonics such as bio-imaging and microscopy [2]. In this work, we demonstrate a highly-stable all-fiber, fully monolithic CR system based on an Yb-fiber femtosecond laser, producing...

  5. Gas detectors for x-ray lasers

    International Nuclear Information System (INIS)

    Tiedtke, K.; Feldhaus, J.; Hahn, U.; Jastrow, U.; Nunez, T.; Tschentscher, T.; Bobashev, S. V.; Sorokin, A. A.; Hastings, J. B.; Moeller, S.; Cibik, L.; Gottwald, A.; Hoehl, A.; Kroth, U.; Krumrey, M.; Schoeppe, H.; Ulm, G.; Richter, M.

    2008-01-01

    We have developed different types of photodetectors that are based on the photoionization of a gas at a low target density. The almost transparent devices were optimized and tested for online photon diagnostics at current and future x-ray free-electron laser facilities on a shot-to-shot basis with a temporal resolution of better than 100 ns. Characterization and calibration measurements were performed in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin. As a result, measurement uncertainties of better than 10% for the photon-pulse energy and below 20 μm for the photon-beam position were achieved at the Free-electron LASer in Hamburg (FLASH). An upgrade for the detection of hard x-rays was tested at the Sub-Picosecond Photon Source in Stanford

  6. Gas detectors for x-ray lasers

    Science.gov (United States)

    Tiedtke, K.; Feldhaus, J.; Hahn, U.; Jastrow, U.; Nunez, T.; Tschentscher, T.; Bobashev, S. V.; Sorokin, A. A.; Hastings, J. B.; Möller, S.; Cibik, L.; Gottwald, A.; Hoehl, A.; Kroth, U.; Krumrey, M.; Schöppe, H.; Ulm, G.; Richter, M.

    2008-05-01

    We have developed different types of photodetectors that are based on the photoionization of a gas at a low target density. The almost transparent devices were optimized and tested for online photon diagnostics at current and future x-ray free-electron laser facilities on a shot-to-shot basis with a temporal resolution of better than 100 ns. Characterization and calibration measurements were performed in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin. As a result, measurement uncertainties of better than 10% for the photon-pulse energy and below 20 μm for the photon-beam position were achieved at the Free-electron LASer in Hamburg (FLASH). An upgrade for the detection of hard x-rays was tested at the Sub-Picosecond Photon Source in Stanford.

  7. Laser ablation of lysozyme with UV, visible and infrared femto- and nanosecond pulses

    OpenAIRE

    Schou, Jørgen; Canulescu, Stela; Matei, Andreea; Cazzaniga, Andrea Carlo; Constantinescu, Catalin; Amoruso, S.; Wang, X.; Bruzzese, R.; Dinescu, M.

    2013-01-01

    Lysozyme is an interesting molecule for laser ablation of organic materials, because the ablation has been comprehensively studied, it is a medium heavy molecule with a mass of 14305 Da, which can be detected by standard techniques, and because it is used as a bactericidal protein in the food industry. Lysozyme molecules do not absorb energy for wavelengths above 310 nm, but nevertheless there is a strong mass loss by ablation for laser irradiation in the visible regime. The total ablation yi...

  8. Ablation from metals induced by visible and UV laser irradiation

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Schou, Jørgen; Thestrup Nielsen, Birgitte

    1996-01-01

    The deposition rate of laser-ablated silver has been determined for fluences between 0.5 and 15 J/cm2 at the wavelengths 532 and 355 nm for a beam spot area of around 0.01 cm2. The ablated metal was collected on a quartz crystal microbalance. The rate at 5 J/cm2 was about 4 × 1013 Ag/cm2 per puls...

  9. Inactivation of viruses by coherent excitations with a low power visible femtosecond laser

    Directory of Open Access Journals (Sweden)

    Wu T-C

    2007-06-01

    Full Text Available Abstract Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

  10. Status of the visible Free-Electron Laser at the Brookhaven Accelerator Test Facility

    International Nuclear Information System (INIS)

    Batchelor, K.; Ben-Zvi, I.; Fernow, R.C.; Fisher, A.S.; Friedman, A.; Gallardo, J.; Ingold, G.; Kirk, H.; Kramer, S.; Lin, L.; Rogers, J.T.; Sheehan, J.F.; van Steenbergen, A.; Woodle, M.; Xie, J.; Yu, L.H.; Zhang, R.; Bhowmik, A.

    1991-01-01

    The 500 nm Free-Electron Laser (ATF) of the Brookhaven National Laboratory is reviewed. We present an overview of the ATF, a high-brightness, 50-MeV, electron accelerator and laser complex which is a users' facility for accelerator and beam physics. A number of laser acceleration and FEL experiments are under construction at the ATF. The visible FEL experiment is based on a novel superferric 8.8 mm period undulator. The electron beam parameters, the undulator, the optical resonator, optical and electron beam diagnostics are discussed. The operational status of the experiment is presented. 22 refs., 7 figs

  11. Long life gas laser system and method

    International Nuclear Information System (INIS)

    Hochuli, E.E.

    1975-01-01

    A long life gas discharge laser having an improved self-repairing cathode system is described. In a specific embodiment, water vapor having a partial pressure below about 10 -5 torr incorporated in a molecular sieve is used to provide impurities (in this case water vapor) for repairing the cathode surface by regenerating the oxide surface and/or preventing same from deteriorating. Other impurities may be incorporated in the molecular sieve such as hydrogen, oxygen, for example. In some cases CO 2 may be used. This application includes material disclosed in a paper entitled ''Continuation of the Investigation into Material Properties Affecting the Frequency Stability and Reliability of He-Ne Laser Structures'' submitted to the Office of Naval Research dated June 1972 by the inventor hereof and also a paper entitled ''Investigations of the Long Term Frequency Stability of Stable Laser Structures'' Progress Report for ONR Contract N00014-67-A-D239-0016 July 1972 by the inventor hereof. A royalty free license is hereby granted to the United States for use of the invention for all government purposes. (auth)

  12. Compact and portable multiline UV and visible Raman lasers in hydrogen-filled HC-PCF.

    Science.gov (United States)

    Wang, Y Y; Couny, F; Light, P S; Mangan, B J; Benabid, F

    2010-04-15

    We report on the realization of compact UV visible multiline Raman lasers based on two types of hydrogen-filled hollow-core photonic crystal fiber. The first, with a large pitch Kagome lattice structure, offers a broad spectral coverage from near IR through to the much sought after yellow, deep-blue and UV, whereas the other, based on photonic bandgap guidance, presents a pump conversion concentrated in the visible region. The high Raman efficiency achieved through these fibers allows for compact, portable diode-pumped solid-state lasers to be used as pumps. Each discrete component of this laser system exhibits a spectral density several orders of magnitude larger than what is achieved with supercontinuum sources and a narrow linewidth, making it an ideal candidate for forensics and biomedical applications.

  13. Laser non-uniformity smoothing using gas jets

    Czech Academy of Sciences Publication Activity Database

    Batani, D.; Dezulian, R.; Redaelli, R.; Benocci, R.; Stabile, H.; Canova, F.; Lucchini, G.; Koenig, M.; Krouský, Eduard; Mašek, Karel; Pfeifer, Miroslav; Skála, Jiří; Dudžák, Roman; Desai, T.; Tikhonchuk, V.; Faure, B.; Malka, V.

    2008-01-01

    Roč. 112, - (2008), 022045/1-022045/4 ISSN 1742-6588 R&D Projects: GA MŠk(CZ) LC528 EU Projects: European Commission(XE) 506350 - LASER LAB-EUROPE Institutional research plan: CEZ:AV0Z10100523 Keywords : laser smoothing technique * gas jet Subject RIV: BH - Optics, Masers, Laser s

  14. Visibility graph network analysis of natural gas price: The case of North American market

    Science.gov (United States)

    Sun, Mei; Wang, Yaqi; Gao, Cuixia

    2016-11-01

    Fluctuations in prices of natural gas significantly affect global economy. Therefore, the research on the characteristics of natural gas price fluctuations, turning points and its influencing cycle on the subsequent price series is of great significance. Global natural gas trade concentrates on three regional markets: the North American market, the European market and the Asia-Pacific market, with North America having the most developed natural gas financial market. In addition, perfect legal supervision and coordinated regulations make the North American market more open and more competitive. This paper focuses on the North American natural gas market specifically. The Henry Hub natural gas spot price time series is converted to a visibility graph network which provides a new direction for macro analysis of time series, and several indicators are investigated: degree and degree distribution, the average shortest path length and community structure. The internal mechanisms underlying price fluctuations are explored through the indicators. The results show that the natural gas prices visibility graph network (NGP-VGN) is of small-world and scale-free properties simultaneously. After random rearrangement of original price time series, the degree distribution of network becomes exponential distribution, different from the original ones. This means that, the original price time series is of long-range negative correlation fractal characteristic. In addition, nodes with large degree correspond to significant geopolitical or economic events. Communities correspond to time cycles in visibility graph network. The cycles of time series and the impact scope of hubs can be found by community structure partition.

  15. Diode laser absorption sensors for gas-dynamic and combustion flows

    Science.gov (United States)

    Allen, M. G.

    1998-01-01

    Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room

  16. Infrared and visible laser spectroscopy for highly-charged Ni-like ions

    Science.gov (United States)

    Ralchenko, Yuri

    2017-10-01

    Application of visible or infrared (IR) lasers for spectroscopy of highly-charged ions (HCI) has not been particularly extensive so far due to a mismatch in typical energies. We show here that the energy difference between the two lowest levels within the first excited configuration 3d9 4 s in Ni-like ions of heavy elements from ZN = 60 to ZN = 92 is within the range of visible or near-IR lasers. The wavelengths of these transitions are calculated within the relativistic model potential formalism and compared with other theoretical and limited experimental data. Detailed collisional-radiative simulations of non-Maxwellian and thermal plasmas are performed showing that photopumping between these levels using relatively moderate lasers is sufficient to provide a two-order of magnitude increase of the pumped level population. This accordingly results in a similar rise of the X-ray line intensity thereby allowing control of X-ray emission with visible/IR lasers.

  17. Laser-ablated active doping technique for visible spectroscopy measurements on Z.

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, Matthew Robert

    2013-09-01

    Visible spectroscopy is a powerful diagnostic, allowing plasma parameters ranging from temperature and density to electric and magnetic fields to be measured. Spectroscopic dopants are commonly introduced to make these measurements. On Z, dopants are introduced passively (i.e. a salt deposited on a current-carrying surface); however, in some cases, passive doping can limit the times and locations at which measurements can be made. Active doping utilizes an auxiliary energy source to disperse the dopant independently from the rest of the experiment. The objective of this LDRD project was to explore laser ablation as a method of actively introducing spectroscopic dopants. Ideally, the laser energy would be delivered to the dopant via fiber optic, which would eliminate the need for time-intensive laser alignments in the Z chamber. Experiments conducted in a light lab to assess the feasibility of fibercoupled and open-beam laser-ablated doping are discussed.

  18. Laser interferometry of radiation driven gas jets

    Science.gov (United States)

    Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

    2017-06-01

    In a series of experiments performed at the 1MA Zebra pulsed power accelerator of the Nevada Terawatt Facility nitrogen gas jets were driven with the broadband x-ray flux produced during the collapse of a wire-array z-pinch implosion. The wire arrays were comprised of 4 and 8, 10μm-thick gold wires and 17μm-thick nickel wires, 2cm and 3cm tall, and 0.3cm in diameter. They radiated 12kJ to 16kJ of x-ray energy, most of it in soft x-ray photons of less than 1keV of energy, in a time interval of 30ns. This x-ray flux was used to drive a nitrogen gas jet located at 0.8cm from the axis of the z-pinch radiation source and produced with a supersonic nozzle. The x-ray flux ionizes the nitrogen gas thus turning it into a photoionized plasma. We used laser interferometry to probe the ionization of the plasma. To this end, a Mach-Zehnder interferometer at the wavelength of 266 nm was set up to extract the atom number density profile of the gas jet just before the Zebra shot, and air-wedge interferometers at 266 and 532 nm were used to determine the electron number density of the plasma right during the Zebra shot. The ratio of electron to atom number densities gives the distribution of average ionization state of the plasma. A python code was developed to perform the image data processing, extract phase shift spatial maps, and obtain the atom and electron number densities via Abel inversion. Preliminary results from the experiment are promising and do show that a plasma has been created in the gas jet driven by the x-ray flux, thus demonstrating the feasibility of a new experimental platform to study photoionized plasmas in the laboratory. These plasmas are found in astrophysical scenarios including x-ray binaries, active galactic nuclei, and the accretion disks surrounding black holes1. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.1R. C. Mancini et al, Phys. Plasmas 16, 041001 (2009)

  19. Measurement of Gas and Aerosol Phase Absorption Spectra across the Visible and Near-IR Using Supercontinuum Photoacoustic Spectroscopy.

    Science.gov (United States)

    Radney, James G; Zangmeister, Christopher D

    2015-07-21

    We demonstrate a method to measure the absorption spectra of gas and aerosol species across the visible and near-IR (500 to 840 nm) using a photoacoustic (PA) spectrometer and a pulsed supercontinuum laser source. Measurements of gas phase absorption spectra were demonstrated using H2O(g) as a function of relative humidity (RH). The measured absorption intensities and peak shapes were able to be quantified and compared to spectra calculated using the 2012 High Resolution Transmission (HITRAN2012) database. Size and mass selected nigrosin aerosol was used to measure absorption spectra across the visible and near-IR. Spectra were measured as a function of aerosol size/mass and show good agreement to Mie theory calculations. Lastly, we measured the broadband absorption spectrum of flame generated soot aerosol at 5% and 70% RH. For the high RH case, we are able to quantifiably separate the soot and water absorption contributions. For soot, we observe an enhancement in the mass specific absorption cross section ranging from 1.5 at 500 nm (p < 0.01) to 1.2 at 840 nm (p < 0.2) and a concomitant increase in the absorption Ångström exponent from 1.2 ± 0.4 (5% RH) to 1.6 ± 0.3 (70% RH).

  20. High Performance self-injection locked 524 nm green laser diode for high bitrate visible light communications

    KAUST Repository

    Shamim, Md. Hosne Mobarok

    2018-03-05

    First demonstration of self-injection locking on 524 nm visible laser diode is presented. Enhancement by ~440 MHz (~30%) in modulation bandwidth, ~7 times reduction in lasing linewidth, and ~10 dB improvement in SMSR is achieved.

  1. Repetitively pulsed gas-jet laser cutting of metals in an oxygen-containing gas

    International Nuclear Information System (INIS)

    Makashev, N K; Asmolov, E S; Buzykin, O G

    2000-01-01

    A model of the repetitively pulsed gas-jet laser cutting of thick metals in an oxidising gas is developed. It is shown that the optimal choice of the time-dependent (radiation) and beam-focusing parameters will make it possible to increase the average cutting rate by a factor of 1.5 - 1.8. (interaction of laser radiation with matter. laser plasma)

  2. Assisting Gas Optimization in CO2 Laser Welding

    DEFF Research Database (Denmark)

    Gong, Hui; Olsen, Flemming Ove

    1996-01-01

    are applied with three different flow rates for each of the gases. A number of systematic laboratory experiments is carried out by employing various experimental designs, 33 and 32 Factorial Design. In the experiments a CO2 laser is used to weld thin sheets of mild steel. The welding specimens are evaluated....... The relations between the gas parameters and signal frequencies are studied. Finally the relationships of the gas parameters and weld characteristics are studied. The possibility of using photo diode signals in controlling the gas parameters is discussed.KeywordsCO2 laser welding, assisting gas parameters...

  3. High speed visible light communication using blue GaN laser diodes

    Science.gov (United States)

    Watson, S.; Viola, S.; Giuliano, G.; Najda, S. P.; Perlin, P.; Suski, T.; Marona, L.; Leszczyński, M.; Wisniewski, P.; Czernecki, R.; Targowski, G.; Watson, M. A.; White, H.; Rowe, D.; Laycock, L.; Kelly, A. E.

    2016-10-01

    GaN-based laser diodes have been developed over the last 20 years making them desirable for many security and defence applications, in particular, free space laser communications. Unlike their LED counterparts, laser diodes are not limited by their carrier lifetime which makes them attractive for high speed communication, whether in free space, through fiber or underwater. Gigabit data transmission can be achieved in free space by modulating the visible light from the laser with a pseudo-random bit sequence (PRBS), with recent results approaching 5 Gbit/s error free data transmission. By exploiting the low-loss in the blue part of the spectrum through water, data transmission experiments have also been conducted to show rates of 2.5 Gbit/s underwater. Different water types have been tested to monitor the effect of scattering and to see how this affects the overall transmission rate and distance. This is of great interest for communication with unmanned underwater vehicles (UUV) as the current method using acoustics is much slower and vulnerable to interception. These types of laser diodes can typically reach 50-100 mW of power which increases the length at which the data can be transmitted. This distance could be further improved by making use of high power laser arrays. Highly uniform GaN substrates with low defectivity allow individually addressable laser bars to be fabricated. This could ultimately increase optical power levels to 4 W for a 20-emitter array. Overall, the development of GaN laser diodes will play an important part in free space optical communications and will be vital in the advancement of security and defence applications.

  4. Transient processes in high-power gas laser amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Bakanina, L.P.; Belonuchkin, V.E.; Kozel, S.M.; Kuznetsov, E.P.; Lokshin, T.R.

    1980-01-01

    A system of equations is derived which describes the laser onset process in a high-gain gas laser amplifier. The intrinsic, amplified spontaneous emission plays the determinate role in the transient processes. The transient processes for a HeFe (3.39 micrometers) laser amplifier are calculated on a computer for three amplifier lengths (40, 80 and 200 centimeters) with the instantaneous onset of inversion.

  5. Comparative evaluation of tungsten inert gas and laser beam ...

    Indian Academy of Sciences (India)

    In this study, the bead-on-plate welds were made on AA5083-H321 alloy plates using both tungsten inert gas (TIG) welding and laser beam (LB) welding processes to study the enhancement of mechanical properties such as weld yield strength and hardness. The low heat input of laser beam welding effectively reduced the ...

  6. Comparative evaluation of tungsten inert gas and laser beam ...

    Indian Academy of Sciences (India)

    Abstract. In this study, the bead-on-plate welds were made on AA5083-H321 alloy plates using both tungsten inert gas (TIG) welding and laser beam (LB) welding pro- cesses to study the enhancement of mechanical properties such as weld yield strength and hardness. The low heat input of laser beam welding effectively ...

  7. Visible and near-ultraviolet spectra of low-pressure rare-gas microwave discharges

    Science.gov (United States)

    Campbell, J. P.; Spisz, E. W.; Bowman, R. L.

    1971-01-01

    The spectral emission characteristics of three commercial low pressure rare gas discharge lamps wire obtained in the near ultraviolet and visible wavelength range. All three lamps show a definite continuum over the entire wavelength range from 0.185 to 0.6 micrometers. Considerable line emission is superimposed on much of the continuum for wavelengths greater than 0.35 micrometers. These sources were used to make transmittance measurements on quartz samples in the near ultraviolet wavelength range.

  8. Enhanced visible-light photocatalysis and gas sensor properties of polythiophene supported tin doped titanium nanocomposite

    Science.gov (United States)

    Chandra, M. Ravi; Siva Prasada Reddy, P.; Rao, T. Siva; Pammi, S. V. N.; Siva Kumar, K.; Vijay Babu, K.; Kiran Kumar, Ch.; Hemalatha, K. P. J.

    2017-06-01

    The polythiophene supported tin doped titanium nanocomposites (PTh/Sn-TiO2) were synthesized by modified sol-gel process through oxidative polymerization of thiophene. The fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectroscopy (UV-DRS) analysis confirms the existence of synergetic interaction between metal oxide and polymer along with extension of absorption edge to visible region. The composites are found to be in spherical form with core-shell structure, which is confirmed by scanning electron spectroscopy (SEM) and transmission electron microscopy (TEM) images, the presence of all respective elements of composite are proven by energy-dispersive X-ray spectroscopy (EDX) analysis. The importance of polythiophene on surface of metal oxide has been were studied as a function of photocatalytic activity for degradation of organic pollutant congo red and gas sensor behavior towards liquid petroleum gas (LPG). All the composites are photocatalytically active and the composite with 1.5 wt% thiophene degrades the pollutant congo red within 120 min when compared to remaining catalysts under visible light irradiation. On the other hand, same composite have shown potential gas sensor properties towards LPG at 300 °C. Considering all the results, it can be noted that polythiophene acts as good sensitizer towards LPG and supporter for the tin doped titania that improve the photocatalytic activity under visible light.

  9. SUPPORTING UAVS IN LOW VISIBILITY CONDITIONS BY MULTIPLE-PULSE LASER SCANNING DEVICES

    Directory of Open Access Journals (Sweden)

    A. Djuricic

    2013-04-01

    Full Text Available Unmanned Aerial Vehicles (UAVs are nowadays promising platforms for capturing spatial information, because they are low cost solutions, which are easy to bring to the surveying field and can operate automatically. Usually these devices are equipped with visual sensors to support the navigation of the platform or to transmit observations of the environment to the operator. By collecting the data and processing the captured images even an estimation of the observed environment in form of 3D information is available. Therefore Simultaneous Localization and Mapping (SLAM algorithms are well known for processing data which is captured in the visible domain. However, situations can occur where gathering visual information is difficult due to given limitations in form of low visibility. For example if soft obstacles in form of translucent materials are given in disaster scenarios with smoke and operating has still to be ensured, active optical sensors (e.g. laser scanners are gaining interest because they can penetrate the soft obstacle and allow to acquire information behind it. A new lightweight (210 g, simplified and minimized scanning unit is now available which allows to capture multiple reflections for each transmitted laser pulse, namely the Hokuyo UTM-30LX-EW. With such a device, it is possible to overcome the above mentioned restrictions or limitations of low visibility by soft obstacles and even measure under critical circumstances. A multi-pulse system can provide accurate measurements on, within, and behind the soft obstacle. This research focuses on investigating the ability and performance of a laser scanner to penetrate the soft obstacle. Thus, investigations on a system that overcomes these limitations and provides a solution will be given. First promising experimental results considering soft obstacle are described.

  10. Electromagnetic radiations from laser interaction with gas-filled Hohlraum

    Science.gov (United States)

    Yang, Ming; Yang, Yongmei; Li, Tingshuai; Yi, Tao; Wang, Chuanke; Liu, Shenye; Jiang, Shaoen; Ding, Yongkun

    2018-01-01

    The emission of intensive electromagnetic pulse (EMP) due to laser-target interactions at the ShenGuang-III laser facility has been evaluated by probes. EMP signals measured using the small discone antennas demonstrated two variation trends including a bilateral oscillation wave and a unilateral oscillation wave. The new trend of unilateral oscillation could be attributed to the hohlraum structure and low-Z gas in the hohlraum. The EMP waveform showed multiple peaks when the gas-filled hohlraum was shot by the high-power laser. Comparing the EMP signals with the verification of stimulated Raman scattering energy and hard x-ray energy spectrum, we found that the intensity of EMP signals decreased with the increase of the hohlraum size. The current results are expected to offer preliminary information to study physical processes on laser injecting gas-filled hohlraums in the National Ignition Facility implementation.

  11. A hybrid CATV/16-QAM-OFDM visible laser light communication system

    International Nuclear Information System (INIS)

    Lin, Chun-Yu; Li, Chung-Yi; Lu, Hai-Han; Chen, Chia-Yi; Jhang, Tai-Wei; Ruan, Sheng-Siang; Wu, Kuan-Hung

    2014-01-01

    A visible laser light communication (VLLC) system employing a vertical cavity surface emitting laser and spatial light modulator with hybrid CATV/16-QAM-OFDM modulating signals over a 5 m free-space link is proposed and demonstrated. With the assistance of a push-pull scheme, low-noise amplifier, and equalizer, good performances of composite second-order and composite triple beat are obtained, accompanied by an acceptable carrier-to-noise ratio performance for a CATV signal, and a low bit error rate value and clear constellation map are achieved for a 16-QAM-OFDM signal. Such a hybrid CATV/16-QAM-OFDM VLLC system would be attractive for providing services including CATV, Internet and telecommunication services. (paper)

  12. Laser ablation of lysozyme with UV, visible and infrared femto- and nanosecond pulses

    DEFF Research Database (Denmark)

    Schou, Jørgen; Canulescu, Stela; Matei, Andreea

    Lysozyme is an interesting molecule for laser ablation of organic materials, because the ablation has been comprehensively studied, it is a medium heavy molecule with a mass of 14305 Da, which can be detected by standard techniques, and because it is used as a bactericidal protein in the food...... industry. Lysozyme molecules do not absorb energy for wavelengths above 310 nm, but nevertheless there is a strong mass loss by ablation for laser irradiation in the visible regime. The total ablation yield of lysozyme at 355 nm and at 2 J/cm2 is about 155 µg/pulse, possibly one of the highest ablation...... yields ever measured. The mass loss is mainly caused by fragmentation of the lysozyme into simple gases, such as H2S, H2O and CO2 , which are rapidly pumped away in the vacuum chamber. We have investigated the mass loss by ablation of lysozyme in all regimes to see whether a similar mechanism governs...

  13. Quantification of UV-Visible and Laser Spectroscopic Techniques for Materials Accountability and Process Control

    International Nuclear Information System (INIS)

    Czerwinski, Kenneth; Weck, Phil

    2013-01-01

    Ultraviolet-visible spectroscopy (UV-Visible) and time-resolved laser fluorescence spectroscopy (TRLFS) optical techniques can permit on-line analysis of actinide elements in a solvent extraction process in real time. These techniques have been used for measuring actinide speciation and concentration under laboratory conditions and are easily adaptable to multiple sampling geometries, such as dip probes, fiber-optic sample cells, and flow-through cell geometries. To fully exploit these techniques, researchers must determine the fundamental speciation of target actinides and the resulting influence on spectroscopic properties. Detection limits, process conditions, and speciation of key actinide components can be established and utilized in a range of areas, particularly those related to materials accountability and process control. Through this project, researchers will develop tools and spectroscopic techniques to evaluate solution extraction conditions and concentrations of U, Pu, and Cm in extraction processes, addressing areas of process control and materials accountability. The team will evaluate UV- Visible and TRLFS for use in solvent extraction-based separations. Ongoing research is examining efficacy of UV-Visible spectroscopy to evaluate uranium and plutonium speciation under conditions found in the UREX process and using TRLFS to evaluate Cm speciation and concentration in the TALSPEAK process. A uranyl and plutonium nitrate UV-Visible spectroscopy study met with success, which supports the utility and continued exploration of spectroscopic methods for evaluation of actinide concentrations and solution conditions for other aspects of the UREX+ solvent extraction scheme. This project will examine U and Pu absorbance in TRUEX and TALSPEAK, perform detailed examination of Cm in TRUEX and TALSPEAK, study U laser fluorescence, and apply project data to contactors. The team will also determine peak ratios as a function of solution concentrations for the UV-Visible

  14. Preformed transient gas channels for laser wakefield particle acceleration

    International Nuclear Information System (INIS)

    Wood, W.M.

    1994-01-01

    Acceleration of electrons by laser-driven plasma wake fields is limited by the range over which a laser pulse can maintain its intensity. This distance is typically given by the Rayleigh range for the focused laser beam, usually on the order of 0.1 mm to 1 mm. For practical particle acceleration, interaction distances on the order of centimeters are required. Therefore, some means of guiding high intensity laser pulses is necessary. Light intensities on the order of a few times 10 17 W/cm 2 are required for laser wakefield acceleration schemes using near IR radiation. Gas densities on the order of or greater than 10 17 cm -3 are also needed. Laser-atom interaction studies in this density and intensity regime are generally limited by the concomitant problems in beam propagation introduced by the creation of a plasma. In addition to the interaction distance limit imposed by the Rayleigh range, defocusing of the high intensity laser pulse further limits the peak intensity which can be achieved. To solve the problem of beam propagation limitations in laser-plasma wakefield experiments, two potential methods for creating transient propagation channels in gaseous targets are investigated. The first involves creation of a charge-neutral channel in a gas by an initial laser pulse, which then is ionized by a second, ultrashort, high-intensity pulse to create a waveguide. The second method involves the ionization of a gas column by an ultrashort pulse; a transient waveguide is formed by the subsequent expansion of the heated plasma into the neutral gas

  15. Selective gas sensing for photonic crystal lasers

    DEFF Research Database (Denmark)

    Smith, Cameron; Christiansen, Mads Brøkner; Buss, Thomas

    2011-01-01

    We facilitate photonic crystal lasers to sense gases via an additional swelling polymer film. We describe the transduction transfer function and experimentally demonstrate an enhanced ethanol vapor sensitivity over 15 dB with low humidity crosstalk.......We facilitate photonic crystal lasers to sense gases via an additional swelling polymer film. We describe the transduction transfer function and experimentally demonstrate an enhanced ethanol vapor sensitivity over 15 dB with low humidity crosstalk....

  16. Smoothing of laser energy deposition by gas jets

    Czech Academy of Sciences Publication Activity Database

    Batani, D.; Benocci, R.; Dezulian, R.; Redaelli, R.; Canova, F.; Stabile, H.; Lucchini, G.; Malka, V.; Fauré, J.; Koenig, M.; Krouský, Eduard; Mašek, Karel; Pfeifer, Miroslav; Skála, Jiří; Dudžák, Roman; Limpouch, J.; Tikhonchuk, V.; Nicolai, P.

    2009-01-01

    Roč. 175, č. 1 (2009), s. 65-70 ISSN 1951-6355 R&D Projects: GA MŠk(CZ) LC528 EU Projects: European Commission(XE) 506350 - LASERLAB-EUROPE Institutional research plan: CEZ:AV0Z10100523 Keywords : laser-generated plasma * laser smoothing technique Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.840, year: 2009

  17. Modeling of diode pumped metastable rare gas lasers.

    Science.gov (United States)

    Yang, Zining; Yu, Guangqi; Wang, Hongyan; Lu, Qisheng; Xu, Xiaojun

    2015-06-01

    As a new kind of optically pumped gaseous lasers, diode pumped metastable rare gas lasers (OPRGLs) show potential in high power operation. In this paper, a multi-level rate equation based model of OPRGL is established. A qualitative agreement between simulation and Rawlins et al.'s experimental result shows the validity of the model. The key parameters' influences and energy distribution characteristics are theoretically studied, which is useful for the optimized design of high efficient OPRGLs.

  18. Laser deposition of sulfonated phthalocyanines for gas sensors

    Czech Academy of Sciences Publication Activity Database

    Fitl, Přemysl; Vrňata, M.; Kopecký, D.; Vlček, J.; Škodová, J.; Bulíř, Jiří; Novotný, Michal; Pokorný, Petr

    2014-01-01

    Roč. 302, MAY (2014), s. 37-41 ISSN 0169-4332. [European-Materials-Research-Society Symposium on Laser Material Interactions for Micro- and Nano- Applications /5./. Strasbourg, 27.05.2013-31.05.2013] R&D Projects: GA ČR(CZ) GAP108/11/1298 Institutional support: RVO:68378271 Keywords : Matrix Assisted Pulsed Laser Evaporation * substituted phthalocyanines * gas sensors * impedance measurements Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.711, year: 2014

  19. Laser-Irradiated Gas Puff Target Plasma Modeling

    Czech Academy of Sciences Publication Activity Database

    Vrba, Pavel; Vrbová, M.

    2014-01-01

    Roč. 42, č. 10 (2014), s. 2600-2601 ISSN 0093-3813 R&D Projects: GA ČR GAP102/12/2043 Grant - others:GA MŠk(CZ) CZ.1.07/2.3.00/20.0092 Institutional support: RVO:61389021 Keywords : Gas puff laser plasma * water window radiation source * RHMD code Z* Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.101, year: 2014 http://ieeexplore.ieee.org

  20. Gas laser tube and method of fabricating same

    International Nuclear Information System (INIS)

    Garman, L.E.

    1975-01-01

    An improved gas laser tube is fabricated by counter boring the ends of a tubular aluminum extrusion having an inner tubular portion supported from an outer tubular portion via the intermediary of a plurality of radially directed support vanes or legs. Metallic transverse walls are sealed across the ends of the tubular extrusion to define the ends of a gas tight metallic envelope. An electrically insulative glow discharge tube is axially disposed within and supported by the inner tubular portion of the extrusion in axial alignment with an optical resonator of the laser tube. (U.S.)

  1. Mechanism behind dry etching of Si assisted by pulsed visible laser

    Science.gov (United States)

    Peck, Jason A.; Ruzic, David N.

    2017-11-01

    Poly-Si films were etched using a 13.56 MHz capacitively coupled plasma source while simultaneously being exposed to a pulsed Nd:YAG laser using 266 and 532 nm lines, with Gaussian pulse durations of 100 Hz and 7 ns. For a fluorocarbon etch recipe of 50:8 sccm Ar:C4F8 with varying O2, a minimum laser intensity for the etch onset was necessary to overcome CFx polymer deposition. This etch onset occurred at 6 ± 1 mJ/cm2/pulse; beyond this onset, the etch rate increased linearly with laser intensity. Null results of laser etch enhancement using continuous wave diode sources demonstrated the necessity of the instantaneous application of the pulsed Nd:YAG source. To determine the mechanism of laser etch enhancement at 532 nm, highly doped Si samples were tested, with varying optical absorption depths while keeping the photon energy constant. It was shown that at phosphorus contents of 1019 cm-3 and 1021 cm-3, 532 nm etch enhancement trends were 1.7× and 3.7× higher than those on intrinsic Si, showing that instantaneous surface heating was key in desorbing involatile etch products. Further investigation of the surface fluorine content via X-ray photon spectroscopy showed that distinct desorption stages occurred for increasing pulse energy—trends which aligned very well with SiFx desorption promoted by steady-state wafer heating. Gas arrival/surface saturation experiments with varying pressures and pulse rates showed that, in straightforward etching discharges such as Ar/SF6, laser removal per pulse plateaus when the pulse rate is lower than the rate of surface saturation, while in fluorocarbon-rich etch chemistries such as Ar/C4F8/O2 mixtures, a minimum pulse rate must be maintained to overcome the CFx polymer layer being deposited.

  2. The influence of shielding gas in hybrid LASER MIG welding

    Science.gov (United States)

    Tani, Giovanni; Campana, Giampaolo; Fortunato, Alessandro; Ascari, Alessandro

    2007-07-01

    Hybrid LASER-GMAW welding technique has been recently studied and developed in order to meet the needs of modern welding industries. The two sources involved in this process play, in fact, a complementary role: fast welding speed, deep bead penetration and high energy concentration can be achieved through the LASER beam, while gap bridgeability and cost-effectiveness are typical of the GMAW process. Particularly interesting, in this context, is the CO 2 LASER-MIG welding which differs from the Nd:YAG LASER-MIG technique for the high powers that can be exploited and for the good power/cost ratio of the process. This paper is a part of a wide study on the hybrid CO 2 LASER-MIG welding and investigates the influence of the shielding gas both on the stability of the process and on the dimensional characteristics of the weld bead. Two different parameters have been taken into consideration in order to develop this analysis: the shielding gas composition and the shielding gas flow. The experiment, performed on AISI 304 stainless steel plates, has been planned exploiting design of experiment techniques. The results have been analyzed through a statistical approach in order to determine the real influence of each parameter on the overall process.

  3. Melt flow characteristics in gas-assisted laser cutting

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. We present a study on laser cutting of mild steel with oxygen as an assist gas. We correlate the cut surface quality with the melt film thickness. We estimate the optimum pressure required for melt ejection under laminar flow regime. The thickness of melt film inside the kerf is estimated using mass balance and the ...

  4. Melt flow characteristics in gas-assisted laser cutting

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    email: trao@cat.ernet.in. MS received 24 May 2001; revised 28 December 2001. Abstract. We present a study on laser cutting of mild steel with oxygen as an assist gas. We correlate the cut surface quality with the melt film thickness. We estimate the optimum pressure required for melt ejection under laminar flow regime.

  5. Theory of porous wall capillary tubes for flowing gas lasers

    International Nuclear Information System (INIS)

    Papayoanou, A.; Fujisawa, A.

    1975-01-01

    Flowing gas capillary lasers exhibit high optical gains. However, as a result of the linear axial pressure variation in the tube bore, gain and saturation intensities are not axially uniform. This pressure variation can be reduced by introducing the gas into the tube bore through the walls of a porous capillary tube. Analysis of the gas flow shows that the axial pressure variation in the porous wall tubes is more gradual than for dense wall tubes leading to more uniform gain conditions. The saturation intensity is more uniform not only due to the reduced pressure anisotropy but also, at higher flow rates, because of axially varying particle dwell times in the discharge region

  6. Simple locking of infrared and ultraviolet diode lasers to a visible laser using a LabVIEW proportional-integral-derivative controller on a Fabry-Perot signal.

    Science.gov (United States)

    Kwolek, J M; Wells, J E; Goodman, D S; Smith, W W

    2016-05-01

    Simultaneous laser locking of infrared (IR) and ultraviolet lasers to a visible stabilized reference laser is demonstrated via a Fabry-Perot (FP) cavity. LabVIEW is used to analyze the input, and an internal proportional-integral-derivative algorithm converts the FP signal to an analog locking feedback signal. The locking program stabilized both lasers to a long term stability of better than 9 MHz, with a custom-built IR laser undergoing significant improvement in frequency stabilization. The results of this study demonstrate the viability of a simple, computer-controlled, non-temperature-stabilized FP locking scheme for our applications, laser cooling of Ca(+) ions, and its use in other applications with similar modest frequency stabilization requirements.

  7. Visible to Infrared Diamond Photonics Enabled by Focused Femtosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Belén Sotillo

    2017-02-01

    Full Text Available Diamond’s nitrogen-vacancy (NV centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and because they can be found, manipulated, and read out optically. An important step forward for diamond photonics would be connecting multiple diamond NVs together using optical waveguides. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work, we show the fabrication of optical waveguides in diamond, enabled by focused femtosecond high repetition rate laser pulses. By optimizing the geometry of the waveguide, we obtain single mode waveguides from the visible to the infrared. Additionally, we show the laser writing of individual NV centers within the bulk of diamond. We use µ-Raman spectroscopy to gain better insight on the stress and the refractive index profile of the optical waveguides. Using optically detected magnetic resonance and confocal photoluminescence characterization, high quality NV properties are observed in waveguides formed in various grades of diamond, making them promising for applications such as magnetometry, quantum information systems, and evanescent field sensors.

  8. Barely visible 10-millisecond pascal laser photocoagulation for diabetic macular edema: observations of clinical effect and burn localization.

    Science.gov (United States)

    Muqit, Mahiul M K; Gray, Jane C B; Marcellino, George R; Henson, David B; Young, Lorna B; Patton, Niall; Charles, Stephen J; Turner, George S; Stanga, Paulo E

    2010-06-01

    To investigate the morphologic features and clinical efficacy of barely visible Pascal (Optimedica Corporation) photocoagulation burns in diabetic macular edema (DME) using Fourier-domain optical coherence tomography (FD OCT) and fundus autofluorescence (AF). Interventional case series. Retrospective evaluation of 10 eyes with newly diagnosed DME that underwent barely visible Pascal photocoagulation using an array of 10-microm, 10-millisecond photocoagulation burns. FD OCT and camera-based AF was performed at baseline and at 1 hour, 2 weeks, 4 weeks, and 12 weeks after laser. Changes in retinal thickening after laser treatment were measured using retinal thickness maps within the treated sector and the central foveal subfield. At 1 hour after treatment, burns were visualized partially with clinical biomicroscopy. AF demonstrated spots lacking autofluorescence that confirmed effective laser uptake within the Pascal arrays. Sequential changes in hyperreflectivity on FD OCT correlated with morphologic alterations seen on AF. Burns became increasingly hyperautofluorescent between 2 and 4 weeks. There were significant reductions in the retinal thickness within treated sectors on FD OCT at 2 weeks (26 +/- 32 microm; P = .012) and 3 months after laser (20 +/- 21 microm; P = .02) compared with baseline. Clinical biomicroscopic reduction of DME was the most common finding in 80%. Barely visible 10-millisecond Pascal laser seems to produce an effect at the level of the inner and outer photoreceptor segments and apical retinal pigment epithelium, with minimal axial and lateral spread of burns. FD OCT confirmed spatial localization of AF signal changes that correlated with laser burn-tissue interactions over 3 months. The technique of lower-fluence barely visible 10-millisecond laser may reduce retinal edema within affected sectors and effectively treat DME with minimization of scar formation. Copyright 2010 Elsevier Inc. All rights reserved.

  9. Modelling and interpretation of gas detection using remote laser pointers.

    Science.gov (United States)

    Hodgkinson, J; van Well, B; Padgett, M; Pride, R D

    2006-04-01

    We have developed a quantitative model of the performance of laser pointer style gas leak detectors, which are based on remote detection of backscattered radiation. The model incorporates instrumental noise limits, the reflectivity of the target background surface and a mathematical description of gas leak dispersion in constant wind speed and turbulence conditions. We have investigated optimum instrument performance and limits of detection in simulated leak detection situations. We predict that the optimum height for instruments is at eye level or above, giving an operating range of 10 m or more for most background surfaces, in wind speeds of up to 2.5 ms(-1). For ground based leak sources, we find laser pointer measurements are dominated by gas concentrations over a short distance close to the target surface, making their readings intuitive to end users in most cases. This finding is consistent with the results of field trials.

  10. 4 Gbps direct modulation of 450 nm GaN laser for high-speed visible light communication.

    Science.gov (United States)

    Lee, Changmin; Zhang, Chong; Cantore, Michael; Farrell, Robert M; Oh, Sang Ho; Margalith, Tal; Speck, James S; Nakamura, Shuji; Bowers, John E; DenBaars, Steven P

    2015-06-15

    We demonstrate high-speed data transmission with a commercial high power GaN laser diode at 450 nm. 2.6 GHz bandwidth was achieved at an injection current of 500 mA using a high-speed visible light communication setup. Record high 4 Gbps free-space data transmission rate was achieved at room temperature.

  11. 4 Gbps direct modulation of 450 nm GaN laser for high-speed visible light communication

    KAUST Repository

    Lee, Changmin

    2015-06-10

    We demonstrate high-speed data transmission with a commercial high power GaN laser diode at 450 nm. 2.6 GHz bandwidth was achieved at an injection current of 500 mA using a high-speed visible light communication setup. Record high 4 Gbps free-space data transmission rate was achieved at room temperature.

  12. Visibility impacts at class i areas near the bakken oil and gas development.

    Science.gov (United States)

    Gebhart, Kristi A; Day, Derek E; Prenni, Anthony J; Schichtel, Bret A; Hand, J L; Evanoski-Cole, Ashley R

    2018-02-12

    Oil and gas activities have occurred in the Bakken region of North Dakota and nearby states and provinces since the 1950s but began increasing rapidly around 2008 due to new extraction methods. Three receptor-based techniques were used to examine the potential impacts of oil and gas extraction activities on airborne particulate concentrations in Class I areas in and around the Bakken. This work was based on long-term measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network. Spatial and temporal patterns in measured concentrations were examined before and after 2008 to better characterize the influence of these activities. A multisite back trajectory analysis and a receptor-based source-apportionment model were used to estimate impacts. Findings suggest that recent Bakken oil and gas activity has led to an increase in regional fine (PM 2.5 -particles with aerodynamic diameters visibility at protected sites in the region. However, the impact has been at least partially offset by a concurrent reduction in emissions from coal fired electric generating stations. Continuing the recent reductions in flaring would likely be beneficial for the regional visual air quality.

  13. All-Solid-State Drivers for High Power Excimer Lasers Used in Projection Gas Immersion Laser Doping

    National Research Council Canada - National Science Library

    Jacob, Jonah

    2001-01-01

    The objective of this SBIR program is to develop all-solid-state pulsed modulators to drive the high power excimer lasers required to commercialize the Projection Gas Immersion Laser Doping (P-GILD) process...

  14. Splash plasma channels produced by picosecond laser pulses in argon gas for laser wakefield acceleration

    Directory of Open Access Journals (Sweden)

    Y. Mizuta

    2012-12-01

    Full Text Available Short-lived, ∼10  ps, deep plasma channels, with their lengths of ∼1  mm and diameters of ∼20  μm, are observed and characterized in Ar gas jets irradiated by moderate intensity, ∼10^{15–16}  W/cm^{2}, laser pulses with a duration from subpicosecond to several picoseconds. The channels, upon 2D particle-in-cell simulations including ionization, fit well in the guiding of high intensity femtosecond laser pulses and, therefore, in laser wakefield acceleration with a controllable electron self-injection.

  15. Subcycle engineering of laser filamentation in gas by harmonic seeding

    Science.gov (United States)

    Béjot, P.; Karras, G.; Billard, F.; Doussot, J.; Hertz, E.; Lavorel, B.; Faucher, O.

    2015-11-01

    Manipulating at will the propagation dynamics of high power laser pulses is a long-standing dream whose accomplishment would lead to the control of fascinating physical phenomena emerging from laser-matter interaction. The present work represents a significant step towards such a control by manipulating the nonlinear optical response of the gas medium. This is accomplished by shaping an intense laser pulse experiencing filamentation at the subcycle level with a relatively weak (≃1 % ) third-harmonic radiation. The control results from quantum interference between a single- and a two-color (mixing the fundamental frequency with its third-harmonic) ionization channel. This mechanism, which depends on the relative phase between the two electric fields, is responsible for wide refractive index modifications in relation with significant enhancement or suppression of the ionization rate. As a first application, we demonstrate the production and control of an axially modulated plasma channel.

  16. Predicting gas decomposition in an industrialized pulsed CO2 laser

    CSIR Research Space (South Africa)

    Forbes, A

    2005-03-01

    Full Text Available , and then test this against experimental data. This is because rate laws must be determined from measurements of reaction rates, and cannot be deduced from reaction stoichiometry. The reader is refered to standard physical chemistry texts5 for further... if kd is not gas species dependent. 3. CATALYSTS PRESENT With catalysts present in the laser, the oxygen concentration stabilise quickly and at lower levels than in the case of no catalysts. Using the model already found for the discharge chemistry...

  17. Electrical and optical properties of thin indium tin oxide films produced by pulsed laser ablation in oxygen or rare gas atmospheres

    DEFF Research Database (Denmark)

    Thestrup, B.; Schou, Jørgen; Nordskov, A.

    1999-01-01

    Films of indium tin oxide (ITO) have been produced in different background gases by pulsed laser deposition (PLD). The Films deposited in rare gas atmospheres on room temperature substrates were metallic, electrically conductive, but had poor transmission of visible light. For substrate temperatu......Films of indium tin oxide (ITO) have been produced in different background gases by pulsed laser deposition (PLD). The Films deposited in rare gas atmospheres on room temperature substrates were metallic, electrically conductive, but had poor transmission of visible light. For substrate...... temperatures at 200 degrees C, the specific resistivity was reduced and the transmission of visible light enhanced for all background gases. Films produced in oxygen turned out to be superior to films deposited in other gases at the same temperature. (C) 1999 Elsevier Science B.V. All rights reserved....

  18. Efficiency of laser beam utilization in gas laser cutting of materials

    Science.gov (United States)

    Galushkin, M. G.; Grishaev, R. V.

    2018-02-01

    Relying on the condition of dynamic matching of the process parameters in gas laser cutting, the dependence of the beam utilization factor on the cutting speed and the beam power has been determined. An energy balance equation has been derived for a wide range of cutting speed values.

  19. Laser Doppler detection systems for gas velocity measurement.

    Science.gov (United States)

    Huffaker, R M

    1970-05-01

    The velocity of gas flow has been remotely measured using a technique which involves the coherent detection of scattered laser radiation from small particles suspended in the fluid utilizing the doppler effect. Suitable instrumentation for the study of wind tunnel type and atmospheric flows are described. Mainly for reasons of spatial resolution, a function of the laser wavelength, the wind tunnel system utilizes an argon laser operating at 0.5 micro. The relaxed spatial resolution requirement of atmospheric applications allows the use of a carbon dioxide laser, which has superior performance at a wavelength of 10.6 micro, a deduction made from signal-to-noise ratio considerations. Theoretical design considerations are given which consider Mie scattering predictions, two-phase flow effects, photomixing fundamentals, laser selection, spatial resolution, and spectral broadening effects. Preliminary experimental investigations using the instrumentation are detailed. The velocity profile of the flow field generated by a 1.27-cm diam subsonic jet was investigated, and the result compared favorably with a hot wire investigation conducted in the same jet. Measurements of wind velocity at a range of 50 m have also shown the considerable promise of the atmospheric system.

  20. Laser Acceleration of Electrons in Shock Wave Enhanced Gas Jets

    Science.gov (United States)

    Kaganovich, Dmitri; Helle, Michael; Gordon, Daniel; Ting, Antonio

    2012-10-01

    Controlling the gas density gradient and profile is important for electron and proton acceleration. Using an optimized gas density profile, we have demonstrated 40 times higher electron energy compared to a Gaussian gas jet without lost of charge or stability. Propagation of a shock wave through a gas jet can modify the gas density profile and create sharp density gradients [1, 2]. Using different shock waves energies and shock originating positions, we were able to modify the plasma density profile of a ``typical'' Gaussian gas jet into a variety of profiles, from thin (foil-like) structure to elongated profiles with fast rise and slow fall. We used a plasma bubble Cherenkov diagnostic [3, 4] to optimize the acceleration process. Accelerated electron energy and charge were cross-correlated with the second harmonic diagnostic signal. The optimized gas density profile generated stable 0.5 nC of 40 MeV electrons using a 10 TW laser. The shock wave modified gas jet can be used as a stand alone electron source or as an injector coupled to additional acceleration structures. We demonstrated stable injection of electrons from the shock wave modified gas jet into a lower density plasma. The results are also being studied with numerical simulations. [4pt] [1] D. Kaganovich et al., Physics of Plasmas 18, 120701 (2011)[0pt] [2] D. Kaganovich et al., Applied Physics Letters 97, 191501 (2010)[0pt] [3] D. F. Gordon, et al., Phys. Rev. Lett. 101, 045004 (2008)[0pt] [4] M. H. Helle et al., Phys. Rev. Lett. 105, 105001 (2010)

  1. Attosecond pulse trains from long laser-gas interaction targets

    International Nuclear Information System (INIS)

    Hauri, C.P.; Lopez-Martens, R.; Varju, K.; Ruchon, T.; Gustafsson, E.; L'Huillier, A.

    2006-01-01

    Complete test of publication follows. Many experiments in attosecond physics require high XUV photon flux as well as a clean attosecond pulse train (APT) temporal structure. Temporal characterization of high-order harmonic generation (HHG) in long interaction targets is thus of high interest. HHG being a very inefficient process, a large effort has been made to increase the amount of XUV photons emitted per infrared laser pulse. Besides quasi phase-matching in a modulated capillary, loose driving laser focusing conditions and subsequent self-channeling have shown to significantly increase the conversion efficiency. We characterized the temporal structure of APTs generated during the self-channeling of an intense IR driving laser pulse. Our first results indicate, however, that the temporal structure of the APT generated during the HHG process might be affected by quantum path interference and spectral phase distortion due to the self-channeling process itself. In particular, our measurements show that the relative spectral phase between consecutive harmonics can strongly vary depending on the target length and the position of the laser focus with respect to the target. In general for short gas targets, no clean APT structure can be expected since the individual attosecond pulses carry significant chirp. For longer targets, however, we observe a flattening of the harmonic spectral phase, resulting in near-transform-limited attosecond pulse trains. A complete analysis of the process is complex and involves detailed knowledge of the spatial and temporal evolution of the self-channeling driver laser pulse throughout the gas target.

  2. Two-step laser ionization schemes for in-gas laser ionization and spectroscopy of radioactive isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Kudryavtsev, Yu., E-mail: yuri.kudryavtsev@fys.kuleuven.be; Ferrer, R.; Huyse, M.; Van den Bergh, P.; Van Duppen, P. [Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven (Belgium); Vermeeren, L. [SCK-CEN, Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium)

    2014-02-15

    The in-gas laser ionization and spectroscopy technique has been developed at the Leuven isotope separator on-line facility for the production and in-source laser spectroscopy studies of short-lived radioactive isotopes. In this article, results from a study to identify efficient optical schemes for the two-step resonance laser ionization of 18 elements are presented.

  3. Two-step laser ionization schemes for in-gas laser ionization and spectroscopy of radioactive isotopes.

    Science.gov (United States)

    Kudryavtsev, Yu; Ferrer, R; Huyse, M; Van den Bergh, P; Van Duppen, P; Vermeeren, L

    2014-02-01

    The in-gas laser ionization and spectroscopy technique has been developed at the Leuven isotope separator on-line facility for the production and in-source laser spectroscopy studies of short-lived radioactive isotopes. In this article, results from a study to identify efficient optical schemes for the two-step resonance laser ionization of 18 elements are presented.

  4. Fragmentation of neutral van der Waals clusters with visible laser light: A new variant of the Raman effect?

    International Nuclear Information System (INIS)

    Stamatovic, A.; Howorka, F.; Scheier, P.; Maerk, T.D.

    1989-01-01

    We have observed strong photodissociation (using visible laser light) of neutral van der Waals clusters (Ar, N 2 , O 2 , CO 2 , SO 2 , NH 3 ) produced by supersonic expansion and detected by electron ionization/mass spectrometer. Several tests were performed, all of them supporting this surprising discovery. We suggest that Raman induced photodissociation (RIP) is responsible for this phenomenon. This first observation of Raman induced photodissociation provides a new technique for the study of neutral van der Waals clusters. (orig.)

  5. Development and Quantification of UV-Visible and Laser Spectroscopic Techniques for Materials Accountability and Process Control

    International Nuclear Information System (INIS)

    Czerwinski, Ken; Weck, Phil; Poineau, Frederic

    2010-01-01

    Ultraviolet-Visible Spectroscopy (UV-Visible) and Time Resolved Laser Fluorescence Spectroscopy (TRLFS) optical techniques can permit on-line, real-time analysis of the actinide elements in a solvent extraction process. UV-Visible and TRLFS techniques have been used for measuring the speciation and concentration of the actinides under laboratory conditions. These methods are easily adaptable to multiple sampling geometries, such as dip probes, fiber-optic sample cells, and flow-through cell geometries. To fully exploit these techniques for GNEP applications, the fundamental speciation of the target actinides and the resulting influence on 3 spectroscopic properties must be determined. Through this effort detection limits, process conditions, and speciation of key actinide components can be establish and utilized in a range of areas of interest to GNEP, especially in areas related to materials accountability and process control.

  6. Resolving fringe ambiguities of a wide-field Michelson interferometer using visibility measurements of a noncollimated laser beam.

    Science.gov (United States)

    Wan, Xiaoke; Wang, Ji; Ge, Jian

    2009-09-10

    An actively stabilized interferometer with a constant optical path difference is a key element in long-term astronomical observation, and resolving interference fringe ambiguities is important to produce high-precision results for the long term. We report a simple and reliable method of resolving fringe ambiguities of a wide-field Michelson interferometer by measuring the interference visibility of a noncollimated single-frequency laser beam. Theoretical analysis shows that the interference visibility is sensitive to a subfringe phase shift, and a wide range of beam arrangements is suitable for real implementation. In an experimental demonstration, a Michelson interferometer has an optical path difference of 7 mm and a converging monitoring beam has a numerical aperture of 0.045 with an incidental angle of 17 degrees. The resolution of visibility measurements corresponds to approximately 1/16 fringe in the interferometer phase shift. The fringe ambiguity-free region is extended over a range of approximately 100 fringes.

  7. Investigation of silver-only and silver/TOPAS coated hollow glass waveguides for visible and NIR laser delivery

    Science.gov (United States)

    Melzer, Jeffrey E.; Harrington, James A.

    2015-03-01

    Hollow Glass Waveguides (HGWs) present a viable option for the low-loss transmission of radiation over a broad range spanning from visible to far-infrared wavelengths. Cyclic Olefin Copolymer (COC), a commercially available polymer known as TOPAS®, is chosen for this study due to its exceptionally low absorption losses throughout the spectrum, particularly in the visible and near-infrared (NIR) regions. While silver-coated HGWs are capable of transmitting visible and NIR radiation with low losses, theory predicts that the addition of a uniform dielectric thin film of quarter wavelength thickness will reduce these losses for both straight and bent configurations, while additionally providing a potentially more desirable modal output for laser applications. In this paper, the procedures for the deposition of the silver and subsequent COC films are outlined. Spectroscopy is used to obtain the thickness of the polymer film. The theoretical attenuation losses of the silver and Ag/COC HGWs are explored and experimental values are obtained using various visible and IR lasers. Moreover, the modal output of the silver and Ag/COC HGWs is qualitatively compared. The possibility of use of these Ag/COC HGWs at mid- and far-IR wavelengths is discussed.

  8. Molecular beam epitaxy growth and characterization of two-six materials for visible semiconductor lasers

    Science.gov (United States)

    Zeng, Linfei

    This thesis proposes the molecular beam epitaxy (MBE) growth and characterization of a new Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se based semiconductor materials system on InP substrates for visible light emitting diodes (LED) and lasers. The growth conditions for lattice-matched Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se layers with the desired bandgap have been established and optimized. A chemical etching technique to measure the defect density of Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se materials has been established. The accuracy of this method for revealing stacking faults and dislocations was verified by plan-view TEM. Using the techniques such as III-V buffer layer, Zn-irradiation, low-temperature growth, ZnCdSe interfacial layer and growth interruption to improve the quality of the interface of III-V and II-VI, the material quality of Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se has been improved dramatically. Defect density has been reduced from 10sp{10}\\ cmsp{-2} to {˜}5×10sp4\\ cmsp{-2}. The properties of this material system such as the quality and strain state in the epilayer, the dependence of bandgap on temperature, and the band offset have been studied by using double crystal x-ray diffraction, photoluminescence and capacitance voltage measurements. The ZnCdSe/ZnCdMgSe based quantum well (QW) structures have been grown and studied. Optically pumped lasing with emission range from red to blue has been obtained from ZnCdSe/ZnCdMgSe based separate-confinement single QW laser structures. The results demonstrate the potential for these materials as integrated full color display devices. Preliminary studies of the degradation behavior of ZnCdSe/ZnCdMgSe QW were performed. No dark line defects (DLDs) were observed during the degradation. A very strong room temperature differential negative resistance behavior was observed from Al/Znsb{0.61}Cdsb{0.39}Se/nsp+-InP devices, which is useful in millimeter-wave applications. We also found that these devices can be set to either in highly conductive or

  9. Visible laser and superluminescent diode based free space and underwater communications

    KAUST Repository

    Ooi, Boon S.

    2017-01-30

    We report on our recent progress in high-modulation-efficiency, InGaN-based integrated waveguide modulator-laser diodes (IWM-LDs), high-speed violet and blue emitting superluminescent diodes (SLDs), InGaN-based vertical-cavity surface-emitting lasers (VCSELs), and their applications for gigahertz laser based free-space and underwater wireless optical communications.

  10. Visible Photodissociation Spectra of the 1-METHYL and 2-METHYLNAPHTHALENE Cations: Laser Spectroscopy and Theoretical Simulations

    Science.gov (United States)

    Friha, Hela; Feraud, Geraldine; Falvo, Cyril; Parneix, Pascal; Pino, Thomas; Brechignac, Philippe; Troy, Tyler; Schmidt, Timothy; Dhaouadi, Zoubeida

    2014-06-01

    Naphthalene (Np) and its methylated derivatives (1-Me-Np and 2-Me-Np) are prototype molecules for spectroscopists as first members of the polycyclic aromatic hydrocarbons (PAHs) family. High resolution studies are capable to explore the details of the internal rotation of the methyl group. Although this was achieved in neutral PAHs, the task is not the same in cations. Me-Np cations have been probed by resonance-enhanced multiphoton dissociation, showing only very broad and unresolved spectra, while absorption in argon matrix revealed more resolved vibronic bands. The electronic absorption gas phase spectra of 1-Me-Np^+ and 2-Me-Np^+ were measured using an Ar-tagging technique. In both cases, a band system was observed in the visible range and assigned to the D_2← D_0 transition. The 1-Me-Np^+ absorption bands revealed a red shift of 808 cm-1, relative to Np^+ (14 906 cm-1), while for 2-Me-Np^+ a blue shift of 226 cm-1 was found. A short vibrational progression was also observed. Moreover, insights into the internal rotation motion of the CH_3 were inferred, although intrinsic broadening due to intramolecular relaxation was present. These measurements were supported by detailed quantum chemical calculations that allowed exploration of the potential energy curves, along with a complete simulation of the harmonic FC factors using the cumulant Gaussian fluctuations formalism, extended to include the internal rotation. see for instance Baba et al, J.Phys.Chem.A, 2009, 113, 2366 Dunbar et al, J. Am. Chem. Soc. 1976, 98, 7994-7999; J.Phys.Chem. 1985, 89, 3617 Andrews et al, J.Phys.Chem. 1982, 86, 2916 Pino et al, J. Chem. Phys. 1999, 111, 7337-7347

  11. Development and optimization of a "water window" microscope based on a gas-puff target laser-produced plasma source

    Science.gov (United States)

    Torrisi, Alfio; Wachulak, Przemyslaw; Bartnik, Andrzej; Węgrzyński, Łukasz; Fok, Tomasz; Fiedorowicz, Henryk

    2018-01-01

    A laser-plasma double stream gas-puff target source coupled with Fresnel zone plate (FZP) optics, operating at He-like nitrogen spectral line λ=2.88nm, is capable of acquire complementary information in respect to optical and electron microscopy, allowing to obtain high resolution imaging, compared to the traditional visible light microscopes, with an exposition time of a few seconds. The compact size and versatility of the microscope offers the possibility to perform imaging experiments in the university laboratories, previously restricted to large-scale photon facilities. Source and microscope optimization, and examples of applications will be presented and discussed.

  12. Construction of a Visible Diode Laser Source for Free Radical Photochemistry and Spectroscopy Experiments

    Science.gov (United States)

    Newman, Bronjelyn; Halpern, Joshua B.

    1997-01-01

    Tunable diode lasers are reliable sources of narrow-band light and comparatively cheap. Optical feedback simplifies frequency tuning of the laser diodes. We are building an inexpensive diode laser system incorporating optical feedback from a diffraction grating. The external optical cavity can be used with lasers that emit between 2 and 100 mW, and will also work if they are pulsed, although this will significantly degrade the bandwidth. The diode laser output power and bandwidth are comparable to CW dye lasers used in kinetics and dynamics experiments. However, their cost and maintenance will be much less as will alignment time. We intend to use the diode lasers to investigate CN and C2 kinetics as well as to study dissociation dynamics of atmospherically important molecules.

  13. On the Gas Dynamics of Inert-Gas-Assisted Laser Cutting of Steel Plate

    Science.gov (United States)

    Brandt, A. D.; Settles, G. S.; Scroggs, S. D.

    1996-11-01

    Laser beam cutting of sheet metal requires an assist gas to blow away the molten material. Since the assist-gas dynamics influences the quality and speed of the cut, the orientation of the gas nozzle with respect to the kerf is also expected to be important. A 1 kW cw CO2 laser with nitrogen assist gas was used to cut mild steel sheet of 1 to 4 mm thickness, using a sonic coaxial nozzle as a baseline. Off-axis nozzles were oriented from 20 deg to 60 deg from normal with exit Mach numbers from 1 to 2.4. Results showed maximum cutting speed at a 40 deg nozzle orientation. Shadowgrams of a geometrically-similar model kerf then revealed a separated shock wave-boundary layer interaction within the kerf for the (untilted) coaxial nozzle case. This was alleviated, resulting in a uniform supersonic flow throughout the kerf and consequent higher cutting speeds, by tilting the nozzle between 20 deg and 45 deg from the normal. This result did not depend upon the exit Mach number of the nozzle. (Research supported by NSF Grant DMI-9400119.)

  14. Open Path Trace Gas Laser Sensors for UAV Deployment

    Science.gov (United States)

    Shadman, S.; Mchale, L.; Rose, C.; Yalin, A.

    2015-12-01

    Novel trace gas sensors based on open-path Cavity Ring-down Spectroscopy (CRDS) are being developed to enable remote and mobile deployments including on small unmanned aerial systems (UAS). Relative to established closed-path CRDS instruments, the use of open-path configurations allows removal of the bulky and power hungry vacuum and flow system, potentially enabling lightweight and low power instruments with high sensitivity. However, open path operation introduces new challenges including the need to maintain mirror cleanliness, mitigation of particle optical effects, and the need to measure spectral features that are relatively broad. The present submission details open-path CRDS instruments for ammonia and methane and their planned use in UAS studies. The ammonia sensor uses a quantum cascade laser at 10.3 mm in a configuration in which the laser frequency is continuously swept and a trigger circuit and acousto-optic modulator (AOM) extinguish the light when the laser is resonant with the cavity. Ring-down signals are measured with a two-stage thermoelectrically cooled MCT photodetector. The cavity mirrors have reflectivity of 0.9995 and a noise equivalent absorption of 1.5 ppb Hz-1/2 was demonstrated. A first version of the methane sensor operated at 1.7um with a telecom diode laser while the current version operates at 3.6 um with an interband cascade laser (stronger absorption). We have performed validation measurements against known standards for both sensors. Compact optical assemblies are being developed for UAS deployment. For example, the methane sensor head will have target mass of designed for sensor control and signal processing with target mass <1 kg and power draw <10 W. The sensor size and power parameters are suitable for UAS deployment on both fixed wing and rotor style UAS. We plan to deploy the methane sensor to measure leakage and emission of methane from natural gas infrastructure, and to deploy both sensors together to study emissions from

  15. Semipolar InGaN quantum-well laser diode with integrated amplifier for visible light communications

    KAUST Repository

    Shen, Chao

    2018-02-14

    GaN-based semiconductor optical amplifier (SOA) and its integration with laser diode (LD) is an essential building block yet to be demonstrated for III-nitride photonic integrated circuits (PICs) at visible wavelength. This paper presents the InGaN/GaN quantum well (QW) based dual-section LD consisting of integrated amplifier and laser gain regions fabricated on a semipolar GaN substrate. The threshold current in the laser gain region was favorably reduced from 229mA to 135mA at SOA driving voltages, VSOA, of 0V and 6.25V, respectively. The amplification effect was measured based on a large gain of 5.7 dB at VSOA = 6.25V from the increased optical output power of 8.2 mW to 30.5 mW. Such integrated amplifier can be modulated to achieve Gbps data communication using on-off keying technique. The monolithically integrated amplifier-LD paves the way towards the III-nitride on-chip photonic system, providing a compact, low-cost, and multi-functional solution for applications such as smart lighting and visible light communications.

  16. Calibrating Laser Gas Measurements by Use of Natural CO2

    Science.gov (United States)

    Webster, Chris

    2003-01-01

    An improved method of calibration has been devised for instruments that utilize tunable lasers to measure the absorption spectra of atmospheric gases in order to determine the relative abundances of the gases. In this method, CO2 in the atmosphere is used as a natural calibration standard. Unlike in one prior calibration method, it is not necessary to perform calibration measurements in advance of use of the instrument and to risk deterioration of accuracy with time during use. Unlike in another prior calibration method, it is not necessary to include a calibration gas standard (and the attendant additional hardware) in the instrument and to interrupt the acquisition of atmospheric data to perform calibration measurements. In the operation of an instrument of this type, the beam from a tunable diode laser or a tunable quantum-cascade laser is directed along a path through the atmosphere, the laser is made to scan in wavelength over an infrared spectral region that contains one or two absorption spectral lines of a gas of interest, and the transmission (and, thereby, the absorption) of the beam is measured. The concentration of the gas of interest can then be calculated from the observed depth of the absorption line(s), given the temperature, pressure, and path length. CO2 is nearly ideal as a natural calibration gas for the following reasons: CO2 has numerous rotation/vibration infrared spectral lines, many of which are near absorption lines of other gases. The concentration of CO2 relative to the concentrations of the major constituents of the atmosphere is well known and varies slowly and by a small enough amount to be considered constant for calibration in the present context. Hence, absorption-spectral measurements of the concentrations of gases of interest can be normalized to the concentrations of CO2. Because at least one CO2 calibration line is present in every spectral scan of the laser during absorption measurements, the atmospheric CO2 serves

  17. On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; Brumfield, B. E.; Phillips, M. C.; Miloshevsky, G.

    2017-06-01

    Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early times of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are separated in

  18. Intensity dependence of electron gas kinetics in a laser corona

    Directory of Open Access Journals (Sweden)

    Mašek Martin

    2013-11-01

    Full Text Available In various experimental situations relevant to the laser fusion, such as plasma near the light entrance holes of hohlraum in the indirect drive experiments or more recently in the shock ignition direct drive a relatively long underdense plasma of corona type is encountered, which is subject to an intense nanosecond laser beam. The plasma is only weakly collisional and thus in the electron phase space a complicated kinetic evolution is going on, which is taking the electron gas fairly far from the thermal equilibrium and contributes to its unstable behaviour. These phenomena impede the absorption and thermalization of the incoming laser energy, create groups of fast electrons and also may lead to a non-linear reflection of the heating laser beam. One of the key processes leading to the electron acceleration is the stimulated Raman scattering (SRS in its non-linear phase. The SRS in the presence of electron-ion collisions requires a certain threshold intensity above which the mentioned non-dissipative phenomena can occur and develop to the stage, where they may become unpleasant for the fusion experiments. To assess this intensity limit a computational model has been developed based on the Vlasov-Maxwell kinetics describing such a plasma in 1D geometry. At a relatively high intensity of 1016 W/cm2 a number of non-linear phenomena are predicted by the code such as a saturation of Landau damping, which is then translated in an unfavourable time dependence of the reflected light intensity and formation of accelerated electron groups due to the electron trapping. The purpose of the present contribution is to map the intensity dependence of this non-linear development with the aim of assessing its weight in fusion relevant situations.

  19. Application of Factorial Design for Gas Parameter Optimization in CO2 Laser Welding

    DEFF Research Database (Denmark)

    Gong, Hui; Dragsted, Birgitte; Olsen, Flemming Ove

    1997-01-01

    The effect of different gas process parameters involved in CO2 laser welding has been studied by applying two-set of three-level complete factorial designs. In this work 5 gas parameters, gas type, gas flow rate, gas blowing angle, gas nozzle diameter, gas blowing point-offset, are optimized...... to be a very useful tool for parameter optimi-zation in laser welding process. Keywords: CO2 laser welding, gas parameters, factorial design, Analysis of Variance........ The bead-on-plate welding specimens are evaluated by a number of quality char-acteristics, such as the penetration depth and the seam width. The significance of the gas pa-rameters and their interactions are based on the data found by the Analysis of Variance-ANOVA. This statistic methodology is proven...

  20. Comparing predictive ability of laser-induced breakdown spectroscopy to visible near-infrared spectroscopy for soil property determination

    DEFF Research Database (Denmark)

    Knadel, Maria; Gislum, René; Hermansen, Cecilie

    2017-01-01

    Soil organic carbon (SOC) and particle size fractions have a practical value for agronomy and the environment. Thus, alternative techniques to replace the expensive conventional analyses of soil are needed. Visible near-infrared reflectance spectroscopy (viseNIRS) has already shown potential...... for becoming an alternative method for soil analysis since it is faster and cheaper than conventional methods. Laser-induced breakdown spectroscopy (LIBS) is another cost-effective technique with potential for rapid analysis of elements present in the soil. In this study, the feasibility of using LIBS...

  1. Label-free optical-resolution photoacoustic microscopy of superficial microvasculature using a compact visible laser diode excitation

    Science.gov (United States)

    Zeng, Lvming; Piao, Zhonglie; Huang, Shenghai; Jia, Wangcun; Chen, Zhongping

    2015-01-01

    We have developed laser-diode-based optical-resolution photoacoustic microscopy (LD-OR-PAM) of superficial microvasculature which has the desirable properties of being compact, low-cost, and label-free. A 300-mW visible pulsed laser diode was operated at a 405 ± 5 nm wavelength with a pulse energy as low as 52 nJ. By using a 3.6 MHz ultrasound transducer, the system was tested on carbon fibers with a lateral resolution of 0.95 µm and an SNR of 38 dB. The subcutaneous microvasculature on a mouse back was imaged without an exogenous contrast agent which demonstrates the potential of the proposed prototype for skin chromophores. Our eventual goal is to offer a practical and affordable multi-wavelength functional LD-OR-PAM instrument suitable for clinical applications. PMID:26698732

  2. Investigation on gas medium parameters for an ArF excimer laser through orthogonal experimental design

    Science.gov (United States)

    Song, Xingliang; Sha, Pengfei; Fan, Yuanyuan; Jiang, R.; Zhao, Jiangshan; Zhou, Yi; Yang, Junhong; Xiong, Guangliang; Wang, Yu

    2018-02-01

    Due to complex kinetics of formation and loss mechanisms, such as ion-ion recombination reaction, neutral species harpoon reaction, excited state quenching and photon absorption, as well as their interactions, the performance behavior of different laser gas medium parameters for excimer laser varies greatly. Therefore, the effects of gas composition and total gas pressure on excimer laser performance attract continual research studies. In this work, orthogonal experimental design (OED) is used to investigate quantitative and qualitative correlations between output laser energy characteristics and gas medium parameters for an ArF excimer laser with plano-plano optical resonator operation. Optimized output laser energy with good pulse to pulse stability can be obtained effectively by proper selection of the gas medium parameters, which makes the most of the ArF excimer laser device. Simple and efficient method for gas medium optimization is proposed and demonstrated experimentally, which provides a global and systematic solution. By detailed statistical analysis, the significance sequence of relevant parameter factors and the optimized composition for gas medium parameters are obtained. Compared with conventional route of varying single gas parameter factor sequentially, this paper presents a more comprehensive way of considering multivariables simultaneously, which seems promising in striking an appropriate balance among various complicated parameters for power scaling study of an excimer laser.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lindley, Roger Alan [Michigan Univ., Ann Arbor, MI (United States)

    1993-01-01

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

  4. Pulsed laser facilities operating from UV to IR at the Gas Laser Lab of the Lebedev Institute

    Science.gov (United States)

    Ionin, Andrei; Kholin, Igor; Vasil'Ev, Boris; Zvorykin, Vladimir

    2003-05-01

    Pulsed laser facilities developed at the Gas Lasers Lab of the Lebedev Physics Institute and their applications for different laser-matter interactions are discussed. The lasers operating from UV to mid-IR spectral region are as follows: e-beam pumped KrF laser (λ= 0.248 μm) with output energy 100 J; e-beam sustained discharge CO2(10.6 μm) and fundamental band CO (5-6 μm) lasers with output energy up to ~1 kJ; overtone CO laser (2.5-4.2 μm) with output energy ~ 50 J and N2O laser (10.9 μm) with output energy of 100 J; optically pumped NH3 laser (11-14 μm). Special attention is paid to an e-beam sustained discharge Ar-Xe laser (1.73 μm ~ 100 J) as a potential candidate for a laser-propulsion facility. The high energy laser facilities are used for interaction of laser radiation with polymer materials, metals, graphite, rocks, etc.

  5. Greenhouse Gas Laser Imaging Tomography Experiment (GreenLITE

    Directory of Open Access Journals (Sweden)

    Dobler Jeremy

    2016-01-01

    Full Text Available Exelis has recently developed a novel laser-based instrument to aid in the autonomous real-time monitoring and mapping of CO2 concentration over a two-dimensional area. The Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE instrument uses two transceivers and a series of retroreflectors to continuously measure the differential transmission over a number of overlapping lines of sight or “chords”, forming a plane. By inverting the differential transmission measurements along with locally measured temperature (T, pressure (P and relative humidity (RH the average concentration of CO2 along each chord can be determined and, based on the overlap between chords, a 2D map of CO2 concentration over the measurement plane can be estimated. The GreenLITE system was deployed to the Zero Emissions Research and Technology (ZERT center in Bozeman, Montana, in Aug-Sept 2014, where more than 200 hours of data were collected over a wide range of environmental conditions, while utilizing a controlled release of CO2 into a segmented underground pipe [1]. The system demonstrated the ability to identify persistent CO2 sources at the test facility and showed strong correlation with an independent measurement using a LI-COR based system. Here we describe the measurement approach, instrument design, and results from the deployment to the ZERT site.

  6. Ignition parameters and early flame kernel development of laser-ignited combustible gas mixtures

    International Nuclear Information System (INIS)

    Kopecek, H.; Wintner, E.; Ruedisser, D.; Iskra, K.; Neger, T.

    2002-01-01

    Full text: Laser induced breakdown of focused pulsed laser radiation, the subsequent plasma formation and thermalization offers a possibility of ignition of combustible gas mixtures free from electrode interferences, an arbitrary choice of the location within the medium and exact timing regardless of the degree of turbulence. The development and the decreasing costs of solid state laser technologies approach the pay-off for the higher complexity of such an ignition system due to several features unique to laser ignition. The feasability of laser ignition was demonstrated in an 1.5 MW(?) natural gas engine, and several investigations were performed to determine optimal ignition energies, focus shapes and laser wavelengths. The early flame kernel development was investigated by time resolved planar laser induced fluorescence of the OH-radical which occurs predominantly in the flame front. The flame front propagation showed typical features like toroidal initial flame development, flame front return and highly increased flame speed along the laser focus axis. (author)

  7. Modeling of growth, evaporation and sedimentation effects on transmission of visible and IR laser beams in artificial fogs

    Science.gov (United States)

    Yue, G. K.; Deepak, A.

    1980-01-01

    The dense polydisperse aerosol particles in a quiet chamber may spontaneously go through different microphysical processes including gravitational sedimentation, thermal coagulation, and growth or evaporation. In an earlier paper, we presented the results of a parametric study of the combined and separate effects of thermal coagulation and sedimentation on the time dependence of extinction of four visible and IR laser beams traversing an aerosol medium. As a continuation of this series of studies, the separate and combined effects of growth or evaporation and gravitational sedimentation on the time dependence of extinction of the same four visible and IR laser beams traversing in artificial fogs will be reported in this paper. The method of numerically modeling the change of water droplet size distribution with time due to growth/evaporation and the cutoff of larger aerosols due to gravitational sedimentation is described in detail. Factors governing the relative importance of these two processes are discussed. Results of this study show that the relative humidity or ambient temperature is a crucial parameter in determining the optical depth of the water droplet and aerosol media undergoing microphysical processes.

  8. Visible microactuation of a ferromagnetic shape memory alloy by focused laser beam

    International Nuclear Information System (INIS)

    Hu, Zhibin; Tamang, Rajesh; Varghese, Binni; Sow, Chorng-Haur; Rajini Kanth, B; Mukhopadhyay, P K

    2012-01-01

    We used a focused laser beam to achieve large amplitude and localized controlled actuation in a microstructure made of a ferromagnetic shape memory alloy. Significant deformation (18 µm) was achieved at low laser power (20 mW) and the amplitude of actuation could be linearly controlled with the laser power. The rapid mechanical actuation shows no apparent sign of fatigue even after a million continuous oscillatory cycles. As a possible mechanism, we propose that the deformation of structure was induced by a combination of the thermal effect and the magnetic field of the incident laser light. This is possibly the first such reported visual evidence of microactuation of materials due to the optomagnetic field. (fast track communication)

  9. In Vitro UV-Visible Spectroscopy Study of Yellow Laser Irradiation on Human Blood

    Science.gov (United States)

    Fuad, Siti Sakinah Mohd; Suardi, N.; Mustafa, I. S.

    2018-04-01

    This experimental study was performed to investigate the effect of low level yellow laser of 589nm wavelength with various laser irradiation time. Human blood samples with random diseases are irradiated with yellow laser of power density of 450mW/cm2 from 10 minutes to 60 minutes at 10 minutes intervals. The morphology of the red blood cell were also observed for different irradiation time. The result shows that there is a significant different in the absorption of light with varying laser irradiation time (pBlood smear of the samples reveals that there are observable changes in the morphology of the red blood cell at 40 minutes and 60 minutes of irradiation.

  10. Visible laser induced positive ion emissions from NaCl nanoparticles prepared by droplet rapid drying

    International Nuclear Information System (INIS)

    Sun, Mao-Xu; Guo, Deng-Zhu; Xing, Ying-Jie; Zhang, Geng-Min

    2012-01-01

    Highlights: ► NaCl nanoparticles were firstly prepared by heat induced explosion on silicon wafer. ► We found that laser induced ion emissions from NaCl nanoparticles are more prominent. ► We found that water adsorption can efficiently enhance laser induced ion emissions. ► The ultra-photothermal effect in NaCl nanoparticles was observed and explained. - Abstract: A novel convenient way for the formation of sodium chloride (NaCl) nanoparticles on silicon wafer is proposed by using a droplet rapid drying method. The laser induced positive ion emissions from NaCl nanoparticles with and without water treatment is demonstrated by using a laser desorption/ionization time-of-flight mass spectrometer, with laser intensity well below the plasma formation threshold. It is found that the positive ion emissions from NaCl nanoparticles are obviously higher than that from microsize NaCl particles under soft 532 nm laser irradiations, and water adsorption can efficiently enhance the ion emissions from NaCl nanoparticles. The initial kinetic energies of the emitted ions are estimated as 16–17 eV. The synergy of the ultra-thermal effect in nanomaterials, the defect-mediated multiphoton processes, and the existence of intermediate states in NaCl-water interfaces are suggested as the mechanisms.

  11. Quantum-cascade laser photoacoustic detection of methane emitted from natural gas powered engines

    Science.gov (United States)

    Rocha, M. V.; Sthel, M. S.; Silva, M. G.; Paiva, L. B.; Pinheiro, F. W.; Miklòs, A.; Vargas, H.

    2012-03-01

    In this work we present a laser photoacoustic arrangement for the detection of the important greenhouse gas methane. A quantum-cascade laser and a differential photoacoustic cell were employed. A detection limit of 45 ppbv in nitrogen was achieved as well as a great selectivity. The same methodology was also tested in the detection of methane issued from natural gas powered vehicles (VNG) in Brazil, which demonstrates the excellent potential of this arrangement for greenhouse gas detection emitted from real sources.

  12. Performance of a high repetition pulse rate laser system for in-gas-jet laser ionization studies with the Leuven laser ion source LISOL

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer, R., E-mail: Rafael.Ferrer@fys.kuleuven.be [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Sonnenschein, V.T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35 (YFL), FI-40014 Jyvaeskylae (Finland); Bastin, B. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Franchoo, S. [Institut de Physique Nucleaire (IPN) d' Orsay, 91406 Orsay, Cedex (France); Huyse, M.; Kudryavtsev, Yu. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Kron, T. [Institut fuer Physik, Universitaet Mainz, D-55128 Mainz (Germany); Lecesne, N. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Moore, I.D. [Department of Physics, University of Jyvaeskylae, P.O. Box 35 (YFL), FI-40014 Jyvaeskylae (Finland); Osmond, B. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Pauwels, D. [SCK-CEN, Belgian Nuclear Research Center, Boeretang 200, 2400 Mol (Belgium); Radulov, D. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Raeder, S. [Institut fuer Physik, Universitaet Mainz, D-55128 Mainz (Germany); Rens, L. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); and others

    2012-11-15

    The laser ionization efficiency of the Leuven gas cell-based laser ion source was investigated under on- and off-line conditions using two distinctly different laser setups: a low-repetition rate dye laser system and a high-repetition rate Ti:sapphire laser system. A systematic study of the ion signal dependence on repetition rate and laser pulse energy was performed in off-line tests using stable cobalt and copper isotopes. These studies also included in-gas-jet laser spectroscopy measurements on the hyperfine structure of {sup 63}Cu. A final run under on-line conditions in which the radioactive isotope {sup 59}Cu (T{sub 1/2} = 81.5 s) was produced, showed a comparable yield of the two laser systems for in-gas-cell ionization. However, a significantly improved time overlap by using the high-repetition rate laser system for in-gas-jet ionization was demonstrated by an increase of the overall duty cycle, and at the same time, pointed to the need for a better shaped atomic jet to reach higher ionization efficiencies.

  13. Laser-driven nuclear-polarized hydrogen internal gas target

    International Nuclear Information System (INIS)

    Seely, J.; Crawford, C.; Clasie, B.; Xu, W.; Dutta, D.; Gao, H.

    2006-01-01

    We report the performance of a laser-driven polarized internal hydrogen gas target (LDT) in a configuration similar to that used in scattering experiments. This target used the technique of spin-exchange optical pumping to produce nuclear spin polarized hydrogen gas that was fed into a cylindrical storage (target) cell. We present in this paper the performance of the target, methods that were tried to improve the figure-of-merit (FOM) of the target, and a Monte Carlo simulation of spin-exchange optical pumping. The dimensions of the apparatus were optimized using the simulation and the experimental results were in good agreement with the results from the simulation. The best experimental result achieved was at a hydrogen flow rate of 1.1x10 18 atoms/s, where the sample beam exiting the storage cell had 58.2% degree of dissociation and 50.5% polarization. Based on this measurement, the atomic fraction in the storage cell was 49.6% and the density averaged nuclear polarization was 25.0%. This represents the highest FOM for hydrogen from an LDT and is higher than the best FOM reported by atomic beam sources that used storage cells

  14. UV laser induced proton-transfer of protein molecule in the gas phase produced by droplet-beam laser ablation

    Science.gov (United States)

    Kohno, Jun-ya; Kondow, Tamotsu

    2008-09-01

    Droplet-beam laser-ablation mass-spectrometry was applied for a study of the UV-laser induced proton-transfer reaction of protonated lysozyme hydrated clusters in the gas phase. Protonated lysozyme hydrated clusters were produced by irradiation of an IR laser onto a droplet-beam of an aqueous solution of lysozyme and were subsequently irradiated by a UV laser. It is found that H + and H 3O + are produced through photodissociation of protonated lysozyme hydrated clusters. The mechanism of the proton-transfer reaction is discussed.

  15. Studies of inactivation mechanism of non-enveloped icosahedral virus by a visible ultrashort pulsed laser.

    Science.gov (United States)

    Tsen, Shaw-Wei D; Kingsley, David H; Poweleit, Christian; Achilefu, Samuel; Soroka, Douglas S; Wu, T C; Tsen, Kong-Thon

    2014-02-05

    Low-power ultrashort pulsed (USP) lasers operating at wavelengths of 425 nm and near infrared region have been shown to effectively inactivate viruses such as human immunodeficiency virus (HIV), M13 bacteriophage, and murine cytomegalovirus (MCMV). It was shown previously that non-enveloped, helical viruses such as M13 bacteriophage, were inactivated by a USP laser through an impulsive stimulated Raman scattering (ISRS) process. Recently, enveloped virus like MCMV has been shown to be inactivated by a USP laser via protein aggregation induced by an ISRS process. However, the inactivation mechanism for a clinically important class of viruses--non-enveloped, icosahedral viruses remains unknown. We have ruled out the following four possible inactivation mechanisms for non-enveloped, icosahedral viruses, namely, (1) inactivation due to ultraviolet C (UVC) photons produced by non-linear optical process of the intense, fundamental laser beam at 425 nm; (2) inactivation caused by thermal heating generated by the direct laser absorption/heating of the virion; (3) inactivation resulting from a one-photon absorption process via chromophores such as porphyrin molecules, or indicator dyes, potentially producing reactive oxygen or other species; (4) inactivation by the USP lasers in which the extremely intense laser pulse produces shock wave-like vibrations upon impact with the viral particle. We present data which support that the inactivation mechanism for non-enveloped, icosahedral viruses is the impulsive stimulated Raman scattering process. Real-time PCR experiments show that, within the amplicon size of 273 bp tested, there is no damage on the genome of MNV-1 caused by the USP laser irradiation. We conclude that our model non-enveloped virus, MNV-1, is inactivated by the ISRS process. These studies provide fundamental knowledge on photon-virus interactions on femtosecond time scales. From the analysis of the transmission electron microscope (TEM) images of viral particles

  16. [Basic research for visible laser unit for the spinal cord (a preliminary report)].

    Science.gov (United States)

    Egashira, T; Yoshii, Y; Maki, Y

    1983-04-01

    The cat's spinal dorsal column was irradiated unilaterally with Ar. laser of which power output was 500 mW and the spot size was 2 mm in diameter. The somatosensory evoked potentials (S.E.P.) were recorded bilaterally. In other cats, the fluorescein was injected intravenously for photoactivation and the dorsal column was irradiated with Ar. laser. The conclusion can be summarized as follows: 1) When the small demarcated area was made in the surface of the dorsal column by Ar. laser-irradiation, the early component of S.E.P. was disappeared. The histological finding revealed the destruction of the irradiated dorsal column. 2) The photoactivation effect of Ar. laser was demonstrated in the spinal cord, by using a fluorescein drug. The S.E.P. and the histological finding were the same as those of the nonfluorescein drug group. 3) The S.E.P. was available for the concept of the Laser-Photo-Biological-Effect (L.P.B.E.).

  17. Gas ion laser construction for electrically isolating the pressure gauge thereof

    Science.gov (United States)

    Wood, C. E.; Witte, R. S. (Inventor)

    1975-01-01

    The valve and the pressure gauge of a gas ion laser were electrically insulated from the laser discharge path by connecting them in series with the cathode of the laser. The laser cathode can be grounded and preferably is a cold cathode although a hot cathode may be used instead. The cold cathode was provided with a central aperture to which was connected both the pressure gauge and the gas pressure reservoir through the valve. This will effectively prevent electric discharges from passing either to the pressure gauge or the valve which would otherwise destroy the pressure gauge.

  18. Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE)

    Energy Technology Data Exchange (ETDEWEB)

    Dobler, Jeremy [Exelis Inc., Fort Wayne, IN (United States); Zaccheo, T. Scott [Exelis Inc., Fort Wayne, IN (United States); Blume, Nathan [Exelis Inc., Fort Wayne, IN (United States); Pernini, Timothy [Exelis Inc., Fort Wayne, IN (United States); Braun, Michael [Exelis Inc., Fort Wayne, IN (United States); Botos, Christopher [Exelis Inc., Fort Wayne, IN (United States)

    2016-03-31

    This report describes the development and testing of a novel system, the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE), for Monitoring, Reporting and Verification (MRV) of CO2 at Geological Carbon Storage (GCS) sites. The system consists of a pair of laser based transceivers, a number of retroreflectors, and a set of cloud based data processing, storage and dissemination tools, which enable 2-D mapping of the CO2 in near real time. A system was built, tested locally in New Haven, Indiana, and then deployed to the Zero Emissions Research and Technology (ZERT) facility in Bozeman, MT. Testing at ZERT demonstrated the ability of the GreenLITE system to identify and map small underground leaks, in the presence of other biological sources and with widely varying background concentrations. The system was then ruggedized and tested at the Harris test site in New Haven, IN, during winter time while exposed to temperatures as low as -15 °CºC. Additional testing was conducted using simulated concentration enhancements to validate the 2-D retrieval accuracy. This test resulted in a high confidence in the reconstruction ability to identify sources to tens of meters resolution in this configuration. Finally, the system was deployed for a period of approximately 6 months to an active industrial site, Illinois Basin – Decatur Project (IBDP), where >1M metric tons of CO2 had been injected into an underground sandstone basin. The main objective of this final deployment was to demonstrate autonomous operation over a wide range of environmental conditions with very little human interaction, and to demonstrate the feasibility of the system for long term deployment in a GCS environment.

  19. High gain semiconductor optical amplifier — Laser diode at visible wavelength

    KAUST Repository

    Shen, Chao

    2017-02-07

    We reported on the first experimental demonstration of a two-section semipolar InGaN-based laser diode with monolithically integrated semiconductor optical amplifier (SOA-LD). The onset of amplification effect was measured at 4V SOA bias (VSOA). The SOA-LD shows a large gain of 5.32 dB at Vsoa = 6 V.

  20. [Gas pipeline leak detection based on tunable diode laser absorption spectroscopy].

    Science.gov (United States)

    Zhang, Qi-Xing; Wang, Jin-Jun; Liu, Bing-Hai; Cai, Ting-Li; Qiao, Li-Feng; Zhang, Yong-Ming

    2009-08-01

    The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection.

  1. Bactericidal effect of visible light in the presence of erythrosine on Porphyromonas gingivalis and Fusobacterium nucleatum compared with diode laser, an in vitro study.

    Science.gov (United States)

    Habiboallah, Ghanbari; Mahdi, Zakeri; Mahbobeh, Naderi Nasab; Mina, Zareian Jahromi; Sina, Faghihi; Majid, Zakeri

    2014-12-27

    Recently, photodynamic therapy (PDT) has been introduced as a new modality in oral bacterial decontamination. Besides, the ability of laser irradiation in the presence of photosensitizing agent to lethal effect on oral bacteria is well documented. Current research aims to evaluate the effect of photodynamic killing of visible blue light in the presence of plaque disclosing agent erythrosine as photosensitizer on Porphyromonas gingivalis associated with periodontal bone loss and Fusobacterium nucleatum associated with soft tissue inflammation, comparing with the near-infrared diode laser. Standard suspension of P. gingivalis and F. nucleatum were exposed to Light Emitting Diode (LED) (440-480 nm) used to photopolymerize composite resine dental restoration in combination with erythrosine (22 µm) up to 5 minutes. Bacterial sample were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. Bacterial samples from each treatment groups (radiation-only group, erythrosine-only group and light or laser with erythrosine group) were subcultured onto the surface of agar plates. Survival of these bacteria was determined by counting the number of colony forming units (CFU) after incubation. Exposure to visible blue light and diode laser in conjugation with erythrosine significantly reduced both species examined viability, whereas erythrosine-treated samples exposed to visible light suggested a statically meaningful differences comparing to diode laser. In addition, bactericidal effect of visible light or diode laser alone on P. gingivalis as black-pigmented bacteria possess endogenous porphyrins was noticeably. Our result suggested that visible blue light source in the presence of plaque disclosing agent erythrosine could can be consider as potential approach of PDT to kill the main gram-negative periodontal pathogens. From a clinical standpoint, this regimen could be established as an additional minimally

  2. Detection using visible laser of palm oil quality affected by heating process

    International Nuclear Information System (INIS)

    El-Rahman, A.A.; Badawy, H.A.

    2010-01-01

    Palm oil was heated at 180 degree C for six times (3, 6, 9, 12, 15, and 18 hours) to measure some physical, chemical and optical properties. Palm oil was exposure to laser beam to determine optical properties of oils using (He-Ne) lasers with wavelengths 632.8 and 543.5 nm. The obtained results are as follows: (1) Chemical properties such as oxidized fatty acid, acid value and peroxide value were increased by increasing heating time, but the iodine value was decreased. Meanwhile, physical properties such as viscosity and reflective index were increased at the same of heating times., (2) By increasing heating time of palm oil from 3 to 18 hrs, the absorbed of wavelengths of laser beam with wavelength 543.5 nm was more absorbed than 632.8 nm. Meanwhile, the transmission of laser beam with wavelength 543.5 nm was more high transmission than 632.8 nm., (3) The deterioration of palm oil was started after 16 hours of heating at the light intensity 228 and 368 lux of transmission for wavelengths of 543.5 and 632.8 nm., (4) There are high relation between heating time and chemical, physical, optical properties. The R square was ranged from 0.83 to 0.97, from 0.89 to 0.96 and from 0.95 to 0.98 for chemical, physical, and optical properties with heating, and (5) From optical properties we can determine the quality of oil using the laser transmission or absorbed as a detector of oil quality.

  3. Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL

    Energy Technology Data Exchange (ETDEWEB)

    Raeder, S., E-mail: s.raeder@gsi.de [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Helmholtz-Institut Mainz, 55128 Mainz (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt (Germany); Bastin, B. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Block, M. [Helmholtz-Institut Mainz, 55128 Mainz (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt (Germany); Institut für Kernchemie, Johannes Gutenberg Universität, 55128 Mainz (Germany); Creemers, P. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Delahaye, P. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Ferrer, R. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Fléchard, X. [LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen (France); Franchoo, S. [Institute de Physique Nucléaire (IPN) d’Orsay, 91406 Orsay, Cedex (France); Ghys, L. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); SCK-CEN, Belgian Nuclear Research Center, Boeretang 200, 2400 Mol (Belgium); Gaffney, L.P.; Granados, C. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Heinke, R. [Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz (Germany); Hijazi, L. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); and others

    2016-06-01

    To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique.

  4. UV-Visible Absorption Spectroscopy Enhanced X-ray Crystallography at Synchrotron and X-ray Free Electron Laser Sources.

    Science.gov (United States)

    Cohen, Aina E; Doukov, Tzanko; Soltis, Michael S

    2016-01-01

    This review describes the use of single crystal UV-Visible Absorption micro-Spectrophotometry (UV-Vis AS) to enhance the design and execution of X-ray crystallography experiments for structural investigations of reaction intermediates of redox active and photosensitive proteins. Considerations for UV-Vis AS measurements at the synchrotron and associated instrumentation are described. UV-Vis AS is useful to verify the intermediate state of an enzyme and to monitor the progression of reactions within crystals. Radiation induced redox changes within protein crystals may be monitored to devise effective diffraction data collection strategies. An overview of the specific effects of radiation damage on macromolecular crystals is presented along with data collection strategies that minimize these effects by combining data from multiple crystals used at the synchrotron and with the X-ray free electron laser.

  5. Design of a surface-emitting, subwavelength metal-clad disk laser in the visible spectrum

    OpenAIRE

    Huang, Jingqing; Kim, Se-Heon; Scherer, Axel

    2010-01-01

    We analyze metal-clad disk cavities designed for nanolasers in the visible red spectrum with subwavelength device size and mode volume. Metal cladding suppresses radiation loss and supports low order modes with room temperature Q of 200 to 300. Non-degenerate single-mode operation with enhanced spontaneous emission coupling factor β is expected with the TE_(011) mode that has a 0.46(λ_0/n)^3 mode volume and Q = 210 in a device of size 0.12λ_0^3. Threshold gain calculations show that room temp...

  6. Experimental demonstration of OFDM/OQAM transmission with DFT-based channel estimation for visible laser light communications

    Science.gov (United States)

    He, Jing; Shi, Jin; Deng, Rui; Chen, Lin

    2017-08-01

    Recently, visible light communication (VLC) based on light-emitting diodes (LEDs) is considered as a candidate technology for fifth-generation (5G) communications, VLC is free of electromagnetic interference and it can simplify the integration of VLC into heterogeneous wireless networks. Due to the data rates of VLC system limited by the low pumping efficiency, small output power and narrow modulation bandwidth, visible laser light communication (VLLC) system with laser diode (LD) has paid more attention. In addition, orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) is currently attracting attention in optical communications. Due to the non-requirement of cyclic prefix (CP) and time-frequency domain well-localized pulse shapes, it can achieve high spectral efficiency. Moreover, OFDM/OQAM has lower out-of-band power leakage so that it increases the system robustness against inter-carrier interference (ICI) and frequency offset. In this paper, a Discrete Fourier Transform (DFT)-based channel estimation scheme combined with the interference approximation method (IAM) is proposed and experimentally demonstrated for VLLC OFDM/OQAM system. The performance of VLLC OFDM/OQAM system with and without DFT-based channel estimation is investigated. Moreover, the proposed DFT-based channel estimation scheme and the intra-symbol frequency-domain averaging (ISFA)-based method are also compared for the VLLC OFDM/OQAM system. The experimental results show that, the performance of EVM using the DFT-based channel estimation scheme is improved about 3dB compared with the conventional IAM method. In addition, the DFT-based channel estimation scheme can resist the channel noise effectively than that of the ISFA-based method.

  7. Applications of laser-photoacoustic gas analysis method

    Energy Technology Data Exchange (ETDEWEB)

    Hernberg, R.; Stenberg, J. [Tampere Univ. of Technology (Finland). Dept. of Physics

    1996-12-01

    The dynamic behavior of a circulating fluidized bed boiler (CFB) was studied using two high speed gas analysis systems during combustion of coal, peat and wood chips. Time resolved concentrations of some pollutants (SO{sub 2}, NO, NH{sub 3} and H{sub 2}S) were measured using laser induced photoacoustic spectroscopy (LIPS). A zirkonia cell based probe (lambda-probe) was used in synchronization with the LIPS-probe to measure fluctuations between reducing and oxidizing conditions. The two probes were positioned in the same measurement volume on the center-line of the combustion chamber of the CFB. The purpose of the measurements was to investigate the behavior of the LIPS in a combustion chamber containing large amounts of other unburnt hydrocarbons. The correlations between oxidizing and reducing conditions and concentrations at three locations in the combustion chamber are presented. The best correlations were found in the upper part of the CFB combustion chamber. In some cases the correlations between reducing conditions and the LIPS signal were caused by hydrocarbons. Comparison of the average values obtained by the LIPS-system for NO and SO{sub 2} with the result from a sampling probe system connected to on-line analysers was also carried out. (author)

  8. The Laser Ion Source Trap (LIST) coupled to a gas cell catcher

    Energy Technology Data Exchange (ETDEWEB)

    Sonoda, T. [Instituut voor Kern- en Stralingsfysica, K.U. Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)], E-mail: tetsu@riken.jp; Cocolios, T.E.; Gentens, J.; Huyse, M.; Ivanov, O.; Kudryavtsev, Yu.; Pauwels, D.; Van den Bergh, P.; Van Duppen, P. [Instituut voor Kern- en Stralingsfysica, K.U. Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2009-09-01

    The proof of principle of the Laser Ion Source Trap (LIST) coupled to a gas cell catcher system has been demonstrated at the Leuven Isotope Separator On Line (LISOL). The experiments were carried out by using the modified gas cell-based laser ion source and the SextuPole Ion Guide (SPIG). Element-selective resonance laser ionization of neutral atoms was taking place inside the cold jet expanding out of the gas cell catcher. The laser path was oriented in longitudinal as well as transverse geometries with respect to the atoms flow. The enhancement of beam purity and the feasibility for in-source laser spectroscopy were investigated in off-line and on-line conditions.

  9. Erosion processes and micro-particle production in gas discharge lasers

    Energy Technology Data Exchange (ETDEWEB)

    Letardi, T.; Giordano, G. [ENEA, Centro Ricerche Frascati, Frascati, RM (Italy). Dipt. Innovazione

    1999-07-01

    The erosion processes of the cathode for pulsed excimer gas lasers are explained by comparing the initiation conditions of the pulsed excimer gas laser discharge to that of the vacuum discharge breakdown. The number of the micro-particles, generated due to the above cathode-processes, are estimated. Several possible influences of the micro-particles on performances of the gas discharge lasers are analyzed. Two methods for eliminating the micro-particles or reducing their influences are discussed. [Italian] Viene descritto, comparandolo con la scarica in vuoto, il processo di erosione del catodo di un laser ad eccimeri a scarica. Viene stimato il numero delle micro-particelle generate dal processo di scarica. Vengono analizzate le possibili influenze di tali micro-particelle sulle prestazioni dei laser a scarica. Sono presentati e discussi due possibili metodi per la eliminazione delle micro-particelle generate dalla scarica.

  10. Demonstration of a neonlike argon soft-x-ray laser with a picosecond-laser-irradiated gas puff target.

    Science.gov (United States)

    Fiedorowicz, H; Bartnik, A; Dunn, J; Smith, R F; Hunter, J; Nilsen, J; Osterheld, A L; Shlyaptsev, V N

    2001-09-15

    We demonstrate a neonlike argon-ion x-ray laser, using a short-pulse laser-irradiated gas puff target. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit and irradiated with a combination of long, 600-ps and short, 6-ps high-power laser pulses with a total of 10 J of energy in a traveling-wave excitation scheme. Lasing was observed on the 3p (1)S(0)?3s (1)P(1) transition at 46.9 nm and the 3d (1)P(1)?3p (1)P(1) transition at 45.1 nm. A gain of 11 cm(-1) was measured on these transitions for targets up to 0.9 cm long.

  11. Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum.

    Science.gov (United States)

    Ghanbari, Habibollah; Mousavi, Seyed Amir; Forouzanfar, Ali; Zakeri, Mahdi; Shafaee, Hooman; Shahnaseri, Shirin

    2015-01-01

    According to the development of resistant strains of pathogenic bacteria following treatment with antimicrobial chemotherapeutic agents, alternative approaches such as lethal photosensitization are being used. The aim of this study was to evaluate the effect of visible light and laser beam radiation in conjugation with three different photosensitizers on the survival of two main periodontopathogenic bacteria including Porphyromonas gingivalis and Fusobacterium nucleatum in different exposure periods. In this in vitro prospective study, strains of P. gingivalis and F. nucleatum. were exposed to visible light at wavelengths of 440 nm and diode laser light, Gallium-Arsenide, at wavelength of 830 nm in the presence of a photosensitizer (erythrosine, curcuma, or hydrogen peroxide). They were exposed 1-5 min to each light. Each experiment was repeated 3 times for each strain of bacteria. Data were analyzed by two-ways ANOVA and least significant difference post-hoc tests. P < 0.05 was considered as significant. After 4 days the colonies were counted. Viability of P. gingivalis was reduced 10% and 20% subsequent to exposure to visible light and diode laser, respectively. The values were 65% and 75% for F. nucleatum in a period of 5-min, respectively. Exposure to visible light or laser beam in conjugation with the photosensitizers suspension caused significant reduction in the number of P. gingivalis in duration of 5-min, suggesting a synergic phototoxic effect. However, the survival rate of F. nucleatum following the exposure to laser with hydrogen peroxide, erythrosine and rhizome of Curcuma longa (curcumin) after 5-min was 10%, 20% and 90% respectively. Within the limitations of this study, the synergic phototoxic effect of visible light in combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on F. nucleatum was not shown.

  12. Characterization of a plasma produced using a high power laser with a gas puff target for x-ray laser experiments

    International Nuclear Information System (INIS)

    Fiedorowicz, H.; Bartnik, A.; Gac, K.; Parys, P.; Szczurek, M.; Tyl, J.

    1995-01-01

    A high temperature, high density plasma can be produced by using a nanosecond, high-power laser with a gas puff target. The gas puff target is formed by puffing a small amount of gas from a high-pressure reservoir through a nozzle into a vacuum chamber. In this paper we present the gas puff target specially designed for x-ray laser experiments. The solenoid valve with the nozzle in the form of a slit 0.3-mm wide and up to 40-mm long, allows to form an elongated gas puff suitable for the creation of an x-ray laser active medium by its perpendicular irradiation with the use of a laser beam focused to a line. Preliminary results of the experiments on the laser irradiation of the gas puff targets, produced by the new valve, show that hot plasma suitable for x-ray lasers is created

  13. Thermodynamic explanation of eliminating platinum inclusions in laser glass by POCl3 gas bubbling

    International Nuclear Information System (INIS)

    Jiang Zhonghong; Hu Lili; Yu Yaochu

    1995-01-01

    The mechanism of eliminating platinum inclusions in laser glass by POCl 3 gas bubbling has been discussed from thermodynamic aspects in the present paper. It is deduced from calculated reaction free energy that the platinum inclusion is ionized after POCl 3 gas bubbling in the existence of water and oxygen. The platinum inclusion is dissolved as platinum(II) metaphosphate in the laser glass matrix

  14. Laser-induced transformation of GaS and GaSe nanosheets to ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Experimental evidence for the transformation of nanosheets of GaS and GaSe into onion struc- tures on UV excimer pulsed laser irradiation is presented. Few-layer GaS and GaSe on Si substrates were exposed to KrF pulsed laser with wavelength of 248 nm and the effect was studied as a function of number of.

  15. Pulsed Gas Lasers Pumped by a Runaway Electron Initiated Discharge

    Science.gov (United States)

    Panchenko, A. N.; Tarasenko, V. F.; Panchenko, N. A.

    2017-12-01

    The generation parameters are investigated in a runaway electron preionized diffuse discharge (REP DD). Laser generation is produced in different spectral bands from the IR to VUV range. New modes of the nitrogen laser operation are obtained. Ultimate efficiencies of N2- and nonchain HF(DF)-lasers are achieved. A possibility of increasing the pulse durations of XeF-, KrF-, ArF- and VUV F2- lasers (157 nm) in an oscillating REP DD is shown. The efficiencies of VUV- and UV-generation comparable with that of a laser pumped by a self-sustained volume discharge with preionization are gained.

  16. Gas laser having an integral optical resonator with external stabilizing means

    International Nuclear Information System (INIS)

    Hensolt, R.A.; Dowley, M.W.

    1975-01-01

    A gaseous laser having an internal optical resonator is provided with external stabilizing means for maintaining alignment of mirrors forming the optical resonator. Means are also provided for allowing expansion of the remainder of the gas-confining envelope relative to the stabilized resonator mirrors during the operation of the laser. (U.S.)

  17. High repetition rate pulsed gas lasers and their applications in chemistry and isotope separation

    International Nuclear Information System (INIS)

    Barahov, V.Y.

    1983-01-01

    Presented in this paper are the results of experimental studies of pulsed high repetition rate XeCl, CO 2 , NH 3 , and CF 4 lasers with a closed gas cycle. Some applications of these lasers in chemistry and isotope separation are discussed

  18. A Plasma Control and Gas Protection System for Laser Welding of Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther; Olsen, Flemming Ove

    1997-01-01

    stability and protection against oxidation. Also oxidation related to special conditions at the starting edge has been investigated. The interaction between coaxial and plasma gas flow show that the coaxial flow widens the band in which the plasma gas flow suppresses the metal plasma. In this band the welds......A prototype shield gas box with different plasma control nozzles have been investigated for laser welding of stainless steel (AISI 316). Different gases for plasma control and gas protection of the weld seam have been used. The gas types, welding speed and gas flows show the impact on process...

  19. Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum

    Directory of Open Access Journals (Sweden)

    Habibollah Ghanbari

    2015-01-01

    Conclusion: Within the limitations of this study, the synergic phototoxic effect of visible light in combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on F. nucleatum was not shown.

  20. Azides and nitrides in joints welded by laser using N2 as covering gas

    Science.gov (United States)

    Daurelio, Giuseppe; Dionoro, G.; Memola Capece Minutolo, F.; Panagopoulos, Christos N.

    1993-05-01

    A large amount of metals and alloys are successfully penetration welded by pulsed or cw laser. The laser welding process requires a gas flow (covering gas) to ensure adequate protection of the melt against atmospheric oxidation. The gas can be supplied in a variety of ways but in many cases the coaxial gas-laser geometry is used. This work is concerned with technological and structural investigations (using SEM and A.E.S. microanalysis) aimed at identifying any particular differences in the welds obtained using N2 instead of He as the covering gas. The investigations conducted on INCONEL 600 and stainless steel appear to provide conclusive evidence that N2 may be readily used as an alternative to He. Very recent works have studied some peculiarities (blanketing, transmission, and process efficiency) of N2 as a covering gas, when used in 2 kW CO2 laser welding. The influence of the covering gas in welding two stainless steels (AISI 304 and 430) and of a nickel alloy (INCONEL 600) using a 2 kW CO2 laser is examined.

  1. Development of a gas cell-based laser ion source for RIKEN PALIS

    Energy Technology Data Exchange (ETDEWEB)

    Sonoda, T., E-mail: tetsu@riken.jp; Wada, M. [RIKEN, SLOWRI Team, Nishina Center for Accelerator-Based Science (Japan); Tomita, H.; Sakamoto, C.; Takatsuka, T.; Noto, T. [Nagoya University, Faculty of Engineering (Japan); Iimura, H. [Japan Atomic Energy Agency (JAEA) (Japan); Matsuo, Y.; Kubo, T. [RIKEN, SLOWRI Team, Nishina Center for Accelerator-Based Science (Japan); Shinozuka, T.; Wakui, T. [Tohoku University, Cyclotron and Radioisotope Center (Japan); Mita, H. [Tsukuba University, Department of Physics (Japan); Naimi, S. [RIKEN, SLOWRI Team, Nishina Center for Accelerator-Based Science (Japan); Furukawa, T. [Tokyo Metropolitan University, Department of Physics (Japan); Itou, Y.; Schury, P. [Tsukuba University, Department of Physics (Japan); Miyatake, H.; Jeong, S.; Ishiyama, H.; Watanabe, Y. [High Energy Accelerator Research Organization (KEK) (Japan); and others

    2013-04-15

    We developed a prototype laser ionization gas cell with a beam extraction system. This device is for use of PArasitic Laser Ion-Source (PALIS), which will be implemented into RIKEN's fragment separator, BigRIPS as a part of SLOWRI. Off-line resonant laser ionization for stable Co, Cu, Fe, Ni, Ti, Nb, Sn, In and Pd inside the gas cell, ion extraction and transport to the high-vacuum region via SPIG and QMS have been confirmed (Sonoda et al, Nucl Instrum Meth B 295:1, 2013).

  2. HV discharge acceleration by sequences of UV laser filaments with visible and near-infrared pulses

    Science.gov (United States)

    Schubert, Elise; Rastegari, Ali; Feng, Chengyong; Mongin, Denis; Kamer, Brian; Kasparian, Jérôme; Wolf, Jean-Pierre; Arissian, Ladan; Diels, Jean-Claude

    2017-12-01

    We investigate the triggering and guiding of DC high-voltage discharges over a distance of 37 cm by filaments produced by ultraviolet (266 nm) laser pulses of 200 ps duration. The latter reduce the breakdown electric field by half and allow up to 80% discharge probability in an electric field of 920 kV m–1. This high efficiency is not further increased by adding nanosecond pulses in the Joule range at 532 and at 1064 nm. However, the latter statistically increases the guiding length, thereby accelerating the discharge by a factor of 2. This effect is due both to photodetachment and to the heating of the plasma channel, that increases the efficiency of avalanche ionization and reduces electron attachment and recombination.

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

    Science.gov (United States)

    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.

  4. Visible photodissociation spectra of the 1- and 2-methylnaphthalene cations: laser spectroscopy and theoretical simulations.

    Science.gov (United States)

    Friha, Hela; Féraud, Géraldine; Troy, Tyler; Falvo, Cyril; Parneix, Pascal; Bréchignac, Philippe; Dhaouadi, Zoubeida; Schmidt, Timothy W; Pino, Thomas

    2013-12-19

    The electronic absorption spectra of the two methyl derivatives of the naphthalene cation were measured using an argon tagging technique. In both cases, a band system was observed in the visible range and assigned to the D2 ← D0 electronic transition. The 1-methylnaphthalene(+) absorption bands revealed a red shift of 808 cm(-1), relative to those of the naphthalene cation (14,906 cm(-1)), whereas for 2-methylnaphthalene(+) a blue shift of 226 cm(-1) appeared. A short vibrational progression, similar to the naphthalene cation, was also observed for both isomers and found to involve similar aromatic ring skeleton vibrations. Moreover, insights into the internal rotation motion of the methyl group were inferred, although the spectral resolution was not sufficient to fully resolve the substructure. These measurements were supported by detailed quantum chemical calculations. They allowed exploration of the potential energy curves along this internal coordinate, along with a complete simulation of the harmonic Franck-Condon factors using the cumulant Gaussian fluctuations formalism extended to include the internal rotation.

  5. Parametric Study of Laser Driven Proton Beams from a Critical Density Gas Jet

    Science.gov (United States)

    Haberberger, D.; Tsung, F.; Tochitsky, S.; Mori, W.; Joshi, C.

    2009-11-01

    Laser driven ion acceleration (LDIA) is studied via particle-in-cell simulations in a novel parameter space for laser-plasma interactions of a relativistic laser pulse with a gas jet target at the critical plasma density (nc). Previous LDIA studies have been based on the interaction of a 1μm laser pulse with either a solid foil (n˜100nc) or a gas jet (nhigh power CO2 laser pulse at a H2 gas jet which is tunable around the critical plasma density for 10μm radiation (10^19cm-3). A rectangular H2 gas jet operated near nc lends itself to efficient coupling of the laser light to forward directed electrons instigating the target normal sheath acceleration mechanism to produce a beam of protons. Results are presented here on a parametric study of the peak plasma density and plasma profile to find optimal conditions for total charge, divergence, and energy of the accelerated proton beam. These simulations support an ongoing LDIA experiment at the Neptune Laboratory at UCLA using a 3ps 1TW CO2 laser pulse for the production of collimated proton beams.

  6. 3D printing of gas jet nozzles for laser-plasma accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Döpp, A.; Guillaume, E.; Thaury, C.; Gautier, J.; Ta Phuoc, K.; Malka, V. [LOA, ENSTA ParisTech, CNRS, École Polytechnique, Université Paris-Saclay, 828 Boulevard des Maréchaux, 91762 Palaiseau Cedex (France)

    2016-07-15

    Recent results on laser wakefield acceleration in tailored plasma channels have underlined the importance of controlling the density profile of the gas target. In particular, it was reported that the appropriate density tailoring can result in improved injection, acceleration, and collimation of laser-accelerated electron beams. To achieve such profiles, innovative target designs are required. For this purpose, we have reviewed the usage of additive layer manufacturing, commonly known as 3D printing, in order to produce gas jet nozzles. Notably we have compared the performance of two industry standard techniques, namely, selective laser sintering (SLS) and stereolithography (SLA). Furthermore we have used the common fused deposition modeling to reproduce basic gas jet designs and used SLA and SLS for more sophisticated nozzle designs. The nozzles are characterized interferometrically and used for electron acceleration experiments with the SALLE JAUNE terawatt laser at Laboratoire d’Optique Appliquée.

  7. Resonance ionization in a gas cell: a feasibility study for a laser ion source

    International Nuclear Information System (INIS)

    Qamhieh, Z.N.; Vandeweert, E.; Silverans, R.E.; Duppen, P. van; Huyse, M.; Vermeeren, L.

    1992-01-01

    A laser ion source based on resonance photo-ionization in a gas cell is proposed. The gas cell, filled with helium, consists of a target chamber in which the recoil products are stopped and neutralized, and an ionization chamber where the atoms of interest are selectively ionized by the laser light. The extraction of the ions from the ionization chamber through the exit hole-skimmer setup is similar to the ion-guide system. The conditions to obtain an optimal system are given. The results of a two-step one-laser resonance photo-ionization of nickel and the first results of laser ionization in a helium buffer gas cell are presented. (orig.)

  8. The growth of human scalp hair in females using visible red light laser and LED sources.

    Science.gov (United States)

    Lanzafame, Raymond J; Blanche, Raymond R; Chiacchierini, Richard P; Kazmirek, Eric R; Sklar, Jeffrey A

    2014-10-01

    Low level laser (light) therapy (LLLT) has been demonstrated to promote hair growth in males. A double-blind randomized controlled trial was undertaken to define the safety and physiologic effects of LLLT on females with androgenic alopecia. Forty-seven females (18-60 years old, Fitzpatrick I-IV, and Ludwig-Savin Baldness Scale I-2, I-3, I-4, II-1, II-2 baldness patterns) were recruited. A transition zone scalp site was selected; hairs were trimmed to 3 mm height; the area was tattooed and photographed. The active group received a "TOPHAT655" unit containing 21, 5 mW diode lasers (655 ± 5 nm) and 30 LEDS (655 ± 20 nm), in a bicycle-helmet like apparatus. The placebo group unit appeared identical, containing incandescent red lights. Patients treated at home every other day × 16 weeks (60 treatments, 67 J/cm(2) irradiance/25 minute treatment, 2.9 J dose), with follow up and photography at 16 weeks. A masked 2.85 cm(2) photographic area was evaluated by another blinded investigator. The primary endpoint was the percent increase in hair counts from baseline. Forty-two patients completed the study (24 active, 18 sham). No adverse events or side effects were reported. Baseline hair counts were 228.2 ± 133.4 (N = 18) in the sham and 209.6 ± 118.5 (N = 24) in the active group (P = 0.642). Post Treatment hair counts were 252.1 ± 143.3 (N = 18) in the sham group and 309.9 ± 166.6 (N = 24) in the active group (P = 0.235). The change in hair counts over baseline was 23.9 ± 30.1 (N = 18) in the sham group and 100.3 ± 53.4 (N = 24) in the active group (P hair increase over the duration of the study was 11.05 ± 48.30 (N = 18) for the sham group and 48.07 ± 17.61 (N = 24) for the active group (P hair growth in the active treatment group as compared to the placebo group. LLLT of the scalp at 655 nm significantly improved hair counts in women with androgenetic

  9. High pressure gas laser technology for atmospheric remote sensing

    Science.gov (United States)

    Javan, A.

    1980-01-01

    The development of a fixed frequency chirp-free and highly stable intense pulsed laser made for Doppler wind velocity measurements with accurate ranging is described. Energy extraction from a high pressure CO2 laser at a tunable single mode frequency is also examined.

  10. Plasma Control and Gas Protection System for Laser Welding of Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther; Olsen, Flemming Ove; Petersen, Kaj

    1997-01-01

    stability and protection against oxidation. Also oxidation related to special conditions at the starting edge has been investigated. The interaction between coaxial and plasma gas flow show that the coaxial flow widens the band in which the plasma gas flow suppresses the metal plasma. In this band the welds......An integrated plasma nozzle and a shield gas box have been investigated for laser welding of 2 mm stainless steel sheets. Different gases for plasma control and gas protection of the weld seam have been used. The gas types, welding speed and coaxial and plasma flow show the impact on process...

  11. High power electron beam accelerators for gas laser excitation

    International Nuclear Information System (INIS)

    Kelly, J.G.; Martin, T.H.; Halbleib, J.A.

    1976-06-01

    A preliminary parameter investigation has been used to determine a possible design of a high-power, relativistic electron beam, transversely excited laser. Based on considerations of present and developing pulsed power technology, broad area diode physics and projected laser requirements, an exciter is proposed consisting of a Marx generator, pulse shaping transmission lines, radially converging ring diodes and a laser chamber. The accelerator should be able to deliver approximately 20 kJ of electron energy at 1 MeV to the 10 4 cm 2 cylindrical surface of a laser chamber 1 m long and 0.3 m in diameter in 24 ns with very small azimuthal asymmetry and uniform radial deposition

  12. Comparative evaluation of tungsten inert gas and laser beam ...

    Indian Academy of Sciences (India)

    - cluded that LB welding process is more suitable to join AA5083-H321. Keywords. Aluminum alloys; laser beam welding; mechanical properties; vapourization. 1. Introduction. Aluminum and its alloys are widely used in the transportation, ...

  13. In-gas laser ionization and spectroscopy of actinium isotopes near the N =126 closed shell

    Science.gov (United States)

    Granados, C.; Creemers, P.; Ferrer, R.; Gaffney, L. P.; Gins, W.; de Groote, R.; Huyse, M.; Kudryavtsev, Yu.; Martínez, Y.; Raeder, S.; Sels, S.; Van Beveren, C.; Van den Bergh, P.; Van Duppen, P.; Wrzosek-Lipska, K.; Zadvornaya, A.; Barzakh, A. E.; Bastin, B.; Delahaye, P.; Hijazi, L.; Lecesne, N.; Luton, F.; Piot, J.; Savajols, H.; Thomas, J.-C.; Traykov, E.; Beerwerth, R.; Fritzsche, S.; Block, M.; Fléchard, X.; Franchoo, S.; Ghys, L.; Grawe, H.; Heinke, R.; Kron, T.; Naubereit, P.; Wendt, K.; Laatiaoui, M.; Moore, I.; Sonnenschein, V.; Loiselet, M.; Mogilevskiy, E.; Rothe, S.

    2017-11-01

    The in-gas laser ionization and spectroscopy (IGLIS) technique was applied on the Ac-215212 isotopes, produced at the Leuven Isotope Separator On-Line (LISOL) facility by using the in-gas-cell and the in-gas-jet methods. The first application under on-line conditions of the in-gas-jet laser spectroscopy method showed a superior performance in terms of selectivity, spectral resolution, and efficiency in comparison with the in-gas-cell method. Following the analysis of both experiments, the magnetic-dipole moments for the Ac-215212 isotopes, electric-quadrupole moments and nuclear spins for the Ac,215214 isotopes are presented and discussed. A good agreement is obtained with large-scale nuclear shell-model calculations by using a 208Pb core.

  14. Laser ignition of liquid petroleum gas at elevated pressures

    Science.gov (United States)

    Loktionov, E.; Pasechnikov, N.; Telekh, V.

    2017-11-01

    Recent development of laser spark plugs for internal combustion engines have shown lack of data on laser ignition of fuel mixtures at multi-bar pressures needed for laser pulse energy and focusing optimisation. Methane and hydrogen based mixtures are comparatively well investigated, but propane and butane based ones (LPG), which are widely used in vehicles, are still almost unstudied. Optical breakdown thresholds in gases decrease with pressure increase up to ca. 100 bar, but breakdown is not a sufficient condition for combustion ignition. So minimum ignition energy (MIE) becomes more important for combustion core onset, and its dependency on mixture composition and pressure has several important features. For example, unlike breakdown threshold, is poorly dependent on laser pulse length, at least in pico- and to microsecond range. We have defined experimentally the dependencies of minimum picosecond laser pulse energies (MIE related value) needed for ignition of LPG based mixtures of 1.0 to 1.6 equivalence ratios and pressure of 1.0 to 3.5 bar. In addition to expected values decrease, low-energy flammability range broadening has been found at pressure increase. Laser ignition of LPG in Wankel rotary engine is reported for the first time.

  15. Laser gas assisted treatment of steel 309: Corrosion and scratch resistance of treated surface

    Science.gov (United States)

    Toor, Ihsan-ul-Haq; Yilbas, B. S.; Ahmed, Junaid; Karatas, C.

    2017-10-01

    Laser gas assisted surface treatment of steel 309 is carried out and the characteristics of the resulting surface are analyzed using the analytical tools. Scanning electron and 3-D optical microscopes are used to assess the morphological and metallurgical changes in the laser treated layer. Energy spectroscopy and X-ray diffraction are carried out to determine the elemental composition and compounds formed on the laser treated surface. The friction coefficient of the laser treated surface is measured using the micro-tribometer and compared to that of the as received surface. The corrosion resistance of the laser treated and as received surfaces is measured incorporating the electrochemical tests. It is found that laser treatment results in a dense layer and formation of nitride compounds at the surface. This enhances the microhardness at the laser treated surface. The friction coefficient attains lower values at the laser treated surface than that corresponding to the as received surface. The corrosion rate of the surface reduces significantly after the laser treatment process, which can be attributed to the passive layer at the surface via formation of a dense layer and nitride compounds in the surface vicinity. In addition, the number of pit sites decreased for the laser treated surface than that of as received surface.

  16. Computer simulations of a single-laser double-gas-jet wakefield accelerator concept

    Directory of Open Access Journals (Sweden)

    R. G. Hemker

    2002-04-01

    Full Text Available We report in this paper on full scale 2D particle-in-cell simulations investigating laser wakefield acceleration. First we describe our findings of electron beam generation by a laser propagating through a single gas jet. Using realistic parameters which are relevant for the experimental setup in our laboratory we find that the electron beam resulting after the propagation of a 0.8 μm, 50 fs laser through a 1.5 mm gas jet has properties that would make it useful for further acceleration. Our simulations show that the electron beam is generated when the laser exits the gas jet, and the properties of the generated beam, especially its energy, depend only weakly on most properties of the gas jet. We therefore propose to use the first gas jet as a plasma cathode and then use a second gas jet placed immediately behind the first to provide additional acceleration. Our simulations of this proposed setup indicate the feasibility of this idea and also suggest ways to optimize the quality of the resulting beam.

  17. High-power gas-discharge excimer ArF, KrCl, KrF and XeCl lasers utilising two-component gas mixtures without a buffer gas

    Science.gov (United States)

    Razhev, A. M.; Kargapol'tsev, E. S.; Churkin, D. S.

    2016-03-01

    Results of an experimental study of the influence of a gas mixture (laser active medium) composition on an output energy and total efficiency of gas-discharge excimer lasers on ArF* (193 nm), KrCl* (222 nm), KrF* (248 nm) and XeCl* (308 nm) molecules operating without a buffer gas are presented. The optimal ratios of gas components (from the viewpoint of a maximum output energy) of an active medium are found, which provide an efficient operation of laser sources. It is experimentally confirmed that for gas-discharge excimer lasers on halogenides of inert gases the presence of a buffer gas in an active medium is not a necessary condition for efficient operation. For the first time, in two-component gas mixtures of repetitively pulsed gas-discharge excimer lasers on electron transitions of excimer molecules ArF*, KrCl*, KrF* and XeCl*, the pulsed energy of laser radiation obtained under pumping by a transverse volume electric discharge in a low-pressure gas mixture without a buffer gas reached up to 170 mJ and a high pulsed output power (of up to 24 MW) was obtained at a FWHM duration of the KrF-laser pulse of 7 ns. The maximal total efficiency obtained in the experiment with two-component gas mixtures of KrF and XeCl lasers was 0.8%.

  18. Diode laser MIR-DFG spectrometer for trace gas detection

    Science.gov (United States)

    Willer, Ulrike; Blanke, Torsten; Schade, Wolfgang

    1996-10-01

    Two cw-single mode diode-lasers with powers of 30 and 50 mW at the center wavelengths 682 and 791 nm are applied as signal and pump sources for difference frequency generation (DFG) in an AgGaS2 crystal with a length of 30 mm. For 90 degree type I phase matching tunable mid-infrared laser radiation is obtained in the spectral range between 4.9 and 5.1 micrometers , while the DFG-output power is 0.2 (mu) W. The performance of this diode-laser MIR-DFG spectrometer is shown as the absorption of CO for the P(28) rotational line around 2023 cm-1 is probed in a cell and on-line in the exhaust of an engine.

  19. In-gas-cell laser ionization studies of plutonium isotopes at IGISOL

    Science.gov (United States)

    Pohjalainen, I.; Moore, I. D.; Kron, T.; Raeder, S.; Sonnenschein, V.; Tomita, H.; Trautmann, N.; Voss, A.; Wendt, K.

    2016-06-01

    In-gas-cell resonance laser ionization has been performed on long-lived isotopes of Pu at the IGISOL facility, Jyväskylä. This initiates a new programme of research towards high-resolution optical spectroscopy of heavy actinide elements which can be produced in sufficient quantities at research reactors and transported to facilities elsewhere. In this work a new gas cell has been constructed for fast extraction of laser-ionized elements. Samples of 238-240,242Pu and 244Pu have been evaporated from Ta filaments, laser ionized, mass separated and delivered to the collinear laser spectroscopy station. Here we report on the performance of the gas cell through studies of the mass spectra obtained in helium and argon, before and after the radiofrequency quadrupole cooler-buncher. This provides valuable insight into the gas phase chemistry exhibited by Pu, which has been additionally supported by measurements of ion time profiles. The resulting monoatomic yields are sufficient for collinear laser spectroscopy. A gamma-ray spectroscopic analysis of the Pu samples shows a good agreement with the assay provided by the Mainz Nuclear Chemistry department.

  20. Characterization of plasmas produced by laser-gas jet interaction

    International Nuclear Information System (INIS)

    Malka, V.; Faure, J.; Amiranoff, F.

    2001-01-01

    An experiment has been performed with one of the six nanosecond beams of the Laboratoire pour l'Utilisation des Lasers Intenses laser facility in order to create long scale uniform plasmas over a wide range of electron density (1x10 19 -1.6x10 20 cm -3 ) and electron temperature (0.5-1.3 keV). Electron density and temperature evolution have been measured using Thomson scattering. Numerical simulations obtained by using a simple model are presented. Scaling law related electron density and electron temperature have been established in agreement with experimental data

  1. Ionization processes in combined high-voltage nanosecond - laser discharges in inert gas

    Science.gov (United States)

    Starikovskiy, Andrey; Shneider, Mikhail; PU Team

    2016-09-01

    Remote control of plasmas induced by laser radiation in the atmosphere is one of the challenging issues of free space communication, long-distance energy transmission, remote sensing of the atmosphere, and standoff detection of trace gases and bio-threat species. Sequences of laser pulses, as demonstrated by an extensive earlier work, offer an advantageous tool providing access to the control of air-plasma dynamics and optical interactions. The avalanche ionization induced in a pre-ionized region by infrared laser pulses where investigated. Pre-ionization was created by an ionization wave, initiated by high-voltage nanosecond pulse. Then, behind the front of ionization wave extra avalanche ionization was initiated by the focused infrared laser pulse. The experiment was carried out in argon. It is shown that the gas pre-ionization inhibits the laser spark generation under low pressure conditions.

  2. [INVITED] Laser gas assisted treatment of Ti-alloy: Analysis of surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Karatas, C.

    2016-04-01

    Laser gas assisted treatment of Ti6Al4V alloy surface is carried out and nitrogen/oxygen mixture with partial pressure of PO2/PN2=1/3 is introduced during the surface treatment process. Analytical tools are used to characterize the laser treated surfaces. The fracture toughness at the surface and the residual stress in the surface region of the laser treated layer are measured. Scratch tests are carried out to determine the friction coefficient of the treated surface. It is found that closely spaced regular laser scanning tracks generates a self-annealing effect in the laser treated layer while lowering the stress levels in the treated region. Introducing high pressure gas mixture impingement at the surface results in formation of oxide and nitride species including, TiO, TiO2, TiN and TiOxNy in the surface region. A dense layer consisting of fine size grains are formed in the surface region of the laser treated layer, which enhances the microhardness at the surface. The fracture toughness reduces after the laser treatment process because of the microhardness enhancement at the surface. The residual stress formed is comprehensive, which is in the order of -350 MPa.

  3. Gas-Filled Targets to Study Laser Backscatter on the National Ignition Facility

    Science.gov (United States)

    London, R. A.; Williams, E. A.; Hinkel, D. E.; Moody, J. D.; Suter, L. J.

    2009-11-01

    To achieve indirect drive fusion at the National Ignition Facility (NIF), laser beams must propagate through several millimeters of high-density plasma to reach the hohlraum walls. Stimulated Brillouin and Raman backscatter could create problems with energetics and/or symmetry. Laser backscatter at NIF will be diagnosed with full aperture backscatter systems (FABS) and near backscatter imagers (NBI). Several gas-filled targets (``gas pipes'') have been designed to provide backscatter sources to commission the diagnostics. The 7-mm long gas pipes are filled with various gases, including C5H12 and CO2, and are irradiated by a NIF quad with 16 kJ of energy in 2-4 ns pulses. We describe the design of the gas pipes using hydrodynamics and laser-plasma-interaction computer codes. The relationship between the design parameters (gas composition and density and laser pulse shape) and the character of the backscatter (Brillouin versus Raman and narrow versus broad angle) are discussed. Comparisons of predicted and measured backscatter distributions and levels are discussed.

  4. Initiation of long, free-standing z discharges by CO2 laser gas heating

    Science.gov (United States)

    Niemann, C.; Tauschwitz, A.; Penache, D.; Neff, S.; Knobloch, R.; Birkner, R.; Presura, R.; Hoffmann, D. H. H.; Yu, S. S.; Sharp, W. M.

    2002-01-01

    High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beam fusion reactor. At the Gesellschaft für Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia (NH3) gas are initiated by a CO2 laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the v2 vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high current discharge was investigated. This article describes the laser-gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge.

  5. Influence of the atomic mass of the background gas on laser ablation plume propagation

    DEFF Research Database (Denmark)

    Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

    2008-01-01

    A combination of time-of-flight ion probe measurements and gas dynamical modeling has been used to investigate the propagation of a laser ablation plume in gases of different atomic/molecular weight. The pressure variation of the ion time-of-flight was found to be well described by the gas...... dynamical model of Predtechensky and Mayorov (Appl. Supercond. 1:2011, 1993). In particular, the model describes how the pressure required to stop the plume in a given distance depends on the atomic/molecular weight of the gas, which is a feature that cannot be explained by standard point......-blast-wave descriptions of laser ablation plume expansion in gas....

  6. 450-nm GaN laser diode enables high-speed visible light communication with 9-Gbps QAM-OFDM.

    Science.gov (United States)

    Chi, Yu-Chieh; Hsieh, Dan-Hua; Tsai, Cheng-Ting; Chen, Hsiang-Yu; Kuo, Hao-Chung; Lin, Gong-Ru

    2015-05-18

    A TO-38-can packaged Gallium nitride (GaN) blue laser diode (LD) based free-space visible light communication (VLC) with 64-quadrature amplitude modulation (QAM) and 32-subcarrier orthogonal frequency division multiplexing (OFDM) transmission at 9 Gbps is preliminarily demonstrated over a 5-m free-space link. The 3-dB analog modulation bandwidth of the TO-38-can packaged GaN blue LD biased at 65 mA and controlled at 25°C is only 900 MHz, which can be extended to 1.5 GHz for OFDM encoding after throughput intensity optimization. When delivering the 4-Gbps 16-QAM OFDM data within 1-GHz bandwidth, the error vector magnitude (EVM), signal-to-noise ratio (SNR) and bit-error-rate (BER) of the received data are observed as 8.4%, 22.4 dB and 3.5 × 10(-8), respectively. By increasing the encoded bandwidth to 1.5 GHz, the TO-38-can packaged GaN blue LD enlarges its transmission capacity to 6 Gbps but degrades its transmitted BER to 1.7 × 10(-3). The same transmission capacity of 6 Gbps can also be achieved with a BER of 1 × 10(-6) by encoding 64-QAM OFDM data within 1-GHz bandwidth. Using the 1.5-GHz full bandwidth of the TO-38-can packaged GaN blue LD provides the 64-QAM OFDM transmission up to 9 Gbps, which successfully delivers data with an EVM of 5.1%, an SNR of 22 dB and a BER of 3.6 × 10(-3) passed the forward error correction (FEC) criterion.

  7. Measurement of gas flow velocities by laser-induced gratings

    Energy Technology Data Exchange (ETDEWEB)

    Hemmerling, B.; Stampanoni-Panariello, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Kozlov, A.D.N. [General Physics Institute, Moscow (Russian Federation)

    1999-08-01

    Time resolved light scattering from laser-induced electrostrictive gratings was used for the determination of flow velocities in air at room temperature. By measuring the velocity profile across the width of a slit nozzle we demonstrated the high spatial resolution (about 200 mm) of this novel technique. (author) 3 figs., 1 ref.

  8. Tissue ablation and gas formation of two excimer laser systems: an in vitro evaluation on porcine aorta.

    Science.gov (United States)

    Appelman, Y E; Piek, J J; Verhoofstad, G G; Gijsbers, G H; Van Gemert, M J

    1996-01-01

    The relationship between tissue ablation volume and the formation of insoluble gas of the currently available excimer laser systems is unknown. This aspect was evaluated in two excimer laser systems. We measured tissue ablation volume and gas production of two excimer laser systems (308 nm) on porcine aortic tissue immersed in saline (the CVX-300 using 1.4 and 1.7 mm laser catheters and the Dymer 200 + using 1.3, 1.3z and 1.6 mm laser catheters). Tissue ablation volume and gas production increased proportionally with the applied energy fluence, ranging from 30-60 mJ/mm2. The gas production per unit of ablated tissue volume of the 1.4 mm laser catheter was significantly higher than the 1.3 mm laser catheter (mean difference +117%, 95% CI from +64% till +188%, PCVX-300 laser system results in significantly higher gas production than the Dymer 200+ laser system, which can be markedly reduced by lowering the applied energy fluence. The 1.3z laser catheter constitutes an exception, showing similar characteristics as the CVX-300 laser catheters.

  9. Enhanced transduction of photonic crystal dye lasers for gas sensing via swelling polymer film

    DEFF Research Database (Denmark)

    Smith, Cameron; Lind, Johan Ulrik; Christiansen, Mads Brøkner

    2011-01-01

    We present the enhanced transduction of a photonic crystal dye laser for gas sensing via deposition of an additional swelling polymer film. Device operation involves swelling of the polymer film during exposure to specific gases, leading to a change in total effective refractive index. Experimental...... in its application to other intracavity-based detection schemes to enable gas sensing. © 2011 Optical Society of America....

  10. Tissue ablation and gas formation of two excimer laser systems: an in vitro evaluation on porcine aorta

    NARCIS (Netherlands)

    Appelman, Y. E.; Piek, J. J.; Verhoofstad, G. G.; Gijsbers, G. H.; van Gemert, M. J.

    1996-01-01

    BACKGROUND and The relationship between tissue ablation volume and the formation of insoluble gas of the currently available excimer laser systems is unknown. This aspect was evaluated in two excimer laser systems. STUDY DESIGN/MATERIALS and We measured tissue ablation volume and gas production of

  11. Soft x-ray emission characteristics from laser produced plasmas using a double stream gas-puff nozzle

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Masayuki; Yamagami, Susumu; Mima, Kunioki [Osaka Univ., Institute of Laser Engineering, Suita, Osaka (Japan); Daido, Hiroyuki; Oketa, Takatsugu [Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan). Kansai Research Establishment; Fiedorowicz, Henrky; Bartnik, Andrzej [Military University of Technology, Institute of Optoelectronics, Kaliskiego, Warsaw (Poland); Nakayama, Takeyoshi [Kinki Univ., School of Science and Engineering, Osaka (Japan)

    2001-10-01

    We characterize a laser produced double-stream gas puff plasma for soft x-ray generation. The double-stream nozzle gas puff target could suppress sideway gas expansion by surrounding the gas from the outer nozzle. Therefore, the x-ray emission from a double nozzle Xe gas-puff target irradiated by a nano-second laser pulse is as strong as that using a solid target. In addition the x-ray source size is smaller than ordinary gas puff plasma. (author)

  12. Modeling pulsed excitation for gas-phase laser diagnostics

    International Nuclear Information System (INIS)

    Settersten, Thomas B.; Linne, Mark A.

    2002-01-01

    Excitation dynamics for pulsed optical excitation are described with the density-matrix equations and the rate equations for a two-level system. A critical comparison of the two descriptions is made with complete and consistent formalisms that are amenable to the modeling of applied laser-diagnostic techniques. General solutions, resulting from numerical integration of the differential equations describing the excitation process, are compared for collisional conditions that range from the completely coherent limit to the steady-state limit, for which the two formalisms are identical. This analysis demonstrates the failure of the rate equations to correctly describe the transient details of the excitation process outside the steady-state limit. However, reasonable estimates of the resultant population are obtained for nonsaturating (linear) excitation. This comparison provides the laser diagnostician with the means to evaluate the appropriate model for excitation through a simple picture of the breakdown of the rate-equation validity

  13. Mode composition of radiation from waveguide gas lasers

    Energy Technology Data Exchange (ETDEWEB)

    Il' in, A.V.; Kozel, S.M.

    1979-06-01

    Calculations are made of the mode composition of radiation emerging from a waveguide laser. Allowance is made for all types of resonator losses and also for a spatially inhomogeneous distribution of the population inversion. Using a two-mode model, it is shown that a transverse inhomogeneity of the inversion results in efficient filtering of higher-order modes even in the case of identical diffraction losses for the different modes.

  14. Experimental investigation of CFRP cutting with nano second laser under air and Ar gas ambience

    Science.gov (United States)

    Sato, Yuji; Tsukamoto, Masahiro; Matsuoka, Fumihiro; Yamashita, Kensuke; Takahashi, Kenjiro; Masuno, Shinichiro

    2015-03-01

    A carbon fiber reinforced plastic (CFRP) is widely used for automobile, aircraft and so on, because of having high strength, lightweight and weather resistance. A laser is one of useful tools for cutting CFRP. However, a matrix evaporated zone (MEZ) is formed around the laser irradiation area since heat property of the resin is different from that of carbon fiber. It is required for optimizing the laser processing condition to minimize the MEZ. In our experiment, the CFRP plate was cut with a nanosecond laser under air and Ar gas ambience. The ambient gas is an important factor for reduction of MEZ since formation of MEZ might be caused due to an oxidization of carbon fiber and epoxy resin. In order to evaluate the oxidization, spectroscopic analysis was carried out to investigate an ablation plume under air and Ar gas. Furthermore, a surface on CFRP plate was observed with a scanning electron microscope (SEM). As the results, the cutting quality for argon is better than that for air, and the MEZ for Ar gas is smaller than than that for air.

  15. Direct evidence of gas-induced laser beam smoothing in the interaction with thin foils

    Czech Academy of Sciences Publication Activity Database

    Benocci, R.; Batani, D.; Dezulian, R.; Redaelli, R.; Lucchini, G.; Canova, F.; Stabile, H.; Fauré, J.; Krouský, Eduard; Mašek, Karel; Pfeifer, Miroslav; Skála, Jiří; Dudžák, Roman; Koenig, M.; Tikhonchuk, V.; Nicolai, Ph.; Malka, V.

    2009-01-01

    Roč. 16, č. 1 (2009), 012703/1-012703/5 ISSN 1070-664X R&D Projects: GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z10100523 Keywords : foils * ionisation * plasma heating by laser * plasma shock waves Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.475, year: 2009

  16. Development of CO2 and KrF gas lasers as drivers for inertial confinement fusion

    International Nuclear Information System (INIS)

    Rockwood, S.D.

    1983-01-01

    Several different driver systems are currently under development in the national ICF program. Los Alamos has traditionally emphasized gas laser systems because of their intrinsic high average power capability and ease of operation. This paper will review the status of activities in both carbon dioxide (CO 2 ) and krypton fluoride (KrF) development at the Laboratory

  17. Fireworks in noble gas clusters a first experiment with the new "free-electron laser"

    CERN Multimedia

    2002-01-01

    An international group of scientists has published first experiments carried out using the new soft X-ray free-electron laser (FEL) at the research center DESY in Hamburg, Germany. Using small clusters of noble gas atoms, for the first time, researchers studied the interaction of matter with intense X-ray radiation from an FEL on extremely short time scales (1 page).

  18. Selective Laser Melting of Hot Gas Turbine Components: Materials, Design and Manufacturing Aspects

    DEFF Research Database (Denmark)

    Goutianos, Stergios

    2017-01-01

    Selective Laser Melting (SLM) allows the design and manufacturing of novel parts and structures with improved performance e.g. by incorporating complex and more efficient cooling schemes in hot gas turbine parts. In contrast to conventional manufacturing of removing material, with SLM parts...

  19. Monte Carlo description of gas flow from laser-evaporated silver

    DEFF Research Database (Denmark)

    Ellegaard, O.; Schou, Jørgen; Urbassek, H.M.

    1999-01-01

    at times t much greater than tau(laser), and this demonstrates that at these later times, the collisions in the plume efficiently smear out the characteristics of the varying temperature at the surface during ablation. The physical properties of the gas flow are determined by the mean thermal energy...

  20. Liquid jet formation through the interactions of a laser-induced bubble and a gas bubble

    Directory of Open Access Journals (Sweden)

    Bing Han

    2017-10-01

    Full Text Available The mechanisms of the liquid jet formation from the interaction of the laser-induced and gas bubble pair are investigated and compared with the jet formation from the interaction of the laser-induced anti-phase bubble pair. The strobe photography experimental method and numerical simulations are implemented to obtain the parameter space of the optimum liquid jet, i.e. highest speed and lowest diameter. It is found that due to the enhanced “catapult effect”, which is induced by the protrusion of the first bubble into the second bubble and the flip back of the elongated part of the first bubble, the optimum liquid jet of the second bubble of the laser-induced anti-phase bubble pair compared to that of the laser-induced and gas bubble pair is 54 %, 65 % and 11 % faster in speed, and 4 %, 44 % and 64 % smaller in diameter, for the 500 μm, 50 μm and 5 μm sized bubbles, respectively. The optimum dimensionless distance for the optimum jet of the laser-induced and the gas bubble is around 0.7, when the maximum bubble radius increases from ∼ 5μm to ∼500 μm, which is different from the laser-induced anti-phase bubble pairs. Besides, the optimum jet of the laser-induced bubble appeared when the bubbles are equal sized, while that of the gas bubble is independent of the relative bubble size, i.e. the liquid jet of the gas bubble has higher robustness in real liquid jet assisted applications when the laser-induced bubble size varies. However, the jet of bubble 2 could maintain a high speed (20 m/s - 35 m/s and a low diameter (∼5 % of the maximum bubble diameter over a big range of the dimensionless distance (0.6 - 0.9 for both of the 50 μm and 500 μm sized laser-induced equal sized anti-phase bubble pairs.

  1. Liquid jet formation through the interactions of a laser-induced bubble and a gas bubble

    Science.gov (United States)

    Han, Bing; Liu, Liu; Zhao, Xiong-Tao; Ni, Xiao-Wu

    2017-10-01

    The mechanisms of the liquid jet formation from the interaction of the laser-induced and gas bubble pair are investigated and compared with the jet formation from the interaction of the laser-induced anti-phase bubble pair. The strobe photography experimental method and numerical simulations are implemented to obtain the parameter space of the optimum liquid jet, i.e. highest speed and lowest diameter. It is found that due to the enhanced "catapult effect", which is induced by the protrusion of the first bubble into the second bubble and the flip back of the elongated part of the first bubble, the optimum liquid jet of the second bubble of the laser-induced anti-phase bubble pair compared to that of the laser-induced and gas bubble pair is 54 %, 65 % and 11 % faster in speed, and 4 %, 44 % and 64 % smaller in diameter, for the 500 μm, 50 μm and 5 μm sized bubbles, respectively. The optimum dimensionless distance for the optimum jet of the laser-induced and the gas bubble is around 0.7, when the maximum bubble radius increases from ˜ 5μm to ˜500 μm, which is different from the laser-induced anti-phase bubble pairs. Besides, the optimum jet of the laser-induced bubble appeared when the bubbles are equal sized, while that of the gas bubble is independent of the relative bubble size, i.e. the liquid jet of the gas bubble has higher robustness in real liquid jet assisted applications when the laser-induced bubble size varies. However, the jet of bubble 2 could maintain a high speed (20 m/s - 35 m/s) and a low diameter (˜5 % of the maximum bubble diameter) over a big range of the dimensionless distance (0.6 - 0.9) for both of the 50 μm and 500 μm sized laser-induced equal sized anti-phase bubble pairs.

  2. Laser-induced breakdown ignition in a gas fed two-stroke engine

    Science.gov (United States)

    Loktionov, E. Y.; Pasechnikov, N. A.; Telekh, V. D.

    2018-01-01

    Laser-induced ignition for internal combustion engines is investigated intensively after demonstration of a compact ‘laser plug’ possibility. Laser spark benefits as compared to traditional spark plugs are higher compression rate, and possibility of almost any fuel ignition, so lean mixtures burning with lower temperatures could reduce harmful exhausts (NO x , CH, etc). No need in electrode and possibility for multi-point, linear or circular ignition can make combustion even more effective. Laser induced combustion wave appears faster and is more stable in time, than electric one, so can be used for ramjets, chemical thrusters, and gas turbines. To the best of our knowledge, we have performed laser spark ignition of a gas fed two-stroke engine for the first time. Combustion temperature and pressure, exhaust composition, ignition timing were investigated at laser and compared to a regular electric spark ignition in a two-stroke model engine. Presented results show possibility for improvement of two-stroke engines performance, in terms of rotation rate increase and NO x emission reduction. Such compact engines using locally mined fuel could be highly demanded in remote Arctic areas.

  3. Monolithic wide tunable laser diodes for gas sensing at 2100 nm

    Science.gov (United States)

    Koslowski, Nicolas; Heger, Andreas; Roessner, Karl; Legge, Michael; Koeth, Johannes; Hildebrandt, Lars

    2013-03-01

    Novel monolithic widely tunable laser diodes in the 2.1μm wavelength region based on GaSb / AlGaAsSb are presented. Using the concept of a lateral binary superimposed (BSG) grating structures and multisegment Verniertuning, stable single-mode output is realized at discrete wavelength channels in the 2060 nm - 2140 nm region. A total tuning above 80 nm in six channels is demonstrated. In every wavelength channel, the output wavelength can be tuned by current and temperature. Each wavelength channel offers up to 6 nm of mode hop free tuning, making this novel widely tunable laser highly attractive as a monolithic light source for multiple-gas sensing or liquid detection purposes. The wavelength channels can be arbitrarily placed within the material gain allowing BSG lasers to sweep e.g. over several gas absorption line within 80 nm. Within a wavelength channel, the widely tunable lasers show DFB like spectral performance with average side-mode suppression-ratios above 40 dB, output power of up to 15 mW at 25°C. Also temperature and current tuning coefficients are comparable to those of DFB lasers. This paper will present an overview of laser concept, performance data and applications.

  4. Resonance-enhanced laser-induced plasma spectroscopy: ambient gas effects

    International Nuclear Information System (INIS)

    Lui, S.L.; Cheung, N.H.

    2003-01-01

    When performing laser-induced plasma spectroscopy for elemental analysis, the sensitivity could be significantly enhanced if the plume was resonantly rekindled by a dye laser pulse. The extent of the enhancement was found to depend on the ambient gas. Air, nitrogen, helium, argon and xenon at pressures ranging from vacuum to 1 bar were investigated. In vacuum, the analyte signal was boosted because of reduced cooling, but it soon decayed as the plume freely expanded. By choosing the right ambient gas at the right pressure, the expanding plume could be confined as well as thermally insulated to maximize the analyte signal. For instance, an ambient of 13 mbar xenon yielded a signal-to-noise ratio of 110. That ratio was 53 when the pellet was ablated in air, and decreased further to 5 if the dye laser was tuned off resonance

  5. In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

    Directory of Open Access Journals (Sweden)

    Basseem B. Hallac

    2018-02-01

    Full Text Available The extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt % lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe3O4. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible light using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe2O3 increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe+2.57 for the catalyst with no lanthana and Fe+2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe+2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe+2.57. The findings of this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. The paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities.

  6. UV-visible spectrum of the phenyl radical and kinetics of its reaction with NO in the gas phase

    DEFF Research Database (Denmark)

    Wallington, T.J.; Egsgaard, H.; Nielsen, O.J.

    1998-01-01

    Pulse radiolysis transient UV-visible absorption spectroscopy was used to study the UV-visible absorption spectrum (225-575 nm) of the phenyl radical, C6H5(.), and kinetics of its reaction with NO. Phenyl radicals have a strong broad featureless absorption in the region of 225-340 nm...

  7. DFB lasers at wavelengths in excess of 2300 nm for remote gas sensing

    Science.gov (United States)

    Koeth, J.; Fischer, M.; Legge, M.; Seufert, J.; Werner, R.

    2017-11-01

    Remote gas sensing for atmospheric and environmental studies using single mode emitting semiconductor lasers, e.g. in LIDAR applications has gained wide interest in the last few years. This technique has been brought to sophisticated sensitivity levels and nowadays detection limits are in the range of a few ppb. However, up until recently only semiconductor laser diode sources with wavelengths below 2.3 μm have been available, which inherently limits the detection sensitivity due to the fact that the fundamental absorption band of many gases lies in the spectral range beyond 2.3 μm. With novel distributed feedback laser diodes at wavelengths up to 2.9 μm higher detection sensitivities as compared to currently available laser based sensors are possible.

  8. Enhancement of methane gas sensing characteristics of graphene oxide sensor by heat treatment and laser irradiation.

    Science.gov (United States)

    Assar, Mohammadreza; Karimzadeh, Rouhollah

    2016-12-01

    The present study uses a rapid, easy and practical method for cost-effective fabrication of a methane gas sensor. The sensor was made by drop-casting a graphene oxide suspension onto an interdigital circuit surface. The electrical conductivity and gas-sensing characteristics of the sensor were determined and then heat treatment and in situ laser irradiation were applied to improve the device conductivity and gas sensitivity. Real-time monitoring of the evolution of the device current as a function of heat treatment time revealed significant changes in the conductance of the graphene oxide sensor. The use of low power laser irradiation enhanced both the electrical conductivity and sensing response of the graphene oxide sensor. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Fundamental Studies of Ignition Process in Large Natural Gas Engines Using Laser Spark Ignition

    Energy Technology Data Exchange (ETDEWEB)

    Azer Yalin; Bryan Willson

    2008-06-30

    Past research has shown that laser ignition provides a potential means to reduce emissions and improve engine efficiency of gas-fired engines to meet longer-term DOE ARES (Advanced Reciprocating Engine Systems) targets. Despite the potential advantages of laser ignition, the technology is not seeing practical or commercial use. A major impediment in this regard has been the 'open-path' beam delivery used in much of the past research. This mode of delivery is not considered industrially practical owing to safety factors, as well as susceptibility to vibrations, thermal effects etc. The overall goal of our project has been to develop technologies and approaches for practical laser ignition systems. To this end, we are pursuing fiber optically coupled laser ignition system and multiplexing methods for multiple cylinder engine operation. This report summarizes our progress in this regard. A partial summary of our progress includes: development of a figure of merit to guide fiber selection, identification of hollow-core fibers as a potential means of fiber delivery, demonstration of bench-top sparking through hollow-core fibers, single-cylinder engine operation with fiber delivered laser ignition, demonstration of bench-top multiplexing, dual-cylinder engine operation via multiplexed fiber delivered laser ignition, and sparking with fiber lasers. To the best of our knowledge, each of these accomplishments was a first.

  10. Application of a high-density gas laser target to the physics of x-ray lasers and coronal plasmas

    International Nuclear Information System (INIS)

    Pronko, J.G.; Kohler, D.

    1996-01-01

    An experiment has been proposed to investigate a photopumped x-ray laser approach using a novel, high-density, laser heated supersonic gas jet plasma to prepare the lasant plasma. The scheme uses the He- like sodium 1.10027 nm line to pump the He-like neon 1s-4p transition at 1.10003 nm with the lasing transitions between the n=4 to n=2,3 states and the n=3 to n=2 state at 5.8 nm, 23.0 nm, and 8.2 nm, respectively. The experiment had been proposed in 1990 and funding began Jan. 1991; however circumstances made it impossible to pursue the research over the past 5 years, and it was decided not to pursue the research any further

  11. [Measurement on gas temperature distribution by tunable diode laser absorption spectroscopy].

    Science.gov (United States)

    Li, Ning; Yan, Jian-hua; Wang, Fei; Chi, Yong; Cen, Ke-fa

    2008-08-01

    The technique of tunable diode laser absorption spectroscopy (TDLAS) can be used for gas temperature distribution measurement by scanning multiple gas absorption lines with a tunable diode laser. The fundamental of gas temperature distribution measurement by TDLAS is introduced in the present paper, and the discretization strategy of equation for gas absorption is also given here. Using constrained linear least-square fitting method, the gas temperature distribution can be calculated with the help of physical constraints under the condition of uniform gas concentration and pressure. Based on the spectral parameters of four CO absorption lines near 6330 cm(-1) from HITRAN database, the model of two-temperature distribution at 300 and 600 K with each path length of 55 cm was set up. The effects of relative measurement error and different path length constraints of temperature bins on the gas temperature distribution measurement results were simulated by constrained linear least-square fitting. The results show that the temperature distribution calculation error increases as the relative measurement error rises. A measurement error of 5% could lead to a maximum relative error of 11%, and an average relative error of 2.2% for calculation result. And the weak physical constraints of path length for temperature bins could increase the calculation result error during the process of constrained linear least-square fitting. By setting up the model of two-temperature distribution with gas cells at room temperature as the cold section and in tube furnace as the hot section, the experiment of gas temperature distribution measurement in lab was carried out. Using four absorption lines of CO near 6330 cm(-1) scanned by VCSEL diode laser, and fitting the background laser intensity without absorption by the cubic polynomial to get the baseline signal, the integrals of spectral absorbance for gas temperature distribution measurement can be calculated. The relative calculation

  12. Laser photoacoustic spectroscopy of biosystems gas exchange with the atmosphere

    Science.gov (United States)

    Ageev, B. G.; Ponomarev, Y. N.; Sapozhnikova, V. A.

    1998-10-01

    A response of plants to stress action is characterized by an activation of the respiration process. The CO2 evolution by some plants exposed to elevated concentration of pollutants and pressure decrease is studied using a photoacoustic spectrometer with a CO2 laser. The measurements show a considerable CO2 evolution by all kinds of the test plants. The quantity of CO2 emitted by pea seedlings at 8 kPa, for example, exceeds the control one by about 20 times (24 h after the exposure start). The exposure of pea seedlings to C2H4 and O3 at various concentrations also increases CO2 evolution: the 48-h exposure of test plants to C2H4 (at 0.01 ppm) increases CO2 evolution by approximately 100% with respect to the control plants.

  13. Titanium Matrix Composite Ti/TiN Produced by Diode Laser Gas Nitriding

    Directory of Open Access Journals (Sweden)

    Aleksander Lisiecki

    2015-01-01

    Full Text Available A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808–940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer beads at different heat inputs, different scanning speeds, and different powers of laser beam. The influence of laser nitriding parameters on the quality, shape, and morphology of the surface layers was investigated. It was found that the nitrided surface layers consist of titanium nitride precipitations mainly in the form of dendrites embedded in the titanium alloy matrix. The titanium nitrides are produced as a result of the reaction between molten Ti and gaseous nitrogen. Solidification and subsequent growth of the TiN dendrites takes place to a large extent at the interface of the molten Ti and the nitrogen gas atmosphere. The direction of TiN dendrites growth is perpendicular to the surface of molten Ti. The roughness of the surface layers depends strongly on the heat input of laser nitriding and can be precisely controlled. In spite of high microhardness up to 2400 HV0.2, the surface layers are crack free.

  14. Determination of absorption coefficient based on laser beam thermal blooming in gas-filled tube.

    Science.gov (United States)

    Hafizi, B; Peñano, J; Fischer, R; DiComo, G; Ting, A

    2014-08-01

    Thermal blooming of a laser beam propagating in a gas-filled tube is investigated both analytically and experimentally. A self-consistent formulation taking into account heating of the gas and the resultant laser beam spreading (including diffraction) is presented. The heat equation is used to determine the temperature variation while the paraxial wave equation is solved in the eikonal approximation to determine the temporal and spatial variation of the Gaussian laser spot radius, Gouy phase (longitudinal phase delay), and wavefront curvature. The analysis is benchmarked against a thermal blooming experiment in the literature using a CO₂ laser beam propagating in a tube filled with air and propane. New experimental results are presented in which a CW fiber laser (1 μm) propagates in a tube filled with nitrogen and water vapor. By matching laboratory and theoretical results, the absorption coefficient of water vapor is found to agree with calculations using MODTRAN (the MODerate-resolution atmospheric TRANsmission molecular absorption database) and HITRAN (the HIgh-resolution atmospheric TRANsmission molecular absorption database).

  15. First Results from Laser-Driven MagLIF Experiments on OMEGA: Time Evolution of Laser Gas Heating Using Soft X-Ray Diagnostics

    Science.gov (United States)

    Barnak, D. H.; Betti, R.; Chang, P.-Y.; Davies, J. R.

    2015-11-01

    Magnetized liner inertial fusion (MagLIF) is a promising inertial confinement fusion scheme comprised of three stages: axial magnetization, laser heating of the deuterium -tritium gas fill, and compression of the gas by the liner. To study the physics of MagLIF, a scaled-down version has been designed and implemented on the OMEGA-60 laser. This talk will focus primarily on the heating process of a MagLIF target using a 351-nm laser. A neon-doped deuterium gas capsule was heated using a 2.5-ns square pulse delivering 200 J of laser energy. Spectral analysis of the x-ray emission from the side and the laser entrance hole of the capsule is used to infer the time evolution of the gas temperature. The x-ray spectra for a grid of possible gas temperatures and densities are simulated using Spect3D atomic modeling software. The simulation results are then used to deconvolve the raw signals and obtain density and temperature estimations. A gas temperature lower bound of 100 eV at 1.3 ns after the start of the laser pulse can be inferred from these estimations. The estimations are then compared to 2-D hydrocode modeling. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by DE-FG02-04ER54786 and DE-FC02-04ER54789 (Fusion Science Center).

  16. Influence of Ambient Gas on Laser-Induced Breakdown Spectroscopy of Uranium Metal

    International Nuclear Information System (INIS)

    Zhang Dacheng; Ma Xinwen; Wang Shulong; Zhu Xiaolong

    2015-01-01

    Laser-induced breakdown spectroscopy (LIBS) is regarded as a suitable method for the remote analysis of materials in any phase, even in an environment with high radiation levels. In the present work we used the third harmonic pulse of a Nd:YAG laser for ablation of uranium metal and measured the plasma emission with a fiber-optic spectrometer. The LIBS spectra of uranium metal and their features in different ambient gases (i.e., argon, neon, oxygen, and nitrogen) at atmospheric pressure were studied. Strong continuum spectrum and several hundreds of emission lines from UI and UII were observed. It is found that the continuum spectrum observed in uranium not only comes from bremsstrahlung emission but is also due to the complex spectrum of uranium. The influence of ambient gas and the gas flow rate for ablation of uranium metal was investigated. The experimental results indicate that the intensity of the uranium lines was enhanced in argon and nitrogen. However, the intensity of uranium lines was decreased in oxygen due to the generation of UO and other oxides. The results also showed that the highest intensity of uranium lines were obtained in argon gas with a gas flow rate above 2.5 L/min. The enhanced mechanism in ambient gas and the influence of the gas flow rate were analyzed in this work. (paper)

  17. Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Sonoda, T., E-mail: tetsu@riken.jp [RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wada, M. [RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Tomita, H.; Sakamoto, C.; Takatsuka, T. [Faculty of Engineering, Nagoya University, Nagoya 464-8603 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Furukawa, T. [Department of Physics, Tokyo Metropolitan University, Tokyo 116-8551 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Iimura, H. [Japan Atomic Energy Agency (JAEA), Tokaimura 319-1100 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Ito, Y. [Department of Physics, Tsukuba University, Tsukuba 305-8577 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kubo, T.; Matsuo, Y. [RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Mita, H. [Department of Physics, Tsukuba University, Tsukuba 305-8577 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Naimi, S. [RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Nakamura, S. [Department of Physics, Tsukuba University, Tsukuba 305-8577 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Noto, T. [Faculty of Engineering, Nagoya University, Nagoya 464-8603 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Schury, P. [Department of Physics, Tsukuba University, Tsukuba 305-8577 (Japan); RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Shinozuka, T. [Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-8578 (Japan); and others

    2013-01-15

    A new laser ion source configuration based on resonant photoionization in a gas cell has been developed at RIBF RIKEN. This system is intended for the future PArasitic RI-beam production by Laser Ion-Source (PALIS) project which will be installed at RIKEN’s fragment separator, BigRIPS. A novel implementation of differential pumping, in combination with a sextupole ion beam guide (SPIG), has been developed. A few small scroll pumps create a pressure difference from 1000 hPa–10{sup −3} Pa within a geometry drastically miniaturized compared to conventional systems. This system can utilize a large exit hole for fast evacuation times, minimizing the decay loss for short-lived nuclei during extraction from a buffer gas cell, while sufficient gas cell pressure is maintained for stopping high energy RI-beams. In spite of the motion in a dense pressure gradient, the photo-ionized ions inside the gas cell are ejected with an assisting force gas jet and successfully transported to a high-vacuum region via SPIG followed by a quadrupole mass separator. Observed behaviors agree with the results of gas flow and Monte Carlo simulations.

  18. Thermal blooming effects of gas on laser propagation in a closed tube

    Science.gov (United States)

    Yu, Huahua; Hu, Peng; An, Jianzhu; Zhang, Feizhou

    2015-02-01

    Thermal blooming effect of inner optical path remarkably affects far-field beam quality and energy distributions which should be taken into account in high energy laser (HEL) system. A physical model of thermal blooming is established. Based on the model, numerical simulations are carried out to study both the influences of absorptions of laser energy and tube structures on laser propagation in a closed tube. The natural convection of gas is numerically simulated by computational fluid dynamics (CFD) method. Gas temperature distributions, additional phase differences (APDs), variations of beam quality and drifts of mass center in far-field under different absorptions of laser energy and tube structures (Z-shaped and U-shaped) are compared, respectively. By analysis of numerical simulation results, the switch time of heat conduction and heat convection in gas is distinguished, which significantly affects the variations of beam quality and drifts of mass center in far-field. In addition, it also indicates that less absorption of laser energy improves beam quality and delays the switch time of beam quality between two heat transfer mechanisms. Therefore, it is significant to control the absorptions of laser energy for HEL system in practice. Different tube structures owning different beam paths change the distributions of APDs and thus influence beam quality. APDs of the two horizontal sections are the same (superposition effect) for Z-shaped tube while inverse (compensation effect) for U-shaped tube. It is shown that drifts of mass center in far-field are greatly suppressed for U-shaped tube than that of Z-shaped tube and beam quality is also improved.

  19. Multi-species trace gas analysis with dual-wavelength quantum cascade laser

    Science.gov (United States)

    Jágerská, Jana; Tuzson, Béla; Looser, Herbert; Jouy, Pierre; Hugi, Andreas; Mangold, Markus; Soltic, Patrik; Faist, Jérôme; Emmenegger, Lukas

    2015-04-01

    Simultaneous detection of multiple gas species using mid-IR laser spectroscopy is highly appealing for a large variety of applications ranging from air quality monitoring, medical breath analysis to industrial process control. However, state-of-the-art distributed-feedback (DFB) mid-IR lasers are usually tunable only within a narrow spectral range, which generally leads to one-laser-one-compound measurement strategy. Thus, multi-species detection involves several lasers and elaborate beam combining solutions [1]. This makes them bulky, costly, and highly sensitive to optical alignment, which limits their field deployment. In this paper, we explore an alternative measurement concept based on a dual-wavelength quantum cascade laser (DW-QCL) [2]. Such a laser can emit at two spectrally distinct wavelengths using a succession of two DFB gratings with different periodicities and a common waveguide to produce one output beam. The laser design was optimized for NOx measurements and correspondingly emits single-mode at 5.26 and 6.25 μm. Electrical separation of the respective laser sections makes it possible to address each wavelength independently. Thereby, it is possible to detect NO and NO2 species with one laser using the same optical path, without any beam combining optics, i.e. in a compact and cost-efficient single-path optical setup. Operated in a time-division multiplexed mode, the spectrometer reaches detection limits at 100 s averaging of 0.5 and 1.5 ppb for NO2 and NO, respectively. The performance of the system was validated against the well-established chemiluminescence detection while measuring the NOx emissions on an automotive test-bench, as well as monitoring the pollution at a suburban site. [1] B. Tuzson, K. Zeyer, M. Steinbacher, J. B. McManus, D. D. Nelson, M. S. Zahniser, and L. Emmenegger, 'Selective measurements of NO, NO2 and NOy in the free troposphere using quantum cascade laser spectroscopy,' Atmospheric Measurement Techniques 6, 927-936 (2013

  20. Kinetic analysis of rare gas metastable production and optically pumped Xe lasers

    Science.gov (United States)

    Demyanov, A. V.; Kochetov, I. V.; Mikheyev, P. A.; Azyazov, V. N.; Heaven, M. C.

    2018-01-01

    Optically pumped all-rare-gas lasers use metastable rare gas atoms as the lasing species in mixtures with He or Ar buffer gas. The metastables are generated in a glow discharge, and we report model calculations for the optimal production of Ne*, Ar*, Kr* and Xe*. Discharge efficiency was estimated by solving the Boltzmann equation. Laser efficiency, gain and output power of the CW optically pumped Xe laser were assessed as functions of heavier rare gas content, pressure, optical pump intensity and the optical path length. It was found that, for efficient operation the heavier rare gas content has to be of the order of one percent or less, and the total pressure—in the range 0.3–1.5 atm. Output power and specific discharge power increase approximately linearly with pump intensity over the output range from 300–500 W cm‑2. Ternary mixtures Xe:Ar:He were found to be the most promising. Total laser efficiency was found to be nearly the same for pumping the 2p8 or 2p9 state, reaching 61%–70% for a pump intensity of ~720 W cm‑2 when the Xe fraction was in the range 0.001 ÷ 0.01 and Ar fraction—0.1 ÷ 0.5. However, when the 2p8 state was pumped, the maximum total efficiency occurred at larger pressures than for pumping of the 2p9 state. The discharge power density required to sustain a sufficient Xe* number density was in the range of tens of watts per cubic centimeter for 50% Ar in the mixture.

  1. The Huber’s Method-based Gas Concentration Reconstruction in Multicomponent Gas Mixtures from Multispectral Laser Measurements under Noise Overshoot Conditions

    Directory of Open Access Journals (Sweden)

    V. A. Gorodnichev

    2016-01-01

    Full Text Available Laser gas analysers are the most promising for the rapid quantitative analysis of gaseous air pollution. A laser gas analysis problem is that there are instable results in reconstruction of gas mixture components concentration under real noise in the recorded laser signal. This necessitates using the special processing algorithms. When reconstructing the quantitative composition of multi-component gas mixtures from the multispectral laser measurements are efficiently used methods such as Tikhonov regularization, quasi-solution search, and finding of Bayesian estimators. These methods enable using the single measurement results to determine the quantitative composition of gas mixtures under measurement noise. In remote sensing the stationary gas formations or in laboratory analysis of the previously selected (when the gas mixture is stationary air samples the reconstruction procedures under measurement noise of gas concentrations in multicomponent mixtures can be much simpler. The paper considers a problem of multispectral laser analysis of stationary gas mixtures for which it is possible to conduct a series of measurements. With noise overshoots in the recorded laser signal (and, consequently, overshoots of gas concentrations determined by a single measurement must be used stable (robust estimation techniques for substantial reducing an impact of the overshoots on the estimate of required parameters. The paper proposes the Huber method to determine gas concentrations in multicomponent mixtures under signal overshoot. To estimate the value of Huber parameter and the efficiency of Huber's method to find the stable estimates of gas concentrations in multicomponent stationary mixtures from the laser measurements the mathematical modelling was conducted. Science & Education of the Bauman MSTU 108 The mathematical modelling results show that despite the considerable difference among the errors of the mixture gas components themselves a character of

  2. Enhancement of the vacuum ultraviolet emission from excimer laser-generated plasmas by ambient gas atoms

    Science.gov (United States)

    Mehlman, G.; Chrisey, D. B.; Horwitz, J. S.; Burkhalter, P. G.; Auyeung, R. C. Y.; Newman, D. A.

    1993-11-01

    We have measured the axial (z) and radial (x) distribution of the vacuum ultraviolet emission from excimer laser generated aluminum plasmas in vacuum and in 300 mTorr of argon. The ratio of the radiated line intensities (emission in a gas versus vacuum) on the z axis (i.e., x=0) increased exponentially with distance from the target surface for plasmas generated in a 300 mTorr argon ambient. The absolute line intensities increased linearly with the argon pressure and approximately linearly with the ambient gas atomic cross section when other rare gases were substituted. The line intensity radial distribution was broader for plasmas in argon than in vacuum and the magnitude of the effect increased monotonically with z. The spectral data obtained from plasmas in a gas ambient are discussed in terms of the diffusion of plasma electrons in an ionized gas.

  3. Transport phenomena in non-uniform gas subjected to laser radiation

    Science.gov (United States)

    Chermyaninov, I. V.; Chernyak, V. G.

    2017-04-01

    The paper discusses the theory of transport processes in one-component gas located in capillary subjected to resonant laser radiation and both temperature and pressure gradients. The equations for the kinetic coefficients determining heat- and mass transport in the gas are derived on the basis of modified Boltzmann equations for the excited and unexcited particles. The cross kinetic coefficients satisfy the Onsager reciprocity for all Knudsen numbers and laws of gas particles interaction with each other and with boundary surface of the capillary. Analysis of possible non-equilibrium stationary states of first and second order for the one-component gas in the capillary has been developed on the basis of the Prigogine theorem of stationary states. Equations describing the stationary states in Knudsen limit (Kn >> 1) and slip-flow regime (Kn << 1) were derived.

  4. Diode laser absorption spectroscopy for studies of gas exchange in fruits

    Science.gov (United States)

    Persson, L.; Gao, H.; Sjöholm, M.; Svanberg, S.

    2006-07-01

    Gas exchange in fruits, in particular oxygen transport in apples, was studied non-intrusively using wavelength modulation diode laser absorption spectroscopy at about 761 nm, applied to the strongly scattering intact fruit structure. The applicability of the technique was demonstrated by studies of the influence of the skin to regulate the internal oxygen balance and of cling film in modifying it by observing the response of the signal from the internal oxygen gas to a transient change in the ambient gas concentration. Applications within controlled atmosphere fruit storage and modified atmosphere packaging are discussed. The results suggest that the technique could be applied to studies of a large number of problems concerning gas exchange in foods and in food packaging.

  5. Hollow Core Optical Fiber Gas Lasers: Toward Novel and Practical Systems in Fused Silica

    Science.gov (United States)

    2017-05-18

    release. John Luginsland Hollow-Core Optical Fiber Gas Lasers K. Corwin et al. 16 Fig. 18 (a) The mode- locked Tm/Ho...18. NUMBER OF PAGES 19a.  NAME OF RESPONSIBLE PERSON LUGINSLAND, JOHN 19b.  TELEPHONE NUMBER (Include area code) 703-588-1775 Standard Form 298 (Rev. 8...for public release. John Luginsland FA9550-14-1-0024 Final Report K. Corwin et al. 1 A. Project Summary/Abstract Hollow Core Optical Fiber Gas

  6. Densification behavior of gas and water atomized 316L stainless steel powder during selective laser melting

    Science.gov (United States)

    Li, Ruidi; Shi, Yusheng; Wang, Zhigang; Wang, Li; Liu, Jinhui; Jiang, Wei

    2010-04-01

    The densification during selective laser melting (SLM) process is an important factor determining the final application of SLM-part. In the present work, the densifications under different processing conditions were investigated and the densification mechanisms were elucidated. It was found that the higher laser power, lower scan speed, narrower hatch spacing and thinner layer thickness could enable a much smoother melting surface and consequently a higher densification. The gas atomized powder possessed better densification than water atomized powder, due to the lower oxygen content and higher packing density of gas atomized powder. A large number of regular-shaped pores can be generated at a wider hatch spacing, even if the scanning track is continuous and wetted very well. The densification mechanisms were addressed and the methods for building dense metal parts were also proposed as follows: inhibiting the balling phenomenon, increasing the overlap ratio of scanning tracks and reducing the micro-cracks.

  7. Momentum distributions of selected rare-gas atoms probed by intense femtosecond laser pulses

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses. The cal......We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses....... The calculations are performed by solving the time-dependent Schrödinger equation within the single-active-electron approximation, and focal-volume effects are taken into account by appropriately averaging the results. The resulting momentum distributions are in quantitative agreement with the experimental...

  8. He-Ne and cw CO2 laser long-path systems for gas detection.

    Science.gov (United States)

    Grant, W B

    1986-03-01

    This paper describes the design and testing of a laboratory prototype dual He-Ne laser system for the detection of methane leaks from underground pipelines and solid-waste landfill sites using differential absorption of radiation backscattered from topographic targets. A laboratory-prototype dual cw carbon dioxide laser system also using topographic backscatter is discussed, and measurement results for methanol are given. With both systems, it was observed that the time-varying differential absorption signal was useful in indicating the presence of a gas coming from a nearby source. Limitations to measurement sensitivity, especially the role of speckle and atmospheric turbulence, are described. The speckle results for hard targets are contrasted with those from atmospheric aerosols. The Appendix gives appropriate laser lines and values of absorption coefficients for the hydrazine fuel gases.

  9. CO{sub 2} laser gas assisted nitriding of Ti-6Al-4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S. [KFUPM, Dhahran (Saudi Arabia)]. E-mail: bsyilbas@kfupm.edu.sa; Karatas, C. [Hacettepe University, Ankara (Turkey); Uslan [Gazi University, Ankara (Turkey); Keles, O. [Gazi University, Ankara (Turkey); Usta, I.Y. [Gazi University, Ankara (Turkey); Ahsan, M. [KFUPM, Dhahran (Saudi Arabia)

    2006-10-15

    Laser gas assisted nitriding of Ti-6Al-4V alloy is carried out and nitride compounds formed and their concentration in the surface vicinity are examined. SEM, XRD and XPS are accommodated to examine the nitride layer characteristics. Microhardness across the nitride layer is measured. Temperature field and nitrogen distribution due to laser irradiation pulse is predicted. It is found that the nitride layer appears like golden color; however, it becomes dark gold color once the laser power irradiation is increased. The {delta}-TiN and {epsilon}-TiN are dominant phases in the surface vicinity. The needle like dendrite structure replace with the feathery like structure in the surface region due to high nitrogen concentration. No porous or microcracks are observed in the nitrided layer, except at high power irradiation, in this case, elongated cracks are observed in the surface region where the nitrogen concentration is considerably high.

  10. Monte Carlo description of gas flow from laser-evaporated silver

    DEFF Research Database (Denmark)

    Ellegaard, Ole; SCHOU, J; Urbassek, H

    1999-01-01

    at times t much greater than tau(laser), and this demonstrates that at these later times, the collisions in the plume efficiently smear out the characteristics of the varying temperature at the surface during ablation. The physical properties of the gas flow are determined by the mean thermal energy...... are determined by the mean thermal energy in the initial plume as well as the number of monolayers emitted.......In the present work, we have studied ablation of a silver metal surface with a Nd:YAG laser (355 nm, 0.8 J/cm(2), 6 ns) on the basis of measured data. We have solved the nonlinear heat conduction equation for the laser heating of the system and calculated the varying surface temperature...

  11. Intensification of rare gas halide lasers with application to laser fusion

    International Nuclear Information System (INIS)

    Jacobs, R.R.; Eimerl, D.; Goldhar, J.; Murray, J.R.; Rapoport, W.R.; Schlitt, L.; Swingle, J.C.

    1980-01-01

    The two techniques of backward-wave Raman pulse compression and pulse stacking are reviewed in the context of using KrF lasers as drivers in inertial confinement fusion. Experimental and theoretical results on Raman pulse compression in methane are presented including data on 70 to 75% pump energy extraction by the counter propagating Stokes wave. Results from on-going pulse stacker/Raman compressor experiments are also described, along with future investigations in this general area

  12. Waste Gas And Particulate Control Measures For Laser Cutters In The Automotive Cloth Industry

    Science.gov (United States)

    Ball, R. D.; Kulik, B. F.; Stoncel, R. J.; Tan, S. L.

    1986-11-01

    Demands for greater flexibility and accuracy in the manufacture of automobile trim parts has made single-ply laser cutting an attractive proposition. Lasers are able to cut a large variety of cloth types, from vinyls to velours. Unlike mechanically cut parts, which in the case of velours produce rough edges and dust problems, laster cutting of parts produces smooth edges, fumes and fine particulate. A detailed study of the nature of the laser effluent from a cross section of typical synthetic cloth found in an automotive trim plant was undertaken. Most samples were cut by a fast axial flow, 500 Watt, continuous wave CO2 laser. A 254 mm (10-inch) focussing optics package was used. The width of the kerf varied with the material, and values were determined at between 0.2 and 0.7 mm. Particle size distribution analysis and rates of particulate emission for each cloth were determined. Gases were collected in gas sample bags and analyzed using Fourier transform infrared analysis. Low boiling point organics were collected on activated charcoal tubes, identified on a gas chromatograph mass spectrometer, and quantified on a gas chromatograph. Inorganic contaminants were collected on filter paper and analysed on an inductively coupled plasma atomic emission spectrometer. A number of different effluent control systems were evaluated. Due to the very fine and sticky nature of the particulate, filters capable of removing particulate sizes in the 10 μm or lower range, tend to clog rapidly. Laboratory scale models of wet scrubbers, and electrostatic precipitators were built and tested. The most effective dust and effluent gas control was given by a wet electrostatic precipitator. This system, in conjunction with a scrubber, should maintain emission levels within environmental standards.

  13. Route to Soft X-ray Laser Pumped by Gas-Filled-Capillary Discharge

    Czech Academy of Sciences Publication Activity Database

    Koláček, Karel; Schmidt, Jiří; Prukner, Václav; Řípa, Milan; Frolov, Oleksandr; Štraus, Jaroslav; Vrba, Pavel

    2004-01-01

    Roč. 34, - (2004), s. 154-157 ISSN 1433-5581. [First Cairo Conference on Plasma Physics & Applications. Cairo, 11.10.2003-15.10.2003] R&D Projects: GA ČR(CZ) GA202/03/0711 Grant - others:GA MŠk1(CZ) LA 235 Keywords : fast capillary discharge * soft x-Ray laser Subject RIV: BL - Plasma and Gas Discharge Physics

  14. Design of the energy storage system for the High Energy Gas Laser Facility at LASL

    International Nuclear Information System (INIS)

    Riepe, K.B.; Kircher, M.J.

    1977-01-01

    The Antares laser is being built in the High Energy Gas Laser Facility (HEGLF) at Los Alamos to continue laser fusion experiments at very high power. The laser medium will be pumped by an electrical discharge, which requires an energy input of about 5 MJ in a few microseconds at about 500 kV. The energy storage system which will provide the pulsed power will be a bank of high-voltage pulse-forming networks. Tradeoff studies have been performed comparing the performance of multi-mesh networks with single-mesh networks. The single-mesh network requires about 20% more energy than a two-mesh network, but will tolerate three times the inductance of a two-mesh network. Analysis also shows that amplifier gain is not sensitive to impedance mismatch among the pulse-forming network, the transmission cables, and the gas discharge. A prototype pulse-forming network is being built to test components and trigger performance. It is a Marx generator storing 300 kJ at 1.2 MV open circuit, with 3 μH internal inductance

  15. Numerical investigation of the threshold intensity dependence on gas pressure in the breakdown of xenon by different laser wavelengths

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Abd El Hameid Mahmoud, Mohamed; Dawood, Nagia D. A.

    2014-07-01

    We report a theoretical analysis of the measurements that carried out to study the breakdown of xenon gas over a wide pressure range induced by laser source operating at different wavelengths. The study provided an investigation of the effect of laser wavelength as well as gas pressure on the physical processes associated with this phenomenon. To this aim a modified electron cascade model is applied. The model based on the numerical solution of the time dependent Boltzmann equation for the electron energy distribution function (EEDF) simultaneously with a set of rate equations which describe the rate of change of the formed excited states population. Comparison between the calculated and measured threshold intensities for the experimentally tested laser wavelengths and gas pressure range is obtained. Furthermore computations of the EEDF and its parameters showed the actual correlation between the gain and loss processes which determine the threshold breakdown intensity of xenon and the two experimentally tested parameters; laser wavelength and gas pressure.

  16. Diode Laser Sensor for Gas Temperature and H2O Concentration in a Scramjet Combustor Using Wavelength Modulation Spectroscopy (Postprint)

    National Research Council Canada - National Science Library

    Rieker, Gregory B; Li, Jonathan T; Jeffries, Jay B; Mathur, Tarun; Gruber, Mark R; Carter, Campbell D

    2005-01-01

    A diode laser absorption sensor which probes three spectral features of water vapor in the near infrared region to infer gas temperature and water vapor concentration near the exit of a scramjet combustor is presented...

  17. Trace-gas sensing using the compliance voltage of an external cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.

    2013-06-04

    Quantum cascade lasers (QCLs) are increasingly being used to detect, identify, and measure levels of trace gases in the air. External cavity QCLs (ECQCLs) provide a broadly-tunable infrared source to measure absorption spectra of chemicals and provide high detection sensitivity and identification confidence. Applications include detecting chemical warfare agents and toxic industrial chemicals, monitoring building air quality, measuring greenhouse gases for atmospheric research, monitoring and controlling industrial processes, analyzing chemicals in exhaled breath for medical diagnostics, and many more. Compact, portable trace gas sensors enable in-field operation in a wide range of platforms, including handheld units for use by first responders, fixed installations for monitoring air quality, and lightweight sensors for deployment in unmanned aerial vehicles (UAVs). We present experimental demonstration of a new chemical sensing technique based on intracavity absorption in an external cavity quantum cascade laser (ECQCL). This new technique eliminates the need for an infrared photodetector and gas cell by detecting the intracavity absorption spectrum in the compliance voltage of the laser device itself. To demonstrate and characterize the technique, we measure infrared absorption spectra of chemicals including water vapor and Freon-134a. Sub-ppm detection limits in one second are achieved, with the potential for increased sensitivity after further optimization. The technique enables development of handheld, high-sensitivity, and high-accuracy trace gas sensors for in-field use.

  18. Controlling residual hydrogen gas in mass spectra during pulsed laser atom probe tomography.

    Science.gov (United States)

    Kolli, R Prakash

    2017-01-01

    Residual hydrogen (H 2 ) gas in the analysis chamber of an atom probe instrument limits the ability to measure H concentration in metals and alloys. Measuring H concentration would permit quantification of important physical phenomena, such as hydrogen embrittlement, corrosion, hydrogen trapping, and grain boundary segregation. Increased insight into the behavior of residual H 2 gas on the specimen tip surface in atom probe instruments could help reduce these limitations. The influence of user-selected experimental parameters on the field adsorption and desorption of residual H 2 gas on nominally pure copper (Cu) was studied during ultraviolet pulsed laser atom probe tomography. The results indicate that the total residual hydrogen concentration, H TOT , in the mass spectra exhibits a generally decreasing trend with increasing laser pulse energy and increasing laser pulse frequency. Second-order interaction effects are also important. The pulse energy has the greatest influence on the quantity H TOT , which is consistently less than 0.1 at.% at a value of 80 pJ.

  19. Evaporation-induced gas-phase flows at selective laser melting

    Science.gov (United States)

    Zhirnov, I.; Kotoban, D. V.; Gusarov, A. V.

    2018-02-01

    Selective laser melting is the method for 3D printing from metals. A solid part is built from powder layer-by-layer. A continuum-wave laser beam scans every powder layer to fuse powder. The process is studied with a high-speed CCD camera at the frame rate of 104 fps and the resolution up to 5 µm per pixel. Heat transfer and evaporation in the laser-interaction zone are numerically modeled. Droplets are ejected from the melt pool in the direction around the normal to the melt surface and the powder particles move in the horizontal plane toward the melt pool. A vapor jet is observed in the direction of the normal to the melt surface. The velocities of the droplets, the powder particles, and the jet flow and the mass loss due to evaporation are measured. The gas flow around the vapor jet is calculated by Landau's model of submerged jet. The measured velocities of vapor, droplets, and powder particles correlate with the calculated flow field. The obtained results show the importance of evaporation and the flow of the vapor and the ambient gas. These gas-dynamic phenomena can explain the formation of the denudated zones and the instability at high-energy input.

  20. A Laser Spark Plug Ignition System for a Stationary Lean-Burn Natural Gas Reciprocating Engine

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, D. L. [West Virginia Univ., Morgantown, WV (United States)

    2007-05-01

    To meet the ignition system needs of large bore, high pressure, lean burn, natural gas engines a side pumped, passively Q-switched, Nd:YAG laser was developed and tested. The laser was designed to produce the optical intensities needed to initiate ignition in a lean burn, high compression engine. The laser and associated optics were designed with a passive Q-switch to eliminate the need for high voltage signaling and associated equipment. The laser was diode pumped to eliminate the need for high voltage flash lamps which have poor pumping efficiency. The independent and dependent parameters of the laser were identified and explored in specific combinations that produced consistent robust sparks in laboratory air. Prior research has shown that increasing gas pressure lowers the breakdown threshold for laser initiated ignition. The laser has an overall geometry of 57x57x152 mm with an output beam diameter of approximately 3 mm. The experimentation used a wide range of optical and electrical input parameters that when combined produced ignition in laboratory air. The results show a strong dependence of the output parameters on the output coupler reflectivity, Q-switch initial transmission, and gain media dopant concentration. As these three parameters were lowered the output performance of the laser increased leading to larger more brilliant sparks. The results show peak power levels of up to 3MW and peak focal intensities of up to 560 GW/cm2. Engine testing was performed on a Ricardo Proteus single cylinder research engine. The goal of the engine testing was to show that the test laser performs identically to the commercially available flashlamp pumped actively Q-switched laser used in previous laser ignition testing. The engine testing consisted of a comparison of the in-cylinder, and emissions behavior of the engine using each of the lasers as an ignition system. All engine parameters were kept as constant as possilbe while the equivalence ratio (fueling

  1. Widely tunable Sampled Grating Distributed Bragg Reflector Quantum Cascade laser for gas spectroscopy applications

    Science.gov (United States)

    Diba, Abdou Salam

    Since the advent of semiconductor lasers, the development of tunable laser sources has been subject of many efforts in industry and academia arenas. This interest towards broadly tunable lasers is mainly due to the great promise they have in many applications ranging from telecommunication, to environmental science and homeland security, just to name a few. After the first demonstration of quantum cascade laser (QCL) in the early nineties, QCL has experienced a rapid development, so much so that QCLs are now the most reliable and efficient laser source in the Mid-IR range covering between 3 microm to 30 microm region of the electromagnetic spectrum. QCLs have almost all the desirable characteristics of a laser for spectroscopy applications such as narrow spectral linewidth ideal for high selectivity measurement, high power enabling high sensitivity sensing and more importantly they emit in the finger-print region of most of the trace gases and large molecules. The need for widely tunable QCLs is now more pressing than ever before. A single mode quantum cascade laser (QCL) such as a distributed feedback (DFB) QCL, is an ideal light source for gas sensing in the MIR wavelength range. Despite their performance and reliability, DFB QCLs are limited by their relatively narrow wavelength tuning range determined by the thermal rollover of the laser. An external cavity (EC) QCL, on the other hand, is a widely tunable laser source, and so far is the choice mid-infrared single frequency light sources for detecting multiple species/large molecules. However, EC QCLs can be complex, bulky and expensive. In the quest for finding alternative broadly wavelength tunable sources in the mid-infrared, many monolithic tunable QCLs are recently proposed and fabricated, including SG-DBR, DFB-Arrays, Slot-hole etc. and they are all of potentially of interest as a candidate for multi-gas sensing and monitoring applications, due to their large tuning range (>50 cm-1), and potentially low

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

    Science.gov (United States)

    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.

  3. Laser-based data acquisition in gas centrifuge environments using optical fibers

    International Nuclear Information System (INIS)

    Cates, M.R.; Allison, S.W.; Marshall, B.; Davies, T.J.; Franks, L.A.; Nelson, M.A.; Noel, B.W.

    1984-01-01

    The operating environment of gas centrifuges poses three basic experimental problems: rotating reference frame, corrosive effects of UF 6 gas, and vacuum coupling. Diagnostic experiments in this environment effectively use fiber optics as laser transport systems and data extraction channels. Access to the interior of rotating centrifuges is only from a central nonrotating column assembly. Optical paths are often long and difficult to measure in static conditions with precision necessary in operating conditions. Residual traces of HF gas, from UF 6 , damage exposed optical components over time. Diagnostic measurements requiring pulsed laser sources and analysis of fluorescence emissions, both from UF 6 gas and from temperature-sensitive phosphor are described, with emphasis on optical fiber components and experimental design configurations. The studies were done at Oak Ridge Gaseous Diffusion Plant through the Centrifuge Physics Department of the Centrifuge Division. The advantages of fiber optics methods include: optical path flexibility, small and adaptable size of components, utility in connection with moveable assemblies, and relative ease of vacuum isolation. 3 references, 6 figures

  4. Systematic analysis of DNA damage induction and DNA repair pathway activation by continuous wave visible light laser micro-irradiation

    Directory of Open Access Journals (Sweden)

    Britta Muster

    2017-02-01

    Full Text Available Laser micro-irradiation can be used to induce DNA damage with high spatial and temporal resolution, representing a powerful tool to analyze DNA repair in vivo in the context of chromatin. However, most lasers induce a mixture of DNA damage leading to the activation of multiple DNA repair pathways and making it impossible to study individual repair processes. Hence, we aimed to establish and validate micro-irradiation conditions together with inhibition of several key proteins to discriminate different types of DNA damage and repair pathways using lasers commonly available in confocal microscopes. Using time-lapse analysis of cells expressing fluorescently tagged repair proteins and also validation of the DNA damage generated by micro-irradiation using several key damage markers, we show that irradiation with a 405 nm continuous wave laser lead to the activation of all repair pathways even in the absence of exogenous sensitization. In contrast, we found that irradiation with 488 nm laser lead to the selective activation of non-processive short-patch base excision and single strand break repair, which were further validated by PARP inhibition and metoxyamine treatment. We conclude that these low energy conditions discriminated against processive long-patch base excision repair, nucleotide excision repair as well as double strand break repair pathways.

  5. A (S)TEM Gas Cell Holder with Localized Laser Heating for In Situ Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Mehraeen, Shareghe [Univ. of California, Davis, CA (United States). Dept. of Molecular and Cellular Biology; McKeown, Joseph T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Condensed Matter and Materials Division; Deshmukh, Pushkarraj V. [E.A. Fischione Instruments, Inc., Export, PA (United States); Evans, James E. [Univ. of California, Davis, CA (United States). Dept. of Molecular and Cellular Biology; Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Chemical and Materials Science Division; Abellan, Patricia [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Chemical and Materials Science Division; Xu, Pinghong [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science; Reed, Bryan W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Condensed Matter and Materials Division; Taheri, Mitra L. [Drexel Univ., Philadelphia, PA (United States). Dept. of Materials Science & Engineering; Fischione, Paul E. [E.A. Fischione Instruments, Inc., Export, PA (United States); Browning, Nigel D. [Univ. of California, Davis, CA (United States). Dept. of Molecular and Cellular Biology; Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Chemical and Materials Science Division; Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

    2013-03-04

    We report that the advent of aberration correction for transmission electron microscopy has transformed atomic resolution imaging into a nearly routine technique for structural analysis. Now an emerging frontier in electron microscopy is the development of in situ capabilities to observe reactions at atomic resolution in real time and within realistic environments. Here we present a new in situ gas cell holder that is designed for compatibility with a wide variety of sample type (i.e., dimpled 3-mm discs, standard mesh grids, various types of focused ion beam lamellae attached to half grids). Its capabilities include localized heating and precise control of the gas pressure and composition while simultaneously allowing atomic resolution imaging at ambient pressure. The results show that 0.25-nm lattice fringes are directly visible for nanoparticles imaged at ambient pressure with gas path lengths up to 20 μm. Additionally, we quantitatively demonstrate that while the attainable contrast and resolution decrease with increasing pressure and gas path length, resolutions better than 0.2 nm should be accessible at ambient pressure with gas path lengths less than the 15 μm utilized for these experiments.

  6. Growth by the μ-PD Method and Visible Laser Operation of a Single-Crystal Fiber of Pr3+:KY3F10

    Directory of Open Access Journals (Sweden)

    Jun Shu

    2017-07-01

    Full Text Available We report on the first growth, spectroscopy, and visible laser operation of a single-crystal fiber (SCF of KY3F10 (KYF grown by the micro-pulling-down (μ-PD method, doped with Pr3+ ions. This material has a cubic lattice, which makes it appealing for use in the industry. However, KYF crystals are considered difficult to grow with high optical quality, even with well-established methods. Nevertheless, we grew a 50-mm-long SCF of Pr:KYF, which was transparent in its inner part. We studied the spectroscopic features of it in comparison with existing literature and with samples of the same crystal grown by the Czochralski method, and we did not notice any large differences. These characterizations confirmed that is indeed possible to grow high-quality crystals of Pr:KYF by the μ-PD method. Unfortunately, the crystal proved to be more brittle than typical KYF and especially difficult to polish, leading to rough and irregular facets, as evidenced by transmission measurements. Despite these issues, we obtained continuous-wave laser operation in the orange, red, and deep red regions, using a sample carved from the SCF as active medium and an InGaN-based laser diode as pump source, though with lower performances than in existing reports on this crystal.

  7. Theoretical estimation and experimental studies on gas dissociation in TEA CO2 laser for long term arc free operation

    Science.gov (United States)

    Kumar, Manoj; Biswas, A. K.; Bhargav, Pankaj; Reghu, T.; Sahu, Shashikiran; Pakhare, J. S.; Bhagat, M. S.; Kukreja, L. M.

    2013-11-01

    Gas dissociation in a high energy, high repetition rate Transversely Excited Atmospheric (TEA) CO2 laser in both sealed-off and gas replenishment modes were studied for nitrogen lean gas mixture. A comprehensive theoretical model based on the Boltzmann transport equation and the discharge excitation circuit equations was adopted to calculate the amount of CO2 dissociated during a single discharge pulse. Theoretically it is shown that inclusion of superelastic collisions in the Boltzmann transport equation is necessary for precise estimation of dissociation per pulse, particularly at high discharge energy loadings and for nitrogen rich gas mixtures. Gas lifetime for repetitively pulsed operations was found experimentally by measuring the amount of CO formed when frequent arcing sets in under sealed off operation. Using this model, the optimum replenishment rate of CO2 either by gas purging and/or by catalytic regeneration needed for arc free long term operation of the laser was estimated. The measured saturation values of CO concentration in the laser chamber agreed well with the calculated values for various operating conditions. Arc free, long term repetitively pulsed operation of the laser was achieved in the gas replenishment mode with gas purging and/or catalytic regeneration.

  8. [Experimental investigation of laser plasma soft X-ray source with gas target].

    Science.gov (United States)

    Ni, Qi-liang; Gong, Yan; Lin, Jing-quan; Chen, Bo; Cao, Jian-lin

    2003-02-01

    This paper describes a debris-free laser plasma soft X-ray source with a gas target, which has high operating frequency and can produce strong soft X-ray radiation. The valve of this light source is drived by a piezoelectrical ceramic whose operating frequency is up to 400 Hz. In comparison with laser plasma soft X-ray sources using metal target, the light source is debris-free. And it has higher operating frequency than gas target soft X-ray sources whose nozzle is controlled by a solenoid valve. A channel electron multiplier (CEM) operating in analog mode is used to detect the soft X-ray generated by the laser plasma source, and the CEM's output is fed to to a charge-sensitive preamplifier for further amplification purpose. Output charges from the CEM are proportional to the amplitude of the preamplifier's output voltage. Spectra of CO2, Xe and Kr at 8-14 nm wavelength which can be used for soft X-ray projection lithography are measured. The spectrum for CO2 consists of separate spectral lines originate mainly from the transitions in Li-like and Be-like ions. The Xe spectrum originating mainly from 4d-5f, 4d-4f, 4d-6p and 4d-5p transitions in multiply charged xenon ions. The spectrum for Kr consists of separate spectral lines and continuous broad spectra originating mainly from the transitions in Cu-, Ni-, Co- and Fe-like ions.

  9. Wettability modification of electrospun poly(ε-caprolactone) fibers by femtosecond laser irradiation in different gas atmospheres

    International Nuclear Information System (INIS)

    He Lingna; Chen Jian; Farson, Dave F.; Lannutti, John J.; Rokhlin, Stan I.

    2011-01-01

    The effect of femtosecond laser irradiation in air and in O 2 and CF 4 gas flows on the wettability of electrospun poly(ε-caprolactone) fiber tissue scaffolds was studied. Laser power, focus spot size, raster scan spacing and gas atmosphere were varied in experiments. SEM imaging showed the average fiber diameter and surface porosity sizes were both altered by ablation. The micro-scale surface roughness measured by scanning laser profilometry was found to have a non-monotonic relationship to the surface wettability measured by the contact angle of sessile water droplets. In contrast, surface water contact angle continuously decreased with increased oxygen atomic percentage and oxygen-containing group fraction as measured by XPS. Further, the oxygen content was larger for more extensively ablated fiber surfaces, regardless of whether the increased ablation was caused by high laser power, smaller scanning space or smaller defocusing distance. Of the three gas atmospheres, O 2 gas flow was the most favorable environment for increasing surface oxidization, resulting in the largest water contact angle decrease for given laser power. For CF 4 gas flow, the least oxidization occurred, and the magnitude of water contact angle decrease was smallest for treatment at a given laser power.

  10. Wettability modification of electrospun poly(ɛ-caprolactone) fibers by femtosecond laser irradiation in different gas atmospheres

    Science.gov (United States)

    He, Lingna; Chen, Jian; Farson, Dave F.; Lannutti, John J.; Rokhlin, Stan I.

    2011-02-01

    The effect of femtosecond laser irradiation in air and in O2 and CF4 gas flows on the wettability of electrospun poly(ɛ-caprolactone) fiber tissue scaffolds was studied. Laser power, focus spot size, raster scan spacing and gas atmosphere were varied in experiments. SEM imaging showed the average fiber diameter and surface porosity sizes were both altered by ablation. The micro-scale surface roughness measured by scanning laser profilometry was found to have a non-monotonic relationship to the surface wettability measured by the contact angle of sessile water droplets. In contrast, surface water contact angle continuously decreased with increased oxygen atomic percentage and oxygen-containing group fraction as measured by XPS. Further, the oxygen content was larger for more extensively ablated fiber surfaces, regardless of whether the increased ablation was caused by high laser power, smaller scanning space or smaller defocusing distance. Of the three gas atmospheres, O2 gas flow was the most favorable environment for increasing surface oxidization, resulting in the largest water contact angle decrease for given laser power. For CF4 gas flow, the least oxidization occurred, and the magnitude of water contact angle decrease was smallest for treatment at a given laser power.

  11. Role of arc mode in laser-metal active gas arc hybrid welding of mild steel

    International Nuclear Information System (INIS)

    Li, Geng; Zhang, Chen; Gao, Ming; Zeng, Xiaoyan

    2014-01-01

    Highlights: • Pulsed arc is more effective to improve the stability of laser-arc hybrid welding. • LCHW has the highest fraction of acicular ferrite and high-angle grain boundaries. • Grain refinement depends on effective current of the arc. • LSHW has the most apparent vestige of texture components. • The microstructure and microtexture formation mechanisms were summarized. - Abstract: Arc mode plays an important role in joint characterizations of arc welding, but it has been seldom considered in laser-arc hybrid welding. This paper investigated the role of arc mode on laser-metal active gas (MAG) arc hybrid welding of mild steel. Three arc modes were employed, which were cold metal transfer (CMT), pulsed spray arc and standard short circuiting arc. Microtexture of the joints were observed and measured via electron back scattering diffraction (EBSD) system to reveal the effect of arc mode on microstructure. Mechanical properties of the joints were evaluated by tensile and Charpy V-notch impact tests. It was found that both the stability and mechanical properties of laser-CMT hybrid welding (LCHW) is the best, while those of laser-standard short circuiting arc welding (LSHW) is the worst. OM and EBSD results showed that the fraction of acicular ferrite and high-angle grain boundaries in fusion zone decreases gradually in the sequence of LCHW, laser-pulsed spray arc welding and LSHW, while the mean grain size increases gradually. Finally, the microstructure formation mechanisms and the relationship between microstructure and mechanical properties were summarized by the loss of alloying element and the stirring effect in molten pool

  12. Visible photoassisted room-temperature oxidizing gas-sensing behavior of Sn2S3 semiconductor sheets through facile thermal annealing

    Science.gov (United States)

    Liang, Yuan-Chang; Lung, Tsai-Wen; Wang, Chein-Chung

    2016-11-01

    Well-crystallized Sn2S3 semiconductor thin films with a highly (111)-crystallographic orientation were grown using RF sputtering. The surface morphology of the Sn2S3 thin films exhibited a sheet-like feature. The Sn2S3 crystallites with a sheet-like surface had a sharp periphery with a thickness in a nanoscale size, and the crystallite size ranged from approximately 150 to 300 nm. Postannealing the as-synthesized Sn2S3 thin films further in ambient air at 400 °C engendered roughened and oxidized surfaces on the Sn2S3 thin films. Transmission electron microscopy analysis revealed that the surfaces of the Sn2S3 thin films transformed into a SnO2 phase, and well-layered Sn2S3-SnO2 heterostructure thin films were thus formed. The Sn2S3-SnO2 heterostructure thin film exhibited a visible photoassisted room-temperature gas-sensing behavior toward low concentrations of NO2 gases (0.2-2.5 ppm). By contrast, the pure Sn2S3 thin film exhibited an unapparent room-temperature NO2 gas-sensing behavior under illumination. The suitable band alignment at the interface of the Sn2S3-SnO2 heterostructure thin film and rough surface features might explain the visible photoassisted room-temperature NO2 gas-sensing responses of the heterostructure thin film on exposure to NO2 gas at low concentrations in this work.

  13. Optimization of the electron beam properties from intense laser pulses interacting with structured gas jets

    Science.gov (United States)

    Swanson, K. K.; Tsai, H.-E.; Barber, S. K.; Lehe, R.; Mao, H.-S.; Steinke, S.; van Tilborg, J.; Nakamura, K.; Geddes, C. G. R.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2017-05-01

    Laser plasma acceleration has been intensely investigated for its ability to produce energetic, ultrashort electron bunches in a compact distance. A high intensity laser pulse propagating through a plasma expels the electrons from the optical axis via the ponderomotive force, leaving behind a column of ions and driving a density wake. The accelerating electric fields present in the wake can reach several orders of magnitude greater than those found in radio-frequency cavities, allowing for compact systems much smaller than those using conventional accelerators. This compact source can provide electrons for various applications including stages for a high energy collider or for production of x-ray pulses from coherent undulator radiation. However, these applications require tunable, stable and high-quality electron beams. We report on a study of controlled injection along a shock-induced density downramp of laser-plasma- accelerated electrons through precision tailoring of the density profile produced from a mm-scale gas jet. Using BELLA Center's TREX Ti:Sapphire laser, the effects of the plasma density profile and the tilt of the shock front on the beam spatial profile, steering, and energy were investigated experimentally. To explain these rela- tionships, we propose simple models which agree well with experimental results. Using this technique, electron beam quality was tailored, allowing for the production of high-quality electron beams with percent-level energy spreads over a range of energies.

  14. Numerical investigation of the prospects of high energy laser in drilling oil and gas wells

    International Nuclear Information System (INIS)

    Agha, K.R.; Belhaj, H.A.; Mustafiz, S.; Islam, M.R.; Bjorndalen, N.

    2004-01-01

    Rotary drilling is the primary method used to reach oil and gas formations that was developed over a century ago. Many problems persist with this method, including downtime due to dull bits, the lack of precise vertical or horizontal wells and formation fluid leakage during drilling due to the lack of a seal around the hole. Laser drilling is a new technology that has been proposed as a method to eliminate the current problems while drilling and provide a less expensive alternative to conventional methods. This paper discussed the development of a numerical model based on the fundamental heat transfer and fluid flow phenomena including conduction, melting and vaporization responsible for material removal by laser drilling process. The paper addressed the thermal process involved in laser drilling of sandstone and limestone rocks as well as aluminum and mild steel. The paper outlined the parametric study and discussed the design considerations for a field application. Economical and environmental impacts were also included. It was concluded that more experimental investigation is needed to fully understand the laser operation and to enhance the integrity of the numerical models. In addition, it was concluded that field equipment must be designed to meet the changes in drilling requirements. 19 refs., 10 figs

  15. Modeled occupational exposures to gas-phase medical laser-generated air contaminants.

    Science.gov (United States)

    Lippert, Julia F; Lacey, Steven E; Jones, Rachael M

    2014-01-01

    Exposure monitoring data indicate the potential for substantive exposure to laser-generated air contaminants (LGAC); however the diversity of medical lasers and their applications limit generalization from direct workplace monitoring. Emission rates of seven previously reported gas-phase constituents of medical laser-generated air contaminants (LGAC) were determined experimentally and used in a semi-empirical two-zone model to estimate a range of plausible occupational exposures to health care staff. Single-source emission rates were generated in an emission chamber as a one-compartment mass balance model at steady-state. Clinical facility parameters such as room size and ventilation rate were based on standard ventilation and environmental conditions required for a laser surgical facility in compliance with regulatory agencies. All input variables in the model including point source emission rates were varied over an appropriate distribution in a Monte Carlo simulation to generate a range of time-weighted average (TWA) concentrations in the near and far field zones of the room in a conservative approach inclusive of all contributing factors to inform future predictive models. The concentrations were assessed for risk and the highest values were shown to be at least three orders of magnitude lower than the relevant occupational exposure limits (OELs). Estimated values do not appear to present a significant exposure hazard within the conditions of our emission rate estimates.

  16. Creation of Pure Frozen Gas Targets for Ion Acceleration using Short Pulse Lasers

    Science.gov (United States)

    McCary, Edward; Stehr, Florian; Jiao, Xuejing; Quevedo, Hernan; Franke, Philip; Agustsson, Ronald; Oshea, Finn; Berry, Robert; Chao, Dennis; Woods, Kayley; Gautier, Donald; Letzring, Sam; Hegelich, Bjorn

    2015-11-01

    A system for shooting interchangeable frozen gas targets was developed at the University of Texas and will be tested at Los Alamos National Lab. A target holder which can hold up to five substrates used for target growing was cryogenically cooled to temperatures below 14 K. The target substrates consist of holes with diameters ranging from 15 μm-500 μm and TEM grids with micron scale spacing, across which films of ice are frozen by releasing small amounts of pure gas molecules directly into the vacuum target chamber. Frozen gas targets comprised of simple molecules like methane and single element gasses like hydrogen and deuterium will provide novel target configuations that will be compared with laser plasma interaction simulations. The targets will be shot with the ultra-intense short-pulse Trident laser. Accelerated ion spectra will be characterized using a Thomson Parabola with magnetic field strength of 0.92T and electric field strength of 30kV. Hydrogen targets will be additionally characterized using stacks of copper which become activated upon exposure to energetic protons resulting in a beta decay signal which be imaged on electron sensitive imaging plates to provide an energy spectrum and spacial profile of the proton beam. Details of target creation and pre-shot characterization will be presented.

  17. Gold nanoparticles and films produced by a laser ablation/gas deposition (LAGD) method

    International Nuclear Information System (INIS)

    Kawakami, Yuji; Seto, Takafumi; Yoshida, Toshinobu; Ozawa, Eiichi

    2002-01-01

    Gold nanoparticles have great potential for various nanoelectronic applications such as single electron transistors, an infrared absorption sensor and so on. It is very important to understand and control the size distribution of the particles for such a variety of applications. In this paper, we report the size distribution of gold nanoparticles and the relationship between the nanoparticle-films and the electrical property produced by a laser ablation method. Gold nanoparticle-films were prepared by a technique, which sprays nanoparticles on the substrate through a nozzle. We call it a gas deposition method. The nanoparticles were generated by the nanosecond pulsed Nd:YAG laser ablation of a gold substrate under a low-pressure inert gas atmosphere. The ambient pressure was changed to control the average size and their distribution. The particles produced in the generation chamber were transported by a helium carrier gas to the deposition chamber and deposited on a substrate to form the films composed of gold nanoparticles. The electrical resistivity of the generated gold nanoparticle-films on the glass substrates was measured using a four-probe method. The size distribution of the nanoparticles was examined using transmission electron microscopy (TEM) and a low-pressure differential mobility analyzer (LP-DMA). The relationship between the particle size and the electrical properties of each film made by the different synthesis conditions were analyzed. The electrical resistivity changed from the order of 10 -5 to 10 -1 Ω cm depending on the ambient pressure and the size distribution

  18. The waveguide laser - A review

    Science.gov (United States)

    Degnan, J. J.

    1976-01-01

    The present article reviews the fundamental physical principles essential to an understanding of waveguide gas and liquid lasers, and the current technological state of these devices. At the present time, waveguide laser transitions span the visible through submillimeter regions of the wavelength spectrum. The introduction discusses the many applications of waveguide lasers and the wide variety of laser configurations that are possible. Section 1 summarizes the properties of modes in hollow dielectric waveguides of circular, rectangular, and planar cross section. Section 2 considers various approaches to optical feedback including internal and external mirror Fabry-Perot type resonators, hollow waveguide distributed feedback structures, and ring-resonant configurations. Section 3 discusses those aspects of molecular kinetic and laser theory pertinent to the design and optimization of waveguide gas lasers.

  19. III-nitride Photonic Integrated Circuit: Multi-section GaN Laser Diodes for Smart Lighting and Visible Light Communication

    KAUST Repository

    Shen, Chao

    2017-04-01

    The past decade witnessed the rapid development of III-nitride light-emitting diodes (LEDs) and laser diodes (LDs), for smart lighting, visible-light communication (VLC), optical storage, and internet-of-things. Recent studies suggested that the GaN-based LDs, which is free from efficiency droop, outperform LEDs as a viable high-power light source. Conventionally, the InGaN-based LDs are grown on polar, c-plane GaN substrates. However, a relatively low differential gain limited the device performance due to a significant polarization field in the active region. Therefore, the LDs grown on nonpolar m-plane and semipolar (2021)-plane GaN substrates are posed to deliver high-efficiency owing to the entirely or partially eliminated polarization field. To date, the smart lighting and VLC functionalities have been demonstrated based on discrete devices, such as LDs, transverse-transmission modulators, and waveguide photodetectors. The integration of III-nitride photonic components, including the light emitter, modulator, absorber, amplifier, and photodetector, towards the realization of III-nitride photonic integrated circuit (PIC) offers the advantages of small-footprint, high-speed, and low power consumption, which has yet to be investigated. This dissertation presents the design, fabrication, and characterization of the multi-section InGaN laser diodes with integrated functionalities on semipolar (2021)-plane GaN substrates for enabling such photonic integration. The blue-emitting integrated waveguide modulator-laser diode (IWM-LD) exhibits a high modulation efficiency of 2.68 dB/V. A large extinction ratio of 11.3 dB is measured in the violet-emitting IWM-LD. Utilizing an integrated absorber, a high optical power (250mW), droop-free, speckle-free, and large modulation bandwidth (560MHz) blue-emitting superluminescent diode is reported. An integrated short-wavelength semiconductor optical amplifier with the laser diode at ~404 nm is demonstrated with a large gain of 5

  20. Towards high-resolution laser ionization spectroscopy of the heaviest elements in supersonic gas jet expansion.

    Science.gov (United States)

    Ferrer, R; Barzakh, A; Bastin, B; Beerwerth, R; Block, M; Creemers, P; Grawe, H; de Groote, R; Delahaye, P; Fléchard, X; Franchoo, S; Fritzsche, S; Gaffney, L P; Ghys, L; Gins, W; Granados, C; Heinke, R; Hijazi, L; Huyse, M; Kron, T; Kudryavtsev, Yu; Laatiaoui, M; Lecesne, N; Loiselet, M; Lutton, F; Moore, I D; Martínez, Y; Mogilevskiy, E; Naubereit, P; Piot, J; Raeder, S; Rothe, S; Savajols, H; Sels, S; Sonnenschein, V; Thomas, J-C; Traykov, E; Van Beveren, C; Van den Bergh, P; Van Duppen, P; Wendt, K; Zadvornaya, A

    2017-02-22

    Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.

  1. Energy spread of ultracold electron bunches extracted from a laser cooled gas

    Science.gov (United States)

    Franssen, J. G. H.; Kromwijk, J. M.; Vredenbregt, E. J. D.; Luiten, O. J.

    2018-02-01

    Ultrashort and ultracold electron bunches created by near-threshold femtosecond photoionization of a laser cooled gas hold great promise for single-shot ultrafast diffraction experiments. In previous publications the transverse beam quality and the bunch length have been determined. Here the longitudinal energy spread of the generated bunches is measured for the first time, using a specially developed Wien filter. The Wien filter has been calibrated by determining the average deflection of the electron bunch as a function of magnetic field. The measured relative energy spread \\tfrac{{σ }U}{U}=0.64+/- 0.09 % agrees well with the theoretical model which states that it is governed by the width of the ionization laser and the acceleration length.

  2. New semiconductor laser technology for gas sensing applications in the 1650nm range

    Science.gov (United States)

    Morrison, Gordon B.; Sherman, Jes; Estrella, Steven; Moreira, Renan L.; Leisher, Paul O.; Mashanovitch, Milan L.; Stephen, Mark; Numata, Kenji; Wu, Stewart; Riris, Haris

    2017-08-01

    Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with approximately 25 times the radiative forcing of carbon dioxide (CO2) per molecule. CH4 also contributes to pollution in the lower atmosphere through chemical reactions leading to ozone production. Recent developments of LIDAR measurement technology for CH4 have been previously reported by Goddard Space Flight Center (GSFC). In this paper, we report on a novel, high-performance tunable semiconductor laser technology developed by Freedom Photonics for the 1650nm wavelength range operation, and for LIDAR detection of CH4. Devices described are monolithic, with simple control, and compatible with low-cost fabrication techniques. We present 3 different types of tunable lasers implemented for this application.

  3. Complexation of europium(III) with the zwitterionic form of amino acids studied with ultraviolet-visible and time-resolved laser-induced fluorescence spectroscopy.

    Science.gov (United States)

    Heller, Anne; Rönitz, Olivia; Barkleit, Astrid; Bernhard, Gert; Ackermann, Jörg-Uwe

    2010-08-01

    The complex formation of europium(III) with the zwitterionic form of amino acids (alanine, phenylalanine, and threonine) has been studied in aqueous solution. Measurements were performed at I = 0.1 M (NaCl/NaClO(4)), room temperature, and trace metal concentrations in the range of pH 2 to 8 using ultraviolet-visible (UV-Vis) and time-resolved laser-induced fluorescence spectroscopy (TRLFS). While complexation leads to a significant luminescence enhancement in the emission spectrum of the metal ion, absorption in the UV-Vis spectrum of the amino acid (AA) decreases. As zwitterionic species (AAH), all three ligands form weak complexes with 1:1 stoichiometry and a general formula of EuAAH(3+) with the metal. The complex stability constants were determined to be log K approximately 1 for all complexes, indicating the negligible contribution of the amino acid side chain to the complex formation reaction.

  4. 4-Gbit/s visible light communication link based on 16-QAM OFDM transmission over remote phosphor-film converted white light by using blue laser diode

    KAUST Repository

    Duran Retamal, Jose Ramon

    2015-12-21

    Visible Light Communication (VLC) as a new technology for ultrahigh-speed communication is still limited when using slow modulation light-emitting diode (LED). Alternatively, we present a 4-Gbit/s VLC system using coherent blue-laser diode (LD) via 16-quadrature amplitude modulation orthogonal frequency division multiplexing. By changing the composition and the optical-configuration of a remote phosphor-film the generated white light is tuned from cool day to neutral, and the bit error rate is optimized from 1.9 × 10-2 to 2.8 × 10-5 in a blue filter-free link due to enhanced blue light transmission in forward direction. Briefly, blue-LD is an alternative to LED for generating white light and boosting the data rate of VLC. © 2015 Optical Society of America.

  5. Applications of a Mid-IR Quantum Cascade Laser in Gas Sensing Research

    KAUST Repository

    Sajid, Muhammad Bilal

    2015-05-01

    Laser absorption based sensors are extensively used in a variety of gas sensing areas such as combustion, atmospheric research, human breath analysis, and high resolution infrared spectroscopy. Quantum cascade lasers have recently emerged as high resolution, high power laser sources operating in mid infrared region and can have wide tunability range. These devices provide an opportunity to access stronger fundamental and combination vibrational bands located in mid infrared region than previously accessible weaker overtone vibrational bands located in near infrared region. Spectroscopic region near 8 µm contains strong vibrational bands of methane, acetylene, hydrogen peroxide, water vapor and nitrous oxide. These molecules have important applications in a wide range of applications. This thesis presents studies pertaining to spectroscopy and combustion applications. Advancements in combustion research are imperative to achieve lower emissions and higher efficiency in practical combustion devices such as gas turbines and engines. Accurate chemical kinetic models are critical to achieve predictive models which contain several thousand reactions and hundreds of species. These models need highly reliable experimental data for validation and improvements. Shock tubes are ideal devices to obtain such information. A shock tube is a homogenous, nearly constant volume, constant pressure, adiabatic and 0-D reactor. In combination with laser absorption sensors, shock tubes can be used to measure reaction rates and species time histories of several intermediates and products formed during pyrolysis and oxidation of fuels. This work describes measurement of the decomposition rate of hydrogen peroxide which is an important intermediate species controlling reactivity of combustion system in the intermediate temperature range. Spectroscopic parameters (linestrengths, broadening coefficients and temperature dependent coefficients) are determined for various transitions of

  6. Visible ns-pulse laser oscillation in Pr-doped double-clad structured waterproof fluoride glass fibre with SESAM

    Directory of Open Access Journals (Sweden)

    Shota Kajikawa

    2017-06-01

    Full Text Available A visible Q-switched pulse train at 639 nm was successfully generated in a Pr-doped double-clad structured waterproof fluoride glass fibre with a semiconductor saturable absorber mirror. The slope efficiency was calculated as 36.3%. The pulse duration and the radio frequency were measured as 270 ns and 107 kHz at 596 mW of absorbed power, respectively. The pulse energy and the pulse peak power were calculated as 1.32 μJ and 4.87 W, respectively.

  7. [Use of gas laser LG-55 to determine the optical density of biological objects].

    Science.gov (United States)

    Zakruta, M P; Zlupko, V N

    1978-12-01

    In order to registrate optic density of such subjects as vessels, tissues, roentgenogram and electrophoregram images, a universal device is suggested. It consists of a) a gas laser lg-55 supplying a parallel bundle of light with small angular deflection and wave length of 0,6328 mc; b) mounting for attachment the reversive motor pd-9 with transmission to change the speed of the subject table, photo resistance fCK-1, focussing lens triple-edged prism and diaphragm, c) double coordinative recorder (endim 620.01). Repeatedly performed registration of the same arterioroentgenogram (or any other investigated) has demonstrated a high accuracy of the registered curves.

  8. Monitoring and Control of the Hybrid Laser-Gas Metal-Arc Welding Process

    Energy Technology Data Exchange (ETDEWEB)

    Kunerth, D. C.; McJunkin, T. R.; Nichol, C. I.; Clark, D.; Todorov, E.; Couch, R. D.; Yu, F.

    2013-07-01

    Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defects or precursors to defects and correct when possible during the weld process.

  9. Efficient Boron Nitride Nanotube Formation via Combined Laser-Gas Flow Levitation

    Science.gov (United States)

    Whitney, R. Roy (Inventor); Jordan, Kevin (Inventor); Smith, Michael W. (Inventor)

    2014-01-01

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B(sub x)C(sub y)N(sub z) The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B(sub x)C(sub y)N(sub z).

  10. Efficient Boron-Carbon-Nitrogen Nanotube Formation Via Combined Laser-Gas Flow Levitation

    Science.gov (United States)

    Whitney, R. Roy (Inventor); Jordan, Kevin (Inventor); Smith, Michael W. (Inventor)

    2015-01-01

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula BxCyNz. The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula BxCyNz.

  11. Microsecond fiber laser pumped, single-frequency optical parametric oscillator for trace gas detection.

    Science.gov (United States)

    Barria, Jessica Barrientos; Roux, Sophie; Dherbecourt, Jean-Baptiste; Raybaut, Myriam; Melkonian, Jean-Michel; Godard, Antoine; Lefebvre, Michel

    2013-07-01

    We report on the first microsecond doubly resonant optical parametric oscillator (OPO). It is based on a nested cavity OPO architecture allowing single longitudinal mode operation and low oscillation threshold (few microjoule). The combination with a master oscillator-power amplifier fiber pump laser provides a versatile optical source widely tunable in the 3.3-3.5 μm range with an adjustable pulse repetition rate (from 40 to 100 kHz), high duty cycle (~10(-2)) and mean power (up to 25 mW in the idler beam). The potential for trace gas sensing applications is demonstrated through photoacoustic detection of atmospheric methane.

  12. Highly transparent conductive AZO/Zr50Cu50/AZO films in wide range of visible and near infrared wavelength grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Jingyun Cheng

    Full Text Available Novel AZO/Zr50Cu50/AZO tri-layer transparent conductive films with excellent transmittance in both visible and near infrared region were successfully prepared by pulsed laser deposition on glass substrates. The electrical and optical properties were investigated at various Zr50Cu50 thicknesses. As the AZO thickness was fixed at 50 nm and Zr50Cu50 thickness was varied between 1 and 18 nm, it was found that AZO (50 nm/Zr50Cu50/AZO (50 nm tri-layer films exhibited good conductivity and high transmittance in both visible and near infrared wavelength. Additionally, both the electrical and optical properties of AZO (50 nm/Zr50Cu50 (2 nm/AZO (50 nm tri-layer films were found to be sensitive to the growth temperature. In this work, the lowest sheet resistance (43 Ω/□ and relatively high transmittance (∼80% in the range of 400–2000 nm were achieved while the growth temperature was 350 °C. Furthermore, the AZO (50 nm/Zr50Cu50 (2 nm/AZO (50 nm thin film deposited at 350 °C exhibits the highest figure of merit of 1.42 × 10−3 Ω−1, indicating that the multilayer is promising for coated glasses and thin film solar cells. Keywords: Transparent conductive oxide, AZO, Zr50Cu50, Electrical and optical properties, Visible and near infrared transmittance

  13. Effect of Laser Power and Gas Flow Rate on Properties of Directed Energy Deposition of Titanium Alloy

    Science.gov (United States)

    Mahamood, Rasheedat M.

    2018-01-01

    Laser metal deposition (LMD) process belongs to the directed energy deposition class of additive manufacturing processes. It is an important manufacturing technology with lots of potentials especially for the automobile and aerospace industries. The laser metal deposition process is fairly new, and the process is very sensitive to the processing parameters. There is a high level of interactions among these process parameters. The surface finish of part produced using the laser metal deposition process is dependent on the processing parameters. Also, the economy of the LMD process depends largely on steps taken to eliminate or reduce the need for secondary finishing operations. In this study, the influence of laser power and gas flow rate on the microstructure, microhardness and surface finish produced during the laser metal deposition of Ti6Al4V was investigated. The laser power was varied between 1.8 kW and 3.0 kW, while the gas flow rate was varied between 2 l/min and 4 l/min. The microstructure was studied under an optical microscope, the microhardness was studied using a Metkon microhardness indenter, while the surface roughness was studied using a Jenoptik stylus surface analyzer. The results showed that better surface finish was produced at a laser power of 3.0 kW and a gas flow rate of 4 l/min.

  14. Optical design of multi-multiple expander structure of laser gas analysis and measurement device

    Science.gov (United States)

    Fu, Xiang; Wei, Biao

    2018-03-01

    The installation and debugging of optical circuit structure in the application of carbon monoxide distributed laser gas analysis and measurement, there are difficult key technical problems. Based on the three-component expansion theory, multi-multiple expander structure with expansion ratio of 4, 5, 6 and 7 is adopted in the absorption chamber to enhance the adaptability of the installation environment of the gas analysis and measurement device. According to the basic theory of aberration, the optimal design of multi-multiple beam expander structure is carried out. By using image quality evaluation method, the difference of image quality under different magnifications is analyzed. The results show that the optical quality of the optical system with the expanded beam structure is the best when the expansion ratio is 5-7.

  15. Resonant third harmonic generation of KrF laser in Ar gas.

    Science.gov (United States)

    Rakowski, R; Barna, A; Suta, T; Bohus, J; Földes, I B; Szatmári, S; Mikołajczyk, J; Bartnik, A; Fiedorowicz, H; Verona, C; Verona Rinati, G; Margarone, D; Nowak, T; Rosiński, M; Ryć, L

    2014-12-01

    Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

  16. High pressure laser plasma studies. [energy pathways in He-Ar gas mixtures at low pressure

    Science.gov (United States)

    Wells, W. E.

    1980-01-01

    The operation of a nuclear pumped laser, operating at a wavelength of 1.79 micron m on the 3d(1/2-4p(3/2) transition in argon with helium-3 as the majority gas is discussed. The energy pathways in He-Ar gas were investigated by observing the effects of varying partial pressures on the emissions of levels lying above the 4p level in argon during a pulsed afterglow. An attempt is made to determine the population mechanisms of the 3d level in pure argon by observing emission from the same transition in a high pressure plasma excited by a high energy electron beam. Both collisional radiative and dissociative recombination are discussed.

  17. Influence of shielding gas pressure on welding characteristics in CO2 laser-MIG hybrid welding process

    Science.gov (United States)

    Chen, Yanbin; Lei, Zhenglong; Li, Liqun; Wu, Lin

    2006-01-01

    The droplet transfer behavior and weld characteristics have been investigated under different pressures of shielding gas in CO2 laser and metal inert/active gas (laser-MIG) hybrid welding process. The experimental results indicate that the inherent droplet transfer frequency and stable welding range of conventional MIG arc are changed due to the interaction between CO2 laser beam and MIG arc in laser-MIG hybrid welding process, and the shielding gas pressure has a crucial effect on welding characteristics. When the pressure of shielding gas is low in comparison with MIG welding, the frequency of droplet transfer decreases, and the droplet transfer becomes unstable in laser-MIG hybrid welding. So the penetration depth decreases, which shows the characteristic of unstable hybrid welding. However, when the pressure of shielding gas increases to a critical value, the hybrid welding characteristic is changed from unstable hybrid welding to stable hybrid welding, and the frequency of droplet transfer and the penetration depth increase significantly.

  18. Incidence and Outcomes of Anterior Chamber Gas Bubble during Femtosecond Flap Creation for Laser-Assisted In Situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Sloan W. Rush

    2015-01-01

    Full Text Available Purpose. To report the incidence and outcomes of anterior chamber gas bubble formation during femtosecond laser flap creation for laser-assisted in situ keratomileusis (LASIK. Methods. The charts of 2,886 consecutive eyes that underwent femtosecond LASIK from May 2011 through August 2014 were retrospectively reviewed. The incidence, preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed in subjects developing anterior chamber gas bubble formation during the procedure. Results. A total of 4 cases (0.14% developed anterior chamber gas bubble formation during femtosecond laser flap creation. In all four cases, the excimer laser was unable to successfully track the pupil immediately following the anterior chamber bubble formation, temporarily postponing the completion of the procedure. There was an ethnicity predilection of anterior chamber gas formation toward Asians (p=0.0055. An uncorrected visual acuity of 20/20 was ultimately achieved in all four cases without further complications. Conclusions. Anterior chamber gas bubble formation during femtosecond laser flap creation for LASIK is an uncommon event that typically results in a delay in treatment completion; nevertheless, it does influence final positive visual outcome.

  19. Materials processing issues for non-destructive laser gas sampling (NDLGS)

    Energy Technology Data Exchange (ETDEWEB)

    Lienert, Thomas J [Los Alamos National Laboratory

    2010-12-09

    The Non-Destructive Laser Gas Sampling (NDLGS) process essentially involves three steps: (1) laser drilling through the top of a crimped tube made of 304L stainles steel (Hammar and Svennson Cr{sub eq}/Ni{sub eq} = 1.55, produced in 1985); (2) gas sampling; and (3) laser re-welding of the crimp. All three steps are performed in a sealed chamber with a fused silica window under controlled vacuum conditions. Quality requirements for successful processing call for a hermetic re-weld with no cracks or other defects in the fusion zone or HAZ. It has been well established that austenitic stainless steels ({gamma}-SS), such as 304L, can suffer from solidification cracking if their Cr{sub eq}/Ni{sub eq} is below a critical value that causes solidification to occur as austenite (fcc structure) and their combined impurity level (%P+%S) is above {approx}0.02%. Conversely, for Cr{sub eq}/Ni{sub eq} values above the critical level, solidification occurs as ferrite (bcc structure), and cracking propensity is greatly reduced at all combined impurity levels. The consensus of results from studies of several researchers starting in the late 1970's indicates that the critical Cr{sub eq}/Ni{sub eq} value is {approx}1.5 for arc welds. However, more recent studies by the author and others show that the critical Cr{sub eq}/Ni{sub eq} value increases to {approx}1 .6 for weld processes with very rapid thermal cycles, such as the pulsed Nd:YAG laser beam welding (LBW) process used here. Initial attempts at NDLGS using pulsed LBW resulted in considerable solidification cracking, consistent with the results of work discussed above. After a brief introduction to the welding metallurgy of {gamma}-SS, this presentation will review the results of a study aimed at developing a production-ready process that eliminates cracking. The solution to the cracking issue, developed at LANL, involved locally augmenting the Cr content by applying either Cr or a Cr-rich stainless steel (ER 312) to the top

  20. High-quality laser cutting of stainless steel in inert gas atmosphere by ytterbium fibre and CO2 lasers

    International Nuclear Information System (INIS)

    Golyshev, A A; Malikov, A G; Orishich, A M; Shulyat'ev, V B

    2014-01-01

    Processes of cutting stainless steel by ytterbium fibre and CO 2 lasers have been experimentally compared. The cut surface roughnesses for 3- and 5-mm-thick stainless steel sheets are determined. The absorption coefficient of laser radiation during cutting is measured. It is established that the power absorbed by metal during cutting by the CO 2 laser exceeds that for the ytterbium laser (provided that the cutting speed remains the same). The fact that the maximum cutting speed of the CO 2 laser is lower than that of the ytterbium fibre laser is explained. (laser technologies)

  1. Emitting far-field multicolor patterns and characters through plastic diffractive micro-optics elements illuminated by common Gaussian lasers in the visible range.

    Science.gov (United States)

    Zhang, Xinyu; Li, Hui; Liu, Kan; Luo, Jun; Xie, Changsheng; Ji, An; Zhang, Tianxu

    2011-04-01

    Far-field multicolor patterns and characters are emitted effectively in a relatively wide and deep spatial region by plastic diffractive micro-optics elements (DMOEs), which are illuminated directly by common Gaussian lasers in the visible range. Phase-only DMOEs are composed of a large number of fine step-shaped phase microstructures distributed sequentially over the plastic wafer selected. The initial DMOEs in silicon wafer are fabricated by an innovative technique with a combination of a single-mask ultraviolet photolithography and low-cost and rapid wet KOH etching. The fabricated silicon DMOEs are further converted into a nickel mask by the conventional electrochemical method, and they are finally transferred onto the surface of the plastic wafer through mature hot embossing. Morphological measurements show that the surface roughness of the plastic DMOEs is in the nanometer range, and the feature height of the phase steps in diffractive elements is in the submicrometer scale, which can be designed and adjusted flexibly according to requirements. The dimensions of the DMOEs can be changed from the order of millimeters to centimeters. A large number of pixel phase microstructures with a square microappearance employed to construct the phase-only DMOEs are created by the Gerchberg-Saxton algorithm, according to the target patterns and characters and common Gaussian lasers manipulated by the DMOEs fabricated. © 2011 Optical Society of America

  2. Control of electron beam by using high-Z gas target in the laser-plasma acceleration

    International Nuclear Information System (INIS)

    Mori, Michiaki

    2012-01-01

    We investigate the pointing stability and the divergence of a quasi-monoenergetic electron beam generated in a self-injected laser-plasma acceleration regime using high-Z gas-jet target. Gas-jet targets have been irradiated with focused 40 fs laser pulses at the 4-TW peak power. A pointing stability and a beam divergence of electron beam were improved using argon target. These values were about three times smaller than at the optimum condition using helium. This stabilization method is available for another gas material such as nitrogen. At nitrogen gas-jet target, the pointing stability is more improved to two times smaller than that in argon gas-jet target and the peak energy is increased to >30 MeV. These results prove that this method not only stabilizes the e-beam but also allows controlling the electron energy. (author)

  3. High sensitivity ethanol gas sensor based on Sn - doped ZnO under visible light irradiation at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Peishuo; Pan, Guofeng; Zhang, Bingqiang; Zhen, Jiali; Sun, Yicai, E-mail: pgf@hebut.edu.cn [Institute of Microelectronic, Hebei University of Technology, Tianjin (China)

    2014-07-15

    Pure ZnO and 5at%, 7at%, 9at% Sn - doped ZnO materials are prepared by the chemical co - precipitation method. They were annealed by furnace at temperature range of 300 - 700ºC in air for 1h. The ZnO materials are characterized by X - ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the Sn - doped ZnO materials appear rough porous structures. The maximum sensitivity can be achieved by doping the amount of 7 at%. It has much better sensing performance towards ethanol vapor under visible light irradiation. The response and recovery time are ~1s and ~5s, respectively. The mechanism for the improvement in the sensing properties can be explained with the surface adsorption theory and the photoactivation theory. (author)

  4. Radiation power control of the industrial CO2 lasers excited by a nonself-sustained glow discharge with regard to dissociation in a working gas mixture

    Science.gov (United States)

    Shemyakin, Andrey N.; Rachkov, Michael Yu.; Solovyov, Nikolay G.; Yakimov, Mikhail Yu.

    2018-01-01

    The action of a working gas mixture degradation related to the plasma chemical reactions in a glow discharge on the laser output power of the molecular laser excited by a nonself-sustained glow discharge has been studied by the example of an industrial laser of ;Lantan; CO2 laser series. It was found that the laser power overshoot when operating on a fresh gas mixture may exceed 3 times power level set in a steady-state regime. The working algorithm for the control system was proposed and developed setting standard fresh CO2/N2/He laser gas mixture to plasma chemical equilibrium composition during the laser turn-on procedure after full refill of a working gas mixture.

  5. New GasB-based single-mode diode lasers in the NIR and MIR spectral regime for sensor applications

    Science.gov (United States)

    Milde, Tobias; Hoppe, Morten; Tatenguem, Herve; Honsberg, Martin; Mordmüller, Mario; O'Gorman, James; Schade, Wolfgang; Sacher, Joachim

    2018-02-01

    The NIR/MIR region between 1.8μm and 3.5μm contains important absorption lines for gas detection. State of the art are InP laser based setups, which show poor gain above 1.8μm and cannot be applied beyond 2.1μm. GaSb laser show a significantly higher output power (100mW for Fabry-Perot, 30mW for DFB). The laser design is presented with simulation and actual performance data. The superior performance of the GaSb lasers is verified in gas sensing applications. TDLAS and QEPAS measurements at trace gases like CH4, CO2 and N2O are shown to prove the spectroscopy performance.

  6. Heat-transfer regimes in nuclear-reactor-pumped gas lasers

    Energy Technology Data Exchange (ETDEWEB)

    Torczynski, J.R.

    1990-01-01

    The flow induced in nuclear-reactor-pumped gas lasers by the competing effects of spatially nonuniform fission-fragment heating (pumping) and heat transfer to the walls is examined. The equations of motion are acoustically filtered (low Mach number approximation), and the resulting equations are seen to have three timescales: the duration of the heating, the time required by the heating to produce a pressure rise comparable to the initial pressure, and the time for the thermal boundary layer to grow into the center of the laser cell. Three distinct regimes emerge from consideration of the relative magnitudes of these timescales. In the negligible-conduction regime, thermal-conduction effects are small, and the motion is determined by the spatial nonuniformity of the heating. In the dominant-conduction regime, thermal-conduction effects govern the motion. In the mixed regime, the effects of thermal conduction and heating nonuniformity are comparable, but since they are oppositely directed, a complex gas motion results. Analytical solutions to the equations of motion are presented for the negligible-conduction and dominant-conduction regimes, and examples are given for all three regimes. Plots of the second spatial derivative of the density field (a quantity often used in optical analyses) are given for the negligible-conduction and the dominant-conduction regimes as functions of the appropriate similarity parameters. 26 refs., 14 figs.

  7. Ion Acceleration from Pure Frozen Gas Targets using Short Pulse Lasers

    Science.gov (United States)

    McCary, Edward; Stehr, Florian; O'Shea, Finn; Jiao, Xuejing; Agustsson, Ronald; Berry, Robert; Chao, Dennis; Gautier, Donald; Letzring, Samuel; Quevedo, Hernan; Woods, Kaley; Hegelich, Bjorn

    2014-10-01

    A system for shooting interchangeable frozen gas ice targets was developed and tested on the Trident laser system at Los Alamos National Lab. A target holder which could hold up to five substrates used for target growing was cryogenically cooled to temperatures below 14 K. The target substrates consisted of holes with diameters ranging from 15 μm-500 μm and TEM grids with micron scale spacing, across which films of ice were frozen by releasing small amounts of pure gas molecules directly into the vacuum target chamber. The thickness of the ice targets was determined by using alpha spectroscopy. Accelerated ion spectra were characterized using a Thomson Parabola with magnetic field strength of 0.92 T and electric field strength of 30kV and radio-chromic film stacks. Hydrogen targets were additionally characterized using stacks of copper which became activated upon exposure to energetic protons resulting in a beta decay signal. The beta decay was imaged on electron sensitive imaging plates to provide an energy spectrum and spacial profile of the proton beam. Results of the interchangeable, laser-based ion accelerator will be presented. Work Supported by NIH grant.

  8. Models of WO x films growth during pulsed laser deposition at elevated pressures of reactive gas

    Science.gov (United States)

    Gnedovets, A. G.; Fominski, V. Y.; Nevolin, V. N.; Romanov, R. I.; Fominski, D. V.; Soloviev, A. A.

    2017-12-01

    The films of tungsten oxides were prepared by pulsed laser ablation of W target in a reactive gas atmosphere (air of laboratory humidity). Optical analysis and ion signal measurements for the laser plume allowed to recognise a threshold gas pressure that suppresses the deposition of non-scattered atomic flux from the plume. When the pressure exceeds about 40 Pa, the films grow due to the deposition of species that could be formed in collisions of W atoms with reactive molecules (e.g., O2). Kinetic Monte Carlo method was used for modelling film growth. Comparison of the model structures with the experimentally prepared films has shown that the growth mechanism of ballistic deposition at a pressure of 40 Pa could be changed on the diffusion limited aggregation at a pressure of ~100 Pa. Thus, a cauliflower structure of the film transformed to a web-like structure. For good correlation of experimental and model structures of WO x , a dimension of structural elements in the model should coincide with W-O cluster size.

  9. Non-invasive gas monitoring in newborn infants using diode laser absorption spectroscopy: a case study

    Science.gov (United States)

    Lundin, Patrik; Svanberg, Emilie K.; Cocola, Lorenzo; Lewander, Märta; Andersson-Engels, Stefan; Jahr, John; Fellman, Vineta; Svanberg, Katarina; Svanberg, Sune

    2012-03-01

    Non-invasive diode laser spectroscopy was, for the first time, used to assess gas content in the intestines and the lungs of a new-born, 4 kg, baby. Two gases, water vapor and oxygen, were studied with two low-power tunable diode lasers, illuminating the surface skin tissue and detecting the diffusely emerging light a few centimeters away. The light, having penetrated into the tissue, had experienced absorption by gas located in the lungs and in the intestines. Very distinct water vapor signals were obtained from the intestines while imprint from oxygen was lacking, as expected. Detectable, but minor, signals of water vapor were also obtained from the lungs, illuminating the armpit area and detecting below the collar bone. Water vapor signals were seen but again oxygen signals were lacking, now due to the difficulties of penetration of the oxygen probing light into the lungs of this full-term baby. Ultra-sound images were obtained both from the lungs and from the stomach of the baby. Based on dimensions and our experimental findings, we conclude, that for early pre-term babies, also oxygen should be detectable in the lungs, in addition to intestine and lung detection of water vapor. The present paper focuses on the studies of the intestines while the lung studies will be covered in a forthcoming paper.

  10. Optical Properties Dependence with Gas Pressure in AlN Films Deposited by Pulsed Laser Ablation

    International Nuclear Information System (INIS)

    Perez, J A; Riascos, H; Caicedo, J C; Cabrera, G; Yate, L

    2011-01-01

    AlN films were deposited by pulsed laser deposition technique (PLD) using an Nd: YAG laser (λ = 1064 nm). The films were deposited in a nitrogen atmosphere as working gas; the target was an aluminum high purity (99.99%). The films were deposited with a laser fluence of 7 J/cm2 for 10 minutes on silicon (100) substrates. The substrate temperature was 300 deg. C and the working pressure was varied from 3 mtorr to 11 mtorr. The thickness measured by profilometer was 150 nm for all films. The crystallinity was observed via XRD pattern, the morphology and composition of the films were studied using scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400 cm-1- 900 cm-1 by an Ocean Optics 2000 spectrophotometer. In this work, a clear dependence of the reflectance, dominant wavelength and color purity was found in terms of the applied pressure to the AlN films. A reduction in reflectance of about 55% when the pressure was increased from 3 mtorr to 11 mtorr was observed. This paper deals with the formation of AlN thin films as promising materials for the integration of SAW devices on Si substrates due to their good piezoelectric properties and the possibility of deposition at low temperature compatible with the manufacturing of Si integrated circuits.

  11. Optical Properties Dependence with Gas Pressure in AlN Films Deposited by Pulsed Laser Ablation

    Energy Technology Data Exchange (ETDEWEB)

    Perez, J A; Riascos, H [Departamento de Fisica, Universidad Tecnologica de Pereira, Grupo plasma Laser y Aplicaciones A.A 097 (Colombia); Caicedo, J C [Grupo pelIculas delgadas, Universidad del Valle, Cali (Colombia); Cabrera, G; Yate, L, E-mail: jcaicedoangulo@gmail.com [Department de Fisica Aplicada i Optica, Universitat de Barcelona, Catalunya (Spain)

    2011-01-01

    AlN films were deposited by pulsed laser deposition technique (PLD) using an Nd: YAG laser ({lambda} = 1064 nm). The films were deposited in a nitrogen atmosphere as working gas; the target was an aluminum high purity (99.99%). The films were deposited with a laser fluence of 7 J/cm2 for 10 minutes on silicon (100) substrates. The substrate temperature was 300 deg. C and the working pressure was varied from 3 mtorr to 11 mtorr. The thickness measured by profilometer was 150 nm for all films. The crystallinity was observed via XRD pattern, the morphology and composition of the films were studied using scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400 cm-1- 900 cm-1 by an Ocean Optics 2000 spectrophotometer. In this work, a clear dependence of the reflectance, dominant wavelength and color purity was found in terms of the applied pressure to the AlN films. A reduction in reflectance of about 55% when the pressure was increased from 3 mtorr to 11 mtorr was observed. This paper deals with the formation of AlN thin films as promising materials for the integration of SAW devices on Si substrates due to their good piezoelectric properties and the possibility of deposition at low temperature compatible with the manufacturing of Si integrated circuits.

  12. Numerical analysis of excimer laser-induced breakdown of Kr gas

    Science.gov (United States)

    Hamam, Kholoud A.; Elsayed, Khaled A.; Gamal, Yosr E. E.

    2017-03-01

    The present paper displays a numerical study on the role of electron dynamics in relation to the dependence of the threshold intensity on the pressure in the breakdown of gases by laser radiation. The analysis aimed to find out the origin of the steep slope observed in the measurements of threshold intensity against gas pressure in the breakdown of Kr induced by an excimer laser source (Opt. Commun. 13:66-68, 1). The experiment was carried out using wavelength 248 nm and pulse width of 18 ns for a gas pressure range 4.5-300 torr. The investigation centered on an adaptation of our previously developed electron cascade model given in Evans and Gamal (J. Phys. D Appl. Phys. 13:1447-1458, 2). This model solves numerically a time-dependent energy equation simultaneously with a set of rate equations that describe the change of the population of the formed excited states. The modifications introduced into the model the realistic structure of the krypton gas atom as well as electron diffusion as a loss process to inspect the experimentally tested low-pressure regime. A computer program is undertaken to determine the breakdown threshold intensity as a function of gas pressure. Reasonable agreement is obtained between the calculated thresholds and measured ones, corresponding to the examined pressure range. This agreement validates the applicability of the model. The relationship between the role of the physical mechanisms and gas pressure is studied by analyzing the EEDF and its parameters at selected pressure values that cover the experimentally tested range. The result of this study clarified that electron diffusion out of the focal region is responsible for the steep slope of the threshold intensities for pressures <75 torr. For higher pressures (75-300 torr), collisional excitation of ground-state atoms followed by their ionization via multiphoton and collisional processes acts to convert the Kr gas in the interaction region into the state of breakdown. Investigation of

  13. Anterior chamber gas bubbles during femtosecond laser flap creation in LASIK: video evidence of entry via trabecular meshwork.

    Science.gov (United States)

    Soong, H Kaz; de Melo Franco, Rafael

    2012-12-01

    Femtosecond laser photodisruption of corneal stroma during laser in situ keratomileusis flap creation is accompanied by the formation of cavitation gas bubbles consisting of carbon dioxide and water vapor. Entry of these bubbles into the anterior chamber is an infrequent complication. We present video evidence that these bubbles enter via the trabecular meshwork. Neither author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  14. New continuous wave infrared Ar-Xe laser at intermediate gas pressures pumped by a transverse RF discharge

    NARCIS (Netherlands)

    Udalov, Yu.B.; Peters, P.J.M.; Ilieva, M.B.; Heeman-Ilieva, M.B.; Ernst, F.H.J.; Ochkin, V.N.; Witteman, W.J.

    1993-01-01

    An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 μm. The unoptimized total output power of 330 mW was obtained for a gas

  15. Influence of Gas Sort on the Nucleation Region Width of Si Nanocrystal Grains Prepared by Pulsed Laser Ablation

    Directory of Open Access Journals (Sweden)

    Zechao Deng

    2014-01-01

    Full Text Available We have calculated the nucleation region (NR location of Si nanocrystal grains prepared by pulsed laser ablation (PLA with fluence of 4 J/cm2 in 10 Pa gas at room temperature, and ambient gases were He, Ne, and Ar, respectively. Results of calculation indicated that NR width in Ne gas was narrowest, while it was widest in He gas. Maximum mean size of grains deposited on substrates under ablated spot, which were placed horizontally, was the smallest in Ne gas. It would be attribute to more effective energy transfer during the process of collision when atomic mass of Si and ambient gas Ne are more close to each other. In this work, an additional gas flow with the same element as ambient gas was introduced, which is vertical to the plume axis at different lateral positions above ablated spot.

  16. Design of Composite Photocatalyst of TiO2 and Y-Zeolite for Degradation of 2-Propanol in the Gas Phase under UV and Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Takashi Kamegawa

    2014-10-01

    Full Text Available Hydrophobic Y-zeolite (SiO2/Al2O3 = 810 and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (λ > 420 nm irradiation.

  17. Visible-light active thin-film WO3 photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    Directory of Open Access Journals (Sweden)

    Nobuto Oka

    2015-10-01

    Full Text Available A process based on reactive gas flow sputtering (GFS for depositing visible-light active photocatalytic WO3 films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO3 films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH3CHO under visible light irradiation. The decomposition time for 60 ppm of CH3CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO3 films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH3CHO.

  18. Design of composite photocatalyst of TiO2 and Y-zeolite for degradation of 2-propanol in the gas phase under UV and visible light irradiation.

    Science.gov (United States)

    Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

    2014-10-13

    Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (λ > 420 nm) irradiation.

  19. Visible light scattering properties of irregularly shaped silica microparticles using laser based laboratory simulations for remote sensing and medical applications

    Science.gov (United States)

    Boruah, Manash J.; Ahmed, Gazi A.

    2018-01-01

    Laser based experimental light scattering studies of irregularly shaped silica microparticles have been performed at three incident wavelengths 543.5 nm, 594.5 nm and 632.8 nm supported by laboratory based computations and 3D realistic simulations, using an indigenously fabricated light scattering setup. A comparative analysis of the computational and experimentally acquired results is done and a good agreement is found in the forward scattering lobes in all cases for each of the measured scattering parameters. This study also provides an efficient way of detecting and measuring particle size distribution for irregular micro- and nanoparticles and is highly applicable in remote sensing, atmospheric, astrophysical, and medical applications and also for finding potential health hazards in the form of inhalable and respirable small particulate matter.

  20. Bremsstrahlung γ-ray generation by electrons from gas jets irradiated by laser pulses for radiographic testing

    International Nuclear Information System (INIS)

    Oishi, Yuji; Nayuki, Takuya; Zhidkov, Alexei; Fujii, Takashi; Nemoto, Koshichi

    2012-01-01

    Electron generation from a gas jet irradiated by low energy femtosecond laser pulses is studied experimentally as a promising source of radiation for radioisotope-free γ-ray imaging systems. The calculated yield of γ-rays in the 0.5-2 MeV range, produced by low-average-power lasers and gas targets, exceeds the yields from solid tape targets up to 60 times. In addition, an effect of quasi-mono energetic electrons on γ-ray imaging is also discussed.

  1. FIBER LASER CONSTRUCTION AND THEORY INCLUDING FIBER BRAGG GRATINGS Photonic Crystal Fibers (PCFs) and applications of gas filled PCFs

    Energy Technology Data Exchange (ETDEWEB)

    Sutton, Jacob O. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-08

    The principles used in fiber lasers have been around for a while but it is only within the past few years that fiber lasers have become commercially available and used in high power laser applications. This paper will focus on the basic design principles of fiber lasers, including fiber Bragg gratings, principles of operation, and forms of non-linear effects. It will describe the type and associated doping of the fiber used and difficult designs used to guide energy from the pump to the active medium. Topics covered include fiber laser design, fiber Bragg gratings, materials used, differences in quantum energy loss, thermo-optical effects, stimulated Raman scattering, Brillouin scattering, photonic crystal fibers and applications of gas filled Photonic Crystal Fibers (PCFs). Thanks to fiber lasers, the energy required to produce high power lasers has greatly dropped and as such we can now produce kW power using a standard 120V 15A circuit. High power laser applications are always requiring more power. The fiber laser can now deliver the greater power that these applications demand. Future applications requiring more power than can be combined using standard materials or configurations will need to be developed to overcome the high energy density and high non-linear optical scattering effects present during high power operations.

  2. Wide-field laser ophthalmoscopy for imaging of gas-filled eyes after macular hole surgery

    Directory of Open Access Journals (Sweden)

    Nakao S

    2016-08-01

    Full Text Available Shintaro Nakao,1 Ryoichi Arita,1 Yuki Sato,2 Hiroshi Enaida,3 Akifumi Ueno,2 Takaaki Matsui,2 Hani Salehi-Had,4 Tatsuro Ishibashi,1 Koh-hei Sonoda1 1Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, 2Ohshima Hospital of Ophthalmology, Fukuoka, 3Department of Ophthalmology, Faculty of Medicine, Saga University, Saga, Japan; 4Atlantis Eyecare, Huntington Beach, CA, USA Background and objective: Existing ophthalmoscopy methods are unable to obtain clear fundus autofluorescence (FAF images in gas-filled eyes. The purpose of this study was to evaluate the capability of wide-field laser ophthalmoscopy (Optos in obtaining FAF images in gas-filled eyes for the assessment of macular hole (MH closure after surgery. Methods: This was an interventional case series. Eighteen consecutive patients with unilateral MH underwent vitrectomy with internal limiting membrane peeling and 20% sulfur hexafluoride gas tamponade. FAF images using Optos were recorded preoperatively and postoperatively (days 1, 2, and 7. Results: On postoperative days 1, 2, and 7, FAF images were obtained from 11/18 (61.1%, 9/18 (50.0%, and 17/18 eyes (94.4%, respectively, using Optos. The quality of FAF images using Optos was sufficient to determine MH closure in 9/18 (50.0% of gas-filled eyes postoperatively. Quantitative analysis of FAF images was helpful in determining complete or partial closure of the MH. Conclusion: FAF imaging using Optos might be a useful adjunct to optical coherence tomography as a supportive method to guide the release from facedown posturing in some cases of MH. Keywords: Optos, fundus autofluorescence, facedown, gas, vitrectomy

  3. Laser Spectroscopy Multi-Gas Monitor: Results of Technology Demonstration on ISS

    Science.gov (United States)

    Mudgett, Paul D.; Pilgrim, Jeffrey S.

    2015-01-01

    Tunable diode laser spectroscopy (TDLS) is an up and coming trace and major gas monitoring technology with unmatched selectivity, range and stability. The technology demonstration of the 4 gas Multi-Gas Monitor (MGM), reported at the 2014 ICES conference, operated continuously on the International Space Station (ISS) for nearly a year. The MGM is designed to measure oxygen, carbon dioxide, ammonia and water vapor in ambient cabin air in a low power, relatively compact device. While on board, the MGM experienced a number of challenges, unplanned and planned, including a test of the ammonia channel using a commercial medical ammonia inhalant. Data from the unit was downlinked once per week and compared with other analytical resources on board, notably the Major Constituent Analyzer (MCA), a magnetic sector mass spectrometer. MGM spent the majority of the time installed in the Nanoracks Frame 2 payload facility in front breathing mode (sampling the ambient environment of the Japanese Experiment Module), but was also used to analyze recirculated rack air. The capability of the MGM to be operated in portable mode (via internal rechargeable lithium ion polymer batteries or by plugging into any Express Rack 28VDC connector) was a part of the usability demonstration. Results to date show unprecedented stability and accuracy of the MGM vs. the MCA for oxygen and carbon dioxide. The ammonia challenge (approx. 75 ppm) was successful as well, showing very rapid response time in both directions. Work on an expansion of capability in a next generation MGM has just begun. Combustion products and hydrazine are being added to the measurable target analytes. An 8 to 10 gas monitor (aka Gas Tricorder 1.0) is envisioned for use on ISS, Orion and Exploration missions.

  4. Investigation of Gas Seeding for Planar Laser-Induced Fluorescence in Hypersonic Boundary Layers

    Science.gov (United States)

    Arisman, C. J.; Johansen, C. T.; Bathel, B. F.; Danehy, P. M.

    2015-01-01

    Numerical simulations of the gas-seeding strategies required for planar laser-induced fluorescence in a Mach 10 (approximately Mach 8.2 postshock) airflow were performed. The work was performed to understand and quantify the adverse effects associated with gas seeding and to assess various types of seed gas that could potentially be used in future experiments. In prior experiments, NO and NO2 were injected through a slot near the leading edge of a flatplate wedge model used in NASA Langley Research Center's 31 in. Mach 10 air tunnel facility. In this paper, nitric oxide, krypton, and iodine gases were simulated at various injection rates. Simulations showing the deflection of the velocity boundary layer for each of the cases are presented. Streamwise distributions of velocity and concentration boundary-layer thicknesses, as well as vertical distributions of velocity, temperature, and mass distributions, are presented for each of the cases. A comparison between simulated streamwise velocity profiles and experimentally obtained molecular tagging velocimetry profiles using a nitric oxide seeding strategy is performed to verify the influence of such a strategy on the boundary layer. The relative merits of the different seeding strategies are discussed. The results from a custom solver based on OpenFOAM version 2.2.1 are compared against results obtained from ANSYS® Fluent version 6.3.

  5. Laser-Plasma Interaction Experiments in Gas-Filled Hohlraums at the LIL Facility

    Science.gov (United States)

    Masson-Laborde, Paul-Edouard; Loiseau, Pascal; Casanova, Michel; Rousseaux, Christophe; Teychenne, Denis; Laffite, Stephane; Huser, Gael

    2009-11-01

    The first laser-plasma interaction campaign conducted at the LIL facility, using gas-filled hohlraums, ended in spring 09. Two different gas-filled hohlraums have been designed in order to mimic plasma conditions expected along two particular beam paths in ignition hohlraums. The targets consist of 3- or 4-millimeters long, 1 atm neo-pentane gas-filled gold hohlraums. The LIL quadruplet is aligned with the hohlraum's axis and delivers a 6-ns long pulse with 15 kJ at 3φ. Optical smoothing is achieved by longitudinal dispersion and a phase plate giving a near 10^15 W/cm^2 mean intensity on the focal spot at maximum power. Plasma conditions from hydrodynamic calculations allow to calcule SBS and SRS linear gain with the PIRANAH code. The calculated spectra are compared to experimental results. We use the paraxial code HERA to investigate the propagation of the LIL quad. Finally, 1D and 2D PIC simulations based on the plasma conditions of the cavity will be discussed in order to understand experimental SRS spectrum.

  6. The growth of human scalp hair mediated by visible red light laser and LED sources in males.

    Science.gov (United States)

    Lanzafame, Raymond J; Blanche, Raymond R; Bodian, Adam B; Chiacchierini, Richard P; Fernandez-Obregon, Adolfo; Kazmirek, Eric R

    2013-10-01

    Low level laser therapy (LLLT) has been used to promote hair growth. A double-blind randomized controlled trial was undertaken to define the safety and physiologic effects of LLLT on males with androgenic alopecia. Forty-four males (18-48 yo, Fitzpatrick I-IV, Hamilton-Norwood IIa-V) were recruited. A transition zone scalp site was selected; hairs were trimmed to 3 mm height; the area was tattooed and photographed. The active group received a "TOPHAT655" unit containing 21, 5 mW lasers (655 ± 5 nm), and 30 LEDS (655 ± 20 nm), in a bicycle-helmet like apparatus. The placebo group unit appeared identical, containing incandescent red lights. Patients treated at home every other day × 16 weeks (60 treatments, 67.3 J/cm(2) irradiance/25 minute treatment), with follow up and photography at 16 weeks. A masked 2.85 cm(2) photographic area was evaluated by another blinded investigator. The primary endpoint was the percent increase in hair counts from baseline. Forty-one patients completed the study (22 active, 19 placebo). No adverse events or side effects were reported. Baseline hair counts were 162.7 ± 95.9 (N = 22) in placebo and 142.0 ± 73.0 (N = 22) and active groups respectively (P = 0.426). Post Treatment hair counts were 162.4 ± 62.5 (N = 19) and 228.7 ± 102.8 (N = 22), respectively (P = 0.0161). A 39% percent hair increase was demonstrated (28.4 ± 46.2 placebo, N = 19; 67.2 ± 33.4, active, N = 22) (P = 0.001) Deleting one placebo group subject with a very high baseline count and a very large decrease, resulted in baseline hair counts of 151.1 ± 81.0 (N = 21) and 142.0 ± 73.0 (N = 22), respectively (P = 0.680). Post treatment hair counts were 158.2 ± 61.5 (N = 18) and 228.7 ± 102.8 (N = 22) (P = 0.011), resulting in a 35% percent increase in hair growth (32.3 ± 44.2, placebo, N = 18; 67.2 ± 33.4, active, N = 22) (P = 0.003). LLLT of the scalp at 655 nm significantly improved hair counts in males with androgenetic alopecia. © 2013 Wiley Periodicals

  7. Tin oxide thin films prepared by laser-assisted metal-organic CVD: Structural and gas sensing properties

    Czech Academy of Sciences Publication Activity Database

    Lančok, Ján; Santoni, A.; Penza, M.; Loreti, S.; Menicucci, I.; Minarini, C.; Jelínek, Miroslav

    2005-01-01

    Roč. 200, - (2005), s. 1057-1060 ISSN 0257-8972 R&D Projects: GA ČR(CZ) GP106/01/D017; GA MŠk(CZ) LN00A015 Institutional research plan: CEZ:AV0Z10100522 Keywords : tin dioxide * laser-assisted MOCVD * XPS * gas sensor Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.646, year: 2005

  8. Gas-phase thermal dissociation of uranium hexafluoride: Investigation by the technique of laser-powered homogeneous pyrolysis

    International Nuclear Information System (INIS)

    Bostick, W.D.; McCulla, W.H.; Trowbridge, L.D.

    1987-04-01

    In the gas-phase, uranium hexafluoride decomposes thermally in a quasi-unimolecular reaction to yield uranium pentafluoride and atomic fluorine. We have investigated this reaction using the relatively new technique of laser-powered homogeneous pyrolysis, in which a megawatt infrared laser is used to generate short pulses of high gas temperatures under strictly homogeneous conditions. In our investigation, SiF 4 is used as the sensitizer to absorb energy from a pulsed CO 2 laser and to transfer this energy by collisions with the reactant gas. Ethyl chloride is used as an external standard ''thermometer'' gas to permit estimation of the unimolecular reaction rate constants by a relative rate approach. When UF 6 is the reactant, CF 3 Cl is used as reagent to trap atomic fluorine reaction product, forming CF 4 as a stable indicator which is easily detected by infrared spectroscopy. Using these techniques, we estimate the UF 6 unimolecular reaction rate constant near the high-pressure limit. In the Appendix, we describe a computer program, written for the IBM PC, which predicts unimolecular rate constants based on the Rice-Ramsperger-Kassel theory. Parameterization of the theoretical model is discussed, and recommendations are made for ''appropriate'' input parameters for use in predicting the gas-phase unimolecular reaction rate for UF 6 as a function of temperature and gas composition and total pressure. 85 refs., 17 figs., 14 tabs

  9. A new in-gas-laser ionization and spectroscopy laboratory for off-line studies at KU Leuven

    Energy Technology Data Exchange (ETDEWEB)

    Kudryavtsev, Yu., E-mail: Yuri.Kudryavtsev@fys.kuleuven.be; Creemers, P.; Ferrer, R.; Granados, C.; Gaffney, L.P.; Huyse, M.; Mogilevskiy, E.; Raeder, S.; Sels, S.; Van den Bergh, P.; Van Duppen, P.; Zadvornaya, A.

    2016-06-01

    The in-gas laser ionization and spectroscopy (IGLIS) technique is used to produce and to investigate short-lived radioactive isotopes at on-line ion beam facilities. In this technique, the nuclear reaction products recoiling out of a thin target are thermalized and neutralized in a high-pressure noble gas, resonantly ionized by the laser beams in a two-step process, and then extracted from the ion source to be finally accelerated and mass separated. Resonant ionization of radioactive species in the supersonic gas jet ensures very high spectral resolution because of essential reduction of broadening mechanisms. To obtain the maximum efficiency and the best spectral resolution, properties of the supersonic jet and the laser beams must be optimized. To perform these studies a new off-line IGLIS laboratory, including a new high-repetition-rate laser system and a dedicated off-line mass separator, has been commissioned. In this article, the specifications of the different components necessary to achieve optimum conditions in laser-spectroscopy studies of radioactive beams using IGLIS are discussed and the results of simulations are presented.

  10. Population inversion and laser effect in gas flows due to explosion or detonation

    Science.gov (United States)

    Korobeinikov, V. P.; Podduev, M. I.

    The influence of the gas flow behind blast and detonation waves on population inversion of the vibrational levels of CO2 in a CO2-N2-He-H2O mixture was studied by the numerical solution of nonequilibrium gasdynamic equations. The following cases were examined: (1) the propagation of a cylindrical blast wave (generated by the explosion of cylindrically confined RDX or acetylene-oxygen mixture charges) in an active medium, (2) detonation wave propagation in a nozzle filled with a combustible mixture, and (3) expansion of acetylene-air mixture detonation products into vacuum. The optimization questions of gasdynamic processes and emission radiation in pulse gasdynamic lasers were discussed as well. The results suggest that the potential for a population inversion is influenced by the finite dimensions of the charge, the variations in density of the explosive mixture, and the opportunity for expansion of the active medium after shock heating.

  11. Creation of a Bose-condensed gas of87Rb by laser cooling.

    Science.gov (United States)

    Hu, Jiazhong; Urvoy, Alban; Vendeiro, Zachary; Crépel, Valentin; Chen, Wenlan; Vuletić, Vladan

    2017-11-24

    Protocols for attaining quantum degeneracy in atomic gases almost exclusively rely on evaporative cooling, a time-consuming final step associated with substantial atom loss. We demonstrate direct laser cooling of a gas of rubidium-87 ( 87 Rb) atoms to quantum degeneracy. The method is fast and induces little atom loss. The atoms are trapped in a two-dimensional optical lattice that enables cycles of compression to increase the density, followed by Raman sideband cooling to decrease the temperature. From a starting number of 2000 atoms, 1400 atoms reach quantum degeneracy in 300 milliseconds, as confirmed by a bimodal velocity distribution. The method should be broadly applicable to many bosonic and fermionic species and to systems where evaporative cooling is not possible. Copyright © 2017, American Association for the Advancement of Science.

  12. Analysis of pure tar substances (polycyclic aromatic hydrocarbons) in the gas stream using ultraviolet visible (UV-Vis) spectroscopy and multivariate curve resolution (MCR).

    Science.gov (United States)

    Weide, Tobias; Guschin, Viktor; Becker, Wolfgang; Koelle, Sabine; Maier, Simon; Seidelt, Stephan

    2015-01-01

    The analysis of tar, mostly characterized as polycyclic aromatic hydrocarbons (PAHs), describes a topic that has been researched for years. An online analysis of tar in the gas stream in particular is needed to characterize the tar conversion or formation in the biomass gasification process. The online analysis in the gas is carried out with ultraviolet-visible (UV-Vis) spectroscopy (190-720 nm). This online analysis is performed with a measuring cell developed by the Fraunhofer Institute for Chemical Technology (ICT). To this day, online tar measurements using UV-Vis spectroscopy have not been carried out in detail. Therefore, PAHs are analyzed as follows. The measurements are split into different steps. The first step to prove the online method is to vaporize single tar substances. These experiments show that a qualitative analysis of PAHs in the gas stream with the used measurement setup is possible. Furthermore, it is shown that the method provides very exact results, so that a differentiation of various PAHs is possible. The next step is to vaporize a PAH mixture. This step consists of vaporizing five pure substances almost simultaneously. The interpretation of the resulting data is made using a chemometric interpretation method, the multivariate curve resolution (MCR). The verification of the calculated results is the main aim of this experiment. It has been shown that the tar mixture can be analyzed qualitatively and quantitatively (in arbitrary units) in detail using the MCR. Finally it is the main goal of this paper to show the first steps in the applicability of the UV-Vis spectroscopy and the measurement setup on online tar analysis in view of characterizing the biomass gasification process. Due to that, the gasification plant (at the laboratory scale), developed and constructed by the Fraunhofer ICT, has been used to vaporize these substances. Using this gasification plant for the experiments enables the usage of the measurement setup also for the

  13. Effect of preionization, fluorine concentration, and current density on the discharge uniformity in F2 excimer laser gas mixtures

    NARCIS (Netherlands)

    Mathew, D.; Bastiaens, Hubertus M.J.; Boller, Klaus J.; Peters, P.J.M.

    2007-01-01

    The discharge homogeneity in F2-based excimer laser gas mixtures and its dependence on various key parameters, such as the degree of preionization, preionization delay time, F2 concentration and current density, is investigated in a small x-ray preionized discharge chamber. The spatial and temporal

  14. TECHNOLOGICAL ADVANCEMENT OF DEPOSIT WELDING AND GAS LASER CUTTING TO INCREASE THE EFFICIENCY OF THE BIMETALLIC TOOL PRODUCTION

    Directory of Open Access Journals (Sweden)

    Burlachenko Oleg Vasil’evich

    2017-08-01

    Full Text Available Deposit welding is the application of a layer of metal on the surface of a product using fusion welding. In this paper, we consider the method of improving the technology of gas laser cutting, which makes it possible to achieve a high productivity of manufacturing a bimetallic tool. The present paper is concerned with the advantages of gas laser cutting which allows to consider this particular process of separating materials as highly-productive, low-waste, and advanced method of removing allowances of weld-deposit high-speed steel on the working surfaces of bimetallic tool. Urgency of the use of deposit welding and gas laser cutting to improve the efficiency of production of bimetallic tool is shown. The comparative analysis of gas-laser cutting and other cutting methods is given according to the geometrical parameters of cutting and surface quality. Analysis of the results of experimental studies has confirmed the high technological attractiveness and economic efficiency of manufacturing composite structures of punches and matrices when applying deposit welding of cutting parts with high-speed steels. The cost of dimensional processing of the welded cutting part is reduced by 4 to 6 times, while the manufacturing time is reduced by 6 to 12 times.

  15. Quantitative measurement of carbon isotopic composition in CO2 gas reservoir by Micro-Laser Raman spectroscopy

    Science.gov (United States)

    Li, Jiajia; Li, Rongxi; Zhao, Bangsheng; Guo, Hui; Zhang, Shuan; Cheng, Jinghua; Wu, Xiaoli

    2018-04-01

    The use of Micro-Laser Raman spectroscopy technology for quantitatively determining gas carbon isotope composition is presented. In this study, 12CO2 and 13CO2 were mixed with N2 at various molar fraction ratios to obtain Raman quantification factors (F12CO2 and F13CO2), which provide a theoretical basis for calculating the δ13C value. And the corresponding values were 0.523 (0 CO2/CN2 CO2/CN2 CO2/12CO2 binary mixtures when F12CO2/F13CO2 is 0.466972625. In addition, measurement of δ13C values by Micro-Laser Raman analysis were carried out on natural CO2 gas from Shengli Oil-field at room temperature under different pressures. The δ13C values obtained by Micro-Laser Raman spectroscopy technology and Isotope Ratio Mass Spectrometry (IRMS) technology are in good agreement with each other, and the relative errors range of δ13C values is 1.232%-6.964%. This research provides a fundamental analysis tool for determining gas carbon isotope composition (δ13C values) quantitatively by using Micro-Laser Raman spectroscopy. Experiment of results demonstrates that this method has the potential for obtaining δ13C values in natural CO2 gas reservoirs.

  16. Present status of rarefied gas dynamics approach to the structure of a laser-induced evaporating jet

    International Nuclear Information System (INIS)

    Cercignani, C.

    1980-01-01

    With reference to the relation between the state of the surface and the measurements downstream in the dynamic laser pulse technique, the problems arising in connection with the study of the structure of a jet evaporating into a vacuum are investigated. Particular attention is paid to the following aspects gas surface interaction, internal degrees of freedom, presence of more than one species, chemical reactions

  17. Gas-phase laser synthesis of aggregation-free, size-controlled hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    Bapat, Parimal V.; Kraft, Rebecca; Camata, Renato P.

    2012-01-01

    Nanophase hydroxyapatite (HA) is finding applications in many areas of biomedical research, including bone tissue engineering, drug delivery, and intracellular imaging. Details in chemical composition, crystal phase makeup, size, and shape of HA nanoparticles play important roles in achieving the favorable biological responses required in these applications. Most of the nanophase HA synthesis techniques involve solution-based methods that exhibit substantial aggregation of particles upon precipitation. Typically these methods also have limited control over the particle size and crystal phase composition. In this study, we describe the gas-phase synthesis of aggregation-free, size-controlled HA nanoparticles with mean size in the 20–70 nm range using laser ablation followed by aerosol electrical mobility classification. Nanoparticle deposits with adjustable number concentration were obtained on solid substrates. Particles were characterized by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. Samples are well represented by log-normal size distributions with geometric standard deviation σ g ≈ 1.2. The most suitable conditions for HA nanoparticle formation at a laser fluence of 5 J/cm 2 were found to be a temperature of 800 °C and a partial pressure of water of 160 mbar.

  18. High speed engine gas thermometry by Fourier-domain mode-locked laser absorption spectroscopy.

    Science.gov (United States)

    Kranendonk, Laura A; An, Xinliang; Caswell, Andrew W; Herold, Randy E; Sanders, Scott T; Huber, Robert; Fujimoto, James G; Okura, Yasuhiro; Urata, Yasuhiro

    2007-11-12

    We present a novel method for low noise, high-speed, real-time spectroscopy to monitor molecular absorption spectra. The system is based on a rapidly swept, narrowband CW Fourier-domain mode-locked (FDML) laser source for spectral encoding in time and an optically time-multiplexed split-pulse data acquisition system for improved noise performance and sensitivity. An acquisition speed of ~100 kHz, a spectral resolution better than 0.1 nm over a wavelength range of ~1335-1373 nm and a relative noise level of ~5 mOD (~1% minimum detectable base-e absorbance) are achieved. The system is applied for crank-angle-resolved gas thermometry by H(2)O absorption spectroscopy in an engine motoring at 600 and 900 rpm with a precision of ~1%. Influences of various noise sources such as laser phase and intensity noise, trigger and synchronization jitter in the electronic detection system, and the accuracy of available H(2)O absorption databases are discussed.

  19. Surface patterning of Zr-based metallic glass by laser irradiation induced selective thermoplastic extrusion in nitrogen gas

    Science.gov (United States)

    Huang, Hu; Yan, Jiwang

    2017-07-01

    Hierarchical surface structures on metallic glass (MG) are useful for enhancing the material’s functions. In this paper, surface patterning of Zr-based MG was realized by nanosecond pulsed laser irradiation in nitrogen gas. Experimental results showed that three kinds of surface structures, namely, micro grooves, cross-shaped protrusions, and nanoparticles, were generated on the MG surface under specific laser scanning speeds and various laser power intensities and pulse overlap rates. In particular, the formation of cross-shaped protrusions has never been reported in the literature before. The formation mechanism for each kind of surface structure was investigated. In a nitrogen gas environment, cracks are easily generated and the cracked regions have higher laser absorption and localized thermal resistivity than those of the bulk material. Accordingly, the cross-shaped protrusions were ascribed to the selective thermoplastic extrusion of MG material out of the cracks and the laser pulse tracks formed by the preceding laser scans. It was found that the hierarchical surface structures significantly improved the surface hydrophobicity.

  20. Effects of wavelength, beam type and size on cerebral low-level laser therapy by a Monte Carlo study on visible Chinese human

    Directory of Open Access Journals (Sweden)

    Ting Li

    2015-01-01

    Full Text Available Low-level laser therapy (LLLT has been clinically utilized for many indications in medicine requiring protection from cell/tissue death, stimulation of healing and repair of injuries, pain reduction, swelling and inflammation. Presently, the use of LLLT to treat stroke, traumatic brain injury and cognitive dysfunction are attracting growing interest. Near-infrared light is capable of penetrating into the cerebral cortex, allowing noninvasive treatments to be carried out with few treatment-related adverse events. Optimization of LLLT treatment effect is a crucial issue of this field; however, only a few experimental tests on mice for wavelength selection have been reported. We addressed this issue by low-cost, straightforward and quantitative comparisons on light dosage distribution within visible Chinese human head by Monte Carlo modeling of near-infrared light propagation. Optimized selection in wavelength, beam type and size were given based on comparisons among frequently used setups (i.e., wavelengths: 660, 810 and 980 nm; beam type: Gaussian and flat beam; beam diameter: 2, 4 and 6 cm. This study provided an efficient way for guiding the optimization of LLLT setup and selection on wavelength, beam type and size for clinical brain LLLT.

  1. High resolution temperature mapping of gas turbine combustor simulator exhaust with femtosecond laser induced fiber Bragg gratings

    Science.gov (United States)

    Walker, Robert B.; Yun, Sangsig; Ding, Huimin; Charbonneau, Michel; Coulas, David; Lu, Ping; Mihailov, Stephen J.; Ramachandran, Nanthan

    2017-04-01

    Femtosecond infrared (fs-IR) laser written fiber Bragg gratings (FBGs), have demonstrated great potential for extreme sensing. Such conditions are inherent in advanced gas turbine engines under development to reduce greenhouse gas emissions; and the ability to measure temperature gradients in these harsh environments is currently limited by the lack of sensors and controls capable of withstanding the high temperature, pressure and corrosive conditions present. This paper discusses fabrication and deployment of several fs-IR written FBG arrays, for monitoring exhaust temperature gradients of a gas turbine combustor simulator. Results include: contour plots of measured temperature gradients, contrast with thermocouple data.

  2. Effect of laser fluence and ambient gas pressure on surface morphology and chemical composition of hydroxyapatite thin films deposited using pulsed laser deposition

    Science.gov (United States)

    Nishikawa, Hiroaki; Hasegawa, Tsukasa; Miyake, Akiko; Tashiro, Yuichiro; Komasa, Satoshi; Hashimoto, Yoshiya

    2018-01-01

    The dependence of the surface morphology and chemical composition of hydroxyapatite (HA) thin films on the laser fluence and ambient gas pressure during their formation by pulsed laser deposition was studied as the first step to investigate the effect of physical and chemical interactions between the ablated chemical species and ambient gas molecules on HA film formation. It was found that a higher fluence could decrease the number of large protrusions on the surface of HA thin films. However, too high a fluence caused a phosphorus deficiency from the stoichiometric value, particularly in the case of lower ambient gas pressure. It was also found that for lower fluences, the atomic species among the ablated chemical species were easily scattered by collision processes with ambient gas molecules. This was caused by the lower velocity of the ablated chemical species and higher ambient gas pressure, which induced a shorter mean free path. In addition, these collision processes played an important role in the adsorption, migration, and re-evaporation of the ablated chemical species on the substrate via chemical reactions.

  3. Note: Real-time monitoring via second-harmonic interferometry of a flow gas cell for laser wakefield acceleration.

    Science.gov (United States)

    Brandi, F; Giammanco, F; Conti, F; Sylla, F; Lambert, G; Gizzi, L A

    2016-08-01

    The use of a gas cell as a target for laser wakefield acceleration (LWFA) offers the possibility to obtain stable and manageable laser-plasma interaction process, a mandatory condition for practical applications of this emerging technique, especially in multi-stage accelerators. In order to obtain full control of the gas particle number density in the interaction region, thus allowing for a long term stable and manageable LWFA, real-time monitoring is necessary. In fact, the ideal gas law cannot be used to estimate the particle density inside the flow cell based on the preset backing pressure and the room temperature because the gas flow depends on several factors like tubing, regulators, and valves in the gas supply system, as well as vacuum chamber volume and vacuum pump speed/throughput. Here, second-harmonic interferometry is applied to measure the particle number density inside a flow gas cell designed for LWFA. The results demonstrate that real-time monitoring is achieved and that using low backing pressure gas (<1 bar) and different cell orifice diameters (<2 mm) it is possible to finely tune the number density up to the 10(19) cm(-3) range well suited for LWFA.

  4. Note: Real-time monitoring via second-harmonic interferometry of a flow gas cell for laser wakefield acceleration

    Science.gov (United States)

    Brandi, F.; Giammanco, F.; Conti, F.; Sylla, F.; Lambert, G.; Gizzi, L. A.

    2016-08-01

    The use of a gas cell as a target for laser wakefield acceleration (LWFA) offers the possibility to obtain stable and manageable laser-plasma interaction process, a mandatory condition for practical applications of this emerging technique, especially in multi-stage accelerators. In order to obtain full control of the gas particle number density in the interaction region, thus allowing for a long term stable and manageable LWFA, real-time monitoring is necessary. In fact, the ideal gas law cannot be used to estimate the particle density inside the flow cell based on the preset backing pressure and the room temperature because the gas flow depends on several factors like tubing, regulators, and valves in the gas supply system, as well as vacuum chamber volume and vacuum pump speed/throughput. Here, second-harmonic interferometry is applied to measure the particle number density inside a flow gas cell designed for LWFA. The results demonstrate that real-time monitoring is achieved and that using low backing pressure gas (<1 bar) and different cell orifice diameters (<2 mm) it is possible to finely tune the number density up to the 1019 cm-3 range well suited for LWFA.

  5. Comparison of Plasma, Metal Inactive Gas (MIG) and Tungsten Inactive Gas (TIG) Processes for Laser Hybrid Welding (302)

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    2003-01-01

    source, ignition and running torch stability, weld phase transformation and change in ductility and overall weld quality are described. The results show that all three processes can successfully be integrated with a CO2 laser beam for hybrid welding. Due to the pilot arc in plasma welding, this process......, the MIG process is more difficult to control than laser/plasma and laser/TIG processes. All three types of secondary heat sources enable an increased ductility of the weld as compared to pure laser welding when welding 1.8 mm GA 260 with a TIG torch and 2.13 mm CMn steel with a plasma arc or MIG...

  6. Ambient gas effects on the dynamics of laser-produced tin plume expansion

    International Nuclear Information System (INIS)

    Harilal, S. S.; O'Shay, Beau; Tao Yezheng; Tillack, Mark S.

    2006-01-01

    Controlling the debris from a laser-generated tin plume is one of the prime issues in the development of an extreme ultraviolet lithographic light source. An ambient gas that is transparent to 13.5 nm radiation can be used for controlling highly energetic particles from the tin plume. We employed a partial ambient argon pressure for decelerating various species in the tin plume. The kinetic energy distributions of tin species were analyzed at short and large distances using time and space resolved optical emission spectroscopy and a Faraday cup, respectively. A fast-gated intensified charged coupled device was used for understanding the hydrodynamics of the plume's expansion into argon ambient. Our results indicate that the tin ions can be effectively mitigated with a partial argon pressure ∼65 mTorr. Apart from thermalization and deceleration of plume species, the addition of ambient gas leads to other events such as double peak formation in the temporal distributions and ambient plasma formation

  7. In situ laser measurement of oxygen concentration and flue gas temperature utilizing chemical reaction kinetics.

    Science.gov (United States)

    Viljanen, J; Sorvajärvi, T; Toivonen, J

    2017-12-01

    Combustion research requires detailed localized information on the dynamic combustion conditions to improve the accuracy of the simulations and, hence, improve the performance of the combustion processes. We have applied chemical reaction kinetics of potassium to measure the local temperature and O 2 concentration in flue gas. An excess of free atomic potassium is created in the measurement volume by a photofragmenting precursor molecule such as potassium chloride or KOH which are widely released from solid fuels. The decay of the induced potassium concentration is followed with an absorption measurement using a narrow-linewidth diode laser. The temperature and O 2 concentration are solved from the decay curve features using equations obtained from calibration measurements in a temperature range of 800°C-1000°C and in O 2 concentrations of 0.1%-21%. The local flue gas temperature and O 2 concentration were recorded in real time during devolatilization, char burning, and ash cooking phases of combustion in a single-particle reactor with a 5 Hz repetition rate. The method can be further extended to other target species and applications where the chemical dynamics can be disturbed with photofragmentation.

  8. Application of additive laser technologies in the gas turbine blades design process

    Science.gov (United States)

    Shevchenko, I. V.; Rogalev, A. N.; Osipov, S. K.; Bychkov, N. M.; Komarov, I. I.

    2017-11-01

    An emergence of modern innovative technologies requires delivering new and modernization existing design and production processes. It is especially relevant for designing the high-temperature turbines of gas turbine engines, development of which is characterized by a transition to higher parameters of working medium in order to improve their efficient performance. A design technique for gas turbine blades based on predictive verification of thermal and hydraulic models of their cooling systems by testing of a blade prototype fabricated using the selective laser melting technology was presented in this article. Technique was proven at the time of development of the first stage blade cooling system for the high-pressure turbine. An experimental procedure for verification of a thermal model of the blades with convective cooling systems based on the comparison of heat-flux density obtained from the numerical simulation data and results of tests in a liquid-metal thermostat was developed. The techniques makes it possible to obtain an experimentally tested blade version and to exclude its experimental adjustment after the start of mass production.

  9. Electron kinetics dependence on gas pressure in laser-induced oxygen plasma experiment: Theoretical analysis

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Abdellatif, Galila

    2017-08-01

    A study is performed to investigate the dependency of threshold intensity on gas pressure observed in the measurements of the breakdown of molecular oxygen that carried out by Phuoc (2000) [1]. In this experiment, the breakdown was induced by 532 nm laser radiation of pulse width 5.5 ns and spot size of 8.5 μm, in oxygen over a wide pressure range (190-3000 Torr). The analysis aimed to explore the electron kinetic reliance on gas pressure for the separate contribution of each of the gain and loss processes encountered in this study. The investigation is based on an electron cascade model applied previously in Gamal and Omar (2001) [2] and Gaabour et al. (2013) [3]. This model solves numerically a differential equation designates the time evolution of the electron energy distribution, and a set of rate equations that describe the change of excited states population. The numerical examination of the electron energy distribution function and its parameters revealed that photo-ionization of the excited molecules plays a significant role in enhancing the electron density growth rate over the whole tested gas pressure range. This process is off set by diffusion of electrons out of the focal volume in the low-pressure regime. At atmospheric pressure electron, collisional processes dominate and act mainly to populate the excited states. Hence photo-ionization becomes efficient and compete with the encountered loss processes (electron diffusion, vibrational excitation of the ground state molecules as well as two body attachments). At high pressures ( 3000 Torr) three body attachments are found to be the primary cause of losses which deplete the electron density and hence results in the slow decrease of the threshold intensity.

  10. Surface modification of the titanium implant using TEA CO 2 laser pulses in controllable gas atmospheres - Comparative study

    Science.gov (United States)

    Ciganovic, J.; Stasic, J.; Gakovic, B.; Momcilovic, M.; Milovanovic, D.; Bokorov, M.; Trtica, M.

    2012-01-01

    Interaction of a TEA CO2 laser, operating at 10.6 μm wavelength and pulse duration of 100 ns (FWHM), with a titanium implant in various gas atmospheres was studied. The Ti implant surface modification was typically studied at the moderate laser beam energy density/fluence of 28 J/cm2 in the surrounding of air, N2, O2 or He. The energy absorbed from the TEA CO2 laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium implant surface changes and phenomena were observed, depending on the gas used: (i) creation of cone-like surface structures in the atmospheres of air, N2 and O2, and dominant micro-holes/pores in He ambient; (ii) hydrodynamic features, most prominent in air; (iii) formation of titanium nitride and titanium oxide layers, and (iv) occurrence of plasma in front of the implant. It can be concluded from this study that the reported laser fluence and gas ambiences can effectively be applied for enhancing the titanium implant roughness and creation of titanium oxides and nitrides on the strictly localized surface area. The appearance of plasma in front of the implants indicates relatively high temperatures created above the surface. This offers a sterilizing effect, facilitating contaminant-free conditions.

  11. Femtosecond laser-induced cavitations in the lens of the human eye

    DEFF Research Database (Denmark)

    Kessel, Line; Nymand, Jose; Harbst, Michael

    2007-01-01

    Ultrafast femtosecond lasers are used increasingly for a wide range of medicai purposes. The immediate tissue response to pulses above a certain threshold is optically or laser induced breakdown, which is often visible as gas-filled cavities that persist for some time. In the present study, we at...

  12. Quantitative study of the ionization-induced refraction of picosecond laser pulses in gas-jet targets

    International Nuclear Information System (INIS)

    Mackinnon, A.J.; Borghesi, M.; Iwase, A.; Jones, M.W.; Pert, G.J.; Rae, S.; Burnett, K.; Willi, O.

    1996-01-01

    A quantitative study of refractive whole beam defocusing and small scale breakup induced by optical ionization of subpicosecond and picosecond, 0.25 and 1 μm, laser pulses in gas-jet targets at densities above 1x10 19 cm -3 has been carried out. A significant reduction of the incident laser intensity was observed due to refraction from ionization-induced density gradients. The level of refraction measured with optical probing correlated well with the fraction of energy transmitted through the plasma. The numerical and analytical models were found to agree well with experimental observations. copyright 1996 The American Physical Society

  13. Development of an on-line low gas pressure cell for laser ablation-ICP-mass spectrometry

    International Nuclear Information System (INIS)

    Hirata, Takafumi

    2007-01-01

    An on-line low gas pressure cell device has been developed for elemental analysis using laser ablation-ICP-mass spectrometry (LA-ICPMS). Ambient gas in the sample cell was evacuated by a constant-flow diaphragm pump, and the pressure of the sample cell was controlled by changing the flow rate of He-inlet gas. The degree of sample re-deposition around the ablation pit could be reduced when the pressure of the ambient gas was lower than 50 kPa. Produced sample aerosol was drawn and taken from the outlet of the diaphragm pump, and directly introduced into the ICP ion source. The flow rate of He gas controls not only the gas pressure in the sample cell, but also the transport efficiency of the sample particles from the cell to the ICP, and the gas flow rate must be optimized to maximize the signal intensity of the analytes. The flow rates of the He carrier and Ar makeup gas were tuned to maximize the signal intensity of the analytes, and in the case of 238 U from the NIST SRM610 glass material, the signal intensity could be maximized with gas flow rates of 0.4 L/min for He and 1.2 L/min for Ar. The resulting gas pressure in the cell was 30-35 kPa. Using the low gas pressure cell device, the stability in the signal intensities and the resulting precision in isotopic ratio measurements were evaluated. The signal intensity profile of 63 Cu obtained by laser ablation from a metallic sample (NIST SRM976) demonstrated that typical spikes in the transient signal, which can become a large source of analytical error, were no longer found. The resulting precision in the 65 Cu/ 63 Cu ratio measurements was 2-3% (n=10, 2SD), which was half on the level obtained by laser ablation under atmospheric pressure (6-10%). The newly developed low-pressure cell device provides easier optimization of the operational conditions, together with smaller degrees of sample re-deposition and better stability in the signal intensity, even from a metallic sample. (author)

  14. Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy.

    Science.gov (United States)

    Hsu, Paul S; Kulatilaka, Waruna D; Jiang, Naibo; Gord, James R; Roy, Sukesh

    2012-06-20

    We investigate the feasibility of transmitting high-power, ultraviolet (UV) laser pulses through long optical fibers for laser-induced-fluorescence (LIF) spectroscopy of the hydroxyl radical (OH) and nitric oxide (NO) in reacting and non-reacting flows. The fundamental transmission characteristics of nanosecond (ns)-duration laser pulses are studied at wavelengths of 283 nm (OH excitation) and 226 nm (NO excitation) for state-of-the-art, commercial UV-grade fibers. It is verified experimentally that selected fibers are capable of transmitting sufficient UV pulse energy for single-laser-shot LIF measurements. The homogeneous output-beam profile resulting from propagation through a long multimode fiber is ideal for two-dimensional planar-LIF (PLIF) imaging. A fiber-coupled UV-LIF system employing a 6 m long launch fiber is developed for probing OH and NO. Single-laser-shot OH- and NO-PLIF images are obtained in a premixed flame and in a room-temperature NO-seeded N(2) jet, respectively. Effects on LIF excitation lineshapes resulting from delivering intense UV laser pulses through long fibers are also investigated. Proof-of-concept measurements demonstrated in the current work show significant promise for fiber-coupled UV-LIF spectroscopy in harsh diagnostic environments such as gas-turbine test beds.

  15. Laser gas-assisted processing of carbon coated and TiC embedded Ti-6Al-4V alloy surface

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [Mechanical Engineering Department, King Fahd University of Petroleum and Minerals (Saudi Arabia); Akhtar, S.; Aleem, B.J. Abdul [Mechanical Engineering Department, King Fahd University of Petroleum and Minerals (Saudi Arabia); Karatas, C. [Faculty of Engineering, Hacettepe University (Turkey)

    2010-11-01

    Laser gas-assisted treatment of Ti-6Al-4V alloy surface is carried out. The alloy surface is initially coated by a carbon layer, in which the TiC particles are embedded prior to laser processing of the surface. The carbon coating with the presence of TiC particles on the workpiece surface is expected to result in carbonitride compound in the surface vicinity after the laser treatment process. Optical and scanning electron microscopes are used to examine the morphological and the metallurgical changes in the laser treated layer. The residual stress formed in the surface region after the laser treatment process is critical for the practical applications of the resulting surface. Therefore, the residual stress formed in the laser treated region is predicted from the analytically equation. The X-ray diffraction technique is incorporated to obtain the residual stress formed in the surface region. It is found that the residual stress predicted agrees with the X-ray diffraction data. The dense structures consisting of TiC{sub x}N{sub 1-x}, TiN{sub x}, Ti{sub 2}N, and TiC compounds are formed in the surface region of the treated layer. This, in turn, significantly increases the microhardness at the surface.

  16. Applications of laser-photoacoustic gas analysis method; Fotoakustisen kaasuanalyysin sovelluksia. Fotoakustiset mittaukset paineistetussa poelyvirtausreaktorissa

    Energy Technology Data Exchange (ETDEWEB)

    Hernberg, R.; Stenberg, J. [Tampere Univ. of Technology (Finland). Lab. of Plasma Technology

    1997-10-01

    Laser induced photoacoustic spectroscopy has been developed in LIEKKI and LIEKKI 2 research programs. The method is intended for In-Situ analysis of gaseous components in hot and reactive environments such as combustion conditions. The method and the instrumentation developed in this project have been calibrated for SO{sub 2}, NO, NO{sub 2}, NH{sub 3}, N{sub 2}O, and H{sub 2}S between 20 and 860 deg C at atmospheric pressure. Calibrations at elevated pressures have been performed for NO{sub 2}, NO, SO{sub 2}, NH{sub 3} and N{sub 2}O. Calibration for OH radical has also been performed. A known concentration of OH was generated by thermally decomposing H{sub 2}O at temperatures between 900 and 1050 deg C. The photoacoustic method has earlier been applied to the chemical analysis of burning CH{sub 4}/HCN/O{sub 2}/N{sub 2} flame at pressures between 1 and 6 bar. The formation of NO and NH{sub 3} measured in post-flame conditions. The relative concentration of OH in the reactive zone of the flame was measured between 1 and 6 bar pressures. The method was also applied to measurements in circulating fluidized bed (CFB). Time resolved gas concentrations were measured at three different heights above the air distributor with a specialized probe. In this project the photoacoustic method is applied in studies regarding the effect of chlorine (Cl) on combustion chemistry. The second goal of this project is to make In-Situ measurements of the formation of NO{sub 2} in combustion. The formation of NO{sub 2} increases strongly at elevated pressures. Due to the instability of NO{sub 2} the analysis is prone to errors with conventional gas sampling probes

  17. Parametric thermodynamic analysis of closed-cycle gas-laser operation in space

    Science.gov (United States)

    Burns, R. K.

    1974-01-01

    Cycle efficiency and radiator area required were calculated for thermally and electrically pumped lasers operating in closed cycles with a compressor and the required heat exchangers. A thermally pumped laser included within a Brayton cycle was also analyzed. Performance of all components, including the laser, was parametrically varied. For the thermally pumped laser the cycle efficiencies range below 10 percent and are very sensitive to the high-pressure losses associated with the supersonic diffuser required at the laser cavity exit. The efficiencies predicted for the electrically pumped laser cycles range slightly higher, but radiator area also tends to be larger.

  18. Noninvasive monitoring of gas in the lungs and intestines of newborn infants using diode lasers: feasibility study

    Science.gov (United States)

    Lundin, Patrik; Svanberg, Emilie Krite; Cocola, Lorenzo; Xu, Märta Lewander; Somesfalean, Gabriel; Andersson-Engels, Stefan; Jahr, John; Fellman, Vineta; Svanberg, Katarina; Svanberg, Sune

    2013-12-01

    Preterm newborn infants have a high morbidity rate. The most frequently affected organs where free gas is involved are the lungs and intestines. In respiratory distress syndrome, both hyperexpanded and atelectatic (collapsed) areas occur, and in necrotizing enterocolitis, intramural gas may appear in the intestine. Today, these conditions are diagnosed with x-ray radiography. A bed-side, rapid, nonintrusive, and gas-specific technique for in vivo gas sensing would improve diagnosis. We report the use of noninvasive laser spectroscopy, for the first time, to assess gas content in the lungs and intestines of three full-term infants. Water vapor and oxygen were studied with two low-power diode lasers, illuminating the skin and detecting light a few centimeters away. Water vapor was easily detected in the intestines and was also observed in the lungs. The relatively thick chest walls of the infants prevented detection of the weaker oxygen signal in this study. However, results from a previous phantom study, together with scaling of the results presented here to the typical chest-wall thickness of preterm infants, suggest that oxygen also should be detectable in their lungs.

  19. Two dimensional laser induced fluorescence in the gas phase: a spectroscopic tool for studying molecular spectroscopy and dynamics

    Science.gov (United States)

    Gascooke, Jason R.; Lawrance, Warren D.

    2017-11-01

    Two dimensional laser induced fluorescence (2D-LIF) extends the usual laser induced fluorescence technique by adding a second dimension, the wavelength at which excited states emit, thereby significantly enhancing the information that can be extracted. It allows overlapping absorption features, whether they arise from within the same molecule or from different molecules in a mixture, to be associated with their appropriate "parent" state and/or molecule. While the first gas phase version of the technique was published a decade ago, the technique is in its infancy, having been exploited by only a few groups to date. However, its potential in gas phase spectroscopy and dynamics is significant. In this article we provide an overview of the technique and illustrate its potential with examples, with a focus on those utilising high resolution in the dispersed fluorescence dimension.

  20. Femtosecond laser induced breakdown spectroscopy of silver within surrogate high temperature gas reactor fuel coated particles

    International Nuclear Information System (INIS)

    Roberts, D.E.; Plessis, A. du; Steyn, J.; Botha, L.R.; Strydom, C.A.; Rooyen, I.J. van

    2010-01-01

    The detection of metallic silver on Chemical Vapour Deposited (CVD) grown silicon carbide and in Pebble Bed Modular Reactor (PBMR) supplied tri-structural isotropic (TRISO) coated particles (with 500 μm diameter zirconium oxide surrogate kernel) has been studied with femtosecond Laser Induced Breakdown Spectroscopy (femto-LIBS). The SiC layer of the TRISO coated particle is the main barrier to metallic and gaseous fission products of which 110m Ag is of particular interest for direct cycle high temperature reactors. This work is a feasibility study for diagnosing and profiling silver transport through the silicon carbide layer of fuel particles for a high temperature gas reactor in out-of-reactor experimentation. The zirconium oxide is a surrogate for the enriched uranium oxide fuel. The conclusion reached in this study was that femto-LIBS can achieve good surface spatial resolution and good depth resolution for studies of silver in experimental coated particles. The LIBS technique also offers a good alternative for a remote analytical technique.

  1. Tunable Diode Laser Sensors to Monitor Temperature and Gas Composition in High-Temperature Coal Gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, Ronald [Stanford Univ., CA (United States); Whitty, Kevin [Univ. of Utah, Salt Lake City, UT (United States)

    2014-12-01

    The integrated gasification combined cycle (IGCC) when combined with carbon capture and storage can be one of the cleanest methods of extracting energy from coal. Control of coal and biomass gasification processes to accommodate the changing character of input-fuel streams is required for practical implementation of integrated gasification combined-cycle (IGCC) technologies. Therefore a fast time-response sensor is needed for real-time monitoring of the composition and ideally the heating value of the synthesis gas (here called syngas) as it exits the gasifier. The goal of this project was the design, construction, and demonstration an in situ laserabsorption sensor to monitor multiple species in the syngas output from practical-scale coal gasifiers. This project investigated the hypothesis of using laser absorption sensing in particulateladen syngas. Absorption transitions were selected with design rules to optimize signal strength while minimizing interference from other species. Successful in situ measurements in the dusty, high-pressure syngas flow were enabled by Stanford’s normalized and scanned wavelength modulation strategy. A prototype sensor for CO, CH4, CO2, and H2O was refined with experiments conducted in the laboratory at Stanford University, a pilot-scale at the University of Utah, and an engineering-scale gasifier at DoE’s National Center for Carbon Capture with the demonstration of a prototype sensor with technical readiness level 6 in the 2014 measurement campaign.

  2. Urban air pollution monitoring: laser-based procedure for the detection of carbon monoxide gas.

    Science.gov (United States)

    Peng, W X; Ledingham, K W; Singhal, R P; McCanny, T

    1998-05-01

    Urban air quality is of considerable importance in many cities throughout Europe and the USA. In particular, current EU legislation has driven an expansion of monitoring of more pollutants at more sites. At present in the UK, real time readings are now available for benzene, buta-1,3-diene and other volatile organic compounds, airborne fine dust (PM10), CO, 03, SO2, and NOX. Carbon monoxide is produced to varying degrees in all combustion processes but more than 90% is caused by emissions from petrol vehicle exhausts. The World Health Ogranisation guidelines for exposure to the gas is pollutants mentioned above are monitored by different detection techniques and it has been the authors' philosophy to develop instrumentation which can monitor all the different pollutants using a single detector. To this end, a multiphoton laser based procedure, using simple ionization chambers, has been developed to detect the different pollutants with different wavelengths. For CO, a 2 + 1 resonance enhanced multiphoton ionization (REMPI) scheme at 230 nm can be used with detection limits of about 1 ppm.

  3. The effects of focusing power on TEA CO2 laser-induced gas breakdown and the consequent pulse shaping effects

    Science.gov (United States)

    Beheshtipour, Saleheh; Safari, Ebrahim; Majdabadi, Abbas; Silakhori, Kaveh

    2018-02-01

    Transversely Excited Atmospheric (TEA) CO2 laser pulses were used in order to generate an optical breakdown in a variety of mono- and polyatomic molecules using different focusing powers. The dependence of the spark kernel geometry and the transmitted pulse shapes on the focusing power as well as the pressure, molecular weight, and ionization energy of the gases was investigated in detail. Partial removal of the transmitted pulse tail in the 0.05-2.6 μs range together with shortened spikes in the 10-60 ns range has been observed by applying a 2.5 cm focal length lens for all the gases. At higher focal lengths, this effect is only incompletely observed for He gas. Spatial-temporal analyses of the laser beams and the relevant plasma plumes indicate that this behavior is due to the drop in the plasma density below the critical level, before the laser pulse tail is completed.

  4. Functional model for gas sensing based on quantum cascade lasers; Funktionsmuster zur Gasdetektion auf Basis von Quantenkaskadenlasern

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, T.; Rohr, J. [m.u.t. GmbH, Wedel (Germany)

    2005-06-01

    Quantum cascade lasers represent an almost ideal light source for infrared gas analysis. They allow sensitive and selective measurements in the mid-infrared. The detection of combustion gases for early fire detection represents an interesting field of application, where further technologic benefits are shown to advantage. The focus of this report is on the technical realization of a functional model and the electronic components. (orig.)

  5. Quantitative measurement of carbon isotopic composition in CO2gas reservoir by Micro-Laser Raman spectroscopy.

    Science.gov (United States)

    Li, Jiajia; Li, Rongxi; Zhao, Bangsheng; Guo, Hui; Zhang, Shuan; Cheng, Jinghua; Wu, Xiaoli

    2018-04-15

    The use of Micro-Laser Raman spectroscopy technology for quantitatively determining gas carbon isotope composition is presented. In this study, 12 CO 2 and 13 CO 2 were mixed with N 2 at various molar fraction ratios to obtain Raman quantification factors (F 12CO2 and F 13CO2 ), which provide a theoretical basis for calculating the δ 13 C value. And the corresponding values were 0.523 (0Laser Raman analysis were carried out on natural CO 2 gas from Shengli Oil-field at room temperature under different pressures. The δ 13 C values obtained by Micro-Laser Raman spectroscopy technology and Isotope Ratio Mass Spectrometry (IRMS) technology are in good agreement with each other, and the relative errors range of δ 13 C values is 1.232%-6.964%. This research provides a fundamental analysis tool for determining gas carbon isotope composition (δ 13 C values) quantitatively by using Micro-Laser Raman spectroscopy. Experiment of results demonstrates that this method has the potential for obtaining δ 13 C values in natural CO 2 gas reservoirs. Copyright © 2018. Published by Elsevier B.V.

  6. Flame kernel characterization of laser ignition of natural gas-air mixture in a constant volume combustion chamber

    Science.gov (United States)

    Srivastava, Dhananjay Kumar; Dharamshi, Kewal; Agarwal, Avinash Kumar

    2011-09-01

    In this paper, laser-induced ignition was investigated for compressed natural gas-air mixtures. Experiments were performed in a constant volume combustion chamber, which simulate end of the compression stroke conditions of a SI engine. This chamber simulates the engine combustion chamber conditions except turbulence of air-fuel mixture. It has four optical windows at diametrically opposite locations, which are used for laser ignition and optical diagnostics simultaneously. All experiments were conducted at 10 bar chamber pressure and 373 K chamber temperature. Initial stage of combustion phenomena was visualized by employing Shadowgraphy technique using a high speed CMOS camera. Flame kernel development of the combustible fuel-air mixture was investigated under different relative air-fuel ratios ( λ=1.2-1.7) and the images were interrogated for temporal propagation of flame front. Pressure-time history inside the combustion chamber was recorded and analyzed. This data is useful in characterizing the laser ignition of natural gas-air mixture and can be used in developing an appropriate laser ignition system for commercial use in SI engines.

  7. Laser induced energy transfer

    International Nuclear Information System (INIS)

    Falcone, R.W.

    1979-01-01

    Two related methods of rapidly transferring stored energy from one excited chemical species to another are described. The first of these, called a laser induced collision, involves a reaction in which the energy balance is met by photons from an intense laser beam. A collision cross section of ca 10 - 17 cm 2 was induced in an experiment which demonstrated the predicted dependence of the cross section on wavelength and power density of the applied laser. A second type of laser induced energy transfer involves the inelastic scattering of laser radiation from energetically excited atoms, and subsequent absorption of the scattered light by a second species. The technique of producing the light, ''anti-Stokes Raman'' scattering of visible and infrared wavelength laser photons, is shown to be an efficient source of narrow bandwidth, high brightness, tunable radiation at vacuum ultraviolet wavelengths by using it to excite a rare gas transition at 583.7 A. In addition, this light source was used to make the first measurement of the isotopic shift of the helium metastable level at 601 A. Applications in laser controlled chemistry and spectroscopy, and proposals for new types of lasers using these two energy transfer methods are discussed

  8. Greenhouse Gas Concentration Data Recovery Algorithm for a Low Cost, Laser Heterodyne Radiometer

    Science.gov (United States)

    Miller, J. Houston; Melroy, Hilary R.; Ott, Lesley E.; Mclinden, Matthew L.; Holben, Brent; Wilson, Emily L.

    2012-01-01

    The goal of a coordinated effort between groups at GWU and NASA GSFC is the development of a low-cost, global, surface instrument network that continuously monitors three key carbon cycle gases in the atmospheric column: carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), as well as oxygen (O2) for atmospheric pressure profiles. The network will implement a low-cost, miniaturized, laser heterodyne radiometer (mini-LHR) that has recently been developed at NASA Goddard Space Flight Center. This mini-LHR is designed to operate in tandem with the passive aerosol sensor currently used in AERONET (a well established network of more than 450 ground aerosol monitoring instruments worldwide), and could be rapidly deployed into this established global network. Laser heterodyne radiometry is a well-established technique for detecting weak signals that was adapted from radio receiver technology. Here, a weak light signal, that has undergone absorption by atmospheric components, is mixed with light from a distributed feedback (DFB) telecommunications laser on a single-mode optical fiber. The RF component of the signal is detected on a fast photoreceiver. Scanning the laser through an absorption feature in the infrared, results in a scanned heterodyne signal io the RF. Deconvolution of this signal through the retrieval algorithm allows for the extraction of altitude contributions to the column signal. The retrieval algorithm is based on a spectral simulation program, SpecSyn, developed at GWU for high-resolution infrared spectroscopies. Variations io pressure, temperature, composition, and refractive index through the atmosphere; that are all functions of latitude, longitude, time of day, altitude, etc.; are modeled using algorithms developed in the MODTRAN program developed in part by the US Air Force Research Laboratory. In these calculations the atmosphere is modeled as a series of spherically symmetric shells with boundaries specified at defined altitudes. Temperature

  9. Hardness, microstructure and surface characterization of laser gas nitrided commercially pure titanium using high power CO{sub 2} laser

    Energy Technology Data Exchange (ETDEWEB)

    Selvan, J.S.; Subramanian, K. [Anna Univ., Chennai (India). Dept. of Physics; Nath, A.K. [Center for Advanced Technology, Madya Pradesh (India); Gogia, A.K. [DMRL, Hyderabad (India); Balamurugan, A.K.; Rajagopal, S. [Indira Gandhi Centre for Atomic Research, Tamil Nadu (India). Materials Science Div.

    1998-10-01

    Surface nitriding of commercially pure (CP) titanium was carried out using high power CO{sub 2} laser at pure nitrogen and dilute nitrogen (N{sub 2} + Ar) environment. The hardness, microstructure, and melt pool configuration of the laser melted titanium in helium and argon atmosphere was compared with laser melting at pure and dilute nitrogen environment. The hardness of the nitrided layer was of the order of 1000 to 1600 HV. The hardness of the laser melted titanium in the argon and helium atmosphere was 500 to 1000 HV. Using x-ray analysis of the formation of TiN and Ti{sub 2}N phase was identified in the laser nitrided titanium. The presence of nitrogen in the nitrided zone was confirmed using secondary ion mass spectroscopy (SIMS) analysis. The microstructures revealed densely populated dendrites in the sample nitrided at 100% N{sub 2} environment and thinly populated dendrites in dilute environment. The crack intensity was large in the nitrided sample at pure nitrogen, and few cracks were observed in the 50% N{sub 2} + 50% Ar environment.

  10. Various types of semiconductor photocatalysts modified by CdTe QDs and Pt NPs for toluene photooxidation in the gas phase under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Marchelek, M. [Department of Environmental Technology, Faculty of Chemistry, University of Gdansk Wita Stwosza 63, 80-952 Gdansk (Poland); Grabowska, E., E-mail: ewelina.grabowska@ug.edu.pl [Department of Environmental Technology, Faculty of Chemistry, University of Gdansk Wita Stwosza 63, 80-952 Gdansk (Poland); Klimczuk, T. [Department of Solid State Physics, Faculty of Applied Physics and Mathematics, Gdansk University of Technology, G. Narutowicza 11/12, 80-233 Gdansk (Poland); Lisowski, W. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44-52, 01-224 Warsaw (Poland); Zaleska-Medynska, A. [Department of Environmental Technology, Faculty of Chemistry, University of Gdansk Wita Stwosza 63, 80-952 Gdansk (Poland)

    2017-01-30

    Highlights: • Novel semiconductors decorated by CdTe QDs and/or Pt NPs were synthesized. • Photodeposition and radiolysis is an effective method to obtaining Pt NPs. • CdTe decorated samples were prepared by absorption of QDs on matrix surface. • KTaO{sub 3}/CdTe-Pt{sub (R)} showed highest photocatalytic performance. • The enhanced performance was associated with electron trap mechanism. - Abstract: A novel synthesis process was used to prepare TiO{sub 2} microspheres, TiO{sub 2} P-25, SrTiO{sub 3} and KTaO{sub 3} decorated by CdTe QDs and/or Pt NPs. The effect of semiconductor matrix, presence of CdTe QDs and/or Pt NPs on the semiconductor surface as well as deposition technique of Pt NPs (photodeposition or radiolysis) on the photocatalytic activity were investigated. The as-prepared samples were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), photoluminescence spectrometry (PL), Fourier transform infrared (FT-IR) and Raman spectra, diffuse reflectance spectroscopy (DRS) and BET surface area analysis. The photocatalytic decomposition of toluene in gas phase, activated by light-emitting diodes (LEDs), with the CdTe/Pt nanoparticles-modified TiO{sub 2} microspheres, P25, SrTiO{sub 3} and KTaO{sub 3} semiconductors was investigated under UV–vis and visible irradiation.The results showed that the photoactivity depends on semiconductor matrix. The highest photoactivity under Vis light was observed for KTaO{sub 3}/CdTe-Pt{sub (R)} sample (56% of toluene was decompose after 30 min of irradiation). The efficiency of the most active sample was 3 times higher than result for P25 and two times higher than for unmodified KTaO{sub 3}.

  11. Cu-Ni nanowire-based TiO{sub 2} hybrid for the dynamic photodegradation of acetaldehyde gas pollutant under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Shuying [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049 (China); Xie, Xiaofeng, E-mail: xxfshcn@163.com [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Chen, Sheng-Chieh [College of Science and Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Tong, Shengrui [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Lu, Guanhong [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Pui, David Y.H. [College of Science and Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Sun, Jing [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2017-06-30

    Graphical abstract: One-dimensional Cu-Ni bimetallic nanowires were introduced into TiO{sub 2}-based matrix to enhance their photocatalysis efficiency and expand their light absorption range. - Highlights: • Cu-Ni nanowire-based TiO{sub 2} hybrid photocatalyst. • One-dimensional electron pathways and surface plasmon resonance effects. • Dynamic photodegradation of acetaldehyde gas pollutant. - Abstract: One-dimensional bimetallic nanowires were introduced into TiO{sub 2}-based matrix to enhance their photocatalysis efficiency and expand their light absorption range in this work. Recently, metal nanowires have attracted many attention in photocatalyst research fields because of their favorable electronic transmission properties and especially in the aspect of surface plasmon resonance effects. Moreover, Cu-Ni bimetallic nanowires (Cu-Ni NWs) have shown better chemical stability than ordinary monometallic nanowires in our recent works. Interestingly, it has been found that Ni sleeves of the bimetallic nanowires also can modify the Schottky barrier of interface between TiO{sub 2} and metallic conductor, so that be beneficial to the separation of photogenerated carriers in the Cu-Ni/TiO{sub 2} network topology. Hence, a novel heterostructured photocatalyst composed of Cu-Ni NWs and TiO{sub 2} nanoparticles (NPs) was fabricated by one-step hydrolysis approach to explore its photocatalytic performance. TEM and EDX mapping images of this TiO{sub 2} NPs @Cu-Ni NWs (TCN) hybrid displayed that Cu-Ni NWs were wrapped by compact TiO{sub 2} layer and retained the one-dimensional structure in matrix. In experiments, the photocatalytic performance of the TCN nanocomposite was significantly enhanced comparing to pure TiO{sub 2}. Acetaldehyde, as a common gas pollutant in the environment, was employed to evaluate the photodegradation efficiency of a series of TCN nanocomposites under continuous feeding. The TCN exhibited excellent potodegradation performance, where the

  12. An investigation of the role of Ne, Ar, and Kr as buffer gas in a coaxial e-beam pumped KrF laser

    NARCIS (Netherlands)

    Kleikamp, B.M.H.H.; Peters, P.J.M.; Witteman, W.J.

    1986-01-01

    The role of Ne, Ar, and Kr as a buffer gas was investigated in a KrF laser pumped by a coaxiale-beam. The coaxial diode has a length of 20 cm and the anode tube diameter is 1 cm. The tube can be pressurized with the laser gas mixture up to 12 bar while a current density of 250 A/cm2can be achieved.

  13. A compact, quasi-monochromatic laser-plasma EUV source based on a double-stream gas-puff target at 13.8 nm wavelength

    Czech Academy of Sciences Publication Activity Database

    Wachulak, P.W.; Bartnik, A.; Fiedorowicz, H.; Feigl, T.; Jarocki, R.; Kostecki, J.; Rudawski, P.; Sawicka, Magdalena; Szczurek, M.; Szczurek, A.; Zawadzki, Z.

    2010-01-01

    Roč. 100, č. 3 (2010), 461-469 ISSN 0946-2171 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser-plasma * EUV source * gas puff target * elliptical multi- layer * mirror * table-top setup Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.239, year: 2010

  14. Laser gas assisted texturing and formation of nitride and oxynitride compounds on alumina surface: Surface response to environmental dust

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Al-Sharafi, A.; Al-Aqeeli, N.

    2018-03-01

    Laser gas assisted texturing of alumina surface is carried out, and formation of nitride and oxynitride compounds in the surface vicinity is examined. The laser parameters are selected to create the surface topology consisting of micro/nano pillars with minimum defect sites including micro-cracks, voids and large size cavities. Morphological and hydrophobic characteristics of the textured surface are examined using the analytical tools. The characteristics of the environmental dust and its influence on the laser textured surface are studied while mimicking the local humid air ambient. Adhesion of the dry mud on the laser textured surface is assessed through the measurement of the tangential force, which is required to remove the dry mud from the surface. It is found that laser texturing gives rise to micro/nano pillars topology and the formation of AlN and AlON compounds in the surface vicinity. This, in turn, lowers the free energy of the textured surface and enhances the hydrophobicity of the surface. The liquid solution resulted from the dissolution of alkaline and alkaline earth metals of the dust particles in water condensate forms locally scattered liquid islands at the interface of mud and textured surface. The dried liquid solution at the interface increases the dry mud adhesion on the textured surface. Some dry mud residues remain on the textured surface after the dry mud is removed by a pressurized desalinated water jet.

  15. A hydroxyl radical detection system using gas expansion and fast gating laser-induced fluorescence techniques.

    Science.gov (United States)

    Chen, Hao; Hu, Renzhi; Xie, Pinhua; Xing, Xingbiao; Ling, Liuyi; Li, Zhiyan; Wang, Fengyang; Wang, Yihui; Liu, Jianguo; Liu, Wenqing

    2018-03-01

    An OH radical measurement instrument based on Fluorescence Assay by Gas Expansion (FAGE) has been developed in our laboratory. Ambient air is introduced into a low-pressure fluorescence cell through a pinhole aperture and irradiated by a dye laser at a high repetition rate of 8.5kHz. The OH radical is both excited and detected at 308nm using A-X(0,0) band. To satisfy the high efficiency needs of fluorescence collection and detection, a 4-lens optical system and a self-designed gated photomultiplier (PMT) is used, and gating is actualized by switching the voltage applied on the PMT dynodes. A micro channel photomultiplier (MCP) is also prepared for fluorescence detection. Then the weak signal is accumulated by a photon counter in a specific timing. The OH radical excitation spectrum range in the wavelength of 307.82-308.2nm is detected and the excited line for OH detection is determined to be Q 1 (2) line. The calibration of the FAGE system is researched by using simultaneous photolysis of H 2 O and O 2 . The minimum detection limit of the instrument using gated PMT is determined to be 9.4×10 5 molecules/cm 3 , and the sensitivity is 9.5×10 -7 cps/(OH·cm -3 ), with a signal-to-noise ratio of 2 and an integration time of 60sec, while OH detection limit and the detection sensitivity using MCP is calculated to be 1.6×10 5 molecules/cm 3 and 2.3×10 -6 cps/(OH·cm -3 ). The laboratory OH radical measurement is carried out and results show that the proposed system can be used for atmospheric OH radical measurement. Copyright © 2017. Published by Elsevier B.V.

  16. Effect of molecular weight and density of ambient gas on shock wave in laser-induced surface nanostructuring

    International Nuclear Information System (INIS)

    Guo Liying; Wang Xinwei

    2009-01-01

    This paper presents the results of molecular dynamics studies about the shock wave during laser-induced surface nanostructuring. A quasi-three dimensional model is constructed to study systems consisting of over 2 million atoms. Detailed studies are carried out about the shock wave front and Mach number, evolution of plume and ambient gas interaction zone, and energy exchange between the ambient gas and plume. Under an ambience of lower pressure or lighter molecular mass, the plume affects a larger area while the strength of the shock wave front is weaker. With the same ambient pressure, the ablated material features the same kinetic energy at the late stage regardless of the molecular weight of the ambient gas. The same conclusion holds for the energy increase of the ambient gas as well. When the ambient pressure is reduced, more kinetic energy is carried out by the ablated material while less energy is transferred to the ambient gas. It is observed that heavier ambient gas could bounce back the ablated material to the target surface.

  17. Low Power Consumption Lasers for Miniature Optical Spectrometers for Trace Gas Analysis

    Science.gov (United States)

    Forouhar, S.; Frez, C.; Franz, K. J.; Ksendzov, A.; Qiu, Y.; Soibel, K. A.; Chen, J.; Hosoda, T.; Kipshidze, G.; Shterengas, L.; hide

    2011-01-01

    The air quality of any manned spacecraft needs to be continuously monitored in order to safeguard the health of the crew. Air quality monitoring grows in importance as mission duration increases. Due to the small size, low power draw, and performance reliability, semiconductor laser-based instruments are viable candidates for this purpose. Achieving a minimum instrument size requires lasers with emission wavelength coinciding with the absorption of the fundamental absorption lines of the target gases, which are mostly in the 3.0-5.0 micron wavelength range. In this paper we report on our progress developing high wall plug efficiency type-I quantum-well GaSb-based diode lasers operating at room temperatures in the spectral region near 3.0-3.5 micron and quantum cascade (QC) lasers in the 4.0-5.0 micron range. These lasers will enable the development of miniature, low-power laser spectrometers for environmental monitoring of the spacecraft.

  18. Lasers

    OpenAIRE

    Passeron, Thierry

    2012-01-01

    International audience; Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be succesfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-aulait macules should not b...

  19. Laser

    OpenAIRE

    Du, K.; Loosen, P.; Herziger, G.

    1991-01-01

    Laser, consisting of a beam path multiple-folded by means of two cavity end mirrors and having at least one reflector folding the laser beam retroreflectively, the axis of which is arranged offset in parallel to the axis of a further reflector. So that the laser exhibits an improved beam quality while retaining its comparatively low adjustment sensitivity, the beam path is folded at least twice by means of the retoreflective reflector.

  20. [Characteristics of laser light].

    Science.gov (United States)

    Takac, S; Stojanović, S

    1999-01-01

    Laser is one of the greatest technical discoveries of the 20th century. It is important in basic sciences, but particularly in diagnosis and therapy of various pathologic conditions of human organism. It is electromagnetic radiation, not X-irradiation and, as such, it is not expected to produce new generation of iatrogenic malignancies. Laser falls between infrared and ultraviolet on the spectrum mainly in the visible light spectrum. Properties of laser light are: monochromacity (the same color), coherence (all of the light waves are in phase both spatially and temporally), collimation (all rays are parallel to each other and do not diverge significantly even over long distances). Lasers were first conceived by Einstein in 1917 when he wrote his "Zur Quantum Theorie der Strahlung" (the quantum theory of radiation) which enumerated concepts of stimulated and spontaneous emission and absorption. Drs. Arthur Schawlow and Charles Townes, in 1956, extended lasers into the optical frequency range and Maiman, in 1960, operated the first laser using ruby as the active medium (ruby laser). Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. To understand the acronym, it is necessary to understand the basic physics of the atom. However, if the atom that is in the excited state is struck by another photon of energy before it returns to the ground state, two photons of equal frequency and energy, travelling in the same direction and in perfect spatial and temporal harmony, are produced. This phenomenon is termed stimulated emission of radiation. An external power source hyperexcites the atoms in the laser medium so that the number of atoms possessing upper energy levels exceeds the number of atoms in a power energy level, a condition termed a population inversion. This "pumping system" which imparts additional energy to the atoms may be optical, mechanical, or chemical. These atoms in a hyperexcited state spontaneously emit photons of light. The

  1. Visibility Matters

    DEFF Research Database (Denmark)

    Wildgaard, Lorna Elizabeth

    2015-01-01

    Research production, which earns universities money, is accredited publications in peer-reviewed journals and books. Increasing research productivity is one policy amongst many used by management to boost growth and income. It is time for a pat on the back, the growth of knowledge and visibility...... at RSLIS ranks us among the top 10 contributors to core LIS journals in a new international ranking. The management should be pleased....

  2. Tunable lasers for waste management photochemistry applications

    International Nuclear Information System (INIS)

    Finch, F.T.

    1978-09-01

    A review of lasers with potential photochemical applications in waste management indicates that dye lasers, as a class, can provide tunable laser output through the visible and near-uv regions of the spectrum of most interest to photochemistry. Many variables can affect the performance of a specific dye laser, and the interactions of these variables, at the current state of the art, are complex. The recent literature on dye-laser characteristics has been reviewed and summarized, with emphasis on those parameters that most likely will affect the scaling of dye lasers in photochemical applications. Current costs are reviewed and correlated with output power. A new class of efficient uv lasers that appear to be scalable in both energy output and pulse rate, based on rare-gas halide excimers and similar molecules, is certain to find major applications in photochemistry. Because the most important developments are too recent to be adequately described in the literature or are the likely outcome of current experiments, the basic physics underlying the class of excimer lasers is described. Specific cost data are unavailable, but these new gas lasers should reflect costs similar to those of existing gas lasers, in particular, the pulsed CO 2 lasers. To complete the survey of tunable-laser characteristics, the technical characteristics of the various classes of lasers in the ir are summarized. Important developments in ir laser technology are being accelerated by isotope-separation research, but, initially at least, this portion of the spectrum is least likely to receive emphasis in waste-management-oriented photochemistry

  3. Mapping the Ionization State of Laser-Irradiated Ar Gas Jets With Multi-Wavelength Monochromatic X-Ray Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kugland, N L; Doppner, T; Kemp, A; Schaeffer, D; Glenzer, S H; Niemann, C

    2010-04-08

    Two-dimensional monochromatic images of fast-electron stimulated Ar K{alpha} and He-{alpha} x-ray self-emission have recorded a time-integrated map of the extent of Ar{sup {approx}6+} and Ar{sup 16+} ions, respectively, within a high density (10{sup 20} cm{sup -3} atomic density) Ar plasma. This plasma was produced by irradiating a 2 mm wide clustering Ar gas jet with an ultra-high intensity (10{sup 19} W/cm{sup 2}, 200 fs) Ti:Sapphire laser operating at 800 nm. Spherically bent quartz crystals in the 200 (for K{alpha}) and 201 (for He-{alpha}) planes were used as near-normal incidence reflective x-ray optics. We see that a large (830 {micro}m long) region of plasma emits K{alpha} primarily along the laser axis, while the He-{alpha} emission is confined to smaller hot spot (230 {micro}m long) region that likely corresponds to the focal volume of the f/8 laser beam. X-ray spectra from a Bragg spectrometer operating in the von Hamos geometry, which images in one dimension, indicate that the centroids of the K{alpha} and He-{alpha} emission regions are separated by approximately 330 {micro}m along the laser axis.

  4. Mapping the ionization state of laser-irradiated Ar gas jets with multiwavelength monochromatic x-ray imaging.

    Science.gov (United States)

    Kugland, N L; Döppner, T; Kemp, A; Schaeffer, D; Glenzer, S H; Niemann, C

    2010-10-01

    Two-dimensional monochromatic images of fast-electron stimulated Ar Kα and He-α x-ray self-emission have recorded a time-integrated map of the extent of Ar(≈6+) and Ar(16+) ions, respectively, within a high density (10(20) cm(-3) atomic density) Ar plasma. This plasma was produced by irradiating a 2 mm wide clustering Ar gas jet with an ultrahigh intensity (10(19) W/cm(2), 50 TW) Ti:sapphire laser operating at 800 nm. Spherically bent quartz crystals in the 200 (for Kα) and 201 (for He-α) planes were used as near-normal incidence reflective x-ray optics. We see that a large (830 μm long) region of plasma emits Kα primarily along the laser axis, while the He-α emission is confined to smaller hot spot (230 μm long) region that likely corresponds to the focal volume of the f/8 laser beam. X-ray spectra from a Bragg spectrometer operating in the von Hamos geometry indicate that the centroids of the Kα and He-α emission regions are separated by approximately 330 μm along the laser axis.

  5. Dramatic enhancement of XUV laser output using a multi-mode, gas-filled capillary waveguide

    Czech Academy of Sciences Publication Activity Database

    Mocek, Tomáš; McKenna, C.M.; Cros, B.; Sebban, S.; Spence, D.J.; Maynard, G.; Bettaibi, I.; Vorontsov, V.; Gonsavles, A.J.; Hooker, S.M.

    2005-01-01

    Roč. 71, 01 (2005), 013804/1-013804/5 ISSN 1050-2947 Grant - others:EU(XE) HPRI-1999-CT-00086; EU(XE) HPMF-CT-2002-01554 Institutional research plan: CEZ:AV0Z10100523 Keywords : waveguiding * x-ray laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.997, year: 2005

  6. Computational and experimental progress on laser-activated gas avalanche switches for broadband, high-power electromagnetic pulse generation

    International Nuclear Information System (INIS)

    Mayhall, D.J.; Yee, J.H.; Villa, F.

    1991-01-01

    This paper discusses the gas avalanche switch, a high-voltage, picosecond-speed switch, which has been proposed. The basic switch consists of pulse-charged electrodes, immersed in a high-pressure gas. An avalanche discharge is induced in the gas between the electrodes by ionization from a picosecond-scale laser pulse. The avalanching electrons move toward the anode, causing the applied voltage to collapse in picoseconds. This voltage collapse, if rapid enough, generates electromagnetic waves. A two-dimensional (2D), finite difference computer code solves Maxwell's equations for transverse magnetic modes for rectilinear electrodes between parallel plate conductors, along with electron conservation equations for continuity, momentum, and energy. Collision frequencies for ionization and momentum and energy transfer to neutral molecules are assumed to scale linearly with neutral pressure. Electrode charging and laser-driven electron deposition are assumed to be instantaneous. Code calculations are done for a pulse generator geometry, consisting of an 0.7 mm wide by 0.8 mm high, beveled, rectangular center electrode between grounded parallel plates at 2 mm spacing in air

  7. Numerical study of threshold intensity dependence on gas pressure in the breakdown of molecular hydrogen induced by excimer laser

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Nassef, O. Aied

    2017-10-01

    In the present work, a numerical analysis is performed to investigate the threshold intensity dependence on gas pressure in laser spark ignition of the H2 plasma. The analysis considered the experimental measurements that were carried out by Yagi and Huo [Appl. Opt. 35, 3183 (1996)]. In their experiment, H2 in a pressure range of 150-3000 Torr is irradiated by a focused excimer laser source using a 96 cm lens at a wavelength of 248 nm and a pulse duration of 20 ns. The study, based on a modified electron cascade model [K. A. Hamam et al., J. Mod. Phys. 4, 311 (2013)], solves numerically a time-dependent energy equation for the distribution of the electron energy as well as a set of rate equations that describe the change in the formed excited molecule population. This model enabled the determination of the threshold intensity as a function of gas pressure. The validity of the model was tested by comparing the calculated thresholds with the experimentally measured ones. Moreover, the calculation of the electron energy distribution function and its parameters justified the role of the electron gain and loss processes in controlling the value of threshold intensity in relation to the gas pressure. The effect of loss processes on the threshold intensity is also presented.

  8. Bringing a needle to a laser fight: comparing greenhouse gas sampling methods with gas chromatography and fourier transform infrared spectroscopy

    Science.gov (United States)

    As scientists, producers, policymakers, and the general public become more concerned about impacts of climate change, there is an increasing need to understand and quantify greenhouse gas emissions from agricultural practices, which often feed into global, multi-institution databases. Current best p...

  9. Ozone Gas Bath Combined with Endovenous Laser Therapy for Lower Limb Venous Ulcers: A Randomized Clinical Trial.

    Science.gov (United States)

    Zhou, Yi-Ting; Zhao, Xu-Dong; Jiang, Jian-Wei; Li, Xin-Sheng; Wu, Zhen-Hai

    2016-10-01

    Endovenous laser therapy (EVLT) is safe and effective for lower limb venous ulcers. However, severe necrosis and infection in the ulcer area are contraindications of puncture and EVLT. Local bath with ozone gas has been shown to improve the condition of ulcer areas. The aim of this study was to evaluate the clinical efficacy of ozone gas bath combined with EVLT in comparison with EVLT alone for the treatment for lower limb venous ulcers. Ninety-two patients with venous ulcers were randomized to receive ozone gas bath combined with EVLT (OEVLT group) or EVLT alone (EVLT group). In the OEVLT group, the venous ulcers were preconditioned with ozone gas bath prior to EVLT. The minimum follow-up time was 12 months. The two groups were compared in terms of complete occlusion of the treated veins, ulcer healing ratio, ratio of ulcer recurrence, patient satisfaction, complications, and side effects. There was no significant difference in venous occlusion between the two groups. The ratio of ulcer healing in the OEVLT group was significantly higher than the EVLT group at 12 months follow-up. Patients in the OEVLT group showed better satisfaction and a lower recurrence ratio than the OEVLT group. No severe complications or side effects occurred in either groups. Ozone gas bath combined with EVLT showed improved efficacy for the treatment of lower limb venous ulcers and lower recurrence ratio comparison with EVLT alone. This procedure is a safe and technically feasible.

  10. Comparison of eye-safe solid state laser DIAL with passive gas filter correlation measurements from aircraft and spacecraft

    Science.gov (United States)

    Hess, Robert V.; Staton, Leo D.; Wallio, H. Andrew; Wang, Liang-Guo

    1992-01-01

    Differential Absorption Lidar (DIAL) using solid state Ti:sapphire lasers finds current application in the NASA/LASE Project for H2O vapor measurements in the approximately = 0.820 micron region for the lower and mid-troposphere and in potential future applications in planned measurements of the approximately = 0.940 micron region where both strong and weak absorption lines enables measurements throughout the troposphere and lower stratosphere. The challenge exists to perform measurements in the eye-safe greater than 1.5 micron region. A comparison between DIAL and passive Gas Filter Correlation Radiometer (GFCR) measurements is made. The essence of the differences in signal to noise ratio for DIAL and passive GFCR measurements is examined. The state of the art of lasers and optical parametric oscillators (OPO's) is discussed.

  11. Green lasers

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin

    2010-01-01

    Well over a dozen papers at this year's Photonics West meeting in San Francisco boasted improvements in harmonic generation to produce visible laser beams, most of them in the green spectral range......Well over a dozen papers at this year's Photonics West meeting in San Francisco boasted improvements in harmonic generation to produce visible laser beams, most of them in the green spectral range...

  12. Metallurgical characterization of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

    International Nuclear Information System (INIS)

    Padmanaban, G.; Balasubramanian, V.

    2011-01-01

    This paper reports the influences of welding processes such as friction stir welding (FSW), laser beam welding (LBW) and pulsed current gas tungsten arc welding (PCGTAW) on mechanical and metallurgical properties of AZ31B magnesium alloy. Optical microscopy, scanning electron microscopy, transmission electron microscopy and X-Ray diffraction technique were used to evaluate the metallurgical characteristics of welded joints. LBW joints exhibited superior tensile properties compared to FSW and PCGTAW joints due to the formation of finer grains in weld region, higher fusion zone hardness, the absence of heat affected zone, presence of uniformly distributed finer precipitates in weld region.

  13. Pulsed power systems for the LASL High Energy Gas Laser Facility

    International Nuclear Information System (INIS)

    Riepe, K.; Jansen, H.

    1976-01-01

    The laser division at Los Alamos Scientific Laboratory is designing a CO 2 laser fusion experiment with the goal of delivering 100 kJ to the target in a one nanosecond pulse. The laser will be pumped by an electron beam-controlled discharge. The pumping power supply will be a number of parallel Marx generators, with an output voltage of 500 kV, and a total energy storage of about 5 MJ. The electron gun is a ''cold cathode'' triode, also operating at about 500 kV. Preliminary design considerations for the pulsed power systems are presented. Some pulse forming network designs are discussed with calculated waveforms shown

  14. Numerical and experimental investigation of laser induced plasma spectrum of aluminum in the presence of a noble gas

    International Nuclear Information System (INIS)

    Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2012-01-01

    Laser-induced plasma emission of an aluminum target in helium gas at 1 atm pressure is numerically and experimentally investigated. A laser pulse at wavelength of 266 nm and pulse duration of 10 ns has been considered. Laser ablation is calculated by a one dimensional model based on thermal evaporation mechanism. Spatial and temporal parameters of plasma expansion are determined by using hydrodynamic equations. Three kinds of plasma emission, including Bremsstrahlung, recombination and spectral emissions are considered for modeling the spectrum. Strong lines of aluminum and helium in wavelength interval of 200 to 450 nm are selected. Aluminum spectrum in UV range is depicted and compared with other spectral ranges. Temporal and spatial evolution of plasma emission up to 200 ns after the laser irradiation is studied. The effect of laser energy on the plasma spectrum is studied. An experimental set-up is arranged to compare numerical calculations with experimental results. Experimental and numerical results illustrate that helium line widths and peak intensities become narrower and weaker with time, respectively. Spatial distribution of spectrum shows that for closer distance to the sample surface, an intense continuous emission is observed, while at the farther distance, continuous emission decreases and spectral lines become sharper. A good coincidence is observed between experimental and numerical results. - Highlights: ► Aluminum plasma emission in helium is numerically and experimentally studied. ► Spectral, Bremsstrahlung and recombination emissions in spectrum are calculated. ► All strong lines of aluminum and helium are chosen for spectrum simulation. ► Line widths and peak intensities at later times become narrower and weaker. ► At specific optimum position, the maximum of signal peaks is acquired.

  15. Investigation of the threshold intensity versus gas pressure in the breakdown of helium by 248 nm laser radiation

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Abdellatif, Galila

    2014-10-01

    An investigation of the unexpectedly strong dependence of the threshold intensity on the gas pressure in the experimental study on the breakdown of He by short laser wavelength (Turcu et al., in Opt Commun, 134:66-68, 1997) is presented. A modified electron cascade model is applied (Evans and Gamal, in J Phys D Appl Phys, 13:1447-1458, 1980). Computations revealed reasonable agreement between the calculated thresholds and the measured ones. Moreover, the calculated electron energy distribution function and its parameters proved that multiphoton ionization of ground and excited atoms is the main source for the seed electrons, which contributes to the breakdown of helium. The effect of diffusion losses over pressures <1,000 Torr elucidated the origin of the strong dependence of the threshold intensity on the gas pressure. Collisional ionization dominates only at high pressures. No evidence for recombination losses is observed for pressures up to 3,000 Torr.

  16. Examination of potassium diode pumped alkali laser using He, Ar, CH4and C2H6as buffer gas.

    Science.gov (United States)

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

    2017-11-27

    We examined the performance of a potassium diode pumped alkali laser (K DPAL) using He, Ar, CH 4 , C 2 H 6 and a mixture of He and CH 4 as a buffer gas to provide spin-orbit mixing of the 4P 3/2 and 4P 1/2 states of Potassium atoms. We found that pure helium cannot be used as an efficient buffer gas for continuous wave lasing without using a flowing system with a considerable flow speed of about 100 m/s. In contrast, using a small amount of methane (10-20 Torr) mixed with helium, continuous wave lasing can be achieved using very moderate flow speeds of about 1 m/s.

  17. Thermal Boundary Layer Effects on Line-of-Sight Tunable Diode Laser Absorption Spectroscopy (TDLAS) Gas Concentration Measurements.

    Science.gov (United States)

    Qu, Zhechao; Werhahn, Olav; Ebert, Volker

    2018-01-01

    The effects of thermal boundary layers on tunable diode laser absorption spectroscopy (TDLAS) measurement results must be quantified when using the line-of-sight (LOS) TDLAS under conditions with spatial temperature gradient. In this paper, a new methodology based on spectral simulation is presented quantifying the LOS TDLAS measurement deviation under conditions with thermal boundary layers. The effects of different temperature gradients and thermal boundary layer thickness on spectral collisional widths and gas concentration measurements are quantified. A CO 2 TDLAS spectrometer, which has two gas cells to generate the spatial temperature gradients, was employed to validate the simulation results. The measured deviations and LOS averaged collisional widths are in very good agreement with the simulated results for conditions with different temperature gradients. We demonstrate quantification of thermal boundary layers' thickness with proposed method by exploitation of the LOS averaged the collisional width of the path-integrated spectrum.

  18. Coherent soft X-ray high-order harmonics using tight-focusing laser pulses in the gas mixture.

    Science.gov (United States)

    Lu, Faming; Xia, Yuanqin; Zhang, Sheng; Chen, Deying; Zhao, Yang; Liu, Bin

    2014-01-01

    We experimentally study the harmonics from a Xe-He gas mixture using tight-focusing femtosecond laser pulses. The spectrum in the mixed gases exhibits an extended cutoff region from the harmonic H21 to H27. The potential explanation is that the harmonics photons from Xe contribute the electrons of He atoms to transmit into the excited-state. Therefore, the harmonics are emitted from He atoms easily. Furthermore, we show that there are the suppressed harmonics H15 and H17 in the mixed gases. The underlying mechanism is the destructive interference between harmonics generated from different atoms. Our results indicate that HHG from Xe-He gas mixture is an efficient method of obtaining the coherent soft X-ray source.

  19. Visibility graphs and landscape visibility analysis

    OpenAIRE

    O Sullivan, D.; Turner, A.

    2001-01-01

    Visibility analysis based on viewsheds is one of the most frequently used GIS analysis tools. In this paper we present an approach to visibility analysis based on the visibility graph. A visibility graph records the pattern of mutual visibility relations in a landscape, and provides a convenient way of storing and further analysing the results of multiple viewshed analyses for a particular landscape region. We describe how a visibility graph may be calculated for a landscape. We then give exa...

  20. Hydrolysis of a mixture of saccharides by cellulase from Aspergillus niger and its application for visible-light-induced hydrogen gas production system using Mg chlorophyll-a and platinum nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Amao, Yutaka; Hirakawa, Takamasa [Department of Applied Chemistry, Oita University, Dannoharu 700, Oita 870-1192 (Japan)

    2010-07-15

    Cellulase obtained from Aspergillus niger was used to hydrolyze a mixture of saccharides containing sucrose, maltose, and cellobiose; the reduced form of nicotinamide-adenine dinucleotide (NAD{sup +}), which is NADH, was produced during hydrolysis of the mixture of saccharides in the presence of NAD{sup +} and glucose dehydrogenase (GDH). We have developed a visible-light-induced enzymatic biohydrogen production system involving the combination of cellulase-mediated hydrolysis of the mixture of saccharides and hydrogen production by platinum nanoparticles using photosensitization of Mg chlorophyll-a (Mg Chl-a). Continuous production of hydrogen gas was observed when the reaction mixture containing saccharides, cellulase, GDH, NAD{sup +}, Mg Chl-a, methylviologen (MV{sup 2+}, an electron donor), and platinum nanoparticles was irradiated by visible light. After 120 min of irradiation, the amount of hydrogen produced from the mixture of saccharides was approximately 2.8 {mu}mol. (author)

  1. CW-Laser-Induced Solid-State Reactions in Mixed Micron-Sized Particles of Silicon Monoxide and Titanium Monoxide: Nano-Structured Composite with Visible Light Absorption

    Czech Academy of Sciences Publication Activity Database

    Křenek, T.; Tesař, J.; Kupčík, Jaroslav; Netrvalová, M.; Pola, M.; Jandová, Věra; Pokorná, Dana; Cuřínová, Petra; Bezdička, Petr; Pola, Josef

    2017-01-01

    Roč. 27, č. 6 (2017), s. 1640-1648 ISSN 1574-1443 Institutional support: RVO:61388980 ; RVO:67985858 Keywords : Cw CO2 laser heating * IR laser imaging * Silicon monoxide * Solid state redox reactions * Ti/Si/O composite * Titanium monoxide Subject RIV: CA - Inorganic Chemistry; CI - Industrial Chemistry, Chemical Engineering (UCHP-M) OBOR OECD: Inorganic and nuclear chemistry; Chemical process engineering (UCHP-M) Impact factor: 1.577, year: 2016

  2. Rare gas halide lasers for fusion. Final technical report, 1 March 1979-29 February 1980

    Energy Technology Data Exchange (ETDEWEB)

    Duzy, C; Hsia, J; Hyman, H; Jacob, J; Klimek, D; Parks, J; Trainor, D

    1980-04-01

    In an effort to reliably extend the understanding of KrF* lasers, we collected specific, detailed experimental data and carried out theoretical calculations to explore and document those issues we identified as likely to be important in the short pulse operating regime. These included the effects of: (1) fuel burnup, (2) electron quenching, (3) gain/absorption at high current densities, (4) photoionization, (5) accessibility of the lying levels of KrF by laser flux, (6) temperature on fluorescence efficiency.

  3. Lasers.

    Science.gov (United States)

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  4. [Lasers].

    Science.gov (United States)

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  5. Low Power Consumption Laser for Next Generation Miniature Optical Spectrometers for Trace Gas Analysis

    Science.gov (United States)

    Forouhar, S.; Frez, C.; Franz, K. J.; Ksendzov, A.; Qiu, Y.; Soibel, K. A.; Chen, J.; Hosoda, T.; Kipshidze, G.; Shterengas, L.; hide

    2011-01-01

    The air quality of any manned spacecraft needs to be continuously monitored in order to safeguard the health of the crew. Air quality monitoring grows in importance as mission duration increases. Due to the small size, low power draw, and performance reliability, semiconductor laser-based instruments are viable candidates for this purpose. Achieving a minimum instrument size requires lasers with emission wavelength coinciding with the absorption of the fundamental absorption lines of the target gases, which are mostly in the 3.0-5.0 mu m wavelength range. In this paper we report on our progress developing high wall plug efficiency type-I quantum-well GaSb-based diode lasers operating at room temperatures in the spectral region near 3.0-3.5 mu m and quantum cascade (QC) lasers in the 4.0-5.0 mu m range. These lasers will enable the development of miniature, low-power laser spectrometers for environmental monitoring of the spacecraft

  6. Frequency-stabilised laser reference system for trace-gas sensing applications from space

    Science.gov (United States)

    Matthey, Renaud; Affolderbach, Christoph; Mileti, Gaetano; Schilt, Stéphane; Werner, Daniela; Chin, Sanghoon; Abrardi, Laura; Thévenaz, Luc

    2017-11-01

    A four-wavelength low-power continuous-wave frequency laser reference system has been realised in the 935.4-nm range for water vapour differential absorption lidar (DIAL) applications. The system is built around laboratory extended-cavity and DFB diode lasers. Three lasers are directly locked to three water vapour absorption lines of different strength, whereas the wavelength of the fourth laser lies out of any absorption line (offline). On-line stabilisation is performed by wavelength modulation spectroscopy technique, while precise offline stabilisation is realised by an offset locking at 18.8 GHz. Offset frequency larger than 320 GHz has also been demonstrated at 1.55 μm, based on an all-fibre optical frequency comb. First steps towards the use of a photonic crystal fibre as ultra compact reference cell with long optical pathlength were realised. The developed techniques for direct and offset-lock laser stabilisation can also be applied to other gases and wavelengths, provided the required optical components are available for the laser wavelength considered.

  7. Comparative study of the influence of the gas injection system on the Nd:yttrium-aluminum-garnet laser cutting of advanced oxide ceramics

    International Nuclear Information System (INIS)

    Quintero, F.; Pou, J.; Lusquinos, F.; Boutinguiza, M.; Soto, R.; Perez-Amor, M.

    2003-01-01

    Cutting of advanced oxide ceramics is still a difficult task. In this work, the possibility to effectively cut them using a Nd:YAG laser guided by an optical fiber is demonstrated. The key points are the aerodynamic interactions of the assist gas jet in the fusion laser cutting of ceramics. A comprehensive study of the influence of these aerodynamic interactions on the laser cutting of advanced oxide ceramics has been carried out. The characteristics of the heat affected zone (HAZ) were studied related to the efficiency of the assist gas to eject the molten material. It has been demonstrated that the HAZ can be avoided with a suitable design of the gas injection system combined with an appropriate selection of the values of the processing parameters. With the aim of improving the efficiency of the assist gas injection system, a new cutting head with an off-axis supersonic nozzle was developed. Furthermore, a comparison between the utilization of a conventional coaxial conical nozzle to inject the assist gas and the new system is presented. The results obtained give clear proof that the use of the new gas injection system leads to a great improvement on the cut quality by means of a more efficient removing of the molten material out of the cutting front. This result is of special interest in the laser fusion cutting of thick ceramic plates at high processing rates

  8. Narrow Energy-Spread Proton Beams Generated in a Gas Jet by High-Power CO2 Laser Pulses

    Science.gov (United States)

    Haberberger, D.; Tochitsky, S.; Gong, C.; Mori, W.; Joshi, C.; Fiuza, F.; Fonseca, R.; Silva, L.

    2011-11-01

    At the UCLA Neptune Laboratory, we have investigated laser driven ion acceleration using a high-power CO2 laser pulse in a H2 gas jet tuned around the critical plasma density of 10^19cm-3 for 10μm light. The CO2 laser pulses consist of a train of 3ps pulses separated by 18ps with a peak power of up to 4TW and total energy of 50J [1]. Protons have been accelerated from this interaction to energies up to 22MeV, which far exceeds that predicted by ponderomotive force scaling for our vacuum ao˜2. Furthermore, these high energy protons are contained within an energy spread of δE/EFWHM ˜ 1%, and have an estimated transverse emittance of down to ˜1mm.mrad. The evolution of the plasma density profile was probed with 532nm interferometry revealing a steep rise (< 10 λ) to overcritical densities followed by long exponential fall on the back side of the plasma. 2D OSIRIS simulations run with the experimentally measured plasma density profile have uncovered a multistage process for the production of monoenergetic protons based on the shock acceleration mechanism which will be discussed.[4pt][1] D. Haberberger et. al., Opt. Exp. 18, 17865 (2010)

  9. A Study on the Effects of the Use of Gas or Water Atomized AISI 316L Steel Powder on the Corrosion Resistance of Laser Deposited Material

    Science.gov (United States)

    Tobar, M. J.; Amado, J. M.; Montero, J.; Yáñez, A.

    Water atomized and gas atomized powders are commonly used in 3D laser manufacturing. Both types of AISI 316L stainless steel powders are available which differ in their manganese content. This is due to specific procedures related to the two different atomization process. The amount of manganese in the laser processed part might have important implications in its corrosion resistance. It could lead to the formation of manganese sulfides (MnS) which are known to be initiation sites for pitting corrosion. In this work, corrosion performance of laser deposited 316L steel using gas and atomized powders is compared by means of potentiodynamic polarization tests in 0.35%wt. NaCL solution. Worse performance of the gas atomized samples is observed as with respect to the water atomized ones in terms of polarization resistance, corrosion rate and pitting susceptibility.

  10. Analysis of the absorption spectra of gas emission of patients with lung cancer and chronic obstructive pulmonary disease by laser optoacoustic spectroscopy

    Science.gov (United States)

    Bukreeva, Ekaterina B.; Bulanova, Anna A.; Kistenev, Yurii V.; Kuzmin, Dmitry A.; Tuzikov, Sergei A.; Yumov, Evgenii L.

    2013-02-01

    It is important to identify patients with chronic obstructive pulmonary disease (COPD) and lung cancer in the early stages of the disease. The method of laser opto-acoustic gas analysis, in this case, can act as a promising tool for diagnostics. The material for this study were the gas emission samples collected from patients and healthy volunteers - samples of exhaled air, swabs from teeth and cheeks. A set of material was formed three groups: healthy volunteers, patients with COPD, lung cancer patients. The resulting samples were analyzed by means of laser opto-acoustic gas analyzers: with intracavity location detector (ILPA-1), with extracavity location detector (LGA-2). Presentation of the results in an easy to visual form was performed using the method of elastic maps, based on the principal component analysis. The results of analysis show potentialities of usage of laser optoacoustic spectroscopy application to assess the status of patients with chronic obstructive pulmonary disease and lung cancer.

  11. Automatic gas-levitation system for vacuum deposition of laser-fusion targets

    International Nuclear Information System (INIS)

    Jordan, C.W.; Cameron, G.R.; Krenik, R.M.; Crane, J.K.

    1981-01-01

    An improved simple system has been developed to gas-levitate microspheres during vacuum-deposition processes. The automatic operation relies on two effects: a lateral stabilizing force provided by a centering-ring; and an automatically incremented gas metering system to offset weight increases during coating

  12. Gas

    International Nuclear Information System (INIS)

    1996-01-01

    The French government has decided to modify the conditions of extension of local natural gas authorities to neighbouring districts. The European Union is studying the conditions of internal gas market with the objective of more open markets although considering public service requirements

  13. Contribution to the study of the simultaneous emission phenomena in molecular gas lasers

    International Nuclear Information System (INIS)

    Garnier, Jean-Pierre

    1974-01-01

    A selectively or simultaneously laser emission had been improved in a 12 CO 2 - 13 CO 2 -N 2 -He laser. 12 CO 2 wavelength near 945 cm -1 (10,58 μm), 13 CO 2 wavelength near 895 cm -1 (11,17 μm). The effect of CO 2 pressure, current intensity and isotopic enrichment in 13 C on the phenomena has been studied by measuring gain of a sealed laser amplifier containing CO 2 and its decomposition products (CO and O 2 ). A theoretical model has been established. A good agreement between theory and experiment has been obtained. The generalization of the phenomena to non-isotopic molecular systems has been experimentally verified with a mixture of CO 2 and N 2 O.(author) [fr

  14. Laser Annealing for Gas-Dynamical Spraying of HA Coating upon a Titanium Surface

    Directory of Open Access Journals (Sweden)

    Victor Saphronov

    2015-10-01

    Full Text Available Laser post-heating computer controlled detonation spraying (CCDS and cold spray (CS hybrid processes were proposed for fabrication of near sub micron structure coatings of hydroxyapatite (HA + Ti system. Optical and SEM with energy dispersive X-ray analysis and comparative XRD phase analysis were used to evaluate microstructure. After those hybrid processes, no substantial variation in HA composition was noted by structural and phase examination. Nano-sized HA powders can be recommended for laser annealing CS (LaCS process. Regimes of laser treatment optimal for increasing the adhesion between the HA and titanium coatings, providing more strength, ductility and decreasing of HA destruction in the coatings were determined.

  15. Coupling laser desorption with gas chromatography and ion mobility spectrometry for improved olive oil characterisation.

    Science.gov (United States)

    Liedtke, Sascha; Seifert, Luzia; Ahlmann, Norman; Hariharan, Chandrasekhara; Franzke, Joachim; Vautz, Wolfgang

    2018-07-30

    The investigation of volatile compounds in the headspace of liquid samples can often be used for detailed and non-destructive characterisation of the sample. This has great potential for process control or the characterisation of food samples, such as olive oil. We investigated, for the first time, the plume of substances released from olive oil droplets by laser desorption in a feasibility study and applied ion mobility spectrometry coupled to rapid GC pre-separation to enhance selectivity. Our investigation demonstrated that significantly more substances can be detected and quantified via laser desorption than in the usual headspace, enabling a rapid (5-10 min), sensitive (low ng/g range) and comprehensive analysis of the sample, with the potential for quality control and fraud identification. Therefore, laser desorption provides a useful sampling tool for characterising liquids in many applications, requiring only a few µL of sample. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Investigation of SOI Raman Lasers for Mid-Infrared Gas Sensing

    Science.gov (United States)

    Passaro, Vittorio M.N.; De Leonardis, Francesco

    2009-01-01

    In this paper, the investigation and detailed modeling of a cascaded Raman laser, operating in the midwave infrared region, is described. The device is based on silicon-on-insulator optical waveguides and a coupled resonant microcavity. Theoretical results are compared with recent experiments, demonstrating a very good agreement. Design criteria are derived for cascaded Raman lasers working as continuous wave light sources to simultaneously sense two types of gases, namely C2H6 and CO2, at a moderate power level of 130 mW. PMID:22408481

  17. Laser-induced transfer of nanoparticles for gas-phase analysis

    Czech Academy of Sciences Publication Activity Database

    Bulgakov, A.V.; Goodfriend, N.; Nerushev, O.; Bulgakova, Nadezhda M.; Starinskiy, S.V.; Shukhov, Y.G.; Campbell, E.E.B.

    2014-01-01

    Roč. 31, č. 11 (2014), C15-C21 ISSN 0740-3224 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : thin-films * gold-films * mass-spectrometer * excimer-laser * irradiation * deposition * ablation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.970, year: 2014

  18. Communication: Strong laser alignment of solvent-solute aggregates in the gas-phase

    Science.gov (United States)

    Trippel, Sebastian; Wiese, Joss; Mullins, Terry; Küpper, Jochen

    2018-03-01

    Strong quasi-adiabatic laser alignment of the indole-water-dimer clusters, an amino-acid chromophore bound to a single water molecule through a hydrogen bond, was experimentally realized. The alignment was visualized through ion and electron imaging following strong-field ionization. Molecular-frame photoelectron angular distributions showed a clear suppression of the electron yield in the plane of the ionizing laser's polarization, which was analyzed as strong alignment of the molecular cluster with ⟨cos2 θ2D⟩ ≥ 0.9.

  19. Formation of the active medium in high-power repetitively pulsed gas lasers pumped by an electron-beam-controlled discharge

    Science.gov (United States)

    Bulaev, V. D.; Lysenko, S. L.

    2015-07-01

    A high-power repetitively pulsed e-beam-controlled discharge CO2 laser is simulated numerically; the simulation results are compared with experimental data. Optimal sizes and design of electrodes and configuration of the external magnetic field are found, which allow one to introduce no less than 90% electric pump energy into a specified volume of the active medium, including the active volume of a laser with an aperture of 110 × 110 cm. The results obtained can also be used to design other types of highpower gas lasers.

  20. Fiber-Based, Trace-Gas, Laser Transmitter Technology Development for Space

    Science.gov (United States)

    Stephen, Mark; Yu, Anthony; Chen, Jeffrey; Nicholson, Jeffrey; Engin, Doruk; Mathason, Brian; Wu, Stewart; Allan, Graham; Hasselbrack, William; Gonzalez, Brayler; hide

    2015-01-01

    NASA’s Goddard Space Flight Center (GSFC) is working on maturing the technology readiness of a laser transmitter designed for use in atmospheric CO2 remote-sensing. GSFC has been developing an airplane-based CO2 lidar instrument over several years to demonstrate the efficacy of the instrumentation and measurement technique and to link the science models to the instrument performance. The ultimate goal is to make space-based satellite measurements with global coverage. In order to accomplish this, we must demonstrate the technology readiness and performance of the components as well as demonstrate the required power-scaling to make the link with the required signal-to-noise-ratio (SNR). To date, all the instrument components have been shown to have the required performance with the exception of the laser transmitter.In this program we are working on a fiber-based master oscillator power amplifier (MOPA) laser transmitter architecture where we will develop a ruggedized package and perform the relevant environmental tests to demonstrate TRL-6. In this paper we will review our transmitter architecture and progress on the performance and packaging of the laser transmitter.

  1. Applications of cw quantum cascade laser near 8 μm in gas sensing research

    KAUST Repository

    Sajid, Muhammad Bilal

    2014-01-01

    Quantum cascade laser based sensors operating near 8 μm to detect H2O2, C2H2, CH4, N2O and H2O are discussed and demonstrated for applications in chemical kinetics, combustion and spectroscopic measurements.

  2. Diode Laser-Based Sensor for Fast Measurement of Binary Gas Mixtures

    National Research Council Canada - National Science Library

    McNesby, Kevin

    1999-01-01

    The development and characterization of a gas sensor to measure binary mixtures of oxygen and the vapor from a series of volatile organic compounds, with a time resolution of 10 milliseconds, is described...

  3. A comparative study of pressure-dependent emission characteristics in different gas plasmas induced by nanosecond and picosecond neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers.

    Science.gov (United States)

    Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Marpaung, Alion Mangasi; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Suliyanti, Maria Margaretha; Ramli, Muliadi; Suyanto, Heri; Kagawa, Kiichiro; Tjia, May On; Lie, Zener Sukra; Lie, Tjung Jie; Kurniawan, Hendrik Koo

    2013-11-01

    An experimental study has been performed on the pressure-dependent plasma emission intensities in Ar, He, and N2 surrounding gases with the plasma induced by either nanosecond (ns) or picosecond (ps) yttrium aluminum garnet laser. The study focused on emission lines of light elements such as H, C, O, and a moderately heavy element of Ca from an agate target. The result shows widely different pressure effects among the different emission lines, which further vary with the surrounding gases used and also with the different ablation laser employed. It was found that most of the maximum emission intensities can be achieved in Ar gas plasma generated by ps laser at low gas pressure of around 5 Torr. This experimental condition is particularly useful for spectrochemical analysis of light elements such as H, C, and O, which are known to suffer from intensity diminution at higher gas pressures. Further measurements of the spatial distribution and time profiles of the emission intensities of H I 656.2 nm and Ca II 396.8 nm reveal the similar role of shock wave excitation for the emission in both ns and ps laser-induced plasmas, while an additional early spike is observed in the plasma generated by the ps laser. The suggested preference of Ar surrounding gas and ps laser was further demonstrated by outperforming the ns laser in their applications to depth profiling of the H emission intensity and offering the prospect for the development of three-dimensional analysis of a light element such as H and C.

  4. Cropland Field Monitoring: MMV Page 1 Montana Cropland Enrolled Farm Fields Carbon Sequestration Field Sampling, Measurement, Monitoring, and Verification: Application of Visible-Near Infrared Diffuse Reflectance Spectroscopy (VNIR) and Laser-induced Breakdown Spectroscopy (LIBS)

    Energy Technology Data Exchange (ETDEWEB)

    Lee Spangler; Ross Bricklemyer; David Brown

    2012-03-15

    There is growing need for rapid, accurate, and inexpensive methods to measure, and verify soil organic carbon (SOC) change for national greenhouse gas accounting and the development of a soil carbon trading market. Laboratory based soil characterization typically requires significant soil processing, which is time and resource intensive. This severely limits application for large-region soil characterization. Thus, development of rapid and accurate methods for characterizing soils are needed to map soil properties for precision agriculture applications, improve regional and global soil carbon (C) stock and flux estimates and efficiently map sub-surface metal contamination, among others. The greatest gains for efficient soil characterization will come from collecting soil data in situ, thus minimizing soil sample transportation, processing, and lab-based measurement costs. Visible and near-infrared diffuse reflectance spectroscopy (VisNIR) and laser-induced breakdown spectroscopy (LIBS) are two complementary, yet fundamentally different spectroscopic techniques that have the potential to meet this need. These sensors have the potential to be mounted on a soil penetrometer and deployed for rapid soil profile characterization at field and landscape scales. Details of sensor interaction, efficient data management, and appropriate statistical analysis techniques for model calibrations are first needed. In situ or on-the-go VisNIR spectroscopy has been proposed as a rapid and inexpensive tool for intensively mapping soil texture and organic carbon (SOC). While lab-based VisNIR has been established as a viable technique for estimating various soil properties, few experiments have compared the predictive accuracy of on-the-go and lab-based VisNIR. Eight north central Montana wheat fields were intensively interrogated using on-the-go and lab-based VisNIR. Lab-based spectral data consistently provided more accurate predictions than on-the-go data. However, neither in situ

  5. A Miniaturized Laser Heterodyne Radiometer for Greenhouse Gas Measurements in the Atmospheric Column

    Science.gov (United States)

    Steel, Emily Wilson

    2015-01-01

    Laser Heterodyne Radiometry is a technique adapted from radio receiver technology has been used to measure trace gases in the atmosphere since the 1960s.By leveraging advances in the telecommunications industry, it has been possible to miniaturize this technology.The mini-LHR (Miniaturized Laser Heterodyne Radiometer) has been under development at NASA Goddard Space flight Center since 2009. This sun-viewing instrument measures carbon dioxide and methane in the atmospheric column and operates in tandem with an AERONET sun photometer producing a simultaneous measure of aerosols. The mini-LHR has been extensively field tested in a range of locations ranging in the continental US as well as Alaska and Hawaii and now operates autonomously with sensitivities of approximately 0.2 ppmv and approximately10 ppbv, for carbon dioxide and methane respectively, for 10 averaged scans under clear sky conditions.

  6. Design of Composite Photocatalyst of TiO2 and Y-Zeolite for Degradation of 2-Propanol in the Gas Phase under UV and Visible Light Irradiation

    OpenAIRE

    Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

    2014-01-01

    Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the ...

  7. Megawatt Ultraviolet Laser Photolysis of Dichloroethenes for Gas-Phase Deposition of Nanosized Chlorinated Soot

    Czech Academy of Sciences Publication Activity Database

    Pola, Josef; Galíková, Anna; Bakardjieva, Snejana; Šubrt, Jan; Bastl, Zdeněk; Vorlíček, Vladimír; Maryško, Miroslav; Ouchi, A.

    2010-01-01

    Roč. 114, č. 39 (2010), s. 16153-16159 ISSN 1932-7447 R&D Projects: GA AV ČR IAA400720619 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40320502; CEZ:AV0Z40400503; CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : laser-induced photolysis * dichloroethene * chlorinated carbon Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.520, year: 2010

  8. TRANSPARENCY METERS AND GAS ANALYZERS BASED ON TWO-WAVELENGTH SEMICONDUCTOR LASERS

    Directory of Open Access Journals (Sweden)

    V. L. Kozlov

    2011-01-01

    Full Text Available Construction techniques of precision measuring instruments of optical characteristics on the basis of two-wave lasers with use of basic and nephelometer methods are presented. System stability to changes of hardware constants, influence of an environment, pollution of optics is shown. The system automatically takes into account changes of a controllable line length that expands functionalities of a measuring instrument. 

  9. Nano-Structured Crystalline Te Films by Laser Gas-Phase Pyrolysis of Dimethyl Tellurium

    Czech Academy of Sciences Publication Activity Database

    Pola, Josef; Pokorná, Veronika; Boháček, Jaroslav; Bastl, Zdeněk; Ouchi, A.

    2004-01-01

    Roč. 71, č. 2 (2004), s. 739-746 ISSN 0165-2370 R&D Projects: GA AV ČR IAA4072107; GA MŠk OC 523.60 Institutional research plan: CEZ:AV0Z4072921; CEZ:AV0Z4032918; CEZ:AV0Z4040901 Keywords : dimethyl tellurium * tellurium films * laser Subject RIV: CA - Inorganic Chemistry Impact factor: 1.352, year: 2004

  10. In gas laser ionization and spectroscopy experiments at the Superconducting Separator Spectrometer (S{sup 3}): Conceptual studies and preliminary design

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer, R., E-mail: Rafael.Ferrer@fys.kuleuven.be [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Bastin, B.; Boilley, D. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Creemers, P. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Delahaye, P. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Liénard, E.; Fléchard, X. [LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen (France); Franchoo, S. [Institut de Physique Nucléaire (IPN) d’Orsay, 91406 Orsay Cedex (France); Ghys, L. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); SCK-CEN, Belgian Nuclear Research Center, Boeretang 200, 2400 Mol (Belgium); Huyse, M.; Kudryavtsev, Yu. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Lecesne, N.; Lu, H.; Lutton, F. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Mogilevskiy, E.; Pauwels, D. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Piot, J. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); Radulov, D.; Rens, L. [KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Savajols, H. [GANIL, CEA/DSM-CNRS/IN2P3, B.P. 55027, 14076 Caen (France); and others

    2013-12-15

    Highlights: • A setup to perform In-Gas Laser Ionization and Spectroscopy experiments at the Super Separator Spectrometer is presented. • The reported studies address important aspects necessary to applied the IGLIS technique to short-lived isotopes. • An R and D phase required to reach an enhanced spectral resolution will be carried out at KU Leuven. • High-sensitivity and enhanced-resolution laser spectroscopy studies will be possible with the IGLIS setup at S{sub 3}. -- Abstract: The results of preparatory experiments and the preliminary designs of a new in-gas laser ionization and spectroscopy setup, to be coupled to the Super Separator Spectrometer S{sup 3} of SPIRAL2-GANIL, are reported. Special attention is given to the development and tests to carry out a full implementation of the in-gas jet laser spectroscopy technique. Application of this novel technique to radioactive species will allow high-sensitivity and enhanced-resolution laser spectroscopy studies of ground- and excited-state properties of exotic nuclei.

  11. Gigabit-per-second white light-based visible light communication using near-ultraviolet laser diode and red-, green-, and blue-emitting phosphors

    KAUST Repository

    Lee, Changmin

    2017-07-12

    Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021) substrate emitting at 410 nm was used for the transmitter. The measured modulation bandwidth of the LD was 1 GHz, which was limited by the avalanche photodetector. The emission from the NUV LD and the RGB phosphor combination measured a color rendering index (CRI) of 79 and correlated color temperature (CCT) of 4050 K, indicating promise of this approach for creating high quality white lighting. Using this configuration, data was successfully transmitted at a rate of more than 1 Gbps. This NUV laser-based system is expected to have lower background noise from sunlight at the LD emission wavelength than a system that uses a blue LD due to the rapid fall off in intensity of the solar spectrum in the NUV spectral region.

  12. CO2 Laser acceleration of forward directed MeV proton beams in a gas target at critical plasma density

    Science.gov (United States)

    Tsung, F.; Tochitsky, S. Ya.; Haberberger, D. J.; Mori, W. B.; Joshi, C.

    2012-08-01

    The generation of 1-5 MeV protons from the interaction of a 3 ps TW CO2 laser pulse with a gas target with a peak density around the critical plasma density has been studied by 2D particle-in-cell simulations. The proton acceleration in the preformed plasma with a symmetric, linearly ramped density distribution occurs via formation of sheath of the hot electrons on the back surface of the target. The maximum energy of the hot electrons and, hence, net acceleration of protons is mainly defined by Forward Raman scattering instability in the underdense part of the plasma. Forward directed ion beams from a debris free gaseous target can find an application as a high-brightness ion source-injector to a conventional accelerator operating up to kHz pulse repetition frequency.

  13. Enhancement of wear and corrosion resistance of beta titanium alloy by laser gas alloying with nitrogen

    Science.gov (United States)

    Chan, Chi-Wai; Lee, Seunghwan; Smith, Graham; Sarri, Gianluca; Ng, Chi-Ho; Sharba, Ahmed; Man, Hau-Chung

    2016-03-01

    The relatively high elastic modulus coupled with the presence of toxic vanadium (V) in Ti6Al4V alloy has long been a concern in orthopaedic applications. To solve the problem, a variety of non-toxic and low modulus beta-titanium (beta-Ti) alloys have been developed. Among the beta-Ti alloy family, the quaternary Ti-Nb-Zr-Ta (TNZT) alloys have received the highest attention as a promising replacement for Ti6Al4V due to their lower elastic modulus and outstanding long term stability against corrosion in biological environments. However, the inferior wear resistance of TNZT is still a problem that must be resolved before commercialising in the orthopaedic market. In this work, a newly developed laser surface treatment technique was employed to improve the surface properties of Ti-35.3Nb-7.3Zr-5.7Ta alloy. The surface structure and composition of the laser-treated TNZT surface were examined by grazing incidence X-ray diffraction (GI-XRD) and X-ray photoelectron spectroscopy (XPS). The wear and corrosion resistance were evaluated by pin-on-plate sliding test and anodic polarisation test in Hanks' solution. The experimental results were compared with the untreated (or base) TNZT material. The research findings showed that the laser surface treatment technique reported in this work can effectively improve the wear and corrosion resistance of TNZT.

  14. Pulsed X-ray radiography of a gas jet target for laser-matter interaction experiments with the use of a CCD detector

    International Nuclear Information System (INIS)

    Rakowski, R.; Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; MikoIajczyk, J.; Szczurek, A.; Szczurek, M.; Foeldes, I.B.; Toth, Zs.

    2005-01-01

    Characterization of gas jet targets has been carried out using pulsed X-ray radiography. A laser-plasma X-ray source was applied for backlighting of the targets to obtain X-ray shadowgraphs registered with a CCD detector. From the shadowgraphs, characteristics of the targets were determined

  15. Stability and performance improvement of a polymer electrolyte membrane fuel cell stack by laser perforation of gas diffusion layers

    Energy Technology Data Exchange (ETDEWEB)

    Gerteisen, Dietmar; Sadeler, Christian [Fraunhofer Institute for Solar Energy Systems ISE, Department of Energy Technology, Heidenhofstrasse 2, 79110 Freiburg (Germany)

    2010-08-15

    The performance and stability of a hydrogen-driven polymer electrolyte membrane fuel cell stack (6-cell PEFC stack) are investigated with regard to pore flooding within the gas diffusion layers (GDLs). Two short stacks with various GDLs (Toray TGP-H-060 untreated and laser-perforated) were characterized at different operating conditions by several characterization techniques such as constant current load, polarization curve, chronoamperometry and chronovoltammetry. The experimental results reveal that the perforation of the cathode GDLs improves the water transport in the porous media and thus the performance as well as the stability of the operating stack in medium and high current density range. A reduced pore flooding is verified when using the customized laser-perforated GDLs. The GDL perforation has a huge potential to balance the inhomogeneous in-plane saturation conditions between the inlet and outlet area of the cell and to compensate to a certain degree the effects of temperature distribution within a stack regarding the water management. (author)

  16. Stability and performance improvement of a polymer electrolyte membrane fuel cell stack by laser perforation of gas diffusion layers

    Science.gov (United States)

    Gerteisen, Dietmar; Sadeler, Christian

    The performance and stability of a hydrogen-driven polymer electrolyte membrane fuel cell stack (6-cell PEFC stack) are investigated with regard to pore flooding within the gas diffusion layers (GDLs). Two short stacks with various GDLs (Toray TGP-H-060 untreated and laser-perforated) were characterized at different operating conditions by several characterization techniques such as constant current load, polarization curve, chronoamperometry and chronovoltammetry. The experimental results reveal that the perforation of the cathode GDLs improves the water transport in the porous media and thus the performance as well as the stability of the operating stack in medium and high current density range. A reduced pore flooding is verified when using the customized laser-perforated GDLs. The GDL perforation has a huge potential to balance the inhomogeneous in-plane saturation conditions between the inlet and outlet area of the cell and to compensate to a certain degree the effects of temperature distribution within a stack regarding the water management.

  17. Tunable diode laser IR spectrometer for in situ measurements of the gas phase composition and particle size distribution of Titan's atmosphere

    Science.gov (United States)

    Webster, Christopher R.; Sander, Stanley P.; Beer, Reinhard; May, Randy D.; Knollenberg, Robert G.

    1990-01-01

    A new instrument, the Probe Infrared Laser Spectrometer (PIRLS), is described for in situ sensing of the gas composition and particle size distribution of Titan's atmosphere on the NASA/ESA Cassini mission. For gas composition measurements, several narrow-band (0.0001/cm) tunable lead-salt diode lasers operating near 80 K at selected mid-IR wavelengths are directed over a path length defined by a small reflector extending over the edge of the probe spacecraft platform; volume mixing ratios of 10 to the -9th should be measurable for several species of interest. A cloud-particle-size spectrometer using a diode laser source at 780 nm shares the optical path and deployed reflector; a combination of imaging and light scattering techniques is used to determine sizes of haze and cloud particles and their number density as a function of altitude.

  18. Low-visibility light-intensity laser-triggered release of entrapped calcein from 1,2-bis (tricosa-10,12-diynoyl-sn-glycero-3-phosphocholine liposomes is mediated through a type I photoactivation pathway

    Directory of Open Access Journals (Sweden)

    Yavlovich A

    2013-07-01

    only the Cal-G loaded photo-triggerable liposomes but not from Cal-B-loaded liposomes (≤10 µM H2O2. The Cal-G release from photo-triggerable liposomes was found to be significantly inhibited by ascorbic acid (AA, resulting in a 70%–80% reduction in Cal-G release. The extent of AA-mediated inhibition of Cal-G release from the liposomes also correlated with the consumption of AA. No AA consumption was detected in the 514 nm laser-exposed Cal B-loaded liposomes, thus confirming a role of photoactivation of Cal-G in liposome destabilization. Inclusion of 100 mM K3Fe(CN6 (a blocker of electron transfer in the liposomes substantially inhibited Cal-G release, whereas inclusion of 10 mM sodium azide (a blocker of singlet oxygen of type II photoreaction in the liposomes failed to block 514 nm laser-triggered Cal-G release. Taken together, we conclude that low-intensity 514 nm laser-triggered release of Cal-G from photo-triggerable liposomes involves the type I photoreaction pathway.Keywords: visible laser-triggered payload release, photo-agents, photopolymerizable phospholipids, photodynamic actions, reactive oxygen species

  19. 2D numerical modelling of gas temperature in a nanosecond pulsed longitudinal He-SrBr2 discharge excited in a high temperature gas-discharge tube for the high-power strontium laser

    Science.gov (United States)

    Chernogorova, T. P.; Temelkov, K. A.; Koleva, N. K.; Vuchkov, N. K.

    2016-05-01

    An active volume scaling in bore and length of a Sr atom laser excited in a nanosecond pulse longitudinal He-SrBr2 discharge is carried out. Considering axial symmetry and uniform power input, a 2D model (r, z) is developed by numerical methods for determination of gas temperature in a new large-volume high-temperature discharge tube with additional incompact ZrO2 insulation in the discharge free zone, in order to find out the optimal thermal mode for achievement of maximal output laser parameters. A 2D model (r, z) of gas temperature is developed by numerical methods for axial symmetry and uniform power input. The model determines gas temperature of nanosecond pulsed longitudinal discharge in helium with small additives of strontium and bromine.

  20. A Gas-Solid Singlet Delta Oxygen Generator for the Chemical Iodine Laser

    National Research Council Canada - National Science Library

    Alfano, Angelo

    2002-01-01

    ... at 1.27 microns by passing chlorine gas through aqueous, basic hydrogen peroxide (H2O2/OH). Unfortunately, the process of nonradiative relaxation used in COIL results in the creation of undesired heat and not the desired light emission...

  1. Simultaneous high-speed gas property measurements at the exhaust gas recirculation cooler exit and at the turbocharger inlet of a multicylinder diesel engine using diode-laser-absorption spectroscopy.

    Science.gov (United States)

    Jatana, Gurneesh S; Magee, Mark; Fain, David; Naik, Sameer V; Shaver, Gregory M; Lucht, Robert P

    2015-02-10

    A diode-laser-absorption-spectroscopy-based sensor system was used to perform high-speed (100 Hz to 5 kHz) measurements of gas properties (temperature, pressure, and H(2)O vapor concentration) at the turbocharger inlet and at the exhaust gas recirculation (EGR) cooler exit of a diesel engine. An earlier version of this system was previously used for high-speed measurements of gas temperature and H(2)O vapor concentration in the intake manifold of the diesel engine. A 1387.2 N m tunable distributed feedback diode laser was used to scan across multiple H(2)O absorption transitions, and the direct absorption signal was recorded using a high-speed data acquisition system. Compact optical connectors were designed to conduct simultaneous measurements in the intake manifold, the EGR cooler exit, and the turbocharger inlet of the engine. For measurements at the turbocharger inlet, these custom optical connectors survived gas temperatures as high as 800 K using a simple and passive arrangement in which the temperature-sensitive components were protected from high temperatures using ceramic insulators. This arrangement reduced system cost and complexity by eliminating the need for any active water or oil cooling. Diode-laser measurements performed during steady-state engine operation were within 5% of the thermocouple and pressure sensor measurements, and within 10% of the H(2)O concentration values derived from the CO(2) gas analyzer measurements. Measurements were also performed in the engine during transient events. In one such transient event, where a step change in fueling was introduced, the diode-laser sensor was able to capture the 30 ms change in the gas properties; the thermocouple, on the other hand, required 7.4 s to accurately reflect the change in gas conditions, while the gas analyzer required nearly 600 ms. To the best of our knowledge, this is the first implementation of such a simple and passive arrangement of high-temperature optical connectors as well

  2. Experimental and computational study of the effect of 1 atm background gas on nanoparticle generation in femtosecond laser ablation of metals

    Science.gov (United States)

    Wu, Han; Wu, Chengping; Zhang, Nan; Zhu, Xiaonong; Ma, Xiuquan; Zhigilei, Leonid V.

    2018-03-01

    Laser ablation of metal targets is actively used for generation of chemically clean nanoparticles for a broad range of practical applications. The processes involved in the nanoparticle formation at all relevant spatial and temporal scales are still not fully understood, making the precise control of the size and shape of the nanoparticles challenging. In this paper, a combination of molecular dynamics simulations and experiments is applied to investigate femtosecond laser ablation of aluminum targets in vacuum and in 1 atm argon background gas. The results of the simulations reveal a strong effect of the background gas environment on the initial plume expansion and evolution of the nanoparticle size distribution. The suppression of the generation of small/medium-size Al clusters and formation of a dense layer at the front of the expanding ablation plume, observed during the first nanosecond of the plume expansion in a simulation performed in the gas environment, have important implications on the characteristics of the nanoparticles deposited on a substrate and characterized in the experiments. The nanoparticles deposited in the gas environment are found to be more round-shaped and less flattened as compared to those deposited in vacuum. The nanoparticle size distributions exhibit power-law dependences with similar values of exponents obtained from fitting experimental and simulated data. Taken together, the results of this study suggest that the gas environment may be effectively used to control size and shape of nanoparticles generated by laser ablation.

  3. Seeding the FEL of the SCSS Phase 1 Facility with the 13th Laser Harmonic of a Ti Sa Laser (61.5 nm) Produced in Xe Gas

    CERN Document Server

    Lambert, G; Boutu, W; Breger, P; Couprie, M E; Garzella, D; Merdji, H; Monchicourt, P; Salieres, P

    2005-01-01

    In order to reach very short wavelengths in FEL, and to have a more compact, fully coherent and tunable source, a particular seeding configuration is foreseen to be tested as a demonstration experiment in 2006 into the SCSS phase 1 facility (Spring-8 Compact Sase Source, Japan). The external source is the 13th harmonic (61.5 nm) of a Ti: Sa laser (25 mJ, 10 Hz, 100 fs) generated in 10 Hz pulsed Xe gas cell. The harmonic generation process provides us with a intense (1 μJ) and ultra-short (50 fs) VUV beam. The design of the experiment implantation is discussed, taken into account the performances of the generation process, the focusing of the selected harmonic into the modulator, and the resistance of the optical components. Besides one should consider the vacuum needs, the geometrical problems and the mechanics for the under UHV mirrors translation. One first chamber is dedicated to the harmonic generation. A second one is used for spectral selection and adaptation of the harmonic in the modulator. F...

  4. Laser-induced gratings in the gas phase excited via Raman-active transitions

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, D.N. [General Physics Inst., Russian Academy of Sciences, Moscow (Russian Federation); Bombach, R.; Hemmerling, B.; Hubschmid, W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    We report on a new time resolved coherent Raman technique that is based on the generation of thermal gratings following a population change among molecular levels induced by stimulated Raman pumping. This is achieved by spatially and temporally overlapping intensity interference patterns generated independently by two lasers. When this technique is used in carbon dioxide, employing transitions which belong to the Q-branches of the {nu}{sub 1}/2{nu}{sub 2} Fermi dyad, it is possible to investigate molecular energy transfer processes. (author) 2 figs., 10 refs.

  5. In situ laser-induced breakdown spectroscopy measurements of chemical compositions in stainless steels during tungsten inert gas welding

    Science.gov (United States)

    Taparli, Ugur Alp; Jacobsen, Lars; Griesche, Axel; Michalik, Katarzyna; Mory, David; Kannengiesser, Thomas

    2018-01-01

    A laser-induced breakdown spectroscopy (LIBS) system was combined with a bead-on-plate Tungsten Inert Gas (TIG) welding process for the in situ measurement of chemical compositions in austenitic stainless steels during welding. Monitoring the weld pool's chemical composition allows governing the weld pool solidification behavior, and thus enables the reduction of susceptibility to weld defects. Conventional inspection methods for weld seams (e.g. ultrasonic inspection) cannot be performed during the welding process. The analysis system also allows in situ study of the correlation between the occurrence of weld defects and changes in the chemical composition in the weld pool or in the two-phase region where solid and liquid phase coexist. First experiments showed that both the shielding Ar gas and the welding arc plasma have a significant effect on the selected Cr II, Ni II and Mn II characteristic emissions, namely an artificial increase of intensity values via unspecific emission in the spectra. In situ investigations showed that this artificial intensity increase reached a maximum in presence of weld plume. Moreover, an explicit decay has been observed with the termination of the welding plume due to infrared radiation during sample cooling. Furthermore, LIBS can be used after welding to map element distribution. For austenitic stainless steels, Mn accumulations on both sides of the weld could be detected between the heat affected zone (HAZ) and the base material.

  6. Acceleration of Vaporization, Atomization, and Ionization Efficiencies in Inductively Coupled Plasma by Merging Laser-Ablated Particles with Hydrochloric Acid Gas.

    Science.gov (United States)

    Nakazawa, Takashi; Izumo, Saori; Furuta, Naoki

    2016-01-01

    To accelerate the vaporization, atomization, and ionization efficiencies in laser ablation inductively coupled plasma mass spectrometry, we merged HCl gas with laser-ablated particles before introduction into the plasma, to convert their surface constituents from oxides to lower-melting chlorides. When particles were merged with HCl gas generated from a HCl solution at 200°C, the measured concentrations of elements in the particles were 135% higher on average than the concentrations in particles merged with ultrapure water vapor. Particle corrosion and surface roughness were observed by scanning electron microscopy, and oxide conversion to chlorides was confirmed by X-ray photoelectron spectroscopy. Under the optimum conditions, the recoveries of measured elements improved by 23% on average, and the recoveries of elements with high-melting oxides (Sr, Zr, and Th) improved by as much as 36%. These results indicate that vaporization, atomization, and ionization in the ICP improved when HCl gas was merged with the ablated particles.

  7. High K-alpha X-ray Conversion Efficiency From Extended Source Gas Jet Targets Irradiated by Ultra Short Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Kugland, N L; Constantin, C; Collette, A; Dewald, E; Froula, D; Glenzer, S H; Kritcher, A; Neumayer, P; Ross, J S; Niemann, C

    2007-11-01

    The absolute laser conversion efficiency to K{sub {alpha}}-like inner shell x-rays (integrated from K{sub {alpha}} to K{sub {beta}}) is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K{sub {alpha}} is the same in gas jets as in solid targets. These results demonstrate that gas jet targets are bright, high conversion efficiency, high repetition rate, debris-free multi-keV x-ray sources for spectrally resolved scattering and backlighting of rapidly evolving dense matter.

  8. Two- and Three-Component Visible Light Photoinitiating Systems for Radical Polymerization Based on Onium Salts: An Overview of Mechanistic and Laser Flash Photolysis Studies

    Directory of Open Access Journals (Sweden)

    María L. Gómez

    2012-01-01

    Full Text Available A review of our work on two- and-three component photoinitiator systems is presented. The emphasis is in on visible light polymerization in aqueous media. The systems discussed comprise a synthetic dye as sensitizer and an onium salt as coinitiator, or a dye-amine-onium salt with the amine as coinitiator and the onium salt as an enhancer of the polymerization efficiency. The effect of the composition of the system on the photopolymerization kinetics was analyzed. To this end, the photophysics and photochemistry of the dye under polymerization conditions was explored by means of stationary and time-resolved spectroscopic methods. Different dyes and onium salts were investigated. The action mechanism of the different photoinitiators systems is discussed.

  9. Application of multi-way analysis to UV–visible spectroscopy, gas chromatography and electronic nose data for wine ageing evaluation

    International Nuclear Information System (INIS)

    Prieto, N.; Rodriguez-Méndez, M.L.; Leardi, R.; Oliveri, P.; Hernando-Esquisabel, D.; Iñiguez-Crespo, M.; Saja, J.A. de

    2012-01-01

    Highlights: ► Wine samples were analytically characterised according to their ageing process. ► Signals from a sensor-based electronic nose were fused with GC–MS and UV–visible data. ► The study involved 6 periodical determinations of 20 variables on 6 different wines. ► Multi-way analysis allowed to efficiently extract the maximum information from data. ► Multi-way methods represent the most suitable tool for processing three-mode data. - Abstract: In this study, a multi-way method (Tucker3) was applied to evaluate the performance of an electronic nose for following the ageing of red wines. The odour evaluation carried out with the electronic nose was combined with the quantitative analysis of volatile composition performed by GC–MS, and colour characterisation by UV–visible spectroscopy. Thanks to Tucker3, it was possible to understand connections among data obtained from these three different systems and to estimate the effect of different sources of variability on wine evaluation. In particular, the application of Tucker3 supplied a global visualisation of data structure, which was very informative to understand relationships between sensors responses and chemical composition of wines. The results obtained indicate that the analytical methods employed are useful tools to follow the wine ageing process, to differentiate wine samples according to ageing type (either in barrel or in stainless steel tanks with the addition of small oak wood pieces) and to the origin (French or American) of the oak wood. Finally, it was possible to designate the volatile compounds which play a major role in such a characterisation.

  10. Use of TiO{sub 2}/Cr-MCM-41 molecular sieve irradiated with visible light for the degradation of thiophene in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Fabielle C.; Canela, Maria Cristina; Stumbo, Alexandre M. [Laboratorio de Ciencias Quimicas (LCQUI), Universidade Estadual do Norte Fluminense Darcy Ribeiro, Av. Alberto Lamego, 2000 Campos dos Goytacazes-RJ, CEP 28013-602 (Brazil)

    2008-04-15

    Photocatalytic processes using TiO{sub 2} and UV radiation to eliminate pollutants are not yet suitable for industrial facilities due to their high consumption of energy. Transition metals incorporated onto mesoporous MCM-41 molecular sieves impregnated with TiO{sub 2} constitute an alternative that allows the use of solar light. In this study, Cr-substituted MCM-41 were synthesized (Si/Cr = 100, 50 and {infinity}) and impregnated with TiO{sub 2} (10 and 20 wt.%). Raman results showed the formation of anatase. Electronic spectroscopy and EPR exposed the formation of trivalent chromium after impregnation with TiO{sub 2}, which is related to a Cr-TiO{sub 2} interaction. The synthesized photocatalysts, as well as TiO{sub 2} P25, were tested in the degradation of thiophene in gaseous phase. A test with UV lamp showed 100% of conversion for 20%TiO{sub 2}/Cr-MCM-41(100) and exceeded the activity of TiO{sub 2} P25, probably due to the higher dispersion of TiO{sub 2} on the surface of the molecular sieve. During tests using visible light and 20%TiO{sub 2}/Cr-MCM-41(50) higher conversions than those of 20%TiO{sub 2}/Cr-MCM-41(100) and TiO{sub 2} P25 were observed. These results indicate that chromium concentration is a key factor influencing the photocatalytic activity under visible light. (author)

  11. Application of multi-way analysis to UV-visible spectroscopy, gas chromatography and electronic nose data for wine ageing evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, N. [Department of Condensed Matter Physics, Faculty of Sciences, University of Valladolid, 47011 Valladolid (Spain); Department of Inorganic Chemistry, Escuela de Ingenierias Industriales, University of Valladolid, Paseo del Cauce, 59, 47011 Valladolid (Spain); Rodriguez-Mendez, M.L. [Department of Inorganic Chemistry, Escuela de Ingenierias Industriales, University of Valladolid, Paseo del Cauce, 59, 47011 Valladolid (Spain); Leardi, R. [Department of Pharmaceutical and Food Chemistry and Technology, University of Genoa, Via Brigata Salerno 13, I-16147 8 Genoa (Italy); Oliveri, P., E-mail: oliveri@dictfa.unige.it [Department of Pharmaceutical and Food Chemistry and Technology, University of Genoa, Via Brigata Salerno 13, I-16147 8 Genoa (Italy); Hernando-Esquisabel, D.; Iniguez-Crespo, M. [Gobierno de la Rioja, Consejeria de Agricultura y Alimentacion, Estacion Enologica, Breton de los Herreros 4, 26200 Haro, La Rioja (Spain); Saja, J.A. de [Department of Condensed Matter Physics, Faculty of Sciences, University of Valladolid, 47011 Valladolid (Spain)

    2012-03-16

    Highlights: Black-Right-Pointing-Pointer Wine samples were analytically characterised according to their ageing process. Black-Right-Pointing-Pointer Signals from a sensor-based electronic nose were fused with GC-MS and UV-visible data. Black-Right-Pointing-Pointer The study involved 6 periodical determinations of 20 variables on 6 different wines. Black-Right-Pointing-Pointer Multi-way analysis allowed to efficiently extract the maximum information from data. Black-Right-Pointing-Pointer Multi-way methods represent the most suitable tool for processing three-mode data. - Abstract: In this study, a multi-way method (Tucker3) was applied to evaluate the performance of an electronic nose for following the ageing of red wines. The odour evaluation carried out with the electronic nose was combined with the quantitative analysis of volatile composition performed by GC-MS, and colour characterisation by UV-visible spectroscopy. Thanks to Tucker3, it was possible to understand connections among data obtained from these three different systems and to estimate the effect of different sources of variability on wine evaluation. In particular, the application of Tucker3 supplied a global visualisation of data structure, which was very informative to understand relationships between sensors responses and chemical composition of wines. The results obtained indicate that the analytical methods employed are useful tools to follow the wine ageing process, to differentiate wine samples according to ageing type (either in barrel or in stainless steel tanks with the addition of small oak wood pieces) and to the origin (French or American) of the oak wood. Finally, it was possible to designate the volatile compounds which play a major role in such a characterisation.

  12. Strong soft X-ray emission from a double-stream gas puff target irradiated with a nanosecond Nd:YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Fiedorowicz, H.; Bartnik, A.; Rakowski, R.; Szczurek, M. [Military Univ. of Technology, Warsaw (Poland). Inst. of Optoelectronics; Daido, H.; Suzuki, M.; Yamagami, S.; Choi, I.W.; Tang, H.J. [Osaka Univ., Suita (Japan). Inst. of Laser Engineering

    2001-07-01

    Soft X-ray emission from a new double-stream gas puff target irradiated with a nanosecond, high-power Nd:YAG laser pulse has been studied. The target was formed by pulsed injection of gas into a hollow gas stream made from helium by using a double-nozzle setup. Strong X-ray emissions near 10 nm from the double-stream krypton/helium, near 11 nm from the xenon/helium, and at 13 nm from the oxygen/helium targets were observed. The emission from the double-stream gas puff target was several times higher as compared to the ordinary gas puff targets, and comparable to the emission from the solid targets irradiated in the same conditions. (orig.)

  13. Laser flash-photolysis and gas discharge in N2O-containing mixture: kinetic mechanism

    Science.gov (United States)

    Kosarev, Ilya; Popov, Nikolay; Starikovskaia, Svetlana; Starikovskiy, Andrey; mipt Team

    2011-10-01

    The paper is devoted to further experimental and theoretical analysis of ignition by ArF laser flash-photolysis and nanosecond discharge in N2O-containing mixture has been done. Additional experiments have been made to assure that laser emission is distributed uniformly throughout the cross-section. The series of experiments was proposed and carried out to check validity of O(1D) determination in experiments on plasma assisted ignition initiated by flash-photolysis. In these experiments, ozone density in the given mixture (mixture composition and kinetics has been preliminary analyzed) was measured using UV light absorption in Hartley band. Good coincidence between experimental data and results of calculations have been obtained Temporal behavior of energy input, electric field and electric current has been measured and analyzed. These data are considered as initial conditions for numerical modeling of the discharge in O2:N2O:H2:Ar = 0.3:1:3:5 mixture. Ion-molecular reactions and reactions of active species production in Ar:H2:O2:N2O mixture were analyzed. The set of reactions to describe chemical transformation in the system due to the discharge action has been selected.

  14. Enhancement of wear and corrosion resistance of beta titanium alloy by laser gas alloying with nitrogen

    DEFF Research Database (Denmark)

    Chan, Chi-Wai; Lee, Seunghwan; Smith, Graham

    2016-01-01

    , the quaternary Ti-Nb-Zr-Ta (TNZT) alloys have received the highest attention as a promising replacement for Ti6Al4V due to their lower elastic modulus and outstanding long term stability against corrosion in biological environments. However, the inferior wear resistance of TNZT is still a problem that must......The relatively high elastic modulus coupled with the presence of toxic vanadium (V) in Ti6Al4V alloy has long been a concern in orthopaedic applications. To solve the problem, a variety of non-toxic and low modulus beta-titanium (beta-Ti) alloys have been developed. Among the beta-Ti alloy family...... be resolved before commercialising in the orthopaedic market. In this work, a newly developed laser surface treatment technique was employed to improve the surface properties of Ti-35.3Nb-7.3Zr-5.7Ta alloy. The surface structure and composition of the laser-treated TNZT surface were examined by grazing...

  15. Development Algorithm of the Technological Process of Manufacturing Gas Turbine Parts by Selective Laser Melting

    Science.gov (United States)

    Sotov, A. V.; Agapovichev, A. V.; Smelov, V. G.; Kyarimov, R. R.

    2018-01-01

    The technology of the selective laser melting (SLM) allows making products from powders of aluminum, titanium, heat-resistant alloys and stainless steels. Today the use of SLM technology develops at manufacture of the functional parts. This in turn requires development of a methodology projection of technological processes (TP) for manufacturing parts including databases of standard TP. Use of a technique will allow to exclude influence of technologist’s qualification on made products quality, and also to reduce labor input and energy consumption by development of TP due to use of the databases of standard TP integrated into a methodology. As approbation of the developed methodology the research of influence of the modes of a laser emission on a roughness of a surface of synthesized material was presented. It is established that the best values of a roughness of exemplars in the longitudinal and transversal directions make 1.98 μm and 3.59 μm respectively. These values of a roughness were received at specific density of energy 6.25 J/mm2 that corresponds to power and the speed of scanning of 200 W and 400 mm/s, respectively, and a hatch distance of 0.08 mm.

  16. Brome isotope selective control of CF3Br molecule clustering by IR laser radiation in gas-dynamic expansion of CF3Br - Ar mixture

    Science.gov (United States)

    Apatin, V. M.; Lokhman, V. N.; Makarov, G. N.; Ogurok, N.-D. D.; Ryabov, E. A.

    2018-02-01

    We report the results of research on the experimental control of CF3Br molecule clustering under gas-dynamic expansion of the CF3Br - Ar mixture at a nozzle exit by using IR laser radiation. A cw CO2 laser is used for exciting molecules and clusters in the beam and a time-of-flight mass-spectrometer with laser UV ionisation of particles for their detection. The parameters of the gas above the nozzle are determined (compositions and pressure) at which intensive molecule clustering occurs. It is found that in the case of the CF3Br gas without carrier when the pressure P0 above the nozzle does not exceed 4 atm, molecular clusters actually are not generated in the beam. If the gas mixture of CF3Br with argon is used at a pressure ratio 1 : N, where N >= 3, and the total pressure above the nozzle is P0 >= 2 atm, then there occurs molecule clustering. We study the dependences of the efficiency of suppressing the molecule clustering on parameters of the exciting pulse, gas parameters above the nozzle, and on a distance of the molecule irradiation zone from the nozzle exit section. It is shown that in the case of resonant vibrational excitation of gas-dynamically cooled CF3Br molecules at the nozzle exit one can realise isotope-selective suppression of molecule clustering with respect to bromine isotopes. With the CF3Br - Ar mixtures having the pressure ratio 1 : 3 and 1 : 15, the enrichment factors obtained with respect to bromine isotopes are kenr ≈ 1.05 ± 0.005 and kenr ≈ 1.06 ± 0.007, respectively, under jet irradiation by laser emission in the 9R(30) line (1084.635 cm-1). The results obtained let us assume that this method can be used to control clustering of molecules comprising heavy element isotopes, which have a small isotopic shift in IR absorption spectra.

  17. Physics and Chemistry of MW Laser-induced Discharge in Gas Flows and Plasma Jets

    Science.gov (United States)

    2007-12-01

    can be quasi-stationary coaxial plasma accelerators (MPC). This type of accelerators generates plasma jets of different gases (H2, He, N2, Ar) with...gas is ionizing and accelerating in discharge processing. For this regime the plasma gun generates the plasma jets of different gases3 (H2, He, N2...spectrometers. Spectrometers 1 and 2 are used for measuring of time behavior of single spectral lines, emitting in the focus area of plasma gun . Usually

  18. Comparative study of Nd:YAG laser-induced breakdown spectroscopy and transversely excited atmospheric CO2 laser-induced gas plasma spectroscopy on chromated copper arsenate preservative-treated wood.

    Science.gov (United States)

    Khumaeni, Ali; Lie, Zener Sukra; Niki, Hideaki; Lee, Yong Inn; Kurihara, Kazuyoshi; Wakasugi, Motoomi; Takahashi, Touru; Kagawa, Kiichiro

    2012-03-01

    Taking advantage of the specific characteristics of a transversely excited atmospheric (TEA) CO(2) laser, a sophisticated technique for the analysis of chromated copper arsenate (CCA) in wood samples has been developed. In this study, a CCA-treated wood sample with a dimension of 20 mm × 20 mm and a thickness of 2 mm was attached in contact to a nickel plate (20 mm × 20 mm × 0.15 mm), which functions as a subtarget. When the TEA CO(2) laser was successively irradiated onto the wood surface, a hole with a diameter of approximately 2.5 mm was produced inside the sample and the laser beam was directly impinged onto the metal subtarget. Strong and stable gas plasma with a very large diameter of approximately 10 mm was induced once the laser beam had directly struck the metal subtarget. This gas plasma then interacted with the fine particles of the sample inside the hole and finally the particles were effectively dissociated and excited in the gas plasma region. By using this technique, high precision and sensitive analysis of CCA-treated wood sample was realized. A linear calibration curve of Cr was successfully made using the CCA-treated wood sample. The detection limits of Cr, Cu, and As were estimated to be approximately 1, 2, and 15 mg/kg, respectively. In the case of standard LIBS using the Nd:YAG laser, the analytical intensities fluctuate and the detection limit was much lower at approximately one-tenth that of TEA CO(2) laser. © 2012 Optical Society of America

  19. Gas-dynamic perturbations in an electric-discharge repetitively pulsed DF laser and the role of He in their suppression

    Energy Technology Data Exchange (ETDEWEB)

    Evdokimov, P A; Sokolov, D V [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation)

    2015-11-30

    The gas-dynamic perturbations in a repetitively pulsed DF laser are studied using a Michelson interferometer. Based on the analysis of experimental data obtained in two experimental sets (working medium without buffer gas and with up to 90% of He), it is concluded that such phenomena as isentropic expansion of a thermal plug, gas heating by shock waves and resonance acoustic waves do not considerably decrease the upper limit of the pulse repetition rate below a value determined by the time of the thermal plug flush out of the discharge gap. It is suggested that this decrease for a DF laser with the SF{sub 6} – D{sub 2} working mixture is caused by the development of overheat instability due to an increased energy deposition into the near-electrode regions and to the formation of electrode shock waves. Addition of He to the active media of the DF laser changes the discharge structure and improves its homogeneity over the discharge gape cross section, thus eliminating the reason for the development of this instability. A signification dilution of the active medium of a DF laser with helium up to the atmospheric pressure allowed us to achieve the limiting discharge initiation frequencies with the active medium replacement ratio K ∼ 1. (active media)

  20. Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T. [Center for High Energy Density Science, Department of Physics, The University of Texas at Austin, C1510, Austin, Texas 78712 (United States)

    2013-12-15

    Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.

  1. Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas

    Science.gov (United States)

    Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T.

    2013-12-01

    Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.

  2. Displacement sensor based on intra-cavity tuning of dual-frequency gas laser

    Science.gov (United States)

    Niu, Haisha; Niu, Yanxiong; Liu, Ning; Li, Jiyang

    2018-01-01

    A nanometer-resolution displacement measurement instrument based on tunable cavity frequency-splitting method is presented. One beam is split into two orthogonally polarized beams when anisotropic element inserted in the cavity. The two beams with fixed frequency difference are modulated by the movement of the reflection mirror. The changing law of the power tuning curves between the total output and the two orthogonally polarized beams is researched, and a method splitting one tuning cycle to four equal parts is proposed based on the changing law, each part corresponds to one-eighth wavelength of displacement. A laser feedback interferometer (LFI) and piezoelectric ceramic are series connected to the sensor head to calibrate the displacement that less than one-eighth wavelength. The displacement sensor achieves to afford measurement range of 20mm with resolution of 6.93nm.

  3. Geometrical profile of material surface ablated with highpower, short-pulse lasers in ambient gas media

    Science.gov (United States)

    Vatsya, S. R.; Nikumb, S. K.

    2007-04-01

    Finer and cleaner features are expected in micro-machining with high power, ultrashort pulse lasers as the melt and evaporation phases are considerably reduced. However, a high-intensity optical beam propagating through a gaseous medium can cause its breakdown generating plasma, which is enhanced further by the self focusing effect of the medium. Photon-plasma scattering compensates somewhat for the self-focusing, but it also distorts the beam profile with consequent impact on the fabricated surface. Plasma also continues to supply heat beyond the pulse duration, which may cause melting and thus distort the features further. In the present article, we show that suitable parameters can be determined to reduce the distortion to the beam profile and balance self-focusing and plasma defocusing resulting in plasma filamentation. Well-shaped beam and plasma filaments, both have favourable impact on the fabricated features. The calculated surface features are compared with the experimentally machined crater profiles with good agreement.

  4. Multistage plasma initiation process by pulsed CO2 laser irradiation of a Ti sample in an ambient gas (He, Ar, or N2)

    Science.gov (United States)

    Hermann, J.; Boulmer-Leborgne, C.; Mihailescu, I. N.; Dubreuil, B.

    1993-02-01

    New experimental results are reported on plasma initiation in front of a titanium sample irradiated by ir (λ=10.6 μm) laser pulses in an ambient gas (He, Ar, and N2) at pressures ranging from several Torr up to the atmosphere. The plasma is studied by space- and time-resolved emission spectroscopy, while sample vaporization is probed by laser-induced fluorescence spectroscopy. Threshold laser intensities leading to the formation of a plasma in the vapor and in the ambient gases are determined. Experimental results support the model of a vaporization mechanism for the plasma initiation (vaporization-initiated plasma breakdown). The plasma initiation is described by simple numerical criteria based on a two-stage process. Theoretical predictions are found to be in a reasonable agreement with the experiment. This study provides also a clear explanation of the influence of the ambient gas on the laser beam-metal surface energy transfer. Laser irradiation always causes an important vaporization when performed in He, while in the case of Ar or N2, the interaction is reduced in heating and vaporization of some surface defects and impurities.

  5. Application of multi-way analysis to UV-visible spectroscopy, gas chromatography and electronic nose data for wine ageing evaluation.

    Science.gov (United States)

    Prieto, N; Rodriguez-Méndez, M L; Leardi, R; Oliveri, P; Hernando-Esquisabel, D; Iñiguez-Crespo, M; de Saja, J A

    2012-03-16

    In this study, a multi-way method (Tucker3) was applied to evaluate the performance of an electronic nose for following the ageing of red wines. The odour evaluation carried out with the electronic nose was combined with the quantitative analysis of volatile composition performed by GC-MS, and colour characterisation by UV-visible spectroscopy. Thanks to Tucker3, it was possible to understand connections among data obtained from these three different systems and to estimate the effect of different sources of variability on wine evaluation. In particular, the application of Tucker3 supplied a global visualisation of data structure, which was very informative to understand relationships between sensors responses and chemical composition of wines. The results obtained indicate that the analytical methods employed are useful tools to follow the wine ageing process, to differentiate wine samples according to ageing type (either in barrel or in stainless steel tanks with the addition of small oak wood pieces) and to the origin (French or American) of the oak wood. Finally, it was possible to designate the volatile compounds which play a major role in such a characterisation. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Fundamental science investigations to develop a 6-MV laser triggered gas switch for ZR: first annual report.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Van Den Avyle, James A.; Lehr, Jane Marie; Rose, David (Voss Scientific, Albuquerque, NM); Krompholz, Hermann G. (Texas Tech University, Lubbock, TX); Vela, Russell (Texas Tech University, Lubbock, TX); Jorgenson, Roy Eberhardt; Timoshkin, Igor (University of Strathclyde, Glasgow, Scotland); Woodworth, Joseph Ray; Prestwich, Kenneth Randel (Voss Scientific, Albuquerque, NM); Krile, John (Texas Tech University, Lubbock, TX); Given, Martin (University of Strathclyde, Glasgow, Scotland); McKee, G. Randall; Rosenthal, Stephen Edgar; Struve, Kenneth William; Welch, Dale Robert (Voss Scientific, Albuquerque, NM); Benwell, Andrew L. (University of Missouri-Columbia, Columbia, Missouri); Kovaleski, Scott (University of Missouri-Columbia, Columbia, Missouri); LeChien, Keith, R.; Johnson, David (Titan Pulse Sciences Division); Fouracre, R.A. (University of Strathclyde, Glasgow, Scotland); Yeckel, Chris (University of Missouri-Columbia, Columbia, Missouri); Wakeland, Peter Eric (Ktech Corporation, Albuquerque, NM); Miller, A. R. (Titan Pulse Sciences Division); Hodge, Keith Conquest (Ktech Corporation, Albuquerque, NM); Pasik, Michael Francis; Savage, Mark Edward; Maenchen, John Eric; Curry, Randy D. (University of Missouri-Columbia, Columbia, Missouri); Feltz, Greg (Ktech Corporation, Albuquerque, NM); Bliss, David Emery; MacGregor, Scott (University of Strathclyde, Glasgow, Scotland); Corley, J. P. (Ktech Corporation, Albuquerque, NM); Anaya, Victor (Ktech Corporation, Albuquerque, NM); Wallace, Zachariah (Ktech Corporation, Albuquerque, NM); Thoma, Carsten (Voss Scientific, Albuquerque, NM); Neuber, Andreas. (Texas Tech University, Lubbock, TX)

    2007-03-01

    In October 2005, an intensive three-year Laser Triggered Gas Switch (LTGS) development program was initiated to investigate and solve observed performance and reliability issues with the LTGS for ZR. The approach taken has been one of mission-focused research: to revisit and reassess the design, to establish a fundamental understanding of LTGS operation and failure modes, and to test evolving operational hypotheses. This effort is aimed toward deploying an initial switch for ZR in 2007, on supporting rolling upgrades to ZR as the technology can be developed, and to prepare with scientific understanding for the even higher voltage switches anticipated needed for future high-yield accelerators. The ZR LTGS was identified as a potential area of concern quite early, but since initial assessments performed on a simplified Switch Test Bed (STB) at 5 MV showed 300-shot lifetimes on multiple switch builds, this component was judged acceptable. When the Z{sub 20} engineering module was brought online in October 2003 frequent flashovers of the plastic switch envelope were observed at the increased stresses required to compensate for the programmatically increased ZR load inductance. As of October 2006, there have been 1423 Z{sub 20} shots assessing a variety of LTGS designs. Numerous incremental and fundamental switch design modifications have been investigated. As we continue to investigate the LTGS, the basic science of plastic surface tracking, laser triggering, cascade breakdown, and optics degradation remain high-priority mission-focused research topics. Significant progress has been made and, while the switch does not yet achieve design requirements, we are on the path to develop successively better switches for rolling upgrade improvements to ZR. This report summarizes the work performed in FY 2006 by the large team. A high-level summary is followed by detailed individual topical reports.

  7. Lasers: principles, applications and energetic measures; Lasers: principes, applications et mesures energetiques

    Energy Technology Data Exchange (ETDEWEB)

    Subran, C.; Sagaut, J. [Opton Laser International, 91 - Orsay (France); Lapointe, S. [Gentec Electro-Optique (Canada)

    2009-12-15

    After having recalled the principles of a laser and the properties of the laser beam, the authors describe the following different types of lasers: solid state lasers, fiber lasers, semiconductor lasers, dye lasers and gas lasers. Then, their applications are given. Very high energy lasers can reproduce the phenomenon of nuclear fusion of hydrogen atoms. (O.M.)

  8. Comprehensive study of solid pharmaceutical tablets in visible, near infrared (NIR), and longwave infrared (LWIR) spectral regions using a rapid simultaneous ultraviolet/visible/NIR (UVN) + LWIR laser-induced breakdown spectroscopy linear arrays detection system and a fast acousto-optic tunable filter NIR spectrometer.

    Science.gov (United States)

    Yang, Clayton S C; Jin, Feng; Swaminathan, Siva R; Patel, Sita; Ramer, Evan D; Trivedi, Sudhir B; Brown, Ei E; Hommerich, Uwe; Samuels, Alan C

    2017-10-30

    This is the first report of a simultaneous ultraviolet/visible/NIR and longwave infrared laser-induced breakdown spectroscopy (UVN + LWIR LIBS) measurement. In our attempt to study the feasibility of combining the newly developed rapid LWIR LIBS linear array detection system to existing rapid analytical techniques for a wide range of chemical analysis applications, two different solid pharmaceutical tablets, Tylenol arthritis pain and Bufferin, were studied using both a recently designed simultaneous UVN + LWIR LIBS detection system and a fast AOTF NIR (1200 to 2200 nm) spectrometer. Every simultaneous UVN + LWIR LIBS emission spectrum in this work was initiated by one single laser pulse-induced micro-plasma in the ambient air atmosphere. Distinct atomic and molecular LIBS emission signatures of the target compounds measured simultaneously in UVN (200 to 1100 nm) and LWIR (5.6 to 10 µm) spectral regions are readily detected and identified without the need to employ complex data processing. In depth profiling studies of these two pharmaceutical tablets without any sample preparation, one can easily monitor the transition of the dominant LWIR emission signatures from coating ingredients gradually to the pharmaceutical ingredients underneath the coating. The observed LWIR LIBS emission signatures provide complementary molecular information to the UVN LIBS signatures, thus adding robustness to identification procedures. LIBS techniques are more surface specific while NIR spectroscopy has the capability to probe more bulk materials with its greater penetration depth. Both UVN + LWIR LIBS and NIR absorption spectroscopy have shown the capabilities of acquiring useful target analyte spectral signatures in comparable short time scales. The addition of a rapid LWIR spectroscopic probe to these widely used optical analytical methods, such as NIR spectroscopy and UVN LIBS, may greatly enhance the capability and accuracy of the combined system for a comprehensive analysis.

  9. Laser Scanning and Modelling of Barely Visible Features: the Survey of the Grotto of the Animals at the Villa of Castello (florence)

    Science.gov (United States)

    Tesi, V.; Tucci, G.; Bonora, V.; Fiorini, L.; Conti, A.

    2017-05-01

    The deep fusion of natural and artificial elements typical of Italian Renaissance gardens is particularly evident in the park of Villa di Castello and in the Grotto of the Animals, also called Grotto of the Flood. The soil slope is the essential element of a huge underlying hydraulic machine and it is the result of extensive earthworks which led to the construction of the big retaining wall limiting the grotto and the adjacent fountains. Hence, this grotto represents only the visible part of a mechanism running all around it. It is formed by a single chamber vaulted and covered with sponge-like stones, as well as decorations made of pebbles and shells. The space is divided into three wings, with big marble basins at their end. Over them there are reliefs of animals made of different stones and marbles. Animals recur also in the compositions of fish and shellfish decorating the side basins and in the bronze birds currently kept in the Museo del Bargello. The name "Grotto of the Flood" comes from the water feature that characterised this place: visitors were surprised by tens of jets hidden among the stones in the vault and in the floor. To obtain this effect, the whole grotto is surrounded by multi-storey tunnels, hiding the hydraulic system and people activating the mechanisms. Research agreements were drawn up between the Special Superintendence for the Historical, Artistic and Ethnoanthropological Heritage, the Florence museums group and the GeCO Lab, for the realization of the survey presented in this paper. The task of the GeCO Lab was thus identifying the best solutions to check the spatial relations between the grotto and the area above, as well as the geometric and functional connections between the building and the ancient hydraulic system, composed by pipes and nozzles concealed between the stones. Besides, the overall survey was intended as a documentation of the on-going restoration work.

  10. Micromanufacturing in Fused Silica via Femtosecond Laser Irradiation Followed by Gas-Phase Chemical Etching

    Directory of Open Access Journals (Sweden)

    Walter Navarrini

    2012-09-01

    Full Text Available Femtosecond laser irradiation followed by chemical etching (FLICE with hydrogen fluoride (HF is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure, as described in literature, consists of irradiating a silica slab followed by chemical etching using hydrogen fluoride. With aqueous HF the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of about 1.5 mm, while the use of low-pressure gaseous HF etchant can quickly produce 3 mm long channels with an aspect ratio (Length/Diameter higher than 25. By utilizing this methodology the aspect ratio is not constant, but depends on the length of the channel. When the microchannel is short the aspect ratio increases quickly until it reaches a maximum length at around 1400 µm. Thereafter the aspect ratio starts to decrease slowly. In this paper we present a variation of the low-pressure gaseous HF etching method, which is based on the dynamic displacement of the etchant. This method results in a 13% increase in the aspect ratio (L/D = 29 at the expense of a low etching speed (4 µm/min.

  11. Active Stand-off Detection of Gas Leaks Using a Short Range Hard-target Backscatter Differential Optical Absorption System Based on a Quantum Cascade Laser Transmitter

    Directory of Open Access Journals (Sweden)

    Diaz Adrian

    2016-01-01

    Full Text Available Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they can contribute to the global increase of greenhouse gas concentration. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents gas concentration measurements using a quantum cascade laser open path system (QCLOPS. The system retrieves the pathaveraged concentration of N2O and CH4 by collecting the backscattered light from a scattering target. The gas concentration measurements have a high temporal resolution (68 ms and are achieved at sufficient range (up to 40 m, ~ 130 feet with a detection limit of 2.6 ppm CH4 and 0.4 ppm for N2O. Given these characteristics, this system is promising for mobile/multidirectional remote detection and evaluation of gas leaks. The instrument is monostatic with a tunable QCL emitting at ~ 7.7 μm wavelength range. The backscattered radiation is collected by a Newtonian telescope and focused on an infrared light detector. Puffs of N2O and CH4 are released along the optical path to simulate a gas leak. The measured absorption spectrum is obtained using the thermal intra-pulse frequency chirped DFB QCL and is analyzed to obtain path averaged gas concentrations.

  12. Composition and crystalline properties of TiNi thin films prepared by pulsed laser deposition under vacuum and in ambient Ar gas.

    Science.gov (United States)

    Cha, Jeong Ok; Nam, Tae Hyun; Alghusun, Mohammad; Ahn, Jeung Sun

    2012-01-05

    TiNi shape memory alloy thin films were deposited using the pulsed laser deposition under vacuum and in an ambient Ar gas. Our main purpose is to investigate the influences of ambient Ar gas on the composition and the crystallization temperature of TiNi thin films. The deposited films were characterized by energy-dispersive X-ray spectrometry, a surface profiler, and X-ray diffraction at room temperature. In the case of TiNi thin films deposited in an ambient Ar gas, the compositions of the films were found to be very close to the composition of target when the substrate was placed at the shock front. The in-situ crystallization temperature (ca. 400°C) of the TiNi film prepared at the shock front in an ambient Ar gas was found to be lowered by ca. 100°C in comparison with that of a TiNi film prepared under vacuum.

  13. Nanosecond Nd-YAG laser induced plasma emission characteristics in low pressure CO{sub 2} ambient gas for spectrochemical application on Mars

    Energy Technology Data Exchange (ETDEWEB)

    Lie, Zener Sukra; Kurniawan, Koo Hendrik, E-mail: kurnia18@cbn.net.id [Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Pardede, Marincan [Department of Electrical Engineering, University of Pelita Harapan, 1100 M.H. Thamrin Boulevard, Lippo Village, Tangerang 15811 (Indonesia); Tjia, May On [Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Physics of Magnetism and Photonics Group, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia); Kagawa, Kiichiro [Fukui Science Education Academy, Takagi Chuou 2 choume, Fukui 910-0804 (Japan); Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia)

    2015-08-28

    An experimental study is conducted on the possibility and viability of performing spectrochemical analysis of carbon and other elements in trace amount in Mars, in particular, the clean detection of C, which is indispensible for tracking the sign of life in Mars. For this study, a nanosecond Nd-YAG laser is employed to generate plasma emission from a pure copper target in CO{sub 2} ambient gas of reduced pressure simulating the atmospheric condition of Mars. It is shown that the same shock wave excitation mechanism also works this case while exhibiting remarkably long cooling stage. The highest Cu emission intensities induced by 4 mJ laser ablation energy is attained in 600 Pa CO{sub 2} ambient gas. Meanwhile the considerably weaker carbon emission from the CO{sub 2} gas appears relatively featureless over the entire range of pressure variation, posing a serious problem for sensitive trace analysis of C contained in a solid sample. Our time resolved intensity measurement nevertheless reveals earlier appearance of C emission from the CO{sub 2} gas with a limited duration from 50 ns to 400 ns after the laser irradiation, well before the initial appearance of the long lasting C emission from the solid target at about 1 μs, due to the different C-releasing processes from their different host materials. The unwanted C emission from the ambient gas can thus be eliminated from the detected spectrum by a proper time gated detection window. The excellent spectra of carbon, aluminum, calcium, sodium, hydrogen, and oxygen obtained from an agate sample are presented to further demonstrate and verify merit of this special time gated LIBS using CO{sub 2} ambient gas and suggesting its viability for broad ranging in-situ applications in Mars.

  14. UV-laser-light-controlled photoluminescence of metal oxide nanoparticles in different gas atmospheres: BaTiO3, SrTiO3 and HfO2

    International Nuclear Information System (INIS)

    Mochizuki, Shosuke; Saito, Takashi; Yoshida, Kaori

    2012-01-01

    The photoluminescence (PL) enhancement has been studied at room temperature using various specimen atmospheres (O 2 gas, CO 2 gas, CO 2 -H 2 mixture gas, Ar-H 2 mixture gas and vacuum) under 325 nm laser light irradiation on various metal oxides. Of them, the results obtained for BaTiO 3 nanocrystals, SrTiO 3 ones and HfO 2 powder crystal are given in the present paper. Their PL were considerably increased in intensity by irradiation of 325 nm laser light in CO 2 gas and CO 2 -H 2 mixture gas. The cause of the PL intensity enhancements is discussed in the light of the exciton theory, the defect chemistry and the photocatalytic theory. The results may be applied for the utilization of greenhouse gas (CO 2 ) and the optical sensor for CO 2 gas.

  15. Estudo experimental da aplicação retiniana do laser infravermelho via transescleral sob condições de baixa visibilidade Transscleral infrared laser retinal photocoagulation experimental study under low visibility conditions

    Directory of Open Access Journals (Sweden)

    Dario Grechi Goulart

    2008-06-01

    Full Text Available OBJETIVOS: Pesquisa experimental, com laser de diodo infravermelho, para estimar a segurança, a reprodutibilidade e a permeabilidade da parede ocular à sua atuação clínica, quando aplicado via transescleral, em condições de baixa visibilidade. MÉTODOS: Submetemos olhos de coelhos pigmentados da raça Nova Zelândia à fotocoagulação retiniana por laser de diodo infravermelho. No olho direito, realizamos fotocoagulação via transescleral sob parâmetros de potência e tempo pré-determinados clinicamente. No olho esquerdo, foram repetidos os mesmos valores da potência e tempo usados no olho direito, desta vez, via transpupilar. Imediatamente e após 2 meses, estudos clínicos baseados na retinografia e histopatológicos foram realizados. RESULTADOS: A permeabilidade da parede ocular, quando da aplicação do laser de diodo infravermelho via transescleral, variou entre 58,95 e 63,87%. A média da permeabilidade da parede ocular a 300 mW (63,14% mostrou-se significativamente superior àquela da permeabilidade da parede ocular encontrada a 500 mW (59,11%, (PPURPOSE: Retinal photocoagulation under poor visualization condition is often required. Transscleral infrared laser can be used as an alternative to regular transpupillary treatment. Based upon retinographic measurements, we proposed to estimate the reproducibility as well as ocular wall permeability rate for this treatment. Our primary goal was to evaluate whether this technique can deliver adequate photocoagulation at predetermined parameters without direct retinal visualization. METHODS: In New Zealand pigmented rabbits, optimal transscleral infrared diode laser settings were administered to the right eye. With the same parameters, transpupillary photocoagulation was repeated in the left eye. Retinographic and clinical examinations were performed immediately and two months later. RESULTS: Ocular wall permeability rate varied between 58.95 and 63.87%. Average permeability using a

  16. High-brightness laser plasma soft X-ray source using a double-stream gas puff target irradiated with th Prague Asterix Laser System (PALS)

    Czech Academy of Sciences Publication Activity Database

    Fiedorowicz, H.; Bartnik, A.; Juha, Libor; Jungwirth, Karel; Králiková, Božena; Krása, Josef; Kubát, Pavel; Pfeifer, Miroslav; Pina, D.; Prchal, Pavel; Rohlena, Karel; Skála, Jiří; Ullschmied, Jiří; Horvath, M.; Wawer, J.

    2004-01-01

    Roč. 362, - (2004), s. 67-70 ISSN 0925-8388 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z4040901 Keywords : X-ray spectroscopy * laser processing Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.562, year: 2004

  17. Mw Spectroscopy Coupled with Ultrafast UV Laser Vaporization: {RIBOSE} Found in the Gas Phase

    Science.gov (United States)

    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.

  18. Advanced coupling of nuclear reactor-gas laser systems. Technical progress report, August 31, 1974--August 31, 1975

    International Nuclear Information System (INIS)

    Verdeyen, J.T.; Miley, G.H.; Wells, W.E.

    1975-01-01

    Research progress on the development of direct nuclear pumped (DNP) lasers is reported. Most of the work was on a Ne--N 2 DNP laser. Some work is reported on He--Ne--O 2 , He--Hg, and the chemical lasers BF 3 --CH 4 and SF 6 --CH 4 . (U.S.)

  19. Characterization of SrTiO3 target doped with Co ions, SrCoxTi1-xO3-δ, and their thin films prepared by pulsed laser ablation (PLA) in water for visible light response

    Science.gov (United States)

    Ichihara, Fumihiko; Murata, Yuma; Ono, Hiroshi; Choo, Cheow-keong; Tanaka, Katsumi

    2017-10-01

    SrTiO3 (STO) and Co-doped SrTiO3 (Co-STO) sintered targets were synthesized and were Ar+ sputtered to elucidate the charge compensation effect between Sr, Ti and Co cations following the reduction by oxygen desorption. Following exposure of the Ar+-sputtered target to the air, charge transfer reactions occurred among Co2+, Ti3+, O2- and Sr2+ species which were studied by their XPS spectra. Pulsed laser ablation (PLA) of these targets was carried out in water to prepare the nanoparticles which could be supplied to the thin films with much higher surface reactivity expected for photocatalytic reactions. The roles of Co ions were studied for the stoichiometry and crystallinity of the nanoparticles which constituted the thin films. Photo-degradation of methylene blue was carried out on the PLA thin films under very weak visible light at 460 nm. The PLA thin films showed the photocatalytic activities, which were enhanced by the presence of Co ions. Such the effect of Co ions was considered from viewpoint of the d-d transition and the charge-transfer between Co ions and the ligand oxygen.

  20. Detection of ethylene gas in exhaled breath of people living in landfill using CO{sub 2} laser photoacoustic spectroscopy with multicomponent analysis

    Energy Technology Data Exchange (ETDEWEB)

    Oktafiani, Fitri, E-mail: fitri.oktafiani@mail.ugm.ac.id; Stiyabudi, Rizky; Amin, Mochamad Nurul; Mitrayana [Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara BLS 21, Yogyakarta, 55281 Indonesia (Indonesia)

    2016-06-17

    The photoacoustic spectrometer (PAS) had been built and the performance had been determined. The research was based on the conversion of the absorbed middle infra red (IR) radiation by gas confined in a closed PAS cell into standing acoustic wave, which could be detected by a suitable electroacoustic transducer such as a microphone. The lowest detection limit for this setup was (57,1 ± 0,3) ppb and quality factor was (14,5 ± 0,6) for ethylene gas in 10P14 CO{sub 2} laser line. Then, this PAS was used to measure of ethylene gas concentration in breath sample of people living in near the Piyungan Bantul Yogyakarta landfill. The result from multicomponent analysis showed that PAS enable to measure the lowest concentration of volatile organic compound (VOC), such as ethylene, which occured on ambien air in Piyungan landfill. Variaty of distance area applied in this research. In the range of ±0,5 km from landfill, we obtained the concentration of ethylene gas concentration for human breath was (1,520 ± 0,002) ppm, while in the range of ±45 km, the ethylene gas concentration for human breath was (0,424 ± 0,002) ppm. Ethylene gas concentrations in exhaled gas decreased along with increasing distance variation of the landfill.

  1. Ozone air pollution effects on tree-ring growth,{delta}{sup 13}C, visible foliar injury and leaf gas exchange in three ozone-sensitive woody plant species

    Energy Technology Data Exchange (ETDEWEB)

    Novak, K. [Swiss Federal Inst. for Forest, Snow and Landscape Research, Birmensdorf (Switzerland); Agroscope FAL Reckenholz, Swiss Federal Research Station for Agroecology and Agriculture, Zurich (Switzerland); Saurer, M. [Paul Scherrer Inst. Villigen (Switzerland); Fuhrer, J. [Agroscope FAL Reckenholz, Swiss Federal Research Station for Agroecology and Agriculture, Zurich (Switzerland); Skelly, J.M. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Plant Pathology; Krauchi, N.; Schaub, M. [Swiss Federal Inst. for Forest, Snow and Landscape Research, Birmensdorf (Switzerland)

    2007-07-15

    Species specific plant responses to tropospheric ozone pollution depend on a range of morphological, biochemical and physiological characteristics as well as environmental factors. The effects of ambient tropospheric ozone on annual tree-ring growth, {delta}{sup 13} C in the rings, leaf gas exchange and ozone-induced visible foliar injury in three ozone-sensitive woody plant species in southern Switzerland were assessed during the 2001 and 2002 growing seasons. Seedlings of Populus nigra L., Viburnum lantana L. and Fraxinus excelsior L. were exposed to charcoal-filtered air and non-filtered air in open-top chambers, and to ambient air (AA) in open plots. The objective was to determine if a relationship exists between measurable ozone-induced effects at the leaf level and subsequent changes in annual tree-ring growth and {delta} {sup 13} C signatures. The visible foliar injury, early leaf senescence and premature leaf loss in all species was attributed to the ambient ozone exposures in the region. Ozone had pronounced negative effects on net photosynthesis and stomatal conductance in all species in 2002 and in V. lantana and F. excelsior in 2001. Water-use efficiency decreased and intercellular carbon dioxide concentrations increased in all species in response to ozone in 2002 only. The width and {delta}{sup 13} C of the 2001 and 2002 growth rings were measured for all species at the end of the 2002 growing season. Significant ozone-induced effects at the leaf level did not correspond to reduced tree-ring growth or increased {delta}{sup 13} C in all species, suggesting that the timing of ozone exposure and extent of leaf-level responses may be relevant in determining the sensitivity of tree productivity to ozone exposure. 48 refs., 4 tabs., 2 figs.

  2. excimer laser

    Indian Academy of Sciences (India)

    2014-01-07

    Jan 7, 2014 ... is necessary to deposit one order higher input electric power into gas medium than those required for XeCl and KrF lasers. ... neon/helium at a pressure of a few bars was excited by transverse electric discharge. The. Figure 6. Laser pulse ... and also to drive discharge rapidly. The discharge chamber was ...

  3. Narrow energy spread, 25MeV protons from the interaction of a time-structured CO2 laser pulse with a gas target

    Science.gov (United States)

    Haberberger, D.; Tochitsky, S.; Gong, C.; Pak, A.; Marsh, K. A.; Joshi, C.; Tsung, F.; Mori, W.; Fiuza, F.; Fonseca, R.; Silva, L.

    2010-11-01

    Experimental results and 2D OSIRIS simulations of laser-driven proton acceleration from the interaction of a time-structured 10μm CO2 laser pulse train and a gaseous target are presented. The wavelength of a CO2 laser provides a unique opportunity to change the target density from 0.5 to 5ncr in a controlled manner by changing the H2 gas jet pressure. The CO2 laser pulses consist of a train of 3ps pulses separated by 18ps with a peak power of ˜4TW and a total energy of ˜50J. The initial results show the production of proton energies of up to 25MeV, which far exceeds that predicted by ponderomotive force scaling for an ao˜2. Furthermore, in the density range around 2ncr, these high energy protons are contained within a narrow energy spread of δE/E ˜ 10%. These results are attributed to the unique time structure of the CO2 laser pulses, underdense LPI's such as self-focusing due to large P/Pcr values, and profile steepening/hole boring.

  4. Visibly Pushdown Automata

    DEFF Research Database (Denmark)

    Srba, Jiri

    2006-01-01

    We investigate the possibility of (bi)simulation-like preorder/equivalence checking on the class of visibly pushdown automata and its natural subclasses visibly BPA (Basic Process Algebra) and visibly one-counter automata. We describe generic methods for proving complexity upper and lower bounds...... for a number of studied preorders and equivalences like simulation, completed simulation, ready simulation, 2-nested simulation preorders/equivalences and bisimulation equivalence. Our main results are that all the mentioned equivalences and preorders are EXPTIME-complete on visibly pushdown automata, PSPACE......-complete on visibly one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for visibly one-counter automata improves also the previously known DP-hardness results for ordinary one-counter automata and one-counter nets. Finally, we study regularity checking problems for visibly pushdown automata...

  5. High-Speed Multiplexed Spatiotemporally Resolved Measurements of Exhaust Gas Recirculation Dynamics in a Multi-Cylinder Engine Using Laser Absorption Spectroscopy.

    Science.gov (United States)

    Yoo, Jihyung; Prikhodko, Vitaly; Parks, James E; Perfetto, Anthony; Geckler, Sam; Partridge, William P

    2016-04-01

    The need for more environmentally friendly and efficient energy conversion is of paramount importance in developing and designing next-generation internal combustion (IC) engines for transportation applications. One effective solution to reducing emissions of mono-nitrogen oxides (NOx) is exhaust gas recirculation (EGR), which has been widely implemented in modern vehicles. However, cylinder-to-cylinder and cycle-to-cycle variations in the charge-gas uniformity can be a major barrier to optimum EGR implementation on multi-cylinder engines, and can limit performance, stability, and efficiency. Precise knowledge and fine control over the EGR system is therefore crucial, particularly for optimizing advanced engine concepts such as reactivity controlled compression ignition (RCCI). An absorption-based laser diagnostic was developed to study spatiotemporal charge-gas distributions in an IC engine intake manifold in real-time. The laser was tuned to an absorption band of carbon dioxide (CO2), a standard exhaust-gas marker, near 2.7 µm. The sensor was capable of probing four separate measurement locations simultaneously, and independently analyzing EGR fraction at speeds of 5 kHz (1.2 crank-angle degree (CAD) at 1 k RPM) or faster with high accuracy. The probes were used to study spatiotemporal EGR non-uniformities in the intake manifold and ultimately promote the development of more efficient and higher performance engines. © The Author(s) 2016.

  6. Optical properties of crystals doped with Sm3+ or Dy3+ relevant to potential InGaN/GaN laser diode-pumped visible laser operation: A comparative study

    Science.gov (United States)

    Ryba-Romanowski, W.; Strzęp, A.; Lisiecki, R.; Berkowski, M.

    2014-05-01

    Results of detailed spectroscopic investigation of Sm3+ and Dy3+ ions incorporated in crystal structures of Yal YAl3(BO3)4, LiNbO3, Gd3Ga5O12, Gd2SiO5, Lu2SiO5 and (Gd, Lu)2SiO5 are reported and discussed. The impact of the hosts on transition intensities and excited state relaxation dynamics of incorporated luminescent ions was examined. Distribution of luminescence intensity among spectral bands in terms of luminescence branching ratios was evaluated based on numerical integration of luminescence bands. Intensities of UV and blue absorption bands potentially useful for optical pumping were determined quantitatively in units of absorption cross section. The most intense luminescence bands related to potential laser transitions 4 G 5/2 → 6 H 7/2 of Sm3+ around 600 nm and 4 F 9/2 → 6 H 13/2 of Dy3+ around 580 nm were calibrated in units of emission cross section. Evaluated peak values of emission cross section range from 0.43 × 10-20 cm2 for Sm3+ in (Gd, Lu)2SiO5 to 1.17 × 10-20 cm2 for Sm3+ in LiNbO3. Those for dysprosium-doped crystals range from 0.63 × 10-20 cm2 for LiNbO3:Dy3+ to 2.0 × 10-20 cm2 for Yal YAl3(BO3)4:Dy3+. It follows from these considerations that samarium-doped crystals show promise for laser application owing to the combination of a strong absorption that matches radiation of commercial laser diodes emitting near 405 nm and long luminescence lifetime. Major shortcoming of dysprosium-doped crystals results from a weak intensity of absorption bands available for optical pumping near 450 nm and 385 nm combined with relatively strong self-quenching of luminescence.

  7. The Visibility Complex

    NARCIS (Netherlands)

    Pocchiola, Michel; Vegter, Gert

    1993-01-01

    We introduce the visibility complex of a collection O of n pairwise disjoint convex objects in the plane. This 2–dimensional cell complex may be considered as a generalization of the tangent visibility graph of O. Its space complexity k is proportional to the size of the tangent visibility graph. We

  8. Necessary conditions for the homogeneous formation of a volume avalanche discharge with specific applications to rare gas-halide excimer laser discharges

    International Nuclear Information System (INIS)

    Levatter, J.I.

    1979-01-01

    Self-sustained/avalanche discharges are an efficient method of rare gas-halide excimer laser excitation in small systems. However, with the exceptions of the work reported here, experiments attempting to increase the laser energy output by scaling up the discharge volume and/or pulse duration have not been successful. The major problem encountered in scaling experiments has been the formation of arc channels in the discharge volume. The presence of arcing can totally disrupt proper laser operation. This problem stems from a general lack of understanding of high pressure avalanche discharge phenomena. Therefore, clarifying the basic discharge formation process and establishing a set of criteria under which a homogeneous avalanche discharge can be obtained is of central importance in defining the scaling limits of avalanche discharge lasers. The work presented here reviews the phenomena involved in high E/n (electric field to gas number density ratio) breakdown and its relationship to the formation of spatially homogeneous discharges. This relationship was first explored by A.J. Palmer in 1974. The basic requirement of his model was that the preionization density be large enough to cause an appreciable overlap of the primary electron avalanches and hence smooth out the ensuing space-charge fields to the extent that individual streamer formation would be prevented. This is the same basic model used in the more detailed discharge formation analysis developed here except that the effects of a time varying electric field caused by a finite voltage rise time and the effects due to the various electrochemical properties of the gas mixture are property taken into consideration

  9. Scaling up and controlling beam quality of flowing-gas diode pumped potassium laser with different pumping geometries: 3D CFD modeling

    Science.gov (United States)

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

    2017-10-01

    Comprehensive analysis of the performance and beam quality of subsonic flowing-gas K diode-pumped alkali lasers (DPALs) with different pumping geometries, using 3D computational fluid dynamics model, is reported. The model is first applied to a K DPAL with transverse pumping and parameters similar to those of the 1.5 kW K DPAL [Pitz et al, Proc. SPIE 9729, 972902 (2016)] and the calculated results are in satisfactory agreement with the measurements. To study the possibility of scaling up the K DPAL the model is then applied to 100-kW class device with transverse and end pumping geometry. Dependence of the output power on the flow velocity and the pumping geometry is studied. Comparison between end and transverse pumping schemes shows that the output power is almost unaffected by the pumping geometry. However, the spatial intensity distribution of the output laser beam depends on the pumping geometry: it is uniform for the end pumping, whereas for the transverse pumping it is strongly non-uniform at high gas temperature (corresponding to large density of K atoms), becoming more uniform with temperature reduction. The model is applied to evaluation of the beam quality of flowing-gas K DPALs which strongly depends on the refractive index distribution in the gain medium. The beam divergence and the width of the intensity profile in the far field for the end pumping appear to be much smaller than for the transverse pumping. Wave front corrections of the transversely pumped device using cylindrical lens results in substantial reduction of the laser beam divergence and improvement of its quality which becomes comparable with that of the end pumped laser.

  10. He, U, and Th Depth Profiling of Apatite and Zircon Using Laser Ablation Noble Gas Mass Spectrometry and SIMS

    Science.gov (United States)

    Monteleone, B. D.; van Soest, M. C.; Hodges, K. V.; Hervig, R.; Boyce, J. W.

    2008-12-01

    Conventional (U-Th)/He thermochronology utilizes single or multiple grain analyses of U- and Th-bearing minerals such as apatite and zircon and does not allow for assessment of spatial variation in concentration of He, U, or Th within individual crystals. As such, age calculation and interpretation require assumptions regarding 4He loss through alpha ejection, diffusive redistribution of 4He, and U and Th distribution as an initial condition for these processes. Although models have been developed to predict 4He diffusion parameters, correct for the effect of alpha ejection on calculated cooling ages, and account for the effect of U and Th zonation within apatite and zircon, measurements of 4He, U, and Th distribution have not been combined within a single crystal. We apply ArF excimer laser ablation, combined with noble gas mass spectrometry, to obtain depth profiles within apatite and zircon crystals in order to assess variations in 4He concentration with depth. Our initial results from pre-cut, pre-heated slabs of Durango apatite, each subjected to different T-t schedules, suggest a general agreement of 4He profiles with those predicted by theoretical diffusion models (Farley, 2000). Depth profiles through unpolished grains give reproducible alpha ejection profiles in Durango apatite that deviate from alpha ejection profiles predicted for ideal, homogenous crystals. SIMS depth profiling utilizes an O2 primary beam capable of sputtering tens of microns and measuring sub-micron resolution variation in [U], [Th], and [Sm]. Preliminary results suggest that sufficient [U] and [Th] zonation is present in Durango apatite to influence the form of the 4He alpha ejection profile. Future work will assess the influence of measured [U] and [Th] zonation on previously measured 4He depth profiles. Farley, K.A., 2000. Helium diffusion from apatite; general behavior as illustrated by Durango fluorapatite. J. Geophys. Res., B Solid Earth Planets 105 (2), 2903-2914.

  11. Low Power Consumption Lasers for Next Generation Miniature Optical Spectrometers for Major Constituent and Trace Gas Analysis

    Science.gov (United States)

    Forouhar, Siamak; Soibel, Alexander; Frez, Clifford; Qiu, Yueming; Chen, J.; Hosoda, T.; Kipshidze, G.; Shterengas, L.; Tsvid, G.; Belenky, G.; hide

    2010-01-01

    The air quality of any manned spacecraft needs to be continuously monitored in order to safeguard the health of the crew. Air quality monitoring grows in importance as mission duration increases. Due to the small size, low power draw, and performance reliability, semiconductor laser-based instruments are viable candidates for this purpose. The minimum instrument size requires lasers with emission wavelength coinciding with the absorption of the fundamental frequency of the target gases which are mostly in the 3.0-5.0 micrometers wavelength range. In this paper we report on our progress developing high wall plug efficiency type-I quantum-well GaSb-based diode lasers operating at room temperatures in the spectral region near 3.0-3.5 micrometers and quantum cascade (QC) lasers in the 4.0-5.0 micrometers range. These lasers will enable the development of miniature, low-power laser spectrometers for environmental monitoring of the spacecraft.

  12. Comparative study of energy of particles ejected from coulomb explosion of rare gas and metallic clusters irradiated by intense femtosecond laser field

    Science.gov (United States)

    Boucerredj, N.; Beggas, K.

    2016-10-01

    We present our study of high intensity femtosecond laser field interaction with large cluster of Kr and Na (contained 2.103 to 2.107 atoms). When laser intensity is above a critical value, it blows off all of electrons from the cluster and forms a non neutral ion cloud. The irradiation of these clusters by the intense laser field leads to highly excitation energy which can be the source of energetic electrons, electronic emission, highly charge, energetic ions and fragmentation process. During the Coulomb explosion of the resulting highly ionized, high temperature nanoplasma, ions acquire again their energy. It is shown that ultra fast ions are produced. The goal of our study is to investigate in detail a comparative study of the expansion and explosion then the ion energy of metallic and rare gas clusters irradiated by an intense femtosecond laser field. We have found that ions have a kinetic energy up to 105 eV and the Coulomb pressure is little than the hydrodynamic pressure. The Coulomb explosion of a cluster may provide a new high energy ion source.

  13. Phase control of a Zeeman-split He-Ne gas laser by variation of the gaseous discharge voltage.

    Science.gov (United States)

    Shelton, W N; Hunt, R H

    1992-07-20

    Zeeman-split lasers are useful for precise positioning or motion control. In applications that employ such a laser to control closely the position of a moving system, phase noise in the Zeeman frequency is a serious problem. Control of low-frequency phase noise can be obtained through variation of the external magnetic field by way of a solenoid wound around the laser tube. It is the finding in this work that control of the residual higher-frequency noise of a He-Ne laser can be obtained through small variations of the high voltage that is used to effect the gaseous discharge in the laser tube. The application of the present system is to the control of the path difference in a Fourier-transform interferometric spectrometer.

  14. Measurement of the development and evolution of shock waves in a laser-induced gas breakdown plasma

    International Nuclear Information System (INIS)

    Chu, T.K.; Johnson, L.C.

    1974-12-01

    Space- and time-resolved interferometric measurements of electron density in CO 2 -laser produced plasmas in helium or hydrogen are made near the laser focal spot. Immediately after breakdown, a rapidly growing region of approximately uniform plasma density appears at the focal spot. After a few tens of nanoseconds, shock waves are formed, propagating both transverse and parallel to the incident laser beam direction. Behind the transverse propagating shock is an on-axis density minimum, which results in laser-beam self trapping. The shock wave propagating toward the focusing lens effectively shields the interior plasma from the incident beam, because the lower plasma temperature and higher plasma density in the shock allow strong absorption of the incident beam energy. By arranging the laser radiation-plasma interaction to begin at a plasma vacuum interface at the exit of a free-expansion jet, this backward propagating shock wave is eliminated, thus permitting efficient energy deposition in the plasma interior. (auth)

  15. Infrared laser system

    Science.gov (United States)

    Cantrell, Cyrus D.; Carbone, Robert J.; Cooper, Ralph S.

    1977-01-01

    An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture.

  16. Infrared laser system

    International Nuclear Information System (INIS)

    Cantrell, C.D.; Carbone, R.J.

    1977-01-01

    An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture

  17. Excimer laser applications

    International Nuclear Information System (INIS)

    Fantoni, R.

    1988-01-01

    This lecture deals with laser induced material photoprocessing, especially concerning those processes which are initiated by u.v. lasers (mostly excimer laser). Advantages of using the u.v. radiation emitted by excimer lasers, both in photophysical and photochemical processes of different materials, are discussed in detail. Applications concerning microelectronics are stressed with respect to other applications in different fields (organic chemistry, medicine). As further applications of excimer lasers, main spectroscopic techniques for ''on line'' diagnostics which employ excimer pumped dye lasers, emitting tunable radiation in the visible and near u.v. are reviewed

  18. 6.1-MV, 0.79-MA laser-triggered gas switch for multimodule, multiterawatt pulsed-power accelerators

    Directory of Open Access Journals (Sweden)

    K. R. LeChien

    2010-03-01

    Full Text Available A 6.1-MV, 0.79-MA laser-triggered gas switch (LTGS is used to synchronize the 36 modules of the Z machine at Sandia National Laboratories. Each module includes one switch, which serves as the last command-fired switch of the module, and hence is used to determine the time at which each module electrically closes relative to the other modules. The switch is ∼81-cm in length, ∼45-cm in diameter, and is immersed in mineral oil. The outer switch envelope consists of six corrugated monomer-cast acrylic insulators and five contoured stainless-steel rings. The trigger electrodes are fabricated from copper-infused tungsten. The switch is pressurized with several atmospheres of sulfur hexafluoride (SF_{6}, which is turbulently purged within 2 seconds after every shot. Each switch is powered from a 6-MV, 0.78-MJ Marx generator which pulse charges a 24-nF intermediate-store water capacitor in 1.4-μs. Closure of the switch allows power to flow into pulse-forming transmission lines. The power pulse is subsequently compressed by water switches, which results in a total accelerator output power in excess of 70-TW. A previous version of the LTGS performed exceptionally at a 5.4-MV, 0.7-MA level on an engineering test module used for switch development. It exhibited a 1-σ jitter of ∼5  ns, a prefire and flashover rate less than 0.1%, and a lifetime in excess of 150 shots. When installed on the Z accelerator, however, the switch exhibited a prefire probability of ∼3%, a flashover probability of ∼7%, and a 15-ns jitter. The difference in performance is attributed to several factors such as higher total charge transfer, exposure to more debris, and more stressful dynamic mechanical loading upon machine discharge. Under these conditions, the replacement lifetime was less than ten shots. Since refurbishment of Z in October 2007, there have been three LTGS design iterations to improve the performance at 6.1-MV. The most recent design exhibits a

  19. Discharge-current characteristics in UV-preionized Kr/He, F2/He gas-mixtures and KrF excimer laser gas. Shigaisen yobi denri Kr/He, F2/He kongo kitai hoden oyobi KrF laser reiki hoden no denryu tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, N.; Kawakami, H.; Yukimura, K. (Doshisha University, Kyoto (Japan))

    1992-08-15

    In order to study effects of Kr and F2 on discharge characteristics of KrF excimer laser gas, gap phenomena in Kr/He and F2/He gas-mixtures were observed and discharge current (I[sub d]) was measured. In the range where Kr concentration was over 10% in Kr/He gas, in which production of filamentation as well as glow discharge started, discontinuous change in I[sub d] in the second or third half cycle was observed. According to the results of experiments and model analyses, it was considered that the discontinuity of the current showed the transition point to filamentation. When F2 concentration was in the range between 0.1 and 0.3% in F2/He mixture gas, filamentation and arc with glow were observed. Sine-waveform I[sub d] ended in the first half cycle, and began to flow again after cessation or had almost constant current due to arc and others. When F2 was over 0.4%, only are discharge was observed. It was thus found that F2 has a large effect on discharge characteristics of KrF laser gas. 18 refs., 9 figs.

  20. Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

    Science.gov (United States)

    Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

    1976-01-01

    Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

  1. Isolation of adenine salts in the gas phase from a liquid beam of aqueous solutions by IR laser irradiation

    Science.gov (United States)

    Kohno, J.-Y.; Mafuné, F.; Kondow, T.

    2002-09-01

    A continuous liquid flow in a vacuum (a liquid beam) of an aqueous solution of adenine salt containing hydrochloric acid or sodium hydroxide was irradiated with an intense pulsed IR laser at 3 μm, which is resonant to a vibrational mode related to the OH stretch vibration of H2O. Neutral species isolated into the vacuum were ionized by a pulsed UV laser at 270 nm, and the product ions were mass-analyzed by a time-of-flight mass spectrometer. It is found that AH2^{2+}{\\cdot}2Cl^- and [ A iH] ^{i-}{\\cdot} iNa^+ (i=1 3) are isolated in the vacuum from the aqueous acidic and alkaline solutions, respectively, under irradiation of the IR laser, and undergo four-photon ionization involving decomposition and proton transfer of the intermediate species under irradiation of the UV laser.

  2. Study on the effect of ambient gas on nanostructure formation on metal surfaces during femtosecond laser ablation for fabrication of low-reflective surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Smausz, Tomi, E-mail: tomi@physx.u-szeged.hu [MTA-SZTE Research Group on Photoacoustic Spectroscopy, University of Szeged, 6720 Szeged, Dóm tér 9 (Hungary); Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Csizmadia, Tamás [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Attosecond Light Pulse Source, ELI-Hu Nkft, H-6720 Szeged, Dugonics ter 13 (Hungary); Tápai, Csaba; Kopniczky, Judit [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Oszkó, Albert [Department of Physical Chemistry and Material Science, University of Szeged, H-6720 Szeged, Aradi vértanuk tere 1 (Hungary); Ehrhardt, Martin; Lorenz, Pierre; Zimmer, Klaus; Prager, Andrea [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstr. 15, 04318 Leipzig (Germany); Hopp, Béla [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary)

    2016-12-15

    Highlights: • Metal surfaces were irradiated with femtosecond laser in different gas environments. • The reflectivity, morphology and chemical composition of the surfaces were studied. • Darkening was influenced by chemical and physical interaction of the plume and gas. • Molecular mass of the applied gas had an impact on the nanostructure formation. • For some of the used metals the oxide formation affected the reflective properties. - Abstract: Nanostructure formation on bulk metals (silver, gold, copper and titanium) by femtosecond Ti-sapphire laser irradiation (775 nm, 150 fs) is studied aiming the production of low-reflectivity surfaces and the better understanding of the development process. The experiments were performed in nitrogen, air, oxygen and helium environments at atmospheric pressure. The samples were irradiated with fluences in the 0.1–2 J/cm{sup 2} range and an average pulse number of 100 falling over a given area. The reflectivity of the treated surfaces was determined by a microspectrometer in the 450–800 nm range and their morphology was studied by scanning electron microscopy. The gas ambience influenced the results via two effects: formation processes and the chemically-induced modifications of the nanostructures. In case of He the nanoparticle aggregates–otherwise generally present–are predominantly missing, which leads to a lower darkening efficiency. The presence of oxygen enhances the darkening effect for copper mostly at lower fluences, while causes a slow increase in reflectivity in the case of titanium (in case of pure oxygen) in the high fluence range. The surface morphology in case of nitrogen and air were quite similar probably due to their close molecular mass values.

  3. Visibility and Citation Impact

    Science.gov (United States)

    Ebrahim, Nader Ale; Salehi, Hadi; Embi, Mohamed Amin; Tanha, Farid Habibi; Gholizadeh, Hossein; Motahar, Seyed Mohammad

    2014-01-01

    The number of publications is the first criteria for assessing a researcher output. However, the main measurement for author productivity is the number of citations, and citations are typically related to the paper's visibility. In this paper, the relationship between article visibility and the number of citations is investigated. A case study of…

  4. Viewer Makes Radioactivity "Visible"

    Science.gov (United States)

    Yin, L. I.

    1983-01-01

    Battery operated viewer demonstrates feasibility of generating threedimensional visible light simulations of objects that emit X-ray or gamma rays. Ray paths are traced for two pinhold positions to show location of reconstructed image. Images formed by pinholes are converted to intensified visible-light images. Applications range from radioactivity contamination surveys to monitoring radioisotope absorption in tumors.

  5. Metastability exchange optical pumping in 3He gas up to 30 mT. Efficiency measurements and evidence of laser-induced nuclear relaxation

    International Nuclear Information System (INIS)

    Batz, Marion

    2011-01-01

    Advances in metastability exchange optical pumping (MEOP) of 3 He at high laser powers, with its various applications, but also at high gas pressures p 3 and high magnetic field strengths B, have provided strong motivation for revisiting the understanding and for investigating the limitations of this powerful technique. For this purpose, we present systematic experimental and theoretical studies of efficiency and of relaxation mechanisms in B≤30 mT and p 3 =0.63-2.45 mbar. 3 He nuclear polarisation is measured by light absorption in longitudinal configuration where weak light beams at 1083 nm parallel to magnetic field and cell axis with opposite circular polarisations are used to probe the distribution of populations in the metastable state. This method is systematically tested to evaluate potential systematic biases and is shown to be reliable for the study of OP dynamics despite the redistribution of populations by OP light. Nuclear polarisation loss associated to the emission of polarised light by the plasma discharge used for MEOP is found to decrease above 10 mT, as expected, due to hyperfine decoupling in highly excited states. However, this does not lead to improved MEOP efficiency at high laser power. We find clear evidence of additional laser-induced relaxation instead. The strong OP-enhanced polarisation losses, currently limiting MEOP performances, are quantitatively investigated using an angular momentum budget approach and a recently developed comprehensive model that describes the combined effects of OP, ME and relaxation, validated by comparison to experimental results.

  6. Raman fiber lasers

    CERN Document Server

    2017-01-01

    This book serves as a comprehensive, up-to-date reference about this cutting-edge laser technology and its many new and interesting developments. Various aspects and trends of Raman fiber lasers are described in detail by experts in their fields. Raman fiber lasers have progressed quickly in the past decade, and have emerged as a versatile laser technology for generating high power light sources covering a spectral range from visible to mid-infrared. The technology is already being applied in the fields of telecommunication, astronomy, cold atom physics, laser spectroscopy, environmental sensing, and laser medicine. This book covers various topics relating to Raman fiber laser research, including power scaling, cladding and diode pumping, cascade Raman shifting, single frequency operation and power amplification, mid-infrared laser generation, specialty optical fibers, and random distributed feedback Raman fiber lasers. The book will appeal to scientists, students, and technicians seeking to understand the re...

  7. 60 years of UK visibility measurements: impact of meteorology and atmospheric pollutants on visibility

    Science.gov (United States)

    Singh, Ajit; Bloss, William J.; Pope, Francis D.

    2017-02-01

    Reduced visibility is an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to road, rail, sea and air accidents. In this paper, we explore the combined influence of atmospheric aerosol particle and gas characteristics, and meteorology, on long-term visibility. We use visibility data from eight meteorological stations, situated in the UK, which have been running since the 1950s. The site locations include urban, rural and marine environments. Most stations show a long-term trend of increasing visibility, which is indicative of reductions in air pollution, especially in urban areas. Additionally, the visibility at all sites shows a very clear dependence on relative humidity, indicating the importance of aerosol hygroscopicity on the ability of aerosol particles to scatter radiation. The dependence of visibility on other meteorological parameters, such as wind speed and wind direction, is also investigated. Most stations show long-term increases in temperature which can be ascribed to climate change, land-use changes (e.g. urban heat island effects) or a combination of both; the observed effect is greatest in urban areas. The impact of this temperature change upon local relative humidity is discussed. To explain the long-term visibility trends and their dependence on meteorological conditions, the measured data were fitted to a newly developed light-extinction model to generate predictions of historic aerosol and gas scattering and absorbing properties. In general, an excellent fit was achieved between measured and modelled visibility for all eight sites. The model incorporates parameterizations of aerosol hygroscopicity, particle concentration, particle scattering, and particle and gas absorption. This new model should be applicable and is easily transferrable to other data sets worldwide. Hence, historical visibility data can be used to assess trends in aerosol particle

  8. Laser technology (selected articles)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-04-09

    This paper presents high-energy CW HF/DF chemical lasers developed under the U.S. Navy Sealite program and the Alpha program of the DARPA Triad program, and a brief account of Soviet chemical lasers. Continuous wave HF/DF chemical lasers were developed starting in the late sixties as high-power lasers of consistent interest to military circles. These are lasers that have the most matured technology among present-day high-energy lasers. It is hoped that in the near future CW HF/DF chemical lasers can be developed into a space laser weapon to deal with ICBMs. CW HF/DF chemical lasers are an integration of technologies in gas dynamics, chemistry, fluid chemistry, optics, and lasers. By using the branching chain reaction of heat liberation, inversion of the population ratio is generated to obtain lasers.

  9. Visible spectroscopy on ASDEX

    International Nuclear Information System (INIS)

    Hofmann, J.V.

    1991-12-01

    In this report visible spectroscopy and impurity investigations on ASDEX are reviewed and several sets of visible spectra are presented. As a basis for identification of metallic impurity lines during plasma discharges spectra from a stainless steel - Cu arc have been recorded. In a next step a spectrum overview of ASDEX discharges is shown which reveals the dominating role of lines from light impurities like carbon and oxygen throughout the UV and visible range (2000 A ≤ λ ≤ 8000 A). Metallic impurity lines of neutrals or single ionized atoms are observed near localized surfaces. The dramatic effect of impurity reduction by boronization of the vessel walls is demonstrated in a few examples. In extension to some ivesti-gations already published, further diagnostic applications of visible spectroscopy are presented. Finally, the hardware and software system used on ASDEX are described in detail. (orig.)

  10. Numerical investigation of the electron dynamic dependence on gas pressure in the breakdown of hydrogen by KrF laser radiation

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Elsayed, Khaled A.; Mahmoud, M. A.

    2012-10-01

    This paper presents a numerical investigation of the measurements that were carried out by Yagi et al. [12] to study the breakdown of molecular hydrogen induced by short laser of wavelength 248 nm and pulse duration 20 ns. The aim of the study is to give a detailed description of the physical processes which contributed to the breakdown of molecular hydrogen at focused intensities between 4×1012 W/cm2 and 8.0×1012 W/cm2 over gas pressure range extended from 150 to 7000 Torr. The applied computer simulation model is based on the numerical solution of the time dependent Boltzmann equation and a set of rate equations that describe the rate of change of the formed excited states population. The experimentally measured rate constants and cross-sections for the various physical processes involved in the model are used in the calculations. Provision is made for the electron impact ionization and photoionization of the excited states. The former process is incorporated parametrically in the calculation owing to the lack of quantitative description of this process. Computations are performed at each gas pressure. The calculated threshold intensities are found to be in good agreement with the experimentally measured ones, both showing a noticeable increase in the higher pressure region. Moreover, calculation of the electron energy distribution function (EEDF) and its parameters demonstrated the exact correlation between gas pressure and the physical processes responsible for determining the breakdown threshold intensity.

  11. INCREASING EFFICIENCY OF REPAIRING, MANUFACTURING AND OPERATION OF THE TPP FACILITIES BY TECHNOLOGY OF GAS-THERMAL COATING AND LASER SURFACE MELTING

    Directory of Open Access Journals (Sweden)

    O. E. Grachev

    2015-01-01

    Full Text Available The article considers effectiveness increase of the TPP heat-mechanical equipment repair, manufacturing and maintenance as exemplified by gas-thermal technique for hardening laststages rotor blades of the steam turbines. The rotor blades work under conditions of intense power loading, their airfoil being erosion-corrosion destructed by the action of the moist-steam flow. Repairing companies employ quite a number of technologies to restore some of erosion-worn rotor blades. Inter alia, argon-arc, plasma and gas-powder weld deposition of the original material with subsequent machining, stellite protection recovery, electrical spark alloying the entry edge mat surface, spraying ion-plasma coating on the blade airfoil surface. In domestic turbine building, rotor blades of the steam turbines last stages are manufactured of martensitic class stainless steel. The key condition for successful blade restoration is thermal effect minimizing on the base material for excluding the slag areas possible forming. The laser surface coating technology provides these conditions. They coat the surface of an item being processed by way of melting the base and the adding material. In as much the base melts smallest, the coating characteristics depend mainly on the properties of adding material. The procedure of laser coating passes through several stages including physical contact creation, chemical interaction (laser radiation absorption, volumetrical processes resulting in formation of stable bonds in volume of the materials that have reacted. For the low-pressure cylinder rotor blades supplementary protection against erosion destruction, LLC ‘Technological Systems of Protective Coating’ developed technology of the blade airfoil protective finish by method of high-speed gas-flame sputter. The company realized this technology in 2012 during K-200-12,8 turbine (of the Leningrad Metallurgical Works – LMZ repairing in Zainsk SDPP by JSC ‘Tatenergo’. The

  12. Visible imaging of edge turbulence in NSTX

    International Nuclear Information System (INIS)

    S. Zweben; R. Maqueda; K. Hill; D. Johnson; S. Kaye; H. Kugel; F. Levinton; R. Maingi; L. Roquemore; S. Sabbagh; G. Wurden

    2000-01-01

    Edge plasma turbulence in tokamaks and stellarators is believed to cause the radial heat and particle flux across the separatrix and into the scrape-off-layers of these devices. This paper describes initial measurements of 2-D space-time structure of the edge density turbulence made using a visible imaging diagnostic in the National Spherical Torus Experiment (NSTX). The structure of the edge turbulence is most clearly visible using a method of ''gas puff imaging'' to locally illuminate the edge density turbulence

  13. Laser induced pyrolysis techniques

    International Nuclear Information System (INIS)

    Vanderborgh, N.E.

    1976-01-01

    The application of laser pyrolysis techniques to the problems of chemical analysis is discussed. The processes occurring during laser pyrolysis are first briefly reviewed. The problems encountered in laser pyrolysis gas chromatography are discussed using the analysis of phenanthrene and binary hydrocarbons. The application of this technique to the characterization of naturally occurring carbonaceous material such as oil shales and coal is illustrated

  14. Pulsed, all solid-state light source in the visible spectral region based on non-linear cavity dumping

    DEFF Research Database (Denmark)

    Tidemand-Lichtenberg, Peter; Andersen, Martin; Johansson, Sandra

    We propose a novel generic approach for generation of pulsed light in the visible spectrum, based on SFG between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser....

  15. Lasers | RadTown USA | US EPA

    Science.gov (United States)

    2017-08-07

    Laser light is an intense, focused beam of visible light radiation. Lasers are used in many workplaces, including construction, surveying and medicine. High-powered laser light can cause severe skin burns and permanent eye damage. Hand-held laser pointers are not toys. They should not be used by children.

  16. Laser fusion neutron source employing compression with short pulse lasers

    Science.gov (United States)

    Sefcik, Joseph A; Wilks, Scott C

    2013-11-05

    A method and system for achieving fusion is provided. The method includes providing laser source that generates a laser beam and a target that includes a capsule embedded in the target and filled with DT gas. The laser beam is directed at the target. The laser beam helps create an electron beam within the target. The electron beam heats the capsule, the DT gas, and the area surrounding the capsule. At a certain point equilibrium is reached. At the equilibrium point, the capsule implodes and generates enough pressure on the DT gas to ignite the DT gas and fuse the DT gas nuclei.

  17. Advances in copper laser technology: kinetic enhancement [review article

    Science.gov (United States)

    Withford, Michael J.; Brown, Daniel J. W.; Mildren, Richard P.; Carman, Robert J.; Marshall, Graham D.; Piper, James A.

    Since their invention in 1966 copper vapour lasers (CVLs) have developed into a mature technology with applications including high-speed imaging, micro-machining, non-linear frequency conversion to the ultraviolet, and pumping of solid-state laser materials. However, the performance characteristics of conventional CVLs are fundamentally limited by kinetic processes at play within the gain medium and hence, these devices largely failed to keep pace with advances in visible solid state lasers during the late 1980s and early 1990s. In 1996 a new subclass of CVL, termed a kinetically enhanced or KE-CVL, was developed that used a ternary gas mixture (HCl-H 2-Ne) to tailor the kinetic processes that limit laser performance. These devices offer dramatic improvements in power (both average and high beam quality) and repetition rate scalability. Indeed, 100 W of visible, high beam quality power is now readily available from relatively small copper laser systems. In this paper the underlying principles and performance characteristics of KE-CVLs will be reviewed.

  18. Dual-beam, second-derivative tunable diode-laser infrared spectroscopy applied to trace-gas measurement

    International Nuclear Information System (INIS)

    Tallant, D.R.; Jungst, R.G.

    1981-04-01

    A dual beam diode laser spectrometer has been constructed using off-axis reflective optics. The spectrometer can be amplitude modulated for direct absorption measurements or frequency modulated to obtain derivative spectra. The spectrometer has high throughput, is easy to operate and align, provides good dual beam compensation, and has no evidence of the interference effects that have been observed in diode laser spectrometers using refractive optics. Unpurged, using second derivative techniques, the instrument has measured 108 parts-per-million CO (10 cm absorption cell, atmospheric pressure-broadened) with good signal/noise. With the replacement of marginal instrumental components, the signal/noise should be substantially increased. This instrument was developed to monitor the evolution of decomposition gases in sealed containers of small volume at atmospheric pressure

  19. UV Laser Co-Photolytic Approach to Gas-Phase Formation and Deposition of Nano-Sized Germanium Sulfides.

    Czech Academy of Sciences Publication Activity Database

    Tomovska, R.; Vorlíček, Vladimír; Boháček, Jaroslav; Šubrt, Jan; Pola, Josef

    2006-01-01

    Roč. 182, 1 (2006) , s. 107-111 ISSN 0022-3573 R&D Projects: GA MŠk(CZ) ME 486 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z10100523; CEZ:AV0Z40320502 Keywords : laser deposition * germanium sulfides * nanomaterials Subject RIV: CH - Nuclear ; Quantum Chemistry Impact factor: 1.533, year: 2006

  20. Modeling of ns and ps laser-induced soft X-ray sourcesusing nitrogen gas puff target

    Czech Academy of Sciences Publication Activity Database

    Vrba, Pavel; Vrbová, M.; Zakharov, S.V.; Zakharov, V.S.

    2014-01-01

    Roč. 21, č. 7 (2014), 073301-073301 ISSN 1070-664X R&D Projects: GA ČR GAP102/12/2043; GA MŠk(CZ) LG13029 Institutional support: RVO:61389021 Keywords : Capillary Z-pinch * Water window radiation source * RHMD Code Z* Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.142, year: 2014 http://scitation.aip.org/content/aip/journal/pop/21/7/10.1063/1.4887295