WorldWideScience

Sample records for laser transition studies

  1. ULTRAVIOLET TRANSITIONS IN EUROPIUM STUDIED WITH A FREQUENCY-DOUBLED CW RING DYE-LASER

    NARCIS (Netherlands)

    Eliel, E.R.; Hogervorst, W.; van Leeuwen, K.A.H.; Post, B.H.

    1981-01-01

    High resolution laser spectroscopy has been applied to the study of three ultraviolet transitions in Europium at λ = 294.8, 295.1 and 295.8 nm. The tunable narrowband UV has been generated by intracavity frequency doubling in a cw ring dye laser using a temperate tuned, Brewster angled ADA crystal.

  2. Time-Resolved Studies of Laser-Induced Phase Transitions in Gallium Arsenide

    Science.gov (United States)

    Siegal, Yakir

    This thesis describes a series of time-resolved experiments of the linear and nonlinear optical properties of GaAs during laser-induced phase transitions. The first set of experiments consists of a direct determination of the behavior of the linear dielectric constant at photon energies of 2.2 eV and 4.4 eV following excitation of the sample with 1.9-eV, 70-fs laser pulses spanning a fluence range from 0 to 2.5 kJ/m^2. The results from this set of experiments were used to extract the behavior of the second-order optical susceptibility from second-harmonic generation measurements made under identical excitation conditions. These experiments are unique because they provide explicit information on the behavior of intrinsic material properties--the linear and nonlinear optical susceptibilities--during laser-induced phase transitions in semiconductors without the ambiguities in interpretation that are generally inherent in reflectivity and second-harmonic generation measurements. The dielectric constant data indicate a drop in the average bonding-antibonding splitting of GaAs following the laser pulse excitation. This behavior leads to a collapse of the band-gap on a picosecond time scale for excitation at fluences near the damage threshold of 1.0 kJ/m ^2 and even faster at higher excitation fluences. The changes in the electronic band structure result from a combination of electronic screening by the excited free carriers and structural deformation of the lattice caused by the destabilization of the covalent bonds. The behavior of the second-order susceptibility shows that the material loses long-range order before the average bonding-antibonding splitting, which is more sensitive to short-range structure, changes significantly. Loss of long-range order and a drop of more than 2 eV in the average bonding-antibonding splitting are seen even at fluences below the damage threshold, a regime in which the laser-induced changes are reversible.

  3. Lithium tantalate single crystal for pyroelectricity-based laser energy-meter: growth, application and phase transition study

    International Nuclear Information System (INIS)

    Bhaumik, Indranil; Ganesamoorthy, S.; Bhatt, R.; Karnal, A.K.; Gupta, P.K.

    2009-01-01

    Single crystals of lithium tantalate have been grown. Dielectric-spectroscopy study reveals phase transition in congruent lithium tantalate (CLT) single crystal is diffusive and frequency dependent in contrast to that in near stoichiometric lithium tantalate where it is sharper. The ac conductivity measurements show that the conductivity is lower for 0.5Mg-SLT as compared to 1.0Mg-SLT. This is explained in terms of a Li-vacancy model. Calculation of activation energy from the lnσ vs. 1000/T plot reveals that hopping of Li + ions becomes difficult for 0.5 Mg-SLT. The pyroelectric response of CLT for pulsed Nd:YAG laser output has been tested. (author)

  4. Phase transition and thermal expansion studies of alumina thin films prepared by reactive pulsed laser deposition.

    Science.gov (United States)

    Balakrishnan, G; Thirumurugesan, R; Mohandas, E; Sastikumar, D; Kuppusami, P; Songl, J I

    2014-10-01

    Aluminium oxide (Al2O3) thin films were deposited on Si (100) substrates at an optimized oxygen partial pressure of 3 x 10(-3) mbar at room temperature by pulsed laser deposition (PLD). The films were characterized by high temperature X-ray diffraction (HTXRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The HTXRD pattern showed the cubic y-Al2O3 phase in the temperature range 300-973 K. At temperatures ≥ 1073 K, the δ and θ-phases of Al2O3 were observed. The mean linear thermal expansion coefficient and volume thermal expansion coefficient of γ-Al2O3 was found to be 12.66 x 10(-6) K(-1) and 38.87 x 10(-6) K(-1) in the temperature range 300 K-1073 K. The field emission scanning electron microscopy revealed a smooth and structureless morphology of the films deposited on Si (100). The atomic force microscopy study indicated the increased crystallinity and surface roughness of the films after annealing at high temperature.

  5. Recombinational laser employing electron transitions of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Biriukov, A S; Prokhorov, A M; Shelepin, L A; Shirokov, N N

    1974-12-01

    Conditions are established for obtaining laser action in the visible and uv regions of the spectrum, using transitions between electronic states of diatomic molecules during recombination of a dissociated gas. The mechanism of population inversion was studied for the oxygen molecule, and gain estimates were obtained for laser action at a wavelength of 4881 A. The feasibility of laser action at other wavelengths was examined.

  6. Laser spectroscopic studies of the pure rotational U0(0) and W0(0) transitions of solid parahydrogen

    International Nuclear Information System (INIS)

    Chan, M.; Lee, S.S.; Okumura, M.; Oka, T.

    1991-01-01

    High resolution spectrum of multipole-induced transitions of solid parahydrogen was recorded using diode and difference frequency laser spectroscopy. The J=4 left-arrow 0 pure rotational U 0 (0) transition observed in the diode spectrum agrees well in frequency with the value reported by Balasubramanian et al. [Phys. Rev. Lett. 47, 1277 (1981)] but we observed a spectral width smaller by about a factor of 4. The J=6 left-arrow 0 W 0 (0) transition was observed to be exceedingly sharp, with a width of ∼70 MHz, using a difference frequency spectrometer with tone-burst modulation. This transition is composed of three components with varying relative intensity depending upon the direction of polarization of laser radiation. These components were interpreted as the splitting of the M levels in the J=6 state due to crystal field interactions. In addition, a new broad feature was found at 2452.4 cm -1 in the low resolution Fourier-transform infrared (FTIR) spectrum of solid hydrogen and was assigned to be the phonon branch W R (0) transition of the W 0 (0) line. The selection rules, crystal field splitting of J=4 and J=6 rotons, and the measured linewidth based on these observations are discussed

  7. Laser-induced multiphoton transitions

    International Nuclear Information System (INIS)

    Stenholm, S.

    1978-06-01

    Laser induced multiphoton processes are reviewed. The effects of strong fields on atoms are discussed. The perturbation treatment is presented and also its generalization to treat intermediate resonances. The influence of atomic coherence is discussed heuristically and the relation between quantal and classical descriptions of the field is elucidated by reference to the dressed atom description. Atomic ionization experiments are reviewed and the present understanding of multiphoton dissociation of molecules is explained. Finally some prospects for the future are discussed. (author)

  8. Laser Assisted Free-Free Transition in Electron - Atom Collision

    Science.gov (United States)

    Sinha, C.; Bhatia, A. K.

    2011-01-01

    Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

  9. Transition from isentropic to isothermal expansion in laser produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Barrero, A; Santartin, J R

    1980-07-01

    The transition that the expansion flow of laser-produced plasmas experiences when ones moves from long, low intensity pulses (temperature vanishing at the Isentropic plasma-vacuum front, lying at finite distance) to short, intense ones (non-zero, uni- form temperature at the plasma-vacuum front, lying at infinity) is studied. For planar geometry and large Ion number Z{sub j} the transition occurs for d {phi} / d t {approx_equal} 0.14(27/8)k{sup 7}/2 Z{sub j}{sup 3}/2/m{sub j}{sup 3}/2 K; {phi}, k, m{sub j}, and K are laser intensity, Boltzmann s constant, ion mass, and Spitzer s heat conduction coefficient. This result remains valid for finite Z{sub j} though the numerical factor in d{phi} / d t is different. In spherical geometry a similar transition occurs even in steady conditions. Shorter wavelength lasers and higher Z{sub j} plasmas allow faster rising pulses below transition. (Author) 13 refs.

  10. Wettability transition of laser textured brass surfaces inside different mediums

    Science.gov (United States)

    Yan, Huangping; Abdul Rashid, Mohamed Raiz B.; Khew, Si Ying; Li, Fengping; Hong, Minghui

    2018-01-01

    Hydrophobic surface on brass has attracted intensive attention owing to its importance in scientific research and practical applications. Laser texturing provides a simple and promising method to achieve it. Reducing wettability transition time from hydrophilicity to hydrophobicity or superhydrophobicity remains a challenge. Herein, wettability transition of brass surfaces with hybrid micro/nano-structures fabricated by laser texturing was investigated by immersing the samples inside different mediums. Scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy and surface contact angle measurement were employed to characterize surface morphology, chemical composition and wettability of the fabricated surfaces of brass samples. Wettability transition time from hydrophilicity to hydrophobicity was shortened by immersion into isopropyl alcohol for a period of 3 h as a result of the absorption and accumulation of organic substances on the textured brass surface. When the textured brass sample was immersed into sodium bicarbonate solution, flower-like structures on the sample surface played a key role in slowing down wettability transition. Moreover, it had the smallest steady state contact angle as compared to the others. This study provides a facile method to construct textured surfaces with tunable wetting behaviors and effectively extend the industrial applications of brass.

  11. Laser induced single-crystal transition in polycrystalline silicon

    International Nuclear Information System (INIS)

    Vitali, G.; Bertolotti, M.; Foti, G.; Rimini, E.

    1978-01-01

    Transition to single crystal of polycrystalline Si material underlying a Si crystal substrate of 100 orientation was obtained via laser irradiation. The changes in the structure were analyzed by reflection high energy electron diffraction and by channeling effect technique using 2.0 MeV He Rutherford scattering. The power density required to induce the transition in a 4500 A thick polycrystalline layer is about 70 MW/cm 2 (50ns). The corresponding amorphous to single transition has a threshold of about 45 MW/cm 2 . (orig.) 891 HPOE [de

  12. Non-Fourier heat conduction and phase transition in laser ablation of polytetrafluoroethylene (PTFE)

    Science.gov (United States)

    Zhang, Yu; Zhang, Daixian; Wu, Jianjun; Li, Jian; He, Zhaofu

    2017-11-01

    The phase transition in heat conduction of polytetrafluoroethylene-like polymers was investigated and applied in many fields of science and engineering. Considering more details including internal absorption of laser radiation, reflectivity of material and non-Fourier effect etc., the combined heat conduction and phase transition in laser ablation of polytetrafluoroethylene were modeled and investigated numerically. The thermal and mechanic issues in laser ablation were illustrated and analyzed. Especially, the phenomenon of temperature discontinuity formed in the combined phase transition and non-Fourier heat conduction was discussed. Comparisons of target temperature profiles between Fourier and non-Fourier heat conduction in melting process were implemented. It was indicated that the effect of non-Fourier plays an important role in the temperature evolvement. The effect of laser fluence was proven to be significant and the thermal wave propagation was independent on the laser intensity for the non-Fourier heat conduction. Besides, the effect of absorption coefficients on temperature evolvements was studied. For different ranges of absorption coefficients, different temperature evolvements can be achieved. The above numerical simulation provided insight into physical processes of combined non-Fourier heat conduction and phase transition in laser ablation.

  13. Laser surface alloying of aluminium-transition metal alloys

    International Nuclear Information System (INIS)

    Almeida, A.; Vilar, R.

    1998-01-01

    Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM) alloys. Cr and Mo are particularly interesting alloying elements to produce stable high-strength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO 2 laser . This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloy, over the last years. (Author) 16 refs

  14. Phase control of the probability of electronic transitions in the non-perturbative laser field intensity

    International Nuclear Information System (INIS)

    Yokoyama, Keiichi; Sugita, Akihiro; Yamada, Hidetaka; Teranishi, Yoshiaki; Yokoyama, Atsushi

    2007-01-01

    A preparatory study on the quantum control of the selective transition K(4S 1/2 ) → K(4P J ) (J=1/2, 3/2) in intense laser field is reported. To generate high average power femtosecond laser pulses with enough field intensity, a Ti:Sapphire regenerative amplifier system with a repetition rate of 1 kHz is constructed. The bandwidth and pulse energy are shown to qualify the required values for the completely selective transition with 100% population inversion. A preliminary experiment of the selective excitation shows that the fringe pattern formed by a phase related pulse pair depends on the laser intensity, indicating that the perturbative behavior of the excitation probabilities is not valid any more and the laser intensity reaches a non-perturbative region. (author)

  15. Study on laser atomic spectroscopy

    International Nuclear Information System (INIS)

    Lee, Jong Min; Song, Kyu Seok; Jeong, Do Young; Kim, Chul Joong; Han, Phil Soon

    1992-01-01

    Electric discharge type atomic vaporizer is developed for the spectroscopic study on actinide elements. Laser induced fluorescence study on actinide elements is performed by using this high temperature type atomizer. For the effective photoionization of elements, copper vapor laser pumped dye laser and electron beam heating type atomic vaporizer are built and their characteristics are measured. In addition, resonance ionization mass spectroscopic analysis for lead sample as well as laser induced fluorescence study on uranium sample in solution phase is made. (Author)

  16. Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

    Science.gov (United States)

    Bhatia, A. K.; Sinha, Chandana

    2010-01-01

    We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very loud incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering weave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts the exchange approximation has only been considered. We calculate the laser assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

  17. Laser-induced breakdown spectroscopy with laser irradiation resonant with vibrational transitions

    International Nuclear Information System (INIS)

    Khachatrian, Ani; Dagdigian, Paul J.

    2010-01-01

    An investigation of laser-induced breakdown spectroscopy (LIBS) of polymers, both in bulk form and spin coated on Si wafers, with laser irradiation in the mid-infrared spectral region is presented. Of particular interest is whether the LIBS signals are enhanced when the laser wavelength is resonant with a fundamental vibrational transition of the polymer. Significant increases in the LIBS signals were observed for irradiation on hydride stretch fundamental transitions, and the magnitude of the enhancement showed a strong dependence on the mode excited. The role of the substrate was investigated by comparison of results for bulk and spin-coated samples. The polymers investigated were Nylon 12 and poly(vinyl alcohol-co-ethylene).

  18. Pump requirements for betatron-generated femtosecond X-ray laser at saturation from inner-shell transitions

    International Nuclear Information System (INIS)

    Ribiere, M.; Grunenwald, J.; Ribeiro, P.; Sebban, S.; Phuoc, K.Ta; Gautier, J.; Kozlova, M.; Zeitoun, P.; Rousse, A.; Jacquemot, S.; Cheron, B.G.

    2012-01-01

    We study pump requirements to produce femtosecond X-ray laser pulses at saturation from inner-shell transitions in the amplified spontaneous emission regime. Since laser-based betatron radiation is considered as the pumping source, we first study the impact of the driving laser power on its intensity. Then we investigate the amplification behavior of the K-a transition of nitrogen at 3.2 nm (395 eV) from radiative transfer calculations coupled with kinetics modeling of the ion population densities. We show that the saturation regime may be experimentally achieved by using PW-class laser-accelerated electron bunches. Finally, we show that this X-ray laser scheme can be extended to heavier atoms and we calculate pump requirements to reach saturation at 1.5 nm (849 eV) from the K-a transition of neon. (authors)

  19. Instantaneous nonvertical electronic transitions with shaped femtosecond laser pulses: Is it possible?

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Møller, Klaus Braagaard

    2003-01-01

    In molecular electronic transitions, a vertical transition can be induced by an ultrashort laser pulse. That is, a replica of the initial nuclear state-times the transition dipole moment of the electronic transition-can be created instantaneously (on the time scale of nuclear motion) in the excited...

  20. Critical temperature transitions in laser-mediated cartilage reshaping

    Science.gov (United States)

    Wong, Brian J.; Milner, Thomas E.; Kim, Hong H.; Telenkov, Sergey A.; Chew, Clifford; Kuo, Timothy C.; Smithies, Derek J.; Sobol, Emil N.; Nelson, J. Stuart

    1998-07-01

    In this study, we attempted to determine the critical temperature [Tc] at which accelerated stress relaxation occurred during laser mediated cartilage reshaping. During laser irradiation, mechanically deformed cartilage tissue undergoes a temperature dependent phase transformation which results in accelerated stress relaxation. When a critical temperature is attained, cartilage becomes malleable and may be molded into complex new shapes that harden as the tissue cools. Clinically, reshaped cartilage tissue can be used to recreate the underlying cartilaginous framework of structures such as the ear, larynx, trachea, and nose. The principal advantages of using laser radiation for the generation of thermal energy in tissue are precise control of both the space-time temperature distribution and time- dependent thermal denaturation kinetics. Optimization of the reshaping process requires identification of the temperature dependence of this phase transformation and its relationship to observed changes in cartilage optical, mechanical, and thermodynamic properties. Light scattering, infrared radiometry, and modulated differential scanning calorimetry (MDSC) were used to measure temperature dependent changes in the biophysical properties of cartilage tissue during fast (laser mediated) and slow (conventional calorimetric) heating. Our studies using MDSC and laser probe techniques have identified changes in cartilage thermodynamic and optical properties suggestive of a phase transformation occurring near 60 degrees Celsius.

  1. Free-Free Transitions in the Presence of Laser Fields and Debye Potential at Very Low Incident Electron Energies

    Science.gov (United States)

    Bhatia, Anand

    2012-01-01

    We study the free-free transition in electron-helium ion in the ground state and embedded in a Debye potential in the presence of an external laser field at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen as monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function for it. The scattering wave function for the incident electron on the target embedded in a Debye potential is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transition for absorption/emission of a single photon or no photon exchange. The results will be presented at the conference.

  2. American Studies in Transition

    DEFF Research Database (Denmark)

    Nye, David

    Papers first given at a conference the previous year in Fåborg, Denmark, with a dual focus on 20th century America and new methods in American Studies.......Papers first given at a conference the previous year in Fåborg, Denmark, with a dual focus on 20th century America and new methods in American Studies....

  3. First-principles assessment of potential ultrafast laser-induced structural transition in Ni

    Energy Technology Data Exchange (ETDEWEB)

    Bévillon, E.; Colombier, J.P., E-mail: jean.philippe.colombier@univ-st-etienne.fr; Stoian, R.

    2016-06-30

    Highlights: • First-principles theory calculations in nonequilibrium conditions. • Electronic temperatures fully and consistently taken into account. • Evaluation of an ultrafast laser-induced solid-to-solid transition in Ni. • Relative energies, phonon spectra and energy path are evaluated. • Discussion on the generation of non-thermal forces in metals. - Abstract: The possibility to trigger ultrafast solid-to-solid transitions in transition metals under femtosecond laser irradiation is investigated by means of first-principles calculations. Electronic heating can drastically modify screening, charge distribution and atomic binding features, potentially determining new structural relaxation paths in the solid phase, before thermodynamic solid-to-liquid transformations set in. Consequently, we evaluate here the effect of electronic excitation on structural stability and conditions for structural transitions. Ni is chosen as a case study for the probability of a solid transition, and the stability of its FCC phase is compared to the non-standard HCP structure while accounting for the heating of the electronic subsystem. From a phonon spectra analysis, we show that the thermodynamic stability order reverses at an electronic temperature of around 10{sup 4} K. Both structures exhibit a dynamic stability, indicating they present a metastability depending on the heating. However, the general hardening of phonon modes with the increase of the electronic temperature points out that no transformation will occur, as confirmed by the study of a typical FCC to HCP diffusionless transformation path, showing an increasing energy barrier. Finally, based on electronic density of states interpretation, the tendency of different metal categories to undergo or not an ultrafast laser-induced structural transition is discussed.

  4. Transition probabilities of some Si II lines obtained by laser produced plasma emission

    International Nuclear Information System (INIS)

    Blanco, F.; Botho, B.; Campos, J.

    1995-01-01

    The absolute transition probabilities for 28 Si II spectral lines have been determined by measurement of emission line intensities from laser-produced plasmas of Si in Ar and Kr atmospheres. The studied plasma has a temperature of about 2 . 10 4 K and 10 17 cm -3 electron density. The local thermodynamic equilibrium conditions and plasma homogeneity have been checked. The results are compared with the available experimental and theoretical data and with present Hartree-Fock calculations in LS coupling. (orig.)

  5. Solid - solid and solid - liquid phase transitions of iron and iron alloys under laser shock compression

    Science.gov (United States)

    Harmand, M.; Krygier, A.; Appel, K.; Galtier, E.; Hartley, N.; Konopkova, Z.; Lee, H. J.; McBride, E. E.; Miyanishi, K.; Nagler, B.; Nemausat, R.; Vinci, T.; Zhu, D.; Ozaki, N.; Fiquet, G.

    2017-12-01

    An accurate knowledge of the properties of iron and iron alloys at high pressures and temperatures is crucial for understanding and modelling planetary interiors. While Earth-size and Super-Earth Exoplanets are being discovered in increasingly large numbers, access to detailed information on liquid properties, melting curves and even solid phases of iron and iron at the pressures and temperatures of their interiors is still strongly limited. In this context, XFEL sources coupled with high-energy lasers afford unique opportunities to measure microscopic structural properties at far extreme conditions. Also the achievable time resolution allows the shock history and phase transition mechanisms to be followed during laser compression, improving our understanding of the high pressure and high strain experiments. Here we present recent studies devoted to investigate the solid-solid and solid-liquid transition in laser-shocked iron and iron alloys (Fe-Si, Fe-C and Fe-O alloys) using X-ray diffraction and X-ray diffuse scattering. Experiment were performed at the MEC end-station of the LCLS facility at SLAC (USA). Detection of the diffuse scattering allowed the identification of the first liquid peak position along the Hugoniot, up to 4 Mbar. The time resolution shows ultrafast (between several tens and several hundreds of picoseconds) solid-solid and solid-liquid phase transitions. Future developments at XFEL facilities will enable detailed studies of the solid and liquid structures of iron and iron alloys as well as out-of-Hugoniot studies.

  6. Nuclear fission fragment excitation of electronic transition laser media

    International Nuclear Information System (INIS)

    Lorents, D.C.; McCusker, M.V.; Rhodes, C.K.

    1976-01-01

    The properties of high energy electronic transition lasers excited by fission fragments are expanded. Specific characteristics of the media including density, excitation rates, wavelength, kinetics, fissile material, scale size, and medium uniformity are assessed. The use of epithermal neutrons, homogeneously mixed fissile material, and special high cross section nuclear isotopes to optimize coupling of the energy to the medium are shown to be important considerations maximizing the scale size, energy deposition, and medium uniformity. A performance limit point of approximately 1000 J/l in approximately 100 μs pulses is established for a large class of systems operating in the near ultraviolet and visible spectral regions. It is demonstrated that e-beam excitation can be used to simulate nuclear pumping conditions to facilitate the search for candidate media. Experimental data for the kinetics of a XeF* laser operating in Ar/Xe/F 2 /UF 6 mixtures are given. These reactor-pumped systems are suitable for scaling to volumes on the order of (meters) 3

  7. Laser surface alloying of aluminium-transition metal alloys

    Directory of Open Access Journals (Sweden)

    Almeida, A.

    1998-04-01

    Full Text Available Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM alloys. Cr and Mo are particularly interesting alloying elements to produce stable highstrength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO2 laser. This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloys, over the last years.

    En el presente trabajo se estudia la aleación superficial mediante láser de aluminio con metales de transición. El cromo y el molibdeno son particularmente interesantes porque producen aleaciones de alta resistencia y por el bajo coeficiente de difusión y solución sólida en aluminio. Para producir estas aleaciones se ha seguido un procedimiento desarrollado en dos partes. En primer lugar, el material se alea usando una baja velocidad de procesado y en segundo lugar la estructura se modifica mediante un refinamiento posterior. Este procedimiento se ha empleado en la producción de aleaciones Al-Cr, Al-Mo y Al-Nb mediante aleación con láser de CO2 de polvos de Cr, Mo o Nb en aluminio y la aleación 7175. Este trabajo es una revisión del desarrollado en el Instituto Superior Técnico de Lisboa en los últimos años.

  8. Gastrointestinal transit and reflux studies

    International Nuclear Information System (INIS)

    Greenspan, R.L.; Kochan, J.

    1988-01-01

    Current imaging modalities such as magnetic resonance imaging and computed tomography provide anatomic resolution far beyond that achievable with the current methods of scintigraphic imaging. Consequently, the strength of nuclear medicine has shifted and now lies in its ability to provide physiologic data noninvasively and simply. This ability is well illustrated by the scintigraphic techniques developed for evaluation of the alimentary tract. Studies of esophageal transit, gastroesophageal reflux, and gastric emptying are now widely available. Evaluation of small and large intestinal transit have also been investigated. These techniques are discussed in the present chapter

  9. Study on Laser Welding Process Monitoring Method

    OpenAIRE

    Knag , Heeshin

    2017-01-01

    International audience; In this paper, a study of quality monitoring technology for the laser welding was conducted. The laser welding and the industrial robotic systems were used with robot-based laser welding systems. The laser system used in this study was 1.6 kW fiber laser, while the robot system was Industrial robot (pay-load : 130 kg). The robot-based laser welding system was equipped with a laser scanner system for remote laser welding. The welding joints of steel plate and steel plat...

  10. Study on Laser Welding Process Monitoring Method

    OpenAIRE

    Heeshin Knag

    2016-01-01

    In this paper, a study of quality monitoring technology for the laser welding was conducted. The laser welding and the industrial robotic systems were used with robot-based laser welding systems. The laser system used in this study was 1.6 kW fiber laser, while the robot system was Industrial robot (pay-load : 130 kg). The robot-based laser welding system was equipped with a laser scanner system for remote laser welding. The welding joints of steel plate and steel plate coated with zinc were ...

  11. Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Gong, W.; Peng, X., E-mail: xiangpeng@pku.edu.cn; Li, W.; Guo, H., E-mail: hongguo@pku.edu.cn [State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Electronics Engineering and Computer Science, Center for Quantum Information Technology, and Center for Computational Science and Engineering (CCSE), Peking University, Beijing 100871 (China)

    2014-07-15

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  12. Strategies for Time-resolved X-ray Diffraction of Phase Transitions with Laser Compression

    Science.gov (United States)

    Benedetti, Laura Robin; Eggert, J. H.; Bradley, D. K.; Bell, P. M.; Kilkenny, J. D.; Palmer, N.; Petre, R. B.; Rygg, J. R.; Sorce, C.; Collins, G. W.; Boehly, T. R.

    2017-10-01

    As part of a program to document kinetics of phase transitions under laser-driven dynamic compression, we are designing a platform to make multiple x-ray diffraction measurements during a single laser experiment. Our plans include experimental development at Omega-EP and eventual implementation at NIF. We will present our strategy for designing a robust platform that can effectively document a wide variety of phase transformations by utilizing both streaked and multiple-frame imaging detectors. Preliminary designs utilize a novel CMOS detector designed by Sandia National Lab. Our initial experiments include scoping studies that will focus on photometrics and shielding requirements in the high EMP environment close to the target. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC, LLNL-ABS-734470.

  13. A Faraday laser lasing on Rb 1529 nm transition.

    Science.gov (United States)

    Chang, Pengyuan; Peng, Huanfa; Zhang, Shengnan; Chen, Zhangyuan; Luo, Bin; Chen, Jingbiao; Guo, Hong

    2017-08-21

    We present the design and performance characterization of a Faraday laser directly lasing on the Rb 1529 nm transition (Rb, 5P 3/2  - 4D 5/2 ) with high stability, narrow spectral linewidth and low cost. This system does not need an additional frequency-stabilized pump laser as a prerequisite to preparing Rb atom from 5S to 5P excited state. Just by using a performance-improved electrodeless discharge lamp-based excited-state Faraday anomalous dispersion optical filter (LESFADOF), we realized a heterogeneously Faraday laser with the frequency corresponding to atomic transition, working stably over a range of laser diode (LD) current from 85 mA to 171 mA and the LD temperature from 11 °C to 32 °C, as well as the 24-hour long-term frequency fluctuation range of no more than 600 MHz. Both the laser linewidth and relative intensity noisy (RIN) are measured. The Faraday laser lasing on Rb 1529 nm transition (telecom C-band) can be applied to further research on metrology, microwave photonics and optical communication systems. Besides, since the transitions correspongding to the populated excited-states of alkali atoms within lamp are extraordinarily rich, this scheme can increase the flexibility for choosing proper wavelengths for Faraday laser and greatly expand the coverage of wavelength corresponding to atomic transmission for laser frequency stabilization.

  14. Amorphous-polycrystal transition induced by laser pulse in self-ion implanted silicon

    International Nuclear Information System (INIS)

    Foti, G.; Rimini, E.; Vitali, G.; Bertolotti, M.

    1977-01-01

    Reflection high energy electron diffraction has been used to investigate the amorphous to polycrystalline structure transition in silicon induced by laser pulse. The power density of the ruby laser pulse, in the free generation mode, has been maintained below the threshold to induce surface damage. Depth analysis has been carried out in silicon crystal using the channeling effect technique. (orig.) [de

  15. Laser plasma physics in shock ignition – transition from collisional to collisionless absorption

    Directory of Open Access Journals (Sweden)

    Klimo O.

    2013-11-01

    Full Text Available Shock Ignition is considered as a relatively robust and efficient approach to inertial confinement fusion. A strong converging shock, which is used to ignite the fuel, is launched by a high power laser pulse with intensity in the range of 1015 − 1016 W/cm2 (at the wavelength of 351 nm. In the lower end of this intensity range the interaction is dominated by collisions while the parametric instabilities are playing a secondary role. This is manifested in a relatively weak reflectivity and efficient electron heating. The interaction is dominated by collective effects at the upper edge of the intensity range. The stimulated Brillouin and Raman scattering (SBS and SRS respectively take place in a less dense plasma and cavitation provides an efficient collisionless absorption mechanism. The transition from collisional to collisionless absorption in laser plasma interactions at higher intensities is studied here with the help of large scale one-dimensional Particle-in-Cell (PIC simulations. The relation between the collisional and collisionless processes is manifested in the energy spectrum of electrons transporting the absorbed laser energy and in the spectrum of the reflected laser light.

  16. Erosion of the 4-6- and 8 group transition metals under intense laser radiation

    International Nuclear Information System (INIS)

    Samsonov, G.V.; Verkhoturov, A.D.; Roshchina, A.I.; Vasil'ev, A.V.; Klimenko, V.P.

    1976-01-01

    The erosion resistance is studied of transition metals of Groups 4-6 and 8 at laser emission of approximately 6x1O 7 W/cm 2 . It is shown that as the emission power increases from 10 6 to 6x10 7 W/cm 2 the erosion values show an increase over tenfold without any subsequent filling of the craters. The growth of the metallic erosion is largely caused by a greater crater diameter. The erosion resistance of metals enhances in the following series: Ti-Zr-Co-Ni-Fe, Hf-V-Nb-Mo-Cr-Ta-W-Cu

  17. Parametric study of laser photovoltaic energy converters

    Science.gov (United States)

    Walker, G. H.; Heinbockel, J. H.

    1987-01-01

    Photovoltaic converters are of interest for converting laser power to electrical power in a space-based laser power system. This paper describes a model for photovoltaic laser converters and the application of this model to a neodymium laser silicon photovoltaic converter system. A parametric study which defines the sensitivity of the photovoltaic parameters is described. An optimized silicon photovoltaic converter has an efficiency greater than 50 percent for 1000 W/sq cm of neodymium laser radiation.

  18. Systematic study of formation and crystal structure of 3d-transition metal nitrides synthesized in a supercritical nitrogen fluid under 10 GPa and 1800 K using diamond anvil cell and YAG laser heating

    International Nuclear Information System (INIS)

    Hasegawa, Masashi; Yagi, Takehiko

    2005-01-01

    Syntheses of 3d-transition metal (Ti-Cu) nitrides have been tried in a supercritical nitrogen fluid at high pressures (about 10 GPa) and high temperatures (about 1800 K) using diamond anvil cell and YAG laser heating system. Nitrides, such as TiN, VN, CrN, Mn 3 N 2 , Fe 2 N, Co 2 N and Ni 3 N have been successfully synthesized easily by a simple direct nitriding reaction between metal and fluid nitrogen in a short time, while any Cu nitrides were not synthesized. These results indicate that the ratio of nitrogen to metal, N/M, of the nitride decreases from 1 to 0 with the sequence from the early transition metal nitrides to the late transition metal ones. The systematic change of the N/M ratio and crystal structure of the 3d-transition metal nitrides is discussed and interpreted on the basis of the electron arrangement of the 3d-transition metal which is relevant to its coordination number

  19. The dynamics of the laser-induced metal-semiconductor phase transition of samarium sulfide (SmS)

    International Nuclear Information System (INIS)

    Kaempfer, Tino

    2009-01-01

    The present thesis is dedicated to the experimental study of the metal-semiconductor phase transition of samarium sulfide (SmS): Temperature- and time-resolved experiments on the characterization of the phase transition of mixed-valence SmS samples (M-SmS) are presented. The measurement of the dynamics of the laser-induced phase transition pursues via time-resolved ultrashort-time microscopy and by X-ray diffraction with sub-picosecond time resolution. The electronic and structural processes, which follow an excitation of M-SmS with infrared femtosecond laser pulses, are physically interpreted on the base of the results obtained in this thesis and model imaginations. [de

  20. Laser spectroscopy of the 109.1-nm transition in neutral Cs

    International Nuclear Information System (INIS)

    Dimiduk, D.P.; Young, J.F.; Harris, S.E.; Pedrotti, K.D.

    1986-01-01

    Certain core-excited quartet levels in alkali-like atoms and ions, termed quasi-metastable, have slow autoionizing rates and comparable (relatively fast for quartets) VUV radiative rates. This circumstance, desirable for laser transitions, is due to angular momentum and parity selection rules on these quarters and the doublets to which they may couple via the spin-orbit interaction. The 109.1-nm transition is between Cs(5p/sup 5/5d6s)/sup 4/P/sub 5/2/ and Cs(5p/sup 6/5d)/sup 2/D and is a prototype of a class of transitions which originate on quasi-metastable levels. It has been observed in emission from a pulsed hollow-cathode discharge. Here the authors report an experiment using the same discharge to populate the lower level of this transition; tunable VUV radiation, generated by four-wave mixing, is used to make absorption measurements at near Doppler-limited resolution. From these data the authors measure accurately the fine-structure splitting of the transition, estimate the oscillator strength and hyperfine splitting, and thus confirm the identity of the transition. The VUV radiation was generated via a resonant process in Zn vapor and then directed through the pulsed hollow cathode. The scanned VUV was absorbed by the excited Cs(5p/sup 6/5d)/sup 2/D atoms in the discharge. The authors measured separately the excited atom populations via absorption on the 5d-nf transitions, thus measuring the NL product of the lower levels. By varying the discharge current, the absorption was measured as a function of the lower level NL yielding curves of growth for these transitions. Careful study of these curves yielded the oscillator strengths of both components of this transition and an estimate of the hyperfine broadening of the upper level. The measured oscillator strengths agreed well with the authors' calculations using the code RCN/RCG

  1. X-ray laser studies at LLE

    International Nuclear Information System (INIS)

    Yaakobi, B.; Boehly, T.; Audebert, P.; Epstein, R.; Boswell, B.; Richardson, M.C.; Soures, J.M.; Shvarts, D.

    1988-01-01

    New target geometries for collisional excitation X-ray laser experiments (in nickel) were proposed, analyzed, and experimentally studied on the GDL laser. Experiments using a short line focus lens with new target geometries showed general agreement with predictions. The new geometries are designed to yield a higher gain and reduced refraction due to 1) a higher plasma density, 2) a wider lateral density profile, and 3) a concave lateral density profile. These new geometries were a) two parallel exploding (thin) foils, irradiated from one side only, b) two ablating (thick) foils, one of which is irradiated on its inner face, and c) an exploding foil in front of an ablating foil, irradiated by a single laser beam incident on the thin foil. The experiments with a long line focus are in progress. The intensity ratio of Ne-like and F-like Ni lines is used to deduce the temperature, and these results together with the absolute intensity yields the density profile. The results show improvement achieved with the new target geometries: the density is higher (leading to a higher gain), and the concave density profile results in collimation rather than divergence of the X-ray laser beam. Theoretical developments included development of a ray-tracing code for an amplifying medium of varying (e.g., collimating) lateral density profile (results using this code are shown for convex as well as concave lateral density profiles) and prediction of high gain on new type transitions in neonlike ions, involving the excitation of an inner (2s) electron

  2. Study on guided waves in semiconductor lasers

    International Nuclear Information System (INIS)

    Pudensi, M.A.A.

    1980-01-01

    In This work we studied the guided waves in semiconductor lasers. In the first part we carried on the experimental measurements on lasers with stripe nonorthogonal to the mirrors. In the second part we developed a matrix method for the study of propagation and reflection of guided waves in lasers. (author) [pt

  3. Biomedical Studies with the Free Electron Laser

    Science.gov (United States)

    1989-05-15

    and Berns. Mi. W. User pitotora- 26. Kestel. D.. And Chou. T. C. Tumer -localizing components of the ptirph% rin diation therapy of cancer following... cancer , (2) laser tissue interactions for the study of atherosclerosis, (3) pulsed laser effects on the eye, (4) laser application in genetic...these studies. Please refer to the appropriate article/abstract for further detail. 1. Dye plus laser photosensitization of cancer . Significant

  4. Fluorescence Imaging Study of Transition in Underexpanded Free Jets

    Science.gov (United States)

    Wilkes, Jennifer A.; Danehy, Paul M.; Nowak, Robert J.

    2005-01-01

    Planar laser-induced fluorescence (PLIF) is demonstrated to be a valuable tool for studying the onset of transition to turbulence. For this study, we have used PLIF of nitric oxide (NO) to image underexpanded axisymmetric free jets issuing into a low-pressure chamber through a smooth converging nozzle with a sonic orifice. Flows were studied over a range of Reynolds numbers and nozzle-exit-to-ambient pressure ratios with the aim of empirically determining criteria governing the onset of turbulence. We have developed an image processing technique, involving calculation of the standard deviation of the intensity in PLIF images, in order to aid in the identification of turbulence. We have used the resulting images to identify laminar, transitional and turbulent flow regimes. Jet scaling parameters were used to define a rescaled Reynolds number that incorporates the influence of a varying pressure ratio. An empirical correlation was found between transition length and this rescaled Reynolds number for highly underexpanded jets.

  5. Modeling multipulsing transition in ring cavity lasers with proper orthogonal decomposition

    International Nuclear Information System (INIS)

    Ding, Edwin; Shlizerman, Eli; Kutz, J. Nathan

    2010-01-01

    A low-dimensional model is constructed via the proper orthogonal decomposition (POD) to characterize the multipulsing phenomenon in a ring cavity laser mode locked by a saturable absorber. The onset of the multipulsing transition is characterized by an oscillatory state (created by a Hopf bifurcation) that is then itself destabilized to a double-pulse configuration (by a fold bifurcation). A four-mode POD analysis, which uses the principal components, or singular value decomposition modes, of the mode-locked laser, provides a simple analytic framework for a complete characterization of the entire transition process and its associated bifurcations. These findings are in good agreement with the full governing equation.

  6. Dynamics of laterally coupled semiconductor lasers: transition to chaos

    NARCIS (Netherlands)

    Yousefi, M.; Barsella, A.; Lenstra, D.; Lenstra, D.; Morthier, G.; Erneux, T.; Pessa, M.

    2004-01-01

    A method for the investigation of the dynamics of two semiconductor lasers, grown side-by-side on the same wafer to enhance the lateral optical coupling, is presented. Using steady state analysis, parameter regimes of relevant dynamics are identified. This is completed by a spectral analysis, were

  7. Kinetics studies following state-selective laser excitation

    International Nuclear Information System (INIS)

    Keto, J.W.

    1994-04-01

    The objective of this contract was the study of state-to-state, electronic energy transfer reactions relevant to the excited state chemistry observed in discharges. We studied deactivation reactions and excitation transfer in collisions of excited states of xenon and krypton atoms with Ar, Kr, Xe and chlorine. The reactant states were excited selectively in two-photon transitions using tunable u.v. and v.u.v. lasers. Excited states produced by the collision were observed by their fluorescence. Reaction rates were measured by observing the time dependent decay of signals from reactant and product channels. In addition we measured interaction potentials of the reactants by laser spectroscopy where the laser induced fluorescence or ionization is measured as a function of laser wavelength (excitation spectra) or by measuring fluorescence spectra at fixed laser frequencies with monochromators. The spectra were obtained in the form of either lineshapes or individual lines from rovibrational transitions of bound states. Our research then required several categories of experiments in order to fully understand a reaction process: 1. High resolution laser spectroscopy of bound molecules or lineshapes of colliding pairs is used to determine potential curves for reactants. 2. Direct measurements of state-to-state reaction rates were measured by studying the time dependent loss of excited reactants and the time dependent formation of products. 3. The energy selectivity of a laser can be used to excite reactants on an excited surface with controlled internuclear configurations. For free states of reactants (as exist in a gas cell) this has been termed laser assisted reactions, while for initially bound states (as chemically bound reactants or dimers formed in supersonic beams) the experiments have been termed photo-fragmentation spectroscopy

  8. Scaling studies of solar pumped lasers

    Science.gov (United States)

    Christiansen, W. H.; Chang, J.

    1985-01-01

    A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.

  9. Laser induced popcornlike conformational transition of nanodiamond as a nanoknife

    International Nuclear Information System (INIS)

    Chang, C.-C.; Chen, P.-H.; Chu, H.-L.; Lee, T.-C.; Chou, C.-C.; Chao, J.-I; Su, C.-Y.; Chen, J.S.; Tsai, J.-S.; Tsai, C.-M.; Ho, Y.-P.; Sun, K.W.; Cheng, C.-L.; Chen, F.-R.

    2008-01-01

    Nanodiamond (ND) is surrounded by layers of graphite on its surface. This unique structure feature creates unusual fluorescence spectra, which can be used as an indicator to monitor its surface modification. Meanwhile, the impurity, nitroso (C-N=O) inside the ND can be photolyzed by two-photon absorption, releasing NO to facilitate the formation of a sp 3 diamond structure in the core of ND and transforming it into a sp 2 graphite structure. Such a conformational transition enlarges the size of ND from 8 to 90 nm, resulting in a popcornlike structure. This transition reaction may be useful as nanoknives in biomedical application

  10. Studying antimatter with laser precision

    CERN Multimedia

    Katarina Anthony

    2012-01-01

    The next generation of antihydrogen trapping devices, ALPHA-2, is moving into CERN’s Antiproton Decelerator (AD) hall. This brand-new experiment will allow the ALPHA collaboration to conduct studies of antimatter with greater precision. ALPHA spokesperson Jeffrey Hangst was recently awarded a grant by the Carlsberg Foundation, which will be used to purchase equipment for the new experiment.   A 3-D view of the new magnet (in blue) and cryostat. The red lines show the paths of laser beams. LHC-type current leads for the superconducting magnets are visible on the top-right of the image. The ALPHA collaboration has been working to trap and study antihydrogen since 2006. Using antiprotons provided by CERN’s Antiproton Decelerator (AD), ALPHA was the first experiment to trap antihydrogen and to hold it long enough to study its properties. “The new ALPHA-2 experiment will use integrated lasers to probe the trapped antihydrogen,” explains Jeffrey Hangst, ALP...

  11. Oxygen auroral transition laser system excited by collisional and photolytic energy transfer

    International Nuclear Information System (INIS)

    Murray, J.R.; Powell, H.T.; Rhodes, C.K.

    1975-06-01

    The properties of laser media involving the auroral transition of atomic oxygen and analogous systems are examined. A discussion of the atomic properties, collisional mechanisms, excitation processes, and collisionally induced radiative phenomena is given. Crossing phenomena play a particularly important role in governing the dynamics of the medium

  12. Charge exchange induced X-ray transitions of hollow ions in laser field ionized plasmas

    International Nuclear Information System (INIS)

    Rosmej, F.B.; Hoffmann, D.H.H.; Faenov, A. Ya.; Pikuz, T.A.; Magunov, A.I.; Skobelev, I.Yu.; Auguste, T.; D'Oliveira, P.; Hulin, S.; Monot, P.

    2000-01-01

    Double electron charge exchange is proposed for the formation of hollow He-like ions when laser field ionized nuclei penetrate into the residual gas. Using transitions from different configurations in hollow ions a method for the determination of the electron temperature in the long lasting recombination phase is developed

  13. b-dipole transitions in trans-HOCO observed by far infrared laser magnetic resonance

    International Nuclear Information System (INIS)

    Sears, T.J.; Radford, H.E.; Moore, M.A.

    1993-01-01

    Far infrared laser magnetic resonance spectroscopy is used to measure components of 12 rotational transitions in the ground state of the HOCO radical. The transitions are all b-dipole in character in contrast to the a-dipole rotational spectrum previously reported [Radford, Wei, and Sears, J. Chem. Phys. 97, 3989 (1992)]. The new data determine the A rotational constant to high precision and allow the determination of several centrifugal distortion constants for the first time. The hyperfine coupling in the radical leads to observable splittings in several of the observed transitions and these are used to estimate two of the four expected nonzero hyperfine parameters in the radical

  14. Transition from diamagnetic to ferromagnetic state in laser ablated nitrogen doped ZnO thin films

    Directory of Open Access Journals (Sweden)

    Kajal Jindal

    2015-02-01

    Full Text Available Transition from room temperature diamagnetic to ferromagnetic state in N doped ZnO (ZnO:N films grown by pulsed laser deposition with tunable energy density has been identified. ZnO:N films deposited with moderate laser energy density of 2.5 J/cm2 are single phase and nearly defect free having N dopant substitution at O sites in ZnO lattice, exhibiting intrinsic ferromagnetism. When energy density reduces (<2.5 J/cm2, defects in ZnO:N film degrades ferromagnetism and exhibit diamagnetic phase when grown at energy density of 1.0 J/cm2. Growth kinetics, which in turn depends on laser energy density is playing important role in making transition from ferromagnetic to diamagnetic in ZnO:N films.

  15. Theoretical studies of solar pumped lasers

    Science.gov (United States)

    Harries, Wynford L.

    1990-01-01

    One concept for collecting solar energy is to use large solar collectors and then use lasers as energy converters whose output beams act as transmission lines to deliver the energy to a destination. The efficiency of the process would be improved if the conversion could be done directly using solar pumped lasers, and the possibility of making such lasers is studied. There are many applications for such lasers, and these are examined. By including the applications first, the requirements for the lasers will be more evident. They are especially applicable to the Space program, and include cases where no other methods of delivering power seem possible. Using the lasers for conveying information and surveillance is also discussed. Many difficulties confront the designer of an efficient system for power conversion. These involve the nature of the solar spectrum, the method of absorbing the energy, the transfer of power into laser beams, and finally, the far field patterns of the beams. The requirements of the lasers are discussed. Specific laser configurations are discussed. The thrust is into gas laser systems, because for space applications, the laser could be large, and also the medium would be uniform and not subject to thermal stresses. Dye and solid lasers are treated briefly. For gas lasers, a chart of the various possibilities is shown, and the various families of gas lasers divided according to the mechanisms of absorbing solar radiation and of lasing. Several specific models are analyzed and evaluated. Overall conclusions for the program are summarized, and the performances of the lasers related to the requirements of various applications.

  16. Diode laser operating on an atomic transition limited by an isotope ⁸⁷Rb Faraday filter at 780 nm.

    Science.gov (United States)

    Tao, Zhiming; Hong, Yelong; Luo, Bin; Chen, Jingbiao; Guo, Hong

    2015-09-15

    We demonstrate an extended cavity Faraday laser system using an antireflection-coated laser diode as the gain medium and the isotope (87)Rb Faraday anomalous dispersion optical filter (FADOF) as the frequency selective device. Using this method, the laser wavelength works stably at the highest transmission peak of the isotope (87)Rb FADOF over the laser diode current from 55 to 140 mA and the temperature from 15°C to 35°C. Neither the current nor the temperature of the laser diode has significant influence on the output frequency. Compared with previous extended cavity laser systems operating at frequencies irrelevant to spectacular atomic transition lines, the laser system realized here provides a stable laser source with the frequency operating on atomic transitions for many practical applications.

  17. Dual-axis vapor cell for simultaneous laser frequency stabilization on disparate optical transitions

    Science.gov (United States)

    Jayakumar, Anupriya; Plotkin-Swing, Benjamin; Jamison, Alan O.; Gupta, Subhadeep

    2015-07-01

    We have developed a dual-axis ytterbium (Yb) vapor cell and used it to simultaneously address the two laser cooling transitions in Yb at wavelengths 399 nm and 556 nm, featuring the disparate linewidths of 2π × 29 MHz and 2π × 182 KHz, respectively. By utilizing different optical paths for the two wavelengths, we simultaneously obtain comparable optical densities suitable for saturated absorption spectroscopy for both the transitions and keep both the lasers frequency stabilized over several hours. We demonstrate that by appropriate control of the cell temperature profile, two atomic transitions differing in relative strength across a large range of over three orders of magnitude can be simultaneously addressed, making the device adaptable to a variety of spectroscopic needs. We also show that our observations can be understood with a simple theoretical model of the Yb vapor.

  18. Dual-axis vapor cell for simultaneous laser frequency stabilization on disparate optical transitions

    Energy Technology Data Exchange (ETDEWEB)

    Jayakumar, Anupriya, E-mail: anupriya@uw.edu; Plotkin-Swing, Benjamin; Jamison, Alan O.; Gupta, Subhadeep [Department of Physics, University of Washington, P.O. Box 351560, Seattle, Washington 98195-1560 (United States)

    2015-07-15

    We have developed a dual-axis ytterbium (Yb) vapor cell and used it to simultaneously address the two laser cooling transitions in Yb at wavelengths 399 nm and 556 nm, featuring the disparate linewidths of 2π × 29 MHz and 2π × 182 KHz, respectively. By utilizing different optical paths for the two wavelengths, we simultaneously obtain comparable optical densities suitable for saturated absorption spectroscopy for both the transitions and keep both the lasers frequency stabilized over several hours. We demonstrate that by appropriate control of the cell temperature profile, two atomic transitions differing in relative strength across a large range of over three orders of magnitude can be simultaneously addressed, making the device adaptable to a variety of spectroscopic needs. We also show that our observations can be understood with a simple theoretical model of the Yb vapor.

  19. Two-photon transitions driven by a combination of diode and femtosecond lasers.

    Science.gov (United States)

    Moreno, Marco P; Nogueira, Giovana T; Felinto, Daniel; Vianna, Sandra S

    2012-10-15

    We report on the combined action of a cw diode laser and a train of ultrashort pulses when each of them drives one step of the 5S-5P-5D two-photon transition in rubidium vapor. The fluorescence from the 6P(3/2) state is detected for a fixed repetition rate of the femtosecond laser while the cw-laser frequency is scanned over the rubidium D(2) lines. This scheme allows for a velocity selective spectroscopy in a large spectral range including the 5D(3/2) and 5D(5/2) states. The results are well described in a simplified frequency domain picture, considering the interaction of each velocity group with the cw laser and a single mode of the frequency comb.

  20. High Speed Pump-Probe Apparatus for Observation of Transitional Effects in Ultrafast Laser Micromachining Processes

    Directory of Open Access Journals (Sweden)

    Ilya Alexeev

    2015-12-01

    Full Text Available A pump-probe experimental approach has been shown to be a very efficient tool for the observation and analysis of various laser matter interaction effects. In those setups, synchronized laser pulses are used to create an event (pump and to simultaneously observe it (probe. In general, the physical effects that can be investigated with such an apparatus are restricted by the temporal resolution of the probe pulse and the observation window. The latter can be greatly extended by adjusting the pump-probe time delay under the assumption that the interaction process remains fairly reproducible. Unfortunately, this assumption becomes invalid in the case of high-repetition-rate ultrafast laser material processing, where the irradiation history strongly affects the ongoing interaction process. In this contribution, the authors present an extension of the pump-probe setup that allows to investigate transitional and dynamic effects present during ultrafast laser machining performed at high pulse repetition frequencies.

  1. PUREX transition project case study

    International Nuclear Information System (INIS)

    Jasen, W.G.

    1996-01-01

    In December 1992, the US Department of Energy (DOE) directed that the Plutonium-Uranium Extraction (PUREX) Plant be shut down and deactivated because it was no longer needed to support the nation's production of weapons-grade plutonium. The PUREX/UO 2 Deactivation Project will establish a safe and environmentally secure configuration for the facility and preserve that configuration for 10 years. The 10-year span is used to predict future maintenance requirements and represents the estimated time needed to define, authorize, and initiate the follow-on decontamination and decommissioning activities. Accomplishing the deactivation project involves many activities. Removing major hazards, such as excess chemicals, spent fuel, and residual plutonium are major goals of the project. The scope of the PUREX Transition Project is described within

  2. The Carolina Autism Transition Study (CATS)

    Science.gov (United States)

    2017-07-01

    AWARD NUMBER: W81XWH-15-1-0093 TITLE: The Carolina Autism Transition Study (CATS) PRINCIPAL INVESTIGATOR: Laura Carpenter, MD RECIPIENT...Carolina Autism Transition Study (CATS) 5b. GRANT NUMBER W81XWH-15-1-0093 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Laura Carpenter...provides a description of the Year 2 progress made and plans for Year 3 for the project entitled “The Carolina Autism Transition Study (CATS).” The goal of

  3. Laser-driven hydrothermal process studied with excimer laser pulses

    Science.gov (United States)

    Mariella, Raymond; Rubenchik, Alexander; Fong, Erika; Norton, Mary; Hollingsworth, William; Clarkson, James; Johnsen, Howard; Osborn, David L.

    2017-08-01

    Previously, we discovered [Mariella et al., J. Appl. Phys. 114, 014904 (2013)] that modest-fluence/modest-intensity 351-nm laser pulses, with insufficient fluence/intensity to ablate rock, mineral, or concrete samples via surface vaporization, still removed the surface material from water-submerged target samples with confinement of the removed material, and then dispersed at least some of the removed material into the water as a long-lived suspension of nanoparticles. We called this new process, which appears to include the generation of larger colorless particles, "laser-driven hydrothermal processing" (LDHP) [Mariella et al., J. Appl. Phys. 114, 014904 (2013)]. We, now, report that we have studied this process using 248-nm and 193-nm laser light on submerged concrete, quartzite, and obsidian, and, even though light at these wavelengths is more strongly absorbed than at 351 nm, we found that the overall efficiency of LDHP, in terms of the mass of the target removed per Joule of laser-pulse energy, is lower with 248-nm and 193-nm laser pulses than with 351-nm laser pulses. Given that stronger absorption creates higher peak surface temperatures for comparable laser fluence and intensity, it was surprising to observe reduced efficiencies for material removal. We also measured the nascent particle-size distributions that LDHP creates in the submerging water and found that they do not display the long tail towards larger particle sizes that we had observed when there had been a multi-week delay between experiments and the date of measuring the size distributions. This is consistent with transient dissolution of the solid surface, followed by diffusion-limited kinetics of nucleation and growth of particles from the resulting thin layer of supersaturated solution at the sample surface.

  4. Laser-induced microscopic phase-transition on an ionic liquid

    International Nuclear Information System (INIS)

    Iguchi, Natsuki; Datta, Alokmay; Yoshikawa, Kenichi; Ma Yue

    2009-01-01

    Nematic-isotropic transition is induced in a 5 μm 'droplet' within an oriented bulk of a mixture of a liquid crystalline material with a room-temperature ionic liquid, by a laser working at 532 nm with an output power of 200 mW and a beam diameter of 1 μm. No microscopic phase transition is observed either in absence of the ionic liquid or at the other wavelength of 1064 nm, available to the Nd-YAG laser. This indicates the essential role on a resonant transfer of energy to the ionic liquid from the laser radiation, which is subsequently transferred to the liquid crystal. Spectroscopy of the pure liquid crystal and ionic liquid samples confirms this concept. Spatio-temporal image of the droplet growth shows, however, that the phase transition remains confined within the microscopic domain for the first 50 s, and then spreads out rapidly. Since resonant, quantum transitions between molecular levels takes place in less than microseconds, the about seven orders of magnitude slowing down of energy transfer observed here suggests unique hierarchical dynamics including the coupling between the intra-molecular motions in the ionic liquid and the inter-molecular forces between ionic liquid and liquid crystal.

  5. Design study of laser fusion rocket

    International Nuclear Information System (INIS)

    Nakashima, Hideki; Shoyama, Hidetoshi; Kanda, Yukinori

    1991-01-01

    A design study was made on a rocket powered by laser fusion. Dependence of its flight performance on target gain, driver repetition rate and fuel composition was analyzed to obtain optimal design parameters of the laser fusion rocket. The results indicate that the laser fusion rocket fueled with DT or D 3 He has the potential advantages over other propulsion systems such as fission rocket for interplanetary travel. (author)

  6. Density Transition Based Self-Focusing of cosh-Gaussian Laser Beam in Plasma with Linear Absorption

    International Nuclear Information System (INIS)

    Kant, Niti; Wani, Manzoor Ahmad

    2015-01-01

    Density transition based self-focusing of cosh-Gaussian laser beam in plasma with linear absorption has been studied. The field distribution in the plasma is expressed in terms of beam width parameter, decentered parameter, and linear absorption coefficient. The differential equation for the beam width parameter is solved by following Wentzel–Kramers–Brillouin (WKB) and paraxial approximation through parabolic wave equation approach. The behaviour of beam width parameter with dimensionless distance of propagation is studied at optimum values of plasma density, decentered parameter and with different absorption levels in the medium. The results reveal that these parameters can affect the self-focusing significantly. (paper)

  7. The development of laser ignited deflagration-to-detonation transition (DDT) detonators and pyrotechnic actuators

    Energy Technology Data Exchange (ETDEWEB)

    Merson, J.A.; Salas, F.J.; Harlan, J.G.

    1993-11-01

    The use of laser ignited explosive components has been recognized as a safety enhancement over existing electrical explosive devices (EEDs). Sandia has been pursuing the development of optical ordnance for many years with recent emphasis on developing optical deflagration-to-detonation (DDT) detonators and pyrotechnic actuators. These low energy optical ordnance devices can be ignited with either a semiconductor diode laser, laser diode arrays or a solid state rod laser. By using a semiconductor laser diode, the safety improvement can be made without sacrificing performance since the input energy required for the laser diode and the explosive output are similar to existing electrical systems. The use of higher powered laser diode arrays or rod lasers may have advantages in fast DDT applications or lossy optical environments such as long fiber applications and applications with numerous optical connectors. Recent results from our continued study of optical ignition of explosive and pyrotechnic materials are presented. These areas of investigation can be separated into three different margin categories: (1) the margin relative to intended inputs (i.e. powder performance as a function of laser input variation), (2) the margin relative to anticipated environments (i.e. powder performance as a function of thermal environment variation), and (3) the margin relative to unintended environments (i.e. responses to abnormal environments or safety).

  8. New cascade laser transitions in CH2F2 pumped with the 9R32 line of a cw CO2 laser

    International Nuclear Information System (INIS)

    Nieswand, C.

    1991-11-01

    New cascade laser transitions of 12 CH 2 F 2 at 172.50μm, 208.83μm, 220.44μm, 223.99μm,and 250.61μm are reported. A waveguide FIR laser was pumped with a quasi cw 12 C 16 O 2 laser operating on the 9R32 line. Together with the already known lines at 184.3μm, 196.1μm and 235.9μm, the laser lines can be assigned to rotational transitions in the ν 9 vibrational band of 12 CH 2 F 2 and to refill transitions of the vibrational ground state ν 0 . 1 fig., 2 tabs., 6 refs. (author)

  9. Transition probabilities for lines of Cr II, Na II and Sb I by laser produced plasma atomic emission spectroscopy

    International Nuclear Information System (INIS)

    Gonzalez, A. M.; Ortiz, M.; Campos, J.

    1995-01-01

    Absolute transition probabilities for lines of CR II, Na II and Sb I were determined by emission spectroscopy of laser induced plasmas. the plasma was produced focusing the emission of a pulsed Nd-Yag laser on solid samples containing the atom in study. the light arising from the plasma region was collected by and spectrometer. the detector used was a time-resolved optical multichannel analyzer (OMA III EG and G). The wavelengths of the measured transitions range from 2000 sto 4100 A. The spectral resolution of the system was 0. 2 A. The method can be used in insulators materials as Cl Na crystals and in metallic samples as Al-Cr and Sn-Sn alloys. to avoid self-absorption effects the alloys were made with low Sb or Cr content. Relative transition probabilities have been determined from measurements of emission-line intensities and were placed on an absolute scale by using, where possible, accurate experimental lifetime values form the literature or theoretical data. From these measurements, values for plasma temperature (8000-24000 K), electron densities (∼∼ 10''16 cm ''-3) and self-absorption coefficients have been obtained. (Author) 56 refs

  10. Transition probabilities for lines of Cr II, Na II and Sb I by laser produced plasma atomic emission spectroscopy

    International Nuclear Information System (INIS)

    Gonzalez, A.M.; Ortiz, M.; Campos, J.

    1995-09-01

    Absolute transition probabilities for lines of Cr II, Na II and Sb I were determined by emission spectroscopy of laser induced plasmas. The plasma was produced focusing the emission of a pulsed Nd-Yag laser on solid samples containing the atom in study. The light arising from the plasma region was collected by and spectrometer. the detector used was a time-resolved optical multichannel analyzer (OMA III EG and G). The wavelengths of the measured transitions range from 2000 to 4100 A. The spectral resolution of the system was 0.2 A. The method can be used in insulators materials as Cl Na crystals and in metallic samples as Al-Cr and Sn-Sb alloys. To avoid self-absorption effects the alloys were made with low Sb or Cr content. Relative transition probabilities have been determined from measurements of emission-line intensities and were placed on an absolute scale by using, where possible, accurate experimental lifetime values form the literature or theoretical data. From these measurements, values for plasma temperature (8000-24000K), electron densities (approx 10 ''16 cm''-3) and self-absorption coefficients have been obtained

  11. Imaging ultrafast excited state pathways in transition metal complexes by X-ray transient absorption and scattering using X-ray free electron laser source

    DEFF Research Database (Denmark)

    Chen, Lin X; Shelby, Megan L; Lestrange, Patrick J

    2016-01-01

    This report will describe our recent studies of transition metal complex structural dynamics on the fs and ps time scales using an X-ray free electron laser source, Linac Coherent Light Source (LCLS). Ultrafast XANES spectra at the Ni K-edge of nickel(ii) tetramesitylporphyrin (NiTMP) were measured...... on the low-energy shoulder of the edge, which is aided by the computation of X-ray transitions for postulated excited electronic states. The observed and computed inner shell to valence orbital transition energies demonstrate and quantify the influence of the electronic configuration on specific metal...

  12. Enhanced relativistic self-focusing of Hermite-cosh-Gaussian laser beam in plasma under density transition

    International Nuclear Information System (INIS)

    Nanda, Vikas; Kant, Niti

    2014-01-01

    Enhanced and early relativistic self-focusing of Hermite-cosh-Gaussian (HChG) beam in the plasmas under density transition has been investigated theoretically using Wentzel-Kramers-Brillouin and paraxial ray approximation for mode indices m=0, 1, and 2. The variation of beam width parameter with normalized propagation distance for m=0, 1, and 2 is reported, and it is observed that strong self-focusing occurs as the HChG beam propagates deeper inside the nonlinear medium as spot size shrinks due to highly dense plasmas and the results are presented graphically. A comparative study between self-focusing of HChG beam in the presence and absence of plasmas density transition is reported. The dependency of beam width parameter on the normalized propagation distance for different values of decentered parameter “b” has also been presented graphically. For m=0 and 1, strong self-focusing is reported for b=1.8, and for m=2 and b=1.8, beam gets diffracted. The results obtained indicate the dependency of the self-focusing of the HChG beam on the selected values of decentered parameter. Moreover, proper selection of decentered parameter results strong self-focusing of HChG beam. Stronger self-focusing of laser beam is observed due to the presence of plasma density transition which might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, etc

  13. Enhanced relativistic self-focusing of Hermite-cosh-Gaussian laser beam in plasma under density transition

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, Vikas; Kant, Niti, E-mail: nitikant@yahoo.com [Department of Physics, Lovely Professional University, Phagwara 144411, Punjab (India)

    2014-04-15

    Enhanced and early relativistic self-focusing of Hermite-cosh-Gaussian (HChG) beam in the plasmas under density transition has been investigated theoretically using Wentzel-Kramers-Brillouin and paraxial ray approximation for mode indices m=0, 1, and 2. The variation of beam width parameter with normalized propagation distance for m=0, 1, and 2 is reported, and it is observed that strong self-focusing occurs as the HChG beam propagates deeper inside the nonlinear medium as spot size shrinks due to highly dense plasmas and the results are presented graphically. A comparative study between self-focusing of HChG beam in the presence and absence of plasmas density transition is reported. The dependency of beam width parameter on the normalized propagation distance for different values of decentered parameter “b” has also been presented graphically. For m=0 and 1, strong self-focusing is reported for b=1.8, and for m=2 and b=1.8, beam gets diffracted. The results obtained indicate the dependency of the self-focusing of the HChG beam on the selected values of decentered parameter. Moreover, proper selection of decentered parameter results strong self-focusing of HChG beam. Stronger self-focusing of laser beam is observed due to the presence of plasma density transition which might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, etc.

  14. Phase Transitions, Diffraction Studies and Marginal Dimensionality

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1985-01-01

    Continuous phase transitions and the associated critical phenomena have been one of the most active areas of research in condensed matter physics for several decades. This short review is only one cut through this huge subject and the author has chosen to emphasize diffraction studies as a basic ...

  15. Laser imprint reduction with a shaping pulse, oscillatory Richtmyer-Meshkov to Rayleigh-Taylor transition and other coherent effects in plastic-foam targets

    International Nuclear Information System (INIS)

    Metzler, N.; Velikovich, A.L.; Schmitt, A.J.; Karasik, M.; Serlin, V.; Mostovych, A.N.; Obenschain, S.P.; Gardner, J.H.; Aglitskiy, Y.

    2003-01-01

    A substantial reduction of the laser imprint with a short, low-energy 'shaping' laser pulse incident upon a foam-plastic sandwich target prior to the main laser pulse has been demonstrated to be possible [Metzler et al., Phys. Plasmas 9, 5050 (2002)]. Nonuniformity of this shaping pulse, however, produces standing sonic waves in the target. Laser-imprinted seeds for the Rayleigh-Taylor (RT) instability growth then emerge from the interaction of these waves with the strong shock wave launched by the drive laser pulse. Such coherent interaction between different waves and modes perturbed at the same wavelength is shown to be important in a variety of situations relevant to the inertial confinement fusion studies. As an example, an oscillatory transition from the classical Richtmyer-Meshkov shock-interface instability development to the RT growth exhibiting a characteristic phase reversal in a target of finite thickness is described. Another example refers to the feedout mechanism of seeding the perturbations that come from the nonuniformities of the rear (inner) surface of the laser target. The coherent interaction between the strong shock wave from the main laser pulse and the rippled rarefaction wave produced by a low-intensity foot of the pulse produces observable effects, such as an extra phase reversal compared to the case of no foot. Some of these predictions are shown to be consistent with our new experimental results obtained in the feedout geometry on the Nike laser facility [S. P. Obenschain et al. Phys. Plasmas 3, 2098 (1996)

  16. Laser-induced fluorescences due to quadrupole moment transition and Stark effect in a He glow discharge

    International Nuclear Information System (INIS)

    Sakai, Hisashi; Takiyama, Ken; Kimura, Masahiko; Yamasaki, Motokuni; Fujita, Toshiaki; Oda, Toshiatsu; Kawasaki, Ken.

    1993-01-01

    The electric quadrupole moment transition and the Stark effect are investigated in a He hollow cathode discharge with laser-induced fluorescence method. It is shown that the forbidden transition from 2 1 S to 3 1 D in the negative glow is dominantly due to the quadrupole moment transition. This absorption coefficient is obtained from the laser-induced fluorescence intensity measurement in which the collisional transfers are taken into account. The result agrees with the theoretical coefficient. In the cathode dark space the fluorescence due to the Stark effect is also observed. Spatial distribution of the fluorescence is discussed, compared with the electric field distribution in the dark space. (author)

  17. Measurement of the population densities in Gd atomic vapor using diode laser absorption spectroscopy in UV transitions

    International Nuclear Information System (INIS)

    Kwon, Duck Hee; Jung, E. C.; Ko, Kwang Hoon; Kim, Tack Soo

    2003-01-01

    We report on the ultraviolet laser absorption spectroscopy of atomic Gd at 394-554 nm where two transition lines are place very closely by using a frequency-doubled beam of external-cavity diode laser (ECDL). One is from 999.121 to 26337.071 cm -1 and the other from 0 to 25337.755 cm -1 . If two transition lines are placed closely within a continuous fine tuning range, the real-time measurement of the atomic excitation temperature is possible without any significant time consumption because at least two transition lines originating from different low-lying energy levels need to be investigated for the Boltzmann-plot. Since the spectral difference between the two transitions is only about 0.195 cm -1 (5.85 GHz), it is possible to record both the absorption spectra simultaneously as shown in Fig. 1. But the transition probabilities (or oscillator strengths) of these lines have not been measured accurately yet to the best of our knowledge. We report on the newly measured transition probabilities by analyzing their absorption spectra at known vapor density conditions. The simultaneous measurement of the atomic excitation temperature and the vapor density demonstrated. In addition we present another ultraviolet laser absorption spectroscopy of atomic Gd at 403.540 nm by means of a commercial blue diode laser and investigate the characteristics of the blue diode laser as well.

  18. TRANSITION METAL OXIDES AS MATERIALS FOR ADDITIVE LASER MARKING ON STAINLESS STEEL

    Directory of Open Access Journals (Sweden)

    Mihail Stoyanov Mihalev

    2017-09-01

    Full Text Available The product information plays an important role in the improvement of the manufacturing, allowing the tracking of the part through the full life cycle. Laser marking is one of the most versatile techniques for this purpose. In this paper, a modification of the powder bed selective laser melting for additive laser marking of stainless steel parts is presented. This modification is based on the use of only one transition metal oxide chemically bonded to the stainless steel substrate, without using any additional materials and cleaning substances. The resulting additive coatings, produced from initial MoO3 and WO3 powders, show strong adhesion, high hardness, long durability and a high optical contrast. For estimation of the chemical and structural properties, the Raman and X-Ray Diffraction (XRD spectroscopy have been implemented. A computer model of the process of the laser melting and re-solidification has been developed as well. A comparative analysis of the properties of both (MoO3 and WO3 additive coatings has been performed. An attempt for a qualitative explanation of the thermo-chemical phenomena during the marking process has been undertaken.

  19. Intra-pulse transition between ion acceleration mechanisms in intense laser-foil interactions

    Energy Technology Data Exchange (ETDEWEB)

    Padda, H.; King, M.; Gray, R. J.; Powell, H. W.; Gonzalez-Izquierdo, B.; Wilson, R.; Dance, R. J.; MacLellan, D. A.; Butler, N. M. H.; Capdessus, R.; McKenna, P., E-mail: paul.mckenna@strath.ac.uk [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Stockhausen, L. C. [Centro de Laseres Pulsados (CLPU), Parque Cientifico, Calle del Adaja s/n. 37185 Villamayor, Salamanca (Spain); Carroll, D. C. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Yuan, X. H. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240 (China); Borghesi, M. [Centre for Plasma Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Neely, D. [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom)

    2016-06-15

    Multiple ion acceleration mechanisms can occur when an ultrathin foil is irradiated with an intense laser pulse, with the dominant mechanism changing over the course of the interaction. Measurement of the spatial-intensity distribution of the beam of energetic protons is used to investigate the transition from radiation pressure acceleration to transparency-driven processes. It is shown numerically that radiation pressure drives an increased expansion of the target ions within the spatial extent of the laser focal spot, which induces a radial deflection of relatively low energy sheath-accelerated protons to form an annular distribution. Through variation of the target foil thickness, the opening angle of the ring is shown to be correlated to the point in time transparency occurs during the interaction and is maximized when it occurs at the peak of the laser intensity profile. Corresponding experimental measurements of the ring size variation with target thickness exhibit the same trends and provide insight into the intra-pulse laser-plasma evolution.

  20. Laser isotope separation studies in JAERI

    International Nuclear Information System (INIS)

    Arisawa, Takashi; Shiba, Koreyuki

    1986-01-01

    For uranium enrichment, Japan Atomic Energy Research Institute (JAERI) has been studying atomic vapor laser isotope separation since 1976, in addition to such separation methods as gas diffusion, chemical exchange and gas-dynamic techniques. Studies carried out to date in JAERI is briefly summarized in the first part of the report. Then, some major separation techniques which have been studied in JAERI are outlined, and typical results obtained are presented. A large part is devoted to the multiple-photon photoionization technique, which is commonly known as the atomic laser isotope separation method for uranium enrichment. It has such advantages as 1) very high spectral selectivity for the relevant isotope and 2) highly improved photoionizing effect by means of two- and three-step resonance photoionization processes. Here, the atomic laser isotope separation method is discussed in detail with respect to the evaporation process, energy levels, photoionization, selectivity, photoionization schemes, ion recovery, separation in macroscopic amounts, and separation of trace amounts of isotopes. Typical observed and claculated results related to these subjects are shown. In addition, the report briefly describes some other separation processes including laser induced chemical reaction, multiple photo-dissociation, multiple-photo excitation and UV dissociation, laser induced thermal diffusion, and laser centrifugation. (Nogami, K.)

  1. High sensitivity spectroscopy with tunable diode lasers - detection of O2 quadrupole transitions and 14C

    International Nuclear Information System (INIS)

    Reid, J.

    1981-01-01

    In recent years, tunable lead-salt diode lasers (TDLs) have found widespread application in all fields of infrared spectroscopy. However, most applications of TDLs utilise only the tunability and high resolution of these devices, and few experiments have employed the ability of the TDL to detect very small absorption coefficients. We have developed a laser absorption spectrometer (LAS) which can detect absorption coefficients as small as 10 -6 to 10 -7 m -1 , while retaining the full tunability and resolution of the TDL. This instrument has been used as a point monitoring system for many trace gases of atmospheric significance. In this paper, we describe two additional applications of the LAS: (I) the detection of very weak transitions such as quadrupole lines in oxygen, and (II) the detection of rare isotopes, with 14 C in CO 2 as an example. Details are given in the following sections. (orig.)

  2. Transition between laser absorption dominated regimes in carbon-based plasma

    Directory of Open Access Journals (Sweden)

    K. Hajisharifi

    2017-09-01

    Full Text Available In this work, we investigate the energy absorption enhancement of a laser by adding a variety of light ion species to a primarily carbon-based plasma during the high-power laser interaction with the finite size targets. A developed Particle-In-Cell simulation code is used to study the reduction of laser reflectivity (stimulated backward scatterings in both Brillouin- and Raman-dominated regimes. The simulation is performed in various Carbon-light ion plasmas such as Carbon-Hydrogen, Carbon-Helium, Carbon-Deuterium, and Carbon-Tritium. The results show that, in the optimized condition, the inclusion of light Hydrogen ions into the Carbon-based plasma up to 50%-50% mixture enhances the laser absorption exceeding 20% in the Brillouin regime due to the suppression of laser reflectivity in contract to 4% in the Raman-dominated regime. Moreover, the absorption dominated regime switches from Raman to Brillouin regime by adding 50% of Hydrogen ions to a purely carbon target. The results of this investigation will be applicable to the laser-plasma experiments so long as the laser energy absorption in the Carbon plasma target, the most readily available material in laboratory, is concerned.

  3. Ion beam production and study of radioactive isotopes with the laser ion source at ISOLDE

    Science.gov (United States)

    Fedosseev, Valentin; Chrysalidis, Katerina; Day Goodacre, Thomas; Marsh, Bruce; Rothe, Sebastian; Seiffert, Christoph; Wendt, Klaus

    2017-08-01

    At ISOLDE the majority of radioactive ion beams are produced using the resonance ionization laser ion source (RILIS). This ion source is based on resonant excitation of atomic transitions by wavelength tunable laser radiation. Since its installation at the ISOLDE facility in 1994, the RILIS laser setup has been developed into a versatile remotely operated laser system comprising state-of-the-art solid state and dye lasers capable of generating multiple high quality laser beams at any wavelength in the range of 210-950 nm. A continuous programme of atomic ionization scheme development at CERN and at other laboratories has gradually increased the number of RILIS-ionized elements. At present, isotopes of 40 different elements have been selectively laser-ionized by the ISOLDE RILIS. Studies related to the optimization of the laser-atom interaction environment have yielded new laser ion source types: the laser ion source and trap and the versatile arc discharge and laser ion source. Depending on the specific experimental requirements for beam purity or versatility to switch between different ionization mechanisms, these may offer a favourable alternative to the standard hot metal cavity configuration. In addition to its main purpose of ion beam production, the RILIS is used for laser spectroscopy of radioisotopes. In an ongoing experimental campaign the isotope shifts and hyperfine structure of long isotopic chains have been measured by the extremely sensitive in-source laser spectroscopy method. The studies performed in the lead region were focused on nuclear deformation and shape coexistence effects around the closed proton shell Z = 82. The paper describes the functional principles of the RILIS, the current status of the laser system and demonstrated capabilities for the production of different ion beams including the high-resolution studies of short-lived isotopes and other applications of RILIS lasers for ISOLDE experiments. This article belongs to the Focus on

  4. QED studies using high-power lasers

    International Nuclear Information System (INIS)

    Mattias Marklund

    2010-01-01

    Complete text of publication follows. The event of extreme lasers, which intensities above 10 22 W/cm 2 will be reached on a routine basis, will give us opportunities to probe new aspects of quantum electrodynamics. In particular, the non-trivial properties of the quantum vacuum can be investigated as we reach previously unattainable laser intensities. Effects such as vacuum birefringence and pair production in strong fields could thus be probed. The prospects of obtaining new insights regarding the non-perturbative structure of quantum field theories shows that the next generation laser facilities can be important tool for fundamental physical studies. Here we aim at giving a brief overview of such aspects of high-power laser physics.

  5. Feasibility of Optical Transition Radiation Imaging for Laser-driven Plasma Accelerator Electron-Beam Diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A. H. [Fermilab; Rule, D. W. [Unlisted, US, MD; Downer, M. C. [Texas U.

    2017-10-09

    We report the initial considerations of using linearly polarized optical transition radiation (OTR) to characterize the electron beams of laser plasma accelerators (LPAs) such as at the Univ. of Texas at Austin. The two LPAs operate at 100 MeV and 2-GeV, and they currently have estimated normalized emittances at ~ 1-mm mrad regime with beam divergences less than 1/γ and beam sizes to be determined at the micron level. Analytical modeling results indicate the feasibility of using these OTR techniques for the LPA applications.

  6. 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.

  7. Detroit regional transit study : a study of factors that enable and inhibit effective regional transit.

    Science.gov (United States)

    2014-03-01

    An interdisciplinary team of six faculty members and six students at the University of Detroit Mercy (UDM) conducted a : comprehensive study of the factors enabling or inhibiting development of effective regional transit. Focusing on Metro Detroit an...

  8. Welding with high power fiber lasers - A preliminary study

    International Nuclear Information System (INIS)

    Quintino, L.; Costa, A.; Miranda, R.; Yapp, D.; Kumar, V.; Kong, C.J.

    2007-01-01

    The new generation of high power fiber lasers presents several benefits for industrial purposes, namely high power with low beam divergence, flexible beam delivery, low maintenance costs, high efficiency and compact size. This paper presents a brief review of the development of high power lasers, and presents initial data on welding of API 5L: X100 pipeline steel with an 8 kW fiber laser. Weld bead geometry was evaluated and transition between conduction and deep penetration welding modes was investigated

  9. Coherent transition radiation from a laser wakefield accelerator as an electron bunch diagnostic

    International Nuclear Information System (INIS)

    Tilborg, J. van; Geddes, C.G.R.; Toth, C.; Esarey, E.; Schroeder, C.B.; Martin, M.C.; Hao, Z.; Leemans, W.P.

    2004-01-01

    The observation and modeling of coherent transition radiation from femtosecond laser accelerated electron bunches is discussed. The coherent transition radiation, scaling quadratically with bunch charge, is generated as the electrons transit the plasma-vacuum boundary. Due to the limited transverse radius of the plasma boundary, diffraction effects will strongly modify the angular distribution and the total energy radiated is reduced compared to an infinite transverse boundary. The multi-nC electron bunches, concentrated in a length of a few plasma periods (several tens of microns), experience partial charge neutralization while propagating inside the plasma towards the boundary. This reduces the space-charge blowout of the beam, allowing for coherent radiation at relatively high frequencies (several THz). The charge distribution of the electron bunch at the plasma-vacuum boundary can be derived from Fourier analysis of the coherent part of the transition radiation spectrum. A Michelson interferometer was used to measure the coherent spectrum, and electron bunches with duration on the order of 50 fs (rms) were observed

  10. Impurity studies in fusion devices using laser-fluorescence-spectroscopy

    International Nuclear Information System (INIS)

    Husinsky, W.R.

    1980-08-01

    Resonance fluorescence excitation of neutral atoms using tunable radiation from dye lasers offers a number of unique advantages for impurity studies in fusion devices. Using this technique, it is possible to perform local, time-resolved measurements of the densities and velocity distributions of metallic impurities in fusion devices without disturbing the plasma. Velocities are measured by monitoring the fluorescence intensity while tuning narrow bandwidth laser radiation through the Doppler - broadened absorbtion spectrum of the transition. The knowledge of the velocity distribution of neutral impurities is particularly useful for the determination of impurity introduction mechanisms. The laser fluorescence technique will be described in terms of its application to metallic impurities in fusion devices and related laboratory experiments. Particular attention will be given to recent results from the ISX-B tokamak using pulsed dye lasers where detection sensitivities for neutral Fe of 10 6 atoms/cm 3 with a velocity resolution of 600 m/sec (0.1 eV) have been achieved. Techniques for exciting plasma particles (H,D) will also be discussed

  11. Theoretical studies of solar-pumped lasers

    Science.gov (United States)

    Harries, W. L.

    1983-01-01

    Possible types of lasers were surveyed for solar power conversion. The types considered were (1) liquid dye lasers, (2) vapor dye lasers, and (3) nondissociative molecular lasers. These are discussed.

  12. Dynamical study of a laser with a saturable absorber

    Energy Technology Data Exchange (ETDEWEB)

    Dignowity, D; RamIrez, R [Centro de Investigaciones en Optica, Loma del Bosque 115, Col. Lomas del Campestre, 37150, Leon, Guanajuato (Mexico)

    2005-01-01

    The study of a laser including a saturable absorber is presented. The non-linear system describing the complex dynamics of the laser is presented. The laser is shown to operate in several regimes depending on the parameters used. It is also shown how the control of the laser is possible depending on the operating regime parameters.

  13. Studies on CO2-laser Hybrid-Welding of Copper

    DEFF Research Database (Denmark)

    Nielsen, Jakob Skov; Olsen, Flemming Ove; Bagger, Claus

    2005-01-01

    CO2-laser welding of copper is known to be difficult due to the high heat conductivity of the material and the high reflectivity of copper at the wavelength of the CO2-laser light. THis paper presents a study of laser welding of copper, applying laser hybrid welding. Welding was performed as a hy...

  14. Molecular dynamics study of lubricant depletion by pulsed laser heating

    Science.gov (United States)

    Seo, Young Woo; Rosenkranz, Andreas; Talke, Frank E.

    2018-05-01

    In this study, molecular dynamics simulations were performed to numerically investigate the effect of pulsed laser heating on lubricant depletion. The maximum temperature, the lubricant depletion width, the number of evaporated lubricant beads and the number of fragmented lubricant chains were studied as a function of laser peak power, pulse duration and repetition rate. A continuous-wave laser and a square pulse laser were simulated and compared to a Gaussian pulse laser. With increasing repetition rate, pulsed laser heating was found to approach continuous-wave laser heating.

  15. Antiferromagnetic–paramagnetic state transition of NiO synthesized by pulsed laser deposition

    CSIR Research Space (South Africa)

    Nkosi, SS

    2013-01-01

    Full Text Available respectively from Raman spectroscopy study. These particle sizes are known be affected by substrate temperature during the deposition. Electron spin resonance (ESR) results demonstrated a strange antiferromagnetic to paramagnetic transition at a room...

  16. Studies on corrosion protection of laser hybrid welded AISI 316 by laser remelting

    DEFF Research Database (Denmark)

    Olsen, Flemming Ove; Ambat, Rajan; Rasmussen, A.J.

    2005-01-01

    laser surface melting on microstructure and corrosion behaviour of AISI 316L welds. Welding and laser treatment parameters were varied. General corrosion behaviour of the weld and laser treated surface was characterised using a gel visualization test. The local electrochemistry of the weld and laser......Unlike in autogenous laser welding, hybrid laser welding of stainless steel could introduce grain boundary carbides due to low cooling rates. Formation of grain boundary carbides leads to reduced corrosion properties. Studies have initially been carried out on hybrid laser welding and subsequent...... treated surface was investigated using a novel micro electrochemical technique with a tip resolution of ~1 mm. Results show that hybrid laser welding of 316L has increased corrosion susceptibility probably as a result of grain boundary carbide formation. However a suitable post laser treatment could...

  17. Dosimetric Properties of Plasma Density Effects on Laser-Accelerated VHEE Beams Using a Sharp Density-Transition Scheme

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Seung Hoon; Cho, Sungho; Kim, Eun Ho; Park, Jeong Hoon; Jung, Won-Gyun; Kim, Geun Beom; Kim, Kum Bae [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Min, Byung Jun [Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Kim, Jaehoon [Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Jeong, Hojin [Gyeongsang National University Hospital, Jinju (Korea, Republic of); Lee, Kitae [Korea Atomic Energy Research Institute, Deajeon (Korea, Republic of); Park, Sung Yong [Karmanos Cancer Institute, Michigan (United States)

    2017-01-15

    In this paper, the effects of the plasma density on laser-accelerated electron beams for radiation therapy with a sharp density transition are investigated. In the sharp density-transition scheme for electron injection, the crucial issue is finding the optimum density conditions under which electrons injected only during the first period of the laser wake wave are accelerated further. In this paper, we report particle-in-cell simulation results for the effects of both the scale length and the density transition ratio on the generation of a quasi-mono-energetic electron bunch. The effects of both the transverse parabolic channel and the plasma length on the electron-beam's quality are investigated. Also, we show the experimental results for the feasibility of a sharp density-transition structure. The dosimetric properties of these very high-energy electron beams are calculated using Monte Carlo simulations.

  18. Thermal transitions in Fe-Ti-Cr-C quaternary system used as precursor during laser in situ carbide coating

    International Nuclear Information System (INIS)

    Singh, Anshul; Porter, Wallace D.; Dahotre, Narendra B.

    2005-01-01

    The temperature range of thermal transitions within the quaternary system (Fe, Ti, Cr, and C) and the thermal stability of the evolved phases were studied with the help of differential scanning calorimetry (DSC). DSC studies indicated that the major exothermic reactions (formation of carbides) take place within 850-1150 deg. C. The evolved phases (TiC, M 7 C 3 , Fe-Cr, and Fe 3 C) were characterized using X-ray diffraction (XRD). This multicomponent powder mixture was used as a precursor for synthesizing a composite coating on the surface of steel via laser surface engineering (LSE). The intended wear applications of the coating made thermal stability investigations vital. Experimental evaluation of thermal stability of the phases formed was done

  19. Kinetic studies following state-selective laser excitation: Progress report, March 15, 1988--March 14, 1989

    International Nuclear Information System (INIS)

    Keto, J.W.

    1988-11-01

    The objective of this contract is the study of state-to-state, electronic energy transfer reactions following two-photon laser excitation. We have chosen to study reactions of Xe 5p 5 np because of their relevance to the XeCl excimer laser. We are studying deactivation reactions in collisions with heavy atoms such as Ar, Kr, and Xe and reactive collisions with chlorides. The reactants are excited by multiphoton laser absorption. Product channels are observed by their fluorescence, or by laser induced fluorescence using a second color laser. Reaction rates are measured by observing the time dependent decay of signals from reactant and product channels. In addition we measure interaction potentials of the reactants by laser spectroscopy where the laser induced fluorescence or ionization is measured as a function of laser wavelength (excitation spectra) or by measuring fluorescence spectra at fixed laser frequencies with monochromators. The spectra are obtained in the form of either lineshapes or individual lines from rovibrational transitions of bound states. 11 refs. 4 figs., 3 tabs

  20. Laser fusion system design study. Final report

    International Nuclear Information System (INIS)

    1975-01-01

    The following studies were completed: (1) The synthesis of a pointing/control system compatible with existing and advanced laser opto-mechanical configurations. (2) Attainment of the required pointing angle, longitudinal focus, and differential pathlength accuracies. (3) Maximum modularization of the sensor and gimbal assemblies to provide the required accuracies at minimum cost. Detailed information is given on each. (MOW)

  1. Measurements of excited-state-to-excited-state transition probabilities and photoionization cross-sections using laser-induced fluorescence and photoionization signals

    International Nuclear Information System (INIS)

    Shah, M.L.; Sahoo, A.C.; Pulhani, A.K.; Gupta, G.P.; Dikshit, B.; Bhatia, M.S.; Suri, B.M.

    2014-01-01

    Laser-induced photoionization and fluorescence signals were simultaneously observed in atomic samarium using Nd:YAG-pumped dye lasers. Two-color, three-photon photoionization and two-color fluorescence signals were recorded simultaneously as a function of the second-step laser power for two photoionization pathways. The density matrix formalism has been employed to analyze these signals. Two-color laser-induced fluorescence signal depends on the laser powers used for the first and second-step transitions as well as the first and second-step transition probability whereas two-color, three-photon photoionization signal depends on the third-step transition cross-section at the second-step laser wavelength along with the laser powers and transition probability for the first and second-step transitions. Two-color laser-induced fluorescence was used to measure the second-step transition probability. The second-step transition probability obtained was used to infer the photoionization cross-section. Thus, the methodology combining two-color, three-photon photoionization and two-color fluorescence signals in a single experiment has been established for the first time to measure the second-step transition probability as well as the photoionization cross-section. - Highlights: • Laser-induced photoionization and fluorescence signals have been simultaneously observed. • The density matrix formalism has been employed to analyze these signals. • Two-color laser-induced fluorescence was used to measure the second-step transition probability. • The second-step transition probability obtained was used to infer the photoionization cross-section. • Transition probability and photoionization cross-section have been measured in a single experiment

  2. Free-Free Transitions of e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident Electron Energies

    Science.gov (United States)

    Bhatia, A. K.; Sinha, C.

    2012-01-01

    The free-free transition is studied for an electron-hydrogen in the ground state at low incident energies in the presence of an external homogenous, monochromatic, and linearly polarized laser-field inside a hot dense plasma.The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit, assuming that the plasma frequency is much higher than the laser frequency. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption /emission and no photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

  3. Image analysis of speckle patterns as a probe of melting transitions in laser-heated diamond anvil cell experiments.

    Science.gov (United States)

    Salem, Ran; Matityahu, Shlomi; Melchior, Aviva; Nikolaevsky, Mark; Noked, Ori; Sterer, Eran

    2015-09-01

    The precision of melting curve measurements using laser-heated diamond anvil cell (LHDAC) is largely limited by the correct and reliable determination of the onset of melting. We present a novel image analysis of speckle interference patterns in the LHDAC as a way to define quantitative measures which enable an objective determination of the melting transition. Combined with our low-temperature customized IR pyrometer, designed for measurements down to 500 K, our setup allows studying the melting curve of materials with low melting temperatures, with relatively high precision. As an application, the melting curve of Te was measured up to 35 GPa. The results are found to be in good agreement with previous data obtained at pressures up to 10 GPa.

  4. Optical transition radiation measurements for the Los Alamos and Boeing Free-Electron Laser experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H.; Feldman, R.B.; Feldman, D.W.; Apgar, S.A.; Calsten, B.E.; Fiorito, R.B.; Rule, D.W.

    1988-01-01

    Optical transition radiation (OTR) measurements of the electron-beam emittance have been performed at a location just before the wiggler in the Los Alamos Free-Electron Laser (FEL) experiment. Beam profiles and beam divergence patterns from a single macropulse were recorded simultaneously using two intensified charge-injection device (CID) television cameras and an optical beamsplitter. Both single-foil OTR and two-foil OTR interference experiments were performed. Preliminary results are compared to a reference variable quadrupole, single screen technique. New aspects of using OTR properties for pointing the e-beam on the FEL oscillator axis, as well as measuring e-beam emittance are addressed. 7 refs., 9 figs.

  5. Adiabatic, diabatic field-free and dressed molecular bases in a semiclassical treatment of laser induced transitions near pseudocrossings

    Energy Technology Data Exchange (ETDEWEB)

    Errea, L.F.; Mendez, L.; Riera, A.

    1986-07-15

    We study the characteristics of charge exchange processes in ion--atom collisions, induced by a strong laser field whose wavelength is resonant to the splitting at a pseudocrossing of two molecular adiabatic energies, where the transition dipole has a sharp maximum. To calculate the charge exchange cross section we use a semiclassical approach and a molecular expansion for the electronic wave function. Using the formalism of Macias and Riera, and of Ho, Chu, and Laughlin, the properties and practical advantages of field-free and dressed molecular wave functions in that expansion are studied in detail. In practice we have found the former basis to be more advantageous from the computational point of view. A limitation of the Floquet approach of Ho et al. is obtained. As an illustration, we treat O/sup 8 +/+H(1s) charge exchange collisions in presence of a laser field whose frequency is quasiresonant with the energy splitting at the pseudocrossing between the 7isigma and the 6hsigma energy curves. The importance of the (usually neglected) diagonal ac Stark terms is stressed.

  6. Adiabatic, diabatic field-free and dressed molecular bases in a semiclassical treatment of laser induced transitions near pseudocrossings

    International Nuclear Information System (INIS)

    Errea, L.F.; Mendez, L.; Riera, A.

    1986-01-01

    We study the characteristics of charge exchange processes in ion--atom collisions, induced by a strong laser field whose wavelength is resonant to the splitting at a pseudocrossing of two molecular adiabatic energies, where the transition dipole has a sharp maximum. To calculate the charge exchange cross section we use a semiclassical approach and a molecular expansion for the electronic wave function. Using the formalism of Macias and Riera, and of Ho, Chu, and Laughlin, the properties and practical advantages of field-free and dressed molecular wave functions in that expansion are studied in detail. In practice we have found the former basis to be more advantageous from the computational point of view. A limitation of the Floquet approach of Ho et al. is obtained. As an illustration, we treat O 8+ +H(1s) charge exchange collisions in presence of a laser field whose frequency is quasiresonant with the energy splitting at the pseudocrossing between the 7isigma and the 6hsigma energy curves. The importance of the (usually neglected) diagonal ac Stark terms is stressed

  7. Numerical simulation of compressible multiphase flows with or without phase transition. Application to laser plasma interaction

    International Nuclear Information System (INIS)

    Perrier, V.

    2007-07-01

    This work deals with the modelling and simulation of compressible flows. A seven equations model is obtained by homogenizing the Euler system. Fluctuation terms are modeled as relaxation terms. When the relaxation terms tend to infinity, which means that the phases are well mixed, a five equations model is obtained via an asymptotic expansion. This five equations model is strictly hyperbolic, but nonconservative. The discretization of this model is obtained by an asymptotic expansion of a scheme for the seven equations model. The numerical method is implemented, validated on analytic cases, and compared with experiments in the case of multiphase shocks. We are then interested in the modelling of phase transition with two equations of state. Optimization of the mixture entropy leads to the fact that three zones can be separated: one in which the pure liquid is the most stable, one in which the pure gas is the most stable, and one in which a mixture with equality of temperature, pressure and chemical potentials is the most stable. Conditions are given on the coupling of the two equations of state for ensuring that the mixture equation of state is convex, and that the system is strictly hyperbolic. In order to take into account phase transition, a vaporization wave is introduced in the solution of the Riemann problem, that is modeled as a deflagration wave. It is then proved that the usual closure, the Chapman-Jouguet closure, is wrong in general, and a correct closure in the case when both fluids have a perfect gas equation of state. Last, the solution of the Riemann problem is implemented in a multiphase code, and validated on analytic cases. In the same code, models of laser release and thermal conduction are implemented to simulate laser ablation. The results are comparable to the ones obtained with scale laws. The last chapter, fully independent, is concerned with correctors in stochastic homogenization in the case of heavy tails process. (author)

  8. Water evaporation: a transition path sampling study.

    Science.gov (United States)

    Varilly, Patrick; Chandler, David

    2013-02-07

    We use transition path sampling to study evaporation in the SPC/E model of liquid water. On the basis of thousands of evaporation trajectories, we characterize the members of the transition state ensemble (TSE), which exhibit a liquid-vapor interface with predominantly negative mean curvature at the site of evaporation. We also find that after evaporation is complete, the distributions of translational and angular momenta of the evaporated water are Maxwellian with a temperature equal to that of the liquid. To characterize the evaporation trajectories in their entirety, we find that it suffices to project them onto just two coordinates: the distance of the evaporating molecule to the instantaneous liquid-vapor interface and the velocity of the water along the average interface normal. In this projected space, we find that the TSE is well-captured by a simple model of ballistic escape from a deep potential well, with no additional barrier to evaporation beyond the cohesive strength of the liquid. Equivalently, they are consistent with a near-unity probability for a water molecule impinging upon a liquid droplet to condense. These results agree with previous simulations and with some, but not all, recent experiments.

  9. Optical gain for the interband optical transition in InAsP/InP quantum well wire in the influence of laser field intensity

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, S. [Dept.of Physics, GTN Arts College, Dindigul-624 005. India (India); Peter, A. John, E-mail: a.john.peter@gmail.com [P.G & Research Dept.of Physics, Government Arts College, Melur-625 106. Madurai. India (India)

    2016-05-23

    Intense high frequency laser field induced electronic and optical properties of heavy hole exciton in the InAs{sub 0.8}P{sub 0.2}/InP quantum wire is studied taking into account the geometrical confinement effect. Laser field related exciton binding energies and the optical band gap in the InAs{sub 0.8}P{sub 0.2}/InP quantum well wire are investigated. The optical gain, for the interband optical transition, as a function of photon energy, in the InAs{sub 0.8}P{sub 0.2}/InP quantum wire, is obtained in the presence of intense laser field. The compact density matrix method is employed to obtain the optical gain. The obtained optical gain in group III-V narrow quantum wire can be applied for achieving the preferred telecommunication wavelength.

  10. Laser reflection method for determination of shear stress in low density transitional flows

    Science.gov (United States)

    Sathian, Sarith P.; Kurian, Job

    2006-03-01

    The details of laser reflection method (LRM) for the determination of shear stress in low density transitional flows are presented. The method is employed to determine the shear stress due to impingement of a low density supersonic free jet issuing out from a convergent divergent nozzle on a flat plate. The plate is smeared with a thin oil film and kept parallel to the nozzle axis. For a thin oil film moving under the action of aerodynamic boundary layer, the shear stress at the air-oil interface is equal to the shear stress between the surface and air. A direct and dynamic measurement of the oil film slope generated by the shear force is done using a position sensing detector (PSD). The thinning rate of the oil film is directly measured which is the major advantage of the LRM. From the oil film slope history, calculation of the shear stress is done using a three-point formula. The range of Knudsen numbers investigated is from 0.028 to 0.516. Pressure ratio across the nozzle varied from 3,500 to 8,500 giving highly under expanded free jets. The measured values of shear, in the overlapping region of experimental parameters, show fair agreement with those obtained by force balance method and laser interferometric method.

  11. Study of Laser Reflectivity on Skin

    International Nuclear Information System (INIS)

    Oidor-Garcia, J. J. J.; Trevino-Palacios, C. G.

    2008-01-01

    The response to the light on the skin can be manifested as temperature increase or creation of biochemical byproducts, in which further studies are required to asset the light effect. This response changes the average response over time and can produce discrepancies between similar studies. In this work we present a Low Level Laser Therapy (LLLT) study with feedback. We study the time response reflectivity of a 980 nm laser diode of 25 mW modulated at frequencies close to 40 kHz and detect the reflected light on a silicon photodiode, finding no direct correlation between different test points or individuals, while finding reproducible responses within the same individual and test point

  12. Strain-free Ge/GeSiSn Quantum Cascade Lasers Based on L-Valley Intersubband Transitions

    National Research Council Canada - National Science Library

    Soret, R. A; Sun, G; Cheng, H; Menendez, J; Khurgin, J

    2007-01-01

    The authors propose a Ge/Ge0.76Si0.19Sn0.05 quantum cascade laser using intersubband transitions at L valleys of the conduction band which has a clean offset of 150 meV situated below other energy valleys Gamma and X...

  13. Study of the phase transition dynamics of the L to H transition

    International Nuclear Information System (INIS)

    Moyer, R.A.; Rhodes, T.L.; Rettig, C.L.

    1997-12-01

    A highly radiating zone (MARFE) just above the divertor X-point has been used to access the marginal transition regime P sep ∼ P thres to study the existence of a critical point for the L to H transition. Phase transition models predict that at the critical point, the transition duration increases and the plasma parameters vary continuously between L-mode and H-mode. In these experiments, the L to H transition duration increased 50--100 times over fast transitions. However, the evolution of E r shear, edge density gradient, H-mode pedestal, and fluctuations is essentially unchanged from that in fast transitions. The only difference is in the speed with which and the degree to which the fluctuation amplitudes are transiently reduced. This difference is understandable in terms of the time scales for fluctuation amplitude reduction (≤ 100 micros) and edge pressure gradient increase (several ms), provided the edge fluctuations are pressure-gradient driven

  14. Transit value capture coordination : case studies, best practices, and recommendations.

    Science.gov (United States)

    2015-02-17

    This study is based on the hypothesis that coordination between transit capital planners, municipal taxation authorities, and private developers and stakeholders can be a benefit to transit capital projects that choose to use value capture as a fundi...

  15. Establishing Antibacterial Multilayer Films on the Surface of Direct Metal Laser Sintered Titanium Primed with Phase-Transited Lysozyme

    Science.gov (United States)

    Guan, Binbin; Wang, Haorong; Xu, Ruiqing; Zheng, Guoying; Yang, Jie; Liu, Zihao; Cao, Man; Wu, Mingyao; Song, Jinhua; Li, Neng; Li, Ting; Cai, Qing; Yang, Xiaoping; Li, Yanqiu; Zhang, Xu

    2016-11-01

    Direct metal laser sintering is a technology that allows the fabrication of titanium (Ti) implants with a functional gradation of porosity and surface roughness according to three-dimensional (3D) computer data. The surface roughness of direct metal laser sintered titanium (DMLS-Ti) implants may provide abundant binding sites for bacteria. Bacterial colonization and subsequent biofilm formation can cause unsatisfactory cell adhesion and implant-related infections. To prevent such infections, a novel phase-transited lysozyme (PTL) was utilized as an initial functional layer to simply and effectively prime DMLS-Ti surfaces for subsequent coating with antibacterial multilayers. The purpose of the present study was to establish a surface with dual biological functionality. The minocycline-loaded polyelectrolyte multilayers of hyaluronic acid (HA) and chitosan (CS) formed via a layer-by-layer (LbL) self-assembly technique on PTL-functionalized DMLS-Ti were designed to inhibit pathogenic microbial infections while allowing the DMLS-Ti itself and the modified coatings to retain acceptable biocompatibility. The experimental results indicate that the DMLS-Ti and the hydrogel treated surfaces can inhibit early bacterial adhesion while completely preserving osteoblast functions. This design is expected to gain considerable interest in the medical field and to have good potential for applications in multifunctional DMLS-Ti implants.

  16. Establishing Antibacterial Multilayer Films on the Surface of Direct Metal Laser Sintered Titanium Primed with Phase-Transited Lysozyme.

    Science.gov (United States)

    Guan, Binbin; Wang, Haorong; Xu, Ruiqing; Zheng, Guoying; Yang, Jie; Liu, Zihao; Cao, Man; Wu, Mingyao; Song, Jinhua; Li, Neng; Li, Ting; Cai, Qing; Yang, Xiaoping; Li, Yanqiu; Zhang, Xu

    2016-11-08

    Direct metal laser sintering is a technology that allows the fabrication of titanium (Ti) implants with a functional gradation of porosity and surface roughness according to three-dimensional (3D) computer data. The surface roughness of direct metal laser sintered titanium (DMLS-Ti) implants may provide abundant binding sites for bacteria. Bacterial colonization and subsequent biofilm formation can cause unsatisfactory cell adhesion and implant-related infections. To prevent such infections, a novel phase-transited lysozyme (PTL) was utilized as an initial functional layer to simply and effectively prime DMLS-Ti surfaces for subsequent coating with antibacterial multilayers. The purpose of the present study was to establish a surface with dual biological functionality. The minocycline-loaded polyelectrolyte multilayers of hyaluronic acid (HA) and chitosan (CS) formed via a layer-by-layer (LbL) self-assembly technique on PTL-functionalized DMLS-Ti were designed to inhibit pathogenic microbial infections while allowing the DMLS-Ti itself and the modified coatings to retain acceptable biocompatibility. The experimental results indicate that the DMLS-Ti and the hydrogel treated surfaces can inhibit early bacterial adhesion while completely preserving osteoblast functions. This design is expected to gain considerable interest in the medical field and to have good potential for applications in multifunctional DMLS-Ti implants.

  17. Space and time resolved spectroscopy of laser-produced plasmas: A study of density-sensitive x-ray transitions in helium-like and neon-like ions

    International Nuclear Information System (INIS)

    Young, Bruce Kai Fong.

    1988-09-01

    The determination of level populations and detailed population mechanisms in dense plasmas has become an increasingly important problem in atomic physics. In this work, the density variation of line intensities and level populations in aluminum K-shell and molybdenum and silver L-shell emission spectra have been measured from high-powered, laser-produced plasmas. For each case, the density dependence of the observed line emission is due to the effect of high frequency electron-ion collisions on metastable levels. The density dependent line intensities vary greatly in laser-produced plasmas and can be used to extract detailed information concerning the population kinetics and level populations of the ions. The laser-plasmas had to be fully characterized in order to clearly compare the observed density dependence with atomic theory predictions. This has been achieved through the combined use of new diagnostic instruments and microdot targets which provided simultaneously space, time, and spectrally resolved data. The plasma temperatures were determined from the slope of the hydrogen-like recombination continuum. The time resolved electron density profiles were measured using multiple frame holographic interferometry. Thus, the density dependence of K-shell spectral lines could be clearly examined, independent of assumptions concerning the dynamics of the plasma. In aluminum, the electron density dependence of various helium-like line intensity ratios were measured. Standard collisional radiative equilibrium models fail to account for the observed density dependence measured for the ''He/sub α//IC'' ratio. Instead, a quasi-steady state atomic model based on a purely recombining plasma is shown to accurately predict the measured density dependence. This same recombining plasma calculation successfully models the density dependence of the high-n ''He/sub γ//He/sub β/'' and ''He/sub δ//He/sub β/'' helium-like resonance line intensity ratios

  18. Space and time resolved spectroscopy of laser-produced plasmas: A study of density-sensitive x-ray transitions in helium-like and neon-like ions

    Energy Technology Data Exchange (ETDEWEB)

    Young, Bruce Kai Fong

    1988-09-01

    The determination of level populations and detailed population mechanisms in dense plasmas has become an increasingly important problem in atomic physics. In this work, the density variation of line intensities and level populations in aluminum K-shell and molybdenum and silver L-shell emission spectra have been measured from high-powered, laser-produced plasmas. For each case, the density dependence of the observed line emission is due to the effect of high frequency electron-ion collisions on metastable levels. The density dependent line intensities vary greatly in laser-produced plasmas and can be used to extract detailed information concerning the population kinetics and level populations of the ions. The laser-plasmas had to be fully characterized in order to clearly compare the observed density dependence with atomic theory predictions. This has been achieved through the combined use of new diagnostic instruments and microdot targets which provided simultaneously space, time, and spectrally resolved data. The plasma temperatures were determined from the slope of the hydrogen-like recombination continuum. The time resolved electron density profiles were measured using multiple frame holographic interferometry. Thus, the density dependence of K-shell spectral lines could be clearly examined, independent of assumptions concerning the dynamics of the plasma. In aluminum, the electron density dependence of various helium-like line intensity ratios were measured. Standard collisional radiative equilibrium models fail to account for the observed density dependence measured for the ''He/sub ..cap alpha..//IC'' ratio. Instead, a quasi-steady state atomic model based on a purely recombining plasma is shown to accurately predict the measured density dependence. This same recombining plasma calculation successfully models the density dependence of the high-n ''He/sub ..gamma..//He/sub ..beta../'' and ''He/sub delta

  19. Laser fusion study. Final report

    International Nuclear Information System (INIS)

    1975-06-01

    The following appendices are included: (1) sensor performance calculation techniques, (2) focus sensing, (3) purchased item data, (4) pointing and focusing configuration tradeoff studies, (5) false start centering sensor, (6) RCA application notes on quad delection, (7) elliptical flex pivot analysis, (8) servo mirrors cross coupling, (9) optical misalignment analysis, (10) stress induced birefrigent quarter-wave retarder, (11) data bulletin on incramute damping alloy, (12) the utilization of stepping motors, and (13) computer program listing for stepper motor load simulation

  20. Amorphous to crystalline phase transition in carbon induced by intense femtosecond x-ray free-electron laser pulses

    Czech Academy of Sciences Publication Activity Database

    Gaudin, J.; Peyrusse, O.; Chalupský, Jaromír; Toufarová, Martina; Vyšín, Luděk; Hájková, Věra; Sobierajski, R.; Burian, Tomáš; Dastjani-Farahani, S.; Graf, A.; Amati, M.; Gregoratti, L.; Hau-Riege, S.P.; Hoffmann, G.; Juha, Libor; Krzywinski, J.; London, R.A.; Moeller, S.; Sinn, H.; Schorb, S.; Störmer, M.; Tschentscher, T.; Vorlíček, Vladimír; Vu, H.; Bozek, J.; Bostedt, C.

    2012-01-01

    Roč. 86, č. 2 (2012), "024103-1"-"024103-7" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP108/11/1312; GA ČR GAP205/11/0571; GA ČR GAP208/10/2302; GA AV ČR IAAX00100903; GA MŠk EE.2.3.20.0087 Grant - others:OP VK 2 LaserGen(XE) CZ.1.07/2.3.00/20.0087 Institutional research plan: CEZ:AV0Z10100523 Keywords : amorphous carbon * phase transition * graphitization * x-ray laser * free-electron laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.767, year: 2012

  1. Laser Raman Spectroscopy in studies of corrosion and electrocatalysis

    International Nuclear Information System (INIS)

    Melendres, C.A.

    1988-01-01

    Laser Raman Spectroscopy (LRS) has become an important tool for the in-situ structural study of electrochemical systems and processes in recent years. Following a brief introduction of the experimental techniques involved in applying LRS to electrochemical systems, we survey the literature for examples of studies in the inhibition of electrode reactions by surface films (e.g., corrosion and passivation phenomena) as well as the acceleration of reactions by electro-sorbates (electrocatalysis). We deal mostly with both normal and resonance Raman effects on fairly thick surface films in contrast to surface-enhanced Raman investigations of monolayer adsorbates, which is covered in another lecture. Laser Raman spectroelectrochemical studies of corrosion and film formation on such metals as Pb, Ag, Fe, Ni, Co, Cr, Au, stainless steel, etc. in various solution conditions are discussed. Further extension of the technique to studies in high-temperature and high-pressure aqueous environments is demonstrated. Results of studies of the structure of corrosion inhibitors are also presented. As applications of the LRS technique in the area of electrocatalysis, we cite studies of the structure of transition metal macrocyclic compounds, i.e., phthalocyanines and porphyrins, used for catalysis of the oxygen reduction reaction. 104 refs., 20 figs

  2. Experimental study of linear magnetic dichroism in photoionization satellite transitions of atomic rubidium

    International Nuclear Information System (INIS)

    Jaenkaelae, K.; Alagia, M.; Feyer, V.; Richter, R.; Prince, K. C.

    2011-01-01

    Laser orientation in the initial state has been used to study the properties of satellite transitions in inner-shell photoionization of rubidium atoms. The linear magnetic dichroism in the angular distribution (LMDAD) has been utilized to probe the continuum waves of orbital angular momentum conserving monopole, and angular momentum changing conjugate satellites, accompanying the 4p ionization of atomic Rb. We show experimentally that LMDAD of both types of satellite transitions is nonzero and that LMDAD of monopole satellites, measured as a function of photon energy, mimics the LMDAD of direct photoionization, whereas the LMDAD of conjugate transitions deviates drastically from that trend. The results indicate that conjugate transitions cannot be described theoretically without explicit inclusion of electron-electron interaction. The present data can thus be used as a very precise test of current models for photoionization.

  3. Radiotherapy enhances laser palliation of malignant dysphagia: a randomised study

    Energy Technology Data Exchange (ETDEWEB)

    Sargeant, I.R.; Thorpe, S.; Glover, J.R.; Bown, S.G. [National Medical Laser Centre, London (United Kingdom); Tobias, J.S.; Blackman, G. [University Coll., London (United Kingdom). Meyerstein Inst. of Oncology

    1997-03-01

    A major drawback of laser endoscopy in the palliation of malignant dysphagia is the need for repeated treatments. This study was designed to test whether external beam radiotherapy would reduce the necessity for repeated laser therapy. (author).

  4. Radiotherapy enhances laser palliation of malignant dysphagia: a randomised study

    International Nuclear Information System (INIS)

    Sargeant, I.R.; Thorpe, S.; Glover, J.R.; Bown, S.G.; Tobias, J.S.; Blackman, G.

    1997-01-01

    A major drawback of laser endoscopy in the palliation of malignant dysphagia is the need for repeated treatments. This study was designed to test whether external beam radiotherapy would reduce the necessity for repeated laser therapy. (author)

  5. Photon-phonon laser on crystalline silicon: a feasibility study

    International Nuclear Information System (INIS)

    Zadernovsky, A A

    2015-01-01

    We discuss a feasibility of photon-phonon laser action in bulk silicon with electron population inversion. It is well known, that only direct gap semiconductors are used as an active medium in optical lasers. In indirect gap semiconductors, such as crystalline silicon, the near-to-gap radiative electron transitions must be assisted by emission or absorption of phonons to conserve the momentum. The rate of such two-quantum transitions is much less than in direct gap semiconductors, where the similar radiative transitions are single-quantum. As a result, the quantum efficiency of luminescence in silicon is too small to get it as a laser material. Numerous proposals to overcome this problem are aimed at increasing the rate of radiative recombination. We suggest enhancing the quantum efficiency of luminescence in silicon by stimulating the photon part of the two-quantum transitions by light from an appropriate external laser source. This allows us to obtain initially an external-source-assisted lasing in silicon and then a true photon-phonon lasing without any external source of radiation. Performed analysis revealed a number of requirements to the silicon laser medium (temperature, purity and perfection of crystals) and to the intensity of stimulating radiation. We discuss different mechanisms that may hinder the implementation of photon-phonon lasing in silicon

  6. Gifted Students in Transition: A Grounded Theory Study

    Science.gov (United States)

    Meadows, Jodi J.

    2017-01-01

    Gifted students in transition to college may be at risk for underachievement, difficult transition, or even attrition. Giftedness by itself is not always sufficient for academic success in college. The purpose of this grounded theory study was to construct a theory regarding the process of transition to college for high-achieving gifted high…

  7. Exploratory laser-driven shock wave studies

    International Nuclear Information System (INIS)

    Solem, J.C.; Veeser, L.R.

    1977-11-01

    We show the results of a feasibility study for investigating shock structure and for measuring equation-of-state parameters using high-energy, short-pulse lasers. We discuss the temporal and spatial structure of the luminosity from laser-driven shock unloading in aluminum foils. We demonstrate that shock velocity can be measured by observing the time interval between shock emergence across two thicknesses and show data for shocks of 1.3 and 2.1 Mbar. The fact that we observe shock fronts cleanly breaking through steps as small as 3 μm indicates that the shock front thickness is very small in the few megabar region; this is the first experimental verification that these fronts are not more than a few micrometers thick. We present approximate measurements of free-surface velocity. Finally, we speculate on the use of these techniques to obtain detailed equation-of-state data

  8. Laser fusion hybrid reactor systems study

    International Nuclear Information System (INIS)

    1976-07-01

    The work was performed in three phases. The first phase included a review of the many possible laser-reactor-blanket combinations and resulted in the selection of a ''demonstration size'' 500 MWe plant for further study. A number of fast fission blankets using uranium metal, uranium-molybdenum alloy, and uranium carbide as fuel were investigated. The second phase included design of the reactor vessel and internals, heat transfer system, tritium processing system, and the balance of plant, excluding the laser building and equipment. A fuel management scheme was developed, safety considerations were reviewed, and capital and operating costs were estimated. Costs developed during the second phase were unexpectedly high, and a thorough review indicated considerable unit cost savings could be obtained by scaling the plant to a larger size. Accordingly, a third phase was added to the original scope, encompassing the redesign and scaling of the plant from 500 MWe to 1200 MWe

  9. Free-Free Transitions of the e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident-Electron Energies

    Science.gov (United States)

    Bhatia, A. K.; Sinha, C.

    2012-01-01

    The free-free transition is studied for an electron-hydrogen atom in ground state when a low-energy electron (external) is injected into hydrogenic plasma in the presence of an external homogenous, monochromatic, and linearly polarized laser field. The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption or emission and no-photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

  10. Short-wavelength multiline erbium-doped fiber ring laser by a broadband long-period fiber grating inscribed in a taper transition

    International Nuclear Information System (INIS)

    Anzueto-Sánchez, G; Martínez-Rios, A

    2014-01-01

    A stable multiwavelength all-fiber erbium-doped fiber ring laser (EDFRL) based on a broadband long-period fiber grating (LPFG) inscribed in a fiber taper transition is presented. The LPFG’s characteristics were engineered to provide a higher loss at the natural lasing wavelength of the laser cavity. The LPFG inscribed on a taper transition provided a depth greater than 25 dB, and posterior chemical etching provided a broad notch band to inhibit laser generation on the long-wavelength side of the EDF gain. Up to four simultaneous laser wavelengths are generated in the range of 1530–1535 nm. (paper)

  11. Observation of double resonant laser induced transitions in the $v = n - l - 1 = 2$ metastable cascade of antiprotonic helium-4 atoms

    CERN Document Server

    Hayano, R S; Tamura, H; Torii, H A; Hori, Masaki; Maas, F E; Morita, N; Kumakura, M; Sugai, I; Hartmann, F J; Daniel, H; Von Egidy, T; Ketzer, B; Pohl, R; Horváth, D; Eades, John; Widmann, E; Yamazaki, T

    1997-01-01

    A new laser-induced resonant transition in the $v=n-l-1=2$ metastable cascade of antiprotonic $^4$He atoms has been found by using a double resonance technique. This was done by setting the first laser to the already known 470.724 nm resonance ($(n,l)=(37,34)\\rightarrow (36,33)$), while the $(38,35)\\rightarrow (37,34)$ transition was searched for with the second laser. The resonant transition was found at wavelength of 529.622$\\pm$0.003 nm, showing excellent agreement with a recent prediction of Korobov.

  12. Dissociative photoionization of molecular hydrogen. A joint experimental and theoretical study of the electron-electron correlations induced by XUV photoionization and nuclear dynamics on IR-laser dressed transition states

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Andreas

    2015-01-13

    In this thesis, the dissociative single-ionization of molecular hydrogen is investigated in a kinematically complete experiment by employing extreme ultraviolet attosecond pulse trains and infrared femtosecond laser pulses. Induced by the absorption of a single XUV photon, a pronounced energy-dependent asymmetry of the relative emission direction of the photoelectron and the ion is observed. The asymmetry pattern is explained in terms of an interference of two ionization pathways involving a doubly-excited state. This interpretation is validated by a semi-classical model which only takes the nuclear motion into account. Using this model and the observed asymmetry, it is furthermore possible to disentangle the two dissociation pathways which allows for the determination of the autoionization lifetime of the contributing doubly-excited state as a function of the internuclear distance. Moreover, using a pump-probe experiment the dissociation dynamics of molecular hydrogen is investigated. A time-delay dependent momentum distribution of the fragments is observed. With a combined quantum mechanical and semi-classical approach the mechanism giving rise to the observed time-dependence is identified in terms of an intuitive elevator mechanism.

  13. Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.

    Science.gov (United States)

    Linford, G J

    1973-06-01

    A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air.

  14. Numerical Study of Transition of an Annular Lift Fan Aircraft

    OpenAIRE

    Yun Jiang; Bo Zhang

    2016-01-01

    The present study aimed at studying the transition of annular lift fan aircraft through computational fluid dynamics (CFD) simulations. The oscillations of lift and drag, the optimization for the figure of merit, and the characteristics of drag, yawing, rolling and pitching moments in transition are studied. The results show that a two-stage upper and lower fan lift system can generate oscillations of lift and drag in transition, while a single-stage inner and outer fan lift system can elimin...

  15. Phase transition in lead titanate thin films: a Brillouin study

    International Nuclear Information System (INIS)

    Kuzel, P; Dugautier, C; Moch, P; Marrec, F Le; Karkut, M G

    2002-01-01

    The elastic properties of both polycrystalline and epitaxial PbTiO 3 (PTO) thin films are studied using Brillouin scattering spectroscopy. The epitaxial PTO films were prepared by pulsed laser ablation on (1) a [0 0 1] single crystal of SrTiO 3 (STO) doped with Nb and (2) a [0 0 1] STO buffered with a layer of YBa 2 Cu 3 O 7 . The polycrystalline PTO films were prepared by sol-gel on a Si substrate buffered with TiO 2 and Pt layers. The data analysis takes into account the ripple and the elasto-optic contributions. The latter significantly affects the measured spectra since it gives rise to a Love mode in the p-s scattering geometry. At room temperature, the spectra of the epitaxially grown samples are interpreted using previously published elastic constants of PTO single crystals. Sol-gel samples exhibit appreciable softening of the effective elastic properties compared to PTO single crystals: this result is explained by taking into account the random orientation of the microscopic PTO grains. For both the polycrystalline and the epitaxial films we have determined that the piezoelectric terms do not contribute to the spectra. The temperature dependence of the spectra shows strong anomalies of the elastic properties near the ferroelectric phase transition. Compared to the bulk, T C is higher in the sol-gel films, while in the epitaxial films the sign of the T C shift depends on the underlying material

  16. Study of Laser Created Metal Vapor Plasmas.

    Science.gov (United States)

    1979-11-16

    Leventhal(1 indicate a value closer to 10-1 cm. might be expected. In the case of’ laser induced penniinf, ionization., wec -,;4-,rit LIP 32 LIP L J where...modified Kramer’s formulae.(25) In figure 11 we demonstrate the impact of associative ionization and laser induced penning ionization upon the temporal...34Laser Induced Fluorescence and Environmental Sensing", Invited paper for Optical Society of America, Topical Mcetixg on "Applications of Laser

  17. Femtosecond laser studies of ultrafast intramolecular processes

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, C. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    The goal of this research is to better understand the detailed mechanisms of chemical reactions by observing, directly in time, the dynamics of fundamental chemical processes. In this work femtosecond laser pulses are used to initiate chemical processes and follow the progress of these processes in time. The authors are currently studying ultrafast internal conversion and subsequent intramolecular relaxation in unsaturated hydrocarbons. In addition, the authors are developing nonlinear optical techniques to prepare and monitor the time evolution of specific vibrational motions in ground electronic state molecules.

  18. The Transit/Admission Lounge study.

    LENUS (Irish Health Repository)

    Gilligan, P

    2009-01-01

    In response to persistent overcrowding of Emergency Departments in Ireland, the Department of Health and Health Service Executive provided funding for "Transit Lounge" areas to be built. These lounges were to provide a location for patients to wait in beds pending the availability of a ward bed. This research was performed to assess the impact of such a lounge on the overcrowding of the Emergency Department and on patient outcomes. The time period from the opening of the Transit Lounge was compared with the same period a year earlier. The Transit Lounge delivers a comfortable place for patients to wait. It does not reduce Emergency Department overcrowding and has been associated with an increased time waiting for a ward bed. The solution to overcrowding is the creation of real capacity in the system so that ward beds are available in acute hospitals for the "unscheduled unwell".

  19. Observations of high-n transitions in the spectra of near-neon-like copper ions from laser-produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, K.B. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Faenov, A.Ya.; Pikuz, T.A.; Skobelev, I.Yu. [Multicharged Ions Spectra Data Center of VNIIFTRI, Moscow (Russian Federation); Flora, F.; Bollanti, S.; Lazzaro, P.Di.; Murra, D. [ENEA, Dipartimento Innovazione, Settore Fisica Applicata, Frascati, Rome (Italy); Grilli, A. [INFN Frascati, Rome (Italy); Reale, A.; Reale, L.; Tomassetti, G.; Ritucci, A. [Dipartimento di Fisica e INFM, INFN g.c. LNGS, Universita dell' Aquila, L' Aquila (Italy); Bellucci, I.; Martellucci, S.; Petrocelli, G. [INFM, Dipartimento di Scienze e Tecnologie Fisiche ed Energetiche, Universita di Roma Tor Vergata, Rome (Italy)

    2002-08-14

    Spectra in the 7.50-8.70 A range from highly charged copper ions are analysed, and line identifications are made for the Na-, Ne-, F- and O-like charge states. The spectra are recorded with a spherically bent crystal spectrometer using either a mica or quartz crystal for moderate ({lambda}/{delta}{lambda}=3000) and high ({lambda}/{delta}{lambda}=8000) energy resolution, respectively. The plasmas from which the spectra are emitted are formed with either a Nd:glass (15 ns pulse) or a XeCl (12 ns pulse) laser. Systematic variations in the observed spectra with pulse energy are studied. Using different laser energies, and defocusing of the laser to reduce the intensity, we create plasmas with different ionization state distributions, which allows us to deconvolve blended lines from different copper ions. Line identifications are made based on relativistic atomic structure calculations that account for configuration interaction in level energies and transition rates. We use full kinetics simulations of ion emissivities, not just calculations of theoretical transition energies, to identify the strong and weak lines in crowded spectral regions. We identify 2p-nl transitions for Ne-like Cu{sup 19+} for 4{<=}n{<=}8 and 2s-np transitions for 4{<=}n{<=}6. We offer the first identification of high-n (n{<=}8) Na-like satellites to Ne-like Rydberg resonance lines. The first and second ionization energies for Cu{sup 19+} are found, at 1689.02 and 1709.16 eV, respectively, based on our observations. (author)

  20. Investigation of the hyperfine structure of Praseodymium-transitions using laser spectroscopy

    International Nuclear Information System (INIS)

    Shamim Khan

    2011-01-01

    A comprehensive knowledge of the electron levels in an atom is one of the prerequisite for understanding the electron-electron and electron-nucleus interactions inside an atom and for the classification of the atomic spectrum of an element. The spin-orbit interaction is the largest relativistic effect and is responsible for the fine structure splitting in an atom. The hyperfine structure splitting of the fine structure atomic energy levels arise as a result of the interaction between spinning and orbiting electrons and electromagnetic multipole nuclear moments. The electronic ground state configuration of praseodymium 59 Pr 141 is [Xe] 4f 3 6s 2 , with ground state level 4 I 9/2 . Because of its 5 outer electrons Praseodymium has a high density of energy levels which give rise to an extremely line rich emission spectrum. Due to this fact praseodymium serves as an efficient testing ground for hyperfine structure studies. The thesis is mainly devoted to the finding of previously unknown energy levels by the investigation of spectral lines and their hyperfine structures. In a hollow cathode discharge lamp praseodymium atoms and ions in ground and excited states are excited to high lying states by laser light. The excitation source is a tunable ring-dye laser system, operated with Stilbene 3, Rhodamine 6G, Kiton Red, DCM and LD 700. A high resolution Fourier Transform spectrum is used for extracting excitation wavelengths. Then the laser wavelength is tuned to a strong hyperfine component of the spectral line to be investigated, and a search for fluorescence from excited levels is performed. From the observed hyperfine structure pattern, J-values and hyperfine interaction constants A of the combining levels are determined. This information, together with excitation and fluorescence wavelengths, allows us to find the energies of the involved levels. During the course of this dissertation 313 new energy levels of Pr I and 4 new energy levels of Pr II were discovered

  1. Theoretcial studies of solar-pumped lasers

    Science.gov (United States)

    Harries, W. L.; Fong, Z. S.

    1984-01-01

    A method of pumping a COhZ laser by a hot cavity was demonstrated. The cavity, heated by solar radiation, should increase the efficiency of solar pumped lasers used for energy conversion. Kinetic modeling is used to examine the behavior of such a COhZ laser. The kinetic equations are solved numerically vs. time and, in addition, steady state solutions are obtained analytically. The effect of gas heating filling the lower laser level is included. The output power and laser efficiency are obtained as functions of black body temperature and gas ratios (COhZ-He-Ar) and pressures. The values are compared with experimental results.

  2. Laser ablation studies in southern Africa

    Science.gov (United States)

    McKenzie, Edric; Forbes, A.; Turner, G. R.; Michaelis, Max M.

    2000-08-01

    With the launch of the South African National Laser Centre, new programs will need to be defined. Medical, environmental and industrial laser applications must obviously take top priority -- as opposed to the uranium isotope separation and military applications of the past. We argue however, that a small effort in laser ablation for space propulsion is justifiable, since a few very large CO2 lasers are available and since two tentative propulsion experiments have already been conducted in South Africa. We attempt to give LISP (Laser Impulse Space Propulsion) an equatorial and a Southern dimension.

  3. Study of compact X-ray laser pumped by pulse-train laser. Double-target experiment

    International Nuclear Information System (INIS)

    Yamaguchi, Naohiro; Fujikawa, Chiemi; Hara, Tamio

    2000-01-01

    We have been developing a tabletop x-ray laser based on the recombination plasma scheme. An advanced experiment has been started to improve x-ray laser output substantially. Two 11-mm-long laser produced plasmas were produced so that their axis aligned into a line, the double-target configuration. X-ray intensity of the 15.47 nm transition line of the Li-like Al ion has been enhanced in the double-target configuration. (author)

  4. Reduction in L10 phase transition temperature of PLD grown FePt thin by pre-annealing pulse laser exposure

    International Nuclear Information System (INIS)

    Wang, Y.; Rawat, R.S.; Bisht, A.

    2013-01-01

    A pre-annealing atmospheric pulsed laser exposure was applied to decrease the phase transition (from chemically disordered A1 phase to chemically ordered L1 0 phase) temperature of FePt nano-particles on a Si (100) substrate. Different pre-annealing laser energy densities of 0.024 and 0.079 J/cm2 were utilized to expose the pulsed laser deposition (PLD) FePt thin film samples under atmospheric conditions. Subsequently, FePt thin film samples were annealed at different temperatures of 300 and 400 ºC to observe the influence of laser exposure on the phase transition temperature. The phase transition temperature was decreased from conventional 600 ºC to 400 ºC by one shot pre-annealing atmospheric pulsed laser exposure. (author)

  5. Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing

    Science.gov (United States)

    Ngo, Chi-Vinh; Chun, Doo-Man

    2017-07-01

    Recently, the fabrication of superhydrophobic metallic surfaces by means of pulsed laser texturing has been developed. After laser texturing, samples are typically chemically coated or aged in ambient air for a relatively long time of several weeks to achieve superhydrophobicity. To accelerate the wettability transition from hydrophilicity to superhydrophobicity without the use of additional chemical treatment, a simple annealing post process has been developed. In the present work, grid patterns were first fabricated on stainless steel by a nanosecond pulsed laser, then an additional low-temperature annealing post process at 100 °C was applied. The effect of 100-500 μm step size of the textured grid upon the wettability transition time was also investigated. The proposed post process reduced the transition time from a couple of months to within several hours. All samples showed superhydrophobicity with contact angles greater than 160° and sliding angles smaller than 10° except samples with 500 μm step size, and could be applied in several potential applications such as self-cleaning and control of water adhesion.

  6. New numerical method to study phase transitions and its applications

    International Nuclear Information System (INIS)

    Lee, Jooyoung; Kosterlitz, J.M.

    1991-11-01

    We present a powerful method of identifying the nature of transitions by numerical simulation of finite systems. By studying the finite size scaling properties of free energy barrier between competing states, we can identify unambiguously a weak first order transition even when accessible system sizes are L/ξ < 0.05 as in the five state Potts model in two dimensions. When studying a continuous phase transition we obtain quite accurate estimates of critical exponents by treating it as a field driven first order transition. The method has been successfully applied to various systems

  7. Study of transition probabilities in 192Pt

    International Nuclear Information System (INIS)

    Roulet, C.; Sergolle, H.; Hubert, P.P.; Lindblad, T.

    1978-01-01

    The nucleus 192 Pt is Coulomb excited with 370 MeV 84 Kr projectiles. Levels up to spin 8 + (10 + ) in the ground band and up to 6 + in the γ-band are observed. The B(E2) values implied by the observed yields are compared with predictions of different nuclear models. Particular attention is paid to the ground band transition rates and the rotation-alignment model

  8. Transition probabilities for lines of Cr II, Na II and Sb I by laser produced plasma atomic emission spectroscopy; Probabilidades de transicion de algunos niveles de Cr II, Na II y Sb I medediante espectroscopia de plasma producidos por laser

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, A. M.; Ortiz, M.; Campos, J.

    1995-07-01

    Absolute transition probabilities for lines of CR II, Na II and Sb I were determined by emission spectroscopy of laser induced plasmas. the plasma was produced focusing the emission of a pulsed Nd-Yag laser on solid samples containing the atom in study. the light arising from the plasma region was collected by and spectrometer. the detector used was a time-resolved optical multichannel analyzer (OMA III EG and G). The wavelengths of the measured transitions range from 2000 sto 4100 A. The spectral resolution of the system was 0. 2 A. The method can be used in insulators materials as Cl Na crystals and in metallic samples as Al-Cr and Sn-Sn alloys. to avoid self-absorption effects the alloys were made with low Sb or Cr content. Relative transition probabilities have been determined from measurements of emission-line intensities and were placed on an absolute scale by using, where possible, accurate experimental lifetime values form the literature or theoretical data. From these measurements, values for plasma temperature (8000-24000 K), electron densities ({approx}{approx} 10''16 cm ''-3) and self-absorption coefficients have been obtained. (Author) 56 refs.

  9. Studies into laser ignition of confined pyrotechnics

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, S.R.; Russell, D.A. [Centre for Applied Laser Spectroscopy, DASSR, Defence Academy, Cranfield University, Shrivenham, Swindon (United Kingdom)

    2008-10-15

    Ignition tests were carried out on three different pyrotechnics using laser energy from the multimode output from an Ar-Ion laser (av) at 500 nm and a near-IR diode laser pigtailed to a fibre optic cable and operating at 808 nm. The pyrotechnics investigated were: G20 black powder, SR44 and SR371C. The confined ignition tests were conducted in a specially designed ignition chamber. Pyrotechnics were ignited by a free space beam entering the chamber through an industrial sapphire window in the case of the Ar-ion laser. For the NIR diode laser, fibre was ducted through a block into direct contact with the pyrotechnic. The Ar-Ion laser was chosen as this was found to ignite all three pyrotechnics in the unconfined condition. It also allowed for a direct comparison of confined/unconfined results to be made. The threshold laser flux densities to initiate reproducible ignitions at this wavelength were found to be between {proportional_to}12.7 and {proportional_to}0.16 kW cm{sup -2}. Plotted on the ignition maps are the laser flux densities versus the start of ignition times for the three confined pyrotechnics. It was found from these maps that the times for confined ignition were substantially lower than those obtained for unconfined ignition under similar experimental conditions. For the NIR diode laser flux densities varied between {proportional_to}6.8 and {proportional_to}0.2 kW cm{sup -2}. The minimum ignition times for the NIR diode laser for SR371C ({proportional_to}11.2 ms) and G20 ({proportional_to}17.1 ms) were faster than those achieved by the use of the Ar-ion laser. However, the minimum ignition time was shorter ({proportional_to}11.7 ms) with the Ar-ion laser for SR44. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  10. Phase transitions in LiCoO2 thin films prepared by pulsed laser deposition

    International Nuclear Information System (INIS)

    Huang Rong; Hitosugi, Taro; Fisher, Craig A.J.; Ikuhara, Yumi H.; Moriwake, Hiroki; Oki, Hideki; Ikuhara, Yuichi

    2012-01-01

    Highlights: ► Epitaxial LiCoO 2 thin films were formed on the Al 2 O 3 (0 0 0 1) substrate by PLD at room temperature and annealed at 600 °C in air. ► The orientation relationship between film and substrate is revealed. ► Crystalline phases in the RT deposited and annealed thin films are clearly identified. ► Atomic level interface structure indicates an interface reaction during annealing. ► A phase transition mechanism from fully disordered LiCoO 2 to fully ordered LiCoO 2 is proposed. - Abstract: Microstructures of epitaxial LiCoO 2 thin films formed on the (0 0 0 1) surface of sapphire (α-Al 2 O 3 ) substrates by pulsed laser deposition at room temperature and annealed at 600 °C in air were investigated by a combination of selected-area electron diffraction, high-resolution transmission electron microscopy, spherical-aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, and electron energy-loss spectroscopy. As-deposited LiCoO 2 thin films consisted of epitaxial grains of the fully cation-disordered phase (γ) with a cubic rock-salt structure. During annealing, this cubic-structured phase transformed into the fully ordered trigonal (α) phase oriented with its basal plane parallel to the surface of the sapphire substrate. Although overall the film appeared to be a single crystal, a small number of Co 3 O 4 grains were also observed in annealed thin films, indicating that some Li and O had been lost during processing. The atomically sharp interface between the film and substrate also became rougher during annealing, with step defects being formed, suggesting that a localized reaction occurred at the interface.

  11. Study of laser cladding nuclear valve parts

    International Nuclear Information System (INIS)

    Shi Shihong; Wang Xinlin; Huang Guodong

    1998-12-01

    The mechanism of laser cladding is discussed by using heat transfer model of laser cladding, heat conduction model of laser cladding and convective transfer mass model of laser melt-pool. Subsequently the laser cladding speed limit and the influence of laser cladding parameters on cladding layer structure is analyzed. A 5 kW with CO 2 transverse flow is used in the research for cladding treatment of sealing surface of stop valve parts of nuclear power stations. The laser cladding layer is found to be 3.0 mm thick. The cladding surface is smooth and has no such defects as crack, gas pore, etc. A series of comparisons with plasma spurt welding and arc bead welding has been performed. The results show that there are higher grain grade and hardness, lower dilution and better performances of resistance to abrasion, wear and of anti-erosion in the laser cladding layer. The new technology of laser cladding can obviously improve the quality of nuclear valve parts. Consequently it is possible to lengthen the service life of nuclear valve and to raise the safety and reliability of the production system

  12. TRANSIT

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. TRANSIT. SYSTEM: DETERMINE 2D-POSITION GLOBALLY BUT INTERMITTENT (POST-FACTO). IMPROVED ACCURACY. PRINCIPLE: POLAR SATELLITES WITH INNOVATIONS OF: GRAVITY-GRADIENT ATTITUDE CONTROL; DRAG COMPENSATION. WORKS ...

  13. Transition from oxcarbazepine to eslicarbazepine acetate: A single center study.

    Science.gov (United States)

    Mäkinen, Jussi; Rainesalo, Sirpa; Peltola, Jukka

    2017-03-01

    There is limited clinical evidence for comparison between oxcarbazepine (OXC) and eslicarbazepine acetate (ESL) in terms of tolerability, or how to execute the change from OXC to ESL. We report the process of transitioning patients with focal epilepsy from previous OXC treatment to ESL due to tolerability problems. The rationale for change from OXC is reported, and the outcome with respective to this rationale is analyzed in terms of tolerability and efficacy. The subjects were transitioned overnight from OXC to ESL in a hospital inpatient setting. An evaluation of the effects of the transition was made after 1 and 3 months. All adverse events (AEs) were recorded following the transition period. Subjects were classified by outcome in terms of AEs. Twenty-three subjects were transitioned from OXC to ESL. Fifteen patients OXC-related AEs reduced significantly after transition. Particularly, most of (93%) the AEs presented in the morning resolved after transition to ESL. No patient had an increase in seizure frequency following the transition. The incidence of ESL-related AEs was 39% at 1 month and 13% at 3 month follow-up; however, all patients continued ESL throughout the study period. This study demonstrates that patients suffering from OXC-related AEs improve in terms of tolerability after a switch to ESL with maintaining seizure control. This improvement is more pronounced if the OXC-related AEs are most evident following morning dosing of OXC. Transition can be safely executed in an outpatient setting.

  14. A study of optical design and optimization of laser optics

    Science.gov (United States)

    Tsai, C.-M.; Fang, Yi-Chin

    2013-09-01

    This paper propose a study of optical design of laser beam shaping optics with aspheric surface and application of genetic algorithm (GA) to find the optimal results. Nd: YAG 355 waveband laser flat-top optical system, this study employed the Light tools LDS (least damped square) and the GA of artificial intelligence optimization method to determine the optimal aspheric coefficient and obtain the optimal solution. This study applied the aspheric lens with GA for the flattening of laser beams using collimated laser beam light, aspheric lenses in order to achieve best results.

  15. Airborne laser: a tool to study landscape surface features

    International Nuclear Information System (INIS)

    Ritchie, J.C.; Jackson, T.J.; Everitt, J.H.; Escobar, D.E.; Murphey, J.B.; Grissinger, E.H.

    1992-01-01

    Landscape surface features related to erosion and hydrology were measured using an airborne laser profiler. The airborne laser profiler made 4,000 measurements per second with a recording accuracy of 5 cm (1.9 inches) on a single measurement. Digital data from the laser are recorded and analyzed with a personal computer. These airborne laser profiles provide information on surface landscape features. Topography and canopy heights, cover, and distribution of natural vegetation were determined in studies in South Texas. Laser measurements of shrub cover along flightlines were highly correlated (R 2 = 0.98) with ground measurements made with line-intercept methods. Stream channel cross sections on Goodwin Creek in Mississippi were measured quickly and accurately with airborne laser data. Airborne laser profile data were used to measure small gullies in a level fallow field and in field with mature soybeans. While conventional ground-based techniques can be used to make these measurements, airborne laser profiler techniques allow data to be collected quickly, at a high density, and in areas that are essentially inaccessible for ground surveys. Airborne laser profiler data can quantify landscape features related to erosion and runoff, and the laser proler has the potential to be a useful tool for providing other data for studying and managing natural resources

  16. Studies of the Influence of Beam Profile and Cooling Conditions on the Laser Deposition of a Directionally-Solidified Superalloy

    Directory of Open Access Journals (Sweden)

    Shuo Yang

    2018-02-01

    Full Text Available In the laser deposition of single crystal and directionally-solidified superalloys, it is desired to form laser deposits with high volume fractions of columnar grains by suppressing the columnar-to-equiaxed transition efficiently. In this paper, the influence of beam profile (circular and square shapes and cooling conditions (natural cooling and forced cooling on the geometric morphology and microstructure of deposits were experimentally studied in the laser deposition of a directionally-solidified superalloy, IC10, and the mechanisms of influence were revealed through a numerical simulation of the thermal processes during laser deposition. The results show that wider and thinner deposits were obtained with the square laser beam than those with the circular laser beam, regardless of whether natural or forced cooling conditions was used. The heights and contact angles of deposits were notably increased due to the reduced substrate temperatures by the application of forced cooling for both laser beam profiles. Under natural cooling conditions, columnar grains formed epitaxially at both the center and the edges of the deposits with the square laser beam, but only at the center of the deposits with the circular laser beam; under forced cooling conditions, columnar grains formed at both the center and the edges of deposits regardless of the laser beam profile. The high ratios of thermal gradient and solidification velocity in the height direction of the deposits were favorable to forming deposits with higher volume fractions of columnar grains.

  17. Theoretical studies of transition metal complexes with nitriles and isocyanides

    International Nuclear Information System (INIS)

    Kuznetsov, Maksim L

    2002-01-01

    Theoretical studies of transition metal complexes with nitriles and isocyanides are reviewed. The electronic structures and the nature of coordination bonds in these complexes are discussed. The correlation between the electronic structures of transition metal complexes with nitriles and isocyanides and their structural properties, spectroscopic characteristics, and reactivities are considered. The bibliography includes 121 references.

  18. Study of optical confinement of quantum cascade lasers and applications to detection

    International Nuclear Information System (INIS)

    Moreau, Virginie

    2008-01-01

    Quantum cascade lasers have been invented in 1994 and they have already established themselves as the semiconductor laser source of choice in the mid- and far-infrared ranges of the electromagnetic spectrum. As most molecules of chemical interest exhibit roto-vibrational transitions in these spectral ranges, quantum cascade lasers are especially suited for applications such as spectroscopy, trace gas detection or medical imaging. One of the current leading research axis targets the device optimization and miniaturization, with possible applications in detection microsystems. This PhD thesis work focused on the study and optimization of the vertical optical confinement in quantum cascade lasers featuring optical waveguides without top cladding layers. These structures are interesting because they are compatible with two different guiding mechanisms at the same time, i.e. surface-plasmons and air confinement. The study of the characteristics of the optical mode and of the electrical current dispersion allowed us to conceive original structures which open new perspectives, for instance in the domain of analytic detection in a fluidic environment. Furthermore, we have shown that the observation by near field microscopy is a powerful tool to characterize and understand quantum cascade lasers. Finally, we have laid the foundations for the optimization of miniaturized arrays of single-mode lasers based on photonic crystal technology. (author) [fr

  19. Absolute transition probabilities in the NeI 3p-3s fine structure by beam-gas-dye laser spectroscopy

    International Nuclear Information System (INIS)

    Hartmetz, P.; Schmoranzer, H.

    1983-01-01

    The beam-gas-dye laser two-step excitation technique is further developed and applied to the direct measurement of absolute atomic transition probabilities in the NeI 3p-3s fine-structure transition array with a maximum experimental error of 5%. (orig.)

  20. Properties of transition metal-doped zinc chalcogenide crystals for tunable IR laser radiation

    International Nuclear Information System (INIS)

    DeLoach, L.D.; Page, R.H.; Wilke, G.D.

    1995-01-01

    The spectroscopic properties of Cr 2+ , Co 2+ , and Ni 2+ -doped single crystals of ZnS, ZnSe, and ZnTe have been investigated to understand their potential application as mid-IR tunable solid-state laser media. The spectroscopy indicated divalent Cr was the most favorable candidate for efficient room temperature lasing, and accordingly, a laser-pumped laser demonstration of Cr:ZnS and Cr:ZnSe has been performed. The lasers' output were peaked at ∼ 2.35 μm and the highest measured slope efficiencies were ∼ 20% in both cases

  1. KrF laser kinetics studies

    International Nuclear Information System (INIS)

    Mandl, A.; Klimek, D.; Parks, J.H.

    1984-01-01

    A series of measurements characterizing an e beam pumped KrF* laser was carried out using a 200-nsec e-beam pulse having a rise time of 25 nsec at current densities up to 50 A/cm 2 . These pump conditions are relevent for inertial confinement fusion laser drivers. The measurements include fluorescence efficiency, sidelight suppression of the fluorescence during lasing, and laser energy output over a wide range of laser parameters including: total density 0.5--2.0 amagats, temperature 300--400 K, fluorine density 0.15%--0.5%, current density 38--50 A/cm 2 and various mirror transmissions. This data was used to verify and refine a model of KrF* kinetics which was then used to estimate the performance of an angular multiplexed power amplifier suitable for laser fusion applications

  2. Older Persons’ Transitions in Care (OPTIC: a study protocol

    Directory of Open Access Journals (Sweden)

    Cummings Greta G

    2012-12-01

    Full Text Available Abstract Background Changes in health status, triggered by events such as infections, falls, and geriatric syndromes, are common among nursing home (NH residents and necessitate transitions between NHs and Emergency Departments (EDs. During transitions, residents frequently experience care that is delayed, unnecessary, not evidence-based, potentially unsafe, and fragmented. Furthermore, a high proportion of residents and their family caregivers report substantial unmet needs during transitions. This study is part of a program of research whose overall aim is to improve quality of care for frail older adults who reside in NHs. The purpose of this study is to identify successful transitions from multiple perspectives and to identify organizational and individual factors related to transition success, in order to inform improvements in care for frail elderly NH residents during transitions to and from acute care. Specific objectives are to: 1. define successful and unsuccessful elements of transitions from multiple perspectives; 2. develop and test a practical tool to assess transition success; 3. assess transition processes in a discrete set of transfers in two study sites over a one year period; 4. assess the influence of organizational factors in key practice locations, e.g., NHs, emergency medical services (EMS, and EDs, on transition success; and 5. identify opportunities for evidence-informed management and quality improvement decisions related to the management of NH – ED transitions. Methods/Design This is a mixed-methods observational study incorporating an integrated knowledge translation (IKT approach. It uses data from multiple levels (facility, care unit, individual and sources (healthcare providers, residents, health records, and administrative databases. Discussion Key to study success is operationalizing the IKT approach by using a partnership model in which the OPTIC governance structure provides for team decision-makers and

  3. Two-photon laser-induced fluorescence studies of HS radicals, DS radicals, and I atoms

    Energy Technology Data Exchange (ETDEWEB)

    Tiee, J J; Ferris, M J; Loge, G W; Wampler, F B

    1983-04-15

    A two-photon laser-induced excitation and fluorescence technique has been used to study the A /sup 2/..sigma../sup +/ - X/sup 2/PI transition of HS and DS radicals and various high-lying /sup 4/P/sup 0/, /sup 2/D/sup 0/, and /sup 4/D/sup 0/ states of the I atom. The two-photon excitation cross sections and detection sensitivity are discussed. 13 references, 5 figures.

  4. Kinetic studies following state-selective laser excitation: Annual performance report for the period March 15, 1987-March 14, 1988

    International Nuclear Information System (INIS)

    Keto, J.W.

    1987-11-01

    The objective of this contract is the study of state-to-state, electronic energy transfer reactions following two-photon laser excitation. We have specifically been studying reactions of Xe 5p 5 6p because of their relevance to the XeCl excimer laser. We are studying deactivation reactions in collisions with heavy atoms such as Ar, Kr, and Xe and reactive collisions with chlorides. The reactants are excited by multiphoton laser absorption. Product channels are observed by their fluorescence, or in experiments in the coming months by laser induced fluorescence using a second color laser. Reaction rates are measured by observing the time dependent decay of signals from reactant and product channels. In addition we measure interaction potentials of the reactants by laser spectroscopy where the laser induced fluorescence or ionization is measured as a function of laser wavelength (excitation spectra) or by measuring fluorescence spectra at fixed laser frequencies with monochromators. The spectra are obtained in the form of either lineshapes or individual lines from rovibrational transitions of bound states. 4 figs

  5. Critical behavior within 20 fs drives the out-of-equilibrium laser-induced magnetic phase transition in nickel.

    Science.gov (United States)

    Tengdin, Phoebe; You, Wenjing; Chen, Cong; Shi, Xun; Zusin, Dmitriy; Zhang, Yingchao; Gentry, Christian; Blonsky, Adam; Keller, Mark; Oppeneer, Peter M; Kapteyn, Henry C; Tao, Zhensheng; Murnane, Margaret M

    2018-03-01

    It has long been known that ferromagnets undergo a phase transition from ferromagnetic to paramagnetic at the Curie temperature, associated with critical phenomena such as a divergence in the heat capacity. A ferromagnet can also be transiently demagnetized by heating it with an ultrafast laser pulse. However, to date, the connection between out-of-equilibrium and equilibrium phase transitions, or how fast the out-of-equilibrium phase transitions can proceed, was not known. By combining time- and angle-resolved photoemission with time-resolved transverse magneto-optical Kerr spectroscopies, we show that the same critical behavior also governs the ultrafast magnetic phase transition in nickel. This is evidenced by several observations. First, we observe a divergence of the transient heat capacity of the electron spin system preceding material demagnetization. Second, when the electron temperature is transiently driven above the Curie temperature, we observe an extremely rapid change in the material response: The spin system absorbs sufficient energy within the first 20 fs to subsequently proceed through the phase transition, whereas demagnetization and the collapse of the exchange splitting occur on much longer, fluence-independent time scales of ~176 fs. Third, we find that the transient electron temperature alone dictates the magnetic response. Our results are important because they connect the out-of-equilibrium material behavior to the strongly coupled equilibrium behavior and uncover a new time scale in the process of ultrafast demagnetization.

  6. Tunable Landau-Zener transitions using continuous- and chirped-pulse-laser couplings

    Science.gov (United States)

    Sarreshtedari, Farrokh; Hosseini, Mehdi

    2017-03-01

    The laser coupled Landau-Zener avoided crossing has been investigated with an aim towards obtaining the laser source parameters for precise controlling of the state dynamics in a two-level quantum system. The conventional Landau-Zener equation is modified for including the interaction of the system with a laser field during a bias energy sweep and the obtained Hamiltonian is numerically solved for the investigation of the two-state occupation probabilities. We have shown that in the Landau-Zener process, using an additional laser source with controlled amplitude, frequency, and phase, the system dynamics could be arbitrarily engineered. This is while, by synchronous frequency sweeping of a chirped-pulse laser, the system could be guided into a resonance condition, which again gives the remarkable possibility for precise tuning and controlling of the quantum system dynamics.

  7. The 2P1/2 → 2P3/2 laser transition in atomic iodine and the problem of search for signals from extraterrestrial intelligence

    International Nuclear Information System (INIS)

    Kutaev, Yu F; Mankevich, S K; Nosach, O Yu; Orlov, E P

    2007-01-01

    It is proposed to search for signals from extraterrestrial intelligence (ETI) at a wavelength of 1.315 μm of the laser 2 P 1/2 → 2 P 3/2 transition in the atomic iodine, which can be used for this purpose as the natural frequency reference. The search at this wavelength is promising because active quantum filters (AQFs) with the quantum sensitivity limit have been developed for this wavelength, which are capable of receiving laser signals, consisting of only a few photons, against the background of emission from a star under study. In addition, high-power iodine lasers emitting diffraction-limited radiation at 1.315 μm have been created, which highly developed ETI also can have. If a ETI sends in our direction a diffraction-limited 10-ns, 1-kJ laser pulse with the beam diameter of 10 m, a receiver with an AQF mounted on a ten-meter extra-atmospheric optical telescope can detect this signal at a distance of up to 300 light years, irrespective of the ETI position on the celestial sphere. The realisation of the projects for manufacturing optical telescopes of diameter 30 m will increase the research range up to 2700 light years. A weak absorption of the 1.315-μm radiation in the Earth atmosphere (the signal is attenuated by less than 20%) allows the search for ETI signals by using ground telescopes equipped with adaptive optical systems. (laser applications and other topics in quantum electronics)

  8. Energy Transition in the Nebular City: Connecting Transition Thinking, Metabolism Studies, and Urban Design

    Directory of Open Access Journals (Sweden)

    Griet Juwet

    2018-03-01

    Full Text Available Transforming urban infrastructures is an essential part of creating more sustainable urban regions. But rethinking these complex systems requires a better understanding of their spatial dimensions and their relation with urban morphology and spatial structure. This paper addresses that gap by examining different conceptualizations of technical infrastructure and space in science, technology and society studies (STS, transition thinking, urban metabolism studies, and urban political ecology, and draws connections with the spatial perspective of urban planning and design. It illustrates and tests these concepts through the case of energy transition in the Flemish region of Belgium. Transport and supply networks have played a crucial role in facilitating, structuring, and reproducing the region’s characteristic dispersed and energy-intensive urban landscape. Bringing different disciplinary perspectives together, the research broadens the conceptualization of the spatial dimension in transition thinking, and identifies useful concepts and design parameters for urban design to engage with the technical and socio-political complexity of transforming urban infrastructure. It reveals the energy transition as an inherently spatial project, and explores the spatially and socio-politically transformative potential of the transition towards a new energy system.

  9. Numerical Study of Transition of an Annular Lift Fan Aircraft

    Directory of Open Access Journals (Sweden)

    Yun Jiang

    2016-09-01

    Full Text Available The present study aimed at studying the transition of annular lift fan aircraft through computational fluid dynamics (CFD simulations. The oscillations of lift and drag, the optimization for the figure of merit, and the characteristics of drag, yawing, rolling and pitching moments in transition are studied. The results show that a two-stage upper and lower fan lift system can generate oscillations of lift and drag in transition, while a single-stage inner and outer fan lift system can eliminate the oscillations. The characteristics of momentum drag of the single-stage fans in transition are similar to that of the two-stage fans, but with the peak of drag lowered from 0.63 to 0.4 of the aircraft weight. The strategy to start transition from a negative angle of attack −21° further reduces the peak of drag to 0.29 of the weight. The strategy also reduces the peak of pitching torque, which needs upward extra thrusts of 0.39 of the weight to eliminate. The peak of rolling moment in transition needs differential upward thrusts of 0.04 of the weight to eliminate. The requirements for extra thrusts in transition lead to a total thrust–weight ratio of 0.7, which makes the aircraft more efficient for high speed cruise flight (higher than 0.7 Ma.

  10. Radionuclide Esophageal Transit Study in the Esophageal Motility Disorders

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jae Gol; Lee, Min Jae; Song, Chi Wook [Korea University College of Medicine, Seoul (Korea, Republic of)

    1993-07-15

    Esophageal motility was evaluated from the analysis of 10 consecutive swallows using liquid bolus containing 0.5 mCi of {sup 99m}Tc tin colloid. We have reviewed our experience of esophageal transit study in the 20 normal volunteers and 55 patients with dysphagia that was not related to mechanical obstruction. The purpose of this study is to measure the esophageal transit in normal subjects and in patients with various esophageal motility disorders. The overall sensitivity and specificity of radionuclide esophageal transit study in detecting esophageal motor abnormality were compared with manometric results as a gold standard, which were 80% and 100% respectively. Radionuclide transit study is a safe, rapid, noninvasive test and suitable as a screening test for esophageal motor disorders.

  11. Radionuclide Esophageal Transit Study in the Esophageal Motility Disorders

    International Nuclear Information System (INIS)

    Choi, Jae Gol; Lee, Min Jae; Song, Chi Wook

    1993-01-01

    Esophageal motility was evaluated from the analysis of 10 consecutive swallows using liquid bolus containing 0.5 mCi of 99m Tc tin colloid. We have reviewed our experience of esophageal transit study in the 20 normal volunteers and 55 patients with dysphagia that was not related to mechanical obstruction. The purpose of this study is to measure the esophageal transit in normal subjects and in patients with various esophageal motility disorders. The overall sensitivity and specificity of radionuclide esophageal transit study in detecting esophageal motor abnormality were compared with manometric results as a gold standard, which were 80% and 100% respectively. Radionuclide transit study is a safe, rapid, noninvasive test and suitable as a screening test for esophageal motor disorders.

  12. Thermal stress modification in regenerated fiber Bragg grating via manipulation of glass transition temperature based on CO₂-laser annealing.

    Science.gov (United States)

    Lai, Man-Hong; Lim, Kok-Sing; Gunawardena, Dinusha S; Yang, Hang-Zhou; Chong, Wu-Yi; Ahmad, Harith

    2015-03-01

    In this work, we have demonstrated thermal stress relaxation in regenerated fiber Bragg gratings (RFBGs) by using direct CO₂-laser annealing technique. After the isothermal annealing and slow cooling process, the Bragg wavelength of the RFBG has been red-shifted. This modification is reversible by re-annealing and rapid cooling. It is repeatable with different cooling process in the subsequent annealing treatments. This phenomenon can be attributed to the thermal stress modification in the fiber core by means of manipulation of glass transition temperature with different cooling rates. This finding in this investigation is important for accurate temperature measurement of RFBG in dynamic environment.

  13. An experimental study on downstream of the transition of the chemically reacting liquid round free jet

    International Nuclear Information System (INIS)

    Hong, S.D.; Sugii, Y.; Okamoto, K.; Madarame, H.

    2002-01-01

    An experimental study was conducted on the chemically reacting liquid round free jet, Laser Induced Fluorescence (LIF) technique was adopted to evaluate the diffusion width of the jet into liquid streams. In the fluid engineering, it is very important to evaluate the characteristics of reacting jet for the safety of the nuclear reactor. In this study, the jet profile of downstream region far away from the transition point was evaluated, providing comparisons between reacting and non-reacting jet case. The concentration of the jet solution was varied from 0.01 mol/L to 0.5 mol/L in reacting cases. In the downstream far away from the transition point, the jet profiles between reacting cases and non-reacting cases were visualized quite different. It was concluded that the chemical reaction affects the momentum diffusion of the jet in the downstream region. (author)

  14. Simultaneous X-ray imaging and diffraction study of shock propagation and phase transition in silicon

    Science.gov (United States)

    Galtier, Eric

    2017-06-01

    X-ray phase contrast imaging technique using a free electron laser have observed the propagation of laser-driven shock waves directly inside materials. While providing images with few hundred nanometers spatial resolution, access to more quantitative information like the material density and the various shock front speeds remain challenging due to imperfections in the images limiting the convergence in the reconstruction algorithm. Alternatively, pump-probe X-ray diffraction (XRD) is a robust technique to extract atomic crystalline structure of compressed matter, providing insight into the kinetics of phase transformation and material response to stress. However, XRD by itself is not sufficient to extract the equation of state of the material under study. Here we report on the use of the LCLS free electron laser as a source of a high-resolution X-ray microscopy enabling the direct imaging of shock waves and phase transitions in optically opaque silicon. In this configuration, no algorithm is necessary to extract the material density and the position of the shock fronts. Simultaneously, we probed the crystalline structure via XRD of the various phases in laser compressed silicon. E. Galtier, B. Nagler, H. J. Lee, S. Brown, E. Granados, A. Hashim, E. McBride, A. Mackinnon, I. Nam, J. Zimmerman (SLAC) A. Gleason (Stanford, LANL) A. Higginbotham (University of York) A. Schropp, F. Seiboth (DESY).

  15. IDA Gamma-Ray Laser Annual Summary Report (1990): Investigation of the Feasibility of Developing A Laser Using Nuclear Transitions

    Science.gov (United States)

    1992-04-01

    Broadening in the Theory of Superradiant Emission," Acta Physica Polonica , Vol. A39, 1971, pp. 633-638. 8. B. Balko, I.W. Kay, and J. Neuberger, IDA...Cuopy 1 3 of 60 copies AD-A259 475 IDA PAPER P-2533 IDA GAMMA-RAY LASER ANNUAL SUMMARY REPORT (1990) Investigation of the Feasibility of Developing a ...embody results of major projects which ( a ) have a direct bearing on decisions affecting major programs, (b) address issues of significant concern to

  16. Laser-material interactions: A study of laser energy coupling with solids

    Energy Technology Data Exchange (ETDEWEB)

    Shannon, Mark Alan [Univ. of California, Berkeley, CA (United States)

    1993-11-01

    This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heating of opaque solids that have not undergone phase-change. Of main interest is the physical significance of the shape, magnitude, and phase for the temporal profile of the deflection signal. Considered are the effects that thermophysical properties, boundary conditions, and geometry of the target and optical probe-beam have on the deflection response. PTD is shown to monitor spatial and temporal changes in heat flux leaving the surface due to changes in laser energy coupling. The PTD technique is then extended to detect phase-change at the surface of a solid target. Experimental data shows the onset of melt for indium and tin targets. The conditions for which melt can be detected by PTD is analyzed in terms of geometry, incident power and pulse length, and thermophysical properties of the target and surroundings. Next, monitoring high-powered laser ablation of materials with stress-power is introduced. The motivation for considering stress-power is given, followed by a theoretical discussion of stress-power and how it is determined experimentally. Experiments are presented for the ablation of aluminum targets as a function of energy and intensity. The stress-power response is analyzed for its physical significance. Lastly, the influence of plasma-shielding during high-powered pulsed laser-material interactions is considered. Crater size, emission, and stress-power are measured to determine the role that the gas medium and laser pulse length have on plasma shielding.

  17. Laser-material interactions: A study of laser energy coupling with solids

    International Nuclear Information System (INIS)

    Shannon, M.A.; California Univ., Berkeley, CA

    1993-11-01

    This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heating of opaque solids that have not undergone phase-change. Of main interest is the physical significance of the shape, magnitude, and phase for the temporal profile of the deflection signal. Considered are the effects that thermophysical properties, boundary conditions, and geometry of the target and optical probe-beam have on the deflection response. PTD is shown to monitor spatial and temporal changes in heat flux leaving the surface due to changes in laser energy coupling. The PTD technique is then extended to detect phase-change at the surface of a solid target. Experimental data shows the onset of melt for indium and tin targets. The conditions for which melt can be detected by PTD is analyzed in terms of geometry, incident power and pulse length, and thermophysical properties of the target and surroundings. Next, monitoring high-powered laser ablation of materials with stress-power is introduced. The motivation for considering stress-power is given, followed by a theoretical discussion of stress-power and how it is determined experimentally. Experiments are presented for the ablation of aluminum targets as a function of energy and intensity. The stress-power response is analyzed for its physical significance. Lastly, the influence of plasma-shielding during high-powered pulsed laser-material interactions is considered. Crater size, emission, and stress-power are measured to determine the role that the gas medium and laser pulse length have on plasma shielding

  18. Effect of exponential density transition on self-focusing of q-Gaussian laser beam in collisionless plasma

    Science.gov (United States)

    Valkunde, Amol T.; Vhanmore, Bandopant D.; Urunkar, Trupti U.; Gavade, Kusum M.; Patil, Sandip D.; Takale, Mansing V.

    2018-05-01

    In this work, nonlinear aspects of a high intensity q-Gaussian laser beam propagating in collisionless plasma having upward density ramp of exponential profiles is studied. We have employed the nonlinearity in dielectric function of plasma by considering ponderomotive nonlinearity. The differential equation governing the dimensionless beam width parameter is achieved by using Wentzel-Kramers-Brillouin (WKB) and paraxial approximations and solved it numerically by using Runge-Kutta fourth order method. Effect of exponential density ramp profile on self-focusing of q-Gaussian laser beam for various values of q is systematically carried out and compared with results Gaussian laser beam propagating in collisionless plasma having uniform density. It is found that exponential plasma density ramp causes the laser beam to become more focused and gives reasonably interesting results.

  19. Scintigraphic colonic transit study in children with chronic constipation

    International Nuclear Information System (INIS)

    Yano, Tsunehiro; Uemura, Sadashige; Nakaoka, Tatsuo; Nakagawa, Yoshikiyo; Tanimoto, Terutaka; Sone, Teruki

    2008-01-01

    Chronic constipation can be caused either by slow colonic transit or by functional fecal retention. The treatment strategy for chronic constipation should be based on its etiology. Scintigraphic colonic transit study (SCTS) is useful for dividing the cause of the constipation into slow colonic transit and functional fecal retention. SCTS is also useful for judging the therapeutic effect and postoperative intestinal motility of Hirschsprung's disease, anorectal molformation, and others. As SCTS is a safe, simple, and painless examination, it is one of the most important examinations in evaluating chronic constipation. (author)

  20. Study into penetration speed during laser cutting of brain tissues.

    Science.gov (United States)

    Yilbas, Z; Sami, M; Patiroglu, T

    1998-01-01

    The applications of CO2 continuous-wave lasers in neurosurgery have become important in recent years. Theoretical considerations of laser applicability in medicine are subsequently confirmed experimentally. To obtain precision operation in the laser cutting process, further theoretical developments and experimental studies need to be conducted. Consequently, in the present study, the heat transfer mechanism taking place during laser-tissue interaction is introduced using Fourier theory. The results obtained from the theoretical model are compared with the experimental results. In connection with this, an experiment is designed to measure the penetration speed during the laser cutting process. The measurement is carried out using an optical method. It is found that both results for the penetration speed obtained from the theory and experiment are in a good agreement.

  1. Comparative study on Pulsed Laser Deposition and Matrix Assisted Pulsed Laser Evaporation of urease thin films

    International Nuclear Information System (INIS)

    Smausz, Tomi; Megyeri, Gabor; Kekesi, Renata; Vass, Csaba; Gyoergy, Eniko; Sima, Felix; Mihailescu, Ion N.; Hopp, Bela

    2009-01-01

    Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1-10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm 2 . Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth 'base' layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional 'absorptive matrix' model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.

  2. Study of the Transition Flow Regime using Monte Carlo Methods

    Science.gov (United States)

    Hassan, H. A.

    1999-01-01

    This NASA Cooperative Agreement presents a study of the Transition Flow Regime Using Monte Carlo Methods. The topics included in this final report are: 1) New Direct Simulation Monte Carlo (DSMC) procedures; 2) The DS3W and DS2A Programs; 3) Papers presented; 4) Miscellaneous Applications and Program Modifications; 5) Solution of Transitional Wake Flows at Mach 10; and 6) Turbulence Modeling of Shock-Dominated Fows with a k-Enstrophy Formulation.

  3. Direct solar pumping of semiconductor lasers: A feasibility study

    Science.gov (United States)

    Anderson, Neal G.

    1992-01-01

    This report describes results of NASA Grant NAG-1-1148, entitled Direct Solar Pumping of Semiconductor Lasers: A Feasibility Study. The goals of this study were to provide a preliminary assessment of the feasibility of pumping semiconductor lasers in space with directly focused sunlight and to identify semiconductor laser structures expected to operate at the lowest possible focusing intensities. It should be emphasized that the structures under consideration would provide direct optical-to-optical conversion of sunlight into laser light in a single crystal, in contrast to a configuration consisting of a solar cell or storage battery electrically pumping a current injection laser. With external modulation, such lasers could perhaps be efficient sources for intersatellite communications. We proposed specifically to develop a theoretical model of semiconductor quantum-well lasers photopumped by a broadband source, test it against existing experimental data where possible, and apply it to estimating solar pumping requirements and identifying optimum structures for operation at low pump intensities. These tasks have been accomplished, as described in this report of our completed project. The report is organized as follows: Some general considerations relevant to the solar-pumped semiconductor laser problem are discussed in Section 2, and the types of structures chosen for specific investigation are described. The details of the laser model we developed for this work are then outlined in Section 3. In Section 4, results of our study are presented, including designs for optimum lattice-matched and strained-layer solar-pumped quantum-well lasers and threshold pumping estimates for these structures. It was hoped at the outset of this work that structures could be identified which could be expected to operate continuously at solar photoexcitation intensities of several thousand suns, and this indeed turned out to be the case as described in this section. Our project is

  4. [In-transit metastasis in melanoma: Efficacy of topical imiquimod combined with carbon dioxide laser or with electrocautery].

    Science.gov (United States)

    Elfatoiki, F-Z; Longvert, C; Clerici, T; Bourgault-Villada, I; Roudier-Pujol, C; Vasseur, E; Saiag, P

    2014-02-01

    In-transit metastases in cutaneous melanoma are common and difficult to manage. Therapy is mainly palliative. Use of topical imiquimod has been assessed for surface metastases. We report on four patients with cutaneous melanoma metastases treated with topical imiquimod associated with carbon dioxide laser in the first two patients and with electrocoagulation in the two others. For two patients, we noted complete regression of the lesions after 15 and 18 months. For the two others, treatment was stopped after 9 to 10 months because of progression of subcutaneous metastasis and distant metastasis. Topical imiquimod is an alternative treatment used in superficial in-transit metastasis of melanoma. Its use as a monotherapy is sometimes ineffective. We elected to use combined pre-treatment with carbon dioxide laser or electrocoagulation in order to potentiate the action of imiquimod. This simple and inexpensive therapeutic strategy constitutes a palliative treatment that can allow prolonged local control of cutaneous metastasis. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  5. Unresolved transition array based water window soft x-ray source by laser-produced high-Z plasma

    International Nuclear Information System (INIS)

    Higashiguchi, Takeshi; Dunne, Padraig; O'Sullivan, Gerry

    2013-01-01

    We demonstrate a table-top broadband emission water window source based on laser-produced high-Z plasmas. resonance emission from multiply charged ions merges to produce intense unresolved transition arrays (UTAs) in the 2 to 4 nm region, extending below the carbon K edge (4.37 nm). Arrays resulting from n=4-n=4 transitions are overlaid with n=4-n=5 emission and shift to shorter wavelength with increasing atomic number. An outline of a microscope design for single-shot live cell imaging is proposed based on a bismuth plasma UTA source, coupled to multilayer mirror optics. At power densities available from 'table-top' solid-state lasers, comparison of emission from a number of targets has shown that 3d-4f UTA in zirconium plasmas have highest overall brightness and in an imaging system based on reflective multilayer mirrors, may, depending on bandwidth, have superior performance than either line or broader-band sources. (author)

  6. Laser-welded ureteral anastomoses: experimental studies with three techniques.

    Science.gov (United States)

    Gürpinar, T; Gürer, S; Kattan, M W; Wang, L; Griffith, D P

    1996-01-01

    Tissue welding with laser energy is a new technique for reconstructive surgery. The potential advantages of laser welding are (a) lack of foreign body reaction, (b) decreased operative time, (c) less tissue manipulation, and (d) effective union of tissues equivalent to sutured anastomoses. We have performed ureteral anastomoses in adult mongrel dogs using a KTP 532 nm laser at an intensity of 1.4 W. Multiple "spot welds" of 1-s duration were utilized in a single layer anastomosis. Laser-welded anastomoses were performed with and without protein solder (33% and 50% human albumin) and were compared to sutured anastomoses. The laser-welded anastomoses required less operative time and provided bursting pressure levels similar to those of traditional sutured anastomoses. There was no advantage or disadvantage to the addition of human albumin as a solder in these experimental studies.

  7. Study on process of laser cladded nuclear valve parts

    International Nuclear Information System (INIS)

    Zhang Chunliang

    2000-01-01

    The microstructure and performances of the Co-base alloy coatings that are formed by laser cladding, plasma spurt welding and arc surfacing on the nuclear valve-sealing surface have been studied and compared. The combination costs of laser cladding, plasma spurt welding and arc, surfacing have been analyzed and compared. The results showed that the laser cladding processing has the advantages of high efficiency, low energy cost, a little machining allowance, high rate of finished products and low combination cost, compared with plasma spurt welding processing and arc surfacing processing. The laser cladding technology can improve the qualities of nuclear valve parts and increase their service life. Therefore, the laser cladding processing is a new technology with developing potential

  8. Plasma interpenetration study on the Omega laser facility

    Science.gov (United States)

    Le Pape, Sebastien; Divol, Laurent; Ross, Steven; Wilks, Scott; Amendt, Peter; Berzak Hopkins, Laura; Huser, Gael; Moody, John; MacKinnon, Andy; Meezan, Nathan

    2016-10-01

    The Near Vacuum Campaign on the National Ignition Facility has sparked an interest on the nature of the gold/carbon interface at high velocity, high electron temperature, low-electron density. Indeed radiation-hydrodynamic simulations have been unable to accurately reproduce the experimental shape of the hot spot resulting from implosion driven in Near Vacuum Holhraum. The experimental data are suggesting that the inner beams are freely propagating to the waist of the hohlraum when simulations predict that a density ridge at the gold/carbon interface blocks the inner beams. The discrepancy between experimental data and simulation might be explained by the fluid description of the plasma interface in a rad-hydro code which is probably not valid in when two plasma at high velocity, high temperature are meeting. To test our assumption, we went to the Omega laser facility to study gold/carbon interface in the relevant regime. Time resolved images of the self-emission as well as Thomson scattering data will be presented. For the first time, a transition from a multifluid to a single fluid is observed as plasmas are interacting. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

  9. Status of fiber lasers study of on ytterbium doped fiber laser and laser spectroscopy of doped fibers

    International Nuclear Information System (INIS)

    Magne, S.

    1994-07-01

    This work shows all the advantages and drawbacks of the rare-earth-doped fiber lasers and fiber optical amplifiers, pointing out their potential use for instrumentation and optical fiber sensor technology. The theory of light propagation in optical fibers is presented in order to understand the manufacturing methods. A comparative study of preform surface and concentration analysis is performed. The gain behaviour is also thoroughly examined. A synthesis of all technological parameters of the fiber laser is then established and all technologies of the constituting integrated components are reviewed and compared. The experimental techniques mainly involve: site selective excitation tunability, cooperative luminescence, oxidation state changes induced by gamma irradiation, ytterbium-doped mono-mode continuous wave tunable three-level fiber laser. (TEC). 622 refs., 176 figs

  10. Inuit Health in Transition: the Nuka study

    DEFF Research Database (Denmark)

    Bjerregaard, Peter

    biological samples. The studies in Nunavik and Greenland are not identical but share protocols on diabetes, heart disease, diet, smoking, social capital, self rated health, gambling and many other topics. The study is being geographically expanded to cover also Nunavut, Labrador and East Greenland......, and comparable studies have yielded data from Alaska Natives and Norwegian Sami. A number of researchers will present results from the study at this meeting and we shall hear a lot about the link between diet and health. I will take one step back and look at the social determinants of dietary patterns...... in Greenland in a life course perspective. First different ways to determine dietary patterns will be examined; then the association of parents' background, childhood conditions, education, place of residence, job and wealth with diet will be analysed. Finally, the association of diet with other determinants...

  11. Study abroad: perspectives on transitions to adulthood

    OpenAIRE

    Nielsen, Katherine

    2014-01-01

    The Irish immrama literary style seems the most appropriate way to represent student narratives based on their study abroad experiences in Ireland. The chapters containing the\\ud immrama of students are an ethnographic experiment in which the reflexivity students demonstrated through the interview process is presented in narrative form. This writing style provides the context for the examination of issues related to academic aspirations, professional, and personal wandering, and how study abr...

  12. Gallium colonic transit study patterns in obstructive defecation

    International Nuclear Information System (INIS)

    Bartholomeusz, F.D.L.; Sun, W.M.; Gaffney, R.; Ganesananthan, S.

    1999-01-01

    Full text: Idiopathic constipation may be due to delayed colonic transit or ano-rectal dysfunction and obstructive defecation. The aim of this study was to relate patterns of colonic transit to results of ano-rectal manometry. Sixteen patients (4 males, 12 females, age 20-58 years) were studied. All underwent ano-rectal manometric studies and colonic transit studies. The transit studies were performed following the oral ingestion of 4 MBq 67 Gacitrate with images performed at 6, 24, 48 and 72 h. Computed data on half clearance times (T 1/2 ), mean activity positions (MAP) and segmental tracer retention were obtained. Five patients had normal ano-rectal manometry, 7 decreased rectal sensation and 4 absent or paradoxical ano-rectal reflex (anismus). The T 1/2 for subjects with normal manometry was 78.5 ± 11.9 h, decreased rectal sensation 73 ± 4.9 h and the anismus group 52 ± 12.1 h (P < 0.05). Total retention at 72 h was less at 56 ± 3.73 h in the anismus group compared to normal manometry (74.7 ± 12.2) and decreased rectal sensation (90.7 ± 12.1), with higher MAP and less tracer in the right colon at 48 h in the anismus group (P < 0.05). The results indicate that colonic transit studies in constipated patients with anismus have different patterns to those with normal anorectal manometry or decreased rectal sensation

  13. Experimental study on concrete cutting by CO2 laser beam

    International Nuclear Information System (INIS)

    Kutsumizu, Akira; Tomura, Hidemasa; Wakizaka, Tatsuya; Hishikawa, Kyoichi; Moriya, Masahiro

    1994-01-01

    Methods for dismantling nuclear reactor facilities must meet particularly exacting requirements imposed by heavily reinforced and radioactivated reactor shield walls. Conventional methods do not meet all such requirements, however. Intrigued by excellent characteristics of the laser cutting method relative to nuclear facility demolition, we carried out an experimental study to make a comprehensive evaluation of its characteristics, especially for deep cutting, with success in identifying main factors affecting the cutting depth of a laser and characterizing its cutting behavior. The study results indicate that a 50 kW class CO 2 laser has a potential to provide a practicable cutting speed and depth. (author)

  14. Studies of pulsed laser melting and rapid solidification using amorphous silicon

    International Nuclear Information System (INIS)

    Lowndes, D.H.; Wood, R.F.

    1984-06-01

    Pulsed-laser melting of ion implantation-amorphized silicon layers, and subsequent solidification were studied. Measurements of the onset of melting of amorphous silicon layers and of the duration of melting, and modified melting model calculations demonstrated that the thermal conductivity, K/sub a/, of amorphous silicon is very low (K/sub a/ approx. = 0.02 W/cm-K). K/sub a/ is also the dominant parameter determining the dynamical response of amorphous silicon to pulsed laser radiation. TEM indicates that bulk (volume) nucleation occurs directly from the highly undercooled liquid silicon that can be prepared by pulsed laser melting of amorphous silicon layers at low laser energy densities. A modified thermal melting model is presented. The model calculations demonstrate that the release of latent heat by bulk nucleation occurring during the melt-in process is essential to obtaining agreement with observed depths of melting. These calculations also show that this release of latent heat accompanying bulk nucleation can result in the existence of buried molten layers of silicon in the interior of the sample after the surface has solidified. The bulk nucleation implies that the liquid-to-amorphous phase transition (produced using picosecond or uv nanosecond laser pulses) cannot be explained using purely thermodynamic considerations

  15. Preparation and study of laser plasma diamond

    Energy Technology Data Exchange (ETDEWEB)

    Collins, C.B.; Davanloo, F.; Juengerman, E.M.; Jander, D.R.; Lee, T.J. (Center for Quantum Electronics, Univ. of Texas, Dallas (USA))

    1991-08-01

    Films of diamond-like material can be deposited with a laser plasma source of carbon ions in an ultrahigh vacuum environment without involving hydrogen in the growth mechanism. These films are distinguished by transparency at visible wavelengths which is a result of a high percentage of sp{sup 3} bonds. They resemble materials first quenched from ion beams at very slow deposition rates. In our method an Nd:YAG laser was focused on a graphite feedstock in an ultrahigh vacuum chamber at intensities in excess of 5x10{sup 11} W cm{sup -2}. A high current discharge confined to the path of the laser-ignited plasma provided further heat and aided processing of the ion flux. At a laser repetition rate of 10 Hz, a deposition rate of 0.5 {mu}m h{sup -1} over a 100 cm{sup 2} area was attainable with no measurable substrate heating. The substrates required no special preparation or seeding and materials including silicon, fused silica, glass, gold, copper, germanium, InP, ZnS, and polycarbonate and polyimide plastics were readily coated. Complex shapes could be accommodated and spheres of 440C stainless steel were covered successfully. Over 1000 samples were prepared to a variety of specifications with thicknesses reaching 5 {mu}m and hardness exceeding 37 GPa. (orig.).

  16. Development of a new method for small bowel transit study

    International Nuclear Information System (INIS)

    Hung, Guang-Uei; Tsai, Chien-Chung; Lin, Wan-Yu

    2006-01-01

    Currently, most studies combine the small bowel transit examination with gastric emptying time examination. There are significant drawbacks to this method. The radiotracer does not enter the small intestine in a bolus and the starting time for transit in the duodenum is difficult to define. This makes the result unreliable. In this study, we used a commercial enteric capsule containing radioactive charcoal to solve these problems. Activated charcoal powder was mixed with Tc-99m pertechnetate and loaded to the enteric capsule which can resist gastric acid and dissolve only in the small intestine, in-vitro stability experiment was performed by immersing these capsules in a colorless phosphate buffer of variable pH which mimicked the condition in stomach and small intestine. In addition, ten healthy Chinese volunteers were included for in-vivo experiment. Anterior and posterior views of abdomen were obtained at regular 30-minute intervals until the eighth hour after administration of the radioactive enteric capsule. Small bowel transit time was calculated. The enteric capsule remained intact for at least 480 minutes in the solution mimicking gastric content (pH=3.0) and disrupted at a mean duration of 227.2 minutes at a pH of 6.8 and at a mean duration of 212.4 minutes at a pH of 7.4 in the solution mimicking pancreaticobiliary secretions. In nine of ten volunteers, the small bowel transit time was between 30 to 270 minutes with a mean transit time of 140 min. In one volunteer, we failed to detect the exact time of small bowel transit because the capsule remained in the stomach throughout the study for up to 8 hours. We consider activated charcoal labeled with Tc-99m pertechnetate using an enteric capsule as the carrier to be a potential radioactive marker for small bowel transit study. (author)

  17. ILIAS - Ion and laser beam interaction and application studies. Progress report no. 2 of the PHELIX theory group

    Energy Technology Data Exchange (ETDEWEB)

    Mulser, P.; Schlegel, T. (eds.)

    2007-02-15

    The following topics are dealt with:QED, nuclear and high energy processes in extremely strong laser pulses, waves with constant phase velocity in relativistic plasmas, the effective critical electron density and its relativistic increase in an intense laser field, acceleration of electrons by laser pulses in vacuum, electron capture acceleration in a slit laser beam, laser acceleration of ion beams, collisionless high-power laser beam absorption, vacuum heating vs skin layer absorption of intense fs laser pulses, timescales of laser-induced phase transitions, quasi-static electron equilibria of laser-heted clusters, correlations in multi-electronic satellite spectra, radiation transport in the CAVEAT code. (HSI)

  18. ILIAS - Ion and laser beam interaction and application studies. Progress report no. 2 of the PHELIX theory group

    International Nuclear Information System (INIS)

    Mulser, P.; Schlegel, T.

    2007-02-01

    The following topics are dealt with:QED, nuclear and high energy processes in extremely strong laser pulses, waves with constant phase velocity in relativistic plasmas, the effective critical electron density and its relativistic increase in an intense laser field, acceleration of electrons by laser pulses in vacuum, electron capture acceleration in a slit laser beam, laser acceleration of ion beams, collisionless high-power laser beam absorption, vacuum heating vs skin layer absorption of intense fs laser pulses, timescales of laser-induced phase transitions, quasi-static electron equilibria of laser-heted clusters, correlations in multi-electronic satellite spectra, radiation transport in the CAVEAT code. (HSI)

  19. Biological Studies with Laser-Polarized ^129Xe

    Science.gov (United States)

    Tseng, C. H.; Oteiza, E. R.; Wong, G. A.; Walsworth, R. L.; Albert, M. S.; Nascimben, L.; Peled, S.; Sakai, K.; Jolesz, F. A.

    1996-05-01

    We have studied several biological systems using laser-polarized ^129Xe. In certain tissues magnetic resonance imaging (MRI) using inhaled laser-polarized noble gases may provide images superior to those from conventional proton MRI. High resolution laser-polarized ^3He images of air spaces in the human lung were recently obtained by the Princeton/Duke group. However, ^3He is not very soluble in tissue. Therefore, we are using laser polarized ^129Xe (tissue-soluble), with the long term goal of biomedical functional imaging. We have investigated multi-echo and multi-excitation magnetic resonance detection schemes to exploit the highly non-thermal ^129Xe magnetization produced by the laser polarization technique. We have inhalated live rats with laser-polarized ^129Xe gas and measured three distinct ^129Xe tissue resonances that last 20 to 40 sec. As a demonstration, we obtained a laser polarized ^129Xe image of the human oral cavity. Currently we are measuring the polarization lifetime of ^129Xe dissolved in human blood, the biological transporting medium. These studies and other recent developments will be reported.

  20. Forbidden atomic transitions driven by an intensity-modulated laser trap.

    Science.gov (United States)

    Moore, Kaitlin R; Anderson, Sarah E; Raithel, Georg

    2015-01-20

    Spectroscopy is an essential tool in understanding and manipulating quantum systems, such as atoms and molecules. The model describing spectroscopy includes the multipole-field interaction, which leads to established spectroscopic selection rules, and an interaction that is quadratic in the field, which is not often employed. However, spectroscopy using the quadratic (ponderomotive) interaction promises two significant advantages over spectroscopy using the multipole-field interaction: flexible transition rules and vastly improved spatial addressability of the quantum system. Here we demonstrate ponderomotive spectroscopy by using optical-lattice-trapped Rydberg atoms, pulsating the lattice light and driving a microwave atomic transition that would otherwise be forbidden by established spectroscopic selection rules. This ability to measure frequencies of previously inaccessible transitions makes possible improved determinations of atomic characteristics and constants underlying physics. The spatial resolution of ponderomotive spectroscopy is orders of magnitude better than the transition frequency would suggest, promising single-site addressability in dense particle arrays for quantum computing applications.

  1. Optical studies on individual transitions in GaN:Zn,Si/AlGaN heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Mohajerani, Matin; Behrends, Arne; Bakin, Andrey; Waag, Andreas [Institute for Semiconductor Technology, Braunschweig (Germany); Peters, Silke; Hofer, Helmut; Schmunk, Waldemar; Kueck, Stefan [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

    2012-07-01

    During the past few years many methods have been developed to generate single-photon sources including atoms, ions, molecules or impurities in semiconductors and quantum dots. In this work, we have investigated Si and Zn co-doped GaN/AlGaN heterostructures. This approach could potentially allow room temperature electrically driven single photon emission. The samples studied were fabricated by metal-organic chemical vapor deposition and were patterned by photolithography and plasma etching processes in 3D pillar structures in order to confine individual emitters. Photoluminescence (PL) images were obtained by a confocal fluorescence microscope with a spatial resolution of 0.3 {mu}m and focal resolution of 0.5 {mu}m demonstrating well separated pillars. PL spectra measured under 325 nm He-Cd laser excitation show a broad emission around 2.9 eV (blue luminescence band) which is attributed to transition between the shallow donor band and the Zn deep acceptor. In addition, time-resolved PL was utilized to study the recombination lifetime of the BL transitions by 375 nm pulsed laser excitation. The potential of the GaN:Zn system for single photon emission is discussed in detail.

  2. Nonstationary plasma-thermo-fluid dynamics and transition in processes of deep penetration laser beam-matter interaction

    Science.gov (United States)

    Golubev, Vladimir S.; Banishev, Alexander F.; Azharonok, V. V.; Zabelin, Alexandre M.

    1994-09-01

    A qualitative analysis of the role of some hydrodynamic flows and instabilities by the process of laser beam-metal sample deep penetration interaction is presented. The forces of vapor pressure, melt surface tension and thermocapillary forces can determined a number of oscillatory and nonstationary phenomena in keyhole and weld pool. Dynamics of keyhole formation in metal plates has been studied under laser beam pulse effect ((lambda) equals 1.06 micrometers ). Velocities of the keyhole bottom motion have been determined at 0.5 X 105 - 106 W/cm2 laser power densities. Oscillatory regime of plate break- down has been found out. Small-dimensional structures with d-(lambda) period was found on the frozen cavity walls, which, in our opinion, can contribute significantly to laser beam absorption. A new form of periodic structure on the frozen pattern being a helix-shaped modulation of the keyhole walls and bottom relief has been revealed. Temperature oscillations related to capillary oscillations in the melt layer were discovered in the cavity. Interaction of the CW CO2 laser beam and the matter by beam penetration into a moving metal sample has been studied. The pulsed and thermodynamic parameters of the surface plasma were investigated by optical and spectroscopic methods. The frequencies of plasma jets pulsations (in 10 - 105 Hz range) are related to possible melt surface instabilities of the keyhole.

  3. Morphology and structural studies of WO_3 films deposited on SrTiO_3 by pulsed laser deposition

    International Nuclear Information System (INIS)

    Kalhori, Hossein; Porter, Stephen B.; Esmaeily, Amir Sajjad; Coey, Michael; Ranjbar, Mehdi; Salamati, Hadi

    2016-01-01

    Highlights: • Highly oriented WO_3 stoichiometric films were determined using pulsed laser deposition method. • Effective parameters on thin films including temperature, oxygen partial pressure and laser energy fluency was studied. • A phase transition was observed in WO_3 films at 700 °C from monoclinic to tetragonal. - Abstract: WO_3 films have been grown by pulsed laser deposition on SrTiO_3 (001) substrates. The effects of substrate temperature, oxygen partial pressure and energy fluence of the laser beam on the physical properties of the films were studied. Reflection high-energy electron diffraction (RHEED) patterns during and after growth were used to determine the surface structure and morphology. The chemical composition and crystalline phases were obtained by XPS and XRD respectively. AFM results showed that the roughness and skewness of the films depend on the substrate temperature during deposition. Optimal conditions were determined for the growth of the highly oriented films.

  4. Diagnostics for studies of novel laser ion acceleration mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Senje, Lovisa; Aurand, Bastian; Wahlström, Claes-Göran [Department of Physics, Lund University, P. O. Box 118, S-221 00 Lund (Sweden); Yeung, Mark; Kuschel, Stephan; Rödel, Christian [Helmholtz-Institut Jena, D-07743 Jena (Germany); Wagner, Florian; Roth, Markus [Technische Universität Darmstadt, D-64289 Darmstadt (Germany); Li, Kun; Neumayer, Paul [ExtreMe Matter Institut, D-64291 Darmstadt (Germany); Dromey, Brendan; Jung, Daniel [Department of Physics and Astronomy, Queen' s University, Belfast BT7 1NN (United Kingdom); Bagnoud, Vincent [Helmholtz-Institut Jena, D-07743 Jena (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Zepf, Matthew [Helmholtz-Institut Jena, D-07743 Jena (Germany); Department of Physics and Astronomy, Queen' s University, Belfast BT7 1NN (United Kingdom); Kuehl, Thomas [ExtreMe Matter Institut, D-64291 Darmstadt (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Universität Mainz, D-55099 Mainz (Germany)

    2014-11-15

    Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.

  5. Diagnostics for studies of novel laser ion acceleration mechanisms

    International Nuclear Information System (INIS)

    Senje, Lovisa; Aurand, Bastian; Wahlström, Claes-Göran; Yeung, Mark; Kuschel, Stephan; Rödel, Christian; Wagner, Florian; Roth, Markus; Li, Kun; Neumayer, Paul; Dromey, Brendan; Jung, Daniel; Bagnoud, Vincent; Zepf, Matthew; Kuehl, Thomas

    2014-01-01

    Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution

  6. LPI studies with grazing incidence irradiation at the Nike laser

    Science.gov (United States)

    Weaver, J.; Kehne, D.; Schmitt, A.; Obenschain, S.; Serlin, V.; Oh, J.; Lehmberg, R.; Seely, J.

    2013-10-01

    Studies of laser plasma instabilities (LPI) at the Nike laser facility at NRL have previously concentrated on planar targets irradiated with their surface normal aligned to the central axis of the laser. Shots with planar targets rotated up 60° to the laser have shown changes in thresholds for the two-plasmon decay instability and stimulated Raman scattering near the quarter critical region. In the case of rotated low-Z targets, spectra were observed to shift to lower wavelength and were substantially stronger in the visible and ultraviolet spectral ranges. The low-Z target data show growth at an incident intensity slightly below (~30%) the threshold values observed at normal incidence. A rapid rise in signal level over the same laser intensities was also observed in the hard x-ray data which serve as an overall indicator of LPI activity. Shots with rotated planar high-Z targets showed that the visible and ultraviolet emissions dropped significantly when compared to low-Z targets in the same geometry. This presentation will include results from upcoming experiments to determine the LPI signal for low-Z, high-Z, and high-Z coated targets at lower laser intensities for several angles of target rotation. Shots with widely separated laser beams are also planned to explore cross beam energy transport at Nike. Work supported by DoE/NNSA.

  7. Conceptual design study for a laser fusion hybrid

    International Nuclear Information System (INIS)

    Maniscalco, J.A.

    1976-01-01

    Lawrence Livermore Laboratory and Bechtel Corporation have been involved in a joint effort to conceptually design a laser fusion hybrid reactor. The design which has evolved is a depleted-uranium fueled fast-fission blanket which produces fissile plutonium and electricity. A major objective of the design study was to evaluate the feasibility of producing fissile fuel with laser fusion. This feasibility evaluation was carried out by analyzing the integrated engineering performance of the complete conceptual design and by identifying the required laser/pellet performance. The performance of the laser fusion hybrid has also been compared to a typical fast breeder reactor. The results show that the laser fusion hybrid produces enough fissile material to fuel more than six light water reactors (LWRs) of equivalent thermal power while operating in a regime which requires an order of magnitude less laser and pellet performance than pure laser fusion. In comparison to a fast breeder reactor the hybrid produces 10 times more fissile fuel. An economic analysis of the design shows that the cost of electricity in a combined hybrid-LWR scenario increases by only 20 to 40 percent when the capital cost of the hybrid ranges from 2 to 3 times more than an LWR

  8. Conceptual design study for a laser fusion hybrid

    International Nuclear Information System (INIS)

    Maniscalco, J.A.

    1976-09-01

    Lawrence Livermore Laboratory and Bechtel Corporation have been involved in a joint effort to conceptually design a laser fusion hybrid reactor. The design which has evolved is a depleted-uranium fueled fast-fission blanket which produces fissile plutonium and electricity. A major objective of the design study was to evaluate the feasibility of producing fissile fuel with laser fusion. This feasibility evaluation was carried out by analyzing the integrated engineering performance of the complete conceptual design and by identifying the required laser/pellet performance. The performance of the laser fusion hybrid has also been compared to a typical fast breeder reactor. The results show that the laser fusion hybrid produces enough fissile material to fuel more than six light water reactors (LWR's) of equivalent thermal power while operating in a regime which requires an order of magnitude less laser and pellet performance than pure laser fusion. In comparison to a fast breeder reactor the hybrid produces 10 times more fissile fuel. An economic analysis of the design shows that the cost of electricity in a combined hybrid-LWR scenario is insensitive to the capital cost of the hybrid, increasing by only 20 to 40 percent when the capital cost of the hybrid ranges from 2 to 3 times more than an LWR

  9. Characterization of a Laser-Generated Perturbation in High-Speed Flow for Receptivity Studies

    Science.gov (United States)

    Chou, Amanda; Schneider, Steven P.; Kegerise, Michael A.

    2014-01-01

    A better understanding of receptivity can contribute to the development of an amplitude-based method of transition prediction. This type of prediction model would incorporate more physics than the semi-empirical methods, which are widely used. The experimental study of receptivity requires a characterization of the external disturbances and a study of their effect on the boundary layer instabilities. Characterization measurements for a laser-generated perturbation were made in two different wind tunnels. These measurements were made with hot-wire probes, optical techniques, and pressure transducer probes. Existing methods all have their limitations, so better measurements will require the development of new instrumentation. Nevertheless, the freestream laser-generated perturbation has been shown to be about 6 mm in diameter at a static density of about 0.045 kg/cubic m. The amplitude of the perturbation is large, which may be unsuitable for the study of linear growth.

  10. Ultrafast studies of shock-induced melting and phase transitions at LCLS

    Science.gov (United States)

    McMahon, Malcolm

    The study of shock-induced phase transitions, which is vital to the understanding of material response to rapid pressure changes, dates back to the 1950s, when Bankcroft et al reported a transition in iron. Since then, many transitions have been reported in a wide range of materials, but, due to the lack of sufficiently bright x-ray sources, the structural details of these new phases has been notably lacking. While the development of nanosecond in situ x-ray diffraction has meant that lattice-level studies of such phenomena have become possible, including studies of the phase transition reported 60 years ago in iron, the quality of the diffraction data from such studies is noticeably poorer than that obtained from statically-compressed samples on synchrotrons. The advent of x-ray free electron lasers (XFELs), such as the LCLS, has resulted in an unprecedented improvement in the quality of diffraction data that can be obtained from shock-compressed matter. Here I describe the results from three recent experiment at the LCLS that looked at the solid-solid and solid-liquid phase transitions in Sb, Bi and Sc using single 50 fs x-ray exposures. The results provide new insight into the structural changes and melting induced by shock compression. This work is supported by EPSRC under Grant No. EP/J017051/1. Use of the LCLS, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.

  11. Studies of intense-laser plasma instabilities

    Czech Academy of Sciences Publication Activity Database

    Láska, Leoš; Krása, Josef; Badziak, J.; Jungwirth, Karel; Krouský, Eduard; Margarone, Daniele; Parys, P.

    2013-01-01

    Roč. 272, May (2013), 94-98 ISSN 0169-4332 R&D Projects: GA MŠk(CZ) 7E09092; GA MŠk(CZ) LC528; GA AV ČR IAA100100715 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser plasma instabilities * self-generated magnetic field * longitudinal structure of the expanding plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.538, year: 2013

  12. A Longitudinal Study of Adolescent Adjustment Following Family Transitions

    Science.gov (United States)

    Ruschena, Eda; Prior, Margot; Sanson, Ann; Smart, Diana

    2005-01-01

    Background: This study examined the impact of family transitions, that is, parental separation, divorce, remarriage and death, upon the lives of Australian children and adolescents in a longitudinal study of temperament and development. Methods: Using longitudinal and concurrent questionnaire data, outcomes for young people experiencing…

  13. Transition to Postgraduate Study: Postgraduate Ecological Systems and Identity

    Science.gov (United States)

    Tobbell, Jane; O'Donnell, Victoria L.

    2013-01-01

    This paper explores and examines the distal and proximal systems which construct social science postgraduate study in the UK and analyses the emergent identities of postgraduate students as they negotiate the multiple and interacting practices in their transition to study. The data represent part of a one-year research project, funded by the…

  14. Interferometric studies of laser-created plasmas using compact soft x-ray lasers

    International Nuclear Information System (INIS)

    Dunn, J; Nilsen, J; Moon, S; Keenan, R; Jankowska, E; Maconi, M C; Hammarsten, E C; Filevich, J; Hunter, J R; Smith, R F; Shlyaptsev, V; Rocca, J J

    2003-01-01

    We summarize results of several successful dense plasma diagnostics experiments realized by combining two different kinds of table-top soft x-ray lasers with an amplitude division interferometer based on diffraction grating beam splitters. In the first set of experiments this robust high throughput diffraction grating interferometer (DGI) was used with a 46.9 nm portable capillary discharge laser to study the dynamics of line focus and point focus laser-created plasmas. The measured electron density profiles, which differ significantly from those expected from a classical expansion, unveil important two-dimensional effects of the dynamics of these plasmas. A second DGI customized to operate in combination with a 14.7 nm Ni-like Pd transient gain laser was used to perform interferometry of line focus laser-created plasmas with picosecond time resolution. These measurements provide valuable new benchmarks for complex hydrodynamic codes and help bring new understanding of the dynamics of dense plasmas. The instrumentation and methodology we describe is scalable to significantly shorter wavelengths, and constitutes a promising scheme for extending interferometry to the study of very dense plasmas such as those investigated for inertial confinement fusion

  15. Lasers

    CERN Document Server

    Milonni, Peter W

    1988-01-01

    A comprehensive introduction to the operating principles and applications of lasers. Explains basic principles, including the necessary elements of classical and quantum physics. Provides concise discussions of various laser types including gas, solid state, semiconductor, and free electron lasers, as well as of laser resonators, diffraction, optical coherence, and many applications including holography, phase conjugation, wave mixing, and nonlinear optics. Incorporates many intuitive explanations and practical examples. Discussions are self-contained in a consistent notation and in a style that should appeal to physicists, chemists, optical scientists and engineers.

  16. Dielectric constant of GaAs during a subpicosecond laser-induced phase transition

    Science.gov (United States)

    Siegal, Y.; Glezer, E. N.; Mazur, E.

    1994-06-01

    We measured the time evolution of the real and imaginary parts of the dielectric constant of GaAs following femtosecond laser pulse excitation. The data show a collapse of the average optical gap, or average bonding-antibonding energy-level separation. The rate of collapse increases with pump fluence. The decrease in the gap indicates that the pump beam induces a structural transformation from a covalent, tetrahedrally coordinated crystal to a phase with metallic cohesive properties.

  17. Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

    Science.gov (United States)

    Li, Gan; Cheng, Mousen; Li, Xiaokang

    2016-09-01

    Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM.

  18. Laser damage studies on MgF2 thin films

    International Nuclear Information System (INIS)

    Protopapa, Maria Lucia; De Tomasi, Ferdinando; Perrone, Maria Rita; Piegari, Angela; Masetti, Enrico; Ristau, Detlev; Quesnel, Etienne; Duparre, Angela

    2001-01-01

    The results of laser damage studies performed at 248 nm (KrF excimer laser) on MgF 2 thin films deposited by different techniques (electron-beam evaporation, thermal boat evaporation, and ion-beam sputtering) on fused silica and CaF 2 substrates are presented. We find that the films deposited on CaF 2 substrates by the electron-beam evaporation technique present the highest damage threshold fluence (9 J/cm2). The photoacoustic (PA) beam deflection technique was employed, in addition to microscopical inspection, to determine laser damage fluences. We confirm, by scanning electron microscopy analysis of the damaged spots, the capability of the PA technique to provide information on the mechanisms leading to damage. The dependence of both laser damage fluence and damage morphology on the film deposition technique, as well as on the film substrate, is discussed

  19. Study on laser welding of austenitic stainless steel by varying incident angle of pulsed laser beam

    Science.gov (United States)

    Kumar, Nikhil; Mukherjee, Manidipto; Bandyopadhyay, Asish

    2017-09-01

    In the present work, AISI 304 stainless steel sheets are laser welded in butt joint configuration using a robotic control 600 W pulsed Nd:YAG laser system. The objective of the work is of twofold. Firstly, the study aims to find out the effect of incident angle on the weld pool geometry, microstructure and tensile property of the welded joints. Secondly, a set of experiments are conducted, according to response surface design, to investigate the effects of process parameters, namely, incident angle of laser beam, laser power and welding speed, on ultimate tensile strength by developing a second order polynomial equation. Study with three different incident angle of laser beam 89.7 deg, 85.5 deg and 83 deg has been presented in this work. It is observed that the weld pool geometry has been significantly altered with the deviation in incident angle. The weld pool shape at the top surface has been altered from semispherical or nearly spherical shape to tear drop shape with decrease in incident angle. Simultaneously, planer, fine columnar dendritic and coarse columnar dendritic structures have been observed at 89.7 deg, 85.5 deg and 83 deg incident angle respectively. Weld metals with 85.5 deg incident angle has higher fraction of carbide and δ-ferrite precipitation in the austenitic matrix compared to other weld conditions. Hence, weld metal of 85.5 deg incident angle achieved higher micro-hardness of ∼280 HV and tensile strength of 579.26 MPa followed by 89.7 deg and 83 deg incident angle welds. Furthermore, the predicted maximum value of ultimate tensile strength of 580.50 MPa has been achieved for 85.95 deg incident angle using the developed equation where other two optimum parameter settings have been obtained as laser power of 455.52 W and welding speed of 4.95 mm/s. This observation has been satisfactorily validated by three confirmatory tests.

  20. Pyrolysis in Groningen, Netherlands. Feasibility study on a transition coalition

    International Nuclear Information System (INIS)

    Siemons, R.V.

    2005-01-01

    Results of a study on the technical, economical and financial feasibility of a pyrolysis factory for the processing and energetic application of biomass wastes in the Dutch province Groningen are presented and discussed. Also, attention is paid to the implementation of the planned pyrolysis factory in one or more transition programmes. [nl

  1. Application of Kissinger analysis to glass transition and study of ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 35; Issue 4. Application of Kissinger analysis to glass transition and study of thermal degradation kinetics of phenolic–acrylic IPNs ... Author Affiliations. S Goswami1 K Kiran1. Department of Polymer Engineering, Birla Institute of Technology, Ranchi 835 215, India ...

  2. Veterans' Transitions to Community College: A Case Study

    Science.gov (United States)

    Wheeler, Holly A.

    2012-01-01

    Veterans on college campuses are not new; however, the recent influx of veterans returning home from war-time service present challenges to the colleges they attend. The purpose of this qualitative case study was to examine the transition process experienced by veterans leaving military service and attending community college for the first time.…

  3. Secondary Analysis of National Longitudinal Transition Study 2 Data

    Science.gov (United States)

    Hicks, Tyler A.; Knollman, Greg A.

    2015-01-01

    This review examines published secondary analyses of National Longitudinal Transition Study 2 (NLTS2) data, with a primary focus upon statistical objectives, paradigms, inferences, and methods. Its primary purpose was to determine which statistical techniques have been common in secondary analyses of NLTS2 data. The review begins with an…

  4. Laser induced fluorescence of TiD: analysis of the B4Γ-X4Φ transition

    International Nuclear Information System (INIS)

    Danielsson, M

    2007-01-01

    A titanium hollow cathode lamp in combination with a dye laser and a monochromator has been used to resolve the laser-induced fluorescence of the TiD molecule. This has enabled the extension of the earlier rotational analysis of the (0,0) band of the B 4 Γ-X 4 Φ transition. In addition, the (1,1) band and part of the (2,2) band have been observed and analyzed. All earlier works on the TiD and TiH molecules concern the (0,0) band. The present work is the first to report experimentally determined equilibrium constants for TiD. For the ground state X 4 Φ the principal parameters are (in cm -1 ) A e =33.075, B e =2.7804, D e =6.819x10 -5 and α e =0.0466. By using the isotope relationships the corresponding equilibrium parameters for the TiH molecule are given

  5. Measurement of the spectral shift of the 3d→4p transitions in Ar+, Cl+ and S+ by means of collinear fast-beam laser spectroscopy

    International Nuclear Information System (INIS)

    Eichhorn, A.

    1981-01-01

    The spectral shift of the 3d→4p transitions in Ar + ( 36 Ar + and 40 Ar + ) Cl + ( 35 Cl + and 37 Cl + ) and S + ( 32 S + + 34 S + ) were measured by means of collinear fast-beam laser spectroscopy. Since the volume effect is neglectible only the normal and specific mass effect give contributions to the spectral shift. (BEF)

  6. Hyperfine structure and isotope shift of transitions in YbI using UV and deep-UV cw laser light and the angular distribution of fluorescence radiation

    NARCIS (Netherlands)

    Zinkstok, R.T.; van Duijn, E.J.; Witte, S.; Hogervorst, W.

    2002-01-01

    Using the third harmonic of a cw titanium:sapphire laser, the hyperfine structure (HFS) and isotope shift (IS) of three deep-UV transitions of neutral Yb have been measured for the first time. By exploiting the angular distribution of fluorescence radiation, accurate and complete results are

  7. SOLASE conceptual laser fusion reactor study

    International Nuclear Information System (INIS)

    Moses, G.A.; Conn, R.W.; Abdel-Khalik, S.I.; Cooper, G.W.; Howard, J.; Magelssen, G.R.

    1978-01-01

    A conceptual laser fusion reactor for electric power, SOLASE, has been designed. The SOLASE design utilizes a 1 MJ, 6.7% efficient laser to implode 20 fusion targets per second. The target gain is 150 and produces a net electrical power of 1000 MW. The reactor cavity is spherical with a 6 m radius. The first wall is graphite and has a neutron wall loading of 5 MW/m 2 . It is protected from the target debris by low pressure xenon gas that is introduced into the cavity. The blanket structure is a honeycombed graphite composite. The tritium breeding and heat transport medium is Li 2 O in the form of pellets that flow through the blanket. The tritium breeding ration is 1.34. Temperature decoupling of the graphite structure and the Li 2 O coolant enables the structure to operate at temperatures that minimize radiation damage effects. The graphite blanket is replaced every year but exhibits low levels of radioactivity so that limited hands on maintenance is possible two weeks after shutdown, thus facilitating rapid replacement

  8. Shock-Assisted Superficial Hexagonal-to-Cubic Phase Transition in GaN/Sapphire Interface Induced by Using Ultra-violet Laser Lift-Of Techniques

    International Nuclear Information System (INIS)

    Wei-Hua, Chen; Xiao-Dong, Hu; Xiang-Ning, Kang; Xu-Rong, Zhou; Xiao-Min, Zhang; Tong-Jun, Yu; Zhi-Jian, Yang; Ke, Xu; Guo-Yi, Zhang; Xu-Dong, Shan; Li-Ping, You

    2009-01-01

    Ultra-violet (KrF excimer laser, λ = 248 nm) laser lift-of (LLO) techniques have been operated to the GaN/sapphire structure to separate GaN from the sapphire substrate. Hexagonal to cubic phase transformation induced by the ultra-violet laser lift-of (UV-LLO) has been characterized by micro-Raman spectroscopy, micro-photoluminescence, along with high-resolution transmission electron microscopy (HRTEM). HRTEM indicates that UV-LLO induced phase transition takes place above the LLO interface, without phase transition under the LLO interface. The formed cubic GaN often exists as nanocrystal grains attaching on the bulk hexagonal GaN. The half-loop-cluster-like UV-LLO interface indicates that the LLO-induced shock waves has generated and played an assistant role in the decomposition of the hexagonal GaN and in the formation of cubic GaN grains at the LLO surface

  9. Studies of bandwidth dependence of laser plasma instabilities driven by the Nike laser

    Science.gov (United States)

    Weaver, J.; Kehne, D.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Oh, J.; Lehmberg, R. H.; Brown, C. M.; Seely, J.; Feldman, U.

    2012-10-01

    Experiments at the Nike laser facility of the Naval Research Laboratory are exploring the influence of laser bandwidth on laser plasma instabilities (LPI) driven by a deep ultraviolet pump (248 nm) that incorporates beam smoothing by induced spatial incoherence (ISI). In early ISI studies with longer wavelength Nd:glass lasers (1054 nm and 527 nm),footnotetextObenschain, PRL 62(1989);Mostovych, PRL 62(1987);Peyser, Phys. Fluids B 3(1991). stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (δν/ν˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). The current studies will compare the emission signatures of LPI from planar CH targets during Nike operation at large bandwidth (δν˜1THz) to observations for narrower bandwidth operation (δν˜0.1-0.3THz). These studies will help clarify the relative importance of the short wavelength and wide bandwidth to the increased LPI intensity thresholds observed at Nike. New pulse shapes are being used to generate plasmas with larger electron density scale-lengths that are closer to conditions during pellet implosions for direct drive inertial confinement fusion.

  10. Low intensity 635 nm diode laser irradiation inhibits fibroblast-myofibroblast transition reducing TRPC1 channel expression/activity: New perspectives for tissue fibrosis treatment.

    Science.gov (United States)

    Sassoli, Chiara; Chellini, Flaminia; Squecco, Roberta; Tani, Alessia; Idrizaj, Eglantina; Nosi, Daniele; Giannelli, Marco; Zecchi-Orlandini, Sandra

    2016-03-01

    Low-level laser therapy (LLLT) or photobiomodulation therapy is emerging as a promising new therapeutic option for fibrosis in different damaged and/or diseased organs. However, the anti-fibrotic potential of this treatment needs to be elucidated and the cellular and molecular targets of the laser clarified. Here, we investigated the effects of a low intensity 635 ± 5 nm diode laser irradiation on fibroblast-myofibroblast transition, a key event in the onset of fibrosis, and elucidated some of the underlying molecular mechanisms. NIH/3T3 fibroblasts were cultured in a low serum medium in the presence of transforming growth factor (TGF)-β1 and irradiated with a 635 ± 5 nm diode laser (continuous wave, 89 mW, 0.3 J/cm(2) ). Fibroblast-myofibroblast differentiation was assayed by morphological, biochemical, and electrophysiological approaches. Expression of matrix metalloproteinase (MMP)-2 and MMP-9 and of Tissue inhibitor of MMPs, namely TIMP-1 and TIMP-2, after laser exposure was also evaluated by confocal immunofluorescence analyses. Moreover, the effect of the diode laser on transient receptor potential canonical channel (TRPC) 1/stretch-activated channel (SAC) expression and activity and on TGF-β1/Smad3 signaling was investigated. Diode laser treatment inhibited TGF-β1-induced fibroblast-myofibroblast transition as judged by reduction of stress fibers formation, α-smooth muscle actin (sma) and type-1 collagen expression and by changes in electrophysiological properties such as resting membrane potential, cell capacitance and inwardly rectifying K(+) currents. In addition, the irradiation up-regulated the expression of MMP-2 and MMP-9 and downregulated that of TIMP-1 and TIMP-2 in TGF-β1-treated cells. This laser effect was shown to involve TRPC1/SAC channel functionality. Finally, diode laser stimulation and TRPC1 functionality negatively affected fibroblast-myofibroblast transition by interfering with TGF-β1 signaling, namely reducing the

  11. Higher-order interactions in molecular collisions studied by a novel laser spectroscopic method

    International Nuclear Information System (INIS)

    Kajita, M.; Tachikawa, M.; Shimizu, T.

    1986-01-01

    This is the first systematic experiment to study the characteristics of the dipole-quadrupole and dipole-induced dipole interactions as well as the dipole-dipole interaction. The authors developed a new method to measure the relaxation rate constant of a weak IR transition. The absorption cell is introduced inside the CO/sub 2/ laser cavity to improve sensitivity. The transient oscillation superimposed on the cw laser output is observed when the Stark pulse is applied to the absorbing molecules. The absorption increases when the better coincidence between the laser and absorption lines is obtained by application of the Stark voltage. The absorption decreases for a larger Stark voltage. The sign of the signal depends on whether the absorption intensity increases or decreases due to the Stark field. Since pressure broadening modifies the absorption line shape, the sign of the signal changes when the pressure is increased. The relaxation rate constant can be determined by observing the sign of the signal. The experiment is performed with the frequency coincidence between the CH/sub 3/CN ν/sub 7//sup r/ R(6.6) line and the CO/sub 2/ laser 9.4-μm R(22) line. The relaxation rate constants against various foreign gas molecules (polar molecules, nonpolar linear molecules, and spherical atoms and molecules) have been determined

  12. Study of X-ray spectrum of laser-produced gold plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Busquet, M. (CEA Centre d' Etudes de Limeil, 94 - Villeneuve-Saint-Georges (France)); Pain, D.; Bauche, J.; Luc-Koenig, E. (Centre National de la Recherche Scientifique, 91 - Orsay (France). Lab. Aime Cotton)

    1985-02-01

    Aiming at the spectroscopic diagnostic of gold plasmas, we have studied the wavelengths and intensities of X-ray spectral lines emitted in the range 4.4 to 6.2 angstroms by a target made of gold alloyed to a few percent of aluminium irradiated by a laser pulse. Aluminium yields the wavelength calibration and a monitoring of the temperature and the density of the plasma. The main features of the gold spectrum in this spectral range are due to the 3d-4f, 3p-4s and 3d-4p transitions of gold in the Co I through Cu I isoelectronic sequences.

  13. Study of X-ray spectrum of laser-produced gold plasmas

    International Nuclear Information System (INIS)

    Busquet, M.; Pain, D.; Bauche, J.; Luc-Koenig, E.

    1985-01-01

    Aiming at the spectroscopic diagnostic of gold plasmas, we have studied the wavelengths and intensities of X-ray spectral lines emitted in the range 4.4 to 6.2 angstroms by a target made of gold alloyed to a few percent of aluminium irradiated by a laser pulse. Aluminium yields the wavelength calibration and a monitoring of the temperature and the density of the plasma. The main features of the gold spectrum in this spectral range are due to the 3d-4f, 3p-4s and 3d-4p transitions of gold in the Co I through Cu I isoelectronic sequences. (orig.)

  14. Study of the mechanisms of matrix assisted laser desorption / ionization

    International Nuclear Information System (INIS)

    Manuelli, Pascal

    1995-01-01

    This research thesis aims at a better knowledge of some aspects of a complex mechanism: the matrix-assisted laser desorption/ionization (MALDI). The author first proposes a comparative analysis of results obtained by time-of-flight (TOF) mass spectrometry and by Fourier transform mass spectrometry. He reports the study of the matrix role (notably a polymeric matrix) as a matter submitted to laser desorption. In this respect, the influence of the incident wavelength has been studied. The author also reports a comparative of ions produced by matrix laser desorption (study performed by Fourier transform mass spectrometry) and of neutral molecules (study performed by flash pyrolysis coupled with gas chromatography and with mass spectrometry). Finally, results obtained on derivatives and complexes based on beta-cyclodextrins highlight benefits as well as limitations of this technique [fr

  15. Coupled two-quantum-transition probability for laser photons and microwave plasmons

    International Nuclear Information System (INIS)

    Hildebrandt, J.

    1985-01-01

    The introduction of a plasmon-state vector analogous to a photon-field oscillator allows within the rotating-wave approximation, transformation to a time-independent interaction Hamiltonian, so that Fermi's golden rule can be applied to the two-quantum transition. Although the existence of a vector potential is necessary for the oscillator state vectors, only the multipolar Hamiltonian need be used for the off-resonant frequencies

  16. He-Ne laser effects on blood microcirculation. An in vivo study through laser doppler flowmetry

    International Nuclear Information System (INIS)

    Nunez, Silvia Cristina

    2002-01-01

    Blood microcirculation performs an important function in tissue repair process, as well as in pain control, allowing for greater oxygenation of the tissues and the accelerated expulsion of metabolic products, that may be contributing to pain. Low Intensity Laser Therapy (LILT) is widely used to promote healing, and there is an assumption that it is mechanism of action may be due to an enhancement of blood supply. The purpose of this study was to evaluate, using laser Doppler flowmetry (LDF), the stated effects caused by radiation emitted by a He-Ne laser (λ=632.8 nm) on blood microcirculation during tissue repair. To this end, 15 male mice were selected and received a liquid nitrogen provoked lesion, above the dorsal region, and blood flow was measured periodically, during 21 days. Due to radiation emission by the LDF equipment, a control group was established to evaluate possible effects caused by this radiation on microcirculation. To evaluate the He-Ne laser effects, a 1.15 J/cm 2 dose was utilized, with an intensity of 6 mW/cm 2 . The results obtained demonstrate flow alterations, provoked by the lesion, and subsequent inflammatory response. There was no statistical difference between the studied groups. As per the analysis of the results there is no immediate effect due the radiation emitted by a He Ne laser on microcirculation, although a percentage increase was observed in day 7 on medium blood flow rate in irradiated specimens. New studies are necessary to validate the use of this wavelength, in order to promote beneficial alterations in blood supply in radiated areas. (author)

  17. A new method to induce transitions in muonic atoms using a high-power tunable dye laser coupled to a stopping muon beam

    CERN Document Server

    Bertin, A; Duclos, J; Gastaldi, Ugo; Gorini, G; Neri, G; Picard, J; Pitzurra, O; Placci, A; Polacco, E; Stefanini, G; Torelli, G; Vitale, A; Zavattini, E

    1974-01-01

    An apparatus is described in which a ruby-pumped dye laser is used to induce transitions from the 2S to the 2P levels of the muonic ion ( mu He)/sup +/. The dye laser supplies infra-red radiation pulses in the wavelengths (8040-8180) AA, at typical repetition rates of 1 pulse every 4 s, with an energy release per pulse of 300 mJ for 1.2 J pumping energy. A special synchronization procedure is followed to trigger the laser in close coupling with the incoming muon beam which is stopped in a helium target at pressures between 40 and 50 atm. The other performances of the device are fully discussed with reference both to the laser facility and to the special high-pressure helium target. (23 refs).

  18. Assessment of colonic transit time using MRI: a feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Buhmann, Sonja; Reiser, Maximilian F.; Lienemann, Andreas [Ludwig-Maximilians-University, Department of Clinical Radiology, Campus Grosshadern, Munich (Germany); Kirchhoff, Chlodwig; Ladurner, Roland; Mussack, Thomas [Ludwig-Maximilians-University, Department of Surgery and Traumatology, Campus Innenstadt, Munich (Germany)

    2007-03-15

    The aim of this pilot study was to evaluate a new, non-invasive examination method using MRI for the quantification of the colonic transit time after oral administration of gadolinium-saline solution filled capsules. Healthy volunteers without previous or acute symptoms of gastrointestinal disorders were enrolled. After a 3-day diet for the standardization of gastrocolonic content the volunteers swallowed five Gd-DTPA/saline 0.9%-filledcapsules. Seven different concentrations of Gd-DTPA/saline 0.9% solution between 1:0 and 0:1 were tested in a dilution series. Following ingestion of capsules, coronal Flash T1 and True Fisp sequences using a 1.5 Tesla system were obtained at 0 h, 3 h, 6 h, 12 h, 24 h, 36 h and 60 h. Sequences were analyzed by two independent experts for locating the capsules. Overall colonic transit time was separately analyzed for both genders. Fifteen healthy volunteers (7 females, 8 males; mean age 34{+-}13 years) were enrolled. The phantom study provided the best contrast in both the T1-and T2-weighted sequences defining a ratio of 1:10 for Gd-DTPA/saline 0.9% solution. The mean transit time accounted for 41{+-}9 h in women and for 31{+-}10 h in men. MRI is an adequate method for the assessment of colonic transit time offering the advantages of no exposure to radiation, short examination time, possible dynamic evaluation of the transit and the practicability in terms of a future adoption to clinical routine. (orig.)

  19. Assessment of colonic transit time using MRI: a feasibility study

    International Nuclear Information System (INIS)

    Buhmann, Sonja; Reiser, Maximilian F.; Lienemann, Andreas; Kirchhoff, Chlodwig; Ladurner, Roland; Mussack, Thomas

    2007-01-01

    The aim of this pilot study was to evaluate a new, non-invasive examination method using MRI for the quantification of the colonic transit time after oral administration of gadolinium-saline solution filled capsules. Healthy volunteers without previous or acute symptoms of gastrointestinal disorders were enrolled. After a 3-day diet for the standardization of gastrocolonic content the volunteers swallowed five Gd-DTPA/saline 0.9%-filledcapsules. Seven different concentrations of Gd-DTPA/saline 0.9% solution between 1:0 and 0:1 were tested in a dilution series. Following ingestion of capsules, coronal Flash T1 and True Fisp sequences using a 1.5 Tesla system were obtained at 0 h, 3 h, 6 h, 12 h, 24 h, 36 h and 60 h. Sequences were analyzed by two independent experts for locating the capsules. Overall colonic transit time was separately analyzed for both genders. Fifteen healthy volunteers (7 females, 8 males; mean age 34±13 years) were enrolled. The phantom study provided the best contrast in both the T1-and T2-weighted sequences defining a ratio of 1:10 for Gd-DTPA/saline 0.9% solution. The mean transit time accounted for 41±9 h in women and for 31±10 h in men. MRI is an adequate method for the assessment of colonic transit time offering the advantages of no exposure to radiation, short examination time, possible dynamic evaluation of the transit and the practicability in terms of a future adoption to clinical routine. (orig.)

  20. Preliminary cutting and drilling studies using new generation lasers

    International Nuclear Information System (INIS)

    Kautz, D.D.; Sze, J.S.; Dragon, E.P.; Hargrove, R.S.

    1992-01-01

    High power and radiance dye lasers developed at Lawrence Livermore National Laboratory show promise for material processing tanks. Evaluation using welding heat flow models suggest significant increases in precision and speed are expected. We developed tooling and instrumentation to diagnose important parameters including spot geometry and optical train quality. We started processing studies to determine the viability of these lasers of cutting and drilling. We used titanium alloys first in the studies due to the availability of comparable parametric studies in the technical literature. Results show that cuts and holes with extremely fine features can be made with dye lasers. The high radiance beam produces low distortion and small heat-affected zones. We have accomplished very high aspect ratios and micron scale kerfs and holes. Through continued system improvement and process optimization, we believe that submicron levels will be achieved

  1. Prospective study on laser-assisted laparascopic partial nephrectomy

    Science.gov (United States)

    Sroka, Ronald; Hennig, Georg; Zilinberg, Katja; Khoder, Wael Y.

    2012-02-01

    rinsing. Conclusion: This prospective in-vivo feasibility study shows that laser assisted partial nephrectomy seems to be a safe and promising medical technique which could be provided either during open surgery as well as laparascopically. This application showed good haemostasis and minimal parenchymal damage. Further investigations and development are needed for on-line detection of the remain coagulation margin. An optimised treatment equipment will support the applicability of laser assisted laparoscopic partial nephrectomy.

  2. Studies on mechanisms of the laser particle acceleration; Untersuchungen zu Mechanismen der Laser-Teilchenbeschleunigung

    Energy Technology Data Exchange (ETDEWEB)

    Aurand, Bastian

    2012-06-20

    Within the last decade, many developments towards higher energies and particle numbers paved the way of particle acceleration performed by high intensity laser systems. Up to now, the process of a field-induced acceleration process (Target-Normal-Sheath-Acceleration (TNSA)) is investigated the most. Acceleration occurs as a consequence of separation of charges on a surface potential. Here, the broad energy spectrum is a problem not yet overcome although many improvements were achieved. Calculations for intensities higher than 10{sup 20..21} W/cm{sup 2} give hint that Radiation-Pressure-Acceleration (RPA) may lead to a sharper, monoenergetic energy spectrum. Within the framework of this thesis, the investigation of the acceleration mechanism is studied experimentally in the intensity range of 10{sup 19} W/cm{sup 2}. Suitable targets were developed and applied for patent. A broad range of parameters was scanned by means of high repetition rates together with an adequate laser system to provide high statistics of several thousands of shots, and the dependence of target material, intensity, laser polarisation and pre plasma-conditions was verified. Comparisons with 2-d numeric simulations lead to a model of the acceleration process which was analyzed by several diagnostic methods, giving clear evidence for a new, not field-induced acceleration process. In addition, a system for a continuous variation of the polarization based on reflective optics was developed in order to overcome the disadvantages of retardation plates, and their practicability of high laser energies can be achieved.

  3. Feasibility Study of Laser Cutting for Fabrication of Tensile Specimen

    International Nuclear Information System (INIS)

    Jin, Y. G.; Baik, S. J.; Kim, G. S.; Heo, G. S.; Yoo, B. O.; Ahn, S. B.; Chun, Y. B.

    2015-01-01

    The specimen fabrication technique was established to machine the specimen from the irradiated materials. The wire cut EDM(electric discharge machine) was modified to fabricate the mechanical testing specimens from irradiated components and fuel claddings. The oxide layer removal system was also developed because the oxide layer on the surface of the irradiated components and claddings interrupted the applying the electric current during the processing. However, zirconium oxide is protective against further corrosion as well as beneficial to mechanical strength for the tensile deformation of the cladding. Thus, it is important to fabricate the irradiated specimens without removal of oxide layer on the surface of the irradiated structural components and claddings. In the present study, laser cutting system was introduced to fabricate the various mechanical testing specimens from the unirradiated fuel cladding and the feasibility of the laser cutting system was studied for the fabrication of various types of irradiated specimens in a hot cell at IMEF (Irradiated Materials Examination Facility) of KAERI. Laser beam machining system was introduced to fabricate the various mechanical testing specimens from the unirradiated fuel cladding and the dimensions were compared for the feasibility of the laser cutting system. The effect of surface oxide layer was also investigated for machining process of the zircaloy-4 fuel cladding and it was found that laser beam machining could be a useful tool to fabricate the specimens with surface oxide layer

  4. Feasibility Study of Laser Cutting for Fabrication of Tensile Specimen

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Y. G.; Baik, S. J.; Kim, G. S.; Heo, G. S.; Yoo, B. O.; Ahn, S. B.; Chun, Y. B. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    The specimen fabrication technique was established to machine the specimen from the irradiated materials. The wire cut EDM(electric discharge machine) was modified to fabricate the mechanical testing specimens from irradiated components and fuel claddings. The oxide layer removal system was also developed because the oxide layer on the surface of the irradiated components and claddings interrupted the applying the electric current during the processing. However, zirconium oxide is protective against further corrosion as well as beneficial to mechanical strength for the tensile deformation of the cladding. Thus, it is important to fabricate the irradiated specimens without removal of oxide layer on the surface of the irradiated structural components and claddings. In the present study, laser cutting system was introduced to fabricate the various mechanical testing specimens from the unirradiated fuel cladding and the feasibility of the laser cutting system was studied for the fabrication of various types of irradiated specimens in a hot cell at IMEF (Irradiated Materials Examination Facility) of KAERI. Laser beam machining system was introduced to fabricate the various mechanical testing specimens from the unirradiated fuel cladding and the dimensions were compared for the feasibility of the laser cutting system. The effect of surface oxide layer was also investigated for machining process of the zircaloy-4 fuel cladding and it was found that laser beam machining could be a useful tool to fabricate the specimens with surface oxide layer.

  5. Laser Correction of Delayed Posthypoxic Encephalopathies (Experimental Study

    Directory of Open Access Journals (Sweden)

    V. V. Moroz

    2009-01-01

    Full Text Available Objective: to study whether posthypoxic brain dysfunctions may be corrected by low-intensity laser irradiation an hour after hypovolemic hypotension at late postresuscitation stages (following 30 days. Material and methods. Experiments were carried out on high-anxious male albino rats weighing 280—300 g. The study model was one-hour hypovolemic hypotension (blood pressure 40 mm Hg, followed by blood reinfusion. The integrative brain function was evaluated from the indices of the rat orientative-trying behavior in the elevated cross labyrinth test. The depressive component of the rats’ behavior was examined in the forced swimming test. Plasma norepinephrine levels were measured. Laser irradiation was performed 30 days after blood reinfusion. Results. Laser irradiation used at late postresuscitation stages leads to the normalization of plasma norepinephrine levels, the reduction of anxiety in the rats, and their improved orientative-trying behavior. Conclusion. The positive impact of laser irradiation on the rat orientative-trying behavior is associated with its anxiolytic effect, in which the recovery of autonomic homeostasis plays a considerable role. Key words: blood loss, postresuscitative period, behavior, laser, posthypoxic encephalopathy, norepinephrine.

  6. 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

  7. A study of particle generation during laser ablation with applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chunyi [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained in-line using a differential mobility analyzer (DMA) and a particle counter. The experimental results show that the particle size varies with laser energy, laser pulsewidth, ambient gas flow rate and sample properties. The results serve as a basis for controlling the size of nanoparticles generated by laser ablation. Laser shadowgraph imaging was used to study mass ejection processes and mechanisms. At higher laser irradiance, some particles were ejected in the liquid and even in the solid phase. Time-resolved images show the propagation of the shockwaves: external shockwaves propagate outward and decelerate, and internal shockwaves reflect back and forth between the gas contact surface and the sample surface. The internal shockwave is proposed to cause the ejection of liquid particles when the internal shockwave strikes the liquid molten layer. A simulation based on vapor plume expansion was carried out and provides satisfactory agreement with experimental results. Different material properties result in different particle ejection behavior:particle ejection for most materials including metals result in a conically shaped envelope for the ejected material while ejection for silicon resembles a liquid jet. The difference in density change when the materials melt was proposed to be an important factor in the different ejection behavior. The characteristics of particles generated by laser ablation have a strong influence on the chemical analysis of the irradiated sample. Large particles are more difficult to completely vaporize and ionize, and induced preferential vaporization causes fractionation (i.e. a detected chemical composition that differs from the sample material). Large particles also result in spikes in

  8. Nuclear fuel safety studies by laser pulse heating

    International Nuclear Information System (INIS)

    Viswanadham, C.S.; Kumar, Santosh; Dey, G.K.; Kutty, T.R.G.; Khan, K.B.; Kumar, Arun; Jathar, V.P.; Sahoo, K.C.

    2009-01-01

    The behaviour of nuclear fuels under transient heating conditions is vital to nuclear safety. A laser pulse based heating system to simulate the transient heating conditions experienced by the fuel during reactor accidents like LOCA and RIA is under development at BARC, Mumbai. Some of the concepts used in this system are under testing in pilot studies. This paper describes the results of some pilot studies carried out on unirradiated UO 2 specimens by laser pulse heating, followed by metallography and X-ray diffraction measurements. (author)

  9. GAP WIDTH STUDY IN LASER BUTT-WELDING

    DEFF Research Database (Denmark)

    Gong, Hui; Olsen, Flemming Ove

    power : 2 and 2.6 kW and the focal point position : 0 and -1.2 mm. Quality of all the butt welds are destructively tested according to ISO 13919-1.Influences of the variable process parameters to the maximum allowable gap width are observed as (1) the maximum gap width is inversely related......In this paper the maximum allowable gap width in laser butt-welding is intensively studied. The gap width study (GWS) is performed on the material of SST of W1.4401 (AISI 316) under various welding conditions, which are the gap width : 0.00-0.50 mm, the welding speed : 0.5-2.0 m/min, the laser...... to the welding speed, (2) the larger laser power leads to the bigger maximum allowable gap width and (3) the focal point position has very little influence on the maximum gap width....

  10. Study of multicharged ions in the laser-produced plasmas

    International Nuclear Information System (INIS)

    Jaegle, P.; Carillon, A.; Jamelot, G.; Wehenkel, C.; Sureau, A.; Guennou, H.

    1980-01-01

    With respect to hot plasmas, laser induced plasmas have an especially high density, with a steep partial gradient and a fast temporal variation of temperature and density. The study of multicharged ion radiation, wich is necessary to perform diagnostics of plasma parameters, opens a new field for atomic physics investigations, including identification of peculiar lines, which are not observed in other conditions, large changes in line profiles due to radiative transfer and to both shift and broadening by Stark effect. Departure from population equilibrium takes place in these plasmas, going possibly so far as population inversion between ionic levels in an energy range covering EUV and soft X-rays. Experimental and theoretical study of these phenomena are in progress and needs to find solutions for complicated problems. Here, recent works performed with the laser of the GRECO 'Interaction Laser-Matiere' are briefly presented [fr

  11. Studies of the confinement at laser-induced backside dry etching using infrared nanosecond laser pulses

    Science.gov (United States)

    Ehrhardt, M.; Lorenz, P.; Bayer, L.; Han, B.; Zimmer, K.

    2018-01-01

    In the present study, laser-induced backside etching of SiO2 at an interface to an organic material using laser pulses with a wavelength of λ = 1064 nm and a pulse length of τ = 7 ns have been performed in order to investigate selected processes involved in etching of the SiO2 at confined ablation conditions with wavelengths well below the band gap of SiO2. Therefore, in between the utilized metallic absorber layer and the SiO2 surface, a polymer interlayer with a thickness between 20 nm to 150 nm was placed with the aim, to separate the laser absorption process in the metallic absorber layer from the etching process of the SiO2 surface due to the provided organic interlayer. The influence of the confinement of the backside etching process was analyzed by the deposition of different thick polymer layers on top of the metallic absorber layer. In particular, it was found that the SiO2 etching depth decreases with higher polymer interlayer thickness. However, the etching depth increases with increasing the confinement layer thickness. SEM images of the laser processed areas show that the absorber and confinement layers are ruptured from the sample surface without showing melting, and suggesting a lift off process of these films. The driving force for the layers lift off and the etching of the SiO2 is probably the generated laser-induce plasma from the confined ablation that provides the pressure for lift off, the high temperatures and reactive organic species that can chemically attack the SiO2 surface at these conditions.

  12. Studies of electron transitions using solid He pressure techniques

    International Nuclear Information System (INIS)

    Schirber, J.E.

    1977-01-01

    Changes in the topology of the Fermi surfaces of metals occur with variation of temperature or stoichiometry in a number of metallic systems of current interest. Pressure generated by a variety of techniques has proven to be the most useful experimental variable in the study of these transitions, but in most cases only solid He techniques yield sufficiently hydrostatic conditions to permit direct measurements of the Fermi surface as a function of pressure

  13. Laser study of phase changes in the surface layer of porous materials

    International Nuclear Information System (INIS)

    Wojtatowicz, T W

    2001-01-01

    The paper presents some aspects of the use of interference patterns observed upon reflection of laser radiation from the surface of a porous solid (laser speckles) for the study of moisture condensation in the near-surface layer. (interaction of laser radiation with matter. laser plasma)

  14. The study on laser photochemical process of Diazonaphthoquinon-Cresol system

    International Nuclear Information System (INIS)

    Wei Jie; Huang Yu Li; Wang Wenke

    1999-01-01

    The kinetic process of laser photochemical reaction of diazonaphthoquinon-cresol system was studied by using laser spectrophotofluorimetry and laser induced fluorescence attenuation method. The nonlinear relationship between photodecomposition rate of the sensitizer and laser power, exposure time and concentration of solutions was discussed in detail

  15. Study of laser bending of a preloaded Titanium alloy sheet

    Directory of Open Access Journals (Sweden)

    Wang Xiufeng

    2014-01-01

    Full Text Available Laser bending of sheet metals with preload offers some attractive characteristics/merits, comparing to laser free bending without prestressing on the metals. The study reported in this paper was focused on a Titanium alloy which finds widespread applications in aerospace manufacturing. FE simulation of laser bending with prestressing on the Titanium alloy sheet was conducted for the analysis of the bending process and experiment carried out to verify the model and the result. It was shown that the simulation result is close to that measured in the experiment. Based on the computed result, the load-displacement curve was analysed and transmission efficiency of the elastic energy defined to evaluate the bending effect. These enhanced understanding of the mechanism of laser bending with a preload. A method for the optimization on technological parameters was further proposed. Referring to the deformation targeted, the preload value was determined through the FE simulation. The result showed that, on the premise that the specimen surface can be prevented from damaging, transmission efficiency of the elastic energy could reach to the maximum value through adjusting technological parameters of the laser system and deformation accuracy of the specimen could also be improved through this approach. The work presented in this paper may find its application in the manufacture of Titanium alloy sheets with a more cost-effective and a more precise way.

  16. Glass transition near the free surface studied by synchrotron radiation

    International Nuclear Information System (INIS)

    Sikorski, M.

    2008-06-01

    A comprehensive picture of the glass transition near the liquid/vapor interface of the model organic glass former dibutyl phthalate is presented in this work. Several surface-sensitive techniques using x-ray synchrotron radiation were applied to investigate the static and dynamic aspects of the formation of the glassy state from the supercooled liquid. The amorphous nature of dibutyl phthalate close to the free surface was confirmed by grazing incidence X-ray diffraction studies. Results from X-ray reflectivity measurements indicate a uniform electron density distribution close to the interface excluding the possibility of surface freezing down to 175 K. Dynamics on sub-μm length-scales at the surface was studied with coherent synchrotron radiation via x-ray photon correlation spectroscopy. From the analysis of the dispersion relation of the surface modes, viscoelastic properties of the dibutyl phthalate are deduced. The Kelvin-Voigt model of viscoelastic media was found to describe well the properties of the liquid/vapor interface below room temperature. The data show that the viscosity at the interface matches the values reported for bulk dibutyl phthalate. The scaled relaxation rate at the surface agrees with the bulk data above 210 K. Upon approaching the glass transition temperature the free surface was observed to relax considerably faster close to the liquid/vapor interface than in bulk. The concept of higher relaxation rate at the free surface is also supported by the results of the quasielastic nuclear forward scattering experiment, during which dynamics on molecular length scales around the calorimetric glass transition temperature is studied. The data were analyzed using mode-coupling theory of the glass transition and the model of the liquid(glass)/vapor interface, predicting inhomogeneous dynamics near the surface. The quasielastic nuclear forward scattering data can be explained when the molecular mobility is assumed to decrease with the increasing

  17. Glass transition near the free surface studied by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sikorski, M.

    2008-06-15

    A comprehensive picture of the glass transition near the liquid/vapor interface of the model organic glass former dibutyl phthalate is presented in this work. Several surface-sensitive techniques using x-ray synchrotron radiation were applied to investigate the static and dynamic aspects of the formation of the glassy state from the supercooled liquid. The amorphous nature of dibutyl phthalate close to the free surface was confirmed by grazing incidence X-ray diffraction studies. Results from X-ray reflectivity measurements indicate a uniform electron density distribution close to the interface excluding the possibility of surface freezing down to 175 K. Dynamics on sub-{mu}m length-scales at the surface was studied with coherent synchrotron radiation via x-ray photon correlation spectroscopy. From the analysis of the dispersion relation of the surface modes, viscoelastic properties of the dibutyl phthalate are deduced. The Kelvin-Voigt model of viscoelastic media was found to describe well the properties of the liquid/vapor interface below room temperature. The data show that the viscosity at the interface matches the values reported for bulk dibutyl phthalate. The scaled relaxation rate at the surface agrees with the bulk data above 210 K. Upon approaching the glass transition temperature the free surface was observed to relax considerably faster close to the liquid/vapor interface than in bulk. The concept of higher relaxation rate at the free surface is also supported by the results of the quasielastic nuclear forward scattering experiment, during which dynamics on molecular length scales around the calorimetric glass transition temperature is studied. The data were analyzed using mode-coupling theory of the glass transition and the model of the liquid(glass)/vapor interface, predicting inhomogeneous dynamics near the surface. The quasielastic nuclear forward scattering data can be explained when the molecular mobility is assumed to decrease with the increasing

  18. Optical studies of intersublevel-transitions in self-organized InGaAs/GaAs quantum dots

    International Nuclear Information System (INIS)

    Weber, A.

    2005-01-01

    In this thesis intersublevel-transitions in self-organized InGaAs/GaAs quantum dots are studied with spectroscopic methods. The charge-dependent absorption behaviour of the nanostructures in the intermediate infrared is studied by a new combination of Fourier spectroscopy and calorimetric absorption spectroscopy. Optical absorption in the quantum dots leads to a sample heating by charge-carrier relaxations, whereby non-radiative intersublevel transitions in the quantum dots are directly determined. The effects observed thereby are explained by different charge-carrier occupation, Pauli blocking, and many-=particle effects in the quantum dots. Furthermore intermediate-infrared emission from quantum dots is spectroscopically studied both under optical and electrical excitation. Each according to the structure of the waveguides in the samples emission peaks are shown, the intensity of which grows either sublinearly with the excitation power and finally saturates or exhibits a significantly superlinear growth. Simulations of an intermediate-infrared quantum-dot laser, which regard also the simultaneous intermediate-infrared emission, show that the observed superlinear growth is to be explained by intersublevel emission in the laser mode. The principal feasibility of a bipolar two-colour laser, which emits in the near- and in the intermediate infrared, is shown by this

  19. Studies on widely tunable ultra-short laser pulses using energy transfer distributed feedback dye laser

    International Nuclear Information System (INIS)

    Ahamed, M.B.; Ramalingam, A.; Palanisamy, P.K.

    2003-01-01

    This paper presents both theoretical and experimental study of the characteristics of Nd: YAG laser pumped energy transfer distributed feedback dye laser (ETDFDL). Using theoretical model proposed, the behavior of ETDFDL such as the characteristics of donor DFDL, the acceptor DFDL, the dependence of their pulse width and output power on donor-acceptor concentrations and pump power are studied for dye mixture Rhodamine 6G and Cresyl Violet in detail. Experimentally using prism-dye cell configuration, the ETDFDL output is obtained and the output energy of DFDL is measured at the emission peaks of donor and acceptor dyes for different pump powers and donor-acceptor concentrations. In addition, the DFDL linewidth measurement has been carried out at the lasing wavelengths of the donor and acceptor dyes using Fabry-Perot etalon and the tunability of DFDL is measured to be in the wavelength range of 545-680 nm

  20. Studying the mechanism of micromachining by short pulsed laser

    Science.gov (United States)

    Gadag, Shiva

    economical, because the micromachining rates are much higher than in the case of the ultra-short pulsed lasers. Hence, studying the mechanisms of micromachining by nanosecond pulsed laser of semiconductor silicon, transparent dielectric glass and quartz is undertaken for this research work. Laser drilling of an array of miniaturized micro holes is termed as laser micro via. A study of the effect of laser wavelengths, frequency, and energy of the pulses on the depth and diameter of craters and micro via are carried out using high resolution optical microscopy and a nano via 3D profiler. Analytical equations correlating depth and volume of the crater in terms of the optical absorption coefficient and ratio of peak applied to the threshold fluence for ablation of the silicon are derived. The depth of crater is scaled in terms of optical penetration depth times the ratio of crater diameter to the beam diameter. The shorter UV wavelengths are found to be more suitable for ablation of Si and SiO2 than longer IR wavelengths from the study of the absorption coefficient of Si varying with wavelength. Hence, the UV lasers (266 nm or 355 nm) are used for micromachining of Si and SiO2 involving cutting, cleaning, drilling and dicing, micro-milling and texturing of submicron size vertically oriented silicon wires for photovoltaic applications. The high density vertical wires are useful to grab a greater density of solar energy to generate more environmentally-friendly green power. The laser drilling of micro via can be typically of two types: (1) percussion drilling using a stationary laser beam with single or multiple pulses of the laser or (2) trepanned drilling of micro via by the circular motion of laser. Numerical simulation of dynamic drilling of laser micro via of silicon is performed, using control volume (FV) Fluent code in a Cartesian co-ordinate system. Total enthalpy formulation is used to simulate the phase change taking place during the laser ablation process from melting

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

    International Nuclear Information System (INIS)

    Ferrer, R.; Sonnenschein, V.T.; Bastin, B.; Franchoo, S.; Huyse, M.; Kudryavtsev, Yu.; Kron, T.; Lecesne, N.; Moore, I.D.; Osmond, B.; Pauwels, D.; Radulov, D.; Raeder, S.; Rens, L.

    2012-01-01

    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 63 Cu. A final run under on-line conditions in which the radioactive isotope 59 Cu (T 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.

  2. In vitro studies with a pulsed neodymium/YAG laser.

    Science.gov (United States)

    Venkatesh, S; Guthrie, S; Foulds, W S; Lee, W R; Cruickshank, F R; Bailey, R T

    1985-02-01

    The relationships between the destructive effects of Q-switched Nd/YAG laser pulses and a number of experimental parameters were studied for various target materials including in particular excised, fixed samples of human trabecular meshwork. The laser parameters altered were the pulse energy, the convergence angle of the focused beam, and the position of the focus of the beam relative to the target's axial position. The main finding was that it was possible to make deep holes, of a diameter less than 100 micron, in virtually transparent samples of trabecular meshwork with a laser delivery system of 6 degrees convergence and pulse energies of 14 mJ or more. The relevance of this and the other experimental results to the development of a reliable system for performing internal trabeculotomies for the treatment of open-angle glaucoma is presented.

  3. Parametric study on femtosecond laser pulse ablation of Au films

    International Nuclear Information System (INIS)

    Ni Xiaochang; Wang Chingyue; Yang Li; Li Jianping; Chai Lu; Jia Wei; Zhang Ruobing; Zhang Zhigang

    2006-01-01

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

  4. Bibliographic study of photophysical and photochemical properties of laser dyes

    International Nuclear Information System (INIS)

    Doizi, D.

    1986-06-01

    Laser isotope separation of uranium requires high power and precise wave length. This report is a bibliographic and experimental study of the photophysical and photochemical properties of seven commercial laser dyes which have an emission wavelength in the range 5500-6500 A: Rhodamine 110 or 560, rhodamine 6G or 590, rhodamine B or 610, rhodamine 101 or 640, sulforhodamine B or kiton red 620, sulforhodamine 101 or 640 and DCM or LC 6500. Absorption and emission cross section values, fluorescence lifetimes and quantum yields in various solvents are indicated. For each dye, a non exhaustive list of laboratory experiments made with two types of pump sources: Nd YAG (532) and copper vapor laser is given. When it is known, the toxicity of the dyes is mentioned [fr

  5. Laser fusion systems design study. Final technical report

    International Nuclear Information System (INIS)

    1975-06-01

    This study investigated: (1) the formulation and evaluation of an alignment system to accomplish pointing, focusing, centering and translation for the 20-arm SHIVA laser, (2) the formulation and evaluation of concepts for the correction of static phase distortions introduced by the accumulated optical elements in the laser chains, (3) the formulation and evaluation of concepts for the correction of optical path length differences between the arms of the SHIVA system, and (4) the conceptual design of appropriate control system hardware. (U.S.)

  6. Study of transition metal oxides by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Rao, C.N.R.; Sarma, D.D.; Vasudevan, S.; Hegde, M.S.

    1979-01-01

    Systematics in the X-ray photoelectron spectra (X.p.e.s.) of Ti, V, Cr, Mn and Nb oxides with the metal ion in different oxidation states as well as of related series of mono-, sesqui- and di-oxides of the first row of transition metals have been investigated in detail. Core level binding energies, spin-orbit splittings and exchange splittings are found to exhibit interesting variations with the oxidation state of the metal or the nuclear charge. The 3d binding energies of the monoxides show a proportionality to Goodenough's (R - RC). Other aspects of interest in the study are the satellite structure and final state effects in the X.p.e.s. of the oxides, and identification of different valence states in oxides of the general formulae Mn02n-1 and M304. The nature of changes in the 3d bands of oxides undergoing metal-insulator transitions is also indicated. (author)

  7. Behavior of χ(2) during a laser-induced phase transition in GaAs

    Science.gov (United States)

    Glezer, E. N.; Siegal, Y.; Huang, L.; Mazur, E.

    1995-04-01

    We explicitly determine the second-order optical susceptibility of GaAs following intense femtosecond laser-pulse excitation from second-harmonic-generation measurements. To separate the dependence of the 4.4-eV second-harmonic signal on the second-order susceptibility from its dependence on the linear dielectric constant, we use experimentally determined values for the dielectric constant of GaAs at 2.2 and 4.4 eV. The results show that the excitation of electrons and the resulting changes in the lattice affect the behavior of the second-order susceptibility. At pump fluences of 0.6 kJ/m2 and higher, the material loses long-range order on a time scale ranging from 100 femtoseconds to tens of picoseconds, depending on the pump fluence. A recovery of the second-order susceptibility to its initial value at pump fluences between 0.6 and 1.0 kJ/m2 shows that the loss of long-range order is reversible in this fluence regime.

  8. An Analysis of Public Transit Connectivity Index in Tehran. The Case Study: Tehran Multi-Modal Transit Network

    Directory of Open Access Journals (Sweden)

    Amir Reza Mamdoohi

    2016-10-01

    Full Text Available Public transit is a major priority in modern management of large cities and metropolitan areas in particular. Public transit systems in such cities consist of a large number of nodes and lines which are represented by a complex network. A station for public transit is a bridge between the people and public transit network, based on which, the concept of input and output power for each station can be defined. The objective of this study is the application of the transit connectivity indices to the multimodal transit network in the city of Tehran. The public transit network data employed in this study is taken from Tehran Traffic Control Company, and Tehran Urban and Suburban Railway Operation Company. The methodology for measuring transit connectivity consists of three measures: Node connectivity, Line connectivity and Regional connectivity, where activity density is applied to these measures. The results of node connectivity analysis shows that most of the node connectivity in concentrated in the city center with many nodes in the center along routes going north and south. The line connectivity analysis shows that there is a concentration of highly connected lines that are near Tehran municipality region 12 and 16. Finally, we find that areas with more metro and bus facilities with respect to the other areas, have a better regional connectivity. One of these areas includes Sadeghiyeh Metro Station which is the junction of Tehran Metro Line 2 and Tehran Metro Line 5 which have a high connectivity power. Results of this study can be used to suggest some ideas on how future investments in rail and bus should be prioritized. Particularly in Transit Oriented Development (TOD and sustainble development projects, urban planners can design transit stations with high performance to access the crucial services in poor areas.

  9. Parametric study of a target factory for laser fusion

    International Nuclear Information System (INIS)

    Sherohman, J.W.; Meier, W.R.

    1980-01-01

    An analysis of a target factory leading to the derivation of production rate equations has provided the basis for a parametric study. Rate equations describing the production of laser fusion targets have been developed for the purpose of identifying key parameters, attractive production techniques and cost scaling relationships for a commercial target factory

  10. TEM studies of P+ implanted and subsequently laser annealed Si

    International Nuclear Information System (INIS)

    Sadana, D.K.; Wilson, M.C.; Booker, G.R.; Washburn, J.

    1979-05-01

    The present investigation is concerned with laser annealing of P + implanted Si. The aim of the work was to study the crystallization behavior of damage structure occurring due to high dose rate implantation using transmission electron microscopy (TEM) as the method of examination

  11. Study of shock coalescence in laser-irradiated targets

    International Nuclear Information System (INIS)

    Coe, S.E.; Willi, O.; Afshar-Rad, T.; Rose, S.J.

    1988-01-01

    We report on the first direct experimental observation of the coalescence of two shocks induced by a shaped laser pulse. Optical streak photography of the rear surface of aluminum multiple step targets was used to study the breakout of these shocks and observe their behavior. The experimental results are compared with simulations by a one-dimensional Lagrangian hydrodynamic code

  12. Recent studies of laser science in paintings conservation and research.

    Science.gov (United States)

    Pouli, Paraskevi; Selimis, Alexandros; Georgiou, Savas; Fotakis, Costas

    2010-06-15

    The removal of aged and deteriorated molecular overlayers from the surface of paintings is a delicate and critical intervention in Cultural Heritage (CH) conservation. This irreversible action gets particularly complicated given the multitude of materials that may be present within a painted work of art (often in ultrathin layers or traces), as well as the exceptional sensitivity of the original surfaces to environmental conditions such as heat, light, and so on. Lasers hold an important role among the available cleaning methodologies, as they enable high control and accuracy, material selectivity, and immediate feedback. Still, prior to their implementation, it is imperative to optimize the cleaning parameters, so to ensure that any potential implications to the remaining materials are minimal and well understood. Toward this aim, research at IESL-FORTH is focused on both refining and continuously updating the laser-cleaning protocols (by introducing novel laser technologies into the field, i.e., ultrashort laser pulses), as well as on investigating and studying the nature and extent of laser-induced physicochemical alterations to the involved materials. In this Account, extended work for the understanding of ultraviolet (UV) laser ablation of polymers is presented. Emphasis is placed on the use of model systems (polymers doped with chromophores of known photochemistry) to examine the in-depth laser-induced modifications at the processed surfaces and thus to illustrate the dependence of their nature and extent on laser parameters and material properties. Furthermore, studies for the potential use of femtosecond UV pulses to overcome certain limitations involved with the nanosecond ablation of molecular overlayers from CH surfaces are highlighted. In particular, it is demonstrated that in the femtosecond regime any chemical modifications are, qualitatively and quantitatively, highly defined, limited and nearly independent of the material properties, such as the

  13. Studies of Positron Generation from Ultraintense Laser-Matter Interactions

    Science.gov (United States)

    Williams, Gerald Jackson

    Laser-produced pair jets possess unique characteristics that offer great potential for their use in laboratory-astrophysics experiments to study energetic phenomenon such as relativistic shock accelerations. High-flux, high-energy positron sources may also be used to study relativistic pair plasmas and useful as novel diagnostic tools for high energy density conditions. Copious amounts of positrons are produced with MeV energies from directly irradiating targets with ultraintense lasers where relativistic electrons, accelerated by the laser field, drive positron-electron pair production. Alternatively, laser wakefield accelerated electrons can produce pairs by the same mechanisms inside a secondary converter target. This dissertation describes a series of novel experiments that investigate the characteristics and scaling of pair production from ultraintense lasers, which are designed to establish a robust platform for laboratory-based relativistic pair plasmas. Results include a simple power-law scaling to estimate the effective positron yield for elemental targets for any Maxwellian electron source, typical of direct laser-target interactions. To facilitate these measurements, a solenoid electromagnetic coil was constructed to focus emitted particles, increasing the effective collection angle of the detector and enabling the investigation of pair production from thin targets and low-Z materials. Laser wakefield electron sources were also explored as a compact, high repetition rate platform for the production of high energy pairs with potential applications to the creation of charge-neutral relativistic pair plasmas. Plasma accelerators can produce low-divergence electron beams with energies approaching a GeV at Hz frequencies. It was found that, even for high-energy positrons, energy loss and scattering mechanisms in the target create a fundamental limit to the divergence and energy spectrum of the emitted positrons. The potential future application of laser

  14. Semianalytical study of the propagation of an ultrastrong femtosecond laser pulse in a plasma with ultrarelativistic electron jitter

    Energy Technology Data Exchange (ETDEWEB)

    Jovanović, Dušan, E-mail: dusan.jovanovic@ipb.ac.rs [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Zemun (Serbia); Fedele, Renato, E-mail: renato.fedele@na.infn.it [Dipartimento di Fisica, Università di Napoli “Federico II,” M.S. Angelo, Napoli (Italy); INFN Sezione di Napoli, Complesso Universitario di M.S. Angelo, Napoli (Italy); Belić, Milivoj, E-mail: milivoj.belic@qatar.tamu.edu [Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar); De Nicola, Sergio, E-mail: sergio.denicola@spin.cnr.it [SPIN-CNR, Complesso Universitario di M.S. Angelo, Napoli (Italy)

    2015-04-15

    The interaction of a multi-petawatt, pancake-shaped laser pulse with an unmagnetized plasma is studied analytically and numerically in a regime with ultrarelativistic electron jitter velocities, in which the plasma electrons are almost completely expelled from the pulse region. The study is applied to a laser wakefield acceleration scheme with specifications that may be available in the next generation of Ti:Sa lasers and with the use of recently developed pulse compression techniques. A set of novel nonlinear equations is derived using a three-timescale description, with an intermediate timescale associated with the nonlinear phase of the electromagnetic wave and with the spatial bending of its wave front. They describe, on an equal footing, both the strong and the moderate laser intensity regimes, pertinent to the core and to the edges of the pulse. These have fundamentally different dispersive properties since in the core the electrons are almost completely expelled by a very strong ponderomotive force, and the electromagnetic wave packet is imbedded in a vacuum channel, thus having (almost) linear properties. Conversely, at the pulse edges, the laser amplitude is smaller, and the wave is weakly nonlinear and dispersive. New nonlinear terms in the wave equation, introduced by the nonlinear phase, describe without the violation of imposed scaling laws a smooth transition to a nondispersive electromagnetic wave at very large intensities and a simultaneous saturation of the (initially cubic) nonlocal nonlinearity. The temporal evolution of the laser pulse is studied both analytically and by numerically solving the model equations in a two-dimensional geometry, with the spot diameter presently used in some laser acceleration experiments. The most stable initial pulse length is estimated to exceed ≳1.5–2 μm. Moderate stretching of the pulse in the direction of propagation is observed, followed by the development of a vacuum channel and of a very large

  15. Study of the laser-induced forward transfer of liquids for laser bioprinting

    Science.gov (United States)

    Duocastella, M.; Colina, M.; Fernández-Pradas, J. M.; Serra, P.; Morenza, J. L.

    2007-07-01

    Laser-induced forward transfer (LIFT) is a direct-writing technique that allows printing patterns of diverse materials with a high degree of spatial resolution. In conventional LIFT a small fraction of a solid thin film is vaporized by means of a laser pulse focused on the film through its transparent holder, and the resulting material recondenses on the receptor substrate. It has been recently shown that LIFT can also be used to transfer materials from liquid films. This widened its field of application to biosensors manufacturing, where small amounts of biomolecules-containing solutions have to be deposited with high precision on the sensing elements. However, there is still little knowledge on the physical processes and parameters determining the characteristics of the transfers. In this work, different parameters and their effects upon the transferred material were studied. It was found that the deposited material corresponds to liquid droplets which volume depends linearly on the laser pulse energy, and that a minimum threshold energy has to be overcome for transfer to occur. The liquid film thickness was varied and droplets as small as 10 μm in diameter were obtained. Finally, the effects of the variation of the film to substrate distance were also studied and it was found that there exists a wide range of distances where the morphology of the transferred droplets is independent of this parameter, what provides LIFT with a high degree of flexibility.

  16. Nd:YAG laser in caries prevention: a clinical study

    International Nuclear Information System (INIS)

    Boari, Heloisa Gomes Dimiranda

    2000-01-01

    The caries prevention by using laser irradiation has been investigated during the last 30 years. The Nd: YAG laser associated with acidulated phosphate fluoride has been shown as a very promising technique for enamel caries prevention. The aim of this work was to clinically evaluate the efficiency of Nd: YAG laser associated with acidulated phosphate fluoride in pit and fissure caries prevention of children and adolescents. In this work it was determined the dye that enhance the effect of Nd: YAG laser in enamel. It was selected 242 pre-molar and molar teeth from 33 children and adolescents, aged from 7 to 15 years old. The selected teeth were free from caries or decalcification marks (active white marks) to the clinical and radiographic exams. The teeth were divided into two groups: the first group was laser irradiated and their homologous remained as a control. The right side teeth were dye-assisted Nd:YAG laser irradiated. The dye solution was a moisture of dust coal and equal parts of water and alcohol. The irradiation conditions were 60 mJ/10 Hz, optical fiber in contact mode, with diameter of 300 μm, resulting in an energy density of 84,9 J/cm 2 . The oclusal surface of the teeth was completely irradiated, specially on the slopes and in the deepest part of the pits and fissures. This procedure was repeated three times. In the sequence it was applied the acidulated phosphate fluoride for 4 minutes. On the left side teeth - control group- only acidulated phosphate fluoride was applied for the same time. The final examination considered the presence of caries and active white marks after a period of one year. There were statistical significant differences (p < 0.01) between the lased + fluoride group and the non irradiated group. The present study concluded that the technique used in this work can be an alternative clinical method for caries prevention. (author)

  17. Unique properties associated with normal martensitic transition and strain glass transition – A simulation study

    International Nuclear Information System (INIS)

    Wang, Dong; Ni, Yan; Gao, Jinghui; Zhang, Zhen; Ren, Xiaobing; Wang, Yunzhi

    2013-01-01

    Highlights: ► We model the unique properties of strain glass which is different from that of normal martensite. ► We describe the importance of point defects in the formation of strain glass and related properties. ► The role of point defect can be attributed to global transition temperature effect (GTTE) and local field effect (LFE). -- Abstract: The transition behavior and unique properties associated with normal martensitic transition and strain glass transition are investigated by computer simulations using the phase field method. The simulations are based on a physical model that assumes that point defects alter the thermodynamic stability of martensite and create local lattice distortion. The simulation results show that strain glass transition exhibits different properties from those found in normal martensitic transformations. These unique properties include diffuse scattering pattern, “smear” elastic modulus peak, disappearance of heat flow peak and non-ergodicity. These simulation predictions agree well with the experimental observations

  18. Experimental study and numerical simulation of the propulsion of microbeads by femtosecond laser filament

    International Nuclear Information System (INIS)

    Zhang Nan; Liu Weiwei; Xu Zhijun; Wang Mingwei; Zhu Xiaonong

    2008-01-01

    The light filament formed by intense femtosecond laser pulses in air can be used to generate the effective impulse to propel a micro glass bead. In this report, through both experimental studies and the corresponding numerical simulations that involve the dynamics of the nonlinear propagation of light and the laser ablation mechanism, we confirm that this propulsion scheme is based on the laser ablation of the target material. The fundamental characteristics of laser propulsion using a single ultrafast laser filament is also revealed

  19. Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations

    Directory of Open Access Journals (Sweden)

    Lkhamsuren Bayarjargal

    2011-09-01

    Full Text Available Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p; T stability, compressibility and hardness is described as obtained from experiments.

  20. Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations

    Science.gov (United States)

    Friedrich, Alexandra; Winkler, Björn; Juarez-Arellano, Erick A.; Bayarjargal, Lkhamsuren

    2011-01-01

    Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p,T) stability, compressibility and hardness is described as obtained from experiments. PMID:28824101

  1. Laser transit anemometer and Pitot probe comparative measurements in a sharp cone boundary layer at Mach 4

    Science.gov (United States)

    Hunter, W. W., Jr.; Ocheltree, S. L.; Russ, C. E., Jr.

    1991-01-01

    Laser transit anemometer (LTA) measurements of a 7 degree sharp cone boundary layer were conducted in the Air Force/AEDC Supersonic Tunnel A Mach 4 flow field. These measurements are compared with Pitot probe measurements and tricone theory provided by AEDC staff. Measurements were made both in laminar and turbulent boundary layers of the model. Comparison of LTA measurements with theory showed agreement to better than 1 percent for the laminar boundary layer cases. This level of agreement was obtained after small position corrections, 0.01 to 0.6 mm, were applied to the experimental data sets. Pitot probe data when compared with theory also showed small positioning errors. The Pitot data value was also limited due to probe interference with the flow near the model. The LTA turbulent boundary layer data indicated a power law dependence of 6.3 to 6.9. The LTA data was analyzed in the time (Tau) domain in which it was obtained and in the velocity domain. No significant differences were noted between Tau and velocity domain results except in one turbulent boundary layer case.

  2. Basic studies on laser-assisted phacoemulsification using diode-pumped Er:YAG laser

    Science.gov (United States)

    Hausladen, Florian; Wurm, Holger; Stock, Karl

    2016-03-01

    The aim of this study was to determine the potential of a novel diode-pumped Er:YAG laser for phacoemulsification in basic experimental investigations. An appropriate experimental setup was created, including a translation stage for sample movement, a sample holder, a water spray for sample humidification and a surgical microscope with a CCD camera for video documentation. The analysis of the laser cuts and histological sections was done by light microscopy. As samples porcine eye lenses hardened by formalin were used. In ablation experiments with different spot diameters and radiant powers and a constant repetition rate νr = 200 Hz the maximum ablation depths of (4.346 +/- 0.044) mm have reached at (Ø = 480 μm, Φ = 24.15 W) with a maximum extend of thermal damage of (0.165 +/- 0.030) mm. The average ablation efficiency is 0.241 mm3/J. With a spot diameter of 308 μm the maximum ablation depth is (4.238 +/- 0.040) mm at 24.65 W with a mean ablation efficiency of 0.293 mm3/J. The extend of the thermally damaged region is (0.171 +/- 0.024) mm at this laser power. Using a sapphire cylinder with a diameter of 412 μm (length 38.5 mm) in direct tissue contact with water spray for sample humidification the ablation depth reaches (1.017 +/- 0.074) mm at 4.93 W and (1.840 +/- 0.092) mm at 9.87 W with a mean efficiency of 0.261 mm3/J. A thermal damage zone of (0.064 +/-0.024) mm at 9.87 W was measured. Additionally, at this high power, a progressive contamination and destruction of the cylinder end facet was observed. In conclusion, the investigations show that the diode-pumped Er:YAG laser has considerable potential for cataract surgery.

  3. Comparison of two picosecond lasers to a nanosecond laser for treating tattoos: a prospective randomized study on 49 patients.

    Science.gov (United States)

    Lorgeou, A; Perrillat, Y; Gral, N; Lagrange, S; Lacour, J-P; Passeron, T

    2018-02-01

    Q-switched nanosecond lasers demonstrated their efficacy in treating most types of tattoos, but complete disappearance is not always achieved even after performing numerous laser sessions. Picosecond lasers are supposed to be more efficient in clearing tattoos than nanosecond lasers, but prospective comparative data remain limited. To compare on different types of tattoos the efficacy of a nanosecond laser with two types of picosecond lasers. We conducted a prospective randomized study performed from December 2014 to June 2016 on adult patients with all types of tattoos. The tattoos were divided into two halves of equal size. After randomization, half of the tattoo was treated with a picosecond laser and the other half with a nanosecond laser. The evaluation was performed on standardized pictures performed before treatment and 2 months after the last session, by two physicians, not involved in the treatment, blinded on the type of treatments received. The main end point was a clearance above 75% of the tattoos. A total of 49 patients were included. Professional tattoos represented 85.7%, permanent make-up 8.2% and non-professional tattoo 6.1%. The majority were black or blue and 10.2% were polychromatic. No patient was lost during follow-up. A reduction of 75% or more of the colour intensity was obtained for 33% of the tattoos treated with the picosecond lasers compared to 14% with the nanosecond laser (P = 0.008). An improvement superior to 75% was obtained in 34% monochromic black or blue tattoos with the picosecond lasers compared to 9% for the nanosecond laser. Only one of the five polychromic tattoos achieved more than 75% of improvement with the two types of laser. Our results show a statistically significant superiority of the picosecond lasers compared to the nanosecond laser for tattoo clearance. However, they do not show better efficacy for polychromic tattoos and the difference in terms of side-effects was also minimal with a tendency of picosecond

  4. Infrared, Raman and laser fluorescence studies on large molecules

    International Nuclear Information System (INIS)

    Venkateswaran, Sugandhi

    2000-01-01

    In the present thesis, infrared and Raman spectroscopic studies on large molecules, molecular assemblies and crystalline solids, as a function of temperature, pressure and added materials have been carried out. Spectral changes observed in our studies are interpreted in terms of intermolecular interaction, phase transition and conformational changes taking place in the molecules studied

  5. Hyperfine structure of the metastable p-barHe+ atom revealed by a laser-induced (n,l) = (37,35) → (38,34) transition

    International Nuclear Information System (INIS)

    Widmann, E.; Eades, J.; Yamazaki, T.

    1996-11-01

    A precise scan of the previously discovered laser-induced transition (n,l) = (37,35) → (38,34) in p-barHe + revealed a doublet structure with a separation of Δν HF = 1.70 ± 0.05 GHz. This new type of 'hyperfine' splitting is ascribed to the interaction of the antiproton orbital angular momentum and the electron spin. (author)

  6. High-resolution absorption spectrum of the 61S0 → 63P1 transition in mercury with a Cw dye laser

    International Nuclear Information System (INIS)

    Crane, J.K.; Erbert, G.V.; Mostek, S.D.; Kerlin, R.C.; Paisner, J.A.

    1985-01-01

    Using a stabilized single-frequency commercial dye laser and an external cavity doubling crystal, we have measured the isotope shifts of mercury for the 6 1 S 0 → 6 3 P 1 transition with an accuracy of 4 MHz. We describe the method for generating single-frequency light at 2537 A and compare the results of our measurements of the isotope shifts with previous work. 7 refs., 5 figs., 1 tab

  7. Laser spectroscopy of the 4s4p(3) P-2-4s3d(1) D-2 transition on magnetically trapped calcium atoms

    NARCIS (Netherlands)

    Dammalapati, U.; Norris, I.; Burrows, C.; Riis, E.

    2011-01-01

    Laser excitation of the 4s4p(3) P-2-4s3d(1) D-2 transition in atomic calcium has been observed and the wavelength determined to 1530.5298(6) nm. The metastable 4s4p(3) P-2 atoms were magnetically trapped in the quadrupole magnetic field of a magneto-optical trap. This state represents the only

  8. Experimental and numerical study of the micro-spalling of metallic targets subjected to laser shock

    International Nuclear Information System (INIS)

    Loison, D.

    2012-01-01

    Micro-spalling is a failure phenomenon consisting in dynamic fragmentation of a material after partial or full melting under intense shock wave loading. High power pulsed lasers are used as shock wave generators in laboratory for scientific and industrial purposes, such as research on inertial confinement fusion. In this context, the production of high velocity fragments can damage the facilities where shock experiments are conducted. This thesis, realized in collaboration with different teams from CEA, aims at understanding and modeling the different processes involved in micro-spalling phenomenon. Experiments to study micro-spalling of laser shock-loaded tin and aluminum targets have been performed. Various and complementary diagnostics (photonic Doppler velocimetry, soft recovery of debris and microtomography) have been used to characterize the ballistic properties (size distributions and velocities) of droplets constituting the micro-spalling cloud. In parallel, phase transition and fragmentation models have been adapted to simulate micro-spalling. These models have been implemented in a code to predict the sizes and velocities of debris. The combination of experimental and numerical results allows characterizing the successive stages of micro-spalling from laser-matter interaction to the ejection of droplets. (author)

  9. Studies on mechanisms of the laser particle acceleration

    International Nuclear Information System (INIS)

    Aurand, Bastian

    2012-01-01

    Within the last decade, many developments towards higher energies and particle numbers paved the way of particle acceleration performed by high intensity laser systems. Up to now, the process of a field-induced acceleration process (Target-Normal-Sheath-Acceleration (TNSA)) is investigated the most. Acceleration occurs as a consequence of separation of charges on a surface potential. Here, the broad energy spectrum is a problem not yet overcome although many improvements were achieved. Calculations for intensities higher than 10 20..21 W/cm 2 give hint that Radiation-Pressure-Acceleration (RPA) may lead to a sharper, monoenergetic energy spectrum. Within the framework of this thesis, the investigation of the acceleration mechanism is studied experimentally in the intensity range of 10 19 W/cm 2 . Suitable targets were developed and applied for patent. A broad range of parameters was scanned by means of high repetition rates together with an adequate laser system to provide high statistics of several thousands of shots, and the dependence of target material, intensity, laser polarisation and pre plasma-conditions was verified. Comparisons with 2-d numeric simulations lead to a model of the acceleration process which was analyzed by several diagnostic methods, giving clear evidence for a new, not field-induced acceleration process. In addition, a system for a continuous variation of the polarization based on reflective optics was developed in order to overcome the disadvantages of retardation plates, and their practicability of high laser energies can be achieved.

  10. Study of plasmas created by X-ray laser-matter interaction

    International Nuclear Information System (INIS)

    Galtier, E.

    2010-11-01

    This thesis took advantage of the emerging newly developed 4. generation sources of light, namely the free electron lasers, to create and characterize a state of matter under extreme conditions which is still obscure: the warm dense matter (WDM). WDM is found in giant planets and is also produced in inertial fusion. An experiment allowed to study the transitions between the different phases, solid/WDM/plasma, and characterize the mechanism responsible for the equilibration. The laser pulse FLASH, of duration and energy equal to about 20 femto-seconds and 30 μJ respectively, is micro-focussed on a solid target producing an isochoric heating. The intensity, greater than 10 16 W.cm -2 , has never been reached in such an experimental context so far. Emission spectra from an aluminium plasma are studied with a code coupling a genetic algorithm and a code of atomic physics, in order to interpret the whole temporal evolution of the XUV laser-matter interaction for the first time, despite the time integration of the experimental spectra. The first experimental proof of the important contribution of the Auger effect in the isochoric heating of an aluminium target is established. The first observation of the X-ray emission of a boron nitride target under extreme conditions has been investigated by a preliminary study. Additionally, the effect of hot electrons on the electron population distribution in the energy levels of the ions is analysed and shows an important similarity with the photo-ionization process occurring in XUV/X-ray laser-matter interaction. (author)

  11. Dose-dependent transitions in mechanisms of toxicity: case studies

    International Nuclear Information System (INIS)

    Slikker, William; Andersen, Melvin E.; Bogdanffy, Matthew S.; Bus, James S.; Cohen, Steven D.; Conolly, Rory B.; David, Raymond M.; Doerrer, Nancy G.; Dorman, David C.; Gaylor, David W.; Hattis, Dale; Rogers, John M.; Setzer, R. Woodrow; Swenberg, James A.; Wallace, Kendall

    2004-01-01

    Experience with dose response and mechanisms of toxicity has shown that multiple mechanisms may exist for a single agent along the continuum of the full dose-response curve. It is highly likely that critical, limiting steps in any given mechanistic pathway may become overwhelmed with increasing exposures, signaling the emergence of new modalities of toxic tissue injury at these higher doses. Therefore, dose-dependent transitions in principal mechanisms of toxicity may occur, and could have significant impact on the interpretation of reference data sets for risk assessment. To illustrate the existence of dose-dependent transitions in mechanisms of toxicity, a group of academic, government, and industry scientists, formed under the leadership of the ILSI Health and Environmental Sciences Institute (HESI), developed a series of case studies. These case studies included acetaminophen, butadiene, ethylene glycol, formaldehyde, manganese, methylene chloride, peroxisome proliferator-activated receptor (PPAR), progesterone/hydroxyflutamide, propylene oxide, vinyl acetate, vinyl chloride, vinylidene chloride, and zinc. The case studies formed the basis for technical discourse at two scientific workshops in 2003

  12. Observed transition from Richtmyer-Meshkov jet formation through feedout oscillations to Rayleigh-Taylor instability in a laser target

    International Nuclear Information System (INIS)

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Nikitin, S. P.; Oh, J.; Metzler, N.

    2012-01-01

    Experimental study of hydrodynamic perturbation evolution triggered by a laser-driven shock wave breakout at the free rippled rear surface of a plastic target is reported. At sub-megabar shock pressure, planar jets manifesting the development of the Richtmyer-Meshkov-type instability in a non-accelerated target are observed. As the shock pressure exceeds 1 Mbar, an oscillatory rippled expansion wave is observed, followed by the “feedout” of the rear-surface perturbations to the ablation front and the development of the Rayleigh-Taylor instability, which breaks up the accelerated target.

  13. Laser-spectroscopic nuclear-structure studies on radioactive silver and indium isotopes

    International Nuclear Information System (INIS)

    Dinger, U.

    1988-05-01

    Neutron-deficient silver and neutron-rich indium isotopes were studied by collinear laser spectroscopy. The neutron-deficient nuclei 101 , 103 , 104 , 105 , 105m , 106m Ag were produced as evaporation-residual nuclei in heavy-ion fusion reactions at the mass separator of the GSI in Darmstadt. The fourteen studied indium isotopes and isomers with even mass number in the range 112-126 In were produced by 600-MeV-proton induced fission of a uranium carbide target at the ISOLDE separator in Geneva. The mass-separated ion beam was subsequently deviated electrostatically, neutralized in a sodium vapor and superposed with a c w dye laser. A photon counting system detected the resonance fluorescence of the induced transitions. The hyperfine structure and the isotope shift of the 4d 9 5s 2 2 D 5/2 → 4d 10 6p 2 P 3/2 transition (λ=547.7 nm) in silver and the 5p 2 P 1/2,3/2 → 6s 2 s 1/2 transition (λ=410 respectively 451 nm) in indium were measured. While in indium for the analysis of the data earlier work could be referred to, in silver a detailed analysis of the isotope shift and hyperfine structure was performed by means of ab initio calculations and semi-empirical procedures. Thereby the configuration interactions were especially considered. The nuclear moments were discussed in the framework of existing nuclear models regarding nuclear-spectroscopic informations. (orig./HSI) [de

  14. High-power laser experiments to study collisionless shock generation

    Directory of Open Access Journals (Sweden)

    Sakawa Y.

    2013-11-01

    Full Text Available A collisionless Weibel-instability mediated shock in a self-generated magnetic field is studied using two-dimensional particle-in-cell simulation [Kato and Takabe, Astophys. J. Lett. 681, L93 (2008]. It is predicted that the generation of the Weibel shock requires to use NIF-class high-power laser system. Collisionless electrostatic shocks are produced in counter-streaming plasmas using Gekko XII laser system [Kuramitsu et al., Phys. Rev. Lett. 106, 175002 (2011]. A NIF facility time proposal is approved to study the formation of the collisionless Weibel shock. OMEGA and OMEGA EP experiments have been started to study the plasma conditions of counter-streaming plasmas required for the NIF experiment using Thomson scattering and to develop proton radiography diagnostics.

  15. Laser-plasma based electron acceleration studies planned at CAT, Indore

    International Nuclear Information System (INIS)

    Naik, P.A.; Gupta, P.D.

    2005-01-01

    The Laser Plasma Division at the Centre for Advanced Technology is engaged in a variety of R and D activities on laser-plasma interaction with special emphasis on laser-matter interaction at ultra-high intensities. An important aspect of our future work is studies in laser-plasma based acceleration using an elaborate infrastructural set-up of ultra-fast laser and plasma diagnostic systems and recently acquired 10 TW, 50 fs Ti: Sapphire laser system. This paper presents outline of the planned studies in this field. (author)

  16. Study on the high-frequency laser measurement of slot surface difference

    Science.gov (United States)

    Bing, Jia; Lv, Qiongying; Cao, Guohua

    2017-10-01

    In view of the measurement of the slot surface difference in the large-scale mechanical assembly process, Based on high frequency laser scanning technology and laser detection imaging principle, This paragraph designs a double galvanometer pulse laser scanning system. Laser probe scanning system architecture consists of three parts: laser ranging part, mechanical scanning part, data acquisition and processing part. The part of laser range uses high-frequency laser range finder to measure the distance information of the target shape and get a lot of point cloud data. Mechanical scanning part includes high-speed rotary table, high-speed transit and related structure design, in order to realize the whole system should be carried out in accordance with the design of scanning path on the target three-dimensional laser scanning. Data processing part mainly by FPGA hardware with LAbVIEW software to design a core, to process the point cloud data collected by the laser range finder at the high-speed and fitting calculation of point cloud data, to establish a three-dimensional model of the target, so laser scanning imaging is realized.

  17. Experimental studies of thorium ion implantation from pulse laser plasma into thin silicon oxide layers

    Science.gov (United States)

    Borisyuk, P. V.; Chubunova, E. V.; Lebedinskii, Yu Yu; Tkalya, E. V.; Vasilyev, O. S.; Yakovlev, V. P.; Strugovshchikov, E.; Mamedov, D.; Pishtshev, A.; Karazhanov, S. Zh

    2018-05-01

    We report the results of experimental studies related to implantation of thorium ions into thin silicon dioxide by pulsed plasma flux expansion. Thorium ions were generated by laser ablation from a metal target, and the ionic component of the laser plasma was accelerated in an electric field created by the potential difference (5, 10 and 15 kV) between the ablated target and a SiO2/Si (0 0 1) sample. The laser ablation system installed inside the vacuum chamber of the electron spectrometer was equipped with a YAG:Nd3  +  laser having a pulse energy of 100 mJ and time duration of 15 ns in the Q-switched regime. The depth profile of thorium atoms implanted into the 10 nm thick subsurface areas together with their chemical state as well as the band gap of the modified silicon oxide at different conditions of implantation processes were studied by means of x-ray photoelectron spectroscopy and reflected electron energy loss spectroscopy methods. Analysis of the chemical composition showed that the modified silicon oxide film contains complex thorium silicates. Depending on the local concentration of thorium atoms, the experimentally established band gaps were located in the range 6.0–9.0 eV. Theoretical studies of the optical properties of the SiO2 and ThO2 crystalline systems were performed by ab initio calculations within hybrid functional. The optical properties of the SiO2/ThO2 composite were interpreted on the basis of the Bruggeman effective medium approximation. A quantitative assessment of the yield of isomeric nuclei in ‘hot’ laser plasma at the early stages of expansion was performed. The estimates made with experimental results demonstrated that the laser implantation of thorium ions into the SiO2 matrix can be useful for further research of low-lying isomeric transitions in a 229Th isotope with energy of 7.8 +/- 0.5 eV.

  18. [Crystalline lens photodisruption using femtosecond laser: experimental study].

    Science.gov (United States)

    Chatoux, O; Touboul, D; Buestel, C; Balcou, P; Colin, J

    2010-09-01

    The aim of this study was to analyze the interactions during femtosecond (fs) laser photodisruption in ex vivo porcine crystalline lenses and to study the parameters for laser interaction optimization. An experimental femtosecond laser was used. The laser characteristics were: 1030 nm wavelength; pulse duration, 400 fs; and numerical aperture, 0.13. Specific software was created to custom and monitor any type of photoablation pattern for treatment purposes. Porcine crystalline lenses were placed in an open sky holder filled with physiological liquid (BSS) covered by a glass plate. A numerical camera was associated with metrological software in order to magnify and quantify the results. Transmission electron microscopy (TEM) was performed on some samples to identify the microscopic plasma interactions with the lens. The optimization of parameters was investigated in terms of the optical breakdown threshold, the sizing of interactions, and the best pattern for alignments. More than 150 crystalline lenses of freshly enucleated pigs were treated. The optical breakdown threshold (OBT) was defined as the minimal energy level per pulse necessary to observe a physical interaction. In our study, the OBT varied according to the following parameters: the crystalline lens itself, varying from 4.2 to 7.6 μJ (mean, 5.1 μJ), and the depth of laser focus, varying up to 1 μJ, increasing in the depth of the tissue. Analyzing the distance between impacts, we observed that the closer the impacts were the less power was needed to create a clear well-drawn defect pattern (lines), i.e., with a 4-μJ optimized OBT, when the impacts were placed every 2 μm for the x,y directions and 60 μm for the z direction. Coalescent bubbles created by plasma formation always disappeared in less than 24h. The nonthermal effect of plasma and the innocuousness on surrounding tissues were proven by the TEM results. The crystalline lens photodisruption by the femtosecond laser seems an innovative

  19. A numerical study of the integral equations for the laser fields in free-electron lasers

    International Nuclear Information System (INIS)

    Yoo, J. G.; Park, S. H.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.

    2004-01-01

    The dynamics of the radiation fields in free-electron lasers is investigated on the basis of the integro-differential equations in the one-dimensional formulation. For simple cases we solved the integro-differential equations analytically and numerically to test our numerical procedures developed on the basis of the Filon method. The numerical results showed good agreement with the analytical solutions. To confirm the legitimacy of the numerical package, we carried out numerical studies on the inhomogeneous broadening effects, where no analytic solutions are available, due to the energy spread and the emittance of the electron beam.

  20. The theoretical study of the optical klystron free electron laser

    International Nuclear Information System (INIS)

    Yang Zhenhua

    2001-01-01

    The work of the theoretical study and numerical simulation of optical klystron free electron laser is supported by National 863 Research Development Program and National Science Foundation of China. The object of studying UV band free electron laser (FEL) is to understand the physical law of optical klystron FEL and to gain experience for design. A three-dimensional code OPFEL are made and it is approved that the code is correct completely. The magnetic field of the optical klystron, the energy modulation of the electron beam, the density modulation of the electron beam, spontaneous emission of the electron beam in optical klystron, the harmonic super-radiation of the electron beam, and the effects of the undulator magnetic field error on modulation of the electron beam energy are simulated. These results are useful for the future experiments

  1. Nonlinear scattering in hard tissue studied with ultrashort laser pulses

    International Nuclear Information System (INIS)

    Eichler, J.; Kim, B.M.

    2002-01-01

    The back-scattered spectrum of ultrashort laser pulses (800 nm, 0.2 ps) was studied in human dental and other hard tissues in vitro below the ablation threshold. Frequency doubled radiation (SHG), frequency tripled radiation and two-photon fluorescence were detected. The relative yield for these processes was measured for various pulse energies. The dependence of the SHG signal on probe thickness was determined in forward and back scattering geometry. SHG is sensitive to linear polarization of the incident laser radiation. SHG in human teeth was studied in vitro showing larger signals in dentin than in cementum and enamel. In carious areas no SHG signal could be detected. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed. (orig.)

  2. Uranium speciation in biofilms studies by laser fluorescence techniques

    International Nuclear Information System (INIS)

    Arnold, Thuro; Grossmann, Kay; Baumann, Nils

    2010-01-01

    Biofilms may immobilize toxic heavy metals in the environment and thereby influence their migration behaviour. The mechanisms of these processes are currently not understood, because the complexity of such biofilms creates many discrete geochemical microenvironments which may differ from the surrounding bulk solution in their bacterial diversity, their prevailing geochemical properties, e.g. pH and dissolved oxygen concentration, the presence of organic molecules, e.g. metabolites, and many more, all of which may affect metal speciation. To obtain such information, which is necessary for performance assessment studies or the development of new cost-effective strategies for cleaning waste waters, it is very important to develop new non-invasive methods applicable to study the interactions of metals within biofilm systems. Laser fluorescence techniques have some superior features, above all very high sensitivity for fluorescent heavy metals. An approach combining confocal laser scanning microscopy and laser-induced fluorescence spectroscopy for study of the interactions of biofilms with uranium is presented. It was found that coupling these techniques furnishes a promising tool for in-situ non-invasive study of fluorescent heavy metals within biofilm systems. Information on uranium speciation and uranium redox states can be obtained.

  3. [Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

    Science.gov (United States)

    Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

    2015-11-01

    Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.

  4. Explosive Nucleosynthesis Study Using Laser Driven γ-ray Pulses

    Directory of Open Access Journals (Sweden)

    Takehito Hayakawa

    2017-03-01

    Full Text Available We propose nuclear experiments using γ-ray pulses provided from high field plasma generated by high peak power laser. These γ-ray pulses have the excellent features of extremely short pulse, high intensity, and continuous energy distribution. These features are suitable for the study of explosive nucleosyntheses in novae and supernovae, such as the γ process and ν process. We discuss how to generate suitable γ-ray pulses and the nuclear astrophysics involved.

  5. First-principles study of doping effect on the phase transition of zinc oxide with transition metal doped

    International Nuclear Information System (INIS)

    Wu, Liang; Hou, Tingjun; Wang, Yi; Zhao, Yanfei; Guo, Zhenyu; Li, Youyong; Lee, Shuit-Tong

    2012-01-01

    Highlights: ► We study the doping effect on B4, B1 structures and phase transition of ZnO. ► We calculate the phase transition barrier and phase transition path of doped ZnO. ► The transition metal doping decreases the bulk modulus and phase transition pressure. ► The magnetic properties are influenced by the phase transition process. - Abstract: Zinc oxide (ZnO) is a promising material for its wide application in solid-state devices. With the pressure raised from an ambient condition, ZnO transforms from fourfold wurtzite (B4) to sixfold coordinated rocksalt (B1) structure. Doping is an efficient approach to improve the structures and properties of materials. Here we use density-functional theory (DFT) to study doped ZnO and find that the transition pressure from B4 phase to B1 phase of ZnO always decreases with different types of transition metal (V, Cr, Mn, Fe, Co, or Ni) doped, but the phase transition path is not affected by doping. This is consistent with the available experimental results for Mn-doped ZnO and Co-doped ZnO. Doping in ZnO causes the lattice distortion, which leads to the decrease of the bulk modulus and accelerates the phase transition. Mn-doped ZnO shows the strongest magnetic moment due to its half filled d orbital. For V-doped ZnO and Cr-doped ZnO, the magnetism is enhanced by phase transition from B4 to B1. But for Mn-doped ZnO, Fe-doped ZnO, Co-doped ZnO, and Ni-doped ZnO, B1 phase shows weaker magnetic moment than B4 phase. These results can be explained by the amount of charge transferred from the doped atom to O atom. Our results provide a theoretical basis for the doping approach to change the structures and properties of ZnO.

  6. Long Scalelength Plasmas for LPI Studies at the Nike Laser

    Science.gov (United States)

    Weaver, J. L.; Oh, J.; Bates, J. W.; Schmitt, A. J.; Kehne, D. M.; Wolford, M. F.; Obenschain, S. P.; Serlin, V.; Lehmberg, R. H.; Follett, R. K.; Shaw, J. G.; Myatt, J. F.; McKenty, P. W.; Wei, M. S.; Reynolds, H.; Williams, J.; Tsung, F.

    2017-10-01

    Studies of laser plasma instabilities (LPI) at the Nike laser have mainly used short pulses, small focal spots, and solid plastic (CH) targets that have yielded maximum gradient scalelengths below 200 microns. The current experimental effort aims to produce larger volume plasmas with 5-10x reduction in the density and velocity gradients as a platform for SBS, SRS, and TPD studies. The next campaign will concentrate on the effects of wavelength shifting and bandwidth changes on CBET in low density (5-10 mg/cm3) CH foam targets. This poster will discuss the development of this new LPI target platform based on modelling with the LPSE code developed at LLE. The presentation will also discuss alternative target schemes (e.g. exploding foils) and improvements to the LPI diagnostic suite and laser operations; for example, a new set of etalons will be available for the next campaign that should double the range of available wavelength shifting. Upgrades to the scattered light spectrometers in general use for LPI studies will also be presented. Work supported by DoE/NNSA.

  7. Two-dimensional study of shock breakout at the rear face of laser irradiated metallic targets

    Energy Technology Data Exchange (ETDEWEB)

    Cottet, F.; Marty, L.; Hallouin, M.; Romain, J.P.; Virmont, J.; Fabbro, R.; Faral, B.

    1988-11-01

    The two-dimensional propagation dynamics of laser-driven shock waves in solids is studied through the analysis of the shock breakout at the rear face of the target for a set of materials and laser intensities. The laser shock simulations were carried out by means of a two-dimensional hydrodynamics code in which the laser-ablation pressure is replaced by an equivalent pressure pulse. It is shown that the two-dimensional code is a very useful tool to analyze laser-shock experiments where two-dimensional effects arise from a finite laser-spot size or a heterogeneous energy deposition.

  8. Two-dimensional study of shock breakout at the rear face of laser irradiated metallic targets

    International Nuclear Information System (INIS)

    Cottet, F.; Marty, L.; Hallouin, M.; Romain, J.P.; Virmont, J.; Fabbro, R.; Faral, B.

    1988-01-01

    The two-dimensional propagation dynamics of laser-driven shock waves in solids is studied through the analysis of the shock breakout at the rear face of the target for a set of materials and laser intensities. The laser shock simulations were carried out by means of a two-dimensional hydrodynamics code in which the laser-ablation pressure is replaced by an equivalent pressure pulse. It is shown that the two-dimensional code is a very useful tool to analyze laser-shock experiments where two-dimensional effects arise from a finite laser-spot size or a heterogeneous energy deposition

  9. Molecular dynamics stimulations to study laser dye aggregation in water (comparison with experiments)

    International Nuclear Information System (INIS)

    Dare-Doyen, St.; Doizi, D.

    2000-01-01

    A laser facility consists of dye laser chains where the active medium is composed of fluorescent dyes dissolved in ethanol. The use of water as a solvent would offer two major advantages: greater safety of the laser facility by drastically reducing fire risks, easier design of the laser beam correcting devices required at the end of the dye laser chains, thanks to the properties of water. Unfortunately, laser dyes exhibit poor optical properties in water, due to the formation of dye aggregates. Molecular dynamics simulations were used to study and develop means to prevent this behavior between two charged species. The results were compared with NMR (Nuclear Magnetic Resonance) experiments

  10. Study on Laser Induced Plasma Produced in Liquid

    International Nuclear Information System (INIS)

    Tsuda, N.; Yamada, J.

    2003-01-01

    When an intense laser light is focused in liquid, a hot plasma is produced at the focal spot. The breakdown threshold and the transmittance of sodium choroids solution are observed using excimer laser or YAG laser. The breakdown threshold decreases with increasing NaCl concentration. Threshold intensity of plasma produced by YAG laser is lower than excimer laser. The behavior of plasma development is observed by a streak camera. The plasma produced by a YAG laser develops only backward. However, the plasma produced by excimer laser develops not only backward but also forward same as the plasma development in high-pressure gases

  11. Transitions in Structure in Oil-in-Water Emulsions As Studied by Diffusing Wave Spectroscopy

    NARCIS (Netherlands)

    Ruis, H.G.M.; Gruijthuijsen, van K.; Venema, P.; Linden, van der E.

    2007-01-01

    Transitions in structure of sodium caseinate stabilized emulsions were studied using conventional rheometry as well as diffusing wave spectroscopy (DWS). Structural differences were induced by different amounts of stabilizer, and transitions in structure were induced by acidification. Special

  12. System Operations Studies for Automated Guideway Transit Systems : Discrete Event Simulation Model Programmer's Manual

    Science.gov (United States)

    1982-07-01

    In order to examine specific automated guideway transit (AGT) developments and concepts, UMTA undertook a program of studies and technology investigations called Automated Guideway Transit Technology (AGTT) Program. The objectives of one segment of t...

  13. Study of liquid deposition during laser printing of liquids

    Energy Technology Data Exchange (ETDEWEB)

    Duocastella, M.; Patrascioiu, A. [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain); Dinca, V. [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain); National Institute for Lasers, Plasma and Radiation Physics, Atomistilor No. 409, PO Box MG 16, 077125 Bucharest (Romania); Fernandez-Pradas, J.M.; Morenza, J.L. [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain); Serra, P., E-mail: pserra@ub.edu [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain)

    2011-04-01

    Laser-induced forward transfer (LIFT) is a direct-writing technique which can be used to successfully print various complex and sensitive materials with a high degree of spatial resolution. However, the optimization of its performances requires a deep understanding of the LIFT dynamics. Such understanding should allow correlating the phenomena underlying the liquid transfer process with the morphology of the obtained deposits. To this end, in this work it is presented a study related to two aspects: first, the correlation of the morphological characteristics of the transferred droplets with the variation of the film thickness combined with laser fluence; and second, a correlation of the dependences observed with the dynamics of the transfer process. The work is focused on the understanding of the observed dependences for which the information provided by time-resolved analysis on liquid transfer dynamics has proved to be crucial.

  14. Study of liquid deposition during laser printing of liquids

    International Nuclear Information System (INIS)

    Duocastella, M.; Patrascioiu, A.; Dinca, V.; Fernandez-Pradas, J.M.; Morenza, J.L.; Serra, P.

    2011-01-01

    Laser-induced forward transfer (LIFT) is a direct-writing technique which can be used to successfully print various complex and sensitive materials with a high degree of spatial resolution. However, the optimization of its performances requires a deep understanding of the LIFT dynamics. Such understanding should allow correlating the phenomena underlying the liquid transfer process with the morphology of the obtained deposits. To this end, in this work it is presented a study related to two aspects: first, the correlation of the morphological characteristics of the transferred droplets with the variation of the film thickness combined with laser fluence; and second, a correlation of the dependences observed with the dynamics of the transfer process. The work is focused on the understanding of the observed dependences for which the information provided by time-resolved analysis on liquid transfer dynamics has proved to be crucial.

  15. Comparative study of the synthesis of layered transition metal molybdates

    International Nuclear Information System (INIS)

    Mitchell, S.; Gomez-Aviles, A.; Gardner, C.; Jones, W.

    2010-01-01

    Mixed metal oxides (MMOs) prepared by the mild thermal decomposition of layered double hydroxides (LDHs) differ in their reactivity on exposure to aqueous molybdate containing solutions. In this study, we investigate the reactivity of some T-Al containing MMOs (T=Co, Ni, Cu or Zn) towards the formation of layered transition metal molybdates (LTMs) possessing the general formula AT 2 (OH)(MoO 4 ) 2 .H 2 O, where A=NH 4 + , Na + or K + . The phase selectivity of the reaction was studied with respect to the source of molybdate, the ratio of T to Mo and the reaction pH. LTMs were obtained on reaction of Cu-Al and Zn-Al containing MMOs with aqueous solutions of ammonium heptamolybdate. Rehydration of these oxides in the presence of sodium or potassium molybdate yielded a rehydrated LDH phase as the only crystalline product. The LTM products obtained by the rehydration of MMO precursors were compared with LTMs prepared by direct precipitation from the metal salts in order to study the influence of preparative route on their chemical and physical properties. Differences were noted in the composition, morphology and thermal properties of the resulting products. - Graphical abstract: Mixed metal oxides (MMOs) derived from layered double hydroxide precursors differ in their reactivity on exposure to aqueous molybdate containing solutions. We investigate the influence of the molybdate source, the rehydration pH and the ratio of T/Mo on the reactivity of some T-Al containing MMOs (T=Co, Ni, Cu or Zn) towards the formation of layered transition metal molybdates of general formula AT 2 (OH)(MoO 4 ) 2 .H 2 O (where A + =NH 4 + , K + or Na + ).

  16. Transition radiation electron beam diagnostic study at ATF

    International Nuclear Information System (INIS)

    Qiu, X.Z.; Wang, X.J.; Batchelor, K.; Ben-Zvi, I.

    1995-01-01

    Recently we have started a program to develop transition radiation based electron beam diagnostics at the Accelerator Test Facility at Brookhaven National Laboratory. In this paper, we will discuss a technique to estimate the lower limit in electron beam divergence measurement with single foil transition radiation and two-foil transition radiation interferometer. Preliminary experimental data from 4.5 MeV electron beam will be presented

  17. Treatment of Dentine Hypersensitivity by Diode Laser: A Clinical Study

    Directory of Open Access Journals (Sweden)

    Romeo Umberto

    2012-01-01

    Full Text Available Introduction. Dentine hypersensitivity (DH is characterized by pain after stimuli that usually provoke no symptoms. This study compared the effectiveness of GaAlAs diode laser alone and with topical sodium fluoride gel (NaF. Materials and Methods. The study was conducted on 10 patients (8 F/2 M, age 25–60 and 115 teeth with DH assessed by air and tactile stimuli measured by Numeric Rating Scale (NRS. Teeth were randomly divided into G1 (34 teeth treated by 1.25% NaF; G2 (33 teeth lased at 0.5 W PW (T on 100 m and T off 100 ms, fluence 62.2 J/cm2 in defocused mode with a 320 μ fiber. Each tooth received three 1′ applications; G3 (48 teeth received NaF gel plus laser at same G2 parameters. NRS was checked at each control. Results. Significant pain reduction was showed. The NRS reduction percentages were calculated, and there was a concrete decrease of DH above all in G3 than G2 and G1. Conclusion. Diode laser is a useful device for DH treatment if used alone and mainly if used with NaF gel.

  18. Transition and Students with Mild Intellectual Disability: Findings From the National Longitudinal Transition Study-2

    Science.gov (United States)

    Bouck, Emily C.; Joshi, Gauri S.

    2016-01-01

    Students with intellectual disability historically struggle with post-school outcomes. However, much of the research on students with intellectual disability relative to post-school outcomes and transition services is aggregated for students with mild, moderate, and severe intellectual disability. This secondary analysis of the National…

  19. A study on laser welding deformation of 304 stainless steel

    International Nuclear Information System (INIS)

    Kitagawa, Akikazu; Maehara, Kenji; Takeda, Shinnosuke; Matsunawa, Akira

    2002-01-01

    In heavy industries, 304 austenitic stainless steel is the most popular material which is used for nuclear equipment, chemical vessels, vacuum vessels and so on. On the fabrication, not only a joint quality but also severe dimensional accuracy is required. To keep dimensional accuracy, considerable cost and efforts are requested, because the welding deformation of austenitic stainless steel is deeply depended on the physical properties of material itself. To decrease welding deformation, big jigs or water cooling method are commonly used which lead to the high cost. In general, the fusion welding by high energy density heat source results in less distortion. Today, laser welding technology has grown up to the stage that enables to weld thick plate with small deformation. The researches of welding deformation have been conducted intensively, but they are mainly concerned for arc welding, and studies for laser welding are very few. In this report, the authors will show the test results of deformation behavior in laser welding of 304 stainless steel. Also, they will discuss the deformation behavior comparing to that in arc welding. The main results of this study are as follows. 1. The angular distortion of laser welding can be unified by heat input parameter (Hp) which is used for arc welding deformation. 2. The angular distortion are same under the condition of Hp 3 in spite of different welding method, however under the condition of Hp>6-9 J/mm 3 the angular distortion is quite different depending on the power density of welding method. 3. Pure angular distortion seemed to complete just after welding, but following longitudinal distortion took place for long period. 4. The critical value of longitudinal distortion can be estimated from heat input parameter. The transverse deformation can be also estimated by heat input parameter. (author)

  20. Study of titania nanorod films deposited by matrix-assisted pulsed laser evaporation as a function of laser fluence

    Science.gov (United States)

    Caricato, A. P.; Belviso, M. R.; Catalano, M.; Cesaria, M.; Cozzoli, P. D.; Luches, A.; Manera, M. G.; Martino, M.; Rella, R.; Taurino, A.

    2011-11-01

    Chemically synthesized brookite titanium dioxide (TiO2) nanorods with average diameter and length dimensions of 3-4 nm and 35-50 nm, respectively, were deposited by the matrix-assisted pulsed laser evaporation technique. A toluene nanorod solution was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser ( λ=248 nm, τ=20 ns) at the repetition rate of 10 Hz, at different fluences (25 to 350 mJ/cm2). The deposited films were structurally characterized by high-resolution scanning and transmission electron microscopy. single-crystal Si wafers and carbon-coated Cu grids were used as substrates. Structural analyses evidenced the occurrence of brookite-phase crystalline nanospheres coexisting with individually distinguishable TiO2 nanorods in the films deposited at fluences varying from 50 to 350 mJ/cm2. Nanostructured TiO2 films comprising only nanorods were deposited by lowering the laser fluence to 25 mJ/cm2. The observed shape and phase transitions of the nanorods are discussed taking into account the laser-induced heating effects, reduced melting temperature and size-dependent thermodynamic stability of nanoscale TiO2.

  1. Laser assisted bioprinting using a femtosecond laser with and without a gold transductive layer: a parametric study

    Science.gov (United States)

    Desrus, H.; Chassagne, B.; Catros, S.; Artiges, C.; Devillard, R.; Petit, S.; Deloison, F.; Fricain, J. C.; Guillemot, F.; Kling, R.

    2016-03-01

    Experimental results of femtosecond Laser Assisted Bioprinting (LAB) are reported on. Two set-up, used to print different model bioinks and keratinocytes cells line HaCaT, were studied: first one was using a femtosecond laser with low pulse energy and an absorbing gold layer, whereas the second one used high pulse energy enabling the removal of the absorbing layer. Printed drop diameter and resulting height of the bioink jet are then quantified as a function of the LAB parameters such as laser energy, focus spot location or numerical aperture.

  2. Density functional theory studies of transition metal nanoparticles in catalysis

    DEFF Research Database (Denmark)

    Greeley, Jeffrey Philip; Rankin, Rees; Zeng, Zhenhua

    2013-01-01

    Periodic Density Functional Theory calculations are capable of providing powerful insights into the structural, energetics, and electronic phenomena that underlie heterogeneous catalysis on transition metal nanoparticles. Such calculations are now routinely applied to single crystal metal surfaces...... and to subnanometer metal clusters. Descriptions of catalysis on truly nanosized structures, however, are generally not as well developed. In this talk, I will illustrate different approaches to analyzing nanocatalytic phenomena with DFT calculations. I will describe case studies from heterogeneous catalysis...... and electrocatalysis, in which single crystal models are combined with Wulff construction-based ideas to produce descriptions of average nanocatalyst behavior. Then, I will proceed to describe explicitly DFT-based descriptions of catalysis on truly nanosized particles (

  3. Aging studies for the ATLAS Transition Radiation Tracker (TRT)

    CERN Document Server

    Åkesson, T; Bondarenko, V; Capéans-Garrido, M; Catinaccio, A; Cwetanski, Peter; Danielsson, H; Dittus, F; Dolgoshein, B A; Dressnandt, N; Ebenstein, W L; Eerola, Paule Anna Mari; Farthouat, Philippe; Fedin, O; Froidevaux, D; Gavrilenko, I; Grichkevitch, Y; Gagnon, P; Hajduk, Z; Keener, P T; Kekelidze, G D; Konovalov, S; Kowalski, T; Kramarenko, V A; Laritchev, A; Lichard, P; Lundberg, B; Luehring, F C; Markina, I; Manara, A; McFarlane, K; Mitsou, V; Muraviev, S; Newcomer, F M; Ogren, H; Oh, S H; Olszowska, J; Peshekhonov, V D; Rembser, C; Romaniouk, A; Rhone, O; Rust, D R; Shchegelskii, V; Shmeleva, A; Smirnov, S; Smirnova, L N; Sosnovtsev, V V; Sutchkov, S; Tartarelli, F; Tikhomirov, V; Van Berg, R; Vassilieva, L; Wang, C; Williams, H H

    2003-01-01

    A summary of the aging and material validation studies carried out for the ATLAS Transition Radiation Tracker (TRT) is presented. Particular emphasis is put on the different phenomena observed in straw tubes operating with the chosen Xe/CF//4/CO//2 mixture. The most serious effects observed are silicon deposition on the anode wire and damage of the anode wire gold plating. Etching phenomena and active radical effects are also discussed. With a careful choice of all materials and components, and with good control of the water contamination in the active gas, the ATLAS TRT will operate reliably for 10 years at the LHC design luminosity. To demonstrate this fully, more work is still needed on the gas system purification elements, in particular to understand their interplay with the active species containing fluorine created in the avalanche process under irradiation.

  4. A Study of Radiative Bottomonium Transitions using Converted Photons

    International Nuclear Information System (INIS)

    Lees, J.P.

    2011-01-01

    The authors use (111 ± 1) million Υ(3S) and (89 ± 1) million Υ(2S) events recorded by the BABAR detector at the PEP-II B-factory at SLAC to perform a study of radiative transitions betwen bottomonium states using photons that have been converted to e + e - pairs by the detector material. They observe Υ(3S) → γχ b0,2 (1P) decay, make precise measurements of the branching fractions for χ b1,2 (1P, 2P) → γΥ(1S) and χ b1,2 (2P) → γΥ(2S) decays, and search for radiative decay to the η b (1S) and η b (2S) states.

  5. Parametric Study and Multi-Criteria Optimization in Laser Cladding by a High Power Direct Diode Laser

    Science.gov (United States)

    Farahmand, Parisa; Kovacevic, Radovan

    2014-12-01

    In laser cladding, the performance of the deposited layers subjected to severe working conditions (e.g., wear and high temperature conditions) depends on the mechanical properties, the metallurgical bond to the substrate, and the percentage of dilution. The clad geometry and mechanical characteristics of the deposited layer are influenced greatly by the type of laser used as a heat source and process parameters used. Nowadays, the quality of fabricated coating by laser cladding and the efficiency of this process has improved thanks to the development of high-power diode lasers, with power up to 10 kW. In this study, the laser cladding by a high power direct diode laser (HPDDL) as a new heat source in laser cladding was investigated in detail. The high alloy tool steel material (AISI H13) as feedstock was deposited on mild steel (ASTM A36) by a HPDDL up to 8kW laser and with new design lateral feeding nozzle. The influences of the main process parameters (laser power, powder flow rate, and scanning speed) on the clad-bead geometry (specifically layer height and depth of the heat affected zone), and clad microhardness were studied. Multiple regression analysis was used to develop the analytical models for desired output properties according to input process parameters. The Analysis of Variance was applied to check the accuracy of the developed models. The response surface methodology (RSM) and desirability function were used for multi-criteria optimization of the cladding process. In order to investigate the effect of process parameters on the molten pool evolution, in-situ monitoring was utilized. Finally, the validation results for optimized process conditions show the predicted results were in a good agreement with measured values. The multi-criteria optimization makes it possible to acquire an efficient process for a combination of clad geometrical and mechanical characteristics control.

  6. GreenLight laser vs diode laser vaporization of the prostate: 3-year results of a prospective nonrandomized study.

    Science.gov (United States)

    Guo, Sanwei; Müller, Georg; Bonkat, Gernot; Püschel, Heike; Gasser, Thomas; Bachmann, Alexander; Rieken, Malte

    2015-04-01

    Laser vaporization of the prostate is one of the alternatives to transurethral resection of the prostate. Short-term studies report a comparable outcome after laser vaporization with the 532 nm 120-W GreenLight high-performance system (HPS) laser and the 980 nm 200 W high-intensity diode (diode) laser. In this study, we analyzed the intermediate-term results of both techniques. From January 2007 to January 2008, 112 consecutive patients with symptomatic benign prostate enlargement were nonrandomly assigned to treatment with the GreenLight laser or the diode laser. Perioperative parameters, postoperative functional outcome, complications, and the reoperation rate at 3 years were analyzed. Improvement of voiding symptoms (International Prostate Symptom Score, quality-of-life) and micturition parameters (maximum flow rate, postvoid residual volume) showed no significant difference between the HPS group and the diode group. A significantly higher reoperation rate was observed in the diode group in comparison to the HPS group (37.5% vs 8.9%, p=0.0003) due to obstructive necrotic tissue (16.1% vs 0%, p=0.0018), bladder neck stricture (16.1% vs 1.8%, p=0.008), and persisting or recurrent adenoma (5.4% vs 7.1%, p=0.70), respectively. Both lasers lead to comparable improvement of voiding parameters and micturition symptoms. Treatment with the 200 W diode laser led to a significantly higher reoperation rate, which might be attributed to a higher degree of coagulation necrosis. Thus, a careful clinical application of this diode laser type is warranted.

  7. A high-repetition rate LWFA for studies of laser propagation and electron generation

    Science.gov (United States)

    He, Zhaohan; Easter, James; Hou, Bixue; Krushelnick, Karl; Nees, John; Thomas, Alec

    2010-11-01

    Advances in ultrafast optics today have enabled laser systems to deliver ever shorter and more intense pulses. When focused, such laser pulses can easily exceed relativistic intensities where the wakefield created by the strong laser electric field can be used to accelerate electrons. Laser wakefield acceleration of electrons holds promise for future compact electron accelerators or drivers of other radiation sources in many scientific, medical and engineering applications. We present experimental studies of laser wakefield acceleration using the λ-cubed laser at the University of Michigan -- a table-top high-power laser system operating at 500 Hz repetition rate. The high repetition rate allows statistical studies of laser propagation and electron acceleration which are not accessible with typical sub-0.1 Hz repetition rate systems. In addition, we compare the experiments with particle-in-cell simulations using the code OSIRIS.

  8. A real-time Raman spectroscopy study of the dynamics of laser-thinning of MoS2 flakes to monolayers

    Science.gov (United States)

    Gu, Enyao; Wang, Qiyuan; Zhang, Youwei; Cong, Chunxiao; Hu, Laigui; Tian, Pengfei; Liu, Ran; Zhang, Shi-Li; Qiu, Zhi-Jun

    2017-12-01

    Transition metal dichalcogenides (TMDCs) in monolayer form have attracted a great deal of attention for electronic and optical applications. Compared to mechanical exfoliation and chemical synthesis, laser thinning is a novel and unique "on-demand" approach to fabricate monolayers or pattern desired shapes with high controllability and reproducibility. Its successful demonstration motivates a further exploration of the dynamic behaviour of this local thinning process. Here, we present an in-situ study of void formation by laser irradiation with the assistance of temporal Raman evolution. In the analysis of time-dependent Raman intensity, an empirical formula relating void size to laser power and exposure time is established. Void in thinner MoS2 flakes grows faster than in thicker ones as a result of reduced sublimation temperature in the two-dimensional (2D) materials. Our study provides useful insights into the laser-thinning dynamics of 2D TMDCs and guidelines for an effective control over the void formation.

  9. Studies on the influence of laser beams on wound granulation

    International Nuclear Information System (INIS)

    Brunner, R.

    1982-01-01

    The influence of laser light of law energy on wound healing was tested on 204 rats in a blind study. The growth of granulation tissue in a polyvinylchloride cylinder implanted on the backs of the animals served as parameter for wound healing. Irradiation was carried out with a helium-neon laser (wavelength 632.8 nm) at daily doses of 0.5 J/cm 2 , 1.5 J/cm 2 , 4 J/cm 2 , 10 J/cm 2 and 20 J/cm 2 , and with incoherent non-linear polarized red light (wavelength 630 nm) with a daily dose of 4 J/cm 2 . This was repeated 8 times. Laser irradiation caused a statistically significant increase in wet and dry granulation tissue weight of 25% in the dose range 1.5 J/cm 2 to 20 J/cm 2 . At 0.5 J/cm 2 the effect was less, but the least effect was achieved by non-linear polarized incoherent red light. Bacteriological evaluation of wound germ counts revealed a marginally lower presence of high germ cell densities. In irradiated animals, histological and enzyme cytochemical findings revealed, in addition to a significant findings revealed, in addition to a significant increase in mast cells, a smaller increase in fibroblast count and a slight decrease in granulocytic and histiocytic elements. The biochemical evaluation of granulation tissue revealed no differences in collagen content between irradiated and unirradiated animals. (orig.) [de

  10. Semiconductor laser joint study program with Rome Laboratory

    Science.gov (United States)

    Schaff, William J.; Okeefe, Sean S.; Eastman, Lester F.

    1994-09-01

    A program to jointly study vertical-cavity surface emitting lasers (VCSEL) for high speed vertical optical interconnects (VOI) has been conducted under an ES&E between Rome Laboratory and Cornell University. Lasers were designed, grown, and fabricated at Cornell University. A VCSEL measurement laboratory has been designed, built, and utilized at Rome Laboratory. High quality VCSEL material was grown and characterized by fabricating conventional lateral cavity lasers that emitted at the design wavelength of 1.04 microns. The VCSEL's emit at 1.06 microns. Threshold currents of 16 mA at 4.8 volts were obtained for 30 microns diameter devices. Output powers of 5 mW were measured. This is 500 times higher power than from the light emitting diodes employed previously for vertical optical interconnects. A new form of compositional grading using a cosinusoidal function has been developed and is very successful for reducing diode series resistance for high speed interconnection applications. A flip-chip diamond package compatible with high speed operation of 16 VCSEL elements has been designed and characterized. A flip-chip device binding effort at Rome Laboratory was also designed and initiated. This report presents details of the one-year effort, including process recipes and results.

  11. Some neutron scattering studies on magnetic and molecular phase transitions

    International Nuclear Information System (INIS)

    Bevaart, L.

    1978-01-01

    In this thesis neutron-scattering investigations on two different systems are described. The first study is concerned with the magnetic ordering phenomena in pseudo two-dimensional (d = 2), two-component antiferromagnets K 2 Mnsub(1-x)Msub(x)F 4 (M = Fe, Co), as a function of the composition x and temperature T. For one of the samples in this series, K 2 Musub(0.978)Fesub(0.022)F 4 , the influence of an external magnetic field on the ordering characteristics was studied in addition. The second study deals with the rotational motions of the NH 4 + groups in NH 4 ZnF 3 in relation with the structural phase transition at Tsub(c) = 115.1 K. The experimental techniques were chosen according to the requirements of each of these two subjects. The former study was carried out by observing the elastic magnetic neutron scattering with a double-axis diffractometer, whereas for the latter study time-of-flight (TOF) techniques were applied to observe the inelastic and quasi-elastic incoherent neutron scattering by the protons of the rotating NH 4 + groups. (Auth.)

  12. Study on microstructure and high temperature wear resistance of laser cladded nuclear valve clack

    International Nuclear Information System (INIS)

    Zhang Chunliang; Chen Zichen

    2002-01-01

    Laser cladding of Co-base alloy on the nuclear valve-sealing surface are performed with a 5 kW CO 2 transverse flowing laser. The microstructure and the high temperature impact-slide wear resistance of the laser cladded coating and the plasma cladded coating are studied. The results show that the microstructure, the dilution rate and the high temperature impact-slide wear resistance of the laser cladded coating have obvious advantages over the spurt cladding processing

  13. Conformational reduction of DOPA in the gas phase studied by laser desorption supersonic jet laser spectroscopy.

    Science.gov (United States)

    Ishiuchi, Shun-ichi; Mitsuda, Haruhiko; Asakawa, Toshiro; Miyazaki, Mitsuhiko; Fujii, Masaaki

    2011-05-07

    The conformational reduction in catecholamine neurotransmitters was studied by resonance enhanced multi photon ionization (REMPI), ultraviolet-ultraviolet (UV-UV) hole burning and infrared (IR) dip spectroscopy with applying a laser desorption supersonic jet technique to DOPA, which is one of the catecholamine neurotransmitters and has one more phenolic OH group than tyrosine. It is concluded that DOPA has a single observable conformer in the gas phase at low temperature. Quantum chemical calculations at several levels with or without the dispersion correction were also carried out to study stable conformations. From the comparison between the computational IR spectra and the experimental ones, the most stable structure was determined. It is strongly suggested that the conformational reduction is caused by electrostatic interactions, such as a dipole-dipole interaction, between the chain and OH groups. This journal is © the Owner Societies 2011

  14. Small laser spot versus standard laser spot photodynamic therapy for idiopathic choroidal neovascularization: a randomized controlled study.

    Science.gov (United States)

    Li, Xiao-xin; Tao, Yong

    2012-12-01

    Idiopathic choroidal neovascularization (ICNV) affects young patients and thus may have a significant impact on vision and life quality over a patient's lifespan. This study was designed to compare the visual outcome and retinal pigment epithelium (RPE) damage after photodynamic therapy (PDT) with small laser spot and PDT with standard laser spot for idiopathic choroidal neovascularization (ICNV). This was a randomized controlled study. Fifty-two patients with ICNV were enrolled and randomly divided into a study group (small laser spot PDT, n = 27) and a control group (standard laser spot PDT, n = 25). Best corrected visual acuity (BCVA), optic coherence tomography (OCT) and fluorescein angiography (FA) findings were the main measurements. The patients were followed up 1 week, 1, 3, 6, 9 months and 1 year after PDT. BCVA improvement was statistically significantly higher in the study group than the control group at 6-month ((25.53 ± 15.01) letters vs. (14.71 ± 11.66) letters, P = 0.025) and 9-month follow-ups ((27.53 ± 17.78) letters vs. (15.59 ± 12.21) letters, P = 0.039). At 3- and 6-month follow-ups, the quadrants of RPE damage between the two groups varied significantly (P laser spot PDT group than in the standard laser spot PDT group for ICNV.

  15. Theoretical studies of atomic transitions: Progress report, March 15, 1985-March 14, 1988

    International Nuclear Information System (INIS)

    Froese Fischer, C.

    1987-09-01

    Allowed and forbidden transitions have been studied for a number of atomic systems of interest in astrophysics, laser physics, or fusion research. All calculations have been based on the multiconfiguration Hartree-Fock (MCHF) method extended to include relativistic corrections in the Breit-Pauli approximation. The computer codes for this atomic structure software package were transferred to the CRAY supercomputer and modified for more convenient computation. Techniques were developed to enhance the range of problems considered, by either increasing the accuracy of prediction or increasing the complexity of problems considered. An example is the prediction of a bound state for Ca - for which experimental evidence was inconclusive. Several different types of problems have been considered. A study of energy levels and lifetimes of a Rydberg series can given insight into electronic structure and explain deviations from regular behavior, and a number of such studies were performed. With the MCHF + Breit-Pauli approach it has been possible to determine a large portion of a spectrum. In core excited quartets of Na, autoionization along spin-orbit mixing and term dependence were all important in predicting lifetimes in excellent agreement with the most recent experiments. Some photoionization studies were performed which, like autoionization require the calculation of continuum functions. Finally, an attempt was made to combine the MCHF method with many-body perturbation theory so as to build on the strengths of both. 13 refs., 2 figs., 3 tabs

  16. Stable isotopes of transition and post-transition metals as tracers in environmental studies

    Science.gov (United States)

    Bullen, Tomas D.; Baskaran, Mark

    2011-01-01

    The transition and post-transition metals, which include the elements in Groups 3–12 of the Periodic Table, have a broad range of geological and biological roles as well as industrial applications and thus are widespread in the environment. Interdisciplinary research over the past decade has resulted in a broad understanding of the isotope systematics of this important group of elements and revealed largely unexpected variability in isotope composition for natural materials. Significant kinetic and equilibrium isotope fractionation has been observed for redox sensitive metals such as iron, chromium, copper, molybdenum and mercury, and for metals that are not redox sensitive in nature such as cadmium and zinc. In the environmental sciences, the isotopes are increasingly being used to understand important issues such as tracing of metal contaminant sources and fates, unraveling metal redox cycles, deciphering metal nutrient pathways and cycles, and developing isotope biosignatures that can indicate the role of biological activity in ancient and modern planetary systems.

  17. Study on gamma-ray transitions induced in nuclear spin isomers by X-rays

    International Nuclear Information System (INIS)

    Yang Tianli; Hao Fanhua; Liu Xiaoya; Gong Jian

    2005-10-01

    The development of induced X-ray has been summarized for high spin isomer. the radiation model, transition mechanism and experiment plan have been introduced. The experiments about isomers 180m Ta and 178m2 Hf have been narrated in detail respectively, and the analysis between those results have been obtained. The reasonable theoretical frame and good experimental data have offered the powerful technique base for pumping γ-ray laser with low energy. (authors)

  18. STUDIES ON WETTABILITY OF STAINLESS STEEL 316L POWDER IN LASER MELTING PROCESS

    Directory of Open Access Journals (Sweden)

    KURIAN ANTONY

    2014-10-01

    Full Text Available Laser sintering is one of the techniques used in additive manufacturing processes. The main objective of the work is to study the effects of process parameters on wetting phenomenon and interfacial energy during laser melting of stainless steel powder. This paper reports wetting of laser melted powder particles and its use for the determination of surface energy of stainless steel powder under laser beam exposure. Process parameters such as laser power, scan speed and beam diameter are considered for study. This study also identifies the process parameters for better wettability which produces smooth surfaces.

  19. The simultaneous measurements of core and outer core density fluctuations in L-H transition using CO2 laser collective scattering diagnostic in the EAST superconducting tokamak

    International Nuclear Information System (INIS)

    Cao, G.M.; Li, Y.D.; Zhang, X.D.; Sun, P.J.; Hu, L.Q.; Li, J.G.; Wu, G.J.

    2013-01-01

    The H-mode is the projected basic operation scenario for the ITER tokamak. The turbulence de-correlation by the synergistic effect of zonal flow and equilibrium ExB flow shear is believed to be the reason for L-H transition, however, the detailed physical mechanism has not been identified so far. Tangential multi-channel CO 2 laser collective scattering diagnostic system (mainly k r measurement) was first installed to investigate electron density fluctuations on EAST tokamak. The measurements in a spontaneous dithering L-H transition show that in core plasma (0 < r/a < 0.5) the low-frequency fluctuations strengthen greatly before L-H transition; meanwhile in outer core plasma (0.2 < r/a < 1) the low-frequency fluctuations strengthen slightly. Bispectral analysis reveals that the coupling strength between low- and high-frequency fluctuations in both core and outer core plasma strengthens greatly before the transition, but the latter is greater than the former. The results indicate that the low-frequency fluctuations of the core and outer core plasma play active, but different, roles in the spontaneous L-H transition. (author)

  20. University Transitions and Gender: From Choice of Studies to Academic Career Development

    Science.gov (United States)

    Villar, Alícia; Hernàndez, Francesc Jesús

    2014-01-01

    Based on the results of the authors' research using a case study of a Spanish university, the sociological component of gender is an important factor in building transitions at university. When the authors refer to university transitions they are talking about two periods. Firstly, they refer to the transition of undergraduate students from upper…

  1. Experimental studies of the laser-controlled collective ion accelerator

    International Nuclear Information System (INIS)

    Destler, W.W.; Rodgers, J.; Segalov, Z.

    1989-01-01

    Detailed experimental studies of a collective acceleration experiment in which a time-sequenced laser-generated ionization channel is used to control the propagation of an intense relativistic electron beamfront are presented. Ions trapped in the potential well at the beamfront are accelerated as the velocity of the beamfront is increased in a manner controlled by the time-dependent axial extent of the ionization channel. Beamfront propagation data for two different accelerating gradients are presented, together with results of ion acceleration studies for both gradients

  2. Optical frequency measurements of 6s 2S1/2-6p 2P3/2 transition in a 133Cs atomic beam using a femtosecond laser frequency comb

    International Nuclear Information System (INIS)

    Gerginov, V.; Tanner, C.E.; Diddams, S.; Bartels, A.; Hollberg, L.

    2004-01-01

    Optical frequencies of the hyperfine components of the D 2 line in 133 Cs are determined using high-resolution spectroscopy and a femtosecond laser frequency comb. A narrow-linewidth probe laser excites the 6s 2 S 1/2 (F=3,4)→6p 2 P 3/2 (F=2,3,4,5) transition in a highly collimated atomic beam. Fluorescence spectra are taken by scanning the laser frequency over the excited-state hyperfine structure. The laser optical frequency is referenced to a Cs fountain clock via a reference laser and a femtosecond laser frequency comb. A retroreflected laser beam is used to estimate and minimize the Doppler shift due to misalignment between the probe laser and the atomic beam. We achieve an angular resolution on the order of 5x10 -6 rad. The final uncertainties (∼±5 kHz) in the frequencies of the optical transitions are a factor of 20 better than previous results [T. Udem et al., Phys. Rev. A 62, 031801 (2000).]. We find the centroid of the 6s 2 S 1/2 →6p 2 P 3/2 transition to be f D2 =351 725 718.4744(51) MHz

  3. Study in molecular lasers. Final report, 1 November 1980-30 April 1984

    Energy Technology Data Exchange (ETDEWEB)

    Burns, G; Kutz, H D; Cohen, L K; Billard, T C

    1984-10-01

    A sensitive LIF system was constructed, using a Nd:YAG plus dye laser. The signal was accumulated and analyzed by employing a Tektronix R7912 transient Digitizer and a PDP-11 minicomputer. Reactivity of HF (v=5) was studied. Using the same equipment, a time-delayed photoemission from a trialkali photosensitive semiconductor was observed. Using 3-D trajectory calculations a new computational observable, the relative nonequilibrium distribution (RNED) function at the steady state was determined for the Br + Ar reaction at 3500K. It is characterized by one adjustable parameter equal to 12, while the transition state theory prescribes that it should be infinitely large. RNED will be used to test and refine modern theories of reaction kinetics.

  4. Composite population kernels in ytterbium-buffer collisions studied by means of laser-saturated absorption

    International Nuclear Information System (INIS)

    Zhu, X.

    1986-01-01

    We present a systematic study of composite population kernels for 174 Yb collisions with He, Ar, and Xe buffer gases, using laser-saturation spectroscopy. 174 Yb is chosen as the active species because of the simple structure of its 1 S 0 - 3 P 1 resonance transition (lambda = 556 nm). Elastic collisions are modeled by means of a composite collision kernel, an expression of which is explicitly derived based on arguments of a hard-sphere potential and two-category collisions. The corresponding coupled population-rate equations are solved by iteration to obtain an expression for the saturated-absorption line shape. This expression is fit to the data to obtain information about the composite kernel, along with reasonable values for other parameters. The results confirm that a composite kernel is more general and realistic than a single-component kernel, and the generality in principle and the practical necessity of the former are discussed

  5. Effects of an Intense Laser Field and Hydrostatic Pressure on the Intersubband Transitions and Binding Energy of Shallow Donor Impurities in a Quantum Well

    International Nuclear Information System (INIS)

    Yesilgul, U.; Ungan, F.; Kasapoglu, E.; Sari, H.; Sökmen, I.

    2011-01-01

    We have calculated the intersubband transitions and the ground-state binding energies of a hydrogenic donor impurity in a quantum well in the presence of a high-frequency laser field and hydrostatic pressure. The calculations are performed within the effective mass approximation, using a variational method. We conclude that the laser field amplitude and the hydrostatic pressure provide an important effect on the electronic and optical properties of the quantum wells. According to the results obtained from the present work, it is deduced that (i) the binding energies of donor impurity decrease as the laser field increase, (ii) the binding energies of donor impurity increase as the hydrostatic pressure increase, (iii) the intersubband absorption coefficients shift toward lower energies as the hydrostatic pressure increases, (iv) the magnitude of absorption coefficients decrease and also shift toward higher energies as the laser field increase. It is hopeful that the obtained results will provide important improvements in device applications. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  6. Atomic frequency reference at 1033 nm for ytterbium (Yb)-doped fiber lasers and applications exploiting a rubidium (Rb) 5S_1/2 to 4D_5/2 one-colour two-photon transition

    Science.gov (United States)

    Roy, Ritayan; Condylis, Paul C.; Johnathan, Yik Jinen; Hessmo, Björn

    2017-04-01

    We demonstrate a two-photon transition of rubidium (Rb) atoms from the ground state (5$S_{1/2}$) to the excited state (4$D_{5/2}$), using a home-built ytterbium (Yb)-doped fiber amplifier at 1033 nm. This is the first demonstration of an atomic frequency reference at 1033 nm as well as of a one-colour two-photon transition for the above energy levels. A simple optical setup is presented for the two-photon transition fluorescence spectroscopy, which is useful for frequency stabilization for a broad class of lasers. This spectroscopy has potential applications in the fiber laser industry as a frequency reference, particularly for the Yb-doped fiber lasers. This two-photon transition also has applications in atomic physics as a background- free high- resolution atom detection and for quantum communication, which is outlined in this article.

  7. Comparative study of the synthesis of layered transition metal molybdates

    Science.gov (United States)

    Mitchell, S.; Gómez-Avilés, A.; Gardner, C.; Jones, W.

    2010-01-01

    Mixed metal oxides (MMOs) prepared by the mild thermal decomposition of layered double hydroxides (LDHs) differ in their reactivity on exposure to aqueous molybdate containing solutions. In this study, we investigate the reactivity of some T-Al containing MMOs ( T=Co, Ni, Cu or Zn) towards the formation of layered transition metal molybdates (LTMs) possessing the general formula AT2(OH)(MoO 4) 2·H 2O, where A=NH 4+, Na + or K +. The phase selectivity of the reaction was studied with respect to the source of molybdate, the ratio of T to Mo and the reaction pH. LTMs were obtained on reaction of Cu-Al and Zn-Al containing MMOs with aqueous solutions of ammonium heptamolybdate. Rehydration of these oxides in the presence of sodium or potassium molybdate yielded a rehydrated LDH phase as the only crystalline product. The LTM products obtained by the rehydration of MMO precursors were compared with LTMs prepared by direct precipitation from the metal salts in order to study the influence of preparative route on their chemical and physical properties. Differences were noted in the composition, morphology and thermal properties of the resulting products.

  8. 926 nm laser operation in Nd:GdNbO4 crystal based on 4F3/2 → 4I9/2 transition

    Science.gov (United States)

    Yan, Renpeng; Li, Xudong; Yao, Wenming; Shen, Yingjie; Zhou, Zhongxiang; Peng, Fang; Zhang, Qingli; Dou, Renqing; Gao, Jing

    2018-05-01

    926 nm laser operation in a Nd:GdNbO4 crystal based on quasi-three-level 4F3/2 → 4I9/2 transition is reported, for the first time to our best knowledge. An average output power of 393 mW at 926 nm under 879 nm LD pumping is obtained with a slope efficiency of 33.3% and an optical-to-optical efficiency of 26.0%. The slope efficiency with respect to absorbed pump power is estimated to be 47.7%. Comparison between output characters of 926 nm laser under direct and indirect pumping is conducted. The average output power at 926 nm under 808 nm LD pumping reaches 305 mW with an optical-to-optical efficiency of 16.1%.

  9. Use of a 3-MV proton accelerator for study of noble gases, including laser ionization of excited states

    International Nuclear Information System (INIS)

    Hurst, G.S.; Judish, J.P.; Nayfeh, M.H.; Parks, J.E.; Payne, M.G.; Wagner, E.B.

    1974-01-01

    The use of a pulsed 3-MV accelerator to study energy pathways in the noble gases is described. The objectives of pathways research are to obtain (1) information on the spectrum of excited states produced by a charged particle in a noble gas, (2) the rate of decay of the various states through various channels as a function of gas pressure, and (3) the modification of the decay channels due to the introduction of foreign species. A new energy pathways model is presented for helium as a general illustration. A method for the study of excited states, using a laser ionization technique is reported. Use is made of a laser which is tuned to a resonance transition between the desired excited state and some higher excited state. Photons in the same pulse photoionize the higher excited state; thus the ionization current vs photon wavelength has a resonance structure. Absolute yields of selected excited states can be obtained whenever the photon fluence per pulse is large enough to saturate the ionization current. A general summary is given of experimental facilities which include a 3-MV Van de Graaff accelerator, electronics for measuring radiation lifetimes, vacuum ultraviolet spectrometers, and a pulsed laser facility for direct study of excited states. Finally, the relevance of pathways research to (1) the interaction of radiation with matter, (2) the development of gas lasers, and (3) methods of ultrasensitive elemental analysis is pointed out

  10. Light-scattering study of the glass transition in lubricants

    Science.gov (United States)

    Alsaad, M. A.; Winer, W. O.; Medina, F. D.; Oshea, D. C.

    1977-01-01

    The sound velocity of four lubricants has been measured as a function of temperature and pressure using Brillouin scattering. A change in slope of the velocity as a function of temperature or pressure allowed the determination of the glass transition temperature and pressure. The glass transition data were used to construct a phase diagram for each lubricant. The data indicate that the glass transition temperature increased with pressure at a rate which ranged from 120 to 200 C/GPa. The maximum pressure attained was 0.69 GPa and the temperature range was from 25 to 100 C.

  11. Gendered transitions to adulthood by college field of study in the United States

    OpenAIRE

    Siqi Han; Dmitry Tumin; Zhenchao Qian

    2016-01-01

    Background: Field of study may influence the timing of transitions to the labor market, marriage, and parenthood among college graduates. Research to date has yet to study how field of study is associated with the interweaving of these transitions in the USA. Objective: The current study examines gendered influences of college field of study on transitions to a series of adult roles, including full-time work, marriage, and parenthood. Methods: We use Cox proportional hazards models and ...

  12. Recent aging studies for the ATLAS transition radiation tracker

    CERN Document Server

    Capéans-Garrido, M; Anghinolfi, F; Arik, E; Baker, O K; Baron, S; Benjamin, D; Bertelsen, H; Bondarenko, V; Bychkov, V; Callahan, J; Cardiel-Sas, L; Catinaccio, A; Cetin, S A; Cwetanski, Peter; Dam, M; Danielsson, H; Dittus, F; Dologshein, B; Dressnandt, N; Driouichi, C; Ebenstein, W L; Eerola, Paule Anna Mari; Farthouat, Philippe; Fedin, O; Froidevaux, D; Gagnon, P; Grichkevitch, Y; Grigalashvili, N S; Hajduk, Z; Hansen, P; Kayumov, F; Keener, P T; Kekelidze, G D; Khristatchev, A; Konovalov, S; Koudine, L; Kovalenko, S; Kowalski, T; Kramarenko, V A; Krüger, K; Laritchev, A; Lichard, P; Luehring, F C; Lundberg, B; Maleev, V; Markina, I; McFarlane, K W; Mialkovski, V; Mindur, B; Mitsou, V A; Morozov, S; Munar, A; Muraviev, S; Nadtochy, A; Newcorner, F M; Ogren, H; Oh, S H; Olszowska, J; Passmore, S; Patritchev, S; Peshekhonov, V D; Petti, R; Price, M; Rembser, C; Rohne, O; Romaniouk, A; Rust, D R; Ryabov, Yu; Ryzhov, V; Shchegelskii, V; Seliverstov, D M; Shin, T; Shmeleva, A; Smirnov, S; Sosnovtsev, V V; Soutchkov, V; Spiridenkov, E; Szczygiel, R; Tikhomirov, V; Van Berg, R; Vassilakopoulos, V I; Vassilieva, L; Wang, C; Williams, H H; Zalite, A

    2004-01-01

    The transition radiation tracker (TRT) is one of the three subsystems of the inner detector of the ATLAS experiment. It is designed to operate for 10 yr at the LHC, with integrated charges of similar to 10 C/cm of wire and radiation doses of about 10 Mrad and 2 multiplied by 10**1**4 neutrons/cm**2. These doses translate into unprecedented ionization currents and integrated charges for a large-scale gaseous detector. This paper describes studies leading to the adoption of a new ionization gas regime for the ATLAS TRT. In this new regime, the primary gas mixture is 70%Xe-27%CO**2-3%O**2. It is planned to occasionally flush and operate the TRT detector with an Ar-based ternary mixture, containing a small percentage of CF**4, to remove, if needed, silicon pollution from the anode wires. This procedure has been validated in realistic conditions and would require a few days of dedicated operation. This paper covers both performance and aging studies with the new TRT gas mixture. 12 Refs.

  13. Study of inverse methods in remote sensing with laser

    International Nuclear Information System (INIS)

    Jesus, Wellington Carlos de

    2009-01-01

    The Laboratory of Environmental Applications of Lasers at IPEN realizes a study about atmospherics properties, such as extinction and backscattering coefficient. These coefficient are estimated by an inverse method, whose estimate quality is difficult to measure. This work presents a method with good statistic approach to retrieval the same coefficients. The new method, however, offers a number of advantages compared to the first method in use, including (1) the ability to incorporate different kinds of information under a common retrieval philosophy and (2) the method provides number of ways for evaluating the quality of the retrieval. Thus we hope improve the accuracy of estimates. (author)

  14. Facial recognition and laser surface scan: a pilot study

    DEFF Research Database (Denmark)

    Lynnerup, Niels; Clausen, Maja-Lisa; Kristoffersen, Agnethe May

    2009-01-01

    Surface scanning of the face of a suspect is presented as a way to better match the facial features with those of a perpetrator from CCTV footage. We performed a simple pilot study where we obtained facial surface scans of volunteers and then in blind trials tried to match these scans with 2D...... photographs of the faces of the volunteers. Fifteen male volunteers were surface scanned using a Polhemus FastSCAN Cobra Handheld Laser Scanner. Three photographs were taken of each volunteer's face in full frontal, profile and from above at an angle of 45 degrees and also 45 degrees laterally. Via special...

  15. Study of laser monitoring techniques of pollutants in atmosphere

    International Nuclear Information System (INIS)

    Hassan, T. A. A.

    2006-01-01

    There are several techniques used as a tool for monitoring the pollutions in the atmosphere, where the laser radiation sending through the sample of atmosphere to be investigated ether transmission or the scattering of the light, all the way through a variety of different techniques for monitoring the air quality. We are showed in this study the comparison of detection techniques through measuring the light scattered in some particular direction, rather than measuring direction the attenuation due to two type of scattering (Rayieh scattering and Mie scattering) during (optical Radar, Roman backscattering and Resonance fluorescence).(Author)

  16. Moessbauer study of phase transitions under high hydrostatic pressures. 1

    International Nuclear Information System (INIS)

    Kapitanov, E.V.; Yakovlev, E.N.

    1979-01-01

    Experimental results of the hydrostatic pressure influence on Moessbauer spectrum parameters are obtained over the pressure range including the area of structural phase transition. A linear increase of the Moessbauer effect probability (recoilless fraction) is accompanied by a linear decrease of the electron density at tin nuclei within the pressure range foregoing the phase transition. The electric resistance and the recoilless fraction of the new phase of Mg 2 Sn are lower, but the electron density at tin nuclei is greater than the initial phase ones. Hydrostatic conditions allow to fix clearly the diphasic transition area and to determine the influence of the pressure on the Moessbauer line position and on the recoilless fraction of the high pressure phase. The phase transition heat Q = 415 cal mol -1 is calculated using recoilless fractions of the high and low pressure phases at 25 kbar. The present results are qualitatively and quantitatively different from the results, obtained at nonhydrostatic conditions. (author)

  17. Advanced diagnostics for laser plasma interaction studies and some recent experiments

    International Nuclear Information System (INIS)

    Chaurasia, S.; Munda, D.S.; Dhareshwar, L.J.

    2008-10-01

    The complete characterization of Laser plasma interaction studies related to inertial confinement fusion laser and Equation of state (EOS) studies needs many diagnostics to explain the several physical phenomena occurring simultaneously in the laser produced plasma. This involves many on ion emission are important to understand physical phenomena which are responsible for generation of laser plasma as well as its interaction with an intense laser. In this report we describe the development of various x-ray diagnostics which are used in determining temporal, spatial and spectral properties of x-rays radiated from laser produced plasma. Diagnostics which have been used in experiments for investigation of laser-produced plasma as a source of ions are also described. Techniques using an optical streak camera and VISAR which are being used in the Equation of States (EOS) studies of various materials, which are important for material science, astrophysics as well as ICF is described in details. (author)

  18. Improvement of the superconducting transition and demagnetization factor in YBa2Cu3O7-δ single crystals by laser cutting

    International Nuclear Information System (INIS)

    Bhattacharya, A.; Grupp, D.E.; Goldman, A.M.; Welp, U.

    1996-01-01

    Single crystals of YBa 2 Cu 3 O 7-δ have been cut into disc shapes using an excimer laser. The bulk superconducting transition was found to be sharpened in all cases measured. This is associated with the removal of material at the edges which may be depleted of oxygen or otherwise damaged. The magneto-optical images for one crystal have been correlated with the optical image. The angular dependence of the demagnetizing factor for field applied in the plane was drastically reduced in disc-shaped crystals relative to rectangular ones. The field of first flux entry was also increased. copyright 1996 American Institute of Physics

  19. Generation of second-harmonic radiations of a self-focusing laser from a plasma with density-transition

    International Nuclear Information System (INIS)

    Kant, Niti; Gupta, Devki Nandan; Suk, Hyyong

    2011-01-01

    A Gaussian laser-beam resonantly generates a second-harmonic wave in a plasma in the presence of a wiggler magnetic-field of suitable period. The self-focusing of the fundamental pulse enhances the intensity of the second-harmonic pulse. An introduction of an upward plasma-density ramp strongly enhances the self-focusing of the fundamental laser pulse. The laser pulse attains a minimum spot size and propagates up to several Rayleigh lengths without divergence. Due to the strong self-focusing of the fundamental laser pulse, the second-harmonic intensity enhances significantly. A considerable enhancement of the intensity of the second-harmonic is observed from the proposed mechanism. -- Highlights: → An upward plasma-density ramp is very important for laser propagation in plasmas. → As the plasma density increases, effect of self-focusing becomes stronger. → We utilize this self-focused laser to generate second-harmonic radiations. → The self-focusing laser enhances the intensity of the second-harmonic pulse.

  20. Generation of second-harmonic radiations of a self-focusing laser from a plasma with density-transition

    Energy Technology Data Exchange (ETDEWEB)

    Kant, Niti [Department of Physics, Lovely Professional University, Phagwara 144 402, Punjab (India); Gupta, Devki Nandan, E-mail: dngupta@physics.du.ac.in [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Suk, Hyyong [Advanced Photonics Research Institute (APRI) and Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

    2011-08-15

    A Gaussian laser-beam resonantly generates a second-harmonic wave in a plasma in the presence of a wiggler magnetic-field of suitable period. The self-focusing of the fundamental pulse enhances the intensity of the second-harmonic pulse. An introduction of an upward plasma-density ramp strongly enhances the self-focusing of the fundamental laser pulse. The laser pulse attains a minimum spot size and propagates up to several Rayleigh lengths without divergence. Due to the strong self-focusing of the fundamental laser pulse, the second-harmonic intensity enhances significantly. A considerable enhancement of the intensity of the second-harmonic is observed from the proposed mechanism. -- Highlights: → An upward plasma-density ramp is very important for laser propagation in plasmas. → As the plasma density increases, effect of self-focusing becomes stronger. → We utilize this self-focused laser to generate second-harmonic radiations. → The self-focusing laser enhances the intensity of the second-harmonic pulse.

  1. Studies on laser-assisted Penning ionization by the optogalvanic effect in Ne/Eu hollow cathode discharge.

    Science.gov (United States)

    Saini, V K; Kumar, P; Dixit, S K; Nakhe, S V

    2015-02-01

    Laser-assisted Penning ionization (LAPI) is detected in a Ne/Eu hollow cathode (HC) discharge lamp using the pulsed optogalvanic (OG) method. In the Ne/Eu discharge, doubly ionized europium excited energy levels Eu[4f(7)(P(7/2,5/2)6)] lie within the thermal limit (∼kT) from the laser-excited neon's energy level [2p(5)(P3/202)3p or 2p(8) (in Paschen notation)] lying at 149,848  cm(-1). Therefore, Penning ionization (PI) of europium atoms likely to occur into its highly excited ionic states is investigated. To probe the PI of europium, the temporal profiles of its counterpart neon OG signal are studied as a function of discharge current for the transitions (1s(4)→2p(8)) and (1s(2)→2p(2)), corresponding to 650.65 and 659.89 nm wavelengths, respectively. It is observed that PI of europium alters the overall discharge characteristics significantly and, hence, modifies the temporal profile of the OG signals accordingly. The quasi-resonant ionizing energy transfer collisions between laser-excited Ne 2p(8) atoms and electronically excited europium P(9/2)10 atoms are used to explain the LAPI mechanism. Such LAPI studies carried out in HC discharge could be useful for the discharge of a metal-vapor laser with appropriate Penning mixtures.

  2. Comparative Study of Diode Laser Versus Neodymium-Yttrium Aluminum: Garnet Laser Versus Intense Pulsed Light for the Treatment of Hirsutism.

    Science.gov (United States)

    Puri, Neerja

    2015-01-01

    Lasers are widely used for the treatment of hirsutism. But the choice of the right laser for the right skin type is very important. Before starting with laser therapy, it is important to assess the skin type, the fluence, the pulse duration and the type of laser to be used. To compare the efficacy and side effects of Diode laser, Neodymium-yttrium aluminum - garnet (Nd: YAG) laser and intense pulsed light (IPL) on 30 female patients of hirsutism. Thirty female patients with hirsutism were selected for a randomised controlled study. The patients were divided into three groups of 10 patients each. In group I patients diode laser was used, in group II patients long pulsed Nd: YAG laser was used and in group III, IPL was used. The patients were evaluated and result graded according to a 4-point scale as excellent, >75% reduction; good, 50-75% reduction; fair; 25-50% reduction; and poor, diode laser group, followed by 35% hair reduction in the Nd: Yag laser group and 10% hair reduction in the IPL group. The percentage of hair reduction after four sessions of treatment was maximum (64%) in the diode laser group, followed by 62% hair reduction in the Nd: Yag laser group and 48% hair reduction in the IPL group. The percentage of hair reduction after eight sessions of treatment was maximum (92%) in the diode laser group, followed by 90% hair reduction in the Nd: YAG group and 70% hair reduction in the IPL group. To conclude for the Indian skin with dark hairs, the diode laser still stands the test of time. But, since the diode laser has a narrow margin of safety, proper pre and post-procedure cooling is recommended. Although, the side effects of Nd: YAG laser are less as compared to the diode laser, it is less efficacious as compared to the diode laser.

  3. Raman microspectrometry of laser-reshaped rabbit auricular cartilage: preliminary study on laser-induced cartilage mineralization

    Science.gov (United States)

    Heger, Michal; Mordon, Serge R.; Leroy, Gérard; Fleurisse, Laurence; Creusy, Collette

    2006-03-01

    Laser-assisted cartilage reshaping (LACR) is a relatively novel technique designed to noninvasively and permanently restructure cartilaginous tissue. It is believed that heat-induced stress relaxation, in which a temperature-mediated disruption of H2O binding is associated with conformational alterations in the proteoglycan and collagen-rich matrix, constitutes the underlying mechanism of LACR. Several reports have suggested that laser-mediated cartilage mineralization may contribute to the permanent shape change of laser-reshaped cartilage. In an effort to validate these results in the context of Er:glass LACR, we performed a preliminary Raman microspectrometric study to characterize the crystal deposits in laser-irradiated chondrocytes and extracellular matrix. For the first time, we identified intracellular calcium sulfate deposits and extracellular calcium phosphate (apatite) crystals in laser-reshaped rabbit auricular cartilage. Calcium carbonate deposits are localized in both irradiated and nonirradiated samples, suggesting that this mineral plays no role in conformational retention. In our discussion, we elaborate on the possible molecular and cellular mechanisms responsible for intra- and extracellular crystallization, and propose a novel hypothesis on the formation of apatite, inasmuch as the biological function of this mineral (providing structure and rigidity in bones and dental enamel) may be extrapolated to the permanent shape change of laser-irradiated cartilage.

  4. Comparative in vitro study of tissue welding using a 808 nm diode laser and a Ho:YAG laser.

    Science.gov (United States)

    Ott, B; Züger, B J; Erni, D; Banic, A; Schaffner, T; Weber, H P; Frenz, M

    2001-01-01

    In vitro porcine arteries and veins have been welded end-to-end using either a 808 nm diode laser combined with an indocyanine green enhanced albumin solder, or with a continuous-wave (cw) Ho:YAG laser without biological solder. The vascular stumps were approached to each other over a coronary dilatation catheter in order to obtain a precise alignment and good coaptation. Standard histology revealed for both welding techniques lateral tissue damage between 2 and 3 mm caused by laser-induced heat. Good solder attachment to the tissue was observed by the use of a scanning electron microscope. The vessels soldered with the 808 nm diode laser using albumin solder showed considerably higher tensile strength (1 N compared to 0.3 N) than vessels welded exclusively by Ho:YAG laser radiation. In contrast, leaking pressure (350 +/- 200 mmHg) and bursting pressure (457 +/- 200 mmHg) were found to be independent of the welding technique used. This study demonstrates that fast (total welding time about 2-5 min), stable and tight microvascular anastomosis can be achieved with the use of a dye-enhanced albumin laser soldering technique and an ancillary coronary dilatation catheter.

  5. A comparative study of pulsed dye laser versus long pulsed Nd:YAG laser treatment in recalcitrant viral warts.

    Science.gov (United States)

    Shin, Yo Sup; Cho, Eun Byul; Park, Eun Joo; Kim, Kwang Ho; Kim, Kwang Joong

    2017-08-01

    Viral warts are common infectious skin disease induced by human papillomavirus (HPV). But the treatment of recalcitrant warts is still challenging. In this study, we compared the effectiveness of pulsed dye laser (PDL) and long pulsed Nd:YAG (LPNY) laser in the treatment of recalcitrant viral warts. We retrospectively analyzed the medical records of patients with recalcitrant warts treated with laser therapy between January 2013 and February 2016. Seventy-two patients with recalcitrant warts were evaluated. Thirty-nine patients were treated with pulsed dye laser and thirty-three patients were treated with LPNY laser. The following parameters were used: PDL (spot size, 7 mm; pulse duration, 1.5 ms; and fluence, 10-14 J/cm 2 ) and LPNY (spot size, 5 mm; pulse duration, 20 ms; and fluence, 240-300 J/cm 2 ). Complete clearance of two patients (5.1%) in PDL group, and three patients (9.1%) in LPNY group were observed without significant side effects. The patients who achieved at least 50% improvement from baseline were 20 (51.3%) in PDL and 22 (66.7%) in LPNY, respectively. This research is meaningful because we compared the effectiveness of the PDL and LPNY in the recalcitrant warts. Both PDL and LPNY laser could be used as a safe and alternative treatment for recalcitrant warts.

  6. Observation and investigation of narrow optical transitions of 167Er3+ ions in femtosecond laser printed waveguides in 7LiYF4 crystal

    Science.gov (United States)

    Minnegaliev, M. M.; Dyakonov, I. V.; Gerasimov, K. I.; Kalinkin, A. A.; Kulik, S. P.; Moiseev, S. A.; Saygin, M. Yu; Urmancheev, R. V.

    2018-04-01

    We produced optical waveguides in the 167Er3+:7 LiYF4 crystal with diameters ranging from 30 to 100 μm by using the depressed-cladding approach with femtosecond laser. Stationary and coherent spectroscopy was performed on the 809 nm optical transitions between the hyperfine sublevels of 4I15/2 and 4I9/2 multiplets of 167Er3+ ions both inside and outside of waveguides. It was found that the spectra of 167Er3+ were slightly broadened and shifted inside the waveguides compared to the bulk crystal spectra. We managed to observe a two-pulse photon echo on this transition and determined phase relaxation times for each waveguide. The experimental results show that the created crystal waveguides doped by rare-earth ions can be used in optical quantum memory and integrated quantum schemes.

  7. Application of adjustable pulse lasers to studying rapid reaction kinetics of excited lanthanide complexing

    Energy Technology Data Exchange (ETDEWEB)

    Gruzdev, V.P. (Gosudarstvennyj Opticheskij Inst., Leningrad (USSR))

    1983-12-01

    Using some europium (3) ion complexes new possibilities to be opened by application of adjustable pulse lasers for studying rapid reactions of electron-excited metal ion complexing are demonstrated. The 6Zh rhodamine pulse laser is used as a source of nonequilibrium photoexcitation of an array of Eu/sup 3 +/ complexes in the luminescent kinetic spectroscopy method. The following results are obtained: for the first time the rate of reaction of acetate ion substitution for water molecules of an excited (/sup 5/D/sub 0/) ion of Eu/sup 3 +/ was measured to be (0.7+-0.2)x10/sup 7/ s/sup -1/; using direct experiments the lower limit for the rate of transition of one isomeric form of the excited Eu x EDTA complex into another one in an aqueous solution is determined to be 5x10/sup 5/ s/sup -1/ at 295 K; the kinetics of the excitation energy migration beteen aqueous solvates of Eu/sup 3 +/ and EuxEDTA complexes is investigated.

  8. Laser Spectroscopy Study on the Neutron-Rich and Neutron-Deficient Te Isotopes

    CERN Multimedia

    2002-01-01

    We propose to perform laser spectroscopy measurements on the Te isotopes. This will give access to fundamental properties of the ground and rather long-lived isomeric states such as the change in the mean square charge radius ($\\delta\\langle$r$^2_c\\rangle$) and the nuclear moments. For these medium-mass isotopes, at this moment the optical resolution obtained with RILIS is not high enough to perform isotope shift measurements. Thus we will use the COMPLIS experimental setup which allows Resonant Ionization Spectroscopy (RIS) on laser desorbed atoms. The 5p$^{4}$ $^{3}$P$_{2} \\rightarrow$ 5p$^{3}$ 6s $^{3}$S$_{1}$ and 5p$^{4}$ $^{3}$P$_{2} \\rightarrow$ 5p$^{3}$ 6s $^{5}$S$_{2}$ optical transitions have been used to perform, on the stable Te isotopes, the tests required by the INTC committee. For this purpose stable-ion sources have been built and Te isotopes have been delivered as stable beams by the injector coupled to the COMPLIS setup. ISOLDE offers the opportunity for studying the Te isotope series over a ...

  9. Study on Effectiveness of the chaos laser radar

    OpenAIRE

    成田, 義之; 津田, 紀生; 山田, 諄

    2003-01-01

    A laser is widely applied for measurements, since it is invented. There are two types of laser distance meter for short and long distance. For long distance, a laser radar using propagation time of laser light is used. Generally, a distance is measured from delay time using either a periodic signal or a single pulse. But the signal becomes to be buried in noise with increasing distance. A new type of chaos laser radar which processes by only an addition is proposed. This radar can quickly pro...

  10. Study of Electric Monopole Transitions in $^{76,78}$Kr

    CERN Multimedia

    2002-01-01

    In the run at ISOLDE performed last August we completed the study of the decay properties of the $ 0 ^{+} _{2} $ level in $ ^{76, 78, 80}$Kr by measuring the lifetime of the $ 0 ^{+} _{2} $ level in $^{76}$Kr. This was done by applying the $\\beta \\gamma\\gamma$ (t) fast timing method to the $\\beta^{+} $-decay of $^{76}$Rb. For the first time the method was applied to proton-rich nuclei at ISOLDE. This required some special modifications of the experimental set-up previously used for the case of $\\beta^{-}$-decay due to the presence of intense annihilation radiation. The experiment has been successful and enough data have been collected for the determination of the lifetime. The analysis is in progress. From a very preliminary estimate it would appear that the lifetime value falls in the range 20-60 ps. Combining this value with the previously measured ratio \\[\\frac{B(E0; 0^{+}_{2} \\rightarrow 0^{+}_{1})}{B(E2; 0^{+}_{2} \\rightarrow 2^{+}_{1})}\\] It is possible to extract an estimate of the monopole transition...

  11. Study on effective laser cleaning method to remove carbon layer from a gold surface

    International Nuclear Information System (INIS)

    Singh, Amol; Modi, Mohammed H; Lodha, G S; Choubey, A K; Upadhyaya, B N

    2013-01-01

    Hydrocarbon cracking and carbon contamination is a common problem in soft x-ray Synchrotron Radiation (SR) beamlines. Carbon contamination on optics is known to absorb and scatter radiation close to the C K-edge (284 eV) spectral region. The purpose of this work is to study and develop a laser cleaning method that can effectively remove the carbon contaminations without damaging the underneath gold-coated optics. The laser cleaning process is a non-contact, accurate, efficient and safe. Nd:YAG laser of 100 ns pulse duration is used for carbon cleaning. The effect of laser pulse duration, laser fluence, number of laser passes, angle of incidence and spot overlapping on the cleaning performance is studied. Cleaning effect and subsequent film quality after laser irradiation is analyzed using x-ray photoelectron spectroscopy (XPS) and soft x-ray reflectivity (SXR) techniques.

  12. Femtosecond study of laser dyes soluble in water: coumarins

    International Nuclear Information System (INIS)

    Cassara, Laurence

    1996-01-01

    Coumarins build up one of the great families of laser dyes, and this research thesis addresses the study of four water-soluble coumarins (ATC, DMATC, DATC, and CHOS) which are analogue to conventional coumarins (C120, C311, C1, and C102). These molecules are made water-soluble by substitution of the methyl group in position 4 by a polyether group. Mechanisms of deactivation are studied by means of time-resolved fluorescence and transient adsorption methods which allow the reaction dynamics of coumarins after light excitation to be studied. Several time scales, from femto- to nano-second, have been reached and allowed various processes to be studied: relaxation, solvation dynamics, solute orientation diffusion, process of deactivation of radiative and non-radiative relaxation in various solvents [fr

  13. Equation of state study of Laser Megajoule capsules ablator materials

    International Nuclear Information System (INIS)

    Colin-Lalu, Pierre

    2016-01-01

    This PhD thesis enters the field of inertial confinement fusion studies. In particular, it focuses on the equation of state tables of ablator materials synthesized on LMJ capsules. This work is indeed aims at improving the theoretical models introduced into the equation of state tables. We focused in the Mbar-eV pressure-temperature range because it can be access on kJ-scale laser facilities.In order to achieve this, we used the QEOS model, which is simple to use, configurable, and easily modifiable.First, quantum molecular dynamics (QMD) simulations were performed to generate cold compression curve as well as shock compression curves along the principal Hugoniot. Simulations were compared to QEOS model and showed that atomic bond dissociation has an effect on the compressibility. Results from these simulations are then used to parametrize the Grueneisen parameter in order to generate a tabulated equation of state that includes dissociation. It allowed us to show its influence on shock timing in a hydrodynamic simulation.Second, thermodynamic states along the Hugoniot were measured during three experimental campaigns upon the LULI2000 and GEKKO XII laser facilities. Experimental data confirm QMD simulations.This study was performed on two ablator materials which are an undoped polymer CHO, and a silicon-doped polymer CHOSi. Results showed universal shock compression properties. (author) [fr

  14. The transition radiation. 2. experimental study of the optical transition radiation

    International Nuclear Information System (INIS)

    Couillaud, Ch.; Haouat, G.; Seguin, S.; Striby, S.

    1999-01-01

    Optical-transition-radiation-based diagnostics have been widely used for many years on electron accelerators in order to measure beam energy and transverse and longitudinal emittances. These diagnostics are very attractive for high brightness electron beams used as drivers for radiation sources. Such diagnostics have been performed on the ELSA facility (18 MeV electron energy, 100 A peak current) using both a single interface and an OTR-Wartski interferometer. We present the accelerator, the experimental set-up and the method for analyzing the OTR angular distribution. Then, the experimental results are described and compared with those from the three gradient method. In addition, we present a beam energy measurement using OTR interferogram analysis. (author)

  15. Classical and quantum mechanical studies of HF in an intense laser field

    International Nuclear Information System (INIS)

    Dardi, P.S.; Gray, S.K.

    1982-01-01

    The behavior of an HF molecule in an intense laser field is investigated with both classical trajectories and quantum dynamics. Vibration-rotation transition probabilities and energy absorption as a function of laser pulse time are calculated for the diatomic initially in its ground state. For comparison, results are also reported for a model nonrotating HF molecule. It is found that classical mechanics does not predict the correct time behavior of the system, nor does it predict the correct rotational state distributions. Classical mechanics does, however, predict pulse time averaged quantities to be the correct order of magnitude. There is also a correct general trend of increased multiphoton excitation for laser frequencies red-shifted from the one-photon resonance, although multiphoton resonance peaks are not observed in the classical results and far too little multiphoton excitation is predicted. The effect of laser phase has also been investigated and shown to be relatively unimportant in both the classical and quantum dynamics

  16. THE HOMOGENEOUS STUDY OF TRANSITING SYSTEMS (HoSTS). I. THE PILOT STUDY OF WASP-13

    Energy Technology Data Exchange (ETDEWEB)

    Gomez Maqueo Chew, Yilen; Cargile, Phillip; Hebb, Leslie; Stassun, Keivan G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Faedi, Francesca; Pollacco, Don [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Doyle, Amanda P.; Smalley, Barry [Astrophysics Group, Keele University, Staffordshire ST5 5BG (United Kingdom); Ghezzi, Luan; Cunha, Katia; Smith, Verne V. [Observatorio Nacional, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Sousa, Sergio; Santos, Nuno C. [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Barros, Susana C. C. [LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, Aix Marseille Universite, CNRS, F-13388 Marseille (France); Schuler, Simon C. [Stewart Observatory, University of Arizona, Tucson, AZ 85721 (United States); Collier Cameron, Andrew, E-mail: yilen.gomez@vanderbilt.edu [School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom)

    2013-05-01

    We present the fundamental stellar and planetary properties of the transiting planetary system WASP-13 within the framework of the Homogeneous Study of Transiting Systems (HoSTS). HoSTS aims to derive the fundamental stellar (T{sub eff}, [Fe/H], M{sub *}, R{sub *}) and planetary (M{sub pl}, R{sub pl}, T{sub eq}) physical properties of known transiting planets using a consistent methodology and homogeneous high-quality data set. Four spectral analysis techniques are independently applied to a Keck+HIRES spectrum of WASP-13 considering two distinct cases: unconstrained parameters and constrained log g from transit light curves. We check the derived stellar temperature against that from a different temperature diagnostic based on an INT+IDS H{alpha} spectrum. The four unconstrained analyses render results that are in good agreement, and provide an improvement of 50% in the precision of T{sub eff}, and of 85% in [Fe/H] with respect to the WASP-13 discovery paper. The planetary parameters are then derived via the Monte Carlo Markov Chain modeling of the radial velocity and light curves, in iteration with stellar evolutionary models to derive realistic uncertainties. WASP-13 (1.187 {+-} 0.065 M{sub Sun }; 1.574 {+-} 0.048 R{sub Sun }) hosts a Saturn-mass, transiting planet (0.500 {+-} 0.037 M{sub Jup}; 1.407 {+-} 0.052 R{sub Jup}), and is at the end of its main-sequence lifetime (4-5.5 Gyr). Our analysis of WASP-13 showcases that both a detailed stellar characterization and transit modeling are necessary to well determine the fundamental properties of planetary systems, which are paramount in identifying and determining empirical relationships between transiting planets and their hosts.

  17. TOPEM DSC study of glass transition region of polyurethane cationomers

    International Nuclear Information System (INIS)

    Pielichowska, Kinga; Król, Piotr; Król, Bożena; Pagacz, Joanna

    2012-01-01

    Highlights: ► TOPEM DSC method was employed to investigate the glass transition (T g ) region of fluorinated polyurethane cationomers. ► Introduction of fluorine compounds significantly changes thermal behaviour of cationomers in the T g region of hard segments. ► Introduction of fluorine compound leads to changes of the slope in activation diagram of glass transition. - Abstract: In this paper TOPEM DSC method was employed to investigate the glass transition region of fluorinated polyurethane cationomers. Fluorinated polyurethane cationomers have been synthesised in the reaction of MDI with poly(ethylene glycol) (600) and butane1,4-diol or N-methyl- or N-butyldiethanolamine and 2,2,3,3-tetrafluoro-1,4-butanediol. Better rigidity was found for generally amorphous cationomer coats. It was found that introduction of fluorine compound changes thermal behaviour of polyurethane cationomers as well as leads to changes in the slope in activation diagram profiles of glass transition in comparison to polyuretahene cationomer without fluorine compound. Application of TOPEM DSC allows to obtain more information concerning frequency dependence of glass transition region and thermodynamical stability of polyurethane structures.

  18. A comparative study of modified transcanalicular diode laser dacryocystorhinostomy versus conventional transcanalicular diode laser dacryocystorhinostomy.

    Science.gov (United States)

    Feijó, Eduardo Damous; Caixeta, Juliana Alves; de Souza Nery, Ana Carla; Limongi, Roberto Murillo; Matayoshi, Suzana

    2017-08-01

    External dacryocystorhinostomy (DCR) is the gold standard surgical technique for the treatment of primary acquired nasolacrimal duct obstruction (PANDO). However, new techniques such as endoscopic DCR and transcanalicular dacryocystorhinostomy (T-DCR) are being studied in an attempt to reduce surgical time, avoid external scarring and preserve the lacrimal pump while achieving the same efficacy. The purpose of this study was to compare the efficacy between conventional T-DCR and modified transcanalicular dacryocystorhinostomy (MT-DCR) in patients with PANDO. MT-DCR is performed to remove nasal mucosa prior to laser osteotomy. This is a comparative, prospective, interventionist and randomized study. Patients with PANDO were selected to undergo MT-DCR or T-DCR by blocked randomization. PANDO was diagnosed based on clinical presentation, dye disappearance test and dacryocystography. All of the procedures were performed by the same surgery team members. Anatomical success outcome was defined as positive lacrimal syringing and functional success outcome was defined as the absence or improvement of epiphora. A total of 44 surgical procedures were performed (22 MT-DCR and 22 T-DCR). In the case of MT-DCR, the anatomical and functional success rates after 12 months were 90 and 86%, respectively. After T-DCR, these rates were 77 and 72%, respectively (p = 0.162). MT-DCR and T-DCR are both safe and fast procedures with low morbidity and well-tolerated.

  19. Studies on the optogalvanic effect and isotope-selective excitation of ytterbium in a hollow cathode discharge lamp using a pulsed dye laser.

    Science.gov (United States)

    Kumar, Pankaj; Kumar, Jitendra; Prakash, Om; Saini, Vinod K; Dixit, Sudhir K; Nakhe, Shankar V

    2013-09-01

    This paper presents studies on the pulsed optogalvanic effect and isotope-selective excitation of Yb 555.648 nm (0 cm(-1) → 17 992.007 cm(-1)) and 581.067 nm (17 992.007 cm(-1) → 35 196.98 cm(-1)) transitions, in a Yb/Ne hollow cathode lamp. The Yb atoms were excited by narrow linewidth (500-1000 MHz) Rh110 and Rh6G dye based pulsed lasers. Optogalvanic signal inversion for ground state transition at 555.648 nm was observed beyond a hollow cathode discharge current of 8.5 mA, in contrast to normal optogalvanic signal at 581.067 nm up to maximum current of 14 mA. The isotope-selective excitation studies of Yb were carried out by recording Doppler limited optogalvanic signals as a function of dye laser wavelength. For the 581.067 nm transition, three even isotopes, (172)Yb, (174)Yb, and (176)Yb, and one odd isotope, (171)Yb, were clearly resolved. These data were compared with selective isotope excitation by 10 MHz linewidth continuous-wave dye laser. For 555.648 nm transition, isotopes were not clearly resolved, although isotope peaks of low modulation were observed.

  20. Q-values of mirror transitions for fundamental interaction studies

    CERN Multimedia

    The $Ft$ values for the $0^{+} \\rightarrow 0^{+}$ superallowed $\\beta$-transitions currently provide the best test of the CVC hypothesis, and the most precise determination of the V$_{ud}$ element of the CKM matrix. Recent experimental advances, including direct mass measurements with Penning traps, have led to the precision in the corrected $Ft$ values being dominated by the theoretical corrections rather than experiment. An alternative route are the isospin $T$=1/2 mirror transitions where experimental uncertainties dominate over the theoretical inputs and which can provide an independent test of CVC, and ultimately an independent evaluation of V$_{ud}$. We propose mass measurements of 4 different mirror transitions aiming for a precision of better than 100eV on the ${Q}$-values.

  1. The transition radiation. 2. experimental study of the optical transition radiation; Le rayonnement de transition: 2. etude experimentale du rayonnement de transition optique

    Energy Technology Data Exchange (ETDEWEB)

    Couillaud, Ch.; Haouat, G.; Seguin, S.; Striby, S

    1999-07-01

    Optical-transition-radiation-based diagnostics have been widely used for many years on electron accelerators in order to measure beam energy and transverse and longitudinal emittances. These diagnostics are very attractive for high brightness electron beams used as drivers for radiation sources. Such diagnostics have been performed on the ELSA facility (18 MeV electron energy, 100 A peak current) using both a single interface and an OTR-Wartski interferometer. We present the accelerator, the experimental set-up and the method for analyzing the OTR angular distribution. Then, the experimental results are described and compared with those from the three gradient method. In addition, we present a beam energy measurement using OTR interferogram analysis. (author)

  2. Laser-induced-fluorescence studies of fragment ions: CH+ and CD+

    International Nuclear Information System (INIS)

    O'Keefe, A.

    1981-08-01

    The dynamics of ion-molecule interactions within a mass selective rf quadrupole ion trap are studied for several ion-molecule systems. Laser induced fluorescence is used as a probe of the internal energy distributions of molecular ions under collision free conditions and under controlled collision conditions. The effects of collisions at near thermal energies (0.3 to 0.5 eV) are easily understood in terms of processes such as charge transfer and other energy transfer mechanisms. The A 1 PI - X 1 Σ + system of CH + and CD + has been examined under collision free conditions. The ions were produced from methane through electron impact ionization/dissociation. The observed energy distributions reflect the dynamical partitioning of dissociation exothermicity, excepting short lived electronic states. Many new transitions belonging to this electronic system have been observed and a reliable vibrational frequency for the X 1 Σ + state has been obtained. The radiative lifetimes of CH + and CD + A 1 PI(v = 0) states have been measured and a revised oscillator strength for the A-X transition has been derived from this data

  3. Calorimetric study of water's two glass transitions in the presence of LiCl

    Science.gov (United States)

    Ruiz, Guadalupe N.; Amann-Winkel, Katrin; Bove, Livia E.; Corti, Horacio R.

    2018-01-01

    A DSC study of dilute glassy LiCl aqueous solutions in the water-dominated regime provides direct evidence of a glass-to-liquid transition in expanded high density amorphous (eHDA)-type solutions. Similarly, low density amorphous ice (LDA) exhibits a glass transition prior to crystallization to ice Ic. Both glass transition temperatures are independent of the salt concentration, whereas the magnitude of the heat capacity increase differs. By contrast to pure water, the glass transition endpoint for LDA can be accessed in LiCl aqueous solutions above 0.01 mole fraction. Furthermore, we also reveal the endpoint for HDA's glass transition, solving the question on the width of both glass transitions. This suggests that both equilibrated HDL and LDL can be accessed in dilute LiCl solutions, supporting the liquid–liquid transition scenario to understand water's anomalies. PMID:29442107

  4. Mid-Latitude versus Polar-Latitude Transitional Impact Craters: Geometric Properties from Mars Orbiter Laser Altimeter (MOLA) Observations and Viking Images

    Science.gov (United States)

    Matias, A.; Garvin, J. B.; Sakimoto, S. E. H.

    1998-01-01

    One intriguing aspect of martian impact crater morphology is the change of crater cavity and ejecta characteristics from the mid-latitudes to the polar regions. This is thought to reflect differences in target properties such as an increasing presence of ice in the polar regions. Previous image-based efforts concerning martian crater morphology has documented some aspects of this, but has been hampered by the lack of adequate topography data. Recent Mars Orbiter Laser Altimeter (MOLA) topographic profiles provide a quantitative perspective for interpreting the detailed morphologies of martian crater cavities and ejecta morphology. This study is a preliminary effort to quantify the latitude-dependent differences in morphology with the goal of identifying target-dependent and crater modification effects from the combined of images and MOLA topography. We combine the available MOLA profiles and the corresponding Viking Mars Digital Image Mosaics (MDIMS), and high resolution Viking Orbiter images to focus on two transitional craters; one on the mid-latitudes, and one in the North Polar region. One MOLA pass (MGS Orbit 34) traverses the center of a 15.9 km diameter fresh complex crater located at 12.8degN 83.8degE on the Hesperian ridge plains unit (Hvr). Viking images, as well as MOLA data, show that this crater has well developed wall terraces and a central peak with 429 m of relative relief. Three MOLA passes have been acquired for a second impact crater, which is located at 69.5degN 41degE on the Vastitas Borealis Formation. This fresh rampart crater lacks terraces and central peak structures and it has a depth af 579 m. Correlation between images and MOLA topographic profiles allows us to construct basic facies maps of the craters. Eight main units were identified, four of which are common on both craters.

  5. Studies of the phase transitions in UAs with neutron scattering

    International Nuclear Information System (INIS)

    Sinha, S.K.; Lander, G.H.; Shapiro, S.M.; Vogt, O.

    1980-01-01

    Uranium arsenide is known to order with the type-I antiferromagnetic (AF) structure at approx. 126 K, and exhibit a first-order transition to the type-IA AF structure at T/sub N//2. We have now reexamined these transitions with a single crystal. Above T/sub N/ UAs exhibits critical scattering suggesting a tendency to order with an incommensurate wavevector, but then suddenly orders with the AF-I structure. The analysis of the data shows the need to consider anisotropic exchange interactions of cubic symmetry between U moments

  6. Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers

    OpenAIRE

    Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart

    2011-01-01

    Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influen...

  7. Narrow-linewidth Si/III-V lasers: A study of laser dynamics and nonlinear effects

    Science.gov (United States)

    Vilenchik, Yaakov Yasha

    Narrow-linewidth lasers play an important role in a wide variety of applications, from sensing and spectroscopy to optical communication and on-chip clocks. Current narrow-linewidth systems are usually implemented in doped fibers and are big, expensive, and power-hungry. Semiconductor lasers compete favorably in size, cost, and power consumption, but their linewidth is historically limited to the sub-MHz regime. However, it has been recently demonstrated that a new design paradigm, in which the optical energy is stored away from the active region in a composite high-Q resonator, has the potential to dramatically improve the coherence of the laser. This work explores this design paradigm, as applied on the hybrid Si/III-V platform. It demonstrates a record sub-KHz white-noise-floor linewidth. It further shows, both theoretically and experimentally, that this strategy practically eliminates Henry's linewidth enhancement by positioning a damped relaxation resonance at frequencies as low as 70 MHz, yielding truly quantum limited devices at frequencies of interest. In addition to this empirical contribution, this work explores the limits of performance of this platform. Here, the effect of two-photon-absorption and free-carrier-absorption are analyzed, using modified rate equations and Langevin force approach. The analysis predicts that as the intra-cavity field intensity builds up in the high-Q resonator, non-linear effects cause a new domain of performance-limiting factors. Steady-state behavior, laser dynamics, and frequency noise performance are examined in the context of this unique platform, pointing at the importance of nonlinear effects. This work offers a theoretical model predicting laser performance in light of nonlinear effects, obtaining a good agreement with experimental results from fabricated high-Q Si/III-V lasers. In addition to demonstrating unprecedented semiconductor laser performance, this work establishes a first attempt to predict and demonstrate

  8. Laser Spectroscopy Studies in the Neutron-Rich Sn Region

    CERN Multimedia

    Obert, J

    2002-01-01

    We propose to use the powerful laser spectroscopy method to determine the magnetic moment $\\mu$ and the variation of the mean square charge radius ($\\delta\\,\\langle$r$_{c}^{2}\\,\\rangle$) for ground and long-lived isomeric states of the Sn isotopes from A=125 to the doubly-magic $^{132}$Sn isotope and beyond. For these neutron-rich Sn nuclei, numerous $\\delta\\,\\langle$r$^{2}_{c}\\,\\rangle$ curves have already been calculated and the predictions depend upon the effective interactions used. Therefore, a study of the effect of the shell closure N=82 on the $\\delta\\,\\langle$r$^{2}_{c}\\,\\rangle$ values in the Z=50 magic nuclei is of great interest, especially because $^{132}$Sn is located far from the stability valley. It will help to improve the parameters of the effective interactions and make them more suitable to predict the properties of exotic nuclei. \\\\ \\\\The neutron-rich Sn isotopes produced with an uranium carbide target, are ionized using either a hot plasma ion source or the resonant ionization laser ion ...

  9. Kinetic studies following state-selective laser excitation

    International Nuclear Information System (INIS)

    Keto, J.W.

    1992-01-01

    We have made measurements of state-to-state deactivation cross sections and radiative lifetimes for Xe*(6p,6p',7p) and Kr*(5p) states in xenon and krypton buffer gases. These results are relevant to kinetic models and both excimer lasers and the infrared xenon laser; and they are a significant improvement in the precision of the known radiative lifetimes. This type of experiment can now be compared with recent calculations of state-to-state collisional relaxation in rare-gases by Hickman, Huestis, and Saxon. We have also made significant progress in the study of the electronic spectra of small molecules of the rare gases. Spectra have been obtained for Xe 2 , Xe 3 , Xe 4 , and larger clusters. As guidance for the larger clusters of the rare gases we have obtained the first multiphoton spectra for excitons in condensed xenon. In collaboration with research on the multiphoton spectra of the rare gases, we have continued experiments using synchrotron radiation in collaboration with the University of Hamburg. In experiments there we have observed excitation and fluorescence spectra for single xenon atoms at the surface, within the second layer, and within the bulk of large argon clusters

  10. Cytogenetic studies with laser or X-ray exposures

    International Nuclear Information System (INIS)

    Bozduganov, A.; Genkov, P.

    1975-01-01

    Account is given of studies involving a total of 21 peripheral blood cultures given the following treatments: exposure to 20 0.13-joule pulses from an optic quantum generator (ruby), 9; exposure to 1000 R X-rays, 9; and unexposed controls, 3. Exposures were carried out on three cultures from each experimental series at each of three time intervals, namely 24 h, 48 h, and 72 h after initiation of cultures. On any day, 40 well-spread metaphases were examined. High quality metaphases were photographed and karyotyped in conformity to the Chicago Conference criteria. In the laser experiment, chromosome aberrations were observed in 65% of methaphases analyzed vs. 5.3% in controls. Anomalies encountered included aneuploidy, with hypoploid metaphases predominating, polyploidy (triploidy, tetraploidy, and partial endoreduplication), and structural alterations. The following structural chromosome rearrangements are found: acentric fragments, mostly pairs, occasionally single, including minute chromosomes; dicentric and tricentric chromosomes; interstitial deletions; and chromosome translocations. Most varied and abundant chromosome aberrations were seen in 72-h irradiated cultures. The data presented offer a new opportunity for assessing genetic lesions after laser exposure and may help to determine threshold doses. (author)

  11. Optothermal Switching of Cholesteric Liquid Crystals: A Study of Azobenzene Derivatives and Laser Wavelengths

    Directory of Open Access Journals (Sweden)

    Tai-Chieh Huang

    2015-09-01

    Full Text Available The laser-initiated thermal (optothermal switching of cholesteric liquid crystals (CLCs is characterized by using different azobenzene (Azo derivatives and laser wavelengths. Under 405-nm laser irradiation, Azo-doped CLCs undergo phase transition from cholesteric to isotropic. No cis-to-trans photoisomerization occurs when the 405-nm laser irradiation is blocked because only a single laser is used. The fast response of Azo-doped CLCs under the on–off switching of the 405-nm laser occurs because of the optothermal effect of the system. The 660-nm laser, which cannot be used as irradiation to generate the trans–cis photoisomerization of Azo, is used in Anthraquinone (AQ-Azo-doped CLCs to examine the optothermal effect of doped Azo. The results show that the LC-like Azo derivative bearing two methyl groups ortho to the Azo moiety (A4 can greatly lower the clearing temperature and generate large amount of heat in AQ-A4-doped CLCs.

  12. Quasi-continuous wave and continuous wave laser operation of Eu:KGd(WO4)2 crystal on a 5D0 → 7F4 transition

    International Nuclear Information System (INIS)

    Dashkevich, V I; Orlovich, V A; Bui, A A; Bagayev, S N; Vatnik, S M; Loiko, P A; Yumashev, K V; Kuleshov, N V; Pavlyuk, A A

    2015-01-01

    We report on the first demonstration of quasi-continuous wave (quasi-CW) and real CW room-temperature lasing on the 5 D 0  →  7 F 4 transition of Eu 3+ -doped material using a 25 at.%Eu 3+  : KGd(WO 4 ) 2 crystal pumped into the 7 F 1  →  5 D 1 transition by a diode-end-pumped Nd 3+  : KGd(WO 4 ) 2 /KTP green laser at 533.6 nm. The maximum CW output power of this laser at 702.3 nm is 5.3 mW with 1.4% green-to-red conversion efficiency. In quasi-CW operation mode with a 10% duty cycle, the peak power of ms long pulses reaches ∼54 mW, which corresponds to the optical conversion efficiency of 3.5%. (letter)

  13. The UC{sub 2−x} – Carbon eutectic: A laser heating study

    Energy Technology Data Exchange (ETDEWEB)

    Manara, D., E-mail: dario.manara@ec.europa.eu; Boboridis, K.; Morel, S.; De Bruycker, F.

    2015-11-15

    The UC{sub 2−x} – carbon eutectic has been studied by laser heating and fast multi-wavelength pyrometry under inert atmosphere. The study has been carried out on three compositions, two of which close to the phase boundary of the UC{sub 2−x} – C miscibility gap (with C/U atomic ratios 2 and 2.1), and one, more crucial, with a large excess of carbon (C/U = 2.82). The first two compositions were synthesised by arc-melting. This synthesis method could not be applied to the last composition, which was therefore completed directly by laser irradiation. The U – C – O composition of the samples was checked by using a combustion method in an ELTRA{sup ®} analyser. The eutectic temperature, established to be 2737 K ± 20 K, was used as a radiance reference together with the cubic – tetragonal (α → β) solid state transition, fixed at 2050 K ± 20 K. The normal spectral emissivity of the carbon-richer compounds increases up to 0.7, whereas the value 0.53 was established for pure hypostoichiometric uranium dicarbide at the limit of the eutectic region. This increase is analysed in the light of the demixing of excess carbon, and used for the determination of the liquidus temperature (3220 K ± 50 K for UC{sub 2.82}). Due to fast solid state diffusion, also fostered by the cubic – tetragonal transition, no obvious signs of a lamellar eutectic structure could be observed after quenching to room temperature. The eutectic surface C/UC{sub 2−x} composition could be qualitatively, but consistently, followed during the cooling process with the help of the recorded radiance spectra. Whereas the external liquid surface is almost entirely constituted by uranium dicarbide, it gets rapidly enriched in demixed carbon upon freezing. Demixed carbon seems to quickly migrate towards the inner bulk during further cooling. At the α → β transition, uranium dicarbide covers again the almost entire external surface. - Highlights: • The melting behaviour

  14. Novel 755-nm diode laser vs. conventional 755-nm scanned alexandrite laser: Side-by-side comparison pilot study for thorax and axillary hair removal.

    Science.gov (United States)

    Paasch, Uwe; Wagner, Justinus A; Paasch, Hartmut W

    2015-01-01

    Alexandrite (755 nm) and diode lasers (800-810 nm) are commonly used for hair removal. The alexandrite laser technology is somewhat cumbersome whereas new diode lasers are more robust. Recently, alexandrite-like 755 nm wavelength diodes became available. To compare the efficacy, tolerability, and subject satisfaction of a 755 nm diode laser operated in conventional (HR) and non-conventional in-motion (SHR) modes with a conventional scanned alexandrite 755 nm laser for chest and axillary hair removal. A prospective, single-center, proof of principle study was designed to evaluate the safety, efficacy and handling of a 755 nm diode laser system in comparison to a standard alexandrite 755 nm scanning hair removal laser. The new 755 nm diode is suitable to be used in SHR and HR mode and has been tested for its safety, efficacy and handling in a volunteer with success. Overall, both systems showed a high efficacy in hair reduction (88.8% 755 nm diode laser vs. 77.7% 755 nm alexandrite laser). Also, during the study period, no severe adverse effects were reported. The new 755 nm diode laser is as effective and safe as the traditional 755 nm alexandrite laser. Additionally, treatment with the 755 nm diode laser with HR and SHR modes was found to be less painful.

  15. Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

    Science.gov (United States)

    Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

    2017-10-30

    Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

  16. Study on laser beam welding technology for nuclear power plants

    International Nuclear Information System (INIS)

    Chida, Itaru; Shiihara, Katsunori; Fukuda, Takeshi; Kono, Wataru; Obata, Minoru; Morishima, Yasuo

    2012-01-01

    Laser beam welding is one of the jointing processes by irradiating laser beam on the material surface locally and widely used at various industrial fields. Toshiba has developed various laser-based maintenance and repair technologies and already applied them to several existing nuclear power plants. Laser cladding is a technique to weld the corrosion resistant metal onto a substrate surface by feeding filler wire to improve the corrosion resistance. Temper-bead welding is the heat input process to provide the desired microstructure properties of welded low alloy steels without post weld heat treatment, by inducing proper heat cycle during laser welding. Both laser welding technologies would be performed underwater by blowing the shielding gas for creating the local dry area. In this report, some evaluation results of material characteristics by temper-bead welding to target at Reactor Coolant System nozzle of PWR are presented. (author)

  17. Laser damage study of material of the first wall of target chamber of the future laser Megajoule

    International Nuclear Information System (INIS)

    Dubern, Christelle

    1999-01-01

    Study on damage of carbon-like, boron carbide, and stainless steel materials by ultraviolet laser light, has been carried out at CEA/CESTA in France. This work was performed to help designing and dimensioning the target chamber of the future Laser MegaJoule (LMJ) facility to be used for Inertial Confinement Fusion research. The study revealed that depending the laser fluence, the considered materials were ablated in different manners. lt was demonstrated that at low fluence, damage of carbon-like and boron carbide occurs through a thermal-mechanical mechanism resulting in sputtering of material. At higher fluence, damage was driven by a thermal mechanism, dissipating heat inside material until phase change developed. For stainless steel material, failures were the result of heat absorption associated to physical changes only. To explain and validate the proposed mechanisms, theoretical and experimental works were performed and satisfactory results came out. (author) [fr

  18. Pressure induced phase transitions in transition metal nitrides: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Anurag; Chauhan, Mamta [Advanced Material Research Lab, Indian Institute of Information Technology and Management, Gwalior 474010 (India); Singh, R.K. [Department of Physics, ITM University, Gurgaon 122017 (India)

    2011-12-15

    We have analyzed the stability of transition metal nitrides (TMNs) XN (X = Ti, Zr, Hf, V, Nb, Ta) in their original rocksalt (B1) and hypothetical CsCl (B2) type phases under high compression. The ground state total energy calculation approach of the system has been used through the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) type parameterization as exchange correlation functional. In the whole series of nitrides taken into consideration, tantalum nitride is found to be the most stable. We have observed that under compression the original B1-type phase of these nitrides transforms to a B2-type phase. We have also discussed the computation of ground state properties, like the lattice constant (a), bulk modulus (B{sub 0}) and first order pressure derivative of the bulk modulus (B'{sub 0}) of the TMNs and their host elements. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Coordination to transition metal surfaces : a theoretical study

    NARCIS (Netherlands)

    Santen, van R.A.

    1985-01-01

    A theoretical framework is developed that describes the chemisorption of CO to transition metal surfaces analogous to the HOMO-LUMO concept of MO theory. An explanation is given for the exptl. observation that CO adsorbs on top at the (111), face of Pt, but bridge at the (111) face of Ni. One is due

  20. Rovibronically selected and resolved two-color laser photoionization and photoelectron study of cobalt carbide cation.

    Science.gov (United States)

    Huang, Huang; Chang, Yih Chung; Luo, Zhihong; Shi, Xiaoyu; Lam, Chow-Shing; Lau, Kai-Chung; Ng, C Y

    2013-03-07

    We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization efficiency and pulsed field ionization-photoelectron (PFI-PE) study of gaseous cobalt carbide (CoC) near its ionization onset in the total energy range of 61,200-64,510 cm(-1). The cold gaseous CoC sample was prepared by a laser ablation supersonically cooled beam source. By exciting CoC molecules thus generated to single N' rotational levels of the intermediate CoC∗((2)Σ(+); v') state using a VIS dye laser prior to UV laser photoionization, we have obtained N(+) rotationally resolved PFI-PE spectra for the CoC(+)(X(1)Σ(+); v(+) = 0 and 1) ion vibrational bands free from interference by impurity species except Co atoms produced in the ablation source. The rotationally selected and resolved PFI-PE spectra have made possible unambiguous rotational assignments, yielding accurate values for the adiabatic ionization energy of CoC(X(2)Σ(+)), IE(CoC) = 62,384.3 ± 0.6 cm(-1) (7.73467 ± 0.00007 eV), the vibrational frequency ωe (+) = 985.6 ± 0.6 cm(-1), the anharmonicity constant ωe (+)χe (+) = 6.3 ± 0.6 cm(-1), the rotational constants (Be (+) = 0.7196 ± 0.0005 cm(-1), αe (+) = 0.0056 ± 0.0008 cm(-1)), and the equilibrium bond length re (+) = 1.534 Å for CoC(+)(X(1)Σ(+)). The observation of the N(+) = 0 level in the PFI-PE measurement indicates that the CoC(+) ground state is of (1)Σ(+) symmetry. Large ΔN(+) = N(+) - N' changes up to 6 are observed for the photoionization transitions CoC(+)(X(1)Σ(+); v(+) = 0-2; N(+)) ← CoC∗((2)Σ(+); v'; N' = 6, 7, 8, and 9). The highly precise energetic and spectroscopic data obtained in the present study have served as a benchmark for testing theoretical predictions based on state-of-the-art ab initio quantum calculations at the CCSDTQ∕CBS level of theory as presented in the companion article.

  1. Study of laser plasma emission from doped targets

    Czech Academy of Sciences Publication Activity Database

    Velardi, L.; Krása, Josef; Velyhan, Andriy; Nassisi, V.

    2012-01-01

    Roč. 83, č. 2 (2012), , "02B911-1"-"02B911-3" ISSN 0034-6748 R&D Projects: GA MŠk(CZ) 7E09092; GA MŠk(CZ) LC528 EU Projects: European Commission(XE) 228334 - LASERLAB-EUROPE Institutional research plan: CEZ:AV0Z10100523 Keywords : copper * excimer lasers * ion mobility * krypton compounds * laser ablation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.602, year: 2012

  2. Diagnostics for studies of novel laser ion acceleration mechanisms

    OpenAIRE

    Senje, Lovisa; Yeung, Mark; Aurand, Bastian; Kuschel, Stephan; Rödel, Christian; Wagner, Florian; Li, Kun; Dromey, Brendan; Bagnoud, Vincent; Neumayer, Paul; Roth, Markus; Wahlström, Claes-Göran; Zepf, Matthew; Kuehl, Thomas; Jung, Daniel

    2014-01-01

    Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflecte...

  3. New laser-driven nuclear excitation studies. Concepts and proposals

    International Nuclear Information System (INIS)

    Drska, L.; Hanus, V.; Sinor, M.

    2010-01-01

    Complete text of publication follows. There has been a great interest in the processes of nuclear excitation and triggering in high-parameter laser-produced plasmas in recent years. A series of papers devoted to the theory of this event has been published. Several experiments have already been attempted to study the excitation of the lowest nuclear levels of medium / high-Z nuclides (Ta 181, U 235 etc.), all the same unsuccessful or inconclusive. In the first part of this paper, the situation will be overviewed and analysis of the reasons of this unsatisfactory state of affairs will be accomplished. Prospects of the possible solving of the problem by using novel / projected laser facilities (esp. LIL / PETAL, XFEL, ELI-Phase) will be outlined. Potential of the future ELI Beam Facility in the Czech Republic in this area will be stressed. In the second part, some proposals for the excitation and triggering studies using combined high-power and high-intensity LIL / PETAL system (2012) with multi-kilojoule and multi-petawatt parameters will be discussed. Results of preliminary simulations supporting the thinking about potential projects will be shown and conditions essential for meaningful effort in this area will be analyzed. Problems of realistic simulations of such experiments will be addressed. Completely novel chances for the excitation / triggering studies would be started by constructed / projected facilities XFEL (coherent X-rays ∼ 12 keV, 2014) and ELI (multi-petawatt Phase 1, 2015). Application of intense / coherent high-energy X-rays and / or intense electron / ion beams allows new experimental schemes, extends the range of nuclides to be studied and (maybe) will enable to test some new triggering methods. In the last part of the presentation some possibilities in point (esp. for ELI Beamlines), will be drawn up. Acknowledgements. This research has been supported by the Research Program no. 6840770022 of the Ministry of Education, Youth and Sports of the

  4. Space electric power design study. [laser energy conversion

    Science.gov (United States)

    Martini, W. R.

    1976-01-01

    The conversion of laser energy to electrical energy is discussed. Heat engines in which the laser heats the gas inside the engine through a window as well as heat engines in which the gas is heated by a thermal energy storage reservoir which has been heated by laser radiation are both evaluated, as well as the necessary energy storage, transmission and conversion components needed for a full system. Preliminary system concepts are presented and a recommended development program is outlined. It appears possible that a free displacer Stirling engine operating directly a linear electric generator can convert 65% of the incident laser energy into electricity.

  5. Study of underwater laser propulsion using different target materials.

    Science.gov (United States)

    Qiang, Hao; Chen, Jun; Han, Bing; Shen, Zhong-Hua; Lu, Jian; Ni, Xiao-Wu

    2014-07-14

    In order to investigate the influence of target materials, including aluminum (Al), titanium (Ti) and copper (Cu), on underwater laser propulsion, the analytical formula of the target momentum IT is deduced from the enhanced coupling theory of laser propulsion in atmosphere with transparent overlay metal target. The high-speed photography method and numerical simulation are employed to verify the IT model. It is shown that the enhanced coupling theory, which was developed originally for laser propulsion in atmosphere, is also applicable to underwater laser propulsion with metal targets.

  6. Tunable diode laser measurement of self broadening versus temperature of five close ammonia transitions of the v2 band

    International Nuclear Information System (INIS)

    Baldacchini, G.; D'Amato, F.; Buffa, G.; Tarrini, O.; Ciucci, A.

    1995-08-01

    Self broadening coefficients have been measured as a functional of temperature form 192 to 377 K for five transition lines of the band of ammonia. The results have been compared with theoretical calculations performed in the semiclassical impact approximation, and although one hot transition does not fit well in this scheme, there is in general a fairly good agreement. Moreover there is also an experimental and theoretical evidence against the commonly assumed power law for the temperature dependence. More measurements are needed to clarify the position of the hot transitions in this respect and to verify the extent of validity of the power law in general

  7. X-ray laser studies using plasmas created by optical field ionization

    International Nuclear Information System (INIS)

    Krushelnick, K.M.; Tighe, W.; Suckewer, S.

    1995-01-01

    X-ray laser experiments involving the creation of fast recombining plasmas by optical field ionization of preformed targets were conducted. A nonlinear increase in the intensity of the 13.5nm Lyman-α line in Li III with the length of the target plasma was observed but only for distances less than the laser confocal parameter and for low plasma electron temperatures. Multiphoton pumping of resonant atomic transitions was also examined and the process of multiphoton ionization of FIII was found to be more probable than multiphoton excitation

  8. Locally preserved α  →  β phase transition in natural radiation-damaged titanite (CaTiSiO5): evidence from laser-induced photoluminescence and dielectric measurements

    Science.gov (United States)

    Beirau, Tobias; Murawski, Dawid; Behrens, Harald; Salje, Ekhard K. H.; Groat, Lee A.; Kaden, Ronny; Pöllmann, Herbert; Bismayer, Ulrich

    2018-01-01

    In situ temperature-dependent laser-induced photoluminescence and dielectric measurements provide new evidence for the local occurrence of the α  →  β phase transition near 500 K in the preserved crystalline parts of natural radiation-damaged titanite (sample E2335 with ~24% amorphous fraction, containing Fe and Al impurities). Photoluminescence spectroscopic measurements show an anomaly in the vicinity of 500 K. The temperature-dependent evolution of the real part of the electrical conductivity (σ) and the real (ɛ‧) and the imaginary (ɛ″) part of the complex dielectric permittivity (ɛ *) of titanite have been measured at various AC frequencies (~1.2-96.8 kHz). Despite the masking and smearing effect of impurities and defects, the temperature-dependent behaviour of ɛ‧ and ɛ″ around the transition temperature of the investigated natural titanite E2335 shows a remarkable similarity to that of the synthetic end-member material (see Zhang et al (1995 Phys. Chem. Miner. 22 41-9)). This study indicates the suitability of photoluminescence and impedance spectroscopy for the detection of phase transitions, even in heavily disordered systems.

  9. Studies of Hot Crack Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther

    During the present work crack testing concerning small and fast solidifying laser welds in austenitic stainless steel has been studied. A set of methods has been applied to investigate alloy properties, including ·Application of known information to predict solidification phases from the alloy...... composition. ·Weld metal solidification rate measurements for prediction of phases. ·Various crack tests to assess the crack susceptibility of alloys. ·A combination of the above for selection of suitable, weldable alloys. The possibility of using such specific methods for alloys and applications has been...... to the crack behaviour, but do not show an expected correlation between the crack resistance and the solidification rate. The employment of pulsed seams is therefore assessed not to be usable in the present selection methods. From evaluation of several crack tests, the Weeter spot weld test has been chosen...

  10. A Comparative Study on Cutting Electrodes for Batteries with Lasers

    Science.gov (United States)

    Luetke, Matthias; Franke, Volker; Techel, Anja; Himmer, Thomas; Klotzbach, Udo; Wetzig, Andreas; Beyer, Eckhard

    E-mobility is still one of the most discussed topics within the automotive industry. Electric powered vehicles can drive emissionfree and present consequently the future propulsion. Nearly all global players in the automotive industry are making great efforts to develop cost-efficient electric drives, which are suitable for series production. The national governments support this evolution progressively. For example the mobility research programme of the Federal Republic of Germany looks at the production of Li- Ion cells in its entirety. Within this programme the cutting of electrodes for Li-Ion cells by lasers is an issue, too. This paper provides a comparative study on cutting materials relevant for Li-Ion cells with beam sources operating in a cw mode and a pulsed mode respectively.

  11. Sputtering of amorphous carbon layers studied by laser induced fluorescence

    International Nuclear Information System (INIS)

    Pasch, E.

    1992-07-01

    In order to minimize the radiation losses, it is desirable to keep the plasmas in nuclear fusion devices free of high-Z-impurities. Therefore, the walls of TEXTOR and other tokamaks are covered with thin layers of amorphous carbon layers (a-C:H) or amorphous carbon/boron layers (a-C/B:H). The sputtering behaviour of these layers has been studied under bombardment by Ar + ions with energies of 1.5 keV and current densities of a few mA/cm 2 . Investigations of these coatings were carried out with the object to measure the velocity distribution of the sputtered atoms and the sputtered yields by laser induced fluorescence in the vacuum ultraviolet. (orig.)

  12. Pulsed laser photoacoustic spectrometer for study of solid materials

    International Nuclear Information System (INIS)

    Patel, N.D.; Kartha, V.B.

    1991-01-01

    The technique of photoacoustic spectroscopy has wide applications bacause it is extremely sensitive, and can be used to obtain spectra in wide spectral range for solids, liquids, gases, solutions, crystals etc. which may be usually difficult by conventional methods. For studying a variety of materials, a pulsed laser photoacoustic spectrometer has been set up in the laboratory. The report discusses the design and performance of the instrument. Some of the spectra of materials like Nd 2 O 9 powder, Nd-YAG crystal, CoCl 2 6H 2 O etc. are shown. A detailed discussion on assignment of the spectra of Nd-YAG is also presented. (author). 4 refs., 5 figs., 1 tab

  13. Studies of the Superconducting Transition in the Mo/Au-Bilayer Thin Films

    Science.gov (United States)

    Sadleir, John; Smith, Stephen; Iyomoto, naoko; Bandler, Simon; Chervenak, Jay; Brown, Ari; Brekowsky, Regis; Kilbourne, Caroline; Robinson, Ian

    2007-01-01

    At NASA Goddard, microcalorimeter arrays using superconducting transition edge sensor thermometers (TESs) are under development for high energy resolution X-ray astrophysics applications. We report on our studies of the superconducting transition in our Mo/Au-bilayer TES films including: low current measurements of the superconducting bilayer's resistance transition versus temperature on pixels with different normal metal absorber attachment designs and measured temperature scaling of the critical current and critical magnetic field.

  14. Home Away from Home?: A Case Study of Student Transitions to an International Branch Campus

    Science.gov (United States)

    Cicchetti, Kaitlin Oyler

    2017-01-01

    This study explored the transition experience of home-campus students attending an international branch campus. The studied was informed by a diverse range of literature, including the internationalization of higher education and student affairs, development of international branch campuses, students in transition, the development of student…

  15. ILIAS. Ion and laser beam interaction and application studies. Progress report no. 3 of the PHELIX theory group

    Energy Technology Data Exchange (ETDEWEB)

    Mulser, P. (ed.)

    2008-04-15

    The following topics are dealt with: The PHELIX laser-plasma facility, coupling of nuclear matter to intense photon fields, QED effects in strong laser fields, relativistic critical density increase in a linearly polarized laser beam, absorption of ultrashort laser pulses in strongly overdense targets, Coulomb focusing in electron-ion collisions in a strong laser field, quasiperiodic waves in relativistic plasmas, high-energy-density physics studied by intense particle beams, heavy ions in a high-power laser beam, Monte-Carlo study of electron dynamics in silicon during irradiation with an ultrashort VUV laser pulse. (HSI)

  16. ILIAS. Ion and laser beam interaction and application studies. Progress report no. 3 of the PHELIX theory group

    International Nuclear Information System (INIS)

    Mulser, P.

    2008-04-01

    The following topics are dealt with: The PHELIX laser-plasma facility, coupling of nuclear matter to intense photon fields, QED effects in strong laser fields, relativistic critical density increase in a linearly polarized laser beam, absorption of ultrashort laser pulses in strongly overdense targets, Coulomb focusing in electron-ion collisions in a strong laser field, quasiperiodic waves in relativistic plasmas, high-energy-density physics studied by intense particle beams, heavy ions in a high-power laser beam, Monte-Carlo study of electron dynamics in silicon during irradiation with an ultrashort VUV laser pulse. (HSI)

  17. Value of radionuclide oesophageal transit in studies of functional dysphagia

    International Nuclear Information System (INIS)

    Llamas-Elvira, J.M.; Martinez-Parades, M.; Velasco-Lajo, T.

    1986-01-01

    Radionuclide oesophageal transit time was evaluated in 70 individuals, divided into three groups: normal individuals, patients with non-organic dysphagia and patients with primary oesophageal motility disorders treated with per-endoscopic forced pneumatic dilatation. In all of them the oesophageal transit time of a bolus of water with 18.5 MBq (500 μCi) of 99 Tcsup(m) sulphur colloid was assessed, as was the percentage of residual activity of the bolus in the oesophagus. There was a significant difference in these parameters between the control group and the group with non-organic dysphagia, the diagnostic capacity of this test being 93% sensitivity, 100% specificity, 100% positive predictive value and 90% negative predictive value, which suggests its inclusion in diagnostic protocols of dysphagias. In patients with primary oesophageal motility disorders, a significant decrease in values of residual activity has been observed after treatment with per-endoscopic forced pneumatic dilation. (author)

  18. Comprehensive study of electro-optic and passive Q-switching in solid state lasers for altimeter applications

    Science.gov (United States)

    Bhardwaj, Atul; Agrawal, Lalita; Pal, Suranjan; Kumar, Anil

    2006-12-01

    Laser Science and Technology Center (LASTEC), Delhi, is developing a space qualified diode pumped Nd: YAG laser transmitter capable of generating 10 ns pulses of 30 mJ energy @ 10 pps. This paper presents the results of experiments for comparative studies between electro-optic and passively Q-switched Nd: YAG laser in a crossed porro prism based laser resonator. Experimental studies have been performed by developing an economical bench model of flash lamp pumped Nd: YAG laser (rod dimension, \

  19. Theoretical study of laser feedback interferometry for dynamical material's behaviour studies

    International Nuclear Information System (INIS)

    Le-Barbier, Laura

    2017-01-01

    The purpose of this thesis is to study the feasibility of optical feedback interferometry (OFI) for measuring velocities for dynamical material's behaviour studies. Dynamical material's behaviour studies permit to analyse the shocked material when subjects to shocks (laser shocks, isentropic compression, projectiles, etc.). In these conditions, we seek to measure velocities up to 10 km/s. The OFI technique is regularly used as an embedded system to measure slow velocities in various fields. However, very few studies have been performed for determining velocities measurement limits for this system. As a matter of fact, the optical feedback induces nonlinear effects into the laser's cavity: it disrupts the laser's emitted optical power. Depending on the optical feedback strength, the laser can show chaotic behaviour, then it is no longer possible to get the information for the target's velocity or displacement regarding the signal. In this study, we have been developing mathematical models and performing a wide range of numerical simulations to study the performances and the limits of the OFI technique. We have been also studying the influence of the targets reflectivity, the length and the modulation frequency of the external cavity. (author) [fr

  20. Transitional circuitry for studying the properties of DNA

    Science.gov (United States)

    Trubochkina, N.

    2018-01-01

    The article is devoted to a new view of the structure of DNA as an intellectual scheme possessing the properties of logic and memory. The theory of transient circuitry, developed by the author for optimal computer circuits, revealed an amazing structural similarity between mathematical models of transition silicon elements and logic and memory circuits of solid state transient circuitry and atomic models of parts of DNA.

  1. Study of XUV lasers produced by a CO/sub 2/ laser

    International Nuclear Information System (INIS)

    Daido, H.; Miura, E.; Kitagawa, Y.; Kato, Y.; Nishihara, K.; Sawai, K.; Nakai, S.S.; Yamanaka, C.

    1988-01-01

    The authors present recent progress at ILE, Osaka University in plasma recombination-pumped XUV lasers produced by a CO/sub 2/ laser. One way to produce large-population inversion with this scheme is rapid cooling of the gain medium keeping a high electron density, because the three-body recombination probability is proportional to the square of the electron density. The authors used a cylinder-type target made of 30-μm thick parylene (C/sub 8/H/sub 8/) whose diameter and length are 3 and 4 mm. The laser irradiated the 2500-A thick parylene foil attached to the center of the cylinder. The fully ablated plasma expands isotropically, producing an almost uniform plasma on the cylinder wall. Then the almost fully ionized carbon plasma is cooled by heat transport from the hot plasma to the wall. The estimated cooling time is a few nanoseconds assuming classical heat transport

  2. Study of non-thermal effects from laser radiation on live tissues

    International Nuclear Information System (INIS)

    Cotta, M.A.

    1987-02-01

    The functional biological effects related to the irradiation of live tissues with low power lasers, called non-thermal effects were theoretical and experimentally studied. For the experimental part, a device which allows to: irradiation lesions artificially created on the back of rats by a He-Ne laser, or put a moving ground glass in front of the laser beam, by irradiation of this same laser with its coherence degree decreased. The relevance of the radiation coherence in the lesion cicatrization process was shown. The electrical field distribution and the intensity distribution on a surface with micro-roughness when irradiated by coherent light are theoretically studied. (M.C.K.) [pt

  3. Resonant laser ablation: mechanisms and applications

    International Nuclear Information System (INIS)

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

    1996-01-01

    Resonant laser ablation (RLA) typically relies on irradiation of a sample in a mass spectrometer with modest intensity laser pulses tuned to a one or two photon resonant transition in the analyte of interest. This paper shows that RLA is well suited for highly sensitive analyses of complex samples. The examples actually studied are trace components in rhenium and technetium in nickel. The authors also studied the 2+1 multiphoton ionization spectrum of iron-56 detected by RLA of Re containing 70 ppm iron. Two-photon transition rates for Fe transitions were calculated perturbatively and found to agree semi-quantitatively with experimentally observed intensities. 17 refs., 3 figs

  4. Laser pumped lasers for isotope separation

    International Nuclear Information System (INIS)

    Fry, S.M.

    1976-01-01

    A study of the isotope separation laser requirements reveals that high pressure polyatomic molecular gas laser pumped lasers can attain the necessary characteristics including tunability, energy output, pulse width, and repetition rate. The results of a search, made for molecules meeting the appropriate requirements for one of several pump schemes utilizing a CO 2 laser and with output in the 12 μm or 16μm wavelength range, are presented. Several methods of pumping are reviewed and two novel pump schemes are presented. A laser pumped laser device design is given, and operation of this device and associated diagnostic equipment is confirmed by repeating experiments in OCS and NH 3 . The results of OCS laser experiments show that an improvement in pump rate and output per unit length is obtained with the device, using a wedged transverse pumping scheme. A new multi-line laser system in NH 3 pumped by a TEA CO 2 laser is reported. More than forty transitions spanning the wavelength range of 9.2 to 13.8 μm are observed and identified. A strong output at 12.08 μm is one of the closest lines yet found to the required laser isotope separation wavelength. Far infrared emission near 65 μm is observed and is responsible for populating levels which lase in pure ammonia near 12.3 μm. Buffer gas (e.g., N 2 or He) pressures of approximately 40--800 torr cause energy transfer by collision-induced rotationaltransitions from the pumped antisymmetric to the lasing symmetric levels in the nu 2 = 1 band of ammonia. Most of the observed lines are aP(J,K) transitions which originate from the nu 2 /sup s/ band. Measurements of the pressure dependence of the laser output shows that some lines lase at pressures greater than one atmosphere. Transient behavior of the 12.08 μm line is calculated from a simplified analytic model and these calculations are compared to the experimental results

  5. Experimental studies of laser guiding and wake excitation in plasma channels

    International Nuclear Information System (INIS)

    Volfbeyn, P.; Lawrence Berkeley National Lab., CA

    1998-06-01

    This thesis presents results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor-Heater scheme was proposed and experimentally tested in hydrogen and nitrogen. It made use of two laser pulses. The Ignitor, an ultrashort ( 17 W/cm 2 , 75fs laser pulse. The guiding properties and transmission and coupling efficiency were studied as a function of relative position of the channel and the injection pulse focus. Whereas entrance coupling efficiency into the channel was lower than expected, channel coupling to continuum losses were found to be in good agreement with analytical predictions. The authors speculate that increased coupling efficiency can be achieved through better mode matching into the channel. Analytic and numerical one dimensional (1-D), nonrelativistic theory of laser pulse propagation in underdense plasma was presented, in the context of laser wakefield acceleration. The relation between the laser pulse energy depletion, longitudinal laser pulse shape distortion, and changes in the group velocity and center wavelength was explored. 1-D theory was extended to treat the case of a laser exciting a wake in a hollow plasma channel, by making use of an energy conservation argument. Based on the results of this theory, a laser wakefield diagnostic was proposed where, by measuring the changes in phase or spectrum of the driving laser pulse, it is possible to infer the amplitude of the plasma wake

  6. Experiment and simulation study of laser dicing silicon with water-jet

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Jiading; Long, Yuhong, E-mail: longyuhong@guet.edu.cn; Tong, Youqun; Yang, Xiaoqing; Zhang, Bin; Zhou, Zupeng

    2016-11-30

    Highlights: • The explosive melt expulsion could be a dominant process for the laser ablating silicon in liquids with ns-pulsed laser of 1064 nm irradiating. • Self-focusing phenomenon was found and its causes are analyzed. • SPH modeling technique was employed to understand the effect of water and water-jet on debris removal during water-jet laser machining. - Abstract: Water-jet laser processing is an internationally advanced technique, which combines the advantages of laser processing with water jet cutting. In the study, the experiment of water-jet laser dicing are conducted with ns pulsed laser of 1064 nm irradiating, and Smooth Particle Hydrodynamic (SPH) technique by AUTODYN software was modeled to research the fluid dynamics of water and melt when water jet impacting molten material. The silicon surface morphology of the irradiated spots has an appearance as one can see in porous formation. The surface morphology exhibits a large number of cavities which indicates as bubble nucleation sites. The observed surface morphology shows that the explosive melt expulsion could be a dominant process for the laser ablating silicon in liquids with nanosecond pulse laser of 1064 nm irradiating. Self-focusing phenomenon was found and its causes are analyzed. Smooth Particle Hydrodynamic (SPH) modeling technique was employed to understand the effect of water and water-jet on debris removal during water-jet laser machining.

  7. Experimental study of laser-plasma interaction physics with short laser wavelength

    International Nuclear Information System (INIS)

    Labaune, C.; Amiranoff, F.; Fabre, E.; Matthieussent, G.; Rousseaux, C.; Baton, S.

    1989-01-01

    Many non-linear processes can affect laser-plasma coupling in fusion experiments. The interaction processes of interest involve three or more waves, including the incident electromagnetic wave and various selections of electromagnetic, electrostatic and accoustic waves. Whenever plasma waves are involved (stimulated Raman scattering, two-plasmon decay instability, parametric decay instability and others), energetic electrons are created through the various damping processes of these waves: these energetic electrons in turn deleteriously affect the compression phase in laser fusion experiments through pre-heating of the fuel core. Some parametric processes lead primarily to loss of incident laser energy (stimulated Brillouin scattering) while others, such as filamentation, lead to strongly enhanced local laser intensities through the focusing of part (or all) of the laser beam into filaments of very small dimensions with a concomitant expulsion of the plasma out of these regions. So filamentation destroys the uniformity of energy deposition in the plasma and prevents high compression efficiency of the target. These interaction effects are typically of parametric nature, with their thresholds and growth rates depending critically on plasma scale lengths. Since these scale lengths increase with available laser energy and since millimeter sized plasmas are expected from reactor targets which will be used in direct drive implosion experiments, a good understanding of these processes and their saturation mechanisms becomes imperative. We report here the results on absolute energy measurements and time-resolved spectra of SRS and SBS obtained in various types of plasmas where the major changes were the inhomogeneity scale lengths. (author) 7 refs., 7 figs

  8. LASERS: A cryogenic slab CO laser

    Science.gov (United States)

    Ionin, Andrei A.; Kozlov, A. Yu; Seleznev, L. V.; Sinitsyn, D. V.

    2009-03-01

    A compact capacitive transverse RF-discharge-pumped slab CO laser with cryogenically cooled electrodes, which operates both in the cw and repetitively pulsed regimes, is fabricated. The laser operation is studied in the free running multifrequency regime at the vibrational - rotational transitions of the fundamental (V + 1 → V) vibrational bands of the CO molecule in the spectral region from 5.1 to 5.4 μm. Optimal operation conditions (gas mixture composition and pressure, RF pump parameters) are determined. It is shown that only gas mixtures with a high content of oxygen (up to 20% with respect to the concentration of CO molecules) can be used as an active medium of this laser. It is demonstrated that repetitively pulsed pumping is more efficient compared to cw pumping. In this case, quasi-cw lasing regime can be obtained. The maximum average output power of ~12 W was obtained for this laser operating on fundamental bands and its efficiency achieved ~14 %. The frequency-selective operation regime of the slab RF-discharge-pumped CO laser was realised at ~ 100 laser lines in the spectral region from 5.0 to 6.5 μm with the average output power of up to several tens of milliwatts in each line. Lasing at the transitions of the first vibrational overtone (V + 2 → V) of the CO molecule is obtained in the spectral region from 2.5 to 3.9 μm. The average output power of the overtone laser achieved 0.3 W. All the results were obtained without the forced gas mixture exchange in the discharge chamber. Under fixed experimental conditions, repetitively pulsed lasing (with fluctuations of the output characteristics no more than ±10 %) was stable for more than an hour.

  9. Hybrid Ti:Sapphire / KrF laser facility GARPUN for combined subpicosecond/nanosecond laser-matter interaction studies

    International Nuclear Information System (INIS)

    Zvorykin, V.D.; Ionin, A.A.; Konyashcenko, A.V.; Levchenko, A.O.; Krokhin, O.N.; Mesyats, G.A.; Molchanov, A.G.; Rorulev, M.A.

    2006-01-01

    Complete test of publication follows. Hybrid laser facility consisting of Ti:Sapphire front end, 3ω converter, and e-beam-pumped large-aperture KrF amplifiers is under construction to generate combined sub-picosecond/nanosecond pulses in UV spectral range at 248-nm wavelength. This is a part of the Petawatt excimer laser project started at P.N. Lebedev Physical Institute. In comparison with commonly used solid-state chirped-pulse amplifiers (CPA), KrF amplifiers have following advantages: (i) low-density gaseous matter with three orders of magnitude lower non-linear refraction index has a small value of B-integral and negligible pulse distortion; (ii) short radiation lifetime τ r = 6 ns of the upper laser level of KrF(B-X) transition (with accounting for collisions τ c ∼ 2 ns), that means the population inversion is recovered each 2 ns during the pumping time, which is typically τ p ≥ 100 ns for technical reasons. Thus, it might be possible eliminating of very costly large-aperture compressor gratings and to amplify both short τ sh c and long τ long ≥ τ c pulses in the same amplifiers, as a short pulse does not affect the gain during the most of pumping. This gives a unique opportunity for realization of fast-ignition scheme in Inertial Confinement Fusion using large-scale KrF drivers. The Ti:Sapphire front end 'Start 248M' currently operates with the following parameters: rep rate 10 Hz, pulse energy and duration at fundamental wavelength (744 nm) > 8 mJ and 0.5 mJ and 0.4 mJ, 740 nm) and multi-pass amplifier (10 Hz, > 15 mJ, 740 nm), both pumped by 2ω pulsed Lotis LS-2134 Nd:YAG laser (10 Hz, 10 ns, 532 nm) with distributed energies of 5 and 70 mJ, two-gratings compressor, and 3ω converter with two BBO crystals and total efficiency 8%. EMG 150MSC Lambda Physik KrF laser is used afterwards to generate ns pulses and to amplify fs pulses in its two separate discharge chambers. Two e-beam pumped KrF amplifiers Berdysh and GARPUN with active volumes 10

  10. Application of laser resonance scattering to the study of high-temperature plasma-wall interaction

    International Nuclear Information System (INIS)

    Maeda, Mitsuo; Muraoka, Katsunori; Hamamoto, Makoto; Akazaki, Masanori; Miyazoe, Yasushi

    1981-01-01

    Studies on laser resonance scattering and its application to the study of high-temperature plasma-wall interaction are reviewed. The application of dye laser beam to resonant scattering method has been developed. This method is able to detect low density atoms. The fluorescent photon counts can be estimated for a two-level system and a three-level system. The S/N ratio, Which is in close connection with the detection limit, has been estimated. The doppler effect due to the thermal motion of atoms is taken into consideration. The calibration of the absolute number of atoms is necessary. Tunable coherent light is used as the light source for resonance scattering method. This is able to excite atoms strongly and to increase the detection efficiency. As dye lasers, a N 2 laser, a YAG laser, and a KrF excimer laser have been studied. In VUV region, rare gas or rare gas halide lasers can be used. The strong output power can be expected when the resonance lines of atoms meet the synchronizing region of the excimer laser. The resonance scattering method is applied to the detection of impurity metal atoms in plasma. The studies of laser systems for the detection of hydrogen atoms are also in progress. (Kato, T.)

  11. Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers

    Science.gov (United States)

    Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart

    Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influence of the green wavelength on energy coupling during heat conduction welding and deep penetration welding as well as the influence on the weld shape has been investigated.

  12. Studies on 16 μm spin-flip raman lasers in Tottori University

    International Nuclear Information System (INIS)

    Miyazaki, Kazuhiko

    1986-01-01

    This report outlines the studies on 16 μm spin-flip Raman lasers which have been carried out in Tottori University, Japan. Following the introductory section, the second section of the report deals with performance of infrared lasers for molecular laser isotope separation of UF 6 . It is stressed that the wavelength of the oscillation line should be accurately controlled in the vicinity of 628 cm -1 . The third section addresses 16 μm infrared lasers. Semiconductor diode lasers of Pb 1-x Sn x Te or Pb 1-x Sn x Se are available for the infrared region around 16 μm. Though the wavelength resolution is high and the oscillation wavelength is adjustable in these lasers, their oscillation outputs are not sufficient for the purpose of uranium separation. On the other hand, there are active studies on light-excited infrared gas lasers. It seems very difficult, however, to adjust the wavelength of their oscillation lines to the infrared absorption wavelength of 235 U. Thus, attention is currently focused on Raman lasers in the region around 16 μm. The fourth section briefly summarizes studies conducted in the University during these ten-odd years and the research facilities currently used. In particular, the major part is devoted to research and development of infrared NH 3 lasers and studies on InSb SFR (spin-flip Raman) lasers pumped with an NH 3 laser. A 12.97 μm and a 13.27 μm oscillation line have been obtained with a high output, which is hoped to serve for increasing the output of the 15.9 μm line of InSb SFR lasers. (Nogami, K.)

  13. PRK by Er:YAG laser: in-vitro studies and first in-vivo experiences

    Science.gov (United States)

    Steiner, Rudolf W.; Leiacker, Richard; Russ, Detlef; Seiler, Theo

    1996-01-01

    Photorefractive keratectomy (PRK) is usually performed by an excimer laser at 193 nm wavelength. Ablatio of corneal tissue is, however, not only possible in the UV region of the optical spectrum but also in the IR where water is an excellent absorber. Therefore, an Er:YAG laser was used at 2.94 micrometer wavelength as an alternative laser light source to perform in vitro studies of corneal ablation and also first clinical experiments to correct myopia of patients with blind eyes.

  14. A thyratron-switched modular CO2 TEA laser for infrared photochemical studies

    International Nuclear Information System (INIS)

    Hamilton, N.; Kelly, J.W.; Struve, H.

    1982-09-01

    A thyratron-switched, ultraviolet pre-ionised CO 2 TEA laser, consisting of four modules connected in series, has been designed and constructed. The laser can be operated in the TEM 00 mode and is able to produce 2.5 J per pulse. The design and operation of the laser as a tool for infrared studies is discussed together with an evaluation of the effect of operating parameters on output characteristics

  15. High Intensity Laser Therapy (HILT) versus TENS and NSAIDs in low back pain: clinical study

    Science.gov (United States)

    Zati, Allesandro; Fortuna, Damiano; Valent, A.; Filippi, M. V.; Bilotta, Teresa W.

    2004-09-01

    Low back pain, caused by lumbar disc herniation, is prevalently treated with a conservative approach. In this study we valued the efficacy of High Intensity Laser Therapy (HILT), compared with accepted therapies such as TENS and NSAIDs. Laser therapy obtained similar results in the short term, but better clinical effect over time than TENS and NSAIDs. In conclusion high intensity laser therapy appears to be a interesting new treatment, worthy of further research.

  16. Laser-enhanced cavitation during high intensity focused ultrasound: An in vivo study

    OpenAIRE

    Cui, Huizhong; Zhang, Ti; Yang, Xinmai

    2013-01-01

    Laser-enhanced cavitation during high intensity focused ultrasound (HIFU) was studied in vivo using a small animal model. Laser light was employed to illuminate the sample concurrently with HIFU radiation. The resulting cavitation was detected with a passive cavitation detector. The in vivo measurements were made under different combinations of HIFU treatment depths, laser wavelengths, and HIFU durations. The results demonstrated that concurrent light illumination during HIFU has the potentia...

  17. Synchrotron X-ray topographic studies of para-ferroelectric transition in ammonium sulphate crystal

    International Nuclear Information System (INIS)

    Bhat, H.L.; Roberts, K.J.

    1993-01-01

    Ammonium sulphate undergoes a para-ferroelectric transition at 223 K. The transition is presumably first order in nature. White radiation topographic studies of this transition are presented here. The existence of pre-transition effects due to lattice deformation leading to severe strain is noticed. This sometimes resulted in dislocation generation. The well defined phase boundary observed in this crystal confirms the first order nature of this transition. The zigzag nature of the phase boundary with preferably oriented segments has been attributed to the specific properties of the strain tensors of the transition. Ferroelectric domains have also been detected by faint dynamical x-ray contrast of their images. (author). 7 refs., 1 fig

  18. Dimensionally similar studies of confinement and H-mode transition in ASDEX Upgrade and JET

    International Nuclear Information System (INIS)

    Ryter, F.; Stober, J.; Suttrop, W.

    2001-01-01

    Joint experiments on confinement and L-H transition were performed in ASDEX Upgrade and JET. The confinement experiments suggest that the invariance principle is not always fulfilled at high density. For the L-H transition studies, the dimensionless variables taken at the plasma edge can be in general only made identical per pair, due to the condition imposed by the L-H transition. This new approach to investigate the L-H physics suggests a weak dependence of the L-H transition mechanism on collisionality. (author)

  19. Dimensionally similar studies of confinement and H-mode transition in ASDEX Upgrade and JET

    International Nuclear Information System (INIS)

    Ryter, F.; Stober, J.; Suttrop, W.

    1999-01-01

    Joint experiments on confinement and L-H transition were performed in ASDEX Upgrade and JET. The confinement experiments suggest that the invariance principle is not always fulfilled at high density. For the L-H transition studies, the dimensionless variables taken at the plasma edge can be in general only made identical per pair, due to the condition imposed by the L-H transition. This new approach to investigate the L-H physics suggests a weak dependence of the L-H transition mechanism on collisionality. (author)

  20. Experimental study of laser-oxygen cutting of low-carbon steel using fibre and CO2 lasers under conditions of minimal roughness

    International Nuclear Information System (INIS)

    Golyshev, A A; Malikov, A G; Orishich, A M; Shulyatyev, V B

    2014-01-01

    The results of an experimental study of laser-oxygen cutting of low-carbon steel using fibre and CO 2 lasers are generalised. The dependence of roughness of the cut surface on the cutting parameters is investigated, and the conditions under which the surface roughness is minimal are formulated. It is shown that for both types of lasers these conditions can be expressed in the same way in terms of the dimensionless variables – the Péclet number Pe and the output power Q of laser radiation per unit thickness of the cut sheet – and take the form of the similarity laws: Pe = const, Q = const. The optimal values of Pe and Q are found. We have derived empirical expressions that relate the laser power and cutting speed with the thickness of the cut sheet under the condition of minimal roughness in the case of cutting by means of radiation from fibre and CO 2 lasers. (laser technologies)

  1. Health and wellbeing during transition to adulthood for young people with intellectual disabilities: A qualitative study.

    Science.gov (United States)

    Young-Southward, Genevieve; Cooper, Sally-Ann; Philo, Christopher

    2017-11-01

    Transition to adulthood may have negative consequences for health and wellbeing in individuals with intellectual disabilities (ID), but this aspect of transition has received little investigation. This qualitative study aimed to explore the transition experiences of individuals with ID from their own perspectives, and from that of their parents, in order to identify health or wellbeing implications of transition. Semi-structured interviews were conducted with 17 young people with mild, moderate and severe ID aged 16-27 years and with 23 parents of young people with mild, moderate, severe and profound ID aged 16-26 years. Interviews were analysed using thematic analysis, deploying both emic and etic coding categories. This study provides direct insights into the issues on health and wellbeing that young people with ID and their parents find important during transition. The primary health implication of transition centred on mental health and wellbeing; young people experienced heightened anxiety during transition, and themes identified as contributing to anxiety included: a lack of meaningful activity following school exit; inadequate support during transition; and difficulties associated with 'growing up'. Problem behaviours and obesity were also implicated. The transition from school needs to be better supported in order to ease anxiety for young people during this difficult period. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Potential of public transit as a transportation control measure: Case studies

    Energy Technology Data Exchange (ETDEWEB)

    Sillings, M.

    1998-07-01

    This report is the final product of the Clean Air Project of the National Association of Regional Councils/NARC. It documents a nationwide study of transit projects and programs initiated in the wake of the 1990 Clean Air Act Amendments/CAAA and the Intermodal Surface Transportation Efficiency Act of 1991/ISTEA. The study purpose was to assess the experience, limitations, and value of public transit as a potential transportation control measure/TCM, i.e., generates significant air quality benefits by eliminating or reducing emissions from motor vehicles. Four in-depth case studies and six additional projects featured as innovations in transportation are offered as examples investigating the potential of transit as a TCM. These case studies and innovations highlight the efforts of ten metropolitan areas and transit agencies which have succeed in developing and implementing innovative transit strategies.

  3. Laser-activated solid protein bands for peripheral nerve repair: an vivo study.

    Science.gov (United States)

    Lauto, A; Trickett, R; Malik, R; Dawes, J M; Owen, E R

    1997-01-01

    Severed tibial nerves in rats were repaired using a novel technique, utilizing a semiconductor diode-laser-activated protein solder applied longitudinally across the join. Welding was produced by selective laser denaturation of solid solder bands containing the dye indocyanine green. An in vivo study, using 48 adult male Wistar rats, compared conventional microsuture-repaired tibial nerves with laser solder-repaired nerves. Nerve repairs were characterised immediately after surgery and after 3 months. Successful regeneration with average compound muscle action potentials of 2.5 +/- 0.5 mV and 2.7 +/- 0.3 mV (mean and standard deviation) was demonstrated for the laser-soldered nerves and the sutured nerves, respectively. Histopathology confirmed comparable regeneration of axons in laser- and suture-operated nerves. The laser-based nerve repair technique was easier and faster than microsuture repair, minimising manipulation damage to the nerve.

  4. Effect of axial length on laser spot size during photodynamic therapy: an experimental study in monkeys.

    Science.gov (United States)

    Kondo, Mineo; Ito, Yasuki; Miyata, Kentaro; Kondo, Nagako; Ishikawa, Kohei; Terasaki, Hiroko

    2006-01-01

    To investigate the effect of shorter axial length on the laser spot size and laser energy during photodynamic therapy (PDT) in monkeys. Experimental study with four rhesus monkeys. PDT was performed on the normal retina of monkeys whose ocular axial lengths are shorter (19.55 to 20.25 mm) than that of humans. After the PDT, the eyes were enucleated, and the diameter of the irradiated laser spot was measured with a microcaliper. The area of actual laser spot was only 0.56 to 0.61 times of the planned area, which indicated that the laser energy/area was 1.64 to 1.78 times more intense than planned initially. These results are the in vivo demonstration that the diameter of PDT laser spot is smaller for eyes with shorter axial lengths.

  5. Study of silica coatings degradation under laser irradiation and in controlled environment

    International Nuclear Information System (INIS)

    Becker, S.

    2006-11-01

    Performances of optical components submitted to high laser intensities are usually determined by their laser-induced damage threshold. This value represents the highest density of energy (fluence) sustainable by the component before its damage. When submitted to laser fluences far below this threshold, optical performances may also decrease with time. The degradation processes depend on laser characteristics, optical materials, and environment around the component. Silica being the most used material in optics, the aim of this study was to describe and analyse the physical-chemical mechanisms responsible for laser-induced degradation of silica coatings in controlled environment. Experimental results show that degradation is due to the growth of a carbon deposit in the irradiated zone. From these results, a phenomenological model has been proposed and validated with numerical simulations. Then, several technological solutions have been tested in order to reduce the laser-induced contamination of silica coatings. (author)

  6. Laser assisted crystallization of ferromagnetic amorphous ribbons: A multimodal characterization and thermal model study

    Energy Technology Data Exchange (ETDEWEB)

    Katakam, Shravana; Santhanakrishnan, S.; Smith, Casey; Banerjee, Rajarshi; Dahotre, Narendra B. [Laboratory of Laser Materials Processing and Synthesis Department of Materials Science and Engineering University of North Texas, Denton, Texas 76207 (United States); Devaraj, Arun; Bowden, Mark; Thevuthasan, Suntharampillai [William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Ramanujan, R. V. [Schhol of Materials Science and Engineering Nanyang Technological University, Singapore 639798 (Singapore)

    2013-11-14

    This paper focuses on laser-based de-vitrification of amorphous soft magnetic Fe-Si-B ribbons and its consequent influence on the magnetic properties. Laser processing resulted in a finer scale of crystallites due to rapid heating and cooling during laser annealing compared to conventional furnace annealing process. A significant increase in saturation magnetization is observed for laser-annealed ribbons compared to both as-received and furnace annealed samples coupled with an increase in coercivity compared to the as received samples. The combined effect of thermal histories and stresses developed during laser annealing results in the formation of nano-crystalline phase along the laser track. The phase evolution is studied by micro-XRD and TEM analysis. Solute partitioning and compositional variation within the phases are obtained by Local Electrode Atom probe analysis. The evolution of microstructure is rationalized using a Finite Element based heat transfer multi-physics model.

  7. Proceedings of the conference on lasers and electro-optics

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

    This book presents the papers discussed at a conference on the subject of electro-optics and lasers. Some of the topics discussed were: laser fusion and interactions; implosion experiments; tunable integrated Bragg lasers, CO 2 lasers; present status of integrated lasers; DFB lasers; transition metal lasers-solid state lasers, mirror laser resonators, multiquantumwell lasers; fusion laser technology; and dynamics and characteristics of diode lasers

  8. Study of the low energy gamma transitions of molybdenum 99; Etude des transitions gamma de basse energie du molybdene 99

    Energy Technology Data Exchange (ETDEWEB)

    Ravier, J.

    1959-07-01

    The study of the decay scheme of Mo{sup 99} has been performed on the magnetic iron-less and double focalization spectrograph of the Institute of Nuclear Physics of Lyon. Methods of internal and external conversion have been used. The intensities of the Mo{sup 99} sources used were not strong enough to determine the characteristics of the internal conversion accurately but were sufficient to precise the decay scheme at low energy. We have determined the internal conversion ratio for the transition of 180 KeV, we have got: 0.13 ± 0.03 which is not in agreement with the value given by a previous experiment based on γ-γ coincidence. Our method seems to be more reliable. We confirm the E2 feature of this transition and its 5/2+ spin. We have determined another important parameter for the 180 KeV de-excitation: the percentage of transitions that do not pass by the isomeric level but by the 140 KeV level is (6 ± 2)%, the isomeric level being at 142 KeV. The gamma spectra at low energy has been studied through the photoelectric effect in a lead converter [French] L'etude du schema de desintegration du Mo{sup 99} deja faite par differents auteurs a ete reprise par des methodes de conversion interne et externe, an moyen du spectrographe magnetique sans fer et a double focalisation de l'Institut de Physique Nucleaire de Lyon. Apres avoir cherche les possibilites d'obtention de sources de haute activite specifique par separation isotopique Szilard-Chalmers sur des molybdates alcalins, le spectre de conversion interne a basse energie a ete mesure. Ainsi se trouverent etre determines les coefficients partiaux de conversion interne. Le spectre γ a basse energie a ete etudier au moyen de l'effet photoelectrique sur un convertisseur de plomb. Les coefficients de conversion interne et les intensites relatives des differentes transitions ont ete calcules moyennant certaines hypotheses. La comparaison entre les valeurs donnees par la theorie et l'experience des differentes

  9. Prospective study of the 532 nm laser (KTP) versus diode laser 980 nm in the resection of hyperplastic lesions of the oral cavity

    Science.gov (United States)

    Bargiela-Pérez, Patricia; González-Merchán, Jorge; Díaz-Sánchez, Rosa; Serrera-Figallo, Maria-Angeles; Volland, Gerd; Joergens, Martin; Gutiérrez-Pérez, Jose-Luis

    2018-01-01

    Background The aim of this study is to evaluate the resection of hyperplastic lesions on the buccal mucosa comparing the 532nm laser (KTP), versus diode 980nm laser, considering pain, scarring, inflammation and drug consumption that occurred postoperatively with each lasers. Material and Methods A prospective study of consecutive series of 20 patients in two groups that presents hyperplastic lesions on the buccal mucosa. The choice of the KTP laser or diode 980nm laser for the surgery was made randomly. The power used was 1.5W in both groups in a continuous wave mode with a 320 μm optical fiber. Parameters of pain, scarring, inflammation and consumption of drugs were recorded by a Numerical Rating Scale and evaluated postoperatively. These recordings were made the day of the surgery, 24 hours after, 14 and 28 days after. Results Pain and inflammation was light - moderate. The consumption of paracetamol was somewhat higher in the diode 980nm laser versus the KTP laser after 24 hours, although data was not statistically significant; significant differences were found after 28 days in regards to pain (p = 0.023) and inflammation (p = 0.023), but always in the absence parameter so we find no pain in both lasers. Scarring in the two types of laser showed no differences along the visits, with not detected scar retractable. Conclusions Although there is a slight histological difference regarding the KTP laser in the oral soft tissues for clinical use, both wavelengths are very suitable for excision of oral fibroma. Key words:Laser surgery, Laser therapy, oral surgery, soft tissue, 980 nm diode laser, 532 nm KTP laser. PMID:29274158

  10. Study on the effect of thermal property of metals in ultrasonic-assisted laser machining

    International Nuclear Information System (INIS)

    Lee, Hu Seung; Kim, Gun Woo; Park, Jong Eun; Cho, Sung Hak; Yang, Min Yang; Park, Jong Kweon

    2015-01-01

    The laser machining process has been proposed as an advanced process for the selective fabrication of electrodes without a mask. In this study, we adapt laser machining to metals that have different thermal properties. Based on the results, the metals exhibit a different surface morphology, heat-affected zone (HAZ), and a recast layer around the machined surface according to their thermal conductivity, boiling point, and thermal diffusivity. Then, we apply ultrasonic-assisted laser machining to remove the recast layer. The ultrasonic-assisted laser machining exhibits a better surface quality in metals with higher diffusivity than those having lower diffusivity

  11. Study of x-ray emission enhancement via high contrast femtosecond laser interacting with solid foil

    International Nuclear Information System (INIS)

    Chen, Liming; Kando, Masaki; Bulanov, S.V.; Koga, James K.; Tajima, Toshiki; Xu M.H.; Yuan X.H.; Li Y.T.; Dong Q.L.; Zhang J.

    2007-01-01

    We studied the hard x-ray emission and the Kα x-ray conversion efficiency (η K ) produced by 60 fs high contrast frequency doubled Ti: sapphire laser pulse focused on Cu foil target. Cu Kα photon emission obtained with second harmonic laser pulse is more intense than the case of fundamental laser pulse. The Cu η K shows strong dependence on laser nonlinearly skewed pulse shape and reaches the maximum value 4x10 -4 with 100 fs negatively skewed pulse. It shows the electron spectrum shaping contribute to the increase of η K . (author)

  12. Magneto-optical study of the Verwey transition in magnetite

    International Nuclear Information System (INIS)

    Neal, J.R.; Behan, A.J.; Mokhtari, A.; Ahmed, M.R.; Blythe, H.J.; Fox, A.M.; Gehring, G.A.

    2007-01-01

    We have made the first detailed Faraday measurements on thin films of Fe 3 O 4 for 10 xy , which is analysed for the changes in the energy, oscillator strength, and width of the transitions. A significant anomaly is seen in these optical parameters within about 10 K of the Verwey temperature. However, there are also some differences between the optical parameters above and below T v over a wider temperature range. The results are interpreted to give valuable information on the orbital ordering

  13. Modeling and Implementing Nonlinear Equations in Solid-State Lasers for Studying their Performance

    Directory of Open Access Journals (Sweden)

    Ali Roudehghat Shotorbani

    2018-05-01

    Full Text Available In this paper, the effect of radius variation of beam light on output efficacy of SFD Yttrium aluminium borate laser doped with Neodymium ion, which is simultaneously a non-linear and active laser crystal, is investigated in a double-pass cavity. This is done with a concave lens that concentrates (Reduction of optical radius within nonlinear material as much optical laser as possible, resulting in increasing the laser efficiency, second harmonic and the population inversion difference. In this study, we first developed five discrete differential equations describing the interactions of 807 nm pump beam, 1060nm laser beam and 530nm second harmonic beam. Output efficiencies of laser and second harmonic beams at pumping power of Pp =20W and beam radius of 5μm have been presented. Meanwhile, in this paper, the first experiment for creating second harmonic in solid state lasers was fully described with a figure and its procedure was investigated and then the equations (second harmonic and laser and population inversion were studied. Radius variation of beam light aims at increasing laser output efficacy and improving second harmonic and population inversion. The analytic methods which have been solved the discrete differential equations via Matlab.

  14. Design of the study on transitions in employment, ability and motivation (STREAM)

    NARCIS (Netherlands)

    Geuskens, G.A.; Ybema, J.F.; Heuvel, S.G. van den; Wind, A. de; Leijten, M.S.; Joling, C.I.; Blatter, B.M. van; Burdorf, A.; Beek, A.J. van der; Bongers, P.M.

    2013-01-01

    The objective of the Study on Transitions in Employment, Ability and Motivation (STREAM) is to acquire knowledge on determinants of healthy and productive work participation among persons aged 45–64 years. A research framework was developed with main outcomes of productivity and transitions in

  15. Saudi Deaf Students Post-Secondary Transitioning Experience: A Grounded Theory Study

    Science.gov (United States)

    Almotiri, Abdullah

    2017-01-01

    Understanding how deaf and hard-of-hearing (DHH) international students transition to post-secondary institutions is important for ensuring their academic and personal success. In this grounded theory study, five Saudi Arabian students who are DHH and enrolled at Gallaudet University were interviewed about their transition experience. Participants…

  16. Study of the Betatron and Compton X-ray sources produced in laser wakefield acceleration of electrons

    International Nuclear Information System (INIS)

    Ferri, Julien

    2016-01-01

    An ultra-short and ultra-intense laser pulse propagating in a low-density gas can accelerate in its wake a part of the electrons ionized from the gas to relativistic energies of a few hundreds of MeV over distances of a few millimeters only. During their acceleration, as a consequence of their transverse motion, these electrons emit strongly collimated X-rays in the forward direction, which are called betatron radiations. The characteristics of this source turn it into an interesting tool for high-resolution imagery.In this thesis, we explore three different axis to work on this source using simulations on the Particles-In-Cells codes CALDER and CALDER-Circ. We first study the creation of a betatron X-ray source with kilo-joule and pico-second laser pulses, for which duration and energy are then much higher than usual in this domain. In spite of the unusual laser parameters, we show that X-ray sources can still be generated, furthermore in two different regimes.In a second study, the generally observed discrepancies between experiments and simulations are investigated. We show that the use of realistic laser profiles instead of Gaussian ones in the simulations strongly degrades the performances of the laser-plasma accelerator and of the betatron source. Additionally, this leads to a better qualitative and quantitative agreement with the experiment. Finally, with the aim of improving the X-ray emission, we explore several techniques based on the manipulation of the plasma density profile used for acceleration. We find that both the use of a transverse gradient and of a density step increases the amplitude of the electrons transverse motions, and then increases the radiated energy. Alternatively, we show that this goal can also be achieved through the transition from a laser wakefield regime to a plasma wakefield regime induced by an increase of the density. The laser wakefield optimizes the electron acceleration whereas the plasma wakefield favours the X

  17. Infrared diode-laser measurements of some atomic helium (4He I 1s nl) fine-structure transitions: comment

    International Nuclear Information System (INIS)

    Kono, A.

    1987-01-01

    Five recently measured 4 He I transitions involving nS, nP, and nD levels (n = 3--8, Δn = 0,2) are compared with theoretical energy levels having estimated uncertainties that are comparable with those of the experimental results (--10 -3 cm -1 ) [T.J. Sears S. C. Foster, and A. R. W. McKellar, J. Opt. Soc. Am. B3, 1037 (1986)]. The agreement between theory and experiment is generally good, but considerable discrepancy exists for one transition

  18. Laser fusion study. Final report, volume I, study results

    International Nuclear Information System (INIS)

    1975-06-01

    The primary goal of this study was to devise, evaluate, and conceptually design a complete, end-to-end, alignment system capable of handling 30 to 32 Shiva amplifier chains to specified accuracies in space and time. A secondary goal was to accomplish the primary goal with an acceptably low development and procurement cost and with an acceptably high day-after-day performance reliability. This report presents such a system: it is comprised of sensors, actuating mechanisms, controls, and displays that perform well within the current art-state. (U.S.)

  19. The Study Of Optometry Apparatus Of Laser Speckles

    Science.gov (United States)

    Bao-cheng, Wang; Kun, Yao; Xiu-qing, Wu; Chang-ying, Long; Jia-qi, Shi; Shi-zhong, Shi

    1988-01-01

    Based on the regularity of laser speckles movement the method of exam the uncorrected eyes is determined. The apparatus with micro-computer and optical transformation is made. Its practical function is excellent.

  20. Laser ablation/ionization studies in a glow discharge

    International Nuclear Information System (INIS)

    Hess, K.R.; Harrison, W.W.

    1985-01-01

    The pin cathode glow discharge is used in the laboratory as an atomization/ionization source for a variety of applications, including solids mass spectrometry. Coupled with a tunable dye laser, the glow discharge may also serve as an atom reservoir for resonance ionization mass spectrometry in which the laser ionizes the discharge sputtered atoms. By tightly focusing the laser onto solid samples, various ablation effects may also be investigated. The laser may be used to generate an ionized plasma which may be directly analyzed by mass spectrometry. Alternatively, the ablated neutral atoms may be used in post-ablation excitation/ionization processes, in this case the glow discharge. The results of these investigations are the basis of this paper

  1. Laser ablation studies of Deposited Silver Colloids Active in SERS

    International Nuclear Information System (INIS)

    La Porte, R.T.; Moreno, D.S.; Striano, M.C.; Munnoz, M.M.; Garcia-Ramos, J.V.; Cortes, S.S.; Koudoumas, E.

    2002-01-01

    Laser ablation of deposited silver colloids, active in SERS, is carried out at three different laser wavelengths (KrF, XeCl and Nd:YAG at λ = 248, 308 and 532 nm respectively). Emission form excited neutral Ag and Na atoms, present in the ablation plume, is detected with spectral and temporal resolution. The expansion velocity of Ag in the plume is estimated in ∼1x104m s-1, Low-fluence laser ablation of the colloids yields ionized species that are analyzed by time-of-flight mass spectroscopy. Na+ and Agn+(n≤3) are observed. Composition of the mass spectra and widths of the mass peaks are found to be dependent on laser wavelength, suggesting that the dominant ablation mechanisms are different at the different wavelenghts.

  2. Gendered transitions to adulthood by college field of study in the United States

    Directory of Open Access Journals (Sweden)

    Siqi Han

    2016-09-01

    Full Text Available Background: Field of study may influence the timing of transitions to the labor market, marriage, and parenthood among college graduates. Research to date has yet to study how field of study is associated with the interweaving of these transitions in the USA. Objective: The current study examines gendered influences of college field of study on transitions to a series of adult roles, including full-time work, marriage, and parenthood. Methods: We use Cox proportional hazards models and multinomial logistic regression to examine gendered associations between field of study and the three transitions among college graduates of the NLSY97 (National Longitudinal Survey of Youth cohort. Results: Men majoring in STEM achieve early transitions to full-time work, marriage, and parenthood; women majoring in STEM show no significant advantage in finding full-time work and delayed marriage and childbearing; women in business have earlier transitions to full-time work and marriage than women in other fields, demonstrating an advantage similar to that of men in STEM. Conclusions: The contrast between men and women in STEM shows that transition to adulthood remains gendered; the contrast between women in STEM and women in business illustrates that a prestigious career may not necessarily delay family formation. Contribution: The paper shows how stratification by field of study creates gendered demographic outcomes for college graduates. It also demonstrates that women's decisions regarding marriage and parenthood do not uniformly respond to the economic prospect of their work.

  3. Study of geometry angles forming a coaxial nozzle to performance of laser fusion powder composition

    Directory of Open Access Journals (Sweden)

    Павло Васильович Кондрашев

    2017-06-01

    Full Text Available The main purpose of scientific and experimental research, as reflected in this work is the search for solutions and approaches aimed at improving process performance laser alloying powder composition focused laser radiation. Priori information analysis showed the complexity of the process of laser powder fusion tracks from the physical point of view with a lot of technological impacts. Therefore, in this paper we used the method of experimental design, which will allow a more accurate experimental results compared with other methods of research. Based on the experimental screening were identified most significant technological factors influence. These are: powder mass flow, the geometric configuration of the delivery means of powder composition in the area of laser processing, the speed of movement of the substrate. To study the process performance laser alloying powder compositions were applied methods of mathematical statistics, namely, was elected symmetric quasi-D-optimal plan Pisochynskoho for 3 technological factors influence that has good statistical properties and sold regression equation of second order. As a result of the measures was received mathematical model of laser powder fusion focused laser radiation in a second order polynomial. The technique demonstrated the productivity of the process of laser powder fusion focused laser radiation, obtained by using a mathematical model of the process.

  4. Study on the pathogenesis of transient intraocular pressure after laser iridectomy with Krypton laser combined with Q-switched Nd:YAG laser

    Directory of Open Access Journals (Sweden)

    Zhi-Juan Pei

    2017-12-01

    Full Text Available AIM: To study the pathogenesis of transient intraocular pressure(IOPafter laser iridectomy with Krypton laser combined with Q-switched Nd:YAG laser. METHODS: Totally 42 healthy rabbits(84 eyesprovided by the Animal Experimental Center of our hospital were selected, including 18 female rabbits, 24 male rabbits, average weight 2.24±0.31kg, and they were randomly divided into 6 groups, 7 rats in each group(14 eyes. We observed the change of intraocular pressure after laser iridectomy surgery at 20min, 2, 6, 18, 24h and the nitric oxide(NO, malondialdehyde(MDA, superoxide dismutase(SOD, 6-keto-prostaglandin(6-keto-PGF1αand nitric oxide synthase(NOScontent in aqueous. RESULTS: There was no significant difference in intraocular pressure, NO, NOS, SOD, MAD and 6-keto- PGF1α before operation(P>0.05. The intraocular pressure increased after operation, and the difference was statistically significant(PP>0.05. The levels of NO, NOS and SOD in the aqueous humor of the two groups decreased 20min, 2 and 6h after the operation(PP>0.05. The levels of MDA and 6-keto-prostaglandin in the aqueous humor increased after the operation, and the difference was statistically significant at 20min, 2 and 6h after operation(PP>0.05.CONCLUSION: The increase of transient intraocular pressure after laser iridectomy may relate to the increase of malondialdehyde, 6-keto-prostaglandin content and the decrease of superoxide dismutase and nitric oxide in the aqueous humor after operation.

  5. Kinetic studies following state-selective laser excitation

    International Nuclear Information System (INIS)

    Keto, J.W.

    1991-01-01

    During the past year, we have made measurements of state-to-state energy transfer cross sections and radiative lifetimes for Xe*(6p,6p',7p) and Kr*(5p) states in xenon and krypton buffer gases. These results are relevant to kinetic models of both excimer lasers and the infrared xenon laser; and they are a significant improvement in the precision of the known radiative lifetimes. 3 refs., 2 figs., 2 tabs

  6. Experimental study of a laser-heated solenoid

    International Nuclear Information System (INIS)

    Rutkowski, H.L.

    1975-01-01

    An experimental investigation was made of the interaction of an intense CO 2 laser beam with a column of initially uv-ionized hydrogen immersed in a steady magnetic field of up to 100 kG. Under the intense laser radiation, the gas becomes ionized and heated to temperatures as high as 150 eV (1.6 x 10 6 0 K). The primary purpose of the investigation was to determine the properties of the dense, hot plasma formed in this manner. Time and space resolved measurements of the plasma electron density were made using holographic interferometry along the axis and Mach--Zehnder interferometry across the column. The temperature was determined by measuring the decay rate of a line from CV in the quartz uv. These measurements were supplemented by streak photography to provide data on the development of the luminosity of the plasma column, radially and axially, as a function of time. From these various diagnostic techniques, it was possible to determine that a density minimum is formed on-axis within a few tens of nanoseconds after initiation of the laser pulse. This effectively produces a light pipe which traps the beam, and suggests that long columns can be formed by laser irradiation. The beam energy was efficiently absorbed and plasma loss rates appeared to be those expected from classical MHD modelling. While a completely unambiguous answer as to the mode of laser discharge propagation occurring in the experiment was not obtained, the bulk of the evidence suggests a ''bleaching wave'' rather than a laser driven detonator. In summary, the experiment was successful in demonstrating the creation of dense, slender columns by laser breakdown, in support of the ''laser-heated solenoid'' fusion concept

  7. Sun protection behavior and knowledge of patients attending laser clinic to prevent adverse events of laser: A Cross-sectional, Single Center, Tertiary Care Study.

    Science.gov (United States)

    Tempark, Therdpong; Lueangarun, Suparuj; Chatproedprai, Susheera; Panchaprateep, Ratchathorn; Pongprutthipan, Marisa; Wananukul, Siriwan

    2018-06-08

    Limited data of sun protection knowledge in laser treatment patients exists therefore, preventative information should be provided by dermatologists to minimize harmful effects. To assess sun protection knowledge-behavior and knowledge to prevent adverse events from laser therapy among patients who visited a laser clinic at a tertiary university hospital in Bangkok, Thailand. This is a self-reported questionnaire, cross-sectional survey. All participants from the Laser Clinic in KCMH were recruited into the study. A Total of 385 patients were enrolled into the study; 80.5% female participants. Patients who never received laser treatment significantly lacked proper sun protection knowledge to prevent adverse events of lasers when compared to those who previous received laser treatments regarding the application of sunscreen after laser treatment (56.6% vs 17.4%, p protection in the post laser area (41.9% vs 20.4%, p knowledge of sun protection to prevent adverse events were significantly different among the group of educational levels and previous history of laser treatment. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  8. The multi-level perspective analysis: Indonesia geothermal energy transition study

    Science.gov (United States)

    Wisaksono, A.; Murphy, J.; Sharp, J. H.; Younger, P. L.

    2018-01-01

    The study adopts a multi-level perspective in technology transition to analyse how the transition process in the development of geothermal energy in Indonesia is able to compete against the incumbent fossil-fuelled energy sources. Three levels of multi-level perspective are socio-technical landscape (ST-landscape), socio-technical regime (ST-regime) and niche innovations in Indonesia geothermal development. The identification, mapping and analysis of the dynamic relationship between each level are the important pillars of the multi-level perspective framework. The analysis considers the set of rules, actors and controversies that may arise in the technological transition process. The identified geothermal resource risks are the basis of the emerging geothermal technological innovations in Indonesian geothermal. The analysis of this study reveals the transition pathway, which yields a forecast for the Indonesian geothermal technology transition in the form of scenarios and probable impacts.

  9. Ab initio molecular dynamics study of pressure-induced phase transition in ZnS

    International Nuclear Information System (INIS)

    Martinez, Israel; Durandurdu, Murat

    2006-01-01

    The pressure-induced phase transition in zinc sulfide is studied using a constant-pressure ab initio technique. The reversible phase transition from the zinc-blende structure to a rock-salt structure is successfully reproduced through the simulations. The transformation mechanism at the atomistic level is characterized and found to be due to a monoclinic modification of the simulation cell, similar to that obtained in SiC. This observation supports the universal transition state of high-pressure zinc-blende to rock-salt transition in semiconductor compounds. We also study the role of stress deviations on the transformation mechanism and find that the system follows the same transition pathway under nonhydrostatic compressions as well

  10. XPS studies of short pulse laser interaction with copper

    International Nuclear Information System (INIS)

    Stefanov, P.; Minkovski, N.; Balchev, I.; Avramova, I.; Sabotinov, N.; Marinova, Ts.

    2006-01-01

    The effect of laser ablation on copper foil irradiated by a short 30 ns laser pulse was investigated by X-ray photoelectron spectroscopy. The laser fluence was varied from 8 to 16.5 J/cm 2 and the velocity of the laser beam from 10 to 100 mm/s. This range of laser fluence is characterized by a different intensity of laser ablation. The experiments were done in two kinds of ambient atmosphere: air and argon jet gas. The chemical state and composition of the irradiated copper surface were determined using the modified Auger parameter (α') and O/Cu intensity ratio. The ablation atmosphere was found to influence the size and chemical state of the copper particles deposited from the vapor plume. During irradiation in air atmosphere the copper nanoparticles react with oxygen and water vapor from the air and are deposited in the form of a CuO and Cu(OH) 2 thin film. In argon atmosphere the processed copper surface is oxidized after exposure to air

  11. Study on two-color planar laser induced fluorescence thermometry

    International Nuclear Information System (INIS)

    Li Shaodan; Tan Sichao; Gao Puzhen; Lin Yuansheng

    2014-01-01

    Many of the convection heat transfer process are involved in the research of nuclear reactor thermal hydraulics. To experimentally determine the variation of the temperature field in those processes is important for the design and safety operation of the nuclear reactor. The application of the two-color planar laser induced fluorescence (PLIF) in the measurements of fluid temperature distribution is discussed in the paper. The laser dyes used here is rhodamine B (RhB) with negative temperature coefficient and fluorescein 27 (F127) with positive temperature coefficient. The beam of the laser light is adjusted to laser sheet by using the lens group. The fluid with dyes is excited by this laser sheet in a specific plane and temperature dependent fluorescence is released. The temperature field of the plane can be determined through the intensity information. Some technical aspects encountered in the application of the two-laser PLIF are discussed in the paper, such as the spectra characteristic of the dyes and the separation of the spectra. The calibration temperature is higher than the water saturation temperature (at atmosphere pressure). (authors)

  12. Study of laser plasma interactions in the relativistic regime

    International Nuclear Information System (INIS)

    Umstadter, D.

    1997-01-01

    We discuss the first experimental demonstration of electron acceleration by a laser wakefield over instances greater than a Rayleigh range (or the distance a laser normally propagates in vacuum). A self-modulated laser wakefield plasma wave is shown to have a field gradient that exceeds that of an RF linac by four orders of magnitude (E => 200 GV/m) and accelerates electrons with over 1-nC of charge per bunch in a beam with space-charge-limited emittance (1 mm-mrad). Above a laser power threshold, a plasma channel, created by the intense ultrashort laser pulse (I approx. 4 x1018 W/CM2, gamma = 1 micron, r = 400 fs), was found to increase the laser propagation distance, decrease the electron beam divergence, and increase the electron energy. The plasma wave, directly measured with coherent Thomson scattering is shown to damp-due to beam loading-in a duration of 1.5 ps or approx. 100 plasma periods. These results may have important implications for the proposed fast ignitor concept

  13. Technology Transition and Adoption: A Study in Search of Metrics for Evaluating Transition

    Science.gov (United States)

    2010-12-01

    develops a technology on time, within budget, and performs as advertised meets all conventional standards for success. However, if the technology gets...Model-Based Integration of Embedded Software ( MoBIES ) 0 USAF 1 0 0 0 0 76 Project Mobius: A Study on the Feasibility of Learning by Reading 0 0 0 1 0...Engine Generator (MSEG) Program 50 1 0 1,203 0 0 1 75 Model-Based Integration of Embedded Software ( MoBIES ) 45 1 0 1,659 0 0 1 76 Project Mobius: A

  14. Near‐IR laser cleaning of Cu‐ based artefacts: a comprehensive study of the methodology standardization

    DEFF Research Database (Denmark)

    Hrnjic, Mahir

    2015-01-01

    . In this study, laser cleaning was performed with near-IR lasers on artificially aged copper specimens and on two copper coins coming from Bubastis (Egypt) in order to remove the patinas in a totally non invasive way. Different irradiance and different number of passes were utilised and compared. Treated surface...

  15. Numerical study of the properties of optical vortex array laser tweezers.

    Science.gov (United States)

    Kuo, Chun-Fu; Chu, Shu-Chun

    2013-11-04

    Chu et al. constructed a kind of Ince-Gaussian modes (IGM)-based vortex array laser beams consisting of p x p embedded optical vortexes from Ince-Gaussian modes, IG(e)(p,p) modes [Opt. Express 16, 19934 (2008)]. Such an IGM-based vortex array laser beams maintains its vortex array profile during both propagation and focusing, and is applicable to optical tweezers. This study uses the discrete dipole approximation (DDA) method to study the properties of the IGM-based vortex array laser tweezers while it traps dielectric particles. This study calculates the resultant force exerted on the spherical dielectric particles of different sizes situated at the IGM-based vortex array laser beam waist. Numerical results show that the number of trapping spots of a structure light (i.e. IGM-based vortex laser beam), is depended on the relation between the trapped particle size and the structure light beam size. While the trapped particle is small comparing to the beam size of the IGM-based vortex array laser beams, the IGM-based vortex array laser beams tweezers are suitable for multiple traps. Conversely, the tweezers is suitable for single traps. The results of this study is useful to the future development of the vortex array laser tweezers applications.

  16. Study of 2ω and 3/2ω harmonics in ultrashort high-intensity laser ...

    Indian Academy of Sciences (India)

    An experimental study is presented on measurements of optical spectrum of the laser light scattered from solid surface irradiated by Ti:sapphire laser pulses up to an intensity of 1.2 × 1018 W cm-2. The spectrum has well-defined peaks at wavelengths corresponding to 2 and 3/2 radiations. The spectral features vary with ...

  17. Numerical simulation of compressible multiphase flows with or without phase transition. Application to laser plasma interaction; Modelisation et simulation d'ecoulements multiphasiques compressibles avec ou sans changement de phase. Application a l'interaction laser-plasma

    Energy Technology Data Exchange (ETDEWEB)

    Perrier, V

    2007-07-15

    This work deals with the modelling and simulation of compressible flows. A seven equations model is obtained by homogenizing the Euler system. Fluctuation terms are modeled as relaxation terms. When the relaxation terms tend to infinity, which means that the phases are well mixed, a five equations model is obtained via an asymptotic expansion. This five equations model is strictly hyperbolic, but nonconservative. The discretization of this model is obtained by an asymptotic expansion of a scheme for the seven equations model. The numerical method is implemented, validated on analytic cases, and compared with experiments in the case of multiphase shocks. We are then interested in the modelling of phase transition with two equations of state. Optimization of the mixture entropy leads to the fact that three zones can be separated: one in which the pure liquid is the most stable, one in which the pure gas is the most stable, and one in which a mixture with equality of temperature, pressure and chemical potentials is the most stable. Conditions are given on the coupling of the two equations of state for ensuring that the mixture equation of state is convex, and that the system is strictly hyperbolic. In order to take into account phase transition, a vaporization wave is introduced in the solution of the Riemann problem, that is modeled as a deflagration wave. It is then proved that the usual closure, the Chapman-Jouguet closure, is wrong in general, and a correct closure in the case when both fluids have a perfect gas equation of state. Last, the solution of the Riemann problem is implemented in a multiphase code, and validated on analytic cases. In the same code, models of laser release and thermal conduction are implemented to simulate laser ablation. The results are comparable to the ones obtained with scale laws. The last chapter, fully independent, is concerned with correctors in stochastic homogenization in the case of heavy tails process. (author)

  18. Magnetic field effect on the laser-driven density of states for electrons in a cylindrical quantum wire: transition from one-dimensional to zero-dimensional behavior

    International Nuclear Information System (INIS)

    Lima, C P; Lima, F M S; Fonseca, A L A; Nunes, O A C

    2011-01-01

    The influence of a uniform magnetic field on the density of states (DoS) for carriers confined in a cylindrical semiconductor quantum wire irradiated by a monochromatic, linearly polarized, intense laser field is computed here non-perturbatively, following the Green's function scheme introduced by some of the authors in a recent work (Lima et al 2009 Solid State Commun. 149 678). Besides the known changes in the DoS provoked by an intense terahertz laser field-namely, a significant reduction and the appearance of Franz-Keldysh-like oscillations-our model reveals that the inclusion of a longitudinal magnetic field induces additional blueshifts on the energy levels of the allowed states. Our results show that the increase of the blueshifts with the magnitude of the magnetic field depends only on the azimuthal quantum number m (m=0, 1, 2, ...), being more pronounced for states with higher values of m, which leads to some energy crossovers. For all states, we have obtained, even in the absence of a magnetic field, a localization effect that leads to a transition in the DoS from the usual profile of quasi-1D systems to a peaked profile typical of quasi-0D systems, as e.g. those found for electrons confined in a quantum dot.

  19. Feasibility study of multipoint based laser alignment system for CLIC

    CERN Document Server

    Stern, G; Mainaud-Durand, H; Piedigrossi, D; Geiger, A

    2012-01-01

    CLIC (Compact LInear Collider) is a study for a future electron-positron collider that would allow physicists to explore a new energy region beyond the capabilities oftoday’s particle accelerators. Alignment is one of the major challenges within the CLIC study in order to achieve the high requirement of a multi-TeV center of mass colliding beam energy range (nominal 3 TeV). To reach this energy in a realistic and cost efficient scenario all accelerator components have to be aligned with an accuracy of 10 μm over a sliding window of 200 m. The demand for a straight line reference is so far based on stretched wires coupled with Wire Positioning Sensors (WPS). These solutions are currently further developed inorder to reduce the drawbacks which are mainly given by their costs and difficult implementation. However, it should be validated through inter-comparison with a solution ideally based on a different physical principle. Therefore, a new metrological approach is proposed using a laser beam as straight lin...

  20. Study of Material Consolidation at Higher Throughput Parameters in Selective Laser Melting of Inconel 718

    Science.gov (United States)

    Prater, Tracie

    2016-01-01

    Selective Laser Melting (SLM) is a powder bed fusion additive manufacturing process used increasingly in the aerospace industry to reduce the cost, weight, and fabrication time for complex propulsion components. SLM stands poised to revolutionize propulsion manufacturing, but there are a number of technical questions that must be addressed in order to achieve rapid, efficient fabrication and ensure adequate performance of parts manufactured using this process in safety-critical flight applications. Previous optimization studies for SLM using the Concept Laser M1 and M2 machines at NASA Marshall Space Flight Center have centered on machine default parameters. The objective of this work is to characterize the impact of higher throughput parameters (a previously unexplored region of the manufacturing operating envelope for this application) on material consolidation. In phase I of this work, density blocks were analyzed to explore the relationship between build parameters (laser power, scan speed, hatch spacing, and layer thickness) and material consolidation (assessed in terms of as-built density and porosity). Phase II additionally considers the impact of post-processing, specifically hot isostatic pressing and heat treatment, as well as deposition pattern on material consolidation in the same higher energy parameter regime considered in the phase I work. Density and microstructure represent the "first-gate" metrics for determining the adequacy of the SLM process in this parameter range and, as a critical initial indicator of material quality, will factor into a follow-on DOE that assesses the impact of these parameters on mechanical properties. This work will contribute to creating a knowledge base (understanding material behavior in all ranges of the AM equipment operating envelope) that is critical to transitioning AM from the custom low rate production sphere it currently occupies to the world of mass high rate production, where parts are fabricated at a rapid

  1. Gendered transitions to adulthood by college field of study in the United States.

    Science.gov (United States)

    Han, Siqi; Tumin, Dmitry; Qian, Zhenchao

    2016-01-01

    Field of study may influence the timing of transitions to the labor market, marriage, and parenthood among college graduates. Research to date has yet to study how field of study is associated with the interweaving of these transitions in the USA. The current study examines gendered influences of college field of study on transitions to a series of adult roles, including full-time work, marriage, and parenthood. We use Cox proportional hazards models and multinomial logistic regression to examine gendered associations between field of study and the three transitions among college graduates of the NLSY97 (National Longitudinal Survey of Youth) cohort. Men majoring in STEM achieve early transitions to full-time work, marriage, and parenthood; women majoring in STEM show no significant advantage in finding full-time work and delayed marriage and childbearing; women in business have earlier transitions to full-time work and marriage than women in other fields, demonstrating an advantage similar to that of men in STEM. The contrast between men and women in STEM shows that transition to adulthood remains gendered; the contrast between women in STEM and women in business illustrates that a prestigious career may not necessarily delay family formation.

  2. Gendered transitions to adulthood by college field of study in the United States

    Science.gov (United States)

    Han, Siqi; Tumin, Dmitry; Qian, Zhenchao

    2017-01-01

    BACKGROUND Field of study may influence the timing of transitions to the labor market, marriage, and parenthood among college graduates. Research to date has yet to study how field of study is associated with the interweaving of these transitions in the USA. OBJECTIVE The current study examines gendered influences of college field of study on transitions to a series of adult roles, including full-time work, marriage, and parenthood. METHODS We use Cox proportional hazards models and multinomial logistic regression to examine gendered associations between field of study and the three transitions among college graduates of the NLSY97 (National Longitudinal Survey of Youth) cohort. RESULTS Men majoring in STEM achieve early transitions to full-time work, marriage, and parenthood; women majoring in STEM show no significant advantage in finding full-time work and delayed marriage and childbearing; women in business have earlier transitions to full-time work and marriage than women in other fields, demonstrating an advantage similar to that of men in STEM. CONCLUSIONS The contrast between men and women in STEM shows that transition to adulthood remains gendered; the contrast between women in STEM and women in business illustrates that a prestigious career may not necessarily delay family formation. PMID:29075146

  3. Numerical and experimental study on multi-pass laser bending of AH36 steel strips

    Science.gov (United States)

    Fetene, Besufekad N.; Kumar, Vikash; Dixit, Uday S.; Echempati, Raghu

    2018-02-01

    Laser bending is a process of bending of plates, small sized sheets, strips and tubes, in which a moving or stationary laser beam heats the workpiece to achieve the desired curvature due to thermal stresses. Researchers studied the effects of different process parameters related to the laser source, material and workpiece geometry on laser bending of metal sheets. The studies are focused on large sized sheets. The workpiece geometry parameters like sheet thickness, length and width also affect the bend angle considerably. In this work, the effects of width and thickness on multi-pass laser bending of AH36 steel strips were studied experimentally and numerically. Finite element model using ABAQUS® was developed to investigate the size effect on the prediction of the bend angle. Microhardness and flexure tests showed an increase in the flexural strength as well as microhardness in the scanned zone. The microstructures of the bent strips also supported the physical observations.

  4. A feasibility study of a linear laser heated solenoid fusion reactor. Final report

    International Nuclear Information System (INIS)

    Steinhauer, L.C.

    1976-02-01

    This report examines the feasibility of a laser heated solenoid as a fusion or fusion-fission reactor system. The objective of this study, was an assessment of the laser heated solenoid reactor concept in terms of its plasma physics, engineering design, and commercial feasibility. Within the study many pertinent reactor aspects were treated including: physics of the laser-plasma interaction; thermonuclear behavior of a slender plasma column; end-losses under reactor conditions; design of a modular first wall, a hybrid (both superconducting and normal) magnet, a large CO 2 laser system; reactor blanket; electrical storage elements; neutronics; radiation damage, and tritium processing. Self-consistent reactor configurations were developed for both pure fusion and fusion-fission designs, with the latter designed both to produce power and/or fissile fuels for conventional fission reactors. Appendix A is a bibliography with commentary of theoretical and experimental studies that have been directed at the laser heated solenoid

  5. High Precision Renormalization Group Study of the Roughening Transition

    CERN Document Server

    Hasenbusch, M; Pinn, K

    1994-01-01

    We confirm the Kosterlitz-Thouless scenario of the roughening transition for three different Solid-On-Solid models: the Discrete Gaussian model, the Absolute-Value-Solid-On-Solid model and the dual transform of the XY model with standard (cosine) action. The method is based on a matching of the renormalization group flow of the candidate models with the flow of a bona fide KT model, the exactly solvable BCSOS model. The Monte Carlo simulations are performed using efficient cluster algorithms. We obtain high precision estimates for the critical couplings and other non-universal quantities. For the XY model with cosine action our critical coupling estimate is $\\beta_R^{XY}=1.1197(5)$. For the roughening coupling of the Discrete Gaussian and the Absolute-Value-Solid-On-Solid model we find $K_R^{DG}=0.6645(6)$ and $K_R^{ASOS}=0.8061(3)$, respectively.

  6. Magneto-optical study of the Verwey transition in magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Neal, J.R. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Behan, A.J. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Mokhtari, A. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Ahmed, M.R. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Blythe, H.J. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Fox, A.M. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Gehring, G.A. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)]. E-mail: G.A.Gehring@Sheffield.ac.uk

    2007-03-15

    We have made the first detailed Faraday measurements on thin films of Fe{sub 3}O{sub 4} for 10transitions. A significant anomaly is seen in these optical parameters within about 10 K of the Verwey temperature. However, there are also some differences between the optical parameters above and below T {sub v} over a wider temperature range. The results are interpreted to give valuable information on the orbital ordering.

  7. Transitional lumbosacral vertebral anomaly in the dog: a radiographic study

    International Nuclear Information System (INIS)

    Morgan, J.P.

    1999-01-01

    Transitional lumbosacral vertebral anomalies have for some time been suggested as a possible cause of cauda equina syndrome (especially in the German shepherd dog [GSD]), a condition recently thought to be inherited. The frequency of this condition within a large clinical population and the radiographic features used in its detection are reported. In a group of 143 patients, the sexes were similarly represented and the GSD was greatly over represented. The anomaly is characterised by separation of the first sacral segment that was identified on the lateral view by the presence of a radiolucent disc space between what are normally the first and second sacral segments. On the ventrodorsal view, the anomaly was characterised by separation of the spinous processes between what are normally the first and second sacral segments. In the presence of the transitional segment, the nature of the sacroiliac joint at the level of the anomalous segment varies from a strong ilial attachment, with the presence of a wing-like lateral process, to a weakened ilial attachment because of the presence of a lateral process, shaped as that seen on a lumbar segment. These patterns were present unilaterally or bilaterally and result in symmetrical or asymmetrical patterns. The effect of the weakening of the sacroiliac attachment was thought to result in premature disc degeneration, which, together with spinal canal stenosis, resulted in potential compression of the overlying spinal nerves and creation of a cauda equina syndrome. The condition is thought to have clinical significance and should be selected against in breeding, especially in the GSD

  8. Comparative Evaluation of Effects of Laser Modalities on Shear Bond Strengths of Veneering Porcelains to Laser Sintered Substructures: An In Vitro Study.

    Science.gov (United States)

    Gorler, Oguzhan; Saygin, Aysegul Goze

    2017-06-01

    Laser modalities and direct metal laser sintering (DMLS) have a potential to enhance micromechanical bonding between dental super- and infrastructures. However, the effect of different manufacturing methods on the metal-ceramic bond strength needs further evaluation. We investigated the effect of surface treatment with Er:YAG, Nd:YAG, and Ho:YAG lasers on the shear bond strength (SBS) of high-fusion dental porcelains (Vita and G-Ceram) to infrastructures prepared with DMLS in vitro settings. Study specimens (n = 128) were randomly divided into study subsets (n = 8), considering treatment types applied on the surface of infrastructures, including sandblasting and selected laser modalities; infrastructure types as direct laser sintered (DLS) and Ni-Cr based; and superstructure porcelains as Vita and G-Ceram. The SBS test was performed to assess the effectiveness of surface modifications that were also examined with a stereo microscope. Considering laser procedure types, the highest SBS values were obtained by Er:YAG laser, followed by, with a decreasing efficiency, Ho:YAG laser and sandblasting procedures, and Nd:YAG laser procedure (p laser decreases the bonding of Vita and G-Ceram in all the infrastructures compared with sandblasting. Considering porcelains, the highest SBS values were obtained by Vita (p laser procedures caused surface irregularities as revealed by the stereo microscopic examination. In current experimental settings, Er:YAG laser applied to DLS infrastructure veneered with Vita porcelain increases bonding strength more distinctly, and Nd:YAG laser applied to Ni-Cr-based infrastructure veneered with G-Ceram porcelain alters bonding strength unfavorably.

  9. Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study

    Science.gov (United States)

    Popescu-Pelin, G.; Sima, F.; Sima, L. E.; Mihailescu, C. N.; Luculescu, C.; Iordache, I.; Socol, M.; Socol, G.; Mihailescu, I. N.

    2017-10-01

    Pulsed Laser Deposition (PLD) and Matrix Assisted Pulsed Laser Evaporation (MAPLE) techniques were applied for growing hydroxyapatite (HA) thin films on titanium substrates. All experiments were conducted in a reaction chamber using a KrF* excimer laser source (λ = 248 nm, τFWHM ≈ 25 ns). Half of the samples were post-deposition thermally treated at 500 °C in a flux of water vapours in order to restore crystallinity and improve adherence. Coating surface morphologies and topographies specific to the deposition method were evidenced by scanning electron, atomic force microscopy investigations and profilometry. They were shown to depend on deposition technique and also on the post-deposition treatment. Crystalline structure of the coatings evaluated by X-ray diffraction was improved after thermal treatment. Biocompatibility of coatings, cellular adhesion, proliferation and differentiation tests were conducted using human mesenchymal stem cells (MSCs). Results showed that annealed MAPLE deposited HA coatings were supporting MSCs proliferation, while annealed PLD obtained films were stimulating osteogenic differentiation.

  10. Pressure-induced α->ω transition in titanium metal: a systematic study of the effects of uniaxial stress

    International Nuclear Information System (INIS)

    Errandonea, Daniel; Meng, Y.; Somayazulu, M.; Haeusermann, D.

    2005-01-01

    The effects of uniaxial stress on the pressure-induced α->ω transition in pure titanium (Ti) are investigated by means of angle dispersive X-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9GPa (no pressure medium) to 10.5GPa (argon pressure medium); (2) the α and ω phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the ω phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the α->ω transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrate the influence of uniaxial stress in the α->ω transition

  11. Laser Stabilization with Laser Cooled Strontium

    DEFF Research Database (Denmark)

    Christensen, Bjarke Takashi Røjle

    The frequency stability of current state-of-the-art stabilized clock lasers are limited by thermal fluctuations of the ultra-stable optical reference cavities used for their frequency stabilization. In this work, we study the possibilities for surpassing this thermal limit by exploiting the nonli......The frequency stability of current state-of-the-art stabilized clock lasers are limited by thermal fluctuations of the ultra-stable optical reference cavities used for their frequency stabilization. In this work, we study the possibilities for surpassing this thermal limit by exploiting...... the nonlinear effects from coupling of an optical cavity to laser cooled atoms having a narrow transition linewidth. Here, we have realized such a system where a thermal sample of laser cooled strontium-88 atoms are coupled to an optical cavity. The strontium-88 atoms were probed on the narrow 1S0-3P1 inter......-combination line at 689 nm in a strongly saturated regime. The dynamics of the atomic induced phase shift and absorption of the probe light were experimentally studied in details with the purpose of applications to laser stabilization. The atomic sample temperature was in the mK range which brought this system out...

  12. Fractional CO2 laser treatment for vaginal laxity: A preclinical study.

    Science.gov (United States)

    Kwon, Tae-Rin; Kim, Jong Hwan; Seok, Joon; Kim, Jae Min; Bak, Dong-Ho; Choi, Mi-Ji; Mun, Seok Kyun; Kim, Chan Woong; Ahn, Seungwon; Kim, Beom Joon

    2018-05-07

    Various studies have investigated treatment for vaginal laxity with microablative fractional carbon dioxide CO 2 laser in humans; however, this treatment has not yet been studied in an animal model. Herein, we evaluate the therapeutic effects of fractional CO 2 laser for tissue remodeling of vaginal mucosa using a porcine model, with the aim of improving vaginal laxity. The fractional CO 2 laser enables minimally invasive and non-incisional procedures. By precisely controlling the laser energy pulses, energy is sent to the vaginal canal and the introitus area to induce thermal denaturation and contraction of collagen. We examined the effects of fractional CO 2 laser on a porcine model via clinical observation and ultrasound measurement. Also, thermal lesions were histologically examined via hematoxylin-eosin staining, Masson's trichrome staining, and Elastica van Gieson staining and immunohistochemistry. The three treatment groups, which were determined according to the amount of laser-energy applied (60, 90, and 120 mJ), showed slight thermal denaturation in the vaginal mucosa, but no abnormal reactions, such as excessive hemorrhaging, vesicles, or erythema, were observed. Histologically, we also confirmed that the denatured lamina propria induced by fractional CO 2 laser was dose-dependently increased after laser treatment. The treatment groups also showed an increase in collagen and elastic fibers due to neocollagenesis and angiogenesis, and the vaginal walls became firmer and tighter because of increased capillary and vessel formation. Also, use of the fractional CO 2 laser increased HSP (heat shock protein) 70 and collagen type I synthesis. Our results show that microablative fractional CO 2 laser can produce remodeling of the vaginal connective tissue without causing damage to surrounding tissue, and the process of mucosa remodeling while under wound dressings enables collagen to increase and the vaginal wall to become thick and tightened. Lasers Surg. Med

  13. Studies of harmonic generation in free electron lasers

    International Nuclear Information System (INIS)

    Goldammer, K.

    2007-01-01

    Nonlinear harmonic generation is one of the most interesting aspects of Free Electron Lasers under study today. It provides for coherent, high intensity radiation at higher harmonics of the FEL resonant frequency. The sources, numerical simulation and applications of harmonic radiation in cascaded High Gain Harmonic Generation FELs were the subject of this thesis. Harmonic emission in FELs originates from harmonic microbunching of the particles and the particular electron trajectory during FEL interaction. Numerical FEL simulation codes model these analytical equations and predict the performance of Free Electron Lasers with good accuracy. This thesis has relied heavily upon the FEL simulation code Genesis 1.3 which has been upgraded in the framework of this thesis to compute harmonic generation in a self-consistent manner. Tests against analytical predictions suggest that the harmonic power levels as well as harmonic gain lengths are simulated correctly. A benchmark with the FEL simulation code GINGER yields excellent agreement of the harmonic saturation length and saturation power. The new version of the simulation code Genesis was also tested against measurements from the VUV-FEL FLASH at DESY. The spectral power distributions of fundamental and third harmonic radiation were recorded at 25.9 nm and 8.6 nm, respectively. The relative bandwidths (FWHM) were in the range of 2 % for both the fundamental as well as the third harmonic, which was accurately reproduced by time-dependent simulations with Genesis. The new code was also used to propose and evaluate a new design for the BESSY Soft X-Ray FEL, a cascaded High Gain Harmonic Generation FEL proposed by BESSY in Berlin. The original design for the BESSY High Energy FEL line requires four HGHG stages to convert the initial seed laser wavelength of 297.5 nm down to 1.24 nm. A new scheme is proposed that makes use of fifth harmonic radiation from the first stage and reduces the number of HGHG stages to three. It

  14. Studies of harmonic generation in free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Goldammer, K.

    2007-11-12

    Nonlinear harmonic generation is one of the most interesting aspects of Free Electron Lasers under study today. It provides for coherent, high intensity radiation at higher harmonics of the FEL resonant frequency. The sources, numerical simulation and applications of harmonic radiation in cascaded High Gain Harmonic Generation FELs were the subject of this thesis. Harmonic emission in FELs originates from harmonic microbunching of the particles and the particular electron trajectory during FEL interaction. Numerical FEL simulation codes model these analytical equations and predict the performance of Free Electron Lasers with good accuracy. This thesis has relied heavily upon the FEL simulation code Genesis 1.3 which has been upgraded in the framework of this thesis to compute harmonic generation in a self-consistent manner. Tests against analytical predictions suggest that the harmonic power levels as well as harmonic gain lengths are simulated correctly. A benchmark with the FEL simulation code GINGER yields excellent agreement of the harmonic saturation length and saturation power. The new version of the simulation code Genesis was also tested against measurements from the VUV-FEL FLASH at DESY. The spectral power distributions of fundamental and third harmonic radiation were recorded at 25.9 nm and 8.6 nm, respectively. The relative bandwidths (FWHM) were in the range of 2 % for both the fundamental as well as the third harmonic, which was accurately reproduced by time-dependent simulations with Genesis. The new code was also used to propose and evaluate a new design for the BESSY Soft X-Ray FEL, a cascaded High Gain Harmonic Generation FEL proposed by BESSY in Berlin. The original design for the BESSY High Energy FEL line requires four HGHG stages to convert the initial seed laser wavelength of 297.5 nm down to 1.24 nm. A new scheme is proposed that makes use of fifth harmonic radiation from the first stage and reduces the number of HGHG stages to three. It

  15. Multiple and multidimensional transitions from trainee to trained doctor: a qualitative longitudinal study in the UK.

    Science.gov (United States)

    Gordon, Lisi; Jindal-Snape, Divya; Morrison, Jill; Muldoon, Janine; Needham, Gillian; Siebert, Sabina; Rees, Charlotte

    2017-12-01

    To explore trainee doctors' experiences of the transition to trained doctor, we answer three questions: (1) What multiple and multidimensional transitions (MMTs) are experienced as participants move from trainee to trained doctor? (2) What facilitates and hinders doctors' successful transition experiences? (3) What is the impact of MMTs on trained doctors? A qualitative longitudinal study underpinned by MMT theory. Four training areas (health boards) in the UK. 20 doctors, 19 higher-stage trainees within 6 months of completing their postgraduate training and 1 staff grade, associate specialist or specialty doctor, were recruited to the 9-month longitudinal audio-diary (LAD) study. All completed an entrance interview, 18 completed LADs and 18 completed exit interviews. Data were analysed cross-sectionally and longitudinally using thematic Framework Analysis. Participants experienced a multiplicity of expected and unexpected, positive and negative work-related transitions (eg, new roles) and home-related transitions (eg, moving home) during their trainee-trained doctor transition. Factors facilitating or inhibiting successful transitions were identified at various levels: individual (eg, living arrangements), interpersonal (eg, presence of supportive relationships), systemic (eg, mentoring opportunities) and macro (eg, the curriculum provided by Medical Royal Colleges). Various impacts of transitions were also identified at each of these four levels: individual (eg, stress), interpersonal (eg, trainees' children spending more time in childcare), systemic (eg, spending less time with patients) and macro (eg, delayed start in trainees' new roles). Priority should be given to developing supportive relationships (both formal and informal) to help trainees transition into their trained doctor roles, as well as providing more opportunities for learning. Further longitudinal qualitative research is now needed with a longer study duration to explore transition journeys for

  16. Energy transitions in France: lessons learned from prospective studies. Contribution to the National Debate on Energy Transition

    International Nuclear Information System (INIS)

    Bibas, Ruben; Hourcade, Jean-Charles

    2013-01-01

    After having outlined that the debates on energy transition in France focus on three main issues (management of greenhouse gas emissions, future of nuclear within the French energy mix, energy security), the authors report the use of the Imaclim-R France model (a multi-sector recursive hybrid model) which is adapted to sensitivity studies for the whole set of hypotheses. As energy parameters, they use data provided by ENCILOWCARB scenarios from a European project (Engaging civil society in low carbon scenarios). After having examined that they are not sufficient to conduct a transition strategy leading to a F4 pathway of reduction of greenhouse gas emissions and/or a progressive phasing out nuclear, they consider the policies which are necessary to mobilise potentials of energy saving and emission reduction. Several scenarios are studied in terms of energy and environmental performances and in terms of economic and social performances: scenarios based on policies and measures with or without additional component (carbon tax, social negotiation, carbon finance)

  17. A study of the static to kinetic friction transition of polymers

    OpenAIRE

    Lee, Edward Chungjen

    1995-01-01

    This study investigates the transition from static to kinetic friction for structural polymers and continues previous research conducted by Dr. N. S. Eiss, B. McCann, and R. Molique. A new test apparatus which simultaneously measures friction, normal load, and relative velocity was developed to study this transition. The polymers used in this study were nylon, ABS, polycarbonate, and fiberglass filled and unfilled polypropylene. Creep effects of polymers on the static coefficie...

  18. A computational study of pressure-induced structural transition in ThSb

    International Nuclear Information System (INIS)

    Trinadh, Ch.U.M.; Rajagopalan, M.; Natarajan, S.

    1997-01-01

    The pressure induced phase transition from NaCl-type to CsCl-type structure in ThSb was studied using total energy calculations by tight-binding linear muffin tin orbital (TBLMTO) method within atomic sphere approximation (ASA). The density of states (DOS) at ambient pressure was compared with resonant photoemission studies (PES). The variation in interatomic distances during the transition was found to be in agreement with high pressure x-ray diffraction (HPXRD) studies. (author)

  19. NATO Advanced Study Institute on Physics of New Laser Sources

    CERN Document Server

    Arecchi, F; Mooradian, Aram; Sona, Alberto

    1985-01-01

    This volume contains the lectures and seminars presented at the NATO Advanced Study Institute on "Physics of New Laser Sources", the twelfth course of the Europhysics School of Quantum Electronics, held under the supervision of the Quantum Electronics Division of the European Physical Society. The Institute was held at Centro "I Cappuccini" San Miniato, Tuscany, July 11-21, 1984. The Europhysics School of Quantum Electronics was started in 1970 with the aim of providing instruction for young researchers and advanced students already engaged in the area of quantum electronics or for those wishing to switch into this area after working previously in other areas. From the outset, the School has been under the direction of Prof. F. T. Arecchi, then at the University of Pavia, now at the University of Florence, and Dr. D. Roess of Heraeus, Hanau. In 1981, Prof. H. Walther, University of Munich and Max-Planck Institut fur Quantenoptik joined as co-director. Each year the Directors choose a subj~ct of particular int...

  20. Theoretical study on the thermal and optical features of a diode side-pumped alkali laser

    Science.gov (United States)

    Han, Juhong; Liu, Xiaoxu; Wang, Hongyuan; Cai, He; An, Guofei; Zhang, Wei; Wang, You

    2018-03-01

    As one of the most hopeful candidates to achieve high power performances, a diode-pumped alkali laser (DPAL) has attracted a lot of attention in the last decade. Comparing with a diode end-pumped alkali laser (DEPAL), a diode side-pumped alkali laser (DSPAL) has great potentiality to realize an even-higher output of alkali lasers. However, there are few related researching studies concern DSPAL. In this paper, we introduce a theoretical model to investigate the physical features of a double-directions side-pumped alkali laser. The distributions of the population density, temperature, and absorption power at the cross section of a vapor cell are systematically studied. The analyses should be valuable for design of a steady high-powered DPAL.