WorldWideScience

Sample records for extremely short pulses

  1. Peculiarities of the propagation of multidimensional extremely short optical pulses in germanene

    Science.gov (United States)

    Zhukov, Alexander V.; Bouffanais, Roland; Konobeeva, Natalia N.; Belonenko, Mikhail B.

    2016-09-01

    In this Letter, we study the propagation characteristics of both two-dimensional and three-dimensional extremely short optical pulses in germanene. A distinguishing feature of germanene-in comparison with other graphene-like structures-is the presence of a significant spin-orbit interaction. The account of this interaction has a significant impact on the evolution of extremely short pulses in such systems. Specifically, extremely short optical pulses, consisting of two electric field oscillations, cause the appearance of a tail associated with the excitation of nonlinear waves. Due to the large spin-orbit interaction in germanene, this tail behind the main pulse is much smaller in germanene-based samples as compared to graphene-based ones, thereby making germanene a preferred material for the stable propagation of pulses along the sample.

  2. Peculiarities of the propagation of multidimensional extremely short optical pulses in germanene

    Energy Technology Data Exchange (ETDEWEB)

    Zhukov, Alexander V., E-mail: alex_zhukov@sutd.edu.sg [Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore (Singapore); Bouffanais, Roland [Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore (Singapore); Konobeeva, Natalia N. [Volgograd State University, 400062 Volgograd (Russian Federation); Belonenko, Mikhail B. [Laboratory of Nanotechnology, Volgograd Institute of Business, 400048 Volgograd (Russian Federation); Volgograd State University, 400062 Volgograd (Russian Federation)

    2016-09-07

    Highlights: • Established dynamics of ultra-short pulses in germanene. • Studied balance between dispersive and nonlinear effects in germanene. • Spin–orbit interaction effect onto pulse propagation. - Abstract: In this Letter, we study the propagation characteristics of both two-dimensional and three-dimensional extremely short optical pulses in germanene. A distinguishing feature of germanene—in comparison with other graphene-like structures—is the presence of a significant spin–orbit interaction. The account of this interaction has a significant impact on the evolution of extremely short pulses in such systems. Specifically, extremely short optical pulses, consisting of two electric field oscillations, cause the appearance of a tail associated with the excitation of nonlinear waves. Due to the large spin–orbit interaction in germanene, this tail behind the main pulse is much smaller in germanene-based samples as compared to graphene-based ones, thereby making germanene a preferred material for the stable propagation of pulses along the sample.

  3. Formation and erasure of population difference gratings in the coherent interaction of a resonant medium with extremely short optical pulses

    Science.gov (United States)

    Arkhipov, R. M.; Arkhipov, M. V.; Babushkin, I.; Rosanov, N. N.

    2016-11-01

    In the regime of coherent interaction of short optical pulses with a resonant medium, which is implemented with a pulse duration shorter than the relaxation times in the medium, the formation of population gratings can occur without overlapping the pulses therein. In this case, there are new possibilities for controlling optical pulses, which are especially pronounced for extremely short pulses. It is shown that, with the proper choice of the parameters of a sequence of extremely short optical pulses, not only the formation of population gratings, but also their erasure are possible. It is demonstrated that this effect can be used for the creation of an ultrahigh-speed optical deflector.

  4. Reduced Maxwell-Duffing description of extremely short pulses in nonresonant media.

    Science.gov (United States)

    Kazantseva, Elena V; Maimistov, Andrei I; Caputo, Jean-Guy

    2005-05-01

    The propagation of extremely short pulses of an electromagnetic field (electromagnetic spikes) is considered in the framework of a model wherein the material medium is represented by anharmonic oscillators with cubic nonlinearities (Duffing model) and waves can propagate only in the right direction. The system of reduced Maxwell-Duffing equations admits two families of exact analytical solutions in the form of solitary waves. These are bright spikes propagating on a zero background, and bright and dark spikes propagating on a nonzero background. We find that these steady-state pulses are stable in terms of boundedness of the Hamiltonian. Direct simulations demonstrate that these pulses are very robust against perturbations. We find that a high-frequency modulated electromagnetic pulse evolves into a breather-like one. Conversely, a low frequency pulse transforms into a quasiharmonic wave.

  5. Nonlinear propagation of vector extremely short pulses in a medium of symmetric and asymmetric molecules

    Energy Technology Data Exchange (ETDEWEB)

    Sazonov, S. V., E-mail: sazonov.sergey@gmail.com [National Research Centre “Kurchatov Institute,” (Russian Federation); Ustinov, N. V., E-mail: n-ustinov@mail.ru [Moscow State University of Railways, Kaliningrad Branch (Russian Federation)

    2017-02-15

    The nonlinear propagation of extremely short electromagnetic pulses in a medium of symmetric and asymmetric molecules placed in static magnetic and electric fields is theoretically studied. Asymmetric molecules differ in that they have nonzero permanent dipole moments in stationary quantum states. A system of wave equations is derived for the ordinary and extraordinary components of pulses. It is shown that this system can be reduced in some cases to a system of coupled Ostrovsky equations and to the equation intagrable by the method for an inverse scattering transformation, including the vector version of the Ostrovsky–Vakhnenko equation. Different types of solutions of this system are considered. Only solutions representing the superposition of periodic solutions are single-valued, whereas soliton and breather solutions are multivalued.

  6. Three-dimensional extremely-short optical pulses in carbon nanotube arrays in the presence of an external magnetic field

    Science.gov (United States)

    Zhukov, Alexander V.; Bouffanais, Roland; Belonenko, Mikhail B.; Galkina, Elena N.

    2016-12-01

    In this paper, we study the behavior of three-dimensional extremely-short optical pulses propagating in a system made of carbon nanotubes in the presence of an external magnetic field applied perpendicular both to the nanotube axis and to the direction of propagation of the pulse. The evolution of the electromagnetic field is classically derived on the basis of the Maxwell’s equations. The electronic system of carbon nanotubes is considered in the low-temperature approximation. Our analysis reveals the novel and unique ability of controlling the shape of propagating short optical pulses by tuning the intensity of the applied magnetic field. This effect paves the way for the possible development of innovative applications in optoelectronics.

  7. The Description of Extremely Short Pulses in Non-Resonant Media in Frame of Maxwell-Duffing-Type Models

    Science.gov (United States)

    Kazantseva, Elena V.

    The propagation of extremely short pulses of electromagnetic field (electromagnetic spikes) is considered in the framework of a model where the material medium is represented by anharmonic oscillators with cubic nonlinearities (Duffing model) and waves can propagate in both directions. The system of total Maxwell-Duffing equations admits two families of exact analytical solutions in the form of solitary waves. The single-cycle electromagnetic pulse propagation in a medium whose dispersion and nonlinear properties are described by the cubic-quintic Duffing model (oscillator with third- and fifth-order anharmonicity). A system of equations governing the evolution of a unidirectional electromagnetic wave is analyzed without using the approximation of slowly varying envelopes. Three types of solutions of this system describing stationary propagation of a pulse in such a medium are found. When the signs of the anharmonicity constants are different, the amplitude of a steady-state pulse is limited, but its energy may grow on account of an increase in its duration.

  8. Exact Solutions to Short Pulse Equation

    Institute of Scientific and Technical Information of China (English)

    FU Zun-Tao; ZHENG Ming-Hua; LIU Shi-Kuo

    2009-01-01

    In this paper, dependent and independent variable transformations are introduced to solve the short pulse equation. It is shown that different kinds of solutions can be obtained to the short pulse equation.

  9. Ion Acceleration by Short Chirped Laser Pulses

    Directory of Open Access Journals (Sweden)

    Jian-Xing Li

    2015-02-01

    Full Text Available Direct laser acceleration of ions by short frequency chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1% can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies in the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e., higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

  10. Ion Acceleration by Short Chirped Laser Pulses

    CERN Document Server

    Li, Jian-Xing; Keitel, Christoph H; Harman, Zoltán

    2015-01-01

    Direct laser acceleration of ions by short frequency-chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1 % can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies of the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e. higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

  11. Subthreshold pair production in short laser pulses

    OpenAIRE

    Nousch, T.; Seipt, D.; Kampfer, B.; Titov, A. I.

    2012-01-01

    The $e^+e^-$ pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit-Wheeler process. For short laser pulses with very few oscillations of the electromagnetic field we find below the perturbative weak-field threshold $\\sqrt{s} = 2m$ a similar enhancement of the pair production rate as for circular polarization. The strong subthreshold enhancement is traced back to the finite bandwidth of the laser pulse. A folding model is develo...

  12. Subthreshold pair production in short laser pulses

    CERN Document Server

    Nousch, T; Kampfer, B; Titov, A I

    2012-01-01

    The $e^+e^-$ pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit-Wheeler process. For short laser pulses with very few oscillations of the electromagnetic field we find below the perturbative weak-field threshold $\\sqrt{s} = 2m$ a similar enhancement of the pair production rate as for circular polarization. The strong subthreshold enhancement is traced back to the finite bandwidth of the laser pulse. A folding model is developed which accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.

  13. Ultra short pulse reconstruction software: GROG

    Science.gov (United States)

    Galletti, M.; Galimberti, M.; Giulietti, D.; Curcio, A.

    2016-07-01

    A new algorithmic method based on the 1D Conjugate Gradient Minimization Method, is presented. The purpose is, analyzing experimental FROG/GRENOUILLE traces, to accurately retrieve intensity and phase both in temporal and spectral domain so as to completely characterize an Ultra Short High Power laser pulse. This algorithm shows important features in the reconstruction of many different pulse classes. The employment of this algorithm also permits the inclusion of material response function present in the FROG/GRENOUILLE set-up.

  14. Short pulse laser systems for biomedical applications

    CERN Document Server

    Mitra, Kunal

    2017-01-01

    This book presents practical information on the clinical applications of short pulse laser systems and the techniques for optimizing these applications in a manner that will be relevant to a broad audience, including engineering and medical students as well as researchers, clinicians, and technicians. Short pulse laser systems are useful for both subsurface tissue imaging and laser induced thermal therapy (LITT), which hold great promise in cancer diagnostics and treatment. Such laser systems may be used alone or in combination with optically active nanoparticles specifically administered to the tissues of interest for enhanced contrast in imaging and precise heating during LITT. Mathematical and computational models of short pulse laser-tissue interactions that consider the transient radiative transport equation coupled with a bio-heat equation considering the initial transients of laser heating were developed to analyze the laser-tissue interaction during imaging and therapy. Experiments were first performe...

  15. Ultra-Wideband, Short Pulse Electromagnetics 9

    CERN Document Server

    Rachidi, Farhad; Kaelin, Armin; Sabath, Frank; UWB SP 9

    2010-01-01

    Ultra-wideband (UWB), short-pulse (SP) electromagnetics are now being used for an increasingly wide variety of applications, including collision avoidance radar, concealed object detection, and communications. Notable progress in UWB and SP technologies has been achieved by investigations of their theoretical bases and improvements in solid-state manufacturing, computers, and digitizers. UWB radar systems are also being used for mine clearing, oil pipeline inspections, archeology, geology, and electronic effects testing. Ultra-wideband Short-Pulse Electromagnetics 9 presents selected papers of deep technical content and high scientific quality from the UWB-SP9 Conference, which was held from July 21-25, 2008, in Lausanne, Switzerland. The wide-ranging coverage includes contributions on electromagnetic theory, time-domain computational techniques, modeling, antennas, pulsed-power, UWB interactions, radar systems, UWB communications, and broadband systems and components. This book serves as a state-of-the-art r...

  16. Momentum signatures for Schwinger pair production in short laser pulses with a subcycle structure.

    Science.gov (United States)

    Hebenstreit, F; Alkofer, R; Dunne, G V; Gies, H

    2009-04-17

    We investigate electron-positron pair production from vacuum for short laser pulses with a subcycle structure, in the nonperturbative regime (Schwinger pair production). We use the nonequilibrium quantum kinetic approach and show that the momentum spectrum of the created electron-positron pairs is extremely sensitive to the subcycle dynamics-depending on the laser frequency omega, the pulse length tau, and the carrier phase varphi-and shows several distinctive new signatures. This observation could not only help in the design of laser pulses to optimize the experimental signature of Schwinger pair production but also ultimately lead to new probes of light pulses at extremely short time scales.

  17. Ultra-short pulse laser proton acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Zeil, Karl; Kraft, Stephan; Bussmann, Michael; Cowan, Thomas; Kluge, Thomas; Metzkes, Josefine; Richter, Tom; Schramm, Ulrich [Forschungszentrum Dresden-Rossendorf, Dresden (Germany)

    2010-07-01

    We present a systematic investigation of ultra-short pulse laser acceleration of protons yielding unprecedented maximum proton energies of 17 MeV using the Ti:Sapphire lased high power laser of 100 TW Draco at the Research Centre Dresden-Rossendorf. For plain few micron thick foil targets a linear scaling of the maximum proton energy with laser power is observed and attributed to the short acceleration period close to the target rear surface. Although excellent laser pulse contrast was available slight deformations of the target rear were found to lead to a predictable shift of the direction of the energetic proton emission away from target normal towards the laser direction. The change of the emission characteristics are compared to analytical modelling and 2D PIC simulations.

  18. High-voltage, short-risetime pulse generator based on a ferrite pulse sharpener

    Energy Technology Data Exchange (ETDEWEB)

    Seddon, N.; Thornton, E.

    1988-11-01

    A high-voltage, short-risetime pulse generator is described. The generator consists of a Marx bank, which produces an initial high-voltage pulse, and a ferrite pulse sharpener that reduces the risetime of the pulse. The generator delivers 70-kV, 350-ps risetime pulses into a 50-..cap omega.. load.

  19. Extending ultra-short pulse laser texturing over large area

    Energy Technology Data Exchange (ETDEWEB)

    Mincuzzi, G., E-mail: girolamo.mincuzzi@alphanov.com; Gemini, L.; Faucon, M.; Kling, R.

    2016-11-15

    Highlights: • We carried out metal surface texturing (Ripples, micro grooves, Spikes) using a high power, high repetition rate, industrial, Ultra-short pulses laser. • Extremely Fast processing is shown (Laser Scan speed as high as 90 m/s) with a polygon scanner head. • Stainless steel surface blackening with Ultra-short pulses laser has been obtained with unprecedented scanspeed. • Full SEM surface characterization was carried out for all the different structures obtained. • Reflectance measurements were carried out to characterize surface reflectance. - Abstract: Surface texturing by Ultra-Short Pulses Laser (UPL) for industrial applications passes through the use of both fast beam scanning systems and high repetition rate, high average power P, UPL. Nevertheless unwanted thermal effects are expected when P exceeds some tens of W. An interesting strategy for a reliable heat management would consists in texturing with a low fluence values (slightly higher than the ablation threshold) and utilising a Polygon Scanner Heads delivering laser pulses with unrepeated speed. Here we show for the first time that with relatively low fluence it is possible over stainless steel, to obtain surface texturing by utilising a 2 MHz femtosecond laser jointly with a polygonal scanner head in a relatively low fluence regime (0.11 J cm{sup −2}). Different surface textures (Ripples, micro grooves and spikes) can be obtained varying the scan speed from 90 m s{sup −1} to 25 m s{sup −1}. In particular, spikes formation process has been shown and optimised at 25 m s{sup −1} and a full morphology characterization by SEM has been carried out. Reflectance measurements with integrating sphere are presented to compare reference surface with high scan rate textures. In the best case we show a black surface with reflectance value < 5%.

  20. Chirped pulse amplification in an extreme-ultraviolet free-electron laser

    Science.gov (United States)

    Gauthier, David; Allaria, Enrico; Coreno, Marcello; Cudin, Ivan; Dacasa, Hugo; Danailov, Miltcho Boyanov; Demidovich, Alexander; di Mitri, Simone; Diviacco, Bruno; Ferrari, Eugenio; Finetti, Paola; Frassetto, Fabio; Garzella, David; Künzel, Swen; Leroux, Vincent; Mahieu, Benoît; Mahne, Nicola; Meyer, Michael; Mazza, Tommaso; Miotti, Paolo; Penco, Giuseppe; Raimondi, Lorenzo; Ribič, Primož Rebernik; Richter, Robert; Roussel, Eléonore; Schulz, Sebastian; Sturari, Luca; Svetina, Cristian; Trovò, Mauro; Walker, Paul Andreas; Zangrando, Marco; Callegari, Carlo; Fajardo, Marta; Poletto, Luca; Zeitoun, Philippe; Giannessi, Luca; de Ninno, Giovanni

    2016-12-01

    Chirped pulse amplification in optical lasers is a revolutionary technique, which allows the generation of extremely powerful femtosecond pulses in the infrared and visible spectral ranges. Such pulses are nowadays an indispensable tool for a myriad of applications, both in fundamental and applied research. In recent years, a strong need emerged for light sources producing ultra-short and intense laser-like X-ray pulses, to be used for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences. This demand was satisfied by the advent of short-wavelength free-electron lasers. However, for any given free-electron laser setup, a limit presently exists in the generation of ultra-short pulses carrying substantial energy. Here we present the experimental implementation of chirped pulse amplification on a seeded free-electron laser in the extreme-ultraviolet, paving the way to the generation of fully coherent sub-femtosecond gigawatt pulses in the water window (2.3-4.4 nm).

  1. Chirped pulse amplification in an extreme-ultraviolet free-electron laser.

    Science.gov (United States)

    Gauthier, David; Allaria, Enrico; Coreno, Marcello; Cudin, Ivan; Dacasa, Hugo; Danailov, Miltcho Boyanov; Demidovich, Alexander; Di Mitri, Simone; Diviacco, Bruno; Ferrari, Eugenio; Finetti, Paola; Frassetto, Fabio; Garzella, David; Künzel, Swen; Leroux, Vincent; Mahieu, Benoît; Mahne, Nicola; Meyer, Michael; Mazza, Tommaso; Miotti, Paolo; Penco, Giuseppe; Raimondi, Lorenzo; Ribič, Primož Rebernik; Richter, Robert; Roussel, Eléonore; Schulz, Sebastian; Sturari, Luca; Svetina, Cristian; Trovò, Mauro; Walker, Paul Andreas; Zangrando, Marco; Callegari, Carlo; Fajardo, Marta; Poletto, Luca; Zeitoun, Philippe; Giannessi, Luca; De Ninno, Giovanni

    2016-12-01

    Chirped pulse amplification in optical lasers is a revolutionary technique, which allows the generation of extremely powerful femtosecond pulses in the infrared and visible spectral ranges. Such pulses are nowadays an indispensable tool for a myriad of applications, both in fundamental and applied research. In recent years, a strong need emerged for light sources producing ultra-short and intense laser-like X-ray pulses, to be used for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences. This demand was satisfied by the advent of short-wavelength free-electron lasers. However, for any given free-electron laser setup, a limit presently exists in the generation of ultra-short pulses carrying substantial energy. Here we present the experimental implementation of chirped pulse amplification on a seeded free-electron laser in the extreme-ultraviolet, paving the way to the generation of fully coherent sub-femtosecond gigawatt pulses in the water window (2.3-4.4 nm).

  2. Strong-field short-pulse nondipole dynamics

    DEFF Research Database (Denmark)

    Dimitrovski, Darko; Førre, Morten; Madsen, Lars Bojer

    2009-01-01

    We present a quantitative investigation of strong-field short-pulse nondipole dynamics in laser-matter interactions. We find excellent agreement between ab initio numerical and analytic results obtained using the Magnus expansion. We show that in the short-pulse limit, ultrafast transfer and cont......We present a quantitative investigation of strong-field short-pulse nondipole dynamics in laser-matter interactions. We find excellent agreement between ab initio numerical and analytic results obtained using the Magnus expansion. We show that in the short-pulse limit, ultrafast transfer...

  3. Vectorial diffraction of extreme ultraviolet light and ultrashort light pulses

    NARCIS (Netherlands)

    Nugrowati, A.M.

    2008-01-01

    In this thesis, we present applications in optics involving the diffraction theory of light for two advanced technologies. We have used a rigorous vectorial diffraction method to model: (i) the imaging of mask structures in extreme ultraviolet lithography, and (ii) ultrashort pulse propagation thro

  4. A Mutual Pulse Injection-Seeding Scheme for Optical Short Pulse Generation

    Institute of Scientific and Technical Information of China (English)

    D.; N.; Wang

    2003-01-01

    A mutual pulse injection-seeding scheme is developed to produce wavelength tunable optical short pulse generation. The sidemode suppression ratio obtained is more than 31 dB over the wavelength-tuning rang of 18 nm.

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

    Energy Technology Data Exchange (ETDEWEB)

    Phinney, L.M.; Goldman, C.H.; Longtin, J.P.; Tien, C.L. [Univ. of California, Berkeley, CA (United States)

    1995-12-31

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

  6. SLIM, Short-pulse Technology for High Gradient Induction Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Arntz, Floyd; /Diversified Tech., Bedford; Kardo-Sysoev, A.; /Ioffe Phys. Tech. Inst.; Krasnykh, A.; /SLAC

    2008-12-16

    A novel short-pulse concept (SLIM) suited to a new generation of a high gradient induction particle accelerators is described herein. It applies advanced solid state semiconductor technology and modern microfabrication techniques to a coreless induction method of charged particle acceleration first proven on a macro scale in the 1960's. Because this approach avoids use of magnetic materials there is the prospect of such an accelerator working efficiently with accelerating pulses in the nanosecond range and, potentially, at megahertz pulse rates. The principal accelerator section is envisioned as a stack of coreless induction cells, the only active element within each being a single, extremely fast (subnanosecond) solid state opening switch: a Drift Step Recovery Diode (DSRD). Each coreless induction cell incorporates an electromagnetic pulse compressor in which inductive energy developed within a transmission-line feed structure over a period of tens of nanoseconds is diverted to the acceleration of the passing charge packet for a few nanoseconds by the abrupt opening of the DSRD switch. The duration of this accelerating output pulse--typically two-to-four nanoseconds--is precisely determined by a microfabricated pulse forming line connected to the cell. Because the accelerating pulse is only nanoseconds in duration, longitudinal accelerating gradients approaching 100 MeV per meter are believed to be achievable without inciting breakdown. Further benefits of this approach are that, (1) only a low voltage power supply is required to produce the high accelerating gradient, and, (2) since the DSRD switch is normally closed, voltage stress is limited to a few nanoseconds per period, hence the susceptibility to hostile environment conditions such as ionizing radiation, mismatch (e.g. in medical applications the peak beam current may be low), strong electromagnetic noise levels, etc is expected to be minimal. Finally, we observe the SLIM concept is not limited to

  7. Generalized Short Pulse Equation for Propagation of Few-Cycle Pulses in Metamaterials

    CERN Document Server

    Pietrzyk, Monika E

    2016-01-01

    We show that propagation of ultrashort (few-cycle) pulses in nonlinear Drude metamaterials with both electric and magnetic Kerr nonlinearities is described by coupled generalized Short Pulse Equations. The resulting system of equations generalizes to the case of metamaterials both the Short Pulse Equation and its vector generalizations which describe the few-cycle pulses in dielectric optical fibers beyond the slowly varying envelope approximation leading to the nonlinear Schroedinger equation.

  8. Pulse-shaping strategies in short-pulse fiber amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Schimpf, Damian Nikolaus

    2010-02-09

    Ultrashort pulse lasers are an important tool in scientific and industrial applications. However, many applications are demanding higher average powers from these ultrashort pulse sources. This can be achieved by combining direct diode pumping with novel gain media designs. In particular, ultrashort pulse fiber lasers are now delivering average powers in the kW range. However, the design of fiber lasers, producing pulses with high peak-powers, is challenging due to the impact of nonlinear effects. To significantly reduce these detrimental effects in ultrashort pulse fiber amplifers, the combination of chirped pulse amplification (CPA) and large mode area fibers is employed. Using these methods, the pulse energy of fiber lasers has been steadily increasing for the past few years. Recently, a fiber-based CPA-system has been demonstrated which produces pulse energies of around 1 mJ. However, both the stretching and the enlargement of the mode area are limited, and therefore, the impact of nonlinearity is still noticed in systems employing such devices. The aim of this thesis is the analysis of CPA-systems operated beyond the conventional nonlinear limit, which corresponds to accumulated nonlinear phase-shifts around 1 rad. This includes a detailed discussion of the influence of the nonlinear effect self-phase modulation on the output pulse of CPA-systems. An analytical model is presented. Emphasis is placed on the design of novel concepts to control the impact of self-phase modulation. Pulse-shaping is regarded as a powerful tool to accomplish this goal. Novel methods to control the impact of SPM are experimentally demonstrated. The design of these concepts is based on the theoretical findings. Both amplitude- and phase-shaping are studied. Model-based phase-shaping is implemented in a state-of-the-art fiber CPA-system. The influence of the polarization state is also highlighted. Additionally, existing techniques and recent advances are put into context. (orig.)

  9. Short-pulse high intensity laser thin foil interaction

    Science.gov (United States)

    Audebert, Patrick

    2003-10-01

    The technology of ultrashort pulse laser generation has progressed to the point that optical pulses larger than 10 J, 300 fs duration or shorter are routinely produced. Such pulses can be focused to intensities exceeding 10^18 W/cm^2. With high contrast pulses, these focused intensities can be used to heat solid matter to high temperatures with minimal hydrodynamic expansion, producing an extremely high energy-density state of matter for a short period of time. This high density, high temperature plasma can be studied by x-ray spectroscopy. We have performed experiments on thin foils of different elements under well controlled conditions at the 100 Terawatt laser at LULI to study the characteristics X-ray emission of laser heated solids. To suppress the ASE effect, the laser was frequency doubled. S-polarized light with a peak intensity of 10^19W/cm^2 was used to minimize resonance absorption. To decrease the effect of longitudinal temperature gradients very thin (800 μ) aluminum foil targets were used. We have also studied the effect of radial gradient by limiting the measured x-ray emission zone using 50μ or 100μ pinhole on target. The spectra, in the range 7-8Å, were recorded using a conical crystal spectrometer coupled to a 800 fs resolution streak camera. A Fourier Domain Interferometry (FDI) of the back of the foil was also performed providing a measurement of the hydrodynamic expansion as function of time for each shot. To simulate the experiment, we used the 1D hydrodynamic code FILM with a given set of plasma parameter (ρ, Te) as initial conditions. The X-ray emission was calculated by post processing hydrodynamic results with a collisional-radiative model which uses super-configuration average atomic data. The simulation reproduces the main features of the experimental time resolved spectrum.

  10. Birefringence effects of short probe pulses of electromagnetically induced transparency

    Science.gov (United States)

    Parshkov, Oleg M.; Kochetkova, Anastasia E.; Budyak, Victoria V.

    2016-04-01

    The numerical simulation results of radiations evolution in the presence of electromagnetically induced transparency for J=0-->J=1-->J=2 scheme of degenerate quantum transitions are presented. The pulse regime of wave interaction with Doppler broadening spectral lines was investigated. It was indicated that when the control field is linear polarized, the input circular polarized probe pulse breaks up in the medium into pulses with mutually perpendicular linear polarizations. Polarization direction of one of these pulses coincides with the polarization direction of control fields. The distance, which probe pulse passes in the medium to its full separation, decreases, when input probe pulse duration or control field intensity decreases. The input probe pulse intensity variation almost does not influence separation distance and speed of the linear polarized probe pulses in the medium. The effects, described above, may be interpreted as the birefringence effects of electromagnetically induced transparency in the case of short probe pulse.

  11. Ultra-Short Pulse Tracking by Using Wavelength Dispersion for a Short-Time Optical Buffer

    Institute of Scientific and Technical Information of China (English)

    Tsuyoshi; Konishi; Hideaki; Furukawa; Kousuke; Asano; Kazuyoshi; Itoh

    2003-01-01

    To synchronize a control signal with a packet signal in response to changing timing jitter, we investigate ultra-short pulse tracking by using wavelength dispersion for a short-time optical buffer in an optical router.

  12. Extreme Value Statistical Characterization of Time Domain Pulse-to-Pulse Measurements

    CERN Document Server

    AUTHOR|(SzGeCERN)712364; Arpaia, Pasquale; Martino, Michele

    2015-01-01

    An analytical method, based on Extreme Value Theory (EV T), for predicting the worst case repeatability of time domain pulse-to-pulse measurements, modeled as independent and identically distributed random variables, is proposed. The method allows the use of the noise level of a measurement system for predicting the upcoming peak values over a given number of independent observations. The proposed analytical model is compared against simulated distributions generated in Matlab, highlighting satisfying match for any sample size.The simulations are based on a case study on the characterization of a pulsed power supply for the klystron modulators of the Compact LInear Collider (CLIC) under study at CERN.

  13. Phase Noise Comparision of Short Pulse Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-12-01

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

  14. Weibel instability in the field of a short laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Grishkov, V. E.; Uryupin, S. A. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2013-03-15

    The growth rate of Weibel instability in a plasma interacting with a high-frequency pulse with a duration less or comparable with the electron mean free time is determined. The growth rate is shown to decrease with decreasing pulse duration. It is found that instability can develop after the short pulse is switched off and the generated magnetic field no longer affects electron motion in the high-frequency field.

  15. Electron photodetachment by short laser pulse

    NARCIS (Netherlands)

    Golovinski, P. A.; Drobyshev, A. A.

    2012-01-01

    Expressions are derived for calculations of the total probabilities and electron spectra for the photodetachment of electrons from negative ions with filled valence s shells by ultrashort laser pulses. Particular calculations have been performed for two negative ions (H- and Li-) and titanium-sapphi

  16. Electron photodetachment by short laser pulse

    NARCIS (Netherlands)

    Golovinski, P. A.; Drobyshev, A. A.

    2012-01-01

    Expressions are derived for calculations of the total probabilities and electron spectra for the photodetachment of electrons from negative ions with filled valence s shells by ultrashort laser pulses. Particular calculations have been performed for two negative ions (H- and Li-) and titanium-sapphi

  17. Coherent excitation with short electron pulses

    Science.gov (United States)

    Guertler, Andreas; Robicheaux, Francis; Noordam, Bart

    2000-06-01

    [1pt] The probability for a transition within an atom to be driven by a collision with a long pulse of electrons is proportional to the electron flux with the proportionality factor being the cross section for this transition. Recently it was shown [1] that for electron pulses shorter than the orbit time of the electron in the atom, a contribution of coherent scattering plays a role, which is proportional to the differential cross section in forward direction and the square of the electron flux. To investigate this effect, we are developing a picosecond electron gun [2]. Collision experiments will be done with Rydberg states in lithium around n=40 with Kepler orbit times in the order of 10 ps. For picosecond electron pulses, a quadratic dependance of the transition probability on the electron flux is expected in contrast to the linear dependance expected for nanosecond electron pulses. [1pt] References [1pt] [1] F. Robicheaux and L. D. Noordam, submitted to Phys. Rev. Lett. [1pt] [2] F. Robicheaux, G. M. Lankhuijzen, and L. D. Noordam, JOSA B 15, 1 (1998)

  18. Cavity Optical Pulse Extraction: ultra-short pulse generation as seeded Hawking radiation.

    Science.gov (United States)

    Eilenberger, Falk; Kabakova, Irina V; de Sterke, C Martijn; Eggleton, Benjamin J; Pertsch, Thomas

    2013-01-01

    We show that light trapped in an optical cavity can be extracted from that cavity in an ultrashort burst by means of a trigger pulse. We find a simple analytic description of this process and show that while the extracted pulse inherits its pulse length from that of the trigger pulse, its wavelength can be completely different. Cavity Optical Pulse Extraction is thus well suited for the development of ultrashort laser sources in new wavelength ranges. We discuss similarities between this process and the generation of Hawking radiation at the optical analogue of an event horizon with extremely high Hawking temperature. Our analytic predictions are confirmed by thorough numerical simulations.

  19. Application of short-data methods on extreme surge levels

    Science.gov (United States)

    Feng, X.

    2014-12-01

    Tropical cyclone-induced storm surges are among the most destructive natural hazards that impact the United States. Unfortunately for academic research, the available time series for extreme surge analysis are very short. The limited data introduces uncertainty and affects the accuracy of statistical analyses of extreme surge levels. This study deals with techniques applicable to data sets less than 20 years, including simulation modelling and methods based on the parameters of the parent distribution. The verified water levels from water gauges spread along the Southwest and Southeast Florida Coast, as well as the Florida Keys, are used in this study. Methods to calculate extreme storm surges are described and reviewed, including 'classical' methods based on the generalized extreme value (GEV) distribution and the generalized Pareto distribution (GPD), and approaches designed specifically to deal with short data sets. Incorporating global-warming influence, the statistical analysis reveals enhanced extreme surge magnitudes and frequencies during warm years, while reduced levels of extreme surge activity are observed in the same study domain during cold years. Furthermore, a non-stationary GEV distribution is applied to predict the extreme surge levels with warming sea surface temperatures. The non-stationary GEV distribution indicates that with 1 Celsius degree warming in sea surface temperature from the baseline climate, the 100-year return surge level in Southwest and Southeast Florida will increase by up to 40 centimeters. The considered statistical approaches for extreme surge estimation based on short data sets will be valuable to coastal stakeholders, including urban planners, emergency managers, and the hurricane and storm surge forecasting and warning system.

  20. Pair production in short laser pulses near threshold

    Energy Technology Data Exchange (ETDEWEB)

    Nousch, T. [Helmholtz-Zentrum Dresden-Rossendorf, POB 510119, 01314 Dresden (Germany); TU Dresden, Institut fuer Theoretische Physik, 01062 Dresden (Germany); Seipt, D., E-mail: d.seipt@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, POB 510119, 01314 Dresden (Germany); TU Dresden, Institut fuer Theoretische Physik, 01062 Dresden (Germany); Kaempfer, B. [Helmholtz-Zentrum Dresden-Rossendorf, POB 510119, 01314 Dresden (Germany); TU Dresden, Institut fuer Theoretische Physik, 01062 Dresden (Germany); Titov, A.I. [Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna 141980 (Russian Federation)

    2012-08-29

    The e{sup +}e{sup -} pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit-Wheeler process. For short laser pulses with very few oscillations of the electromagnetic field we find below the perturbative weak-field threshold {radical}(s)=2m a similar enhancement of the pair production rate as for circular polarization. The strong enhancement below the weak-field threshold is traced back to the finite bandwidth of the laser pulse. A folding model is developed which accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.

  1. Pair production in short laser pulses near threshold

    Science.gov (United States)

    Nousch, T.; Seipt, D.; Kämpfer, B.; Titov, A. I.

    2012-08-01

    The e+e- pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit-Wheeler process. For short laser pulses with very few oscillations of the electromagnetic field we find below the perturbative weak-field threshold √{ s} = 2 m a similar enhancement of the pair production rate as for circular polarization. The strong enhancement below the weak-field threshold is traced back to the finite bandwidth of the laser pulse. A folding model is developed which accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.

  2. Pair production in short intense laser pulses near threshold

    Energy Technology Data Exchange (ETDEWEB)

    Nousch, Tobias; Seipt, Daniel; Kaempfer, Burkhart [Helmholtz-Zentrum Dresden-Rossendorf, POB 510119, 01314 Dresden (Germany); TU Dresden, Institut fuer Theoretische Physik, 01062 Dresden (Germany); Titov, Alexander I. [Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna 141980 (Russian Federation)

    2013-07-01

    We study finite-size effects in the process of e{sup +}e{sup -} pair production via the non-linear Breit-Wheeler process in ultra short laser pulses. Based on the Nikishov-Ritus method we use laser dressed electron and positron wave functions to derive the differential and total pair production cross section, focusing on the effects of a finite pulse duration. For short laser pulses with very few oscillations of the electromagnetic field we find an increase of the pair production rate below the perturbative weak-field threshold. The strong enhancement below the weak-field threshold is traced back to the finite bandwidth of the laser pulse. A folding model accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.

  3. Short pulse generation and high speed communication system

    Science.gov (United States)

    Fan, Honglei

    Ultrahigh-speed optical time-division-multiplexing (TDM) transmission technologies are essential to construct ultrahigh-speed all-optical networks needed in the multimedia era. In order to realize high-speed optical TDM systems, ultra-short pulses should be generated. In this dissertation, the gain switching and mode locking techniques have been analyzed and used to produce ultra- short pulses. Gain-switched pulses with a width of ~18ps have been obtained. The theoretical analysis on gain-switching phenomena has been carried out. A new approach for the simulation of the spectrum of a gain- switched laser has been developed. The principle of mode locking has been discussed. ~6.5ps, pulses have been obtained from a monolithic mode-locked distributed Bragg reflector (DBR) laser, which are the shortest pulses from the actively mode- locked DBR lasers as we know. ~1.1ps pulses have been achieved from a colliding-pulse mode-locked (CPM) laser. The operation principle of CPM lasers has been discussed. Pulse compression using dispersion-compensating fiber has been applied in order to get shorter pulses. The semiconductor optical amplifier (SOA) plays a very important role in TDM systems. The cross gain modulation (XGM) measurements on a 2-section SOA, using both cw and pulsed pump and probe beams, have been performed. A theoretical analysis has been carried out. Wavelength conversion and fiber transmission experiments have been achieved at different bit rates. The basic idea of TDM system has been discussed. Multiplexing has been achieved using fibers. Demulitplexing has been demonstrated using XGM in SOA, four-wave mixing (FWM) in SOA, and cascaded modulators. The operation principles have been discussed in detail. The FWM experiments between two optical pulses have been performed.

  4. Generation, temporal characterization and applications of femtosecond-/ attosecond extreme ultraviolet pulses

    Science.gov (United States)

    Thomann, Isabell

    The work of this thesis is arranged into three parts: (A) Generation and temporal characterization of extreme ultraviolet (EUV) attosecond pulses. In this work I present the generation and first temporal characterization of sub-optical cycle EUV radiation generated in a noble-gas filled hollow-core waveguide. Two regimes of EUV radiation were characterized, ranging from 200 attoseconds to ˜ 1 femtosecond in duration. The first regime that was characterized distinguishes itself from EUV radiation generated by other methods by its narrow (˜ 1 eV) spectral width, its simple energy tunability and its temporal confinement to ˜ 1 femtosecond. In the second regime, single isolated pulses of 200 attoseconds duration (and accordingly larger bandwidth) were generated. In both regimes dynamic phase-matching effects create an extremely short time window within which efficient nonlinear conversion is possible, while it is suppressed outside this window. Temporal characterization of the generated EUV pulses was approached by two-color pump-probe photoelectron spectroscopy. Therefore an efficient photoelectron spectrometer was set up, detecting electrons in a 2pi collection angle. For the interpretation of the experimental data, an analytical model as well as an iterative algorithm were developed, to allow extraction of complex EUV waveforms. The demonstrated radiation will allow for time-resolved studies of the fastest processes in molecules and condensed matter, while at the same time ensuring adequate energy resolution for addressing individual electronic states. (B) Application of a COLTRIMS reaction microscope in combination with femtosecond EUV pulses to questions in molecular physics. The combination of the sensitive detection capabilities of a COLTRIMS reaction microscope with the high time resolution of pump-probe experiments using femtosecond extreme-ultraviolet pulses makes it possible to answer very fundamental open questions in molecular physics such as the

  5. Ultra-short pulsed laser engineered metal-glass nanocomposites

    CERN Document Server

    Stalmashonak, Andrei; Abdolvand, Amin

    2013-01-01

    Glasses containing metallic nanoparticles exhibit very promising linear and nonlinear optical properties, mainly due to the surface plasmon resonances (SPRs) of the nanoparticles. The spectral position in the visible and near-infrared range and polarization dependence of the SPR are characteristically determined by the nanoparticles’ shapes. The focus of Ultra-Short Pulsed Laser Engineered Metal-Glass Nanocomposites is the interaction of intense ultra-short laser pulses with glass containing silver nanoparticles embedded in soda-lime glass, and nanostructural modifications in metal-glass nanocomposites induced by such laser pulses. In order to provide a comprehensive physical picture of the processes leading to laser-induced persistent shape transformation of the nanoparticles, series of experimental results investigating the dependences of laser assisted shape modifications of nanoparticles with laser pulse intensity, excitation wavelength, temperature are considered. In addition, the resulting local opti...

  6. Upconversion imaging using short-wave infrared picosecond pulses

    DEFF Research Database (Denmark)

    Mathez, Morgan David; Rodrigo, Peter John; Tidemand-Lichtenberg, Peter

    2017-01-01

    To the best of our knowledge, we present the first demonstration of short-wavelength infrared image upconversion that employs intense picosecond signal and pump beams. We use a fiber laser that emits a signal beam at 1877 nm and a pump beam at 1550 nm—both with a pulse width of 1 ps and a pulse...... by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination....

  7. Medical applications of ultra-short pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B M; Marion, J E

    1999-06-08

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

  8. Short pulse generation by laser slicing at NSLSII

    Energy Technology Data Exchange (ETDEWEB)

    Yu, L.; Blednykh, A.; Guo, W.; Krinsky, S.; Li, Y.; Shaftan, T.; Tchoubar, O.; Wang, G.; Willeke, F.; Yang, L.

    2011-03-28

    We discuss an upgrade R&D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. We discuss its basic parameters and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring. There is a rapid growth of ultrafast user community interested in science using sub-pico-second x-ray pulses. In BNL's Short Pulse Workshop, the discussion from users shows clearly the need for a sub-pico-second pulse source using laser slicing method. In the proposal submitted following this workshop, NSLS team proposed both hard x-ray and soft x-ray beamlines using laser slicing pulses. Hence there is clearly a need to consider the R&D efforts of laser slicing short pulse generation at NSLSII to meet these goals.

  9. Amplification of Short Pulse High Power UV Laser

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    At recent year, with the development of CPA and other amplification technology, laser intensity achieves great increase and laser power can be high to PW(105) now, this ultrashort pulse lasers offer scientists a route to investigate laser-matter interaction in an absolute new regime.So far the researches on ultrashort pulse laser-matter interaction concentrated on infrared regime, yet ultraviolet laser has the advantage in intense field physics and ICF researches for its short wavelength and less nonlinear effects. KrF excimer is the best medium in UV ultrashort pulse amplification for its small saturation energy and high contrast ratio accessible.

  10. Short-Pulsed Wavepacket Propagation in Ray-Chaotic Enclosures

    CERN Document Server

    Castaldi, Giuseppe; Pinto, Innocenzo M

    2011-01-01

    Wave propagation in ray-chaotic scenarios, characterized by exponential sensitivity to ray-launching conditions, is a topic of significant interest, with deep phenomenological implications and important applications, ranging from optical components and devices to time-reversal focusing/sensing schemes. Against a background of available results that are largely focused on the time-harmonic regime, we deal here with short-pulsed wavepacket propagation in a ray-chaotic enclosure. For this regime, we propose a rigorous analytical framework based on a short-pulsed random-plane-wave statistical representation, and check its predictions against the results from finite-difference-time-domain numerical simulations.

  11. Generation of short electrical pulses based on bipolar transistorsny

    Directory of Open Access Journals (Sweden)

    M. Gerding

    2004-01-01

    Full Text Available A system for the generation of short electrical pulses based on the minority carrier charge storage and the step recovery effect of bipolar transistors is presented. Electrical pulses of about 90 ps up to 800 ps duration are generated with a maximum amplitude of approximately 7V at 50Ω. The bipolar transistor is driven into saturation and the base-collector and base-emitter junctions become forward biased. The resulting fast switch-off edge of the transistor’s output signal is the basis for the pulse generation. The fast switching of the transistor occurs as a result of the minority carriers that have been injected and stored across the base-collector junction under forward bias conditions. If the saturated transistor is suddenly reverse biased the pn-junction will appear as a low impedance until the stored charge is depleted. Then the impedance will suddenly increase to its normal high value and the flow of current through the junction will turn to zero, abruptly. A differentiation of the output signal of the transistor results in two short pulses with opposite polarities. The differentiating circuit is implemented by a transmission line network, which mainly acts as a high pass filter. Both the transistor technology (pnp or npn and the phase of the transfer function of the differentating circuit influence the polarity of the output pulses. The pulse duration depends on the transistor parameters as well as on the transfer function of the pulse shaping network. This way of generating short electrical pulses is a new alternative for conventional comb generators based on steprecovery diodes (SRD. Due to the three-terminal structure of the transistor the isolation problem between the input and the output signal of the transistor network is drastically simplified. Furthermore the transistor is an active element in contrast to a SRD, so that its current gain can be used to minimize the power of the driving signal.

  12. Experimental investigation of electron beam wave interactions utilising short pulses

    CERN Document Server

    Wiggins, S M

    2000-01-01

    Experiments have investigated the production of ultra-short electromagnetic pulses and their interaction with electrons in various resonant structures. Diagnostic systems used in the measurements included large bandwidth detection systems for capturing the short pulses. Deconvolution techniques have been applied to account for bandwidth limitation of the detection systems and to extract the actual pulse amplitudes and durations from the data. A Martin-Puplett interferometer has been constructed for use as a Fourier transform spectrometer. The growth of superradiant electromagnetic spikes from short duration (0.5-1.0 ns), high current (0.6-2.0 kA) electron pulses has been investigated in a Ka-band Cherenkov maser and Ka- and W-band backward wave oscillators (BWO). In the Cherenkov maser, radiation spikes were produced with a peak power = 70 ps and a bandwidth <= 19 %. It is shown that coherent spontaneous emission from the leading edge of the electron pulse drives these interactions, giving rise to self-amp...

  13. CIDME: Short distances measured with long chirp pulses

    Science.gov (United States)

    Doll, Andrin; Qi, Mian; Godt, Adelheid; Jeschke, Gunnar

    2016-12-01

    Frequency-swept pulses have recently been introduced as pump pulses into double electron-electron resonance (DEER) experiments. A limitation of this approach is that the pump pulses need to be short in comparison to dipolar evolution periods. The "chirp-induced dipolar modulation enhancement" (CIDME) pulse sequence introduced in this work circumvents this limitation by means of longitudinal storage during the application of one single or two consecutive pump pulses. The resulting six-pulse sequence is closely related to the five-pulse "relaxation-induced dipolar modulation enhancement" (RIDME) pulse sequence: While dipolar modulation in RIDME is due to stochastic spin flips during longitudinal storage, modulation in CIDME is due to the pump pulse during longitudinal storage. Experimentally, CIDME is examined for Gd-Gd and nitroxide-nitroxide distance determination using a high-power Q-band spectrometer. Since longitudinal storage results in a 50% signal loss, comparisons between DEER using short chirp pump pulses of 64 ns duration and CIDME using longer pump pulses are in favor of DEER. While the lower sensitivity restrains the applicability of CIDME for routine distance determination on high-power spectrometers, this result is not to be generalized to spectrometers having lower power and to specialized "non-routine" applications or different types of spin labels. In particular, the advantage of prolonged CIDME pump pulses is demonstrated for experiments at large frequency offset between the pumped and observed spins. At a frequency separation of 1 GHz, where broadening due to dipolar pseudo-secular contributions becomes largely suppressed, a Gd-Gd modulation depth larger than 10% is achieved. Moreover, a CIDME experiment at deliberately reduced power underlines the potential of the new technique for spectrometers with lower power, as often encountered at higher microwave frequencies. With longitudinal storage times T below 10 μs, however, CIDME appears rather

  14. Theory and simulation of ultra-short pulse laser interactions

    Energy Technology Data Exchange (ETDEWEB)

    More, R.; Walling, R.; Price, D.; Guethlein, G.; Stewart, R.; Libby, S.; Graziani, F.; Levatin, J. [Lawrence Livermore National Lab., Livermore, CA (United States)

    1998-03-01

    This paper describes recent Livermore work aimed at building computational tools to describe ultra-short pulse laser plasmas. We discuss calculations of laser absorption, atomic data for high-charge ions, and a new idea for linear-response treatment of non-equilibrium phenomena near LTE. (author)

  15. Observation of superradiance in a short-pulse FEL oscillator

    NARCIS (Netherlands)

    Jaroszynski, D. A.; Chaix, P.; Piovella, N.; Oepts, D.; Knippels, G.M.H.; van der Meer, A. F. G.; Weits, H. H.

    1997-01-01

    Superradiance has been experimentally studied, in a short-pulse free-electron laser (FEL) oscillator. Superradiance is the optimal way of extracting optical radiation from an FEL and can be characterised by the following scale laws: peak optical power P, scales as the square of electron charge, Q, (

  16. Laser short pulse heating of metal nano-wires

    Science.gov (United States)

    Yilbas, B. S.; Al-Dweik, A. Y.

    2012-11-01

    Non-equilibrium energy transfer takes place in a solid substrate during a short-pulse laser irradiation and temperature field can be obtained analytically in the irradiated region. In the present study, laser short-pulse heating of metal nano-wire is considered and the analytical solution for two-dimensional axisymmetric nano-wire is presented. Since the absorption of the incident beam takes place in the skin of the irradiated surface, a volumetric heat source resembling the absorption process is incorporated in the analysis. Three different nano-wire materials are introduced in the analysis for the comparison reason. These include silver, chromium, and copper. It is found that temperature decay is gradual on the surface vicinity and temporal variation of the surface temperature follows almost the laser pulse intensity profile at the irradiated center.

  17. Two-electron quantum ring in short pulses

    Institute of Scientific and Technical Information of China (English)

    Poonam Silotia; Rakesh Kumar Meena; Vinod Prasad

    2015-01-01

    The response of two-electron quantum ring system to the short laser pulses of different shapes in the presence of external static electric field is studied. The variation of transition probabilities of the two-electron quatum ring from ground state to excited states with a number of parameters is shown and explained. The energy levels and wavefunctions of the system in the presence of static electric field are found by solving the time-independent Schr ¨odinger equation numerically by finite difference method. The shape of the pulse plays a dominant role on the dynamics.

  18. Quantum quenching of radiation losses in short laser pulses

    CERN Document Server

    Harvey, Chris; Ilderton, Anton; Marklund, Mattias

    2016-01-01

    Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.

  19. Short pulse mid-infrared amplifier for high average power

    CSIR Research Space (South Africa)

    Botha, LR

    2006-09-01

    Full Text Available @csir.co.za Telephone number of main author: +27-12-841-3447 Fax number of main author: +27-12-841-3152 Complete mailing address of main author: L R Botha, P O Box 395, Building 46, 2 nd Floor, Pretoria, 0001, South Africa Topic Area: Gas lasers including metal....1  Hz. If the relationship 4.0 vt is used then pulses as short as 0.5 ps can be amplified. The gain bandwidth can be increased by using isotopic mixtures and consequently this will allow pulses shorter than 0.5ps to be amplified. Gas lasers...

  20. Transitions between refrigeration regions in extremely short quantum cycles

    Science.gov (United States)

    Feldmann, Tova; Kosloff, Ronnie

    2016-05-01

    The relation between the geometry of refrigeration cycles and their performance is explored. The model studied is based on a coupled spin system. Small cycle times, termed sudden refrigerators, develop coherence and inner friction. We explore the interplay between coherence and energy of the working medium employing a family of sudden cycles with decreasing cycle times. At the point of maximum coherence the cycle changes geometry. This region of cycle times is characterized by a dissipative resonance where heat is dissipated both to the hot and cold baths. We rationalize the change of geometry of the cycle as a result of a half-integer quantization which maximizes coherence. From this point on, increasing or decreasing the cycle time, eventually leads to refrigeration cycles. The transition point between refrigerators and short circuit cycles is characterized by a transition from finite to singular dynamical temperature. Extremely short cycle times reach a universal limit where all cycles types are equivalent.

  1. Short-pulse propagation in fiber optical parametric amplifiers

    DEFF Research Database (Denmark)

    Cristofori, Valentina

    and can operate with a potentially low noise figure with respect to erbium-doped fiber amplifiers and Raman amplifiers, when working in phase-sensitive configurations. A characterization of the signal distortion mechanisms introduced by FOPAs is relevant for investigating the applicability of FOPAs......Fiber optical parametric amplifiers (FOPAs) are attractive because they can provide large gain over a broad range of central wavelengths, depending only on the availability of a suitable pump laser. In addition, FOPAs are suitable for the realization of all-optical signal processing functionalities...... transfer can be reduced in saturated F OPAs. In order to characterize propagation impairments such as dispersion and Kerr effect, affecting signals reaching multi-terabit per second per channel, short pulses on the order of 500 fs need to be considered. Therefore, a short pulses fiber laser source...

  2. Coherent combs in ionization by intense and short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Krajewska, K., E-mail: Katarzyna.Krajewska@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland); Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0299 (United States); Kamiński, J.Z., E-mail: Jerzy.Kaminski@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)

    2016-03-22

    Photoionization of positive ions by a train of intense, short laser pulses is investigated within the relativistic strong field approximation, using the velocity gauge. The formation of broad peak structures in the high-energy domain of photoelectrons is observed and interpreted. The emergence of coherent photoelectron energy combs within these structures is demonstrated, and it is interpreted as the consequence of the Fraunhofer-type interference/diffraction of probability amplitudes of ionization from individual pulses comprising the train. Extensions to the coherent angular combs are also studied, and effects related to the radiation pressure are presented. - Highlights: • We develop relativistic Strong-Field Approximation for ionization by intense and short laser pulses of arbitrary spectral compositions. • We show that the consistent interpretation of results is provided by the Keldysh-type saddle point analysis of probability amplitudes. • We derive a general Fraunhofer-type interference/diffraction formula for finite train of pulses. • We study the coherent combs in photoelectron probability distributions.

  3. Delaying Trains of Short Light Pulses in WGM Resonators

    Science.gov (United States)

    Matsko, Andrey; Iltchenko, Vladimir; Strekalov, Dmitry; Savchenkov, Anatoliy; Maleki, Lute

    2008-01-01

    Suitably configured whispering-gallery-mode (WGM) optical resonators have been proposed as delay lines for trains of short light pulses. Until now, it has been common practice to implement an optical delay line as a coiled long optical fiber, which is bulky and tends to be noisy. An alternative has been to implement an optical delay line as a coupled-resonator optical waveguide (a chain of coupled optical resonators), which is compact but limits the width of the pulse spectrum to the width of an optical resonance and thereby places a lower limit on the duration of a pulse. In contrast, a delay line according to the proposal could be implemented as a single WGM resonator, and the pulses delayed by the resonator could be so short that their spectral widths could greatly exceed the spectral width of any single resonance. The proposal emerged from theoretical and experimental studies of the propagation of a pulse train in a WGM resonator. An important element of the theoretical study was recognition that the traditional definition of group velocity in effect, the velocity of a single pulse comprising a packet of waves propagating in a medium, the responsivity of which is a monotonous function of frequency does not necessarily apply in the case of a WGM resonator or other medium having a spectrum consisting of discrete resonance peaks at different frequencies. A new definition of group velocity, applicable to a train of pulses propagating in such a medium, was introduced and found to lead to the discovery of previously unknown features of propagation. Notably, it was found that in a micro - sphere optical resonator that supports a suitable combination of WGM modes, the group velocity for a train of light pulses could be positive, zero, or negative. A positive group velocity could be so small that the delay could be much longer than the ring-down time of the resonator; a delay of such great length is impossible for a single pulse interacting with either a linearly

  4. Kr photoionized plasma induced by intense extreme ultraviolet pulses

    Science.gov (United States)

    Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Skrzeczanowski, W.

    2016-04-01

    Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Kr plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.

  5. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-08-27

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

  6. Optimization of Short-Pulse GPR Transmit Antenna

    Institute of Scientific and Technical Information of China (English)

    LI Tai-quan; TIAN Mao; XU Ji-sheng

    2004-01-01

    By analyzing the current distribution of Bow-Tie antenna used in short-pulse ground penetrating radar, the methods of antenna load and driving are presented in this paper to reduce strength of reflective wave both at antenna end and excitation point. The numerical simulation results show the strength of reflective wave is smaller than -55 dB comparing with the driving wave when the methods are adopted.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-08-24

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

  8. Experimental uses of short pulse radar in coal seams

    Energy Technology Data Exchange (ETDEWEB)

    Coon, J.B.; Fowler, J.C.; Schafers, C.J.

    1980-04-01

    Radar tests in coal mines conducted by the Mining Research Division of Conoco and Ensco, Inc. are presented. The purpose was to determine penetration distances and reflection ranges which are obtainable with currently available short pulse radar. The tests were conducted in mines operated by Consolidation Coal Co. during 1977 and 1978. The first test examined penetration distances, velocity of propagation, and attenuation versus frequency for a large coal pillar. These tests also showed the definite polarization effects which had previously been measured in coal. The second series of tests was designed to show maximum reflection distances for a radar with a centre frequency of 100 MHz. Using common-depth-point reflection techniques, a ten-fold CDP line obtained reflections from distances in excess of 50 ft. This was the first time such techniques have been used with short pulse radar. The final series of tests was conducted to locate a six-inch borehole within a coal pillar. The radar system located the hole quickly and easily even though it was 20 ft into the pillar. These tests show it is possible to use short pulse radar as a hazard detection device in coal mines. The major limitations with a current equipment are that it cannot be used in return air and it is not easily transported in the mine. As a result of these tests, Conoco and Ensco have started a development program to build and test a truly portable mine radar system capable of operation in return air.

  9. Variable Power, Short Microwave Pulses Generation using a CW Magnetron

    Directory of Open Access Journals (Sweden)

    CIUPA, R.

    2011-05-01

    Full Text Available Fine control of microwave power radiation in medical and scientific applications is a challenging task. Since a commercial Continuous Wave (CW magnetron is the most inexpensive microwave device available today on the market, it becomes the best candidate for a microwave power generator used in medical diathermy and hyperthermia treatments or high efficiency chemical reactions using microwave reactors as well. This article presents a new method for driving a CW magnetron with short pulses, using a modified commercial Zero Voltage Switching (ZVS inverter, software driven by a custom embedded system. The microwave power generator designed with this method can be programmed for output microwave pulses down to 1% of the magnetron's power and allows microwave low frequency pulse modulation in the range of human brain electrical activity, intended for medical applications. Microwave output power continuous control is also possible with the magnetron running in the oscillating area, using a dual frequency Pulse Width Modulation (PWM, where the low frequency PWM pulse is modulating a higher resonant frequency required by the ZVS inverter's transformer. The method presented allows a continuous control of both power and energy (duty-cycle at the inverter's output.

  10. Electron detachment from negative ions in a short laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Shearer, S. F. C.; Smyth, M. C.; Gribakin, G. F. [School of Mathematics and Physics, Queen' s University Belfast, Belfast, BT7 1NN (United Kingdom)

    2011-09-15

    We present an efficient and accurate method to study electron detachment from negative ions by a few-cycle linearly polarized laser pulse. The adiabatic saddle-point method of Gribakin and Kuchiev [Phys. Rev. A 55, 3760 (1997)] is adapted to calculate the transition amplitude for a short laser pulse. Its application to a pulse with N optical cycles produces 2(N+1) saddle points in complex time, which form a characteristic 'smile.' Numerical calculations are performed for H{sup -} in a 5-cycle pulse with frequency 0.0043 a.u. and intensities of 10{sup 10}, 5x10{sup 10}, and 10{sup 11} W/cm{sup 2}, and for various carrier-envelope phases. We determine the spectrum of the photoelectrons as a function of both energy and emission angle, as well as the angle-integrated energy spectra and total detachment probabilities. Our calculations show that the dominant contribution to the transition amplitude is given by 5-6 central saddle points, which correspond to the strongest part of the pulse. We examine the dependence of the photoelectron angular distributions on the carrier-envelope phase and show that measuring such distributions can provide a way of determining this phase.

  11. Numerical simulation of extremely chirped pulse formation with an optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Tamitake; Nishimura, Akihiko; Tei, Kazuyoku; Matoba, Tohru; Takuma, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Yamashita, Mikio; Morita, Ryuji

    1998-03-01

    A nonlinear propagation code which used a symmetric split-step Fourier method as an algorithm was improved to simulate a propagation behavior of extremely chirped pulse in a long fiber. The performances of pulse propagation in noble gases cored hollow fibers and a pulse stretcher using a nonlinear and normal silicate fibers have been simulated by the code. The calculation results in the case of the hollow fiber are consistent with their experimental results. We estimated that this pulse stretcher could give a extremely chirped pulse whose spectral width was 84.2 nm and temporal duration was 1.5 ns. (author)

  12. Single-step electropolymerization patterning of a polypyrrole nanowire by ultra-short pulses via an AFM cantilever

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Kihwan; Lee, Gyudo; Jung, Huihun; Kim, Chi Hyun; Seo, Jongbum; Yoon, Dae Sung; Lee, Sang Woo; Kwon, Taeyun [Department of Biomedical Engineering, Yonsei University, Wonju, 220-710 (Korea, Republic of); Park, Jinsung, E-mail: yusuklee@yonsei.ac.kr, E-mail: tkwon@yonsei.ac.kr [Department of Mechanical Engineering, Korea University, Seoul, 136-701 (Korea, Republic of)

    2011-06-03

    Conducting polymers (CPs) have attracted a great deal of attention due to their unique properties; these properties are useful in implementing various functional devices, such as memory, and chemical and biological sensors. In particular, the nanopatterning of CPs is a key technology that will accelerate the adoption of CPs in fabricating nanoscaled multifunctional devices. This paper presents an innovative technique for forming polypyrrole nanowire (PPy-NW) patterns, without any additional pretreatment on the gold surface, using atomic force microscopy (AFM) and ultra-short pulse voltage. Applying the ultra-short pulse voltage to the AFM tip has the following advantage: since the electrochemical current is extremely localized around the tip, the successful formation of CP nanowires results. This is because the pulse width is much shorter than the resistor-capacitor (RC) time constant of the equivalent electrochemical circuit of our experimental set-up. This paper provides systematic results regarding the dimensional variation of the PPy-NW patterns produced by varying the electrical conditions of the ultra-short pulse, such as the pulse amplitude, width, and frequency. The results show that use of an ultra-short pulse is essential in fabricating PPy-NW patterns. Additionally, an ultra-short pulse offers excellent pattern controllability for both width (353 nm {approx} 3.37 {mu}m) and height (2.0 {approx} 88.3 nm).

  13. Compact short-pulse laser for near-field range-gated imaging

    Science.gov (United States)

    Zutavern, Fred J.; Helgeson, Wesley D.; Loubriel, Guillermo M.; Yates, George J.; Gallegos, Robert A.; McDonald, Thomas E., Jr.

    1997-05-01

    This paper describes a compact laser, which produces high power, wide-angle emission for a near-field, range-gated, imaging system. The optical pulses are produced by a 100 element laser diode array (LDA) which is pulsed with a GaAs, photoconductive semiconductor switch (PCSS). The LDA generates 100 ps long, gain-switched, optical pulses at 904 nm when it is driven with 3 ns, 400 A, electrical pulses from a high gain PCSS. Gain switching is facilitated with this many lasers by using a low impedance circuit to drive an array of lasers, which are connected electrically in series. The total optical energy produced per pulse is 100 microjoules corresponding to a total peak power of 100 kW. The entire laser system, including prime power (a nine volt battery), pulse charging, PCSS, and LDA, is the size of a small, hand-held flashlight, System lifetime, which is presently limited by the high gain PCSS, is an active area of research and development. Present limitations and potential improvements will be discussed. The complete range-gated imaging system is based on complementary technologies: high speed optical gating with intensified charge coupled devices (ICCD) developed at Los Alamos National Laboratory and high gain, PCSS-driven LDAs developed at Sandia National Laboratories. The system is designed for use in highly scattering media such as turbid water or extremely dense fog or smoke. The short optical pulses from the laser and high speed gating of the ICCD are synchronized to eliminate the back-scattered light from outside the depth of the field of view (FOV) which may be as short as a few centimeters. A high speed photodiode can be used to trigger the intensifier gate and set the range-gated FOV precisely on the target. The ICCD and other aspects of the imaging system are discussed in a separate paper.

  14. An integrated CMOS detection system for optical short-pulse

    Science.gov (United States)

    Kim, Chang-Gun; Hong, Nam-Pyo; Choi, Young-Wan

    2014-03-01

    We present design of a front-end readout system consisting of charge sensitive amplifier (CSA) and pulse shaper for detection of stochastic and ultra-small semiconductor scintillator signal. The semiconductor scintillator is double sided silicon detector (DSSD) or avalanche photo detector (APD) for high resolution and peak signal reliability of γ-ray or X-ray spectroscopy. Such system commonly uses low noise multichannel CSA. Each CSA in multichannel includes continuous reset system based on tens of MΩ and charge-integrating capacitor in feedback loop. The high value feedback resistor requires large area and huge power consumption for integrated circuits. In this paper, we analyze these problems and propose a CMOS short pulse detection system with a novel CSA. The novel CSA is composed of continuous reset system with combination of diode connected PMOS and 100 fF. This structure has linearity with increased input charge quantity from tens of femto-coulomb to pico-coulomb. Also, the front-end readout system includes both slow and fast shapers for detecting CSA output and preventing pile-up distortion. Shaping times of fast and slow shapers are 150 ns and 1.4 μs, respectively. Simulation results of the CMOS detection system for optical short-pulse implemented in 0.18 μm CMOS technology are presented.

  15. Superradiance of short electron pulses in regular and corrugated waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Ginzburg, N.S.; Konoplev, I.V.; Sergeev, A.S. [Institute of Applied Physics, Nizhny Novgorod (Russian Federation)] [and others

    1995-12-31

    The report is devoted to theoretical and experimental study of superradiance of short electron pulses moving through waveguide systems. It is suggested that electrons oscillate or in undulator field (undulator SR) or in homogeneous magnetic field (cyclotron SR). We studied specific regimes of SR which may occur due to peculiarities of waveguide dispersion. Among them there are regimes of radiation near cut-off frequency as well as regimes of group synchronism. At the last operating regimes an electron bunch longitudinal velocity coincide with group velocity of e.m. wave. It is found the increasing of the SR instability grows rate and energy extraction efficiency in such regimes. It is also possible to observe the same enhancement using external feedback in periodically corrugated waveguide when Bragg resonance condition with forward propagated e.m. wave is fulfill. For experimental observation of cyclotron SR we intend to use compact subnanosecond accelerator RADAN 303B on the base of the high voltage generator with special subnansecond transformer. Accelerator generates short 0.3ns electron pulses with current about 1kA and particles energy 200keV. Design of magnetic confound system provide possibility to install an active locker to impose to electrons cyclotron rotation with pitch-factor about 1-1.5. According to numerical simulation at the mm and submm wavebands it is possible to achieve radiation pick power about 5-10MW with pulse duration less than 1ns.

  16. Upconversion imaging using short-wave infrared picosecond pulses.

    Science.gov (United States)

    Mathez, Morgan; Rodrigo, Peter John; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2017-02-01

    To the best of our knowledge, we present the first demonstration of short-wavelength infrared image upconversion that employs intense picosecond signal and pump beams. We use a fiber laser that emits a signal beam at 1877 nm and a pump beam at 1550 nm-both with a pulse width of 1 ps and a pulse repetition rate of 21.7 MHz. Due to synchronization of high peak-power pulses, efficient upconversion is achieved in a single-pass setup that employs a bulk lithium niobate crystal. Optimizing the temporal overlap of the pulses for high upconversion efficiency enables us to exploit a relatively large pump beam diameter to upconvert a wider range of signal spatial frequencies in the crystal. The 1877 nm signal is converted into 849 nm-enabling an image to be acquired by a silicon CCD camera. The measured size of the smallest resolvable element of this imaging system is consistent with the value predicted by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, Chad M. (Honeywell FM& T, Kansas City, MO); Perricone, Matthew J. (R.J. Lee Group, Inc., Monroeville, PA); Faraone, Kevin M. (BWX Technologies, Inc., Lynchburg, VA); Norris, Jerome T.

    2007-10-01

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

  18. Modeling short-pulse laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Sandkamm, Ditte Både; Haahr-Lillevang, Lasse

    2014-01-01

    A theoretical description of ultrashort-pulse laser excitation of dielectric materials based on strong-field excitation in the Keldysh picture combined with a multiple-rateequation model for the electronic excitation including collisional processes is presented. The model includes light attenuation...... in a self-consistent manner and changing optical properties described in a Drude picture. The model can be used to calculate the electronic excitation as a function of time and depth, and from these quantities the time-dependent optical parameters as well as the ablation depth can be derived....... The simulations provide insight into the excitation and propagation dynamics of short-pulse excitation and show that at increasing fluence the excitation becomes localized near the material surface and gives rise to strongmodifications of the optical properties of the material....

  19. Multiple quantum wells for passive ultra short laser pulse generation

    CERN Document Server

    Quintero-Torres, R; Rodriguez-Rodriguez, E; Stintz, Andreas; Diels, Jean-Claude

    2007-01-01

    Solid state lasers are demanding independent control in the gain media and cavity loss to achieve ultra short laser pulses using passive mode-locking. Recently, laser mode-locking is achieved with a MBE structure with multiple quantum wells, designed to achieve two functions; Bragg mirror and changes in absorption to control the cavity dynamics. The use of an AlGaAs/AlAs Bragg mirror with a 15 nm GaAs saturable absorber used in a Cr:LiSAF tuneable laser proved to be effective to produce femtosecond pulses. The use of saturable absorbers thus far is a trial and error procedure that is changing due to the correlation with more predictive procedures.

  20. Droplet deformation and fragmentation by ultra-short laser pulses

    CERN Document Server

    Krivokorytov, M S; Sidelnikov, Yu V; Krivtsun, V M; Medvedev, V V; Kompanets, V O; Lash, A A; Koshelev, K N

    2016-01-01

    We report on the experimental studies of the deformation and fragmentation of liquid metal droplets by picosecond and subpicosecond laser pulses. The experiments were performed with laser irradiance varying in 10E13-10E15 W/cm^2 range. The observed evolution of the droplet shape upon the impact dramatically differs from the previously reported for nanosecond laser pulses. Instead of flattening the droplet undergoes rapid asymmetric expansion and transforms into a complex shape which can be interpreted as two conjunct spheroid shells and finally fragments. We explain the described hydrodynamic response to the ultra-short impact as a result of the propagation of the laser-induced convergent shockwave through the volume of droplet.

  1. Computational modeling of ultra-short-pulse ablation of enamel

    Energy Technology Data Exchange (ETDEWEB)

    London, R.A.; Bailey, D.S.; Young, D.A. [and others

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  2. Short-Pulse Laser-Matter Computational Workshop Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Town, R; Tabak, M

    2004-11-02

    For three days at the end of August 2004, 55 plasma scientists met at the Four Points by Sheraton in Pleasanton to discuss some of the critical issues associated with the computational aspects of the interaction of short-pulse high-intensity lasers with matter. The workshop was organized around the following six key areas: (1) Laser propagation/interaction through various density plasmas: micro scale; (2) Anomalous electron transport effects: From micro to meso scale; (3) Electron transport through plasmas: From meso to macro scale; (4) Ion beam generation, transport, and focusing; (5) ''Atomic-scale'' electron and proton stopping powers; and (6) K{alpha} diagnostics.

  3. Optical soliton communication using ultra-short pulses

    CERN Document Server

    Sadegh Amiri, Iraj

    2015-01-01

    This brief analyzes the characteristics of a microring resonator (MRR) to perform communication using ultra-short soliton pulses. The raising of nonlinear refractive indices, coupling coefficients and radius of the single microring resonator leads to decrease in input power and round trips wherein the bifurcation occurs. As a result, bifurcation or chaos behaviors are seen at lower input power of 44 W, where the nonlinear refractive index is n2=3.2×10−20 m2/W. Using a decimal convertor system, these ultra-short signals can be converted into quantum information. Results show that multi solitons with FWHM and FSR of 10 pm and 600 pm can be generated respectively. The multi optical soliton with FWHM and FSR of 325 pm and 880 nm can be incorporated with a time division multiple access (TDMA) system wherein the transportation of quantum information is performed.

  4. Short-pulse laser heating of metals: a new approach

    Science.gov (United States)

    Huettner, Bernd

    1997-04-01

    Recently, several groups have demonstrated that the spatial and temporal temperature distribution inside metals resulting from femtosecond laser pulses cannot be fully explained by the two-temperature model for the electrons and phonons. Since these short pulse lengths may be comparable to the electron temperature relaxation time, we introduce a heat flow which is nonlocal in time. By this way we are taking into account in first order a non-equilibrium distribution of the electrons. As a consequence, three additional terms appear in the differential equation for the electron temperature. Furthermore, we offer an explanation for the different response of metals to the laser radiation on the basis of the electron-phonon coupling constant and the average phonon frequencies squared, well-known quantities in McMillan's theory on superconductivity. Using a double temperature model with nonlocal heat flow and a laser pulse length of 1 ps, the calculated surface temperatures of the electron and phonon subsystems are presented for Cu, Nb, and Pb. This is compared with the results of a local heat flow approach and with the conventional theory as well. Additionally we present calculations of the electron surface temperature of a thin Au film. We find that our model is capable of describing the new measurements on Au films more consistently than the standard double temperature model.

  5. Measurement of Ultra-Short Solitary Electromagnetic Pulses

    Directory of Open Access Journals (Sweden)

    Eva Gescheidtova

    2004-01-01

    Full Text Available In connection with the events of the last few years and with the increased number of terrorist activities, the problem of identification and measurement of electromagnetic weapons or other systems impact occurred. Among these are also microwave sources, which can reach extensive peak power of up to Pmax = 100 MW. Solitary, in some cases several times repeated, impulses lasting from tp E <1, 60>ns, cause the destruction of semiconductor junctions. These days we can find scarcely no human activity, where semiconductor structures are not used. The problem of security support of the air traffic, transportation, computer nets, banks, national strategic data canter’s, and other applications crops up. Several types of system protection from the ultra-short electromagnetic pulses present itself, passive and active protection. The analysis of the possible measuring methods, convenient for the identification and measurement of the ultra-short solitary electromagnetic pulses in presented in this paper; some of the methods were chosen and used for practical measurement. This work is part of Research object MSM262200022 "Research of microelectronic systems".

  6. Using ultra-short pulses to determine particle size and density distributions

    NARCIS (Netherlands)

    Lee, Christopher James; van der Slot, Petrus J.M.; Boller, Klaus J.

    2007-01-01

    We analyze the time dependent response of strongly scattering media (SSM) to ultra-short pulses of light. A random walk technique is used to model the optical scattering of ultra-short pulses of light propagating through media with random shapes and various packing densities. The pulse spreading was

  7. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos; Lozovoy, Vadim V.; Comstock, Matthew

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  8. Studying the mechanism of micromachining by short pulsed laser

    Science.gov (United States)

    Gadag, Shiva

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

  9. High-energy ultra-short pulse thin-disk lasers: new developments and applications

    Science.gov (United States)

    Michel, Knut; Klingebiel, Sandro; Schultze, Marcel; Tesseit, Catherine Y.; Bessing, Robert; Häfner, Matthias; Prinz, Stefan; Sutter, Dirk; Metzger, Thomas

    2016-03-01

    We report on the latest developments at TRUMPF Scientific Lasers in the field of ultra-short pulse lasers with highest output energies and powers. All systems are based on the mature and industrialized thin-disk technology of TRUMPF. Thin Yb:YAG disks provide a reliable and efficient solution for power and energy scaling to Joule- and kW-class picosecond laser systems. Due to its efficient one dimensional heat removal, the thin-disk exhibits low distortions and thermal lensing even when pumped under extremely high pump power densities of 10kW/cm². Currently TRUMPF Scientific Lasers develops regenerative amplifiers with highest average powers, optical parametric amplifiers and synchronization schemes. The first few-ps kHz multi-mJ thin-disk regenerative amplifier based on the TRUMPF thindisk technology was developed at the LMU Munich in 20081. Since the average power and energy have continuously been increased, reaching more than 300W (10kHz repetition rate) and 200mJ (1kHz repetition rate) at pulse durations below 2ps. First experiments have shown that the current thin-disk technology supports ultra-short pulse laser solutions >1kW of average power. Based on few-picosecond thin-disk regenerative amplifiers few-cycle optical parametric chirped pulse amplifiers (OPCPA) can be realized. These systems have proven to be the only method for scaling few-cycle pulses to the multi-mJ energy level. OPA based few-cycle systems will allow for many applications such as attosecond spectroscopy, THz spectroscopy and imaging, laser wake field acceleration, table-top few-fs accelerators and laser-driven coherent X-ray undulator sources. Furthermore, high-energy picosecond sources can directly be used for a variety of applications such as X-ray generation or in atmospheric research.

  10. Experimental and numerical study of short pulse effects in FELs

    CERN Document Server

    Khodyachykh, S; Genz, H; Hessler, C; Richter, A; Asgekar, V

    2004-01-01

    We report the experimental and numerical investigations of the influence of short pulse effects occurring in FELs in different operational regimes for electron bunch lengths which are of the order of the slippage distance. Several observables such as the small signal gain, the macropulse power and the spectral distribution of the FEL radiation were determined experimentally within the constraints of the stable focus regime at the infrared FEL at the S- DALINAC and for the limit cycle regime at the Dutch near infrared FEL FELIX. The experimental findings were compared to predictions of numerical simulations based on the 1D time dependent code FEL1D-OSC. The agreement between experiment and simulation is good. Furthermore, the simulations reveal a chaotic behavior of the macropulses for specific values of the slippage as well as period-doubling, two effects that are predicted to show up in the spectral distribution.

  11. Experimental and numerical study of short pulse effects in FELs

    Science.gov (United States)

    Khodyachykh, S.; Brunken, M.; Genz, H.; Hessler, C.; Richter, A.; Asgekar, V.

    2004-09-01

    We report the experimental and numerical investigations of the influence of short pulse effects occurring in FELs in different operational regimes for electron bunch lengths which are of the order of the slippage distance. Several observables such as the small signal gain, the macropulse power and the spectral distribution of the FEL radiation were determined experimentally within the constraints of the stable focus regime at the infrared FEL at the S-DALINAC and for the limit cycle regime at the Dutch near infrared FEL FELIX. The experimental findings were compared to predictions of numerical simulations based on the 1D time dependent code FEL1D-OSC. The agreement between experiment and simulation is good. Furthermore, the simulations reveal a chaotic behavior of the macropulses for specific values of the slippage as well as period-doubling, two effects that are predicted to show up in the spectral distribution.

  12. Polarization operator approach to pair creation in short laser pulses

    CERN Document Server

    Meuren, Sebastian; Keitel, Christoph H; Di Piazza, Antonino

    2014-01-01

    We investigate the nonlinear Breit-Wheeler process inside short laser pulses, i.e. the creation of an electron-positron pair induced by a gamma photon inside a plane-wave background field. To obtain the total pair-creation probability we verify (to leading-order) the cutting rule for the polarization operator in the realm of strong-field QED by an explicit calculation. Furthermore, a double-integral representation for the leading-order contribution to the field-dependent part of the polarization operator is derived. The combination of both results yields a compact expression for the total pair-creation probability inside an arbitrary plane-wave background field. It is shown numerically that with presently available technology pair-creation probabilities of the order of ten percent could be reached for a single gamma photon.

  13. Analytical study of ultra-short pulse reflectometry

    Energy Technology Data Exchange (ETDEWEB)

    Bruskin, L.G. [Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Mukoyama, Nakamachi, Naka-gun, Ibaraki-ken (Japan)]. E-mail: bruskinl@fusion.naka.jaeri.go.jp; Mase, A.; Yamamoto, A.; Kogi, Y. [Kyushu University, Advanced Science and Technology Center for Cooperative Research, Fukuoka-ken, Kasuga (Japan)

    2001-10-01

    The results of an analytical treatment of the time-dependent 2D full-wave equation are presented here for the case of ultra-short pulse (USP) reflectometry. We consider several models of the plasma geometry, namely linear and nonlinear slab models, as well as a 2D plasma density profile with cylindrical symmetry. The latter model is more realistic when compared to the 1D stratified plasma models previously employed in all the analytical, and most numerical, treatments, since the plasma in fusion toroidal devices, mirror machines and plasma processing chambers can often be considered axially symmetric on the scale relevant to microwave reflectometry. Based on the results of analytical modelling, a signal record analysis method of profile reconstruction is proposed. The method has the advantage of using raw signal records instead of poorly localized frequency modes, which makes it robust for the profile measurements using USP reflectometry. (author)

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

    Science.gov (United States)

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

    2015-02-01

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

  15. Short infrared (IR) laser pulses can induce nanoporation

    Science.gov (United States)

    Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.; Glickman, Randolph D.; Beier, Hope T.

    2016-03-01

    Short infrared (IR) laser pulses on the order of hundreds of microseconds to single milliseconds with typical wavelengths of 1800-2100 nm, have shown the capability to reversibly stimulate action potentials (AP) in neuronal cells. While the IR stimulation technique has proven successful for several applications, the exact mechanism(s) underlying the AP generation has remained elusive. To better understand how IR pulses cause AP stimulation, we determined the threshold for the formation of nanopores in the plasma membrane. Using a surrogate calcium ion, thallium, which is roughly the same shape and charge, but lacks the biological functionality of calcium, we recorded the flow of thallium ions into an exposed cell in the presence of a battery of channel antagonists. The entry of thallium into the cell indicated that the ions entered via nanopores. The data presented here demonstrate a basic understanding of the fundamental effects of IR stimulation and speculates that nanopores, formed in response to the IR exposure, play an upstream role in the generation of AP.

  16. Measurement of Ultra-Short Single-Photon Pulse Duration with Two-Photon Interference

    Institute of Scientific and Technical Information of China (English)

    LV Fan; SUN Fang-Wen; ZOU Chang-Ling; HAN Zheng-Fu; GUO Guang-Can

    2011-01-01

    We proposed a protocol of measuring the duration of ultra-short single-photon pulse with two-photon interference.The pulse duration can be obtained from the width of the visibility of two-photon Hong-Ou-Mandel interference or the indistinguishability of the two photons. Moreover, the shape of a single-photon pulse can be measured with ultra-short single-photon pulses through the two-photon interference.%@@ We proposed a protocol of measuring the duration of ultra-short single-photon pulse with two-photon interference.The pulse duration can be obtained from the width of the visibility of two-photon Hong-Ou-Mandel interference or the indistinguishability of the two photons.Moreover, the shape of a single-photon pulse can be measured with ultra-short single-photon pulses through the two-photon interference.

  17. Extremal projectors for contragredient Lie (super)symmetries (short review)

    CERN Document Server

    Tolstoy, V N

    2010-01-01

    A brief review of the extremal projectors for contragredient Lie (super)symmetries (finite-dimensional simple Lie algebras, basic classical Lie superalgebras, infinite-dimensional affine Kac-Moody algebras and superalgebras, as well as their quantum $q$-analogs) is given. Some bibliographic comments on the applications of extremal projectors are presented.

  18. Analysis of ultra-short pulse shaping with programmable amplitude and phase masks

    Institute of Scientific and Technical Information of China (English)

    Shanhong You; Weidong Shao; Wenfeng Cai; Honglong Cao; M. Kavehrad

    2011-01-01

    @@ Specified ultra-short pulse waveforms could be synthesized with high-resolution zero-dispersion pulse shaping system.The system and parameters are analyzed and discussed.The pulse shaping system with optimized parameters could resolve the frequency components of ultra-broad bandwidth pulse and prevent the spatial shaping of individual frequency components.The specified waveforms, Meyer wavelet and square root raised cosine pulses, are generated with programmable amplitude and phase masks.%Specified ultra-short pulse waveforms could be synthesized with high-resolution zero-dispersion pulse shaping system. The system and parameters are analyzed and discussed. The pulse shaping system with optimized parameters could resolve the frequency components of ultra-broad bandwidth pulse and prevent the spatial shaping of individual frequency components. The specified waveforms, Meyer wavelet and square root raised cosine pulses, are generated with programmable amplitude and phase masks.

  19. Spin-resolved photoelectron spectroscopy using femtosecond extreme ultraviolet light pulses from high-order harmonic generation

    Science.gov (United States)

    Plötzing, M.; Adam, R.; Weier, C.; Plucinski, L.; Eich, S.; Emmerich, S.; Rollinger, M.; Aeschlimann, M.; Mathias, S.; Schneider, C. M.

    2016-04-01

    The fundamental mechanism responsible for optically induced magnetization dynamics in ferromagnetic thin films has been under intense debate since almost two decades. Currently, numerous competing theoretical models are in strong need for a decisive experimental confirmation such as monitoring the triggered changes in the spin-dependent band structure on ultrashort time scales. Our approach explores the possibility of observing femtosecond band structure dynamics by giving access to extended parts of the Brillouin zone in a simultaneously time-, energy- and spin-resolved photoemission experiment. For this purpose, our setup uses a state-of-the-art, highly efficient spin detector and ultrashort, extreme ultraviolet light pulses created by laser-based high-order harmonic generation. In this paper, we present the setup and first spin-resolved spectra obtained with our experiment within an acquisition time short enough to allow pump-probe studies. Further, we characterize the influence of the excitation with femtosecond extreme ultraviolet pulses by comparing the results with data acquired using a continuous wave light source with similar photon energy. In addition, changes in the spectra induced by vacuum space-charge effects due to both the extreme ultraviolet probe- and near-infrared pump-pulses are studied by analyzing the resulting spectral distortions. The combination of energy resolution and electron count rate achieved in our setup confirms its suitability for spin-resolved studies of the band structure on ultrashort time scales.

  20. Overview of LANL short-pulse ion acceleration activities

    Energy Technology Data Exchange (ETDEWEB)

    Flippo, Kirk A. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Schmitt, Mark J. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Offermann, Dustin [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Cobble, James A. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Gautier, Donald [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Kline, John [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Workman, Jonathan [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Archuleta, Fred [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Gonzales, Raymond [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Hurry, Thomas [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Johnson, Randall [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Letzring, Samuel [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Montgomery, David [Los Alamos National Laboratory; Reid, Sha-Marie [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Shimada, Tsutomu [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Gaillard, Sandrine A. [Univ. of Nevada, Reno, NV (United States); Sentoku, Yasuhiko [Univ. of Nevada, Reno, NV (United States); Bussman, Michael [Forschungszentrum Dresden (Germany); Kluge, Thomas [Forschungszentrum Dresden (Germany); Cowan, Thomas E. [Forschungszentrum Dresden (Germany); Rassuchine, Jenny M. [Forschungszentrum Dresden - Rossendorf (Germany); Lowenstern, Mario E. [Univ. of Michigan, Ann Arbor, MI (United States); Mucino, J. Eduardo [Univ. of Michigan, Ann Arbor, MI (United States); Gall, Brady [Univ. of Missouri, Columbia, MO (United States); Korgan, Grant [Nanolabz, Reno, NV (United States); Malekos, Steven [Nanolabz, Reno, NV (United States); Adams, Jesse [Nanolabz, Reno, NV (United States); Bartal, Teresa [Univ. of California, San Diego, CA (United States); Chawla, Surgreev [Univ. of California, San Diego, CA (United States); Higginson, Drew [Univ. of California, San Diego, CA (United States); Beg, Farhat [Univ. of California, San Diego, CA (United States); Nilson, Phil [Lab. for Laser Energetics, Rochester, NY (United States); Mac Phee, Andrew [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Le Pape, Sebastien [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Hey, Daniel [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Mac Kinnon, Andy [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Geissel, Mattias [Sandia National Lab. (SNL), Albuquerque, NM (United States); Schollmeier, Marius [Sandia National Lab. (SNL), Albuquerque, NM (United States); Stephens, Rich [General Atomics, San Diego, CA (United States)

    2009-12-02

    An overview of Los Alamos National Laboratory's activities related to short-pulse ion acceleration is presented. LANL is involved is several projects related to Inertial Confinement Fusion (Fast Ignition) and Laser-Ion Acceleration. LANL has an active high energy X-ray backlighter program for radiographing ICF implosions and other High Energy Density Laboratory Physics experiments. Using the Trident 200TW laser we are currently developing high energy photon (>10 keV) phase contrast imaging techniques to be applied on Omega and the NIF. In addition we are engaged in multiple programs in laser ion acceleration to boost the ion energies and efficiencies for various potential applications including Fast Ignition, active material interrogation, and medical applications. Two basic avenues to increase ion performance are currently under study: one involves ultra-thin targets and the other involves changing the target geometry. We have recently had success in boosting proton energies above 65 MeV into the medical application range. Highlights covered in the presentation include: The Trident Laser System; X-ray Phase Contrast Imaging for ICF and HEDLP; Improving TNSA Ion Acceleration; Scaling Laws; Flat Targets; Thin Targets; Cone Targets; Ion Focusing;Trident; Omega EP; Scaling Comparisons; and, Conclusions.

  1. Computational design of short pulse laser driven iron opacity experiments

    Science.gov (United States)

    Martin, M. E.; London, R. A.; Goluoglu, S.; Whitley, H. D.

    2017-02-01

    The resolution of current disagreements between solar parameters calculated from models and observations would benefit from the experimental validation of theoretical opacity models. Iron's complex ionic structure and large contribution to the opacity in the radiative zone of the sun make iron a good candidate for validation. Short pulse lasers can be used to heat buried layer targets to plasma conditions comparable to the radiative zone of the sun, and the frequency dependent opacity can be inferred from the target's measured x-ray emission. Target and laser parameters must be optimized to reach specific plasma conditions and meet x-ray emission requirements. The HYDRA radiation hydrodynamics code is used to investigate the effects of modifying laser irradiance and target dimensions on the plasma conditions, x-ray emission, and inferred opacity of iron and iron-magnesium buried layer targets. It was determined that plasma conditions are dominantly controlled by the laser energy and the tamper thickness. The accuracy of the inferred opacity is sensitive to tamper emission and optical depth effects. Experiments at conditions relevant to the radiative zone of the sun would investigate the validity of opacity theories important to resolving disagreements between solar parameters calculated from models and observations.

  2. Optical Constants of Ultra-Short-Pulse Laser Heated Metal

    Science.gov (United States)

    Yoneda, Hitoki; Morikami, Hidetoshi; Ueda, Ken-Ichi; More, Richard M.

    The complex refractive index (n + ik) of ultra-short-pulse laser heated gold metal was measured with a new ellipsometric pump-probe technique. Two ratios of four different probe-beam polarizations were used to determine s- and p-reflectivity and their phase difference. In the early stage of heating, only the imaginary part of the dielectric constant ɛ(Im[ɛ] = 2nk) increased while real part of e (Re[ɛ] = n²-k²) was almost constant. This agrees with the Drude model. We observe a pause in the rise of Im[ɛ] at the boiling temperature. Beyond this point, Re[ɛ] started to change and the observed parameters disagree with the Drude theory. It was found that the parameters of the expanding plasma follow a unique trajectory in n, k space, even though time variation of Re[ɛ] and Im[ɛ] are different for various pump intensities. This means the gold remains in a unique state such as the neutral groundstate in this intensity range.

  3. A high current, short pulse electron source for wakefield accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Ching-Hung

    1992-12-31

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  4. A high current, short pulse electron source for wakefield accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Ching-Hung.

    1992-01-01

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  5. Ultra-wideband short-pulse radar with range accuracy for short range detection

    Science.gov (United States)

    Rodenbeck, Christopher T; Pankonin, Jeffrey; Heintzleman, Richard E; Kinzie, Nicola Jean; Popovic, Zorana P

    2014-10-07

    An ultra-wideband (UWB) radar transmitter apparatus comprises a pulse generator configured to produce from a sinusoidal input signal a pulsed output signal having a series of baseband pulses with a first pulse repetition frequency (PRF). The pulse generator includes a plurality of components that each have a nonlinear electrical reactance. A signal converter is coupled to the pulse generator and configured to convert the pulsed output signal into a pulsed radar transmit signal having a series of radar transmit pulses with a second PRF that is less than the first PRF.

  6. Thin film surface processing by UltraShort Laser Pulses (USLP)

    NARCIS (Netherlands)

    Scorticati, D.; Skolski, J.Z.P.; Römer, G.R.B.E.; Huis in 't Veld, A.J.; Workum, M.; Theelen, M.J.; Zeman, M.

    2012-01-01

    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed las

  7. Mitigation of Electromagnetic Pulse (EMP) Effects from Short-Pulse Lasers and Fusion Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Eder, D C; Throop, A; Brown, Jr., C G; Kimbrough, J; Stowell, M L; White, D A; Song, P; Back, N; MacPhee, A; Chen, H; DeHope, W; Ping, Y; Maddox, B; Lister, J; Pratt, G; Ma, T; Tsui, Y; Perkins, M; O' Brien, D; Patel, P

    2009-03-06

    Our research focused on obtaining a fundamental understanding of the source and properties of EMP at the Titan PW(petawatt)-class laser facility. The project was motivated by data loss and damage to components due to EMP, which can limit diagnostic techniques that can be used reliably at short-pulse PW-class laser facilities. Our measurements of the electromagnetic fields, using a variety of probes, provide information on the strength, time duration, and frequency dependence of the EMP. We measure electric field strengths in the 100's of kV/m range, durations up to 100 ns, and very broad frequency response extending out to 5 GHz and possibly beyond. This information is being used to design shielding to mitigate the effects of EMP on components at various laser facilities. We showed the need for well-shielded cables and oscilloscopes to obtain high quality data. Significant work was invested in data analysis techniques to process this data. This work is now being transferred to data analysis procedures for the EMP diagnostics being fielded on the National Ignition Facility (NIF). In addition to electromagnetic field measurements, we measured the spatial and energy distribution of electrons escaping from targets. This information is used as input into the 3D electromagnetic code, EMSolve, which calculates time dependent electromagnetic fields. The simulation results compare reasonably well with data for both the strength and broad frequency bandwidth of the EMP. This modeling work required significant improvements in EMSolve to model the fields in the Titan chamber generated by electrons escaping the target. During dedicated Titan shots, we studied the effects of varying laser energy, target size, and pulse duration on EMP properties. We also studied the effect of surrounding the target with a thick conducting sphere and cube as a potential mitigation approach. System generated EMP (SGEMP) in coaxial cables does not appear to be a significant at Titan. Our

  8. Modulational instability of short pulses in long optical fibers

    DEFF Research Database (Denmark)

    Shukla, P. K.; Juul Rasmussen, Jens

    1986-01-01

    The effect of time-derivative nonlinearity is incorporated into the study of the modulational instability of heat pulses propagating through long optical fibers. Conditions for soliton formation are discussed......The effect of time-derivative nonlinearity is incorporated into the study of the modulational instability of heat pulses propagating through long optical fibers. Conditions for soliton formation are discussed...

  9. Very-short-pulse modulator using asymmetric thyristors

    Science.gov (United States)

    Perol, P.

    1984-09-01

    The development of a semiconductor delay-line modulator for a 40-nsec/pulse 10-kHz-repetition-rate coaxial magnetron radar used to monitor airport runway traffic is reported and illustrated with circuit diagrams, output spectra, and photographs. The problems presented by the design specifications are indicated, and the solutions adopted (asymmetric press-packed thyristors and ferrite pulse transformer) are explained. Pulse widths and peak powers with 16 nf of delay line and a 2.5-kV charge at the level of the modulator are found to be 120 nsec and 58 kW without truncation and 40 nsec and 50-51 kW with truncation, the latter corresponding to an efficiency of 17 percent. The pulse leading edges have dI/dt at the transformer primary = 1.8 kA/microsec and dV/dt at the magnetron = 160 kV/microsec.

  10. Alignment of symmetric top molecules by short laser pulses

    DEFF Research Database (Denmark)

    Hamilton, Edward; Seideman, Tamar; Ejdrup, Tine

    2005-01-01

    Nonadiabatic alignment of symmetric top molecules induced by a linearly polarized, moderately intense picosecond laser pulse is studied theoretically and experimentally. Our studies are based on the combination of a nonperturbative solution of the Schrodinger equation with femtosecond time...

  11. Successful suppression of magnetization precession after short field pulses

    OpenAIRE

    Bauer, Martin; Lopusnik, Radek; Fassbender, Jürgen; Hillebrands, Burkard; Dötsch, H.

    2000-01-01

    For the next generation of high data rate magnetic recording above 1 Gbit/s, a better understanding of the switching processes for both recording heads and media will be required. In order to maximize the switch-ing speed for such devices, the magnetization precession after the magnetic field pulse termination needs to be suppressed to a maximum degree. It is demonstrated experimentally for ferrite films that the appropriate adjustment of the field pulse parameters and/or the static applied f...

  12. 2D simulations of short-pulsed dielectric barrier discharge xenon excimer lamp

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, E.A.; Kudryavtsev, A.A. [St. Petersburg State University, St. Petersburg (Russian Federation); Arslanbekov, R.R. [CFD Research Corporation, Huntsville (United States)

    2006-07-01

    Self-consistent two-dimensional (2D) simulations of short-pulsed dielectric barrier discharge (DBD) in pure xenon have been performed. It is shown that during short current pulse the traversal inhomogeneity of the plasma parameters can be important only at the end of the current pulse as an edge effect close to the side walls. During the current pulse, the gap voltage drops until the ionization wave reaches the cathode so the current in the cathode sheath is the displacement current. This means that almost all of the absorbed power is deposited into excitation of xenon atoms and not to the ion heating in the cathode sheath as in the traditional glow discharges. This fact is one of the reasons of high efficiency of short-pulsed DBD. The developed model allows one to estimate the temporal position of the plasma-sheath boundary. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Consequences of short electron-beam pulses in the FELIX project

    Science.gov (United States)

    Jaroszynski, D. A.; Oepts, D.; Van Der Meer, A. F. G.; Van Amersfoort, P. W.; Colson, W. B.

    1990-10-01

    We discuss the consequences of short micropulses on the output of infrared and far-infrared free electron lasers with special reference to the FELIX project which operates with 3 ps long electron pulses.

  14. Diffractive Interaction for Short Pulses in 2×2 System

    Institute of Scientific and Technical Information of China (English)

    YUAN Ming-sheng

    2008-01-01

    This paper studies the asymptotic behavior of the diffractive interaction of pulses with two linear phases of length ε << 1 in 2 × 2 semilinear strictly hyperbolic system with constant coefficients. By a formal analysis, it derives problems of profiles in the expansion of the pulse like solution with respect to the length ε, and obtains that the leading profile satisfies a nonlinear Schrodinger type system. The problems of profiles are solved, and the formal expansion is justified. It is observed that there is interaction between two phases starting at the third order profiles.

  15. Quantum coherent control of ultra short laser pulses

    Institute of Scientific and Technical Information of China (English)

    ZHOU JianYing; ZENG JianHua; LI JunTao

    2008-01-01

    The effective photonic control is one of the key issues in photo-physics. Significant advancement in photonic crystals, quantum optics, ultrafast optics as well as micro-nano-optics gives rise to new op-portunities to manipulate the emission and propagation in optical fields, leading to a number of new and interesting discoveries, e.g., ultrashort light pulse storage and efficient energy conversion. This paper reviews the latest research progress in storage, release and energy conversion for ultrashort laser pulses in periodical arrays of absorbing medium. Techniques to fabricate such devices are also presented.

  16. Detection of early dental caries with short pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, Nahoko; Goto, Shigeru [Osada Research Inst., Ltd., Tokyo (Japan); Tanaka, Hiroshi; Ohzu, Akira; Arisawa, Takashi [Japan Atomic Energy Research Inst., Kansai Research Establishment, Advanced Photon Research Center, Kyoto (Japan)

    2002-07-01

    Differences in the optical properties of polarization and photoluminescence between caries lesion and noncaries (sound) enamel have been investigated by focusing a pulsed Nd:YAG laser of 532 nm on the surface of teeth. Significant difference in the polarization property of the scattered light from the surface can be observed with some carious samples. For photoluminescence spectral lines which appear at around 650 nm, the intensity of caries lesion has been approximately two times higher than that of sound one. A discussion is presented in which early are potentially detectable by the pulsed laser. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Jared, Bradley Howell

    2010-03-01

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

  18. Pondermotive absorption of a short intense laser pulse in a non-uniform plasma

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A.A.; Platonov, K.Yu. [Inst. for Laser Physics, SC `Vavilov State Optical Inst.` 12, Birzhevaya line, St Petersburg (Russian Federation); Tanaka, K.A.

    1998-03-01

    An analytical description of the pondermotive absorption mechanism at a short high intense laser pulse interaction with a strong inhomogeneous plasma is presented. The optimal conditions for the maximum of resonance absorption of laser pulse interaction with non-uniform plasma at normal incidence are founded. (author)

  19. Saturation properties of four-wave mixing between short optical pulses in semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, A.; Diez, S.

    1999-01-01

    Summary form only given. The authors report the first comparison between theory and experiment on the four wave mixing between trains of short pulses in semiconductor optical amplifiers. The theory is able to explain all qualitative features seen in the experiment.......Summary form only given. The authors report the first comparison between theory and experiment on the four wave mixing between trains of short pulses in semiconductor optical amplifiers. The theory is able to explain all qualitative features seen in the experiment....

  20. Using short pulses to enhance the production rate of vibrationally excited hydrogen molecules in hydrogen discharge

    Institute of Scientific and Technical Information of China (English)

    Sun Ji-Zhong; Li Xian-Tao; Bai Jing; Wang De-Zhen

    2012-01-01

    Hydrogen discharges driven by the combined radio-frequency(rf)/short pulse sources are investigated using the particle-in-cell method.The simulation results show that the discharge driven additionally by the short pulse can enhance the electron density and modulate the electron energy to provide a better condition for negative hydrogen ion production than the discharge driven by the rf-only source.

  1. Electron Dynamics During High-Power, Short-Pulsed Laser Interactions with Solids and Interfaces

    Science.gov (United States)

    2016-06-28

    PAPER ALSO RECEIVED EXTERNAL MEDIA COVERENCE FROM SIGNAL MAGAZINE : http://www.afcea.org/content/?q=Article-scientists-harness- energy -heat Edited...AFRL-AFOSR-VA-TR-2016-0234 Electron Dynamics During High- Power , Short-Pulsed Laser Interactions with Solids and Interfaces Patrick Hopkins...Dynamics During High- Power , Short-Pulsed Laser Interactions with Solids and Interfaces 5a. CONTRACT NUMBER FA9550-13-1-0067 5b. GRANT NUMBER 5c

  2. Short pulse equations and localized structures in frequency band gaps of nonlinear metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tsitsas, N.L. [School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografos, Athens 15773 (Greece); Horikis, T.P. [Department of Mathematics, University of Ioannina, Ioannina 45110 (Greece); Shen, Y.; Kevrekidis, P.G.; Whitaker, N. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-4515 (United States); Frantzeskakis, D.J., E-mail: dfrantz@phys.uoa.g [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 157 84 (Greece)

    2010-03-01

    We consider short pulse propagation in nonlinear metamaterials characterized by a weak Kerr-type nonlinearity in their dielectric response. Two short-pulse equations (SPEs) are derived for the high- and low-frequency 'band gaps' (where linear electromagnetic waves are evanescent) with linear effective permittivity epsilon<0 and permeability mu>0. The structure of the solutions of the SPEs is also briefly discussed, and connections with the soliton solutions of the nonlinear Schroedinger equation are made.

  3. Ionized sputter deposition using an extremely high plasma density pulsed magnetron discharge

    Energy Technology Data Exchange (ETDEWEB)

    Macak, Karol [Department of Physics, Linkoeping University, SE-581 83 Linkoeping, (Sweden); Kouznetsov, Vladimir [Department of Physics, Linkoeping University, SE-581 83 Linkoeping, (Sweden); Schneider, Jochen [Department of Physics, Linkoeping University, SE-581 83 Linkoeping, (Sweden); Helmersson, Ulf [Department of Physics, Linkoeping University, SE-581 83 Linkoeping, (Sweden); Petrov, Ivan [Materials Science Department and Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States)

    2000-07-01

    Time resolved plasma probe measurements of a novel high power density pulsed plasma discharge are presented. Extreme peak power densities in the pulse (on the order of several kW cm{sup -2}) result in a very dense plasma with substrate ionic flux densities of up to 1 A cm{sup -2} at source-to-substrate distances of several cm and at a pressure of 0.13 Pa (1 mTorr). The pulse duration was {approx}100 {mu}s with a pulse repetition frequency of 50 Hz. The plasma consists of metallic and inert gas ions, as determined from time resolved Langmuir probe measurements and in situ optical emission spectroscopy data. It was found that the plasma composition at the beginning of the pulse was dominated by Ar ions. As time elapsed metal ions were detected and finally dominated the ion composition. The effect of the process parameters on the temporal development of the ionic fluxes is discussed. The ionized portion of the sputtered metal flux was found to have an average velocity of 2500 m s{sup -1} at 6 cm distance from the source, which conforms to the collisional cascade sputtering theory. The degree of ionization of the sputtered metal flux at a pressure of 0.13 Pa was found to be 40%{+-}20% by comparing the total flux of deposited atoms with the charge measured for the metal ions in the pulse. (c) 2000 American Vacuum Society.

  4. Extremely Nonlinear Optics Using Shaped Pulses Spectrally Broadened in an Argon- or Sulfur Hexafluoride-Filled Hollow-Core Fiber

    OpenAIRE

    Andreas Hoffmann; Michael Zürch; Christian Spielmann

    2015-01-01

    In this contribution we present a comparison of the performance of spectrally broadened ultrashort pulses using a hollow-core fiber either filled with argon or sulfur hexafluoride (SF6) for demanding pulse-shaping experiments. The benefits of both gases for pulse-shaping are studied in the highly nonlinear process of high-harmonic generation. In this setup, temporally shaping the driving laser pulse leads to spectrally shaping of the output extreme ultraviolet (XUV) spectrum, where total yie...

  5. Second serial transverse enteroplasty procedure in an infant with extreme short bowel syndrome.

    Science.gov (United States)

    Oh, Jung-Tak; Koh, Hong; Chang, Eun Young; Chang, Hye Kyung; Han, Seok Joo

    2012-06-01

    The serial transverse enteroplasty (STEP) procedure is a novel technique to lengthen and taper the bowel in patients with short bowel syndrome. The advantages of STEP include not only technical ease and simplicity, but also the ability to repeat the procedure. Herein, we report a case of extreme short bowel syndrome that was successfully treated by the second STEP procedure. A 3-day old newborn girl underwent STEP because of jejunal atresia with the small bowel length of 15 cm, but her bowel elongation was not enough to escape from short bowel syndrome. At the age of 6 months, she underwent a second STEP procedure. The bowel lengthening by the second STEP made her tolerable to enteral feeding with body weight gain and rescued her from short bowel syndrome. This case showed that second STEP is very helpful in treatment of extreme short bowel syndrome.

  6. Short-Pulse Amplification by Strongly-Coupled Brillouin Scattering

    CERN Document Server

    Edwards, Matthew R; Mikhailova, Julia M; Fisch, Nathaniel J

    2016-01-01

    We examine the feasibility of strongly-coupled stimulated Brillouin scattering as a mechanism for the plasma-based amplification of sub-picosecond pulses. In particular, we use fluid theory and particle-in-cell simulations to compare the relative advantages of Raman and Brillouin amplification over a broad range of achievable parameters.

  7. Ultra-short pulsed millimeter-wave laser

    Science.gov (United States)

    Wilson, Thomas

    2000-10-01

    High peak power pulses of 1.22-mm wavelength radiation have recently been obtained from a novel cavity-dumped far-infrared optically-pumped laser^1. Smooth reproducible pulses with the following characteristics have been routinely obtained: peak power=25-kW, pulsewidth (FWHM)=5-ns, repetition rate=10 pps. (This compares favorably to typical far-infrared, cavity-dumped output - 11-kW, 30-ns, 1 pps - available from the University of California - Santa Barbara Free Electron Laser). The pumping laser is a grating-tuned, hybrid TEA CO2 laser providing 1J / pulse at the 9P32 transition. The far-infrared gain medium is isotopic (C^13) methyl flouride. Experiments are underway for using the novel source to resonantly excite coherent pulses of 250-GHz longitudinal acoustic phonons in silicon doping superlattices. ^1 Thomas E. Wilson, "Modeling the high-speed switching of far-infrared radiation by photoionization in a semiconductor", Phys. Rev. B 59 (20), 12996 (1999).

  8. High Energy, Short Pulse Fiber Injection Lasers at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, J W; Messerly, M J; Phan, H H; Crane, J K; Beach, R J; Siders, C W; Barty, C J

    2008-09-10

    A short pulse fiber injection laser for the Advanced Radiographic Capability (ARC) on the National Ignition Facility (NIF) has been developed at Lawrence Livermore National Laboratory (LLNL). This system produces 100 {micro}J pulses with 5 nm of bandwidth centered at 1053 nm. The pulses are stretched to 2.5 ns and have been recompressed to sub-ps pulse widths. A key feature of the system is that the pre-pulse power contrast ratio exceeds 80 dB. The system can also precisely adjust the final recompressed pulse width and timing and has been designed for reliable, hands free operation. The key challenges in constructing this system were control of the signal to noise ratio, dispersion management and managing the impact of self phase modulation on the chirped pulse.

  9. Measurement and compensation schemes for the pulse front distortion of ultra-intensity ultra-short laser pulses

    Science.gov (United States)

    Wu, Fenxiang; Xu, Yi; Yu, Linpeng; Yang, Xiaojun; Li, Wenkai; Lu, Jun; Leng, Yuxin

    2016-11-01

    Pulse front distortion (PFD) is mainly induced by the chromatic aberration in femtosecond high-peak power laser systems, and it can temporally distort the pulse in the focus and therefore decrease the peak intensity. A novel measurement scheme is proposed to directly measure the PFD of ultra-intensity ultra-short laser pulses, which can work not only without any extra struggle for the desired reference pulse, but also largely reduce the size of the required optical elements in measurement. The measured PFD in an experimental 200TW/27fs laser system is in good agreement with the calculated result, which demonstrates the validity and feasibility of this method effectively. In addition, a simple compensation scheme based on the combination of concave lens and parabolic lens is also designed and proposed to correct the PFD. Based on the theoretical calculation, the PFD of above experimental laser system can almost be completely corrected by using this compensator with proper parameters.

  10. PHz-wide Supercontinua of Nondispersing Subcycle Pulses Generated by Extreme Modulational Instability

    Science.gov (United States)

    Tani, F.; Travers, J. C.; Russell, P. St. J.

    2013-07-01

    Modulational instability (MI) of 500 fs, 5μJ pulses, propagating in gas-filled hollow-core kagome photonic crystal fiber, is studied numerically and experimentally. By tuning the pressure and launched energy, we control the duration of the pulses emerging as a consequence of MI and hence are able to study two regimes: the classical MI case leading to few-cycle solitons of the nonlinear Schrödinger equation; and an extreme case leading to the formation of nondispersing subcycle pulses (0.5 to 2 fs) with peak intensities of order 1014Wcm-2. Insight into the two regimes is obtained using a novel statistical analysis of the soliton parameters. Numerical simulations and experimental measurements show that, when a train of these pulses is generated, strong ionization of the gas occurs. This extreme MI is used to experimentally generate a high energy (>1μJ) and spectrally broad supercontinuum extending from the deep ultraviolet (320 nm) to the infrared (1300 nm).

  11. Time-dependent Bragg diffraction and short-pulse reflection by one-dimensional photonic crystals

    CERN Document Server

    André, Jean-michel

    2015-01-01

    The time-dependence of the Bragg diffraction by one-dimensional photonic crystals and its influence on the short pulse reflection are studied in the framework of the coupled- wave theory. The indicial response of the photonic crystal is calculated and it appears that it presents a time-delay effect with a transient time conditioned by the extinction length. A numerical simulation is presented for a Bragg mirror in the x-ray domain and a pulse envelope modelled by a sine-squared shape. The potential consequences of the time-delay effect in time-dependent optics of short-pulses are emphasized.

  12. Stimulated recombination of antiproton and positron with ultra-short ultra-high intensity laser pulse

    CERN Document Server

    Ryabinina, M V

    2003-01-01

    Ionization of hydrogen atom in the field of high-intense ultra-short femto-second laser pulse recently became the subject of comprehensive theoretical approaches. On the other hand, there exists experimental evidence that short electric pulses can effectively stimulate electron-proton (as well as antiproton-positron) recombination to high-level (Rydberg) state. In this paper we present the results of the theoretical estimations of antiproton-positron recombination cross-section in cold mixed plasmas in traps in the conditions of ATHENA/ATRAP experiments in CERN under the action of sub-fs laser pulse with TW intensity. (2 refs).

  13. Short Pulse Dynamics in Strongly Nonlinear Dissipative Granular Chains

    OpenAIRE

    Rosas, Alexandre; Romero, Aldo H.; Nesterenko, Vitali F.; Lindenberg, Katja

    2008-01-01

    We study the energy decay properties of a pulse propagating in a strongly nonlinear granular chain with damping proportional to the relative velocity of the grains. We observe a wave disturbance that at low viscosities consists of two parts exhibiting two entirely different time scales of dissipation. One part is an attenuating solitary wave, is dominated by discreteness and nonlinearity effects as in a dissipationless chain, and has the shorter lifetime. The other is a purely dissipative sho...

  14. Cross sections for short pulse single and double ionization ofhelium

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, Alicia; Rescigno, Thomas N.; McCurdy, C. William

    2007-11-27

    In a previous publication, procedures were proposed for unambiguously extracting amplitudes for single and double ionization from a time-dependent wavepacket by effectively propagating for an infinite time following a radiation pulse. Here we demonstrate the accuracy and utility of those methods for describing two-photon single and one-photon double ionization of helium. In particular it is shown how narrow features corresponding to autoionizing states are easily resolved with these methods.

  15. Strong Field Molecular Ionization in the Impulsive Limit: Freezing Vibrations with Short Pulses

    CERN Document Server

    Sándor, Péter; Zhao, Arthur; Rozgonyi, Tamás; Ruckenbauer, Matthias; Marquetand, Philipp; Weinacht, Thomas

    2016-01-01

    We study strong-field molecular ionization as a function of pulse duration. Experimental measurements of the photoelectron yield for a number of molecules reveal competition between different ionization continua (cationic states) which depends strongly on pulse duration. Surprisingly, in the limit of short pulse duration, we find that a single ionic continuum dominates the yield, whereas multiple continua are produced for longer pulses. Using calculations which take vibrational dynamics into account, we interpret our results in terms of nuclear motion and non-adiabatic dynamics during the ionization process.

  16. Dual wavelength laser damage mechanisms in the ultra-short pulse regime

    Science.gov (United States)

    Gyamfi, Mark; Costella, Marion; Willemsen, Thomas; Jürgens, Peter; Mende, Mathias; Jensen, Lars; Ristau, Detlev

    2016-12-01

    New ultrashort pulse laser systems exhibit an ever increasing performance which includes shorter pulses and higher pulse energies. Optical components used in these systems are facing increasing requirements regarding their durability, and therefore understanding of the damage mechanism is crucial. In the ultra-short pulse regime electron ionization processes control the damage mechanisms. For the single wavelength, single pulse regime the Keldysh [1] and the Drude model [2] allow a quantitative description of these ionization processes. However, in this model, the electrical field is restricted to a single wavelength, and therefore it cannot be applied in the case of irradiation with two pulses at different wavelengths. As frequency conversion is becoming more common in ultra-short pulse applications, further research is needed in this field to predict the damage resistance of optical components. We investigate the damage behavior of high reflective mirrors made of different metal oxide materials under simultaneous exposure to ultra-short pulses at the wavelengths 387.5 nm and 775 nm, respectively.

  17. Dynamic properties of a pulse-pumped fiber laser with a short, high-gain cavity

    Science.gov (United States)

    Yang, Chaolin; Guo, Junhong; Wei, Pu; Wan, Hongdan; Xu, Ji; Wang, Jin

    2016-09-01

    We demonstrate a pulsed high-gain all-fiber laser without intracavity modulators, where a short and heavily Erbium-doped fiber is used as the gain medium in a ring cavity. By pulsed-pumping this short high gain cavity and tuning an intracavity variable optical coupler, the laser generates optical pulses with a pulse-width of μs at a repetition rate in the order of kHz down to one-shot operation. Furthermore, dynamic properties of this laser are investigated theoretically based on a traveling-wave-model, in which an adaptive-discrete-grid-finite-difference-method is applied. The simulation results validate the experimental results. The demonstrated pulsed laser is compact, flexible and cost-effective, which will have great potential for applications in all-optical sensing and communication systems.

  18. The Influence of Extreme Water Pulses on Greenhouse Gas Emissions from Soils

    Science.gov (United States)

    Petrakis, S.; Vargas, R.; Seyfferth, A.; Kan, J.; Inamdar, S. P.

    2015-12-01

    Anthropogenic activity increasing the amount of radiatively active gases, or Greenhouse Gases (GHGs) in the earth's atmosphere has led to shifts in weather patterns. Climate models predict the occurrence of large storms may increase in frequency and intensity in the mid-Atlantic region. Knowing that extreme precipitation events are rare, testing the influence of large water pulses across different soil types within an ecosystem is challenging. Large additions of water could promote or inhibit microbial activity, and change soil chemistry within a few days. Rapid changes in soil moisture lead to shifts in the behavior of soils as either sinks or sources of several GHGs (i.e., CO2, CH4 and N2O). Unfortunately, it is still unclear how rewetting events could impact the magnitude of GHG fluxes and how changing soil chemical parameters influence these responses. An experiment was designed to test the influence of extreme repeated water pulses on GHG fluxes from four different soils, representing key topographic locations within a watershed in the Piedmont region (i.e., forested upland, forested lowland, creek, wetland). Intact soil cores from these four soil types were kept under constant temperature (22oC) and we measured their responses to extreme water pulses. We continuously (hourly resolution) measured CO2, CH4 and N2O fluxes using a LI-8100A (Licor, Lincoln, NE) multiplexed system coupled to a Picarro G2508 (Picarro, Santa Clara, CA). Furthermore, we used a rhizolysimeter for porewater extraction to measure pH, redox, and water chemistry throughout the experiment. We hypothesized that repeated extreme water pulses would result in non-linear responses of GHG flux magnitudes and dynamics, and these dynamics would relate to changes in soil chemistry. We found that soil moisture alone could not explain the dynamics of GHG fluxes, but these extreme water pulses influenced the overall temporal patterns of all GHGs across all soil types. We also examined the 100 year

  19. 8th conference on Ultra-Wideband Short-Pulse Electromagnetics

    CERN Document Server

    Tyo, J. Scott; Baum, Carl E; Ultra-Wideband Short-Pulse Electromagnetics 8; UWBSP8

    2007-01-01

    The purpose of the Ultra-Wideband Short-Pulse Electromagnetics Conference series is to focus on advanced technologies for the generation, radiation and detection of ultra-wideband short pulse signals, taking into account their propagation and scattering from and coupling to targets of interest. This Conference series reports on developments in supporting mathematical and numerical methods and presents current and potential future applications of the technology. Ultra-Wideband Short-Pulse Electromagnetics 8 is based on the American Electromagnetics 2006 conference held from June 3-7 in Albuquerque, New Mexico. Topical areas covered in this volume include pulse radiation and measurement, scattering theory, target detection and identification, antennas, signal processing, and communications.

  20. Development of ultra-short high voltage pulse technology using magnetic pulse compression

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Byung Heon; Kim, S. G.; Nam, S. M.; Lee, B. C.; Lee, S. M.; Jeong, Y. U.; Cho, S. O.; Jin, J. T.; Choi, H. L

    1998-01-01

    The control circuit for high voltage switches, the saturable inductor for magnetic assist, and the magnetic pulse compression circuit were designed, constructed, and tested. The core materials of saturable inductors in magnetic pulse compression circuit were amorphous metal and ferrite and total compression stages were 3. By the test, in high repetition rate, high pulse compression were certified. As a result of this test, it became possible to increase life-time of thyratrons and to replace thyratrons by solid-state semiconductor switches. (author). 16 refs., 16 tabs.

  1. Repetition rate tunable ultra-short optical pulse generation based on electrical pattern generator

    Institute of Scientific and Technical Information of China (English)

    Xin Fu; Hongming Zhang; Meng Yan; Minyu Yao

    2009-01-01

    @@ An actively mode-locked laser with tunable repetition rate is proposed and experimentally demonstrated based on a programmable electrical pattern generator.By changing the repetition rate of the electrical patterns applied on the in-cavity modulator, the repetition rate of the output optical pulse sequences changes accordingly while the pulse width of the optical pulse train remains almost constant.In other words, the output ultra-short pulse train has a tunable duty cycle.In a proof-of-principle experiment, optical pulses with repetition rates of 10, 5, 2.5 and 1.25 GHz are obtained by adjusting the electrical pattern applied on the in-cavity modulator while their pulse widths remain almost unchanged.

  2. Bit rate and pulse width dependence of four-wave mixing of short optical pulses in semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Diez, S.; Mecozzi, A.; Mørk, Jesper

    1999-01-01

    We investigate the saturation properties of four-wave mixing of short optical pulses in a semiconductor optical amplifier. By varying the gain of the optical amplifier, we find a strong dependence of both conversion efficiency and signal-to-background ratio on pulse width and bit rate....... In particular, the signal-to-background ratio can be optimized for a specific amplifier gain. This behavior, which is coherently described in experiment and theory, is attributed to the dynamics of the amplified spontaneous emission, which is the main source of noise in a semiconductor optical amplifier....

  3. Short-pulse dynamics in strongly nonlinear dissipative granular chains.

    Science.gov (United States)

    Rosas, Alexandre; Romero, Aldo H; Nesterenko, Vitali F; Lindenberg, Katja

    2008-11-01

    We study the energy decay properties of a pulse propagating in a strongly nonlinear granular chain with damping proportional to the relative velocity of the grains. We observe a wave disturbance that at low viscosities consists of two parts exhibiting two entirely different time scales of dissipation. One part is an attenuating solitary wave, dominated by discreteness and nonlinearity effects as in a dissipationless chain, and has the shorter lifetime. The other is a purely dissipative shocklike structure with a much longer lifetime and exists only in the presence of dissipation. The range of viscosities and initial configurations that lead to this complex wave disturbance are explored.

  4. Electron dynamics from low-order harmonics generated by short laser pulses

    Science.gov (United States)

    Xiong, Wei-Hao; Gong, Qihuang; Peng, Liang-You

    2017-08-01

    Recently, low-order harmonics have gained much attention due to their applications as coherent light sources with a high repetition rate. In addition, the generation process is highly related to the bound electrons and can thus be applied to detect the dynamics of these electrons. In this work, we theoretically investigate the low-order harmonics below the first excited state, produced by a single-cycle optical pulse. We numerically solve the three-dimensional time-dependent Schrödinger equation (TDSE) to calculate the harmonic spectrum. With the help of a perturbation model, we can transparently understand the generation process of the spectrum. The results indicate that the harmonic spectrum can be sensitively influenced by the frequency component of the driving field. We find that the carrier envelope phase (CEP) dependence of low-order-harmonic generation originates from the interference of different harmonic orders. For these harmonics, the CEP effects can only be observed when the spectrum of the driving laser is extremely wide, which corresponds to the very short driving pulse. From the CEP-dependent interference structure, the phase relation of the third and the fifth harmonic can be extracted. The extracted information indicates that the atomic response induces a positive chirp for the emitted low-order harmonics. In addition, we investigated the harmonic phase calculated from the TDSE results. The harmonic phase is different from the phase predicted by the adiabatic model, and this phase difference can be related to the time delay of the electronic response. We extract the time delay from the harmonic phase and explore the CEP and intensity dependence of this time delay.

  5. Charge and spin dynamics driven by ultrashort extreme broadband pulses: A theory perspective

    Science.gov (United States)

    Moskalenko, Andrey S.; Zhu, Zhen-Gang; Berakdar, Jamal

    2017-02-01

    information on its spin-dependent dynamics. We review examples of such spectra of photons emitted from pulse-driven nanostructures as well as a possibility to characterize and control the light polarization on an ultrafast time scale. Furthermore, we consider the response of strongly correlated systems to short broadband pulses and show that this case bears a great potential to unveil high order correlations while they build up upon excitations.

  6. A short pulse, high rep-rate microdischarge VUV source

    Science.gov (United States)

    Stephens, Jacob; Fierro, Andrew; Dickens, James; Neuber, Andreas; CenterPulsed Power; Power Electronics Team

    2013-09-01

    A MOSFET based high voltage pulser is utilized to excite a microdischarge (MD), or microdischarge array (MDA) with pulsed voltages of up to 1 kV, with risetime and FWHM on the order of 10 ns and 30 ns, respectively. Additionally, the pulser is capable of pulsing at rep-rates in excess of 35 MHz. However, for these experiments the rep-rate was set on the order of 1 MHz, so as to limit excess energy deposition into the background gas and optimize the energy efficiency of VUV generation. Using VUV capable spectral diagnostics, the VUV emission of the MDs for various pressures (50-800 + Torr) and gases, focused on argon, argon-hydrogen mixtures, and neon-hydrogen mixtures (all of which provide strong emission at λ VUV emission is characterized and compared to results from transient fluid modeling of the MDA. For instance, the MDA turn-on time is recorded to be about 15 ns, which matches the full plasma development time in the model, and the MDA self- capacitance largely determines the turn-off behavior. This research was supported by an AFOSR grant on the Physics of Distributed Plasma Discharges and fellowships from the National Physical Sciences Consortium, supported by Sandia National Laboratories.

  7. Clinical case and short review of extreme short bowel syndrome: an update 21 years after

    Directory of Open Access Journals (Sweden)

    Pasquale Mansueto

    2016-03-01

    Full Text Available Short bowel syndrome refers to the malabsorptive state caused by loss of significant portions of the small intestine, whose clinical framework is characterized by malnutrition, diarrhea, dehydration, weight loss, and low-weight-related symptoms/signs. These clinical conditions seem to be related to the length of resection. Twenty-one years ago we reported the clinical case of an infant, who underwent a massive resection of the loops of the small intestine, of the cecum and of part of the ascending colon, due to intestinal malrotation with volvulus. The residual small intestine measured just 11 cm and consisted of the duodenum and a small part of jejunum, in the absence of the ileocecal valve, configuring the case of a ultra-short bowel syndrome. In this report, we update the case, reporting the patient succeeded to obtain a good weight gain and to conduct a quite normal lifestyle, despite the long-term consequences of such resection.

  8. All-solid-state repetitive semiconductor opening switch-based short pulse generator.

    Science.gov (United States)

    Ding, Zhenjie; Hao, Qingsong; Hu, Long; Su, Jiancang; Liu, Guozhi

    2009-09-01

    The operating characteristics of a semiconductor opening switch (SOS) are determined by its pumping circuit parameters. SOS is still able to cut off the current when pumping current duration falls to the order of tens of nanoseconds and a short pulse forms simultaneously in the output load. An all-solid-state repetitive SOS-based short pulse generator (SPG100) with a three-level magnetic pulse compression unit was successfully constructed. The generator adopts magnetic pulse compression unit with metallic glass and ferrite cores, which compresses a 600 V, 10 mus primary pulse into short pulse with forward pumping current of 825 A, 60 ns and reverse pumping current of 1.3 kA, 30 ns. The current is sent to SOS in which the reverse pumping current is interrupted. The generator is capable of providing a pulse with the voltage of 120 kV and duration of 5-6 ns while output load being 125 Omega. The highest repetition rate is up to 1 kHz.

  9. Optical and electrical properties of SnO2 thin films after ultra-short pulsed laser annealing

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Römer, G.R.B.E.; Bor, T.C.; Ogieglo, W.; Klein Gunnewiek, M.; Lenferink, A.; Otto, C.; Skolski, J.Z.P.; Grob, F.; Lange, de D.F.; Huis in 't Veld, A.J.; Reutzel, Edward W.

    2013-01-01

    Ultra-short pulsed laser sources, with pulse durations in the ps and fs regime, are commonly exploited for cold ablation. However, operating ultra-short pulsed laser sources at fluence levels well below the ablation threshold allows for fast and selective thermal processing. The latter is especially

  10. Optical and electrical properties of SnO2 thin films after ultra-short pulsed laser annealing

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Römer, G.R.B.E.; Bor, T.; Ogieglo, W.; Klein Gunnewiek, M.; Lenferink, A.; Otto, C.; Skolski, J.Z.P.; Grob, F.; de Lange, D.F.; Huis in 't Veld, A.J.; Reutzel, Edward W.

    2013-01-01

    Ultra-short pulsed laser sources, with pulse durations in the ps and fs regime, are commonly exploited for cold ablation. However, operating ultra-short pulsed laser sources at fluence levels well below the ablation threshold allows for fast and selective thermal processing. The latter is especially

  11. Prompt pre-thermal laser ion sheath acceleration with ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zeil, Karl; Bussmann, Michael; Cowan, Thomas; Kluge, Thomas; Kraft, Stephan; Metzkes, Josefine; Schramm, Ulrich [Helmholtz-Zentrum Dresden-Rossendorf (Germany)

    2013-07-01

    Recent laser-ion acceleration experiments performed at the 150 TW Draco laser in Dresden, Germany, have demonstrated the importance of a precise understanding of the electron dynamics in solids on an ultra-short time scale. For example, with ultra-short laser pulses a description based purely on the evolution of a thermal electron ensemble, as in standard TNSA models, is not sufficient anymore. Rather, non-thermal effects during the ultra-short intra-pulse phase of laser-electron interaction in solids become important for the acceleration of ions when the laser pulse duration is in the order of only a few tens of femtoseconds. While the established maximum ion energy scaling in the TNSA regime goes with the square root of the laser intensity, for such ultra short pulse durations the maximum ion energy is found to scale linear with laser intensity, motivating the interest in such laser systems. Investigating the influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution, we present recent advances in the description of the laser interaction with solids, focusing on the implications of intra-pulse non-thermal phenomena on the ion acceleration.

  12. Novel oral applications of ultra-short laser pulses

    Science.gov (United States)

    Wieger, V.; Wernisch, J.; Wintner, E.

    2007-02-01

    In the past decades, many efforts have been made to replace mechanical tools in oral applications by various laser systems. The reasons therefore are manifold: i) Friction causes high temperatures damaging adjacent tissue. ii) Smear layers and rough surfaces are produced. iii) Size and shape of traditional tools are often unsuitable for geometrically complicated incisions and for minimum invasive treatment. iv) Mechanical damage of the remaining tissue occurs. v) Online diagnosis for feedback is not available. Different laser systems in the µs and sub-&mrgs-pulse regime, among them Erbium lasers, have been tested in the hope to overcome the mentioned drawbacks and, to some extent, they represent the current state of the art with respect to commercial and hence practical application. In the present work the applicability of scanned ultrashort pulse lasers (USPLs) for biological hard tissue as well as dental restoration material removal was tested. It is shown that cavities with features superior to mechanically treated or Erbium laser ablated cavities can be generated if appropriate scan algorithms and optimum laser parameters are matched. Smooth cavity rims, no microcracks, melting or carbonisation and precise geometry are the advantages of scanned USLP ablation. For bone treatment better healing conditions are expected as the natural structure remains unaffected by the preparation procedure. The novelty of this work is represented by a comprehensive compilation of various experimental results intended to assess the performance of USPLs. In this context, various pulse durations in the picosecond and femtosecond regime were applied to dental and bone tissue as well as dental restoration materials which is considered to be indispensable for a complete assessment. Parameters like ablation rates describing the efficiency of the ablation process, and ablation thresholds were determined - some of them for the first time - and compared to the corresponding Erbium

  13. Development of a 1 J short pulse tunable TEA CO2 laser with high energy stability

    Science.gov (United States)

    Kumar, Manoj; Reghu, T.; Biswas, A. K.; Bhargav, Pankaj; Pakhare, J. S.; Kumar, Shailesh; Verma, Abrat; Mandloi, Vagesh; Kukreja, L. M.

    2014-12-01

    The design, development and operational characteristics of a 1 J, repetitively pulsed, line tunable TEA CO2 laser producing nearly tail free short pulses (~170 ns) suitable for laser isotope separation is discussed. Tail free short laser pulses were generated by employing a nitrogen lean gaseous active medium. Use of an indigenously developed stable pulsed power supply, uniform and intense UV spark pre-ionization and optimum gas purging with catalytic regeneration to control the deleterious oxygen accumulation helps generate laser pulses with high energy stability. Integration of a sensitive arc detection system allows long term arc-free operation of the laser and protects it from catastrophic failure. Laser pulses in more than 90 lines in 10.6 μm and 9.6 μm bands of CO2 laser spectrum with energy about 1 J in as many as 50 lines could be generated with a typical efficiency of about 4%. A typical pulse to pulse energy stability of ±1.4% was obtained during one hour of continuous operation of the TEA CO2 laser at 75 Hz.

  14. RAPID COMMUNICATION: Enhanced performance of a dielectric barrier discharge lamp using short-pulsed excitation

    Science.gov (United States)

    Mildren, R. P.; Carman, R. J.

    2001-01-01

    We observe marked increases in the time-averaged intensity, peak intensity, efficiency and spectral purity of the VUV output from an Xe excimer barrier discharge lamp when using short-pulse (~150 ns FWHM (full width half maximum)) excitation. Intensity increases with Xe pressure up to 600 Torr with a maximum output 2.6 times higher and an efficiency 3.2 times higher than the same lamp excited by conventional ac excitation (i.e. sinusoidal voltage waveform). The output occurs in regular short pulses (pulsed discharge appears diffuse (i.e. glow-like), even at the higher pressures at which the ac discharge is filamentary. It is concluded that the enhanced performance results largely from the ability for pulsed excitation to generate a discharge at near atmospheric pressures with a much lower electron density than that possible using ac.

  15. Radiative transfer in participating media with collimated short-pulse Gaussian irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Okutucu, Tuba; Yener, Yaman [Mechanical and Industrial Engineering Department, Northeastern University, Boston, MA 02115 (United States)

    2006-05-07

    Radiative transfer in a one-dimensional absorbing and isotropically scattering plane-parallel grey medium with a collimated short-pulse Gaussian irradiation on one of its boundaries is studied. The medium is non-emitting and the boundaries are non-reflecting and non-refracting. The Galerkin method is extended for the solution of the transient radiative transfer problem. The transient transmittance and reflectance of the medium are evaluated for various optical thicknesses, scattering albedos and pulse durations.

  16. Dissociative multiple ionization of diatomic molecules by extreme-ultraviolet free-electron-laser pulses

    DEFF Research Database (Denmark)

    Madsen, Lars Bojer; Leth, Henriette Astrup

    2011-01-01

    Nuclear dynamics in dissociative multiple ionization processes of diatomic molecules exposed to extreme-ultraviolet free-electron-laser pulses is studied theoretically using the Monte Carlo wave packet approach. By simulated detection of the emitted electrons, the model reduces a full propagation...... of the system to propagations of the nuclear wave packet in one specific electronic charge state at a time. Suggested ionization channels can be examined, and kinetic energy release spectra for the nuclei can be calculated and compared with experiments. Double ionization of O2 is studied as an example, and good...

  17. Influence of the pulse duration and the experimental approach onto the specific removal rate for ultra-short pulses

    Science.gov (United States)

    Jaeggi, B.; Neuenschwander, B.; Remund, S.; Kramer, T.

    2017-02-01

    To be competitive in industrial applications the throughput is a key factor in laser micro machining using ultra-short pulsed laser systems. Both, ps and fs laser systems are suitable for industrial applications. Therefore one has to choose the right pulse duration for highest ablation efficiency. As shown in earlier publications the efficiency of the ablation process can be described by the specific removal rate, which has a maximum value at an optimum fluence. But its value often bases on a calculation using the threshold fluence and energy penetration depth deduced by measuring the depth of ablated cavities machined with different fluences and number of pulses. But this calculated specific removal rate often differs from the one deduced from ablated squares as recently shown in literature. Further an unexpected drop of the specific removal rate was reported for stainless steel when the pulse duration was reduced from 900 fs to 400 fs. Thus the influence of the pulse duration in the fs and low ps regime onto the specific removal rate is investigated with different methods for industrial relevant materials

  18. Complex {PT}-symmetric extensions of the nonlinear ultra-short light pulse model

    Science.gov (United States)

    Yan, Zhenya

    2012-11-01

    The short pulse equation u_{xt}=u+\\frac{1}{2}(u^2u_x)_x is PT symmetric, which arises in nonlinear optics for the ultra-short pulse case. We present a family of new complex PT-symmetric extensions of the short pulse equation, i[(iu_x)^{\\sigma }]_t=au+bu^m+ic[u^n(iu_x)^{\\epsilon }]_x \\,\\, (\\sigma ,\\, \\epsilon ,\\,a,\\,b,\\,c,\\,m,\\,n \\in {R}), based on the complex PT-symmetric extension principle. Some properties of these equations with some chosen parameters are studied including the Hamiltonian structures and exact solutions such as solitary wave solutions, doubly periodic wave solutions and compacton solutions. Our results may be useful to understand complex PT-symmetric nonlinear physical models. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’.

  19. Forward voltage short-pulse technique for measuring high power laser array junction temperature

    Science.gov (United States)

    Meadows, Byron L. (Inventor); Amzajerdian, Frazin (Inventor); Barnes, Bruce W. (Inventor); Baker, Nathaniel R. (Inventor)

    2012-01-01

    The present invention relates to a method of measuring the temperature of the P-N junction within the light-emitting region of a quasi-continuous-wave or pulsed semiconductor laser diode device. A series of relatively short and low current monitor pulses are applied to the laser diode in the period between the main drive current pulses necessary to cause the semiconductor to lase. At the sufficiently low current level of the monitor pulses, the laser diode device does not lase and behaves similar to an electronic diode. The voltage across the laser diode resulting from each of these low current monitor pulses is measured with a high degree of precision. The junction temperature is then determined from the measured junction voltage using their known linear relationship.

  20. Modulation of ionization on laser frequency in ultra-short pulse intense laser-gas-target

    Institute of Scientific and Technical Information of China (English)

    Hu Qiang-Lin; Liu Shi-Bing

    2006-01-01

    Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target.The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

  1. Evolution of electron beam pulses of short duration in the solar corona

    Science.gov (United States)

    Casillas-Pérez, G. A.; Jeyakumar, S.; Pérez-Enríquez, H. R.; Trinidad, M. A.

    2016-11-01

    Narrowband radio bursts with durations of the order of milliseconds, called spikes, are known to be associated with solar flares. In order to understand the particle beams responsible for the radio spike phenomena, evolution of electron beam pulses injected from a solar flare region into the corona is studied. Numerical integration of the Fokker-Planck (FP) equation is used to follow the evolution of the electron beam pulse. The simulations show that the short duration pulses lose most of their energy within a second of propagation into the corona. Electron beam with a small low energy cut off is thermalized faster than that with a high low energy cut off.

  2. Short pulse absorption dynamics in a p-i-n InGaAsP MQW waveguide saturable absorber

    DEFF Research Database (Denmark)

    Romstad, Francis Pascal; Öhman, Filip; Mørk, Jesper

    2002-01-01

    The saturation properties and absorption dynamics of an InGaAsP MQW waveguide saturable absorber is measured using short 200-fs and 1-ps pulses. The dependence on the pulse energy and reverse bias is characterized.......The saturation properties and absorption dynamics of an InGaAsP MQW waveguide saturable absorber is measured using short 200-fs and 1-ps pulses. The dependence on the pulse energy and reverse bias is characterized....

  3. Short optical pulse generated by integrated MQW DBR laser/EA-modulator

    Science.gov (United States)

    Chen, Young-Kai; Tanbun-Ek, Tawee; Logan, Ralph A.; Tate, A. R.; Sergent, A. M.; Wecht, K. W.; Sciortino, Paul F., Jr.; Raybon, Gregory; Froberg, Nan M.; Johnson, Anthony M.

    1994-05-01

    We report on the generation of short optical pulses by utilizing the non-linear absorption characteristics of a multiple quantum well (MQW) electro-absorption modulator, which is monolithically integrated with a MQW wavelength-tunable distributed Bragg reflector (DBR) laser on a single chip. Optical pulses as short as 39 ps and 15 ps have been generated at a repetition rate of 3 GHz and 10 GHz, respectively, with a broad tuning range of 5.4 nm near 1554 nm lasing wavelength.

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

    Energy Technology Data Exchange (ETDEWEB)

    Early, J; Bibeau, C; Claude, P

    2003-09-16

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

  5. Parallel simulation for the ultra-short laser pulses' propagation in air

    CERN Document Server

    Ma, Cunliang

    2015-01-01

    A parallel 2D+1 split-step Fourier method with Crank-Nicholson scheme running on multi-core shared memory architectures is developed to study the propagation of ultra-short high-intensity laser pulses in air. The parallel method achieves a near linear speed-up with results for the efficiency of more than 95% on a 24-core machine. This method is of great potential application in studying the long-distance propagation of the ultra-short high intensity laser pulses.

  6. Near infrared and extreme ultraviolet light pulses induced modifications of ultrathin Co films

    Directory of Open Access Journals (Sweden)

    Jan Kisielewski

    2017-05-01

    Full Text Available We report on comparative study of magnetic properties of Pt/Co/Pt trilayers after irradiation with different light sources. Ultrathin Pt/Co/Pt films were deposited by molecular beam epitaxy technique on sapphire (0001 substrates. Pt buffers were grown at room temperature (RT and at 750°C (high temperature, HT. The samples were irradiated with a broad range of light energy densities (up to film ablation using two different single pulse irradiation sources: (i 40 fs laser with 800 nm wavelength and (ii 3 ns laser-plasma source of extreme ultraviolet (EUV with the most intense emission centered at 11 nm. The light pulse-driven irreversible structural and as a consequence, magnetic modifications were investigated using polar magneto-optical Kerr effect-based microscopy and atomic and magnetic force microscopies. The light pulse-induced transitions from the out-of-plane to in-plane magnetization state, and from in-plane to out-of-plane, were observed for both types of samples and irradiation methods. Diagrams of the magnetic states as a function of the Co layer thickness and energy density of the absorbed femtosecond pulses were constructed for the samples with both the RT and HT buffers. The energy density range responsible for the creation of the out-of-plane magnetization was wider for the HT than for RT buffer. This is correlated with the higher (for HT crystalline quality and much smoother Pt/Co surface deduced from the X-ray diffraction studies. Submicrometer magnetic domains were observed in the irradiated region while approaching the out-of-plane magnetization state. Changes of Pt/Co/Pt structures are discussed for both types of light pulses.

  7. A broadly tunable autocorrelator for ultra-short, ultra-high power infrared optical pulses

    Energy Technology Data Exchange (ETDEWEB)

    Szarmes, E.B.; Madey, J.M.J. [Duke Univ., Durham, NC (United States)

    1995-12-31

    We describe the design of a crossed-beam, optical autocorrelator that uses an uncoated, birefringent beamsplitter to split a linearly polarized incident pulse into two orthogonally polarized pulses, and a Type II, SHG crystal to generate the intensity autocorrelation function. The uncoated beamsplitter accommodates extremely broad tunability while precluding any temporal distortion of ultrashort optical pulses at the dielectric interface, and the specific design provides efficient operation between 1 {mu}m and 4 {mu}m. Furthermore, the use of Type II SHG completely eliminates any single-beam doubling, so the autocorrelator can be operated at very shallow crossed-beam angles without generating a background pedestal. The autocorrelator has been constructed and installed in the Mark III laboratory at Duke University as a broadband diagnostic for ongoing compression experiments on the chirped-pulse FEL.

  8. Conditional Second Order Short-crested Water Waves Applied to Extreme Wave Episodes

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher

    2005-01-01

    A derivation of the mean second order short-crested wave pattern and associated wave kinematics, conditional on a given magnitude of the wave crest, is presented. The analysis is based on the second order Sharma and Dean finite water wave theory. A comparison with a measured extreme wave profile......, the Draupner New Year Wave, shows a good agreement in the mean, indicating that this second order wave can be a good identifier of the shape and occurrence of extreme wave events. A discussion on its use as an initial condition for a fully non-linear three-dimensional surface wave analysis is given....

  9. Short-pulse, compressed ion beams at the Neutralized Drift Compression Experiment

    Science.gov (United States)

    Seidl, P. A.; Barnard, J. J.; Davidson, R. C.; Friedman, A.; Gilson, E. P.; Grote, D.; Ji, Q.; Kaganovich, I. D.; Persaud, A.; Waldron, W. L.; Schenkel, T.

    2016-05-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target.

  10. Extremely Nonlinear Optics Using Shaped Pulses Spectrally Broadened in an Argon- or Sulfur Hexafluoride-Filled Hollow-Core Fiber

    Directory of Open Access Journals (Sweden)

    Andreas Hoffmann

    2015-11-01

    Full Text Available In this contribution we present a comparison of the performance of spectrally broadened ultrashort pulses using a hollow-core fiber either filled with argon or sulfur hexafluoride (SF6 for demanding pulse-shaping experiments. The benefits of both gases for pulse-shaping are studied in the highly nonlinear process of high-harmonic generation. In this setup, temporally shaping the driving laser pulse leads to spectrally shaping of the output extreme ultraviolet (XUV spectrum, where total yield and spectral selectivity in the XUV are the targets of the optimization approach. The effect of using sulfur hexafluoride for pulse-shaping the XUV yield can be doubled compared to pulse compression and pulse-shaping using argon and the spectral range for selective optimization of a single harmonic can be extended. The obtained results are of interest for extending the range of ultrafast science applications drawing on tailored XUV fields.

  11. Experimental and theoretical characterisation of short pulse X ray lasers

    CERN Document Server

    Strati, F

    2002-01-01

    Since the demonstration in 1984 of x-ray laser action in Ne-like Se at 20.6 and 20.9 nm, much experimental and theoretical effort has been ongoing to investigate different lasing schemes. Aims in this research include improving pumping efficiency, beam quality and overall energy output of the demonstrated x-ray lasers and the production of lasing at shorter wavelengths. The envisaged and demonstrated applications of x-ray lasers utilise their short wavelength, high brightness and coherence. Examples of potential applications include x-ray imaging and holography of biological materials in the water window region (2.3 - 4.4 nm), x-ray photolithography for the fabrication of microcircuits and structures below the micron scale and x-ray interferometry, deflectometry and radiography of dense plasma environments of interest in inertial confinement fusion and astrophysics. Soft x-ray laser action has been demonstrated in various plasma active media with wavelengths ranging from 3.5 nm to 40.0 nm and above. However, ...

  12. High-pressure dielectric barrier discharge Xenon lamps generating short pulses of high-peak-power VUV radiation (172nm) with high pulse-to-pulse reproducibility.

    Science.gov (United States)

    Carman, Robert; Ward, Barry; Mildren, Richard; Kane, Deborah

    2003-10-01

    Dielectric barrier discharges (DBDs) are used to efficiently generate radiation in the ultraviolet and vacuum-ultraviolet spectral regions (88nm-350nm) by forming rare-gas and rare-gas halide excimers in a transient plasma. Usually, DBD lamps generate the light output quasi-continuously or in bursts with a high degree of stochastic or random variability in the instantaneous UV/VUV intensity. However, regular pulses of high-peak-power UV/VUV, with high pulse-to-pulse reproducibility, are of interest for applications in biology, surface treatment and cleaning, and time-resolved fluorescence spectroscopy. Such pulses can be generated from spatially homogeneous plasmas in a Xe DBD when the discharge is driven by uni-polar voltage pulses of short duration ( 100ns)^1. In the present study, we will report Xe DBD lamp performance and VUV output pulse characteristics for gas pressures up to 2.5bar and excitation conditions tailored for high-peak-power output. The experimental results will be compared to theoretical results from a detailed 1-D computer model of the spatio-temporal evolution of the plasma kinetics and Xe species population densities. ^1R.P.Mildren and R.J.Carman, J.Phys.D, 34, L1-L6, (2001)

  13. Experimental studies on extremely low frequency pulsed magnetic field inhibiting sarcoma and enhancing cellular immune functions

    Institute of Scientific and Technical Information of China (English)

    张沪生; 叶晖; 张传清; 曾繁清; 黄兴鼎; 张晴川; 李宗山; 杜碧

    1997-01-01

    The previous observation with an electron microscope showed that extremely low frequency (ELF) pulsed magnetic field (PMF) (with the maximum intensity of 0. 6-2. 0 T, gradient of 10-100 T. M-1, pulse width of 20-200 ms and frequency of 0. 16-1. 34 Hz) inhibited the growth of S-180 sarcoma in mice and enhanced the ability of immune cell’s dissolving sarcoma cells. In this study, the DNA contents of nuclei were assayed by using Faulgen Staining method. With an electron microscope and cell stereoscopy technology it was observed that magnetic field affected the sarcoma cell’s metabolism, lowered its malignancy, and restrained its rapid and heteromorphic growth. The magnetic field enhanced the cellular immune ability and the reaction of lymphocytes and plasma. Since ELF pulsed magnetic fields can inhibit the growth of sarcomas and enhance the cellular immune ability, it is possible to use it as a new method to treat cancer.

  14. Towards pump-probe experiments of defect dynamics with short ion beam pulses

    Science.gov (United States)

    Schenkel, T.; Lidia, S. M.; Weis, C. D.; Waldron, W. L.; Schwartz, J.; Minor, A. M.; Hosemann, P.; Kwan, J. W.

    2013-11-01

    A novel, induction type linear accelerator, the Neutralized Drift Compression eXperiment (NDCX-II), is currently being commissioned at Berkeley Lab. This accelerator is designed to deliver intense (up to 3 × 1011 ions/pulse), 0.6 to ∼600 ns duration pulses of 0.05-1.2 MeV lithium ions at a rate of about 2 pulses per minute onto 1-10 mm scale target areas. When focused to mm-diameter spots, the beam is predicted to volumetrically heat micrometer thick foils to temperatures of ∼30,000 °K. At lower beam power densities, the short excitation pulse with tunable intensity and time profile enables pump-probe type studies of defect dynamics in a broad range of materials. We briefly describe the accelerator concept and design, present results from beam pulse shaping experiments and discuss examples of pump-probe type studies of defect dynamics following irradiation of materials with intense, short ion beam pulses from NDCX-II.

  15. Towards pump probe experiments of defect dynamics with short ion beam pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schenkel, T. [Lawrence Berkeley National Laboratory (LBNL); Lidia, S. [Lawrence Berkeley National Laboratory (LBNL); Weis, C. D. [Lawrence Berkeley National Laboratory (LBNL); Waldron, W. L. [Lawrence Berkeley National Laboratory (LBNL); Schwartz, J. [Lawrence Berkeley National Laboratory (LBNL); Minor, Andrew [Lawrence Berkeley National Laboratory (LBNL); Hosemann, P [University of California, Berkeley; Kwan, J. W. [Lawrence Berkeley National Laboratory (LBNL)

    2013-01-01

    A novel, induction type linear accelerator, the Neutralized Drift Compression eXperiment (NDCX-II), is currently being commissioned at Berkeley Lab. This accelerator is designed to deliver intense (up to 3 1011 ions/pulse), 0.6 to 600 ns duration pulses of 0.05 1.2 MeV lithium ions at a rate of about 2 pulses per minute onto 1 10 mm scale target areas. When focused to mm-diameter spots, the beam is predicted to volumetrically heat micrometer thick foils to temperatures of 30,000 K. At lower beam power densities, the short excitation pulse with tunable intensity and time profile enables pump probe type studies of defect dynamics in a broad range of materials. We briefly describe the accelerator concept and design, present results from beam pulse shaping experiments and discuss examples of pump probe type studies of defect dynamics following irradiation of materials with intense, short ion beam pulses from NDCX-II.

  16. Towards pump–probe experiments of defect dynamics with short ion beam pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schenkel, T., E-mail: t_schenkel@lbl.gov [Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, 5R121, Berkeley, CA 94720 (United States); Lidia, S.M.; Weis, C.D.; Waldron, W.L.; Schwartz, J. [Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, 5R121, Berkeley, CA 94720 (United States); Minor, A.M. [Materials Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States); Hosemann, P. [Materials Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Nuclear Engineering Department, University of California, Berkeley, CA 94720 (United States); Kwan, J.W. [Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, 5R121, Berkeley, CA 94720 (United States)

    2013-11-15

    A novel, induction type linear accelerator, the Neutralized Drift Compression eXperiment (NDCX-II), is currently being commissioned at Berkeley Lab. This accelerator is designed to deliver intense (up to 3 × 10{sup 11} ions/pulse), 0.6 to ∼600 ns duration pulses of 0.05–1.2 MeV lithium ions at a rate of about 2 pulses per minute onto 1–10 mm scale target areas. When focused to mm-diameter spots, the beam is predicted to volumetrically heat micrometer thick foils to temperatures of ∼30,000 °K. At lower beam power densities, the short excitation pulse with tunable intensity and time profile enables pump–probe type studies of defect dynamics in a broad range of materials. We briefly describe the accelerator concept and design, present results from beam pulse shaping experiments and discuss examples of pump–probe type studies of defect dynamics following irradiation of materials with intense, short ion beam pulses from NDCX-II.

  17. SOLID BODY ABLATION UNDER EXPOSURE TO ULTRA SHORT LASER PULSES: STUDY BY MOLECULAR DYNAMICS METHODS

    Directory of Open Access Journals (Sweden)

    D. S. Ivanov

    2014-09-01

    Full Text Available The process of laser ablation under the influence of ultra short laser pulses on metals is investigated by methods of molecular dynamics. The validity and applicability of the hybrid atomistic-continuous model for the estimation of optimum modes of ultra short laser pulses processing are explored. Combination of atomistic model of laser-induced non-equilibrium process of a phase transition at the atomic level with continuous two-temperature model for describing the dynamics of photo-excitation of free media is proposed. Applicability of laser ablation model on the example of aluminum films and gold under exposure to pulses with different energy density and duration is shown. It is indicated that, depending on the ratio of the laser pulse duration and the characteristic time of electron-phonon material interaction, photothermal and photomechanical modes of destruction are implemented that determine the quality and performance of the laser processing. It is established that at the duration of laser pulse less than the time of electron-phonon interaction high-performance photomechanical type of destruction is implemented by internal stresses arising in the area of exposure. This is confirmed by a linear dependence of the ablation rate from the absorbed energy. At the duration of laser pulse greater than the time of electron-phonon interaction inefficient photothermal mode of destruction is implemented. The results may be useful for specialists engaged in the development of laser technologies

  18. Incremental growth of short SWNT arrays by pulsed chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Puretzky, Alexander A [ORNL; Geohegan, David B [ORNL; Jackson, Jeremy [Sentech, Inc.; Pannala, Sreekanth [ORNL; Eres, Gyula [ORNL; Rouleau, Christopher M [ORNL; More, Karren Leslie [ORNL; Thonnard, Norbert [ORNL; Readle, Jason D [ORNL

    2012-01-01

    Very short, aligned arrays of continuous single wall carbon nanotubes were grown incrementally in steps as small as 25 nm using pulsed chemical vapor deposition. In situ optical extinction measurements indicate that over 98% of the nanotubes reinitiate growth on successive gas pulses, and HRTEM images show that the SWNTs do not exhibit segments, caps, or noticeable sidewall defects resulting from repeatedly stopping and restarting growth. Time-resolved laser reflectivity (3-ms temporal resolution) was used to record the nucleation and growth kinetics for each fast (0.2 second) gas pulse and measure the height increase of the array in situ, providing a "digital" method to incrementally grow short nanotube arrays to precise heights. Derivatives of the optical reflectivity signal reveal distinct temporal signatures for both nucleation and growth kinetics, with their amplitude ratio on the first gas pulse serving as a good predictor for aligned vs. unaligned growth. Incremental growth by pulsed CVD is interpreted in the context of autocatalytic kinetic models as a special processing window in which a sufficiently high flux of feedstock gas drives the nucleation and rapid growth phases of a catalyst nanoparticle ensemble to occur within the temporal period of the gas pulse, but without inducing growth termination.

  19. Incremental growth of short SWNT arrays by pulsed chemical vapor deposition.

    Science.gov (United States)

    Puretzky, Alexander A; Geohegan, David B; Jackson, Jeremy J; Pannala, Sreekanth; Eres, Gyula; Rouleau, Christopher M; More, Karren L; Thonnard, Norbert; Readle, Jason D

    2012-05-21

    Very short arrays of continuous single-wall carbon nanotubes (SWNTs) are grown incrementally in steps as small as 25 nm using pulsed chemical vapor deposition (CVD). In-situ optical extinction measurements indicate that over 98% of the nanotubes reinitiate growth on successive gas pulses, and high-resolution transmission electron microscopy (HR-TEM) images show that the SWNTs do not exhibit segments, caps, or noticeable sidewall defects resulting from repeatedly stopping and restarting growth. Time-resolved laser reflectivity (3-ms temporal resolution) is used to record the nucleation and growth kinetics for each fast (0.2 s) gas pulse and to measure the height increase of the array in situ, providing a method to incrementally grow short nanotube arrays to precise heights. Derivatives of the optical reflectivity signal reveal distinct temporal signatures for both nucleation and growth kinetics, with their amplitude ratio on the first gas pulse serving as a good predictor for the evolution of the growth of the nanotube ensemble into a coordinated array. Incremental growth by pulsed CVD is interpreted in the context of autocatalytic kinetic models as a special processing window in which a sufficiently high flux of feedstock gas drives the nucleation and rapid growth phases of a catalyst nanoparticle ensemble to occur within the temporal period of the gas pulse, but without inducing growth termination.

  20. Annealing of SnO2 thin films by ultra-short laser pulses

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Bor, Teunis Cornelis; Eijt, S.W.H.; Schut, H.; Römer, Gerardus Richardus, Bernardus, Engelina; de Lange, D.F.; Huis in 't Veld, Bert

    2014-01-01

    Post-deposition annealing by ultra-short laser pulses can modify the optical properties of SnO2 thin films by means of thermal processing. Industrial grade SnO2 films exhibited improved optical properties after picosecond laser irradiation, at the expense of a slightly increased sheet resistance

  1. Erosion resistant anti-ice surfaces generated by ultra short laser pulses

    NARCIS (Netherlands)

    Del Cerro, D.A.; Römer, G.R.B.E.; Huis in't Veld, A.J.

    2010-01-01

    Wetting properties of a wide range of materials can be modified by accurate laser micromachining with ultra short laser pulses. Controlling the surface topography in a micro and sub-micrometer scale allows the generation of water-repellent surfaces, which remain dry and prevent ice accumulation

  2. Short Pulse High Brightness X-ray Production with the PLEIADES Thomson Scattering Source

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, S G; Barty, C P J; Betts, S M; Brown, W J; Crane, J K; Cross, R R; Fittinghoff, D N; Gibson, D J; Hartemann, F V; Kuba, J; LaSage, G P; Rosenzweig, J B; Slaughter, D R; Springer, P T; Tremaine, A M

    2003-07-01

    We describe PLEIADES, a compact, tunable, high-brightness, ultra-short pulse, Thomson x-ray source. The peak brightness of the source is expected to exceed 10{sup 20} photons/s/0.1% bandwidth/mm{sup 2}/mrad{sup 2}. Initial results are reported and compared to theoretical calculations.

  3. Thermal processing of thin films using ultra-short laser pulses: applied to photovoltaic materials

    NARCIS (Netherlands)

    Scorticati, D.

    2015-01-01

    In this thesis a novel approach to raise the thermal selectivity of superficial heat treatments, exploiting ultra-short laser pulses, is proposed and studied. That is, the effective applicability of ultrafast lasers for selective heat treatments is proven by increasing the performance of different

  4. Ultra short pulse laser generated surface textures for anti-ice applications in aviation

    NARCIS (Netherlands)

    Römer, G.W.; Del Cerro, D.A.; Sipkema, R.C.J.; Groenendijk, M.N.W.; Huis in 't Veld, A.J.

    2009-01-01

    By laser ablation with ultra short laser pulses in the pico- and femto-second range, well controlled dual scaled micro- and nano-scaled surface textures can be obtained. The micro-scale of the texture is mainly determined by the dimensions of the laser spot, whereas the superimposed nano-structure

  5. Ultra-Short Optical Pulse Generation with Single-Layer Graphene

    CERN Document Server

    Lee, C -C; Bunch, J S; Schibli, T R

    2010-01-01

    Pulses as short as 260 fs have been generated in a diode-pumped low-gain Er:Yb:glass laser by exploiting the nonlinear optical response of single-layer graphene. The application of this novel material to solid-state bulk lasers opens up a way to compact and robust lasers with ultrahigh repetition rates.

  6. Erosion resistant anti-ice surfaces generated by ultra short laser pulses

    NARCIS (Netherlands)

    Del Cerro, D.A.; Römer, G.R.B.E.; Huis in't Veld, A.J.

    2010-01-01

    Wetting properties of a wide range of materials can be modified by accurate laser micromachining with ultra short laser pulses. Controlling the surface topography in a micro and sub-micrometer scale allows the generation of water-repellent surfaces, which remain dry and prevent ice accumulation unde

  7. Low index-contrast photonic bandgap fiber for transmission of short pulsed light

    DEFF Research Database (Denmark)

    Riishede, Jesper; Lægsgaard, Jesper; Broeng, Jes

    2004-01-01

    The use of low-index-contrast photonic bandgap (PBG) fiber for transmission of short pulsed light is discussed. PBG fibers have positive waveguide dispersion at long wavelengths at which conventional index-guiding fibers have negative waveguide dispersion. PBG fibers with low-index contrast can...

  8. Annealing of SnO2 thin films by ultra-short laser pulses

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Bor, T.; Eijt, S.W.H.; Schut, H.; Römer, G.R.B.E.; Lange, D.F. de; Huis In't Veld, A.J.

    2014-01-01

    Post-deposition annealing by ultra-short laser pulses can modify the optical properties of SnO2 thin films by means of thermal processing. Industrial grade SnO2 films exhibited improved optical properties after picosecond laser irradiation, at the expense of a slightly increased sheet resistance [Pr

  9. Ultra short pulse laser generated surface textures for anti-ice applications in aviation

    NARCIS (Netherlands)

    Römer, G.W.; Del Cerro, D.A.; Sipkema, R.C.J.; Groenendijk, M.N.W.; Huis in 't Veld, A.J.

    2009-01-01

    By laser ablation with ultra short laser pulses in the pico- and femto-second range, well controlled dual scaled micro- and nano-scaled surface textures can be obtained. The micro-scale of the texture is mainly determined by the dimensions of the laser spot, whereas the superimposed nano-structure i

  10. Feasibility study on a short-pulsed IR wavelength for effective calculus fragmentation

    Science.gov (United States)

    Kang, Hyun Wook

    2015-05-01

    Laser-induced lithotripsy has been used for a minimally-invasive surgery to treat kidney-stone disease associated with urinary obstruction. A short-pulsed Tm:YAG laser (λ = 2.01 µm) was developed to improve fragmentation efficiency and was evaluated with a Ho:YAG laser (λ = 2.12 μm) as to its ablation feature and mass removal rate. Application of a train of sub-microsecond pulses with a lower energy at a frequency of 500 Hz created multiple events of cavitation that accompanied strong acoustic transients. During Tm:YAG irradiation, both high light absorption and secondary photomechanical impacts readily fragmented the calculus into small pieces (< 3 mm) and removed them 130 times faster than photothermal Ho:YAG lithotripsy. The proposed short-pulsed Tm:YAG approach may be an effective lithotripter for treating calculus disease.

  11. 10th and 11th conference on Ultra-Wideband Short-Pulse Electromagnetics

    CERN Document Server

    Mokole, Eric; UWB SP 10; UWB SP 11

    2014-01-01

    This book presents contributions of deep technical content and high scientific quality in the areas of electromagnetic theory, scattering, UWB antennas, UWB systems, ground penetrating radar (GPR), UWB communications, pulsed-power generation, time-domain computational electromagnetics, UWB compatibility, target detection and discrimination, propagation through dispersive media, and wavelet and multi-resolution techniques. Ultra-wideband (UWB), short-pulse (SP) electromagnetics are now being used for an increasingly wide variety of applications, including collision avoidance radar, concealed object detection, and communications. Notable progress in UWB and SP technologies has been achieved by investigations of their theoretical bases and improvements in solid-state manufacturing, computers, and digitizers. UWB radar systems are also being used for mine clearing, oil pipeline inspections, archeology, geology, and electronic effects testing. Like previous books in this series, Ultra-Wideband Short-Pulse Electrom...

  12. 7th conference on ultra-wideband, short-pulse electromagnetics

    CERN Document Server

    Schenk, Uwe; Nitsch, Daniel; Sabath, Frank; Ultra-Wideband, Short-Pulse Electromagnetics 7; UWBSP7

    2007-01-01

    Ultra-wideband (UWB), short-pulse (SP) electromagnetics are now being used for an increasingly wide variety of applications, including collision avoidance radar, concealed object detection, and communications. Notable progress in UWB and SP technologies has been achieved by investigations of their theoretical bases and improvements in solid-state manufacturing, computers, and digitizers. UWB radar systems are also being used for mine clearing, oil pipeline inspections, archeology, geology, and electronic effects testing. Ultra-Wideband Short-Pulse Electromagnetics 7 presents selected papers of deep technical content and high scientific quality from the UWB-SP7 Conference, including wide-ranging contributions on electromagnetic theory, scattering, UWB antennas, UWB systems, ground penetrating radar (GPR), UWB communications, pulsed-power generation, time-domain computational electromagnetics, UWB compatibility, target detection and discrimination, propagation through dispersive media, and wavelet and multi-res...

  13. Prediction of short-term distributions of load extremes of offshore wind turbines

    Science.gov (United States)

    Wang, Ying-guang

    2016-12-01

    This paper proposes a new methodology to select an optimal threshold level to be used in the peak over threshold (POT) method for the prediction of short-term distributions of load extremes of offshore wind turbines. Such an optimal threshold level is found based on the estimation of the variance-to-mean ratio for the occurrence of peak values, which characterizes the Poisson assumption. A generalized Pareto distribution is then fitted to the extracted peaks over the optimal threshold level and the distribution parameters are estimated by the method of the maximum spacing estimation. This methodology is applied to estimate the short-term distributions of load extremes of the blade bending moment and the tower base bending moment at the mudline of a monopile-supported 5MW offshore wind turbine as an example. The accuracy of the POT method using the optimal threshold level is shown to be better, in terms of the distribution fitting, than that of the POT methods using empirical threshold levels. The comparisons among the short-term extreme response values predicted by using the POT method with the optimal threshold levels and with the empirical threshold levels and by using direct simulation results further substantiate the validity of the proposed new methodology.

  14. Prediction of short-term distributions of load extremes of offshore wind turbines

    Science.gov (United States)

    Wang, Ying-guang

    2016-09-01

    This paper proposes a new methodology to select an optimal threshold level to be used in the peak over threshold (POT) method for the prediction of short-term distributions of load extremes of offshore wind turbines. Such an optimal threshold level is found based on the estimation of the variance-to-mean ratio for the occurrence of peak values, which characterizes the Poisson assumption. A generalized Pareto distribution is then fitted to the extracted peaks over the optimal threshold level and the distribution parameters are estimated by the method of the maximum spacing estimation. This methodology is applied to estimate the short-term distributions of load extremes of the blade bending moment and the tower base bending moment at the mudline of a monopile-supported 5MW offshore wind turbine as an example. The accuracy of the POT method using the optimal threshold level is shown to be better, in terms of the distribution fitting, than that of the POT methods using empirical threshold levels. The comparisons among the short-term extreme response values predicted by using the POT method with the optimal threshold levels and with the empirical threshold levels and by using direct simulation results further substantiate the validity of the proposed new methodology.

  15. Long term outcome of treatment of diffuse proliferative glomerulonephritis with pulse steroids and short course pulse cyclophosphamide

    Directory of Open Access Journals (Sweden)

    S. Bombardieri

    2011-06-01

    Full Text Available Objectives: To evaluate the long- term outcome of a group of systemic lupus erythematosus (SLE patients with diffuse proliferative glomerulonephritis (DPGN treated with pulse steroids and a short course of pulse cyclophosphamide (Cyc in order to find out baseline predictor variables of disease outcome at the end of the follow-up. Methods: Female SLE patients fulfilling ACR criteria with active DPGN treated with pulse steroids and pulse Cyc were enrolled in the study and retrospectively analyzed with particular interest to renal flares and poor renal outcome at the end of follow- up as outcome measures. Results: 30 female patients with DPGN were included, of these 20 (66,7% patients are actually in follow-up at our unit, 4 (13.3% died and 6 (20% were lost during the follow-up. Fourteen patients (46.6% presented at least one renal flare (RF during the follow up for a total of 21 flares. At our last observation, 18 (60% presented a good renal outcome while 12 (40% had a poor outcome. Lower age at kidney biopsy resulted an important prognostic factor for the occurrence of both RF and poor long- term renal outcome; additionally, a poor renal outcome resulted significantly correlated with an inadequate response at the end of the protocol and with the number of renal flares after remission. Conclusions: These data suggest that, in general, a short course therapy with Cyc might be effective in controlling disease activity but demonstrated high rate of RF and poor renal outcome over time; however, this protocol might represent an effective therapeutic strategy in a subgroup of patients with specific epidemiological and clinical characteristics and suggest the possibility of tailoring immunosuppressive therapy on the basis of prognostic factor at baseline.

  16. [Long term outcome of treatment of diffuse proliferative glomerulonephritis with pulse steroids and short course pulse cyclophosphamide].

    Science.gov (United States)

    Tani, C; Mosca, M; d'Ascanio, A; Neri, R; Tavoni, A; Carli, L; Bombardieri, S

    2010-01-01

    To evaluate the long- term outcome of a group of systemic lupus erythematosus (SLE) patients with diffuse proliferative glomerulonephritis (DPGN) treated with pulse steroids and a short course of pulse cyclophosphamide (Cyc) in order to find out baseline predictor variables of disease outcome at the end of the follow-up. Female SLE patients fulfilling ACR criteria with active DPGN treated with pulse steroids and pulse Cyc were enrolled in the study and retrospectively analyzed with particular interest to renal flares and poor renal outcome at the end of follow- up as outcome measures. 30 female patients with DPGN were included, of these 20 (66,7%) patients are actually in follow-up at our unit, 4 (13.3%) died and 6 (20%) were lost during the follow-up. Fourteen patients (46.6%) presented at least one renal flare (RF) during the follow up for a total of 21 flares. At our last observation, 18 (60%) presented a good renal outcome while 12 (40%) had a poor outcome. Lower age at kidney biopsy resulted an important prognostic factor for the occurrence of both RF and poor long- term renal outcome; additionally, a poor renal outcome resulted significantly correlated with an inadequate response at the end of the protocol and with the number of renal flares after remission. These data suggest that, in general, a short course therapy with Cyc might be effective in controlling disease activity but demonstrated high rate of RF and poor renal outcome over time; however, this protocol might represent an effective therapeutic strategy in a subgroup of patients with specific epidemiological and clinical characteristics and suggest the possibility of tailoring immunosuppressive therapy on the basis of prognostic factor at baseline.

  17. Short optical pulse generation at 40 GHz with a bulk electro-absorption modulator packaged device

    Science.gov (United States)

    Langlois, Patrick; Moore, Ronald; Prosyk, Kelvin; O'Keefe, Sean; Oosterom, Jill A.; Betty, Ian; Foster, Robert; Greenspan, Jonathan; Singh, Priti

    2003-12-01

    Short optical pulse generation at 40GHz and 1540nm wavelength is achieved using fully packaged bulk quaternary electro-absorption modulator modules. Experimental results obtained with broadband and narrowband optimized packaged modules are presented and compared against empirical model predictions. Pulse duty cycle, extinction ratio and chirp are studied as a function of sinusoidal drive voltage and detuning between operating wavelength and modulator absorption band edge. Design rules and performance trade-offs are discussed. Low-chirp pulses with a FWHM of ~12ps and sub-4ps at a rate of 40GHz are demonstrated. Optical time-domain demultiplexing of a 40GHz to a 10GHz pulse train is also demonstrated with better than 20dB extinction ratio.

  18. An ultra short pulse reconstruction software applied to the GEMINI high power laser system

    Energy Technology Data Exchange (ETDEWEB)

    Galletti, Mario, E-mail: mario.gall22@gmail.com [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Galimberti, Marco [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Hooker, Chris [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); University of Oxford, Oxford (United Kingdom); Chekhlov, Oleg; Tang, Yunxin [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Bisesto, Fabrizio Giuseppe [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Curcio, Alessandro [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Sapienza – University of Rome, P.le Aldo Moro, 2, 00185 Rome (Italy); Anania, Maria Pia [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Giulietti, Danilo [Physics Department of the University and INFN, Pisa (Italy)

    2016-09-01

    The GRENOUILLE traces of Gemini pulses (15 J, 30 fs, PW, shot per 20 s) were acquired in the Gemini Target Area PetaWatt at the Central Laser Facility (CLF), Rutherford Appleton Laboratory (RAL). A comparison between the characterizations of the laser pulse parameters made using two different types of algorithms: Video Frog and GRenouille/FrOG (GROG), was made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign it has been showed how GROG, the developed algorithm, works as well as VideoFrog algorithm with the PetaWatt pulse class. - Highlights: • Integration of the diagnostic tool on high power laser. • Validation of the GROG algorithm in comparison to a well-known commercial available software. • Complete characterization of the GEMINI ultra-short high power laser pulse.

  19. Improving attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region

    Institute of Scientific and Technical Information of China (English)

    Lin Cheng-You; Chen Shu-Jing; Liu Da-He

    2013-01-01

    The improvement of attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region has been discussed.Numerical simulations of both spectral and temporal reflection characteristics of periodic multilayer mirrors under various incident angles have been analyzed and compared.It was found that the periodic multilayer mirror under a larger incidence angle can provide not only higher integrated reflectivity but also a broader reflection band with negligible dispersion,making it possible to obtain better a reflected pulse that has a higher pulse reflection efficiency and shorter pulse duration for attosecond pulse reflection.In addition,by increasing the incident angle,the promotion of attosecond pulse reflection capability has been proven for periodic multilayer mirrors with arbitrary layers.

  20. Applications of ultra-short pulsed laser ablation: thin films deposition and fs/ns dual-pulse laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Teghil, R; De Bonis, A; Galasso, A [Dipartimento di Chimica, Universita della Basilicata, Via N. Sauro 85, 85100 Potenza (Italy); Santagata, A; Albano, G; Villani, P; Spera, D; Parisi, G P [CNR-IMIP, Unita di Potenza, Via S. Loja, 85050 Tito Scalo (Italy)], E-mail: roberto.teghil@unibas.it

    2008-10-15

    In this paper, we report a survey of two of the large number of possible practical applications of the laser ablation performed by an ultra-short pulse laser, namely pulsed laser deposition (PLD) and fs/ns dual-pulse laser-induced breakdown spectroscopy (DP-LIBS). These applications differ from those using just longer pulsed lasers as a consequence of the distinctive characteristics of the plasma produced by ultra-short laser beams. The most important feature of this plasma is the large presence of particles with nanometric size which plays a fundamental role in both applications.

  1. Strong-field QED processes in short laser pulses. One- and two-photon Compton scattering

    Energy Technology Data Exchange (ETDEWEB)

    Seipt, Daniel

    2012-12-20

    The purpose of this thesis is to advance the understanding of strong-field QED processes in short laser pulses. The processes of non-linear one-photon and two-photon Compton scattering are studied, that is the scattering of photons in the interaction of relativistic electrons with ultra-short high-intensity laser pulses. These investigations are done in view of the present and next generation of ultra-high intensity optical lasers which are supposed to achieve unprecedented intensities of the order of 10{sup 24} W/cm{sup 2} and beyond, with pulse lengths in the order of some femtoseconds. The ultra-high laser intensity requires a non-perturbative description of the interaction of charged particles with the laser field to allow for multi-photon interactions, which is beyond the usual perturbative expansion of QED organized in powers of the fine structure constant. This is achieved in strong-field QED by employing the Furry picture and non-perturbative solutions of the Dirac equation in the presence of a background laser field as initial and final state wave functions, as well as the laser dressed Dirac-Volkov propagator. The primary objective is a realistic description of scattering processes with regard to the finite laser pulse duration beyond the common approximation of infinite plane waves, which is made necessary by the ultra-short pulse length of modern high-intensity lasers. Non-linear finite size effects are identified, which are a result of the interplay between the ultra-high intensity and the ultra-short pulse length. In particular, the frequency spectra and azimuthal photon emission spectra are studied emphasizing the differences between pulsed and infinite laser fields. The proper description of the finite temporal duration of the laser pulse leads to a regularization of unphysical infinities (due to the infinite plane-wave description) of the laser-dressed Dirac-Volkov propagator and in the second-order strong-field process of two-photon Compton

  2. Success of serial transverse enteroplasty in an adult with extreme short bowel syndrome: a case report.

    Science.gov (United States)

    Fan, Shengxian; Li, Yousheng; Zhang, Shaoyi; Wang, Jian; Li, Jieshou

    2015-04-01

    Since its introduction as an alternative intestinal lengthening technique, serial transverse enteroplasty has been increasingly used as the surgical treatment of choice for children with refractory short bowel syndrome, but there have been few reports about the adult patients. This report describes the case of a 71-year-old man with a short bowel after distal gastrectomy with Billroth II reconstruction for gastric cancer, followed by extensive intestinal resection. The serial transverse enteroplasty operation was performed and lengthened the small intestine from 49 to 67 cm. The patient tolerated the procedure well and weaned off total parenteral nutrition. Liver function also improved. This case shows that the serial transverse enteroplasty procedure increases intestinal length. This procedure should be considered a surgical option for adult patients with extreme short bowel syndrome.

  3. FY05 LDRD Final ReportTime-Resolved Dynamic Studies using Short Pulse X-Ray Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A; Dunn, J; van Buuren, T; Budil, K; Sadigh, B; Gilmer, G; Falcone, R; Lee, R; Ng, A

    2006-02-10

    Established techniques must be extended down to the ps and sub-ps time domain to directly probe product states of materials under extreme conditions. We used short pulse ({le} 1 ps) x-ray radiation to track changes in the physical properties in tandem with measurements of the atomic and electronic structure of materials undergoing fast laser excitation and shock-related phenomena. The sources included those already available at LLNL, including the picosecond X-ray laser as well as the ALS Femtosecond Phenomena beamline and the SSRL based sub-picosecond photon source (SPPS). These allow the temporal resolution to be improved by 2 orders of magnitude over the current state-of-the-art, which is {approx} 100 ps. Thus, we observed the manifestations of dynamical processes with unprecedented time resolution. Time-resolved x-ray photoemission spectroscopy and x-ray scattering were used to study phase changes in materials with sub-picosecond time resolution. These experiments coupled to multiscale modeling allow us to explore the physics of materials in high laser fields and extreme non-equilibrium states of matter. The ability to characterize the physical and electronic structure of materials under extreme conditions together with state-of-the-art models and computational facilities will catapult LLNL's core competencies into the scientific world arena as well as support its missions of national security and stockpile stewardship.

  4. Non-constant ponderomotive energy in above threshold ionization by intense short laser pulses

    CERN Document Server

    Della Picca, Renata; Garibotti, Carlos Roberto; López, Sebastián David; Arbó, Diego

    2015-01-01

    We analyze the contribution of the quiver kinetic energy acquired by an electron in an oscillating electric field to the energy balance in atomic ionization processes by a short laser pulse. Due to the time dependence of this additional kinetic energy, a temporal average is assumed to maintain a stationary energy conservation rule. This rule is used to predict the position of the peaks observed in the photo electron spectra (PE). For a flat top pulse envelope, the mean value of the quiver energy over the whole pulse leads to the concept of ponderomotive energy $U_{p}$. However for a short pulse with a fast changing field intensity a stationarity approximation could not be precise. We check these concepts by studying first the photoelectron (PE) spectrum within the Semiclassical Model (SCM) for a multiple steps pulses. The SCM offers the possibility to establish a connection between emission times and the PE spectrum in the energy domain. We show that PE substructures stem from ionization at different times ma...

  5. Generation of isolated attosecond extreme ultraviolet pulses employing nanoplasmonic field enhancement: optimization of coupled ellipsoids

    Energy Technology Data Exchange (ETDEWEB)

    Stebbings, S L; Suessmann, F; Yang, Y-Y; Kling, M F [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strass e 1, 85748 Garching (Germany); Scrinzi, A [Ludwig-Maximilians-Universitaet Muenchen, Theresienstrasse 37, 80333 Muenchen (Germany); Durach, M; Rusina, A; Stockman, M I, E-mail: sarah.stebbings@mpq.mpg.de, E-mail: mstockman@gsu.edu, E-mail: matthias.kling@mpq.mpg.de [Department of Physics and Astronomy, Georgia State University, 29 Peachtree Center Avenue, Atlanta, GA 30303 (United States)

    2011-07-15

    The production of extreme ultraviolet (XUV) radiation via nanoplasmonic field-enhanced high-harmonic generation (HHG) in gold nanostructures at MHz repetition rates is investigated theoretically in this paper. Analytical and numerical calculations are employed and compared in order to determine the plasmonic fields in gold ellipsoidal nanoparticles. The comparison indicates that numerical calculations can accurately predict the field enhancement and plasmonic decay, but may encounter difficulties when attempting to predict the oscillatory behavior of the plasmonic field. Numerical calculations for coupled symmetric and asymmetric ellipsoids for different carrier-envelope phases (CEPs) of the driving laser field are combined with time-dependent Schroedinger equation simulations to predict the resulting HHG spectra. The studies reveal that the plasmonic field oscillations, which are controlled by the CEP of the driving laser field, play a more important role than the nanostructure configuration in finding the optimal conditions for the generation of isolated attosecond XUV pulses via nanoplasmonic field enhancement.

  6. Generation of isolated attosecond extreme ultraviolet pulses employing nanoplasmonic field enhancement: optimization of coupled ellipsoids

    Science.gov (United States)

    Stebbings, S. L.; Süßmann, F.; Yang, Y.-Y.; Scrinzi, A.; Durach, M.; Rusina, A.; Stockman, M. I.; Kling, M. F.

    2011-07-01

    The production of extreme ultraviolet (XUV) radiation via nanoplasmonic field-enhanced high-harmonic generation (HHG) in gold nanostructures at MHz repetition rates is investigated theoretically in this paper. Analytical and numerical calculations are employed and compared in order to determine the plasmonic fields in gold ellipsoidal nanoparticles. The comparison indicates that numerical calculations can accurately predict the field enhancement and plasmonic decay, but may encounter difficulties when attempting to predict the oscillatory behavior of the plasmonic field. Numerical calculations for coupled symmetric and asymmetric ellipsoids for different carrier-envelope phases (CEPs) of the driving laser field are combined with time-dependent Schrödinger equation simulations to predict the resulting HHG spectra. The studies reveal that the plasmonic field oscillations, which are controlled by the CEP of the driving laser field, play a more important role than the nanostructure configuration in finding the optimal conditions for the generation of isolated attosecond XUV pulses via nanoplasmonic field enhancement.

  7. Extreme ultraviolet emission from dense plasmas generated with sub-10-fs laser pulses

    CERN Document Server

    Osterholz, J; Cerchez, M; Fischer, T; Hemmers, D; Hidding, B; Pipahl, A; Pretzler, G; Rose, S J; Willi, O

    2008-01-01

    The extreme ultraviolet (XUV) emission from dense plasmas generated with sub-10-fs laser pulses with varying peak intensities up to 3*10^16 W/cm^2 is investigated for different target materials. K shell spectra are obtained from low Z targets (carbon and boron nitride). In the spectra a series limit for the hydrogen and helium like resonance lines is observed indicating that the plasma is at high density and pressure ionization has removed the higher levels. In addition, L shell spectra from titanium targets were obtained. Basic features of the K and L shell spectra are reproduced with computer simulations. The calculations include hydrodynamic simulation of the plasma expansion and collisional radiative calculations of the XUV emission.

  8. A Comparison of AC and Short-Pulse Excitation for Xe Excimer Barrier Discharge Lamps

    Science.gov (United States)

    Mildren, R. P.; Morrow, R.; Carman, R. J.

    1999-10-01

    Dielectric barrier discharge excitation of rare-gas and rare-gas halide excimers provides an efficient scheme for generating intense VUV radiation for applications including lighting, ozonisation, and photochemical surface treatment. Typically, lamps employ AC (sinusoidal) voltage excitation in which case VUV emission is produced from short-livid micro discharges (streamers) distributed stochastically over the dielectric. However, it has been recently demonstrated that significantly increased efficiency (by factor 2-3) can be obtained from Xe lamps when using short excitation pulses separated by idle periods[1]. In this paper, we report an investigation into the mechanisms which bring about improved efficiency by comparing the electrical, spectral and spatial emission characteristics of a small-scale Xe lamp excited by short pulses ( 100ns) with that of conventional AC excitation. The results reveal that pulsed excitation produces a homogenous glow-like discharge in which the electron density and temperature are more favourable for efficient excimer production. [1] RP Mildren et al, IVth Int. Conf. Atom. and Molec. Pulsed Lasers, Tomsk, Siberia Sept. (1999); F Vollkommer and L Hitzschke, Proc. 8th Int. Symp. Sci. Tech. Light Sources, Greifswald, Germany, '98, IL-07, pp51-59 (1998)

  9. Oral applications of ultra-short laser pulses: a new approach for gentle and painless treatment?

    Science.gov (United States)

    Yousif, A.; Strassl, M.; Wieger, V.; Zoppel, S.; Wintner, E.

    2006-05-01

    In dental hard tissue ablation, ultra-short laser pulses have proven sufficiently their potential for material ablation with negligible collateral damage providing many advantages. The absence of microcracks and the possibility to avoid overheating of the pulp during dental cavity preparation may be among the most important issues, the latter opening up an avenue for potential painless treatment. Beside the evident short interaction time of laser radiation with the irradiated tissue, scanning of the ultra-short pulse trains turned out to be crucial for ablating cavities of required quality and shape. Additionally, such a technique allows to treat larger areas like the ones dentists are used to work with, i.e. ~ 1 mm Ø.In this paper, an overview of different scanning methods together with the algorithms used and an assessment of their applicability is presented. A variety of pulse durations from ~100 fs up to several ps has been used by numerous authors over the last approximately ten years. Having employed 330 fs pulses, we present the corresponding ablation thresholds for dental hard tissue (enamel, dentine; human and bovine), for a number of dental restoration materials, as well as for different types of bovine bone. Dental implants frequently have to be cleaned from plaque being deposited around their necks in areas where the gums have already retreated. A preliminary investigation is presented on the applicability of ultra-short pulses with mentioned duration for the gentle cleaning of titanium implants focusing on the preservation of the special plasma-sprayed biocompatible implant surface.

  10. Interaction of ultra-short laser pulses with CIGS and CZTSe thin films

    Science.gov (United States)

    Gečys, P.; Markauskas, E.; Dudutis, J.; Račiukaitis, G.

    2014-01-01

    The thin-film solar cell technologies based on complex quaternary chalcopyrite and kesterite materials are becoming more attractive due to their potential for low production costs and optimal spectral performance. As in all thin-film technologies, high efficiency of small cells might be maintained with the transition to larger areas when small segments are interconnected in series to reduce photocurrent and related ohmic losses in thin films. Interconnect formation is based on the three scribing steps, and the use of a laser is here crucial for performance of the device. We present our simulation and experimental results on the ablation process investigations in complex CuIn1- x Ga x Se2 (CIGS) and Cu2ZnSn(S,Se)4 (CZTSe) cell's films using ultra-short pulsed infrared (~1 μm) lasers which can be applied to the damage-free front-side scribing processes. Two types of processes were investigated—direct laser ablation of ZnO:Al/CIGS films with a variable pulse duration of a femtosecond laser and the laser-induced material removal with a picosecond laser in the ZnO:Al/CZTSe structure. It has been found that the pulse energy and the number of laser pulses have a significantly stronger effect on the ablation quality in ZnO:Al/CIGS thin films rather than the laser pulse duration. For the thin-film scribing applications, it is very important to carefully select the processing parameters and use of ultra-short femtosecond pulses does not have a significant advantage compared to picosecond laser pulses. Investigations with the ZnO:Al/CZTSe thin films showed that process of the absorber layer removal was triggered by a micro-explosive effect induced by high pressure of sublimated material due to a rapid temperature increase at the molybdenum-CZTSe interface.

  11. Third Harmonic Generation of a Short Pulse Laser in a Tunnel Ionizing Plasma: Effect of Self-Defocusing

    OpenAIRE

    Niti Kant

    2013-01-01

    Third harmonic generation of a Gaussian short pulse laser in a tunnel ionizing plasma is investigated. A Gaussian short pulse laser propagating through a tunnel ionizing plasma generates third harmonic wave. Inhomogeneity of the electric field along the wavefront of the fundamental laser pulse causes more ionization along the axis of propagation while less ionization off axis, leading to strong density gradient with its maximum on the axis of propagation. The medium acts like a diverging lens...

  12. Hot electrons generated by ultra-short pulse laser interacting with solid targets

    Institute of Scientific and Technical Information of China (English)

    陈黎明; 张杰; 李玉同; 梁天骄; 王龙; 魏志义; 江文勉

    2000-01-01

    Hot electrons produced by ultra-short pulse laser interacting with solid targets were studied systematically. When 800 nm, 8 × 1015 W/cm2 laser pulses interacted with solid targets, hot electron e-mission was found to be collimated in certain directions and the angular distribution of hot electrons depended on the energy absorption. The angular divergence of outgoing hot electrons was inversely proportional to the hot electron energy. The energy spectrum of hot electrons was found to be in a bi-Maxwellian distribution and the maximum energy was over 500 keV.

  13. Hot electrons generated by ultra-short pulse laser interacting with solid targets

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Hot electrons produced by ultra-short pulse laser interacting with solid targets were studied systematically. When 800 nm, 8×1015 W/cm2 laser pulses interacted with solid targets, hot electron emission was found to be collimated in certain directions and the angular distribution of hot electrons depended on the energy absorption. The angular divergence of outgoing hot electrons was inversely proportional to the hot electron energy. The energy spectrum of hot electrons was found to be in a bi-Maxwellian distribution and the maximum energy was over 500 keV.

  14. Ultra-short pulse reconstruction software in high power laser system

    Energy Technology Data Exchange (ETDEWEB)

    Galletti, M. [Physics Department of the University and INFN, Pisa (Italy); Galimberti, M. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Giulietti, D. [Physics Department of the University and INFN, Pisa (Italy)

    2015-07-15

    An ultra-short pulse reconstruction software, validated through a set of experimental measurements on the front-end of the Vulcan laser at the RAL Central Laser Facility is presented. The measurements were acquired in Target Area Petawatt of the Vulcan laser, both using a conventional autocorrelation technique and the GRENOUILLE technique in order to compare the results. The FWHM of the laser pulses considered came out to be comparable for the two techniques. In this experimental campaign for the first time a technique different from the autocorrelation one has been used for a PW class laser as Vulcan.

  15. Short Intense Laser Pulse Depletion and Scattering in Under-Dense Plasma

    CERN Document Server

    Yazdanpanah, Jam; Khalilzadeh, Elnaz; Chakhmachi, Amir

    2016-01-01

    Nonlinear evolutions of an ultra-intense, short laser pulse due to the wake excitation inside the plasma are studied by means of detailed particle-in-cell simulations and comprehensive analyses. Pulse lengths both longer and shorter than the plasma wavelength are considered. A new adiabatic regime of the interaction is identified in connection with the quasi-static being of the plasma in the pulse commoving frame. This situation occurs when radiation back-reactions are ignorable in the commoving frame against the measured high plasma momentum. By formulating this regime in terms of the local conservation laws, we calculate the overall pulse depletion and more importantly the global pulse group velocity. The outcome for the group velocity shows non-explicit density dependency and, strangely, remains above the linear value over a long time period. Further, we examine the model adequacy at different applied parameters via comparison with simulations. It is turned out that for pulse lengths larger than the plasma...

  16. Short-Pulse, Compressed Ion Beams at the Neutralized Drift Compression Experiment

    CERN Document Server

    Seidl, Peter A; Davidson, Ronald C; Friedman, Alex; Gilson, Erik P; Grote, David; Ji, Qing; Kaganovich, I D; Persaud, Arun; Waldron, William L; Schenkel, Thomas

    2016-01-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynam...

  17. High-pressure (>1-bar) dielectric barrier discharge lamps generating short pulses of high-peak power vacuum ultraviolet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Carman, R J; Mildren, R P; Ward, B K; Kane, D M [Short Wavelength Interactions with Materials (SWIM), Physics Department, Macquarie University, North Ryde, Sydney, NSW 2109 (Australia)

    2004-09-07

    We have investigated the scaling of peak vacuum ultraviolet output power from homogeneous Xe dielectric barrier discharges excited by short voltage pulses. Increasing the Xe fill pressure above 1-bar provides an increased output pulse energy, a shortened pulse duration and increases in the peak output power of two to three orders of magnitude. High peak power pulses of up to 6 W cm{sup -2} are generated with a high efficiency for pulse rates up to 50 kHz. We show that the temporal pulse characteristics are in good agreement with results from detailed computer modelling of the discharge kinetics.

  18. Complex extreme learning machine applications in terahertz pulsed signals feature sets.

    Science.gov (United States)

    Yin, X-X; Hadjiloucas, S; Zhang, Y

    2014-11-01

    This paper presents a novel approach to the automatic classification of very large data sets composed of terahertz pulse transient signals, highlighting their potential use in biochemical, biomedical, pharmaceutical and security applications. Two different types of THz spectra are considered in the classification process. Firstly a binary classification study of poly-A and poly-C ribonucleic acid samples is performed. This is then contrasted with a difficult multi-class classification problem of spectra from six different powder samples that although have fairly indistinguishable features in the optical spectrum, they also possess a few discernable spectral features in the terahertz part of the spectrum. Classification is performed using a complex-valued extreme learning machine algorithm that takes into account features in both the amplitude as well as the phase of the recorded spectra. Classification speed and accuracy are contrasted with that achieved using a support vector machine classifier. The study systematically compares the classifier performance achieved after adopting different Gaussian kernels when separating amplitude and phase signatures. The two signatures are presented as feature vectors for both training and testing purposes. The study confirms the utility of complex-valued extreme learning machine algorithms for classification of the very large data sets generated with current terahertz imaging spectrometers. The classifier can take into consideration heterogeneous layers within an object as would be required within a tomographic setting and is sufficiently robust to detect patterns hidden inside noisy terahertz data sets. The proposed study opens up the opportunity for the establishment of complex-valued extreme learning machine algorithms as new chemometric tools that will assist the wider proliferation of terahertz sensing technology for chemical sensing, quality control, security screening and clinic diagnosis. Furthermore, the proposed

  19. Direct generation of intense extreme ultraviolet supercontinuum with chirped 11-mJ pulses from a femtosecond laser amplifier

    CERN Document Server

    Zeng, Bin; Li, Guihua; Yao, Jinping; Ni, Jielei; Zhang, Haisu; Cheng, Ya; Xu, Zhizhan

    2011-01-01

    We report on the generation of intense extreme ultraviolet (EUV) supercontinuum with photon energies spanning from 35 eV to 50 eV (i. e., supporting an isolated attosecond pulse with a duration of ~271 as) by loosely focusing 11-mJ chirped pulses from a femtosecond laser amplifier into a 10-mm long gas cell filled with krypton gas. We observe that when high-order harmonics are generated with transformed-limited ~35 fs pulses, only discrete harmonics can be produced; whereas for negatively chirped 188 fs pulses, EUV supercontinuum can be observed in single-shot harmonic spectrum. The dramatic change of spectral and temporal properties of the driver pulses after passing through the gas cell indicates that propagation effects play a significant role in promoting the generation of the EUV supercontinuum.

  20. Two-colour pump–probe experiments with a twin-pulse-seed extreme ultraviolet free-electron laser

    Science.gov (United States)

    Allaria, E.; Bencivenga, F.; Borghes, R.; Capotondi, F.; Castronovo, D.; Charalambous, P.; Cinquegrana, P.; Danailov, M. B.; De Ninno, G.; Demidovich, A.; Di Mitri, S.; Diviacco, B.; Fausti, D.; Fawley, W. M.; Ferrari, E.; Froehlich, L.; Gauthier, D.; Gessini, A.; Giannessi, L.; Ivanov, R.; Kiskinova, M.; Kurdi, G.; Mahieu, B.; Mahne, N.; Nikolov, I.; Masciovecchio, C.; Pedersoli, E.; Penco, G.; Raimondi, L.; Serpico, C.; Sigalotti, P.; Spampinati, S.; Spezzani, C.; Svetina, C.; Trovò, M.; Zangrando, M.

    2013-01-01

    Exploring the dynamics of matter driven to extreme non-equilibrium states by an intense ultrashort X-ray pulse is becoming reality, thanks to the advent of free-electron laser technology that allows development of different schemes for probing the response at variable time delay with a second pulse. Here we report the generation of two-colour extreme ultraviolet pulses of controlled wavelengths, intensity and timing by seeding of high-gain harmonic generation free-electron laser with multiple independent laser pulses. The potential of this new scheme is demonstrated by the time evolution of a titanium-grating diffraction pattern, tuning the two coherent pulses to the titanium M-resonance and varying their intensities. This reveals that an intense pulse induces abrupt pattern changes on a time scale shorter than hydrodynamic expansion and ablation. This result exemplifies the essential capabilities of the jitter-free multiple-colour free-electron laser pulse sequences to study evolving states of matter with element sensitivity. PMID:24048228

  1. Two-colour pump-probe experiments with a twin-pulse-seed extreme ultraviolet free-electron laser.

    Science.gov (United States)

    Allaria, E; Bencivenga, F; Borghes, R; Capotondi, F; Castronovo, D; Charalambous, P; Cinquegrana, P; Danailov, M B; De Ninno, G; Demidovich, A; Di Mitri, S; Diviacco, B; Fausti, D; Fawley, W M; Ferrari, E; Froehlich, L; Gauthier, D; Gessini, A; Giannessi, L; Ivanov, R; Kiskinova, M; Kurdi, G; Mahieu, B; Mahne, N; Nikolov, I; Masciovecchio, C; Pedersoli, E; Penco, G; Raimondi, L; Serpico, C; Sigalotti, P; Spampinati, S; Spezzani, C; Svetina, C; Trovò, M; Zangrando, M

    2013-01-01

    Exploring the dynamics of matter driven to extreme non-equilibrium states by an intense ultrashort X-ray pulse is becoming reality, thanks to the advent of free-electron laser technology that allows development of different schemes for probing the response at variable time delay with a second pulse. Here we report the generation of two-colour extreme ultraviolet pulses of controlled wavelengths, intensity and timing by seeding of high-gain harmonic generation free-electron laser with multiple independent laser pulses. The potential of this new scheme is demonstrated by the time evolution of a titanium-grating diffraction pattern, tuning the two coherent pulses to the titanium M-resonance and varying their intensities. This reveals that an intense pulse induces abrupt pattern changes on a time scale shorter than hydrodynamic expansion and ablation. This result exemplifies the essential capabilities of the jitter-free multiple-colour free-electron laser pulse sequences to study evolving states of matter with element sensitivity.

  2. Projected changes to short- and long-duration precipitation extremes over the Canadian Prairie Provinces

    Science.gov (United States)

    Masud, M. B.; Khaliq, M. N.; Wheater, H. S.

    2017-09-01

    The effects of climate change on April-October short- and long-duration precipitation extremes over the Canadian Prairie Provinces were evaluated using a multi-Regional Climate Model (RCM) ensemble available through the North American Regional Climate Change Assessment Program. Simulations considered include those performed with six RCMs driven by the National Centre for Environmental Prediction (NCEP) reanalysis II product for the 1981-2000 period and those driven by four Atmosphere-Ocean General Circulation Models (AOGCMs) for the current 1971-2000 and future 2041-2070 periods (i.e. a total of 11 current-to-future period simulation pairs). A regional frequency analysis approach was used to develop 2-, 5-, 10-, 25-, and 50-year return values of precipitation extremes from NCEP and AOGCM-driven current and future period simulations that respectively were used to study the performance of RCMs and projected changes for selected return values at regional, grid-cell and local scales. Performance errors due to internal dynamics and physics of RCMs studied for the 1981-2000 period reveal considerable variation in the performance of the RCMs. However, the performance errors were found to be much smaller for RCM ensemble averages than for individual RCMs. Projected changes in future climate to selected regional return values of short-duration (e.g. 15- and 30-min) precipitation extremes and for longer return periods (e.g. 50-year) were found to be mostly larger than those to the longer duration (e.g. 24- and 48-h) extremes and short return periods (e.g. 2-year). Overall, projected changes in precipitation extremes were larger for southeastern regions followed by southern and northern regions and smaller for southwestern and western regions of the study area. The changes to return values were also found to be statistically significant for the majority of the RCM-AOGCM simulation pairs. These projections might be useful as a key input for the future planning of urban

  3. Projected changes to short- and long-duration precipitation extremes over the Canadian Prairie Provinces

    Science.gov (United States)

    Masud, M. B.; Khaliq, M. N.; Wheater, H. S.

    2016-10-01

    The effects of climate change on April-October short- and long-duration precipitation extremes over the Canadian Prairie Provinces were evaluated using a multi-Regional Climate Model (RCM) ensemble available through the North American Regional Climate Change Assessment Program. Simulations considered include those performed with six RCMs driven by the National Centre for Environmental Prediction (NCEP) reanalysis II product for the 1981-2000 period and those driven by four Atmosphere-Ocean General Circulation Models (AOGCMs) for the current 1971-2000 and future 2041-2070 periods (i.e. a total of 11 current-to-future period simulation pairs). A regional frequency analysis approach was used to develop 2-, 5-, 10-, 25-, and 50-year return values of precipitation extremes from NCEP and AOGCM-driven current and future period simulations that respectively were used to study the performance of RCMs and projected changes for selected return values at regional, grid-cell and local scales. Performance errors due to internal dynamics and physics of RCMs studied for the 1981-2000 period reveal considerable variation in the performance of the RCMs. However, the performance errors were found to be much smaller for RCM ensemble averages than for individual RCMs. Projected changes in future climate to selected regional return values of short-duration (e.g. 15- and 30-min) precipitation extremes and for longer return periods (e.g. 50-year) were found to be mostly larger than those to the longer duration (e.g. 24- and 48-h) extremes and short return periods (e.g. 2-year). Overall, projected changes in precipitation extremes were larger for southeastern regions followed by southern and northern regions and smaller for southwestern and western regions of the study area. The changes to return values were also found to be statistically significant for the majority of the RCM-AOGCM simulation pairs. These projections might be useful as a key input for the future planning of urban

  4. A novel generation scheme of ultra-short pulse trains with multiple wavelengths

    Science.gov (United States)

    Su, Yulong; Hu, Hui; Feng, Huan; Li, Lu; Han, Biao; Wen, Yu; Wang, Yishan; Si, Jinhai; Xie, Xiaoping; Wang, Weiqiang

    2017-04-01

    We demonstrate a novel scheme based on active mode locking combined with four-wave mixing (FWM) to generate ultra-short pulse trains at high repetition rate with multiple wavelengths for applications in various fields. The obtained six wavelengths display high uniformity both in temporal and frequency domain. Pulses at each wavelength are mode locked with pulse duration of 44.37 ps, signal-to-noise ratio (SNR) of 47.89 dB, root-mean-square (RMS) timing jitter of 552.7 fs, and the time-bandwidth product of 0.68 at repetition rate of 1 GHz. The experimental results show this scheme has promising usage in optical communications, optical networks, and fiber sensing.

  5. All-optical short pulse translation through cross-phase modulation in a VO₂ thin film.

    Science.gov (United States)

    Fardad, Shima; Das, Susobhan; Salandrino, Alessandro; Breckenfeld, Eric; Kim, Heungsoo; Wu, Judy; Hui, Rongqing

    2016-01-15

    VO2 is a promising material for reconfigurable photonic devices due to the ultrafast changes in electronic and optical properties associated with its dielectric-to-metal phase transition. Based on a fiber-optic, pump-probe setup at 1550 nm wavelength window, and by varying the pump-pulse duration, we show that the material phase transition is primarily caused by the pump-pulse energy. For the first time, we demonstrate that the instantaneous optical phase modulation of probe during pump leading edge can be utilized to create short optical pulses at probe wavelength, through optical frequency discrimination. This circumvents the impact of long recovery time well known for the phase transition of VO2.

  6. Ship motion extreme short time prediction of ship pitch based on diagonal recurrent neural network

    Institute of Scientific and Technical Information of China (English)

    SHEN Yan; XIE Mei-ping

    2005-01-01

    A DRNN (diagonal recurrent neural network) and its RPE (recurrent prediction error) learning algorithm are proposed in this paper .Using of the simple structure of DRNN can reduce the capacity of calculation. The principle of RPE learning algorithm is to adjust weights along the direction of Gauss-Newton. Meanwhile, it is unnecessary to calculate the second local derivative and the inverse matrixes, whose unbiasedness is proved. With application to the extremely short time prediction of large ship pitch, satisfactory results are obtained. Prediction effect of this algorithm is compared with that of auto-regression and periodical diagram method, and comparison results show that the proposed algorithm is feasible.

  7. Comparison of short pulse generation schemes for a soft x-ray free electron laser

    Science.gov (United States)

    Martin, I. P. S.; Bartolini, R.

    2011-03-01

    In this paper we study the performance of two complementary short pulse generation schemes as applied to a soft x-ray free electron laser. The first scheme, recently proposed by Saldin et al., makes use of a laser pulse consisting of only a few optical cycles to give an energy chirp to a short section of an electron bunch and tapers the main radiator undulator in order to compensate the chirped region. The second scheme investigated takes a low-charge, high brightness electron bunch and compresses it to ˜1fs in order to operate in the so-called “single-spike” regime. We perform start-to-end simulations of both these schemes, assess the sensitivity of each scheme to realistic jitter sources, and provide a direct comparison of the respective strengths and drawbacks.

  8. Comparison of short pulse generation schemes for a soft x-ray free electron laser

    Directory of Open Access Journals (Sweden)

    I. P. S. Martin

    2011-03-01

    Full Text Available In this paper we study the performance of two complementary short pulse generation schemes as applied to a soft x-ray free electron laser. The first scheme, recently proposed by Saldin et al., makes use of a laser pulse consisting of only a few optical cycles to give an energy chirp to a short section of an electron bunch and tapers the main radiator undulator in order to compensate the chirped region. The second scheme investigated takes a low-charge, high brightness electron bunch and compresses it to ∼1  fs in order to operate in the so-called “single-spike” regime. We perform start-to-end simulations of both these schemes, assess the sensitivity of each scheme to realistic jitter sources, and provide a direct comparison of the respective strengths and drawbacks.

  9. Comment on "Defocusing complex short-pulse equation and its multi-dark-soliton solution"

    Science.gov (United States)

    Youssoufa, Saliou; Kuetche, Victor K.; Kofane, Timoleon C.

    2017-08-01

    In their recent paper, Feng et al. [Phys. Rev. E 93, 052227 (2016), 10.1103/PhysRevE.93.052227] proposed a complex short-pulse equation of both focusing and defocusing types. They studied in detail the defocusing case and derived its multi-dark-soliton solutions. Nonetheless, from a physical viewpoint in order to better and deeply understand their genuine implications, we find it useful to provide a real and proper background for the derivation of the previous evolution system while showing that the expression of the nonlinear electric polarization the above authors used in their scheme is not suitable for getting the defocusing complex short-pulse equation.

  10. Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate

    Science.gov (United States)

    Li, Jianhui; Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-11-01

    A short-pulse longitudinally excited CO2 laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO2:N2:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

  11. Transient Self-Amplified Cerenkov Radiation with a Short Pulse Electron Beam

    Energy Technology Data Exchange (ETDEWEB)

    Poole, B R; Blackfield, D T; Camacho, J F

    2009-01-22

    An analytic and numerical examination of the slow wave Cerenkov free electron maser is presented. We consider the steady state amplifier configuration as well as operation in the selfamplified spontaneous emission (SASE) regime. The linear theory is extended to include electron beams that have a parabolic radial density inhomogeneity. Closed form solutions for the dispersion relation and modal structure of the electromagnetic field are determined in this inhomogeneous case. To determine the steady state response, a macro-particle approach is used to develop a set of coupled nonlinear ordinary differential equations for the amplitude and phase of the electromagnetic wave, which are solved in conjunction with the particle dynamical equations to determine the response when the system is driven as an amplifier with a time harmonic source. We then consider the case in which a fast rise time electron beam is injected into a dielectric loaded waveguide. In this case, radiation is generated by SASE, with the instability seeded by the leading edge of the electron beam. A pulse of radiation is produced, slipping behind the leading edge of the beam due to the disparity between the group velocity of the radiation and the beam velocity. Short pulses of microwave radiation are generated in the SASE regime and are investigated using particle-in-cell (PIC) simulations. The nonlinear dynamics are significantly more complicated in the transient SASE regime when compared with the steady state amplifier model due to the slippage of the radiation with respect to the beam. As strong self-bunching of the electron beam develops due to SASE, short pulses of superradiant emission develop with peak powers significantly larger than the predicted saturated power based on the steady state amplifier model. As these superradiant pulses grow, their pulse length decreases and forms a series of soliton-like pulses. Comparisons between the linear theory, macro-particle model, and PIC simulations are

  12. Effects of temporal laser profile on the emission spectra for underwater laser-induced breakdown spectroscopy: Study by short-interval double pulses with different pulse durations

    Energy Technology Data Exchange (ETDEWEB)

    Tamura, Ayaka, E-mail: tamura.ayaka.88m@st.kyoto-u.ac.jp; Matsumoto, Ayumu; Nishi, Naoya; Sakka, Tetsuo, E-mail: sakka.tetsuo.2a@kyoto-u.ac.jp [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan); Nakajima, Takashi; Ogata, Yukio H. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Fukami, Kazuhiro [Department of Materials Science and Engineering, Graduate School of Engineering, Kyoto University, Kyoto 606-8501 (Japan)

    2015-01-14

    We investigate the effects of temporal laser profile on the emission spectra of laser ablation plasma in water. We use short-interval (76 ns) double pulses with different pulse durations of the composing two pulses for the irradiation of underwater target. Narrow atomic spectral lines in emission spectra are obtained by the irradiation, where the two pulses are wide enough to be merged into a single-pulse-like temporal profile, while deformed spectra are obtained when the two pulses are fully separated. The behavior of the atomic spectral lines for the different pulse durations is consistent with that of the temporal profiles of the optical emission intensities of the plasma. All these results suggest that continuous excitation of the plasma during the laser irradiation for ∼100 ns is a key to obtain narrow emission spectral lines.

  13. Enhanced efficiency from a Xe excimer barrier discharge lamp employing short-pulsed excitation

    Science.gov (United States)

    Mildren, Richard P.; Morrow, R.; Carman, Robert J.

    2000-04-01

    We have measured the efficiency and spatial characteristics of output radiation as a function of fill pressure for a Xe excimer lamp employing a short voltage pulse (approximately 100 ns) excitation circuit, and compared the results with those obtained using conventional AC (ie. sinusoidal voltage waveform). When using pulsed excitation, VUV output is obtained from a homogeneous discharge at efficiencies which increase linearly with Xe pressure in the range 50 - 750 torr up to 3.2X the maximum efficiency obtained when using AC. When using AC excitation, the efficiency saturates with increasing pressure > 350 torr for which pressures the discharge appearance is altered from a diffuse discharge to one which is comprised of stochastic or stationary filaments. We have also recorded discharge spectra which highlight the different character of the homogeneous and filamented types of discharges. It is deduced that the enhanced efficiency arises due to the capability of pulsed excitation to produce a homogeneous (glow-like) discharge at higher pressure, which brings about more optimal electron density and temperature conditions for exclusively exciting Xe metastables than possible using AC. We attribute the homogenizing effect of short-pulsed excitation to the rapid rate at which the applied E-field increases to the necessary value for homogeneous discharge breakdown to proceed at a faster rate than the formation of filaments.

  14. Advanced concepts for high-power, short-pulse CO2 laser development

    Science.gov (United States)

    Gordon, Daniel F.; Hasson, Victor; von Bergmann, Hubertus; Chen, Yu-hsin; Schmitt-Sody, A.; Penano, Joseph R.

    2016-06-01

    Ultra-short pulse lasers are dominated by solid-state technology, which typically operates in the near-infrared. Efforts to extend this technology to longer wavelengths are meeting with some success, but the trend remains that longer wavelengths correlate with greatly reduced power. The carbon dioxide (CO2) laser is capable of delivering high energy, 10 micron wavelength pulses, but the gain structure makes operating in the ultra-short pulse regime difficult. The Naval Research Laboratory and Air Force Research Laboratory are developing a novel CO2 laser designed to deliver ~1 Joule, ~1 picosecond pulses, from a compact gain volume (~2x2x80 cm). The design is based on injection seeding an unstable resonator, in order to achieve high energy extraction efficiency, and to take advantage of power broadening. The unstable resonator is seeded by a solid state front end, pumped by a custom built titanium sapphire laser matched to the CO2 laser bandwidth. In order to access a broader range of mid infrared wavelengths using CO2 lasers, one must consider nonlinear frequency multiplication, which is non-trivial due to the bandwidth of the 10 micron radiation.

  15. Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

    Science.gov (United States)

    Mahalik, S. S.; Kundu, M.

    2016-12-01

    Linear resonance (LR) absorption of an intense 800 nm laser light in a nano-cluster requires a long laser pulse >100 fs when Mie-plasma frequency ( ω M ) of electrons in the expanding cluster matches the laser frequency (ω). For a short duration of the pulse, the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency Ω [ r ( t ) ] of an electron in the self-consistent anharmonic potential of the cluster satisfies Ω [ r ( t ) ] = ω . However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its Ω [ r ( t ) ] in the self-generated anharmonic plasma potential, it is found that electron is outer ionized only when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models, and MD calculations for the first time but also unequivocally prove that AHR process is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.

  16. Ion motion effects on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration

    Institute of Scientific and Technical Information of China (English)

    W.P.Wang; X.M.Zhang; X.F.Wang; X.Y.Zhao; J.C.Xu; Y.H.Yu; L.Q.Yi; Y.Shi; L.G.Zhang; T.J.Xu; C.Liu; Z.K.Pei; B.F.Shen

    2014-01-01

    The effects of ion motion on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration are investigated by analytical modeling and particle-in-cell simulations. Studies show that the rear part of the transmitted pulse modulated by ion motion is sharper compared with the case of the electron shutter only. In this study, the ions further modulate the short-cycle pulses transmitted. A 3.9 fs laser pulse with an intensity of 1.33×1021W cm-2is generated by properly controlling the motions of the electron and ion in the simulations. The short-cycle laser pulse source proposed can be applied in the generation of single attosecond pulses and electron acceleration in a small bubble regime.

  17. Target Recognition Using Late-Time Returns from Ultra-Wideband, Short-Pulse Radar

    Science.gov (United States)

    2004-06-01

    WIDEBAND, SHORT-PULSE RADAR DISSERTATION Kenneth J. Pascoe, B.S.E.E., M.S. Major, USAF Approved: Dr. Michael J. Havrilla Dissertation Advisor Date Dr...Acknowledgments Thanks to all the people who helped to make this research happen. Thanks to my committee: Dr. Michael Havrilla , the late Major Bill Wood...Singularity Expansion Method 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON Michael J. Havrilla , Ph.D. (ENG) a. REPORT U b

  18. A High Voltage High Frequency Resonant Inverter for Supplying DBD Devices with Short Discharge Current Pulses

    OpenAIRE

    Bonnin, Xavier; Brandelero, Julio; Videau, Nicolas; Piquet, Hubert; Meynard, Thierry

    2014-01-01

    International audience; In this paper, the merits of a high-frequency resonant converter for supplying dielectric barrier discharges (DBD) devices are established. It is shown that, thanks to its high-frequency operating condition, such a converter allows to supply DBD devices with short discharge current pulses, a high repetition rate, and to control the injected power. In addition, such a topology eliminates the matter of connecting a high-voltage transformer directly across the DBD device ...

  19. Numerical Modeling of Melting Process of Thin Metal Films Subjected to the Short Laser Pulse

    Directory of Open Access Journals (Sweden)

    E. Majchrzak

    2012-12-01

    Full Text Available Thin metal film subjected to a short-pulse laser heating is considered. The parabolic two-temperature model describing the temporal and spatial evolution of the lattice and electrons temperatures is discussed and the melting process of thin layer is taken into account. At the stage of numerical computations the finite difference method is used. In the final part of the paper the examples of computations are shown.

  20. Computational Design of Short Pulse Laser Driven Iron Opacity Measurements at Stellar-Relevant Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Madison E. [Univ. of Florida, Gainesville, FL (United States)

    2017-05-20

    Opacity is a critical parameter in the simulation of radiation transport in systems such as inertial con nement fusion capsules and stars. The resolution of current disagreements between solar models and helioseismological observations would bene t from experimental validation of theoretical opacity models. Overall, short pulse laser heated iron experiments reaching stellar-relevant conditions have been designed with consideration of minimizing tamper emission and optical depth effects while meeting plasma condition and x-ray emission goals.

  1. Dynamics of atomic spin-orbit-state wave packets produced by short-pulse laser photodetachment

    CERN Document Server

    Law, S M K

    2016-01-01

    We analyse the experiment by Hultgren et al. [Phys. Rev. A {\\bf 87}, 031404 (2013)] on orbital alignment and quantum beats in coherently excited atomic fine-structure manifolds produced by short-pulse laser photodetachment of C$^-$, Si$^-$ and Ge$^-$ negative ions, and derive a formula that describes the beats. Analysis of the experimental data enables us to extract the non-coherent background contribution for each species, and indicates the need for a full density matrix treatment of the problem.

  2. Accurate modeling of antennas for radiating short pulses, FDTD analysis and experimental measurements

    Science.gov (United States)

    Maloney, James G.; Smith, Glenn S.

    1993-01-01

    Antennas used to radiate short pulses often require different design rules that those that are used to radiate essentially time-harmonic signals. The finite-difference time-domain (FDTD) method is a very flexible numerical approach that can be used to treat a variety of electromagnetic problems in the time domain. It is well suited to the analysis and design of antennas for radiating short pulses; however, several advances had to be made before the method could be applied to this problem. In this paper, we will illustrate the use of the FDTD method with two antennas designed for the radiation of short pulses. The first is a simple, two-dimensional geometry, and open-ended parallel-plate waveguide, while the second is a three-dimensional, rotationally symmetric geometry, a conical monopole fed through an image by a coaxial transmission line. Both antennas are 'optimized' according to given criteria by adjusting geometrical parameters and including resistive loading that varies continuously with position along the antenna. The predicted performance for the conical monopole antenna is compared with experimental measurements; this verifies the optimization and demonstrates the practicality of the design.

  3. Short intense ion pulses for materials and warm dense matter research

    CERN Document Server

    Seidl, Peter A; Lidia, Steven M; Persaud, Arun; Stettler, Matthew; Takakuwa, Jeffrey H; Waldron, William L; Schenkel, Thomas; Barnard, John J; Friedman, Alex; Grote, David P; Davidson, Ronald C; Gilson, Erik P; Kaganovich, Igor D

    2015-01-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r < 1 mm within 2 ns FWHM and approximately 10^10 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminium perovskite using the fully integrated accel...

  4. Short intense ion pulses for materials and warm dense matter research

    Science.gov (United States)

    Seidl, Peter A.; Persaud, Arun; Waldron, William L.; Barnard, John J.; Davidson, Ronald C.; Friedman, Alex; Gilson, Erik P.; Greenway, Wayne G.; Grote, David P.; Kaganovich, Igor D.; Lidia, Steven M.; Stettler, Matthew; Takakuwa, Jeffrey H.; Schenkel, Thomas

    2015-11-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

  5. Short intense ion pulses for materials and warm dense matter research

    Energy Technology Data Exchange (ETDEWEB)

    Seidl, Peter A., E-mail: PASeidl@lbl.gov [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Persaud, Arun; Waldron, William L. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Barnard, John J. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Davidson, Ronald C. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Friedman, Alex [Lawrence Livermore National Laboratory, Livermore, CA (United States); Gilson, Erik P. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Greenway, Wayne G. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Grote, David P. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Kaganovich, Igor D. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Lidia, Steven M.; Stettler, Matthew; Takakuwa, Jeffrey H.; Schenkel, Thomas [Lawrence Berkeley National Laboratory, Berkeley, CA (United States)

    2015-11-11

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 10{sup 10} ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li{sup +} ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

  6. Ultra-short laser pulses in dentistry: a solution toward painless dental treatment?

    Science.gov (United States)

    Wieger, V.; Yousif, A.; Strassl, M.; Wintner, E.

    2006-06-01

    Within the last years, modern ultra-short pulse lasers have successfully proven their potential for application in medical tissue treatment in many respects. In dentistry, overheating of the pulp and induction of micro cracks are usually among the most problematic issues which can be solved in this way. An additional benefit can be seen in the possibility of plasma emission spectroscopy as a means of feedback. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the special physiological requirements. Beside the short interaction time with the irradiated biological matter, lateral scanning of ultra-short pulses following optimized algorithms turned out to be crucial for ablating cavities with the required quality and size, a finding which we also believe to be valid for dental restoration materials. Additionally, out of practical reasons, scanning is necessary to treat larger volumes than just the focal spots typically having dimensions on the order of more than 1 mm 3, thereby allowing to realize an "optical drill".

  7. Search for the Giant Pulses Search for the Giant Pulses - an extreme phenomenon in radio pulsar emission

    CERN Document Server

    Kazantsev, A N

    2016-01-01

    Here we present results of our search for Giant Pulses(GPs) from pulsars of Northern Hemisphere. Our survey was carried out at a frequency of 111 MHz using the Large Phased Array (LPA) radio telescope. Up to now we have detected regular generation of strong pulses satisfying the criteria of GPs from 2 pulsars: B1133+16, B1237+25.

  8. Generation of Short X-Ray Pulses Using Crab Cavities at the Advanced Photon Source

    CERN Document Server

    Harkay, Katherine C; Chae, Yong-Chul; Decker, Glenn; Dejus, Roger J; Emery, Louis; Guo, Weiming; Horan, Douglas; Kim, Kwang-Je; Kustom, Robert; Mills, Dennis M; Milton, Stephen; Pile, Geoffery; Sajaev, Vadim; Shastri, Sarvjit D; Waldschmidt, Geoff J; White, Marion; Yang Bing Xin; Zholents, Alexander

    2005-01-01

    There is growing interest within the user community to utilize the pulsed nature of synchrotron radiation from storage ring sources. Conventional third-generation light sources can provide pulses on the order of 100 ps but typically cannot provide pulses of about 1 ps that some users now require to advance their research programs. However, it was recently proposed by A. Zholents et al. to use rf orbit deflection to generate subpicosecond X-ray pulses.* In this scheme, two crab cavities are used to deliver a longitudinally dependent vertical kick to the beam, thus exciting longitudinally correlated vertical motion of the electrons. This makes it possible to spatially separate the radiation coming from different longitudinal parts of the beam. An optical slit can then be used to slice out a short part of the radiation pulse, or an asymetrically cut crystal can be used to compress the radiation in time. In this paper, we present a feasibility study of this method applied to the Advanced Photon Source. We find th...

  9. Spatial evolution of short pulses under conditions of coherent population trapping

    CERN Document Server

    Arkhipkin, V G

    2001-01-01

    We study the features of spatial and temporal evolution of two powerful short different-wavelength laser pulses interacting with optical dense three-level Lambda-type medium under condition of coherent population trapping for the general case of unequal transition oscillator strengths. The pulses are simultaneously sent into an atom. The durations of probe and coupling pulses $T_{1,2}$ ($T_2>T_1$) are supposed to be shorter than all relaxation times in the medium. We present analytical and numerical solutions of the self-consistent set of coupled Schr\\"{o}dinger equations and reduced wave equations in adiabatic limit with taking into account the first non-adiabatic correction. The adiabaticity criterion with account of pulse propagation is studied. We find that propagation dynamics depends on the relationship between the transition oscillator strengths. It is shown that at the initial stage of propagation the envelopes of the pulses slightly change along the length of the medium. This distance can be large co...

  10. Regional trends in short-duration precipitation extremes: a flexible multivariate monotone quantile regression approach

    Science.gov (United States)

    Cannon, Alex

    2017-04-01

    Estimating historical trends in short-duration rainfall extremes at regional and local scales is challenging due to low signal-to-noise ratios and the limited availability of homogenized observational data. In addition to being of scientific interest, trends in rainfall extremes are of practical importance, as their presence calls into question the stationarity assumptions that underpin traditional engineering and infrastructure design practice. Even with these fundamental challenges, increasingly complex questions are being asked about time series of extremes. For instance, users may not only want to know whether or not rainfall extremes have changed over time, they may also want information on the modulation of trends by large-scale climate modes or on the nonstationarity of trends (e.g., identifying hiatus periods or periods of accelerating positive trends). Efforts have thus been devoted to the development and application of more robust and powerful statistical estimators for regional and local scale trends. While a standard nonparametric method like the regional Mann-Kendall test, which tests for the presence of monotonic trends (i.e., strictly non-decreasing or non-increasing changes), makes fewer assumptions than parametric methods and pools information from stations within a region, it is not designed to visualize detected trends, include information from covariates, or answer questions about the rate of change in trends. As a remedy, monotone quantile regression (MQR) has been developed as a nonparametric alternative that can be used to estimate a common monotonic trend in extremes at multiple stations. Quantile regression makes efficient use of data by directly estimating conditional quantiles based on information from all rainfall data in a region, i.e., without having to precompute the sample quantiles. The MQR method is also flexible and can be used to visualize and analyze the nonlinearity of the detected trend. However, it is fundamentally a

  11. New laser glass for short pulsed laser applications: the BLG80 (Conference Presentation)

    Science.gov (United States)

    George, Simi A.

    2017-03-01

    For achieving highest peak powers in a solid state laser (SSL) system, significant energy output and short pulses are necessary. For mode-locked lasers, it is well-known from the Fourier theorem that the largest gain bandwidths produce the narrowest pulse-widths; thus are transform limited. For an inhomogeneously broadened line width of a laser medium, if the intensity of pulses follow a Gaussian function, then the resulting mode-locked pulse will have a Gaussian shape with the emission bandwidth/pulse duration relationship of pulse ≥ 0.44?02/c. Thus, for high peak power SSL systems, laser designers incorporate gain materials capable of broad emission bandwidths. Available energy outputs from a phosphate glass host doped with rare-earth ions are unparalleled. Unfortunately, the emission bandwidths achievable from glass based gain materials are typically many factors smaller when compared to the Ti:Sapphire crystal. In order to overcome this limitation, a hybrid "mixed" laser glass amplifier - OPCPA approach was developed. The Texas petawatt laser that is currently in operation at the University of Texas-Austin and producing high peak powers uses this hybrid architecture. In this mixed-glass laser design, a phosphate and a silicate glass is used in series to achieve a broader bandwidth required before compression. Though proven, this technology is still insufficient for the future compact petawatt and exawatt systems capable of producing high energies and shorter pulse durations. New glasses with bandwidths that are two and three times larger than what is now available from glass hosts is needed if there is to be an alternative to Ti:Sapphire for laser designers. In this paper, we present new materials that may meet the necessary characteristics and demonstrate the laser and emission characteristics these through the internal and external studies.

  12. Spectral and dynamic properties of stimulated electromagnetic emission (SEE) generated by very short diagnostic pulses

    Science.gov (United States)

    Sergeev, Evgeny; Grach, Savely

    Results of the experimental investigations of the HF Upper Hybrid and LF ionospheric tur-bulence by the SEE diagnostic technique over the SURA heating facility are presented. For pumping of the ionosphere an alternation of two basic time modes was used: (1) high duty cycles, i.e. long pulses with a short pauses of 20-30 ms between them, in addition short (diag-nostic) pump pulses with a duration τ ≤ 200 µs were radiated in the middle of the pauses; (2) low-duty cycles consisting of short pulses τ ≤ 200 µs and interpulse period T = 20-200 ms. It is known that the SEE spectral shape and dynamics are determined mainly by the pump-induced UH plasma waves, while the LF turbulence (striations) is responsible for SEE intensity and interpulse dynamics. In previous experiments longer diagnostic pulses (τ 10-30 ms) and interpulse periods (T = 1-3 s) were used. The reduction of τ and T diminishes an influence of the pulses upon tested processes and improves a temporal resolution of the diagnostic SEE measurements. In case of well developed striations (during high duty cycle) diagnostic pulses excite the upper hybrid plasma waves, and, therefore, the SEE with frequencies close to diag-nostic pulse frequency fd practically without time delay. So far as the pulse duration τ was chosen to be much less than a period of their multiple ionospheric reflections (˜ 2 ms) we were able to analyze the decaying SEE spectra just after the ionospherically reflected pulse trailing edge during periods between multiple signal hops in a whole frequency bandwidth including the fd close vicinity. Observations have shown that the SEE spectral maximum is shifted towards lower frequencies from fd by 2-4 kHz during high duty cycle (well-developed striations), and by up to 4-6 kHz after the mode switching to low duty cycle. Then the SEE intensity decreases from pulse to pulse together with striation relaxation. The typical e-folding decay time of the total SEE intensity after the diagnostic

  13. Pulse compression below 40fs at 1μm: The first step towards a short-pulse, high-energy beam line at LULI

    Science.gov (United States)

    Chen, Xiaowei; Zou, Jiping; Martin, Luc; Simon, Francois; Lopez-Martens, Rodrigo; Audebert, Patrick

    2010-08-01

    We present the upgrading project ELFIE (Equipement Laser de Forte Intensité et Energie) based on the "100TW" mixed Nd:glass CPA laser system at 1μm at LULI, which includes an energy enhancement and the development of a short-pulse, high-energy, good temporal contrast beam line (50fs/5J). We report the first experimental step towards the short-pulse, high-energy beam line: spectral broadening above 60nm from 7nm and temporal pulse compression below 40fs from 300fs at 1μm through a Krypton-filled hollow fiber compressor.

  14. High-Order Temporal Corrected Fields of Ultra-Short Laser Pulses and Laser-Driven Acceleration

    Institute of Scientific and Technical Information of China (English)

    XIE Yong-Jie; HUO Yu-Kun; KONG Qing; WANG Ping-Xiao; CHEN Zhao; LIU Jing-Ru

    2006-01-01

    @@ Up to third-order temporal correction in terms of a small dimensionless temporal parameter ε = 1/(ω0t0) (ω0 =ck0 the central oscillatory frequency, t0 the pulse duration of half period), the field expressions of ultra-short focused laser pulses are explicitly presented. To evaluate the correction efficacy, electric amplitudes of zeroth-order and higher-order corrected fields are compared for different pulse durations. Furthermore, electron interaction with ultra-short laser pulses is simulated using both the zeroth-order and higher-order corrected field equations.

  15. Short Wave Amplification and Extreme Runup by the 2011 Tohoku Tsunami

    Science.gov (United States)

    Shimozono, Takenori; Cui, Haiyang; Pietrzak, Julie D.; Fritz, Hermann M.; Okayasu, Akio; Hooper, Andrew J.

    2014-12-01

    Watermarks found during the post-event surveys of the 2011 Tohoku tsunami confirmed extreme runup heights at several locations along the central to northern part of the Sanriku coast, Japan. We measured the maximum height of nearly 40 m above mean sea level at a narrow coastal valley of the Aneyoshi district. Wave records by offshore GPS-buoys suggest that the remarkably high runup was associated with a leading, impulsive crest of the tsunami amplified by local bathymetry and topography. In order to elucidate the underlying amplification mechanism, we apply a numerical model to reproduce the measured distribution of tsunami heights along the target coastline. A series of numerical tests under different boundary conditions suggests that a spectral component with a dominant period of 4-5 min in the leading wave play a key role in generating the extreme runup. Further analyses focusing on the Aneyoshi district confirm that the short wavelength component undergoes critical amplification in a narrow inlet. Our findings highlight the importance of resolving offshore waveforms as well as local bathymetry and topography when simulating extreme runup events.

  16. Generation of time-dependent ultra-short optical pulse trains in the presence of self-steepening effect

    Institute of Scientific and Technical Information of China (English)

    Zhong Xian-Qiong; Xiang An-Ping

    2009-01-01

    Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as timc gocs on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intcnsity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider.

  17. Micro drilling using deformable mirror for beam shaping of ultra-short laser pulses

    Science.gov (United States)

    Smarra, Marco; Strube, Anja; Dickmann, Klaus

    2016-03-01

    Using ultra-short laser pulses for micro structuring or drilling applications reduces the thermal influence to the surrounding material. The best achievable beam profile equals a Gaussian beam. Drilling with this beam profile results in cylindrical holes. To vary the shape of the holes, the beam can either be scanned or - for single pulse and percussion drilling - manipulated by masks or lenses. A high flexible method for beam shaping can be realized by using a deformable mirror. This mirror contains a piezo-electric ceramic, which can be deformed by an electric potential. By separating the ceramic into independent controllable segments, the shape of the surface can be varied individually. Due to the closed surface of the mirror, there is no loss of intensity due to diffraction. The mirror deformation is controlled by Zernike polynomials and results e.g. in a lens behavior. In this study a deformable mirror was used to generate e.g. slits in thin steel foils by percussion drilling using ultra-short laser pulses. The influence of the cylindrical deformation to the laser beam and the resulting geometry of the generated holes was studied. It was demonstrated that due to the high update rate up to 150 Hz the mirror surface can be varied in each scan cycle, which results in a high flexible drilling process.

  18. Third Harmonic Generation of a Short Pulse Laser in a Tunnel Ionizing Plasma: Effect of Self-Defocusing

    Directory of Open Access Journals (Sweden)

    Niti Kant

    2013-08-01

    Full Text Available Third harmonic generation of a Gaussian short pulse laser in a tunnel ionizing plasma is investigated. A Gaussian short pulse laser propagating through a tunnel ionizing plasma generates third harmonic wave. Inhomogeneity of the electric field along the wavefront of the fundamental laser pulse causes more ionization along the axis of propagation while less ionization off axis, leading to strong density gradient with its maximum on the axis of propagation. The medium acts like a diverging lens and pulse defocuses strongly. The normalized third harmonic amplitude varies periodically with the distance with successive maxima acquiring lower value. The self-defocusing of the fundamental laser pulse decays the intensity of the third harmonic pulse.

  19. Short-pulse cross-phase modulation in an electromagnetically-induced-transparency medium

    CERN Document Server

    Feizpour, Amir; Steinberg, Aephraim M

    2016-01-01

    Electromagnetically-induced transparency (EIT) has been proposed as a way to greatly enhance cross-phase modulation, with the possibility of leading to few-photon-level optical nonlinearities. This enhancement grows as the transparency window width, \\Delta_EIT, is narrowed. Decreasing \\Delta_EIT, however, increases the response time of the effect, suggesting that for pulses of a given duration, there could be a fundamental limit to the strength of the nonlinearity. We show that in the regimes of most practical interest - narrow EIT windows perturbed by short signal pulses- the enhancement offered by EIT is not only in the magnitude of the nonlinear phase shift but in fact also in its increased duration. That is, for the case of signal pulses much shorter (temporally) than the inverse EIT bandwidth, the narrow window serves to prolong the effect of the passing signal pulse, leading to an integrated phase shift that grows linearly with \\Delta_EIT even though the peak phase shift may saturate; the continued grow...

  20. Broadband short pulse measurement by autocorrelation with a sum-frequency generation set-up

    Energy Technology Data Exchange (ETDEWEB)

    Glotin, F.; Jaroszynski, D.; Marcouille, O. [LURE, Orsay (France)] [and others

    1995-12-31

    Previous spectral and laser pulse length measurements carried out on the CLIO FEL at wavelength {lambda}=8.5 {mu}m suggested that very short light pulses could be generated, about 500 fs wide (FWHM). For these measurements a Michelson interferometer with a Te crystal, as a non-linear detector, was used as a second order autocorrelation device. More recent measurements in similar conditions have confirmed that the laser pulses observed are indeed single: they are not followed by other pulses distant by the slippage length N{lambda}. As the single micropulse length is likely to depend on the slippage, more measurements at different wavelengths would be useful. This is not directly possible with our actual interferometer set-up, based on a phase-matched non-linear crystal. However, we can use the broadband non-linear medium provided by one of our users` experiments: Sum-Frequency Generation over surfaces. With such autocorrelation set-up, interference fringes are no more visible, but this is largely compensated by the frequency range provided. First tests at 8 {mu}m have already been performed to validate the technic, leading to results similar to those obtained with our previous Michelson set-up.

  1. Short pulse laser-induced optical damage and fracto-emission of amorphous, diamond-like carbon

    Energy Technology Data Exchange (ETDEWEB)

    SOKOLOWSKI-TINTEN,K.; VON DER LINDE,D.; SIEGAL,MICHAEL P.; OVERMYER,DONALD L.

    2000-02-07

    Short pulse laser damage and ablation of amorphous, diamond-like carbon films is investigated. Material removal is due to fracture of the film and ejection of large fragments, which exhibit a broadband emission of microsecond duration.

  2. Generation of 25-TW Femtosecond Laser Pulses at 515 nm with Extremely High Temporal Contrast

    Directory of Open Access Journals (Sweden)

    Marco Hornung

    2015-12-01

    Full Text Available We report on the frequency doubling of femtosecond laser pulses at 1030 nm center wavelength generated from the fully diode-pumped laser system POLARIS. The newly generated pulses at a center wavelength of 515 nm have a pulse energy of 3 J with a pulse duration of 120 fs. On the basis of initially ultra-high contrast seed pulses we expect a temporal intensity contrast better 10 17 200 ps before the peak of the main pulse. We analyzed the temporal intensity contrast from milliseconds to femtoseconds with a dynamic range covering more than 20 orders of magnitude. The pulses were focussed with a f/2-focussing parabola resulting in a peak intensity exceeding 10 20 W / cm 2 . The peak power and intensity are to the best of our knowledge the highest values for 515 nm-laser-pulses achieved so far.

  3. Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

    Energy Technology Data Exchange (ETDEWEB)

    London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Neev, J. [Beckman Laser Inst., Irvine, CA (United States)

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  4. On exact solutions of the Schäfer Wayne short pulse equation: WKI eigenvalue problem

    Science.gov (United States)

    Kamgang Victor, Kuetche; Bouetou Thomas, Bouetou; Crepin Kofane, Timoleon

    2007-05-01

    We consider a new equation recently found by Schäfer and Wayne, hereafter named Schäfer Wayne short pulse equation (SWSPE), describing the propagation of an ultrashort pulse in nonlinear media. Using some vanishing boundary conditions, we construct and discuss the N-soliton solutions to the previous equation by means of the Wadati Konno Ichikawa (WKI) method, which is arguably more direct than the map through the sine-Gordon equation investigated much earlier by Sakovich and Sakovich (2005 J. Phys. Soc. Japan 74 239, 2006 J. Phys. A: Math. Gen. 39 L361). We particularly focus our attention on the two-soliton solution as an application. As a result, the collision process for two-soliton solutions with 'similar' amplitudes exhibits very different behaviour from the case when the amplitudes are 'dissimilar'.

  5. Strong-field Breit-Wheeler pair production in short laser pulses: Relevance of spin effects

    Science.gov (United States)

    Jansen, M. J. A.; Kamiński, J. Z.; Krajewska, K.; Müller, C.

    2016-07-01

    Production of electron-positron pairs in the collision of a high-energy photon with a high-intensity few-cycle laser pulse is studied. By utilizing the frameworks of laser-dressed spinor and scalar quantum electrodynamics, a comparison between the production of pairs of Dirac and Klein-Gordon particles is drawn. Positron energy spectra and angular distributions are presented for various laser parameters. We identify conditions under which predictions from Klein-Gordon theory either closely resemble or largely differ from those of the proper Dirac theory. In particular, we address the question to which extent the relevance of spin effects is influenced by the short duration of the laser pulse.

  6. Strong-field Breit-Wheeler pair production in short laser pulses: Relevance of spin effects

    CERN Document Server

    Jansen, M J A; Krajewska, K; Müller, C

    2016-01-01

    Production of electron-positron pairs in the collision of a high-energy photon with a high-intensity few-cycle laser pulse is studied. By utilizing the frameworks of laser-dressed spinor and scalar quantum electrodynamics, a comparison between the production of pairs of Dirac and Klein-Gordon particles is drawn. Positron energy spectra and angular distributions are presented for various laser parameters. We identify conditions under which predictions from Klein-Gordon theory either closely resemble or largely differ from those of the proper Dirac theory. In particular, we address the question to which extent the relevance of spin effects is influenced by the short duration of the laser pulse.

  7. Deterministic Writing and Control of the Dark Exciton Spin Using Single Short Optical Pulses

    Directory of Open Access Journals (Sweden)

    I. Schwartz

    2015-01-01

    Full Text Available We demonstrate that the quantum dot-confined dark exciton forms a long-lived integer spin solid-state qubit that can be deterministically on-demand initiated in a pure state by one optical pulse. Moreover, we show that this qubit can be fully controlled using short optical pulses, which are several orders of magnitude shorter than the life and coherence times of the qubit. Our demonstrations do not require an externally applied magnetic field, and they establish that the quantum dot-confined dark exciton forms an excellent solid-state matter qubit with some advantages over the half-integer spin qubits, such as the confined electron and hole, separately. Since quantum dots are semiconductor nanostructures that allow integration of electronic and photonic components, the dark exciton may have important implications for implementations of quantum technologies consisting of semiconductor qubits.

  8. Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation

    Directory of Open Access Journals (Sweden)

    Shin Yoshizawa

    2017-03-01

    Full Text Available A target tissue can be thermally coagulated in high-intensity focused ultrasound (HIFU treatment noninvasively. HIFU thermal treatments have been clinically applied to various solid tumors. One of the problems in HIFU treatments is a long treatment time. Acoustically driven microbubbles can accelerate the ultrasonic heating, resulting in the significant reduction of the treatment time. In this paper, a method named “trigger HIFU exposure” which employs cavitation microbubbles is introduced and its results are reviewed. A trigger HIFU sequence consists of high-intensity short pulses followed by moderate-intensity long bursts. Cavitation bubbles induced in a multiple focal regions by rapidly scanning the focus of high-intensity pulses enhanced the temperature increase significantly and produced a large coagulation region with high efficiency.

  9. Ultra-short pulsed laser ablation of silicon nitride layers: Investigation near threshold fluence

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, Gerrit, E-mail: gheinrich@cismst.de [CIS Forschungsinstititut für Mikrosensorik und Photovoltaik GmbH, Konrad-Zuse-Straße 14, Erfurt 99099 (Germany); Technische Universität Ilmenau, Institut für Physik, Weimarer Str. 32, Ilmenau 98693 (Germany); Wollgarten, Markus [Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Bereich Solarenergieforschung, Institut für Technologie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Bähr, Mario; Lawerenz, Alexander [CIS Forschungsinstititut für Mikrosensorik und Photovoltaik GmbH, Konrad-Zuse-Straße 14, Erfurt 99099 (Germany)

    2013-08-01

    In this work, silicon nitride (SiN{sub x}) layers, deposited on a planar silicon wafer are locally irradiated by ultra short laser pulses with fluences near the threshold fluence. The irradiated areas are investigated by SEM and TEM in order to analyze the laser influence to silicon and to the SiN{sub x} layer. Thereby, a lift-off process is observed for this SiN{sub x} layer. The silicon absorbs the laser pulse energy. For low fluences, crystalline silicon is disordered below the SiN{sub x} layer. For high fluences, silicon evaporates below the SiN{sub x} layer and bulge the SiN{sub x} layer. If the pressure within the bulge is high enough, the SiN{sub x} layer will break down due to high mechanical stress.

  10. An imaging proton spectrometer for short-pulse laser plasma experiments

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H; Hazi, A; van Maren, R; Chen, S; Fuchs, J; Gauthier, M; Pape, S L; Rygg, J R; Shepherd, R

    2010-05-11

    Ultra intense short pulse laser pulses incident on solid targets can generate energetic protons. In additions to their potentially important applications such as in cancer treatments and proton fast ignition, these protons are essential to understand the complex physics of intense laser plasma interaction. To better characterize these laser-produced protons, we designed and constructed a novel, spatially imaging proton spectrometer that will not only measure proton energy distribution with high resolution, but also provide its angular characteristics. The information obtained from this spectrometer compliments those from commonly used diagnostics including radiochromic film packs, CR39 nuclear track detectors, and non-imaging magnetic spectrometers. The basic characterizations and sample data from this instrument are presented.

  11. Experimental Research of Fast Proton Generation From Ultra-short Intense Laser Pulses Interaction With Different Thickness Al Foils

    Institute of Scientific and Technical Information of China (English)

    LAN; Xiao-fei; LU; Jian-xin; HUANG; Yong-sheng; WANG; Lei-jian; XI; Xiao-feng; TANG; Xiu-zhang

    2012-01-01

    <正>With the development of laser technology, the generation of fast ions by the interaction of ultra-short ultra-intense laser pulses with matters has recently been attracting considerable attention, especially for acceleration of proton. Before performing experiment, we calibrated the CR39 detector using standard proton beams from conventional accelerator. In the field of proton acceleration driven by ultra-short ultra-intense laser pulses,

  12. Closed gastroschisis, vanishing midgut and extreme short bowel syndrome: Case report and review of the literature.

    Science.gov (United States)

    Dennison, F A

    2016-08-01

    Gastroschisis alone has excellent survival rates. Occasionally reported is closed gastroschisis, leading to vanishing small bowel and extreme short bowel syndrome. It is believed that the abdominal wall defect can contract or close in utero, which leads to strangulation of the eviscerated bowel and the rare "vanishing gut syndrome." This has a very poor prognosis with mortality as high as 70%. An 18-year-old primigravid patient's 13 week scan diagnosed a large gastroschisis affecting the fetus. After counselling, she decided to continue with the pregnancy. Between 20 and 22 weeks, the gastroschisis disappeared, and the bowel within the abdomen became markedly dilated. Spontaneous labour occurred at 33 + 3 weeks gestation. There was no abdominal wall defect seen at delivery. Imaging and an exploratory laparotomy demonstrated absence of most of the midgut. Because available options for treatment would be very aggressive and risky, palliative care was thought to be the most feasible and practical option. He died at home on day 29 after birth. Extreme short gut syndrome (less than 25 cm of remaining small bowel) is rare. There are 13 reported cases in the literature from year 2000 to 2013. Treatment is aggressive and involves a bowel lengthening procedure or small bowel transplant. All require total parenteral nutrition and liver failure, and liver transplant is a common complication. Of these cases, 12 were born alive and 7 had aggressive treatment. Only two cases were confirmed to still be alive in infancy. If gastroschisis is seen to be reducing and "disappearing" antenatally, parents should be made aware of this rare complication so that they might be prepared if a poor outcome is anticipated.

  13. Short time step continuous rainfall modeling and simulation of extreme events

    Science.gov (United States)

    Callau Poduje, A. C.; Haberlandt, U.

    2017-09-01

    The design, planning, operation and overall assessment of urban drainage systems require long and continuous rain series in a high temporal resolution. Unfortunately, the availability of this data is usually short. Nevertheless a precipitation model could be used to tackle this shortcoming; therefore it is in the aim of this study to present a stochastic point precipitation model to reproduce average rainfall event properties along with extreme values. For this purpose a model is proposed to generate long synthetic series of rainfall for a temporal resolution of 5 min. It is based on an alternating renewal framework and events are characterized by variables describing durations, amounts and peaks. A group of 24 stations located in the north of Germany is used to set up and test the model. The adequate modeling of joint behaviour of rainfall amount and duration is found to be essential for reproducing the observed properties, especially for the extreme events. Copulas are advantageous tools for modeling these variables jointly; however caution must be taken in the selection of the proper copula. The inclusion of seasonality and small events is as well tested and found to be useful. The model is directly validated by generating long synthetic time series and comparing them with observed ones. An indirect validation is as well performed based on a fictional urban hydrological system. The proposed model is capable of reproducing seasonal behaviour and main characteristics of the rainfall events including extremes along with urban flooding and overflow behaviour. Overall the performance of the model is acceptable compared to the design practice. The proposed model is simple to interpret, fast to implement and to transfer to other regions, whilst showing acceptable results.

  14. Interaction of ultrashort laser pulses and silicon solar cells under short circuit conditions

    Science.gov (United States)

    Mundus, M.; Giesecke, J. A.; Fischer, P.; Hohl-Ebinger, J.; Warta, W.

    2015-02-01

    Ultrashort pulse lasers are promising tools for numerous measurement purposes. Among other benefits their high peak powers allow for efficient generation of wavelengths in broad spectral ranges and at spectral powers that are orders of magnitude higher than in conventional light sources. Very recently this has been exploited for the establishment of sophisticated measurement facilities for electrical characterization of photovoltaic (PV) devices. As the high peak powers of ultrashort pulses promote nonlinear optical effects they might also give rise to nonlinear interactions with the devices under test that possibly manipulate the measurement outcome. In this paper, we present a comprehensive theoretical and experimental study of the nonlinearities affecting short circuit current (ISC) measurements of silicon (Si) solar cells. We derive a set of coupled differential equations describing the radiation-device interaction and discuss the nonlinearities incorporated in those. By a semi-analytical approach introducing a quasi-steady-state approximation and integrating a Green's function we solve the system of equations and obtain simulated ISC values. We validate the theoretical model by ISC ratios obtained from a double ring resonator setup capable for reproducible generation of various ultrashort pulse trains. Finally, we apply the model to conduct the most prominent comparison of ISC generated by ultrashort pulses versus continuous illumination. We conclude by the important finding that the nonlinearities induced by ultrashort pulses are negligible for the most common ISC measurements. However, we also find that more specialized measurements (e.g., of concentrating PV or Si-multijunction devices as well as highly localized electrical characterizations) will be biased by two-photon-absorption distorting the ISC measurement.

  15. Ion acceleration in shell cylinders irradiated by a short intense laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A. [Max-Born Institute, Berlin (Germany); ELI-ALPS, Szeged (Hungary); Platonov, K. [St. Petersburg State Polytechnic University, St. Petersburg (Russian Federation); Sharma, A. [ELI-ALPS, Szeged (Hungary); Murakami, M. [ILE, Osaka University, Osaka (Japan)

    2015-09-15

    The interaction of a short high intensity laser pulse with homo and heterogeneous shell cylinders has been analyzed using particle-in-cell simulations and analytical modeling. We show that the shell cylinder is proficient of accelerating and focusing ions in a narrow region. In the case of shell cylinder, the ion energy exceeds the ion energy for a flat target of the same thickness. The constructed model enables the evaluation of the ion energy and the number of ions in the focusing region.

  16. Time-resolved diffraction profiles and structural dynamics of Ni film under short laser pulse irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Zhibin; Zhigilei, Leonid V [University of Virginia, Department of Materials Science and Engineering, 116 Engineer' s Way, Charlottesville, VA 22904-4745 (United States)

    2007-04-15

    The evolution of the diffraction profiles during the fast thermoelastic deformation and structural transformations induced in a thin Ni film by short pulse laser irradiation is investigated in molecular dynamics simulations. Fast disappearance of the diffraction peaks characteristic for the initial crystal structure is related to the homogeneous nucleation and growth of liquid regions inside the overheated crystal. Transient thermoelastic deformation of the film prior to melting is reflected in shifts and splittings of the diffraction peaks, providing an opportunity for experimental probing of the ultrafast deformations.

  17. Partial Shading Detection in Solar System Using Single Short Pulse of Load

    Directory of Open Access Journals (Sweden)

    Bartczak Mateusz

    2017-03-01

    Full Text Available A single photovoltaic panel under uniform illumination has only one global maximum power point, but the same panel in irregularly illuminated conditions can have more maxima on its power-voltage curve. The irregularly illuminated conditions in most cases are results of partial shading. In the work a single short pulse of load is used to extract information about partial shading. This information can be useful and can help to make some improvements in existing MPPT algorithms. In the paper the intrinsic capacitance of a photovoltaic system is used to retrieve occurrence of partial shading.

  18. Determination of the carrier envelope phase for short, circularly polarized laser pulses

    CERN Document Server

    Titov, Alexander I; Hosaka, Atsushi; Nousch, Tobias; Seipt, Daniel

    2015-01-01

    We analyze the impact of the carrier envelope phase on the differential cross sections of the Breit-Wheeler and the generalized Compton scattering in the interaction of a charged electron (positron) with an intensive ultra-short electromagnetic (laser) pulse. The differential cross sections as a function of the azimuthal angle of the outgoing electron have a clear bump structure, where the bump position coincides with the value of the carrier phase. This effect can be used for the carrier envelope phase determination.

  19. Experimental and Analytical Investigation of Cemented Tungsten Carbide Ultra-Short Pulse Laser Ablation

    Science.gov (United States)

    Urbina, J. P. Calderón; Daniel, C.; Emmelmann, C.

    Ultra-short pulse laser processing of hard materials, such as cemented tungsten carbide, requires an accurate and agile experimental and analytical investigation to obtain adequate information and setting parameters to maximize ablation rate. Therefore, this study presents a systematic approach which, first, experimentally searches for the variables with the most significant influence on the objective using a design of experiments method; and second, analyzes by means of existing ablation theory the interaction of the material and laser taking into account the Beer-Lambert law and incubation effect.Therefore, this places a basis for future analytical-experimental validation of the examined material.

  20. Study of rapid transient explosive boiling under short-pulsed laser heating

    Institute of Scientific and Technical Information of China (English)

    JIN Renxi; HUAI Xiulan; LIU Dengying

    2004-01-01

    Using acetone, ethanol, water and acetone-water mixture as test liquids, the rapid transient explosive boiling (RTEB) taking place under short-pulsed laser heating is observed in experiment. The behaviors of temperature variation are investigated via transient temperature measurement. The vapor bubble behaviors of RTEB are captured by high-speed photography, and the difference between RTEB and normal boiling is analyzed. The boiling heat transfer of RTEB is also discussed. It shows that the character of RTEB is far different from normal boiling.

  1. Transference & Retrieval of Pulse-code modulation Audio over Short Messaging Service

    CERN Document Server

    Khan, Muhammad Fahad

    2012-01-01

    The paper presents the method of transferring PCM (Pulse-Code Modulation) based audio messages through SMS (Short Message Service) over GSM (Global System for Mobile Communications) network. As SMS is text based service, and could not send voice. Our method enables voice transferring through SMS, by converting PCM audio into characters. Than Huffman coding compression technique is applied in order to reduce numbers of characters which will latterly set as payload text of SMS. Testing the said method we develop an application using J2me platform

  2. Analyses of the short pulse laser pumped transient collisional excited X-ray lasers

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, A.; Utsumi, T.; Moribayashi, K.; Zhidkov, A.; Kado, M.; Tanaka, M.; Hasegawa, N.; Kawachi, T. [Japan Atomic Energy Research Inst., Osaka (Japan). Advanced Photon Research Center

    2001-07-01

    The soft X-ray gain of the transient collisional excited (TCE) Ni-like Ag laser is investigated using the plasma hydrodynamics and atomic kinetics codes. The gain is calculated for a plasma produced from two 100ps laser irradiated solid target to show qualitative agreement with the experiment. The calculation shows significant improvement of the gain using a thin foil target pumped by two short laser pulses, because of a better coupling of the pump laser energy into the gain region of the plasma. The codes will provide performance prediction as well as optimization of the experimental studies of the TCE X-ray lasers. (orig.)

  3. Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

    Science.gov (United States)

    Bauer, Franziska; Michalowski, Andreas; Kiedrowski, Thomas; Nolte, Stefan

    2015-01-26

    High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

  4. The RMT method for describing many-electron atoms in intense short laser pulses

    Science.gov (United States)

    Lysaght, M. A.; Moore, L. R.; Nikolopoulos, L. A. A.; Parker, J. S.; van der Hart, H. W.; Taylor, K. T.

    2012-11-01

    We describe how we have developed an ab initio R-Matrix incorporating Time (RMT) method to provide an accurate description of the single ionization of a general many-electron atom exposed to short intense laser pulses. The new method implements the "division-of-space" concept central to R-matrix theory and takes over the sophisticated time-propagation algorithms of the HELIUM code. We have tested the accuracy of the new method by calculating multiphoton ionization rates of He and Ne and have found excellent agreement with other highly accurate and well-established methods.

  5. Short-pulse generation in a diode-end-pumped solid-state laser

    CSIR Research Space (South Africa)

    Ngcobo, S

    2010-09-01

    Full Text Available in the picosecond region with a maximum average output power of 2.8W. Passive modelocking of the Nd:YVO4 laser has been demonstrated using a semiconductor saturable absorber mirror (SESAM). THEORETICAL ANALYSIS Ultra-fast solid state lasers are a key component... theoretical PQSML,th of 2.08W. Short-Pulse Generation in a Diode-End-Pumped Solid-State Laser S. Ngcobo1,2, C. Bollig1 and H. Von Bergmann2 1CSIR National Laser Centre, PO Box 395, Pretoria, 0001, South Africa 2Laser Research Center, University...

  6. Assessing the short-term effects of an extreme storm on Mediterranean forest raptors

    Science.gov (United States)

    Martínez, José E.; Jiménez-Franco, María V.; Zuberogoitia, Iñigo; León-Ortega, Mario; Calvo, José F.

    2013-04-01

    Different species show different responses to natural disturbances, depending on their capacity to exploit the altered environment and occupy new niches. In the case of semi-arid Mediterranean areas, there is no information available on the response of bird communities to disturbance caused by extreme weather events. Here, we evaluate the short-term effects of a heavy snowfall and strong winds on three long-lived species of forest-dwelling raptor in a semi-arid Mediterranean region situated in the south-east of Spain. The loss of nests was significantly higher in the first and second years following the disturbance than in the third year. The three species studied exhibited great tolerance to the short-term effects of the storm since we found no differences in density or reproductive parameters between the nine breeding seasons prior to the disturbance and the three which immediately followed it. We suggest that the tolerance shown by these three species to windstorms in semi-arid Mediterranean zones could be an adaptive response, resulting from the climatic and human pressures which have prevailed from the Bronze Age to the present day.

  7. Short-pulsed laser transport in two-dimensional scattering media by natural element method.

    Science.gov (United States)

    Zhang, Yong; Yi, Hong-Liang; Xie, Ming; Tan, He-Ping

    2014-04-01

    The natural element method (NEM) is extended to solve transient radiative transfer (TRT) in two-dimensional semitransparent media subjected to a collimated short laser irradiation. The least-squares (LS) weighted residuals approach is employed to spatially discretize the transient radiative heat transfer equation. First, for the case of the refractive index matched boundary, LSNEM solutions to TRT are validated by comparison with results reported in the literature. Effects of the incident angle on time-resolved signals of transmittance and reflectance are investigated. Afterward, the accuracy of this algorithm for the case of the refractive index mismatched boundary is studied. Finally, the LSNEM is extended to study the TRT in a two-dimensional semitransparent medium with refractive index discontinuity irradiated by the short pulse laser. The effects of scattering albedo, optical thickness, scattering phase function, and refractive index on transmittance and reflectance signals are investigated. Several interesting trends on the time-resolved signals are observed and analyzed.

  8. Human dermis separation via ultra-short pulsed laser plasma-mediated ablation

    Energy Technology Data Exchange (ETDEWEB)

    Huang Huan; Guo Zhixiong, E-mail: guo@jove.rutgers.ed [Department of Mechanical and Aerospace Engineering, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States)

    2009-08-21

    In vitro layer separation of human dermal tissues via laser plasma-mediated ablation was successfully conducted for the first time. The ablation of wet dermis was generated using a 900 fs ultra-short pulsed laser with the wavelength centred at 1552 nm. The ablation and separation results were imaged and measured by scanning electron microscopy. The dermis ablation threshold was determined as 9.65 {+-} 1.21 J cm{sup -2} and the incubation factor was found as 0.46 {+-} 0.03. Histological examinations were performed to find proper laser parameters for dermis ablation and separation with minimal thermal damage. No thermal damage was found in the single line ablation results when the pulse overlap rate was not over 5 pulses {mu}m{sup -1}. Even in the multi-line ablation, thermal damage was insignificant and the lateral damage zone was generally within 5 {mu}m in the results with 100 continuously repeated line scans. The separation of a whole piece of wet dermal tissue into two thin layers was presented. Several separation tests with different layer thicknesses from 200 to 600 {mu}m were completed. The unevenness of the separated layers was generally under 10%. The cohesion and morphology of the separated tissue layers were not altered.

  9. Development and Applications of discharges generated in liquids with short high voltage pulses

    Science.gov (United States)

    Kolb, Juergen; Miron, Camelia; Kruth, Angela; Balcerak, Michal; Bonislawski, Michal; Holub, Marcin

    2016-09-01

    Discharges that are generated within a liquid have been of scientific interest for more than a century. The possibility for a breakdown development that is not mediated by an initial gaseous phase is still disputed. In this respect are especially discharges that are instigated with short high voltage pulses calling for attention. Associated with this specific excitation scheme is a change in plasma development, plasma parameters and reaction mechanisms in the liquid. We have compared discharges in a point-to-plane geometry that were generated with 50-us or 10-ns high voltage pulses. Time-resolved shadowgraphy and spectroscopy were performed to evaluate discharge structures, plasma parameter and reactive species that were formed in distilled water or ethanol. Different propagation modes, with velocities of 6.7 km/s for tree-like streamers and only 50 m/s for bush-like streamers, were observed. Optical emission spectroscopy has shown the formation of molecular bands of nitrogen, as well as strongly broadened atomic hydrogen and oxygen, which are likely to be responsible for the observed surface modifications of polymers. With nanosecond high voltage pulses we found an increase of unsaturated bondings for polyimide surfaces that were exposed in the discharge volume.

  10. Study on Ultra-Short Laser Pulse Ablation of Metals by Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    LIU Xuan; WANG Yang; ZHAO Li-jie

    2006-01-01

    The dynamical progresses involved in ultra-short laser pulse ablation of face-centered cubic metals under stress confinement condition are described completely using molecular dynamics method. The laser beam absorption and thermal energy turning into kinetics energy of atoms are taken into account to give a detailed picture of laser metal interaction. Superheating phenomenon is observed, and the phase change from solid to liquid is characterized by a destroyed atom configuration and a decreased number density. The steep velocity gradients are found in the systems of Cu and Ni after pulse in consequence of located heating and exponential decrease of fluences following the Lambert-Beer expression. The shock wave velocities are predicted to be about 5000m/s in Cu and 7200m/s in Ni. The higher ablation rates are obtained from simulations compared with experimental data as a result of a well-defined crystalline surface irradiated by a single pulse. Simulation results show that the main mechanisms of ablation are evaporation and thermoelastic stress due to located heating.

  11. Design of the plasma grid for a short pulse negative ion source experimental setup at HUST

    Science.gov (United States)

    Zuo, C.; Li, D.; Chen, D.; Zhao, P.; Xu, Q.; Liao, Z.

    2017-08-01

    An experimental setup of a radio frequency (RF) driven negative hydrogen ion source has been developed at Huazhong University of Science and Technology (HUST). The setup without cesium oven and an extraction system had been completed and the plasma was ignited in the driver successfully in 2014. An extraction system with small area (5540 mm2) for short pulse (˜ 4 s) was designed to extract the negative hydrogen ions. Generally, the plasma grid temperature is controlled to reach 150 °C by the cooling channels inside the grid. But another method that we could use the PG current to raise the temperature is being considered only for the short pulse condition. An experiment was introduced to prove the feasibility of this method. A magnetic field produced by current flowing through the plasma grid is required to reduce the electron temperature and suppress the co-extraction electrons. The filter field homogeneity has been studied in detail by finite element method. There have been significant improvements regarding the field homogeneity by means of the grid geometry optimization.

  12. The unsteady regime of intense short-pulse under-dens plasma interactions

    CERN Document Server

    Yazdanpanah, Jam; Chakhmachi, Amir; Khalilzadeh, Elnaz

    2015-01-01

    We have performed a detailed study on the interaction of ultra-intense, short laser pulse with under-dens plasma. The underlying interaction physics is outlined and key topics like laser absorption and electron acceleration are addressed. This study is assisted by the extensive 1D3V particle-in-cell (PIC) simulations over a wide range of initial plasma densities, , ( is the critical density) and laser intensities, . It is noticed that the steady propagation of a short-pulse through a low density plasma is violated in proportion to the expression ( and are electron density laser gamma factor). Accordingly, when the plasma density rises toward the critical value, a new physical regime appears which has not been adequately explored, previously. Using general conservation laws it is demonstrated that due to the radiation pressure, strong wave-breaking (phase mixing) occurs in this regime. The electron acceleration is described in terms of the wave-breaking followed by the direct laser acceleration (DLA). A new ph...

  13. Channels of energy redistribution in short-pulse laser interactions with metal targets

    Science.gov (United States)

    Zhigilei, Leonid V.; Ivanov, Dmitriy S.

    2005-07-01

    The kinetics and channels of laser energy redistribution in a target irradiated by a short, 1 ps, laser pulse is investigated in computer simulations performed with a model that combines molecular dynamics (MD) simulations with a continuum description of the laser excitation and relaxation of the conduction band electrons, based on the two-temperature model (TTM). The energy transferred from the excited electrons to the lattice splits into several parts, namely the energy of the thermal motion of the atoms, the energy of collective atomic motions associated with the relaxation of laser-induced stresses, the energy carried away from the surface region of the target by a stress wave, the energy of quasi-static anisotropic stresses, and, at laser fluences above the melting threshold, the energy transferred to the latent heat of melting and then released upon recrystallization. The presence of the non-thermal channels of energy redistribution (stress wave and quasi-static stresses), not accounted for in the conventional TTM model, can have important implications for interpretation of experimental results on the kinetics of thermal and mechanical relaxation of a target irradiated by a short laser pulse as well as on the characteristics of laser-induced phase transformations. The fraction of the non-thermal energy in the total laser energy partitioning increases with increasing laser fluence.

  14. Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

    Energy Technology Data Exchange (ETDEWEB)

    Giri, Ashutosh; Hopkins, Patrick E., E-mail: phopkins@virginia.edu [Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2015-12-07

    Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.

  15. Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

    Science.gov (United States)

    Giri, Ashutosh; Hopkins, Patrick E.

    2015-12-01

    Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.

  16. BFG composite pulses: a simple family of NOT gates with extreme tolerance of errors

    CERN Document Server

    Jones, Jonathan A

    2012-01-01

    Composite pulses, originally developed in Nuclear Magnetic Resonance, have found widespread use in experimental quantum information processing to reduce the effects of systematic errors. Here I describe how ideas from the Fn, Gn and BB1 families of composite pulses can be used to derive simple implementations of not gates with unprecedented tolerance of pulse strength errors without unreasonable sensitivity to other errors such as off-resonance errors and phase angle errors.

  17. Reflectivity of plasmas created by high-intensity, ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Gold, D.M.

    1994-06-01

    Experiments were performed to characterize the creation and evolution of high-temperature (T{sub e}{approximately}100eV), high-density (n{sub e}>10{sup 22}cm{sup {minus}3}) plasmas created with intense ({approximately}10{sup 12}-10{sup 16}W/cm{sup 2}), ultra-short (130fs) laser pulses. The principle diagnostic was plasma reflectivity at optical wavelengths (614nm). An array of target materials (Al, Au, Si, SiO{sub 2}) with widely differing electronic properties tested plasma behavior over a large set of initial states. Time-integrated plasma reflectivity was measured as a function of laser intensity. Space- and time-resolved reflectivity, transmission and scatter were measured with a spatial resolution of {approximately}3{mu}m and a temporal resolution of 130fs. An amplified, mode-locked dye laser system was designed to produce {approximately}3.5mJ, {approximately}130fs laser pulses to create and nonintrusively probe the plasmas. Laser prepulse was carefully controlled to suppress preionization and give unambiguous, high-density plasma results. In metals (Al and Au), it is shown analytically that linear and nonlinear inverse Bremsstrahlung absorption, resonance absorption, and vacuum heating explain time-integrated reflectivity at intensities near 10{sup 16}W/cm{sup 2}. In the insulator, SiO{sub 2}, a non-equilibrium plasma reflectivity model using tunneling ionization, Helmholtz equations, and Drude conductivity agrees with time-integrated reflectivity measurements. Moreover, a comparison of ionization and Saha equilibration rates shows that plasma formed by intense, ultra-short pulses can exist with a transient, non-equilibrium distribution of ionization states. All targets are shown to approach a common reflectivity at intensities {approximately}10{sup 16}W/cm{sup 2}, indicating a material-independent state insensitive to atomic or solid-state details.

  18. Estimating return periods of extreme values from relatively short time series of winds

    Science.gov (United States)

    Jonasson, Kristjan; Agustsson, Halfdan; Rognvaldsson, Olafur; Arfeuille, Gilles

    2013-04-01

    An important factor for determining the prospect of individual wind farm sites is the frequency of extreme winds at hub height. Here, extreme winds are defined as the value of the highest 10 minutes averaged wind speed with a 50 year return period, i.e. annual exceeding probability of 2% (Rodrigo, 2010). A frequently applied method to estimate winds in the lowest few hundred meters above ground is to extrapolate observed 10-meter winds logarithmically to higher altitudes. Recent study by Drechsel et al. (2012) showed however that this methodology is not as accurate as interpolating simulated results from the global ECMWF numerical weather prediction (NWP) model to the desired height. Observations of persistent low level jets near Colima in SW-Mexico also show that the logarithmic approach can give highly inaccurate results for some regions (Arfeuille et al., 2012). To address these shortcomings of limited, and/or poorly representative, observations and extrapolations of winds one can use NWP models to dynamically scale down relatively coarse resolution atmospheric analysis. In the case of limited computing resources one has typically to make a compromise between spatial resolution and the duration of the simulated period, both of which can limit the quality of the wind farm siting. A common method to estimate maximum winds is to fit an extreme value distribution (e.g. Gumbel, gev or Pareto) to the maximum values of each year of available data, or the tail of these values. If data are only available for a short period, e.g. 10 or 15 years, then this will give a rather inaccurate estimate. It is possible to deal with this problem by utilizing monthly or weekly maxima, but this introduces new problems: seasonal variation, autocorrelation of neighboring values, and increased discrepancy between data and fitted distribution. We introduce a new method to estimate return periods of extreme values of winds at hub height from relatively short time series of winds, simulated

  19. Short- and Long-term Pulmonary Outcome of Palivizumab in Children Born Extremely Prematurely.

    Science.gov (United States)

    Prais, Dario; Kaplan, Eytan; Klinger, Gil; Mussaffi, Huda; Mei-Zahav, Meir; Bar-Yishay, Ephraim; Stafler, Patrick; Steuer, Guy; Sirota, Lea; Blau, Hannah

    2016-03-01

    Palivizumab reduces the severity of respiratory syncytial virus infection in premature infants, but whether there is a protective effect beyond the preschool age is unknown. This study sought to assess the short- and long-term effects of palivizumab immunization on respiratory morbidity and pulmonary function at school age in children born extremely prematurely. Infants born before 29 weeks' gestation in 2000 to 2003 were assessed at school age by parental questionnaire, hospital chart review, and lung function tests. Children born immediately before the introduction of routine palivizumab prophylaxis were compared with age-matched children who received palivizumab prophylaxis during the first respiratory syncytial virus season. Sixty-three children with a mean age 8.9 years were included: 30 had received palivizumab and 33 had not (control subjects). The groups were similar in terms of gestational age, birth weight, need for mechanical ventilation, and oxygen supplementation. Fifty-three percent of the palivizumab group, compared with 39% of the control group, had bronchopulmonary dysplasia (P = .14). Wheezing occurred in the first 2 years of life in 27% of the palivizumab group and in 70% of control subjects (P = .008); respective hospitalization rates were 33% and 70% (P = .001). At school age, rates of hyperresponsiveness (provocative concentration leading to a 20% fall in FEV1 < 1 mg/mL) were 33% and 48%, respectively (P = .38). Spirometry, lung volumes, diffusion, and exhaled nitric oxide were within normal limits, with no significant differences between groups. Palivizumab prophylaxis was associated with reduced wheezing episodes and hospitalizations during the first 2 years of life in children born extremely prematurely. However, it did not affect pulmonary outcome at school age. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

  20. Chronic calcium pyrophosphate crystal inflammatory arthritis induced by extreme hypomagnesemia in short bowel syndrome

    Directory of Open Access Journals (Sweden)

    Hahn Markus

    2012-09-01

    Full Text Available Abstract Background Short bowel syndrome (SBS may induce a plethora of clinical symptoms ranging from underweight to nutrient-, vitamin- and electrolyte deficiencies. The objective of this case report is to illustrate how demanding the management of a 60 year old patient with SBS and recurrent joint attacks was for different medical disciplines. Case presentation The patient with SBS presented with a body mass index of 16.5 kg/m2 after partial jejunoileal resection of the small intestine with a six year long history of recurrent pain attacks in multiple peripheral joints, chronic diarrhoea and food intolerances. Pain attacks occurred 4–5 times a week with a median consumption of 15 mg prednisone per day. The interdisciplinary workup after several gastroenterologic, rheumatologic, radiologic, psychiatric and orthopedic consultations is shown including successful treatment steps. Clinical diagnosis revealed no systemic inflammatory disease, but confirmed extreme hypomagnesemia (0.2 mmol/l after reproducible pathological magnesium resorption tests as causative for chronic calcium pyrophosphate crystal inflammatory arthritis (pseudogout, chondrocalcinosis. Multidisciplinary treatment included application of colchicines, parenteral nutrition and magnesium substitution, antiperistaltic agents and avoidance of intolerant foods. Normalization of magnesium levels and a marked remission of joint attacks were achieved after six months with significant reduction of prednisone to 1.5 mg/day. Conclusion Despite the rarity of this condition, it is important to know that hypomagnesaemia may be associated with calcium pyrophosphate crystal inflammatory arthritis (chondrocalcinosis and that SBS patients may be prone to develop extreme hypomagnesaemia causing recurrent joint attacks without systemic inflammation.

  1. HATS-18 b: An Extreme Short--Period Massive Transiting Planet Spinning Up Its Star

    CERN Document Server

    Penev, Dr Kaloyan M; Bakos, Dr Gaspar A; Ciceri, Ms Simona; Brahm, Dr Rafael; Bayliss, Dr Daniel; Bento, Joao; Jord'an, Andr'es; Csubry, Mr Zoltan; Bhatti, W; de Val-Borro, Miguel; Espinoza, Mr Néstor; Zhou, Dr George; Mancini, Dr Luigi; Rabus, Dr Markus; Suc, Vincent; Henning, Thomas; Schmidt, Prof Brian P; Noyes, Dr Robert W; L'az'ar, J; Papp, Istvan; S'ari, P

    2016-01-01

    We report the discovery by the HATSouth network of HATS-18 b: a 1.980 +/- 0.077 Mj, 1.337 +0.102 -0.049 Rj planet in a 0.8378 day orbit, around a solar analog star (mass 1.037 +/- 0.047 Msun, and radius 1.020 +0.057 -0.031 Rsun) with V=14.067 +/- 0.040 mag. The high planet mass, combined with its short orbital period, implies strong tidal coupling between the planetary orbit and the star. In fact, given its inferred age, HATS-18 shows evidence of significant tidal spin up, which together with WASP-19 (a very similar system) allows us to constrain the tidal quality factor for Sun-like stars to be in the range 6.5 <= lg(Q*/k_2) <= 7 even after allowing for extremely pessimistic model uncertainties. In addition, the HATS-18 system is among the best systems (and often the best system) for testing a multitude of star--planet interactions, be they gravitational, magnetic or radiative, as well as planet formation and migration theories.

  2. A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    NARCIS (Netherlands)

    Irimia, D.; Dobrikov, D.; Kortekaas, R.; Voet, H.; Ende, D.A. van den; Groen, W.A.; Janssen, M.H.M.

    2009-01-01

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms t

  3. Local short-duration precipitation extremes in Sweden: observations, forecasts and projections

    Science.gov (United States)

    Olsson, Jonas; Berg, Peter; Simonsson, Lennart

    2015-04-01

    Local short-duration precipitation extremes (LSPEs) are a key driver of hydrological hazards, notably in steep catchments with thin soils and in urban environments. The triggered floodings, landslides, etc., have large consequences for society in terms of both economy and health. Accurate estimations of LSPEs on both climatological time-scales (past, present, future) and in real-time is thus of great importance for improved hydrological predictions as well as design of constructions and infrastructure affected by hydrological fluxes. Analysis of LSPEs is, however, associated with various limitations and uncertainties. These are to a large degree associated with the small-scale nature of the meteorological processes behind LSPEs and the associated requirements on observation sensors as well as model descriptions. Some examples of causes for the limitations involved are given in the following. - Observations: High-resolution data sets available for LSPE analyses are often limited to either relatively long series from one or a few stations or relatively short series from larger station networks. Radar data have excellent resolutions in both time and space but the estimated local precipitation intensity is still highly uncertain. New and promising techniques (e.g. microwave links) are still in their infancy. - Weather forecasts (short-range): Although forecasts with the required spatial resolution for potential generation of LSPEs (around 2-4 km) are becoming operationally available, the actual forecast precision of LSPEs is largely unknown. Forecasted LSPEs may be displaced in time or, more critically, in space which strongly affects the possibility to assess hydrological risk. - Climate projections: The spatial resolution of the current RCM generation (around 25 km) is not sufficient for proper description of LSPEs. Statistical post-processing (i.e. downscaling) is required which adds substantial uncertainty to the final result. Ensemble generation of sufficiently

  4. Experimental study regarding the effects of pulsed short waves on nervous tissue

    Directory of Open Access Journals (Sweden)

    DOGARU Gabriela

    2014-05-01

    Full Text Available Pulsed short waves are part of high frequency therapy and have through their biological effects, the good therapeutic results and the lack of side effects many indications in various disorders: rheumatologic, traumatologic, burns, neurological (nerve tissue regeneration, ischemic vascular accidents, vascular disorders. The experimental study consisted of the exposure of laboratory animals to the action of pulsed short waves in different doses and the monitoring of changes in the brain cellular and subcellular structure. The study included 35 Wistar rats, assigned to four groups, three groups of 10 animals and the control group of five non-irradiated animals. Group I was exposed to a dose of 1/80 cycles/sec, group II to 4/400 cycles/sec, and group III to 6/600 cycles/sec, for 10 minutes/day, for 15 days. After the rats were sacrificed, nervous tissue fragments were collected. These were adequately processed for their examination by optical and electron microscopy. At structural level, in the control group and the groups exposed to the dose of 1/80 cycles/sec, the neurons were normally structured. In group II, a slight increase of brain metabolic activity was seen, in group III there was a significant increase of brain metabolism, with better myelinated white matter axons, which suggests a better protection for the rapid conduction of nerve impulses to effectors. In group II, electron microscopy revealed similar aspects to those of the control group. A high ribosome density was found in the neuroplasm, which means an intense protein synthesis process. In group III, there was an intense protein synthesis activity, and a strong axon myelination in the white matter, resulting in a better protection for the transmission of nerve impulses. Conclusions: pulsed short waves caused brain changes depending on the dose. The analysis of electron microscopic images showed that irradiation at a dose of 6/600 cycles/sec induced an intense protein synthesis

  5. The First Pulse of the Extremely Bright GRB 130427A: A Test Lab for Synchrotron Shocks

    Science.gov (United States)

    Preece, R.; Burgess, J. Michael; von Kienlin, A.; Bhat, P. N.; Briggs, M. S.; Byrne, D.; Chaplin, V.; Cleveland, W.; Collazzi, A. C.; Goldstein, A.; Kouveliotou, C.; Wilson-Hodge, C.; Gehrels, N.; Harding, A. K.; Nemmen, R.; Racusin, J. L.; Scargle, J. D.

    2013-01-01

    Gamma-ray burst (GRB) 130427A is one of the most energetic GRBs ever observed. The initial pulse up to 2.5 s is possibly the brightest well-isolated pulse observed to date. A fine time resolution spectral analysis shows power-law decays of the peak energy from the onset of the pulse, consistent with models of internal synchrotron shock pulses. However, a strongly correlated power-law behavior is observed between the luminosity and the spectral peak energy that is inconsistent with curvature effects arising in the relativistic outflow. It is difficult for any of the existing models to account for all of the observed spectral and temporal behaviors simultaneously.

  6. Integrable multi-component generalization of a modified short pulse equation

    Science.gov (United States)

    Matsuno, Yoshimasa

    2016-11-01

    We propose a multi-component generalization of the modified short pulse (SP) equation which was derived recently as a reduction of Feng's two-component SP equation. Above all, we address the two-component system in depth. We obtain the Lax pair, an infinite number of conservation laws and multisoliton solutions for the system, demonstrating its integrability. Subsequently, we show that the two-component system exhibits cusp solitons and breathers for which the detailed analysis is performed. Specifically, we explore the interaction process of two cusp solitons and derive the formula for the phase shift. While cusp solitons are singular solutions, smooth breather solutions are shown to exist, provided that the parameters characterizing the solutions satisfy certain conditions. Last, we discuss the relation between the proposed system and existing two-component SP equations.

  7. Improving the efficiency of a fluorescent Xe dielectric barrier light source using short pulse excitation

    Science.gov (United States)

    Beleznai, Sz; Mihajlik, G.; Maros, I.; Balázs, L.; Richter, P.

    2008-06-01

    Operation of a Xe dielectric barrier discharge lamp producing 147-172 nm VUV radiation is investigated both theoretically and experimentally. Xe gas pressure varies between 100 and 300 mbar, and the glass body of the lamp is coated with LAP (green) phosphor to convert radiation into the visible part of the spectrum. Simulation results predict improved discharge efficiencies reaching 67% when excited by a fast rise-time, short pulse (~200 ns) driving waveform. In this case most power deposited into the plasma efficiently produces Xe_2^\\ast excimers, while other energy dissipation processes (ion heating, e-Xe elastic collision) are kept at a low rate. Simulation and experimental results are compared in terms of discharge efficacy and show good agreement. A lamp efficacy value as high as 80 lm W-1 is demonstrated experimentally.

  8. Electronic excitation by short x-ray pulses: from quantum beats to wave packet revivals

    Science.gov (United States)

    Rivière, P.; Iqbal, S.; Rost, J. M.

    2014-06-01

    We propose a simple way to determine the periodicities of wave packets (WPs) in quantum systems directly from the energy differences of the states involved. The resulting classical periods and revival times are more accurate than those obtained with the traditional expansion of the energies about the central quantum number \\overline{n}, especially when \\overline{n} is low. The latter type of WP motion occurs upon excitation of highly charged ions with short XUV or x-ray pulses. Moreover, we formulate the WP dynamics in such a form that it directly reveals the origin of phase shifts in the maxima of the autocorrelation function, a phenomenon most prominent in the low \\overline{n} WP dynamics.

  9. High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M. [Lawrence Berkeley National Lab., CA (United States)

    1996-08-01

    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several {mu}s) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution.

  10. Status of the Short-Pulse X-ray Project at the Advanced Photon Source

    Energy Technology Data Exchange (ETDEWEB)

    Nassiri, A; Berenc, T G; Borland, M; Brajuskovic, B; Bromberek, D J; Carwardine, J; Decker, G; Emery, L; Fuerst, J D; Grelick, A E; Horan, D; Kaluzny, J; Lenkszus, F; Lill, R M; Liu, J; Ma, H; Sajaev, V; Smith, T L; Stillwell, B K; Waldschmidt, G J; Wu, G; Yang, B X; Yang, Y; Zholents, A; Byrd, J M; Doolittle, L R; Huang, G; Cheng, G; Ciovati, G; Dhakal, P; Eremeev, G V; Feingold, J J; Geng, R L; Henry, J; Kneisel, P; Macha, K; Mammosser, J D; Matalevich, J; Palczewski, A D; Rimmer, R A; Wang, H; Wilson, K M; Wiseman, M; Li, Z

    2012-07-01

    The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project.

  11. On some single-hump solutions of the short-pulse equation and their periodic generalizations

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y.; Williams, F.; Whitaker, N. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-4515 (United States); Kevrekidis, P.G., E-mail: kevrekid@gmail.co [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-4515 (United States); Saxena, A. [Center for Nonlinear Studies and Theoretical Division, MS B262, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Frantzeskakis, D.J. [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 15784 (Greece)

    2010-06-28

    In the present work, we consider both localized (e.g. peakon and breather) and extended waveforms (peakon-lattice and breather-lattice, as well as some periodic ones) that arise in the context of the short-pulse equation, as emanating from their sine-Gordon equation analogs. Through direct numerical simulations, we find that the most robust solution is the breather, although some of the single-hump variants of the periodic solutions may be preserved upon the time dynamics as well. Multi-peakon, as well as multi-breather and multi-hump profiles more generally are found to be subject to symmetry-breaking instabilities and are, thus, less robust.

  12. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    Science.gov (United States)

    Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

    2016-06-01

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  13. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station.

    Science.gov (United States)

    Gallmeier, F X; Lu, W; Riemer, B W; Zhao, J K; Herwig, K W; Robertson, J L

    2016-06-01

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm(2) to 20 × 20 mm(2). This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  14. Phase and period responses of the jerboa Jaculus orientalis to short light pulses.

    Science.gov (United States)

    El Moussaouiti, Rachid; Bouhaddou, Nezha; Sabbar, Mariam; Cooper, Howard M; Lakhdar-Ghazal, Nouria

    2010-08-01

    The phase and period responses to short light pulses were studied in the jerboa, a seasonal, hibernating, nocturnal rodent from the Atlas region in Morocco. The jerboa, which is a saltatory species, showed precise activity onsets and offsets under a light-dark (LD) cycle using infrared captors to record locomotor activity. When released into constant darkness (DD), the majority of animals showed a circadian period (tau) light pulses, each separated by at least 2 wks, for up to 160 days in DD. During this span, most individuals maintained robust circadian rhythmicity, with clearly defined activity onsets and offsets, similar levels of total activity, duration of alpha, and percent activity occurring during the subjective night. The phase response curve (PRC) is typical of other nocturnal rodents, with light eliciting delays during late subjective day and early subjective night (CT8-CT19) and advances during late subjective night to early subjective day (CT19-CT2). A dead zone, when light had no effect on phase, is observed during mid-subjective day (CT3-CT8). A few individuals showed large (> 9 h) Type 0 phase resetting near the singularity region (CT19) that resulted in a complete phase reversal, but otherwise displayed normal phase-shifting responses at other CT times. The tau response curve showed a decrease in period from early to late subjective night with increases at other times, but these changes were small (maximum light pulses and, inversely, for animals with long tau to conserve a long tau. This suggests possible constraints on the plasticity of variation of tau in relation to the endogenous period of the animal.

  15. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    Energy Technology Data Exchange (ETDEWEB)

    Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L. [Instrument and Source Division, Oak Ridge National Laboratory, P.O. Box 2008, MS6466, Oak Ridge, Tennessee 37831 (United States)

    2016-06-15

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm{sup 2} to 20 × 20 mm{sup 2}. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  16. Ultrashort Intense Pulse Propagator Applications: Light Strings, Higher Harmonic Generation and Extreme NLO

    Science.gov (United States)

    2010-07-30

    A. Lotti, M. Kolesik, J. V. Moloney, “Analogue gravity and ultrashort laser pulse filamentation”, Europhysics Letters 89, 34004 (2010) Jinjie Liu...followed the same scenario, or if the propagation distance matters. Such was the motivation of our work published recently in Physical Review Letters ...filaments in a high-power pulse determined by the linear “preparation” of the beam? In our previous work published in Physical Review Letters , we

  17. Evolution of extreme temperature events in short term climate projection for Iberian Peninsula.

    Science.gov (United States)

    Rodriguez, Alfredo; Tarquis, Ana M.; Sanchez, Enrique; Dosio, Alessandro; Ruiz-Ramos, Margarita

    2014-05-01

    Extreme events of maximum and minimum temperatures are a main hazard for agricultural production in Iberian Peninsula. For this purpose, in this study we analyze projections of their evolution that could be valid for the next decade, represented in this study by the 30-year period 2004-2034 (target period). For this purpose two kinds of data were used in this study: 1) observations from the station network of AEMET (Spanish National Meteorological Agency) for five Spanish locations, and 2) simulated data at a resolution of 50 ×50 km horizontal grid derived from the outputs of twelve Regional Climate Models (RCMs) taken from project ENSEMBLES (van der Linden and Mitchell, 2009), with a bias correction (Dosio and Paruolo, 2011; Dosio et al., 2012) regarding the observational dataset Spain02 (Herrera et al., 2012). To validate the simulated climate, the available period of observations was compared to a baseline period (1964-1994) of simulated climate for all locations. Then, to analyze the changes for the present/very next future, probability of extreme temperature events for 2004-2034 were compared to that of the baseline period. Although only minor changes are expected, small variations in variability may have a significant impact in crop performance. The objective of the work is to evaluate the utility of these short term projections for potential users, as for instance insurance companies. References Dosio A. and Paruolo P., 2011. Bias correction of the ENSEMBLES high-resolution climate change projections for use by impact models: Evaluation on the present climate. Journal of Geophysical Research, VOL. 116,D16106, doi:10.1029/2011JD015934 Dosio A., Paruolo P. and Rojas R., 2012. Bias correction of the ENSEMBLES high resolution climate change projections for use by impact models: Analysis of the climate change signal. Journal of Geophysical Research,Volume 117, D17, doi: 0.1029/2012JD017968 Herrera et. al. (2012) Development and Analysis of a 50 year high

  18. Theory modeling and experimental research of external-cavity frequency doubling technology of short pulse laser

    Science.gov (United States)

    Duan, Cun-li; Zhang, Su-juan; He, Jiang-long

    2011-06-01

    Q-switched Short pulse laser has been widely applied in many fields, such as optical ranging, remote sensing, communications, nonlinear optics and spectroscopy etc. Q-switched Nd3+: YAG laser, with its high thermal conductivity and resistance to damage threshold, longer energy levels were generally used especially. Second harmonics generation was usually obtained through optical nonlinear effects in crystal. To the frequency doubling technology, poor conversion efficiency and multi-output frequency are the main problems. Researchers focus more on phase and group velocity matching induced by nonlinear effects, but pays less attention on theoretical modeling and numerical calculation of factors affecting frequency doubling of pulsed laser. In this article, nonlinear effects of double frequency crystals in Q-switched Nd3+: YAG laser was first analyzed in theory, then we deduced the relation expressions between factors affecting the efficiency of frequency doubling( thickness of frequency doubling crystal, cross section area of incident beam, power of the fundamental field, phase matching of incidence light)and double frequency efficiency. Secondly, taken KTP Crystal for example; numerical results and theirs' corresponding curves on these relation expressions was calculated and drawn with MATLAB software. These findings can be used for processing the specific requests of frequency doubling crystal. Finally, Theory modeling and numerical calculation were tested in experiment. The experiment results are in good agreement with those obtained in theory.

  19. Short-Pulse Limits in Optical Instrumentation Design for the SLAC Linac Coherent Light Source (LCLS)

    Energy Technology Data Exchange (ETDEWEB)

    Tatchyn, R.

    2005-01-31

    The source properties of linac-driven X-Ray Free-Electron Lasers (XRFELs) operating in the Self-Amplified Spontaneous Emission (SASE) regime differ markedly from those of ordinary insertion devices on synchrotron storage rings. In the case of the 1.5 {angstrom} SLAC Linac Coherent Light Source (LCLS), the longitudinal output profile typically consists of a randomly-distributed train of fully-transversely-coherent micropulses of randomly varying intensity and an average length (corresponding to the source coherence length) two to three orders of magnitude smaller than the transverse diameter of the beam. Total pulse lengths are typically of the same order of size as the beam diameter. Both of these properties can be shown to significantly impact the performance of otherwise conventional synchrotron radiation optics; viz., mirrors, lenses, zone plates, crystals, multilayers, etc. In this paper we outline an analysis of short-pulse effects on selected optical components for the SLAC LCLS and discuss the implications for critical applications such as microfocusing and monochromatization.

  20. Elimination of Lubricants from Aluminum Cold Rolled Products Using Short Laser Pulses

    Directory of Open Access Journals (Sweden)

    Lima M.S.F.

    2002-01-01

    Full Text Available This work presents a new technique to remove the surface impurities from the aluminum cold-worked sheets. The method consists to concentrate a short-time high-power pulsed laser on the materials surface and scan it in order to cover a desired area. Incrustations ablation is obtained as long as the fluency and the peak power are high enough to produce vaporization of the contaminated layer without affecting the material surface properties. The present problem consists in eliminating a desiccated soap of about 1 g/m² from the surface of a 6016-class aluminum alloy sheet. The soap is originated from the rolling process. The present laser method is intended to replace water washing when the piece cannot be soaked, when drying is difficult due to the geometry, or when environmental restrictions apply. Best results were obtained when the pulse length was 100 ns and the average laser power was 95 W. In these conditions, the surface was completely cleaned and the aluminum alloy did not suffer any structural modification.

  1. Distinguishing mechanisms of plasma-based amplification for short laser pulses

    Science.gov (United States)

    Jia, Qing; Edwards, Matthew; Barth, Ido; Mikhailova, Julia; Fisch, Nathaniel

    2016-10-01

    Several plasma-based amplification mechanisms have been proposed to obtain short laser pulses with ultrahigh intensities beyond the damage threshold of solid-state devices, including Compton-like superradiant amplification, backward Raman amplification and strongly-coupled Brillouin amplification. These three mechanisms are all based on the periodic structure of particle (electrons for the former two and ions for Brillouin amplification) density fluctuations that function as a grating. By turning off the ion motion in particle-in-cell simulations, we can distinguish Brillouin from Raman, and show that Raman amplification is responsible for the main leading spike amplification of ultrashort pulses. By artificially turning off the longitudinal electric field (Ex) in simulations, we can distinguish Raman from Compton-like superradiant amplification. Interestingly, we find that the superradiant amplification in Ex-off simulation is similar to the amplification in pair plasmas, with roughly half amplification efficiency of the latter due to absence of equal contribution from positrons. In addition, we also discuss the competition between Brillouin amplification and superradiant amplification in pair plasmas by comparing the dominance of thermal pressure and ponderomotive force.

  2. Self-phase modulation of an ultra-short laser pulse from laser breakdown plasma

    Science.gov (United States)

    Zhang, Yongsheng; Yan, Lixin; Zheng, Guoxin; Wang, Lijun; Liu, Jingru

    2007-01-01

    The detailed dynamic of an atom in a laser field with strength comparable to the atomic electric field is rich in physics and potential applications. Laser-breakdown plasma-induced spectral shifting in supersonic rare gases jet has been investigated with a sub-picosecond KrF excimer laser focused to peak intensity in the region of 10 15W/cm2. A 1.4mm diameter gas jet target was used in the experiment to minimize the refraction of the laser beam and thus a well-defined focused region was obtained. The typical quasi-periodic spectral shifting structures for helium and argon have been measured at various gas densities. For gas densities below 1x10 20cm -3,both spectral red-shift and blue-shift were observed, indicating the gas is partially ionized, in contrast to the predominantly blue shifted as the gas densities grows high and fully ionized. Compared to the other ultra-short pulse measurement methods, qualitative information about the pulse can be deduced by observing their spectrum after interacting with rare gas.

  3. Ultra-short laser pulse ablation using shear-force feedback: Femtosecond laser induced breakdown spectroscopy feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Samek, Ota [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany)]. E-mail: samek@ansci.de; Kurowski, Andre [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany); Kittel, Silke [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany); Kukhlevsky, Sergei [Institute of Physics, University of Pecs, Ifjusag u. 6, Pecs 7624 (Hungary); Hergenroeder, Roland [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany)

    2005-08-31

    This work reports on a feasibility study of proximity ablation using femtosecond pulses. Ultra-short pulses were launched to a bare tapered optical fiber and delivered to the sample. The tip-sample distance was controlled by means of shear-force feedback. Consequently, ablation craters with submicrometer dimensions were obtained. Potential analytical applications for Laser Induced Breakdown Spectroscopy (LIBS) technique, such as e.g. inclusions in steel or bio cells, are suggested.

  4. Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Y. [Laboratory of Advanced Materials, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China); Greuner, H.; Böswirth, B.; Krieger, K. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, 85748 Garching (Germany); Luo, G.-N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Xu, H.Y.; Fu, B.Q.; Li, M. [Laboratory of Advanced Materials, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, W., E-mail: liuw@mail.tsinghua.edu.cn [Laboratory of Advanced Materials, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2013-02-15

    Highlights: ► Recrystallization temperature of a rolled W was ∼2480 °C under applied HHF loads. ► Fine grains were obtained under HHF loads with appropriate short pulse length. ► With increasing pulse length, the recrystallized grains significantly grew larger. ► A linear relationship between ln d and 1/T{sub max} was found. ► Activation energy for grain growth in T evolution up to T{sub max} in 1.5 s was obtained. -- Abstract: Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m{sup 2} were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/T{sub max}) was found and accordingly the activation energy for grain growth in temperature evolution up to T{sub max} in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads.

  5. Short-pulse, high-energy radiation generation from laser-wakefield accelerated electron beams

    Science.gov (United States)

    Schumaker, Will

    2013-10-01

    Recent experimental results of laser wakefield acceleration (LWFA) of ~GeV electrons driven by the 200TW HERCULES and the 400TW ASTRA-GEMINI laser systems and their subsequent generation of photons, positrons, and neutrons are presented. In LWFA, high-intensity (I >1019 W /cm2), ultra-short (τL Z target via bremsstrahlung into low-divergence (Z, the resulting Ne+ /Ne- ratio can approach unity, resulting in a near neutral density plasma jet. These quasi-neutral beams are presumed to retain the short-pulse (τL characteristic of the electron beam, resulting in a high peak density of ne- /e+ ~ 1016 cm-3 , making the source an excellent candidate for laboratory study of astrophysical leptonic jets. Alternatively, the electron beam can be interacted with a counter-propagating, ultra-high intensity (I >1021 W /cm2) laser pulse to undergo inverse Compton scattering and emit a high-peak brightness beam of high-energy photons. Preliminary results and experimental sensitivities of the electron-laser beam overlap are presented. The high-energy photon beams can be spectrally resolved using a forward Compton scattering spectrometer. Moreover, the photon flux can be characterized by a pixelated scintillator array and by nuclear activation and (γ,n) neutron measurements from the photons interacting with a secondary solid target. Monte-Carlo simulations were performed using FLUKA to support the yield estimates. This research was supported by DOE/NSF-PHY 0810979, NSF CAREER 1054164, DARPA AXiS N66001-11-1-4208, SF/DNDO F021166, and the Leverhulme Trust ECF-2011-383.

  6. Nike Experiment to Observe Strong Areal Mass Oscillations in a Rippled Target Hit by a Short Laser Pulse

    Science.gov (United States)

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

    2010-11-01

    When a short (sub-ns) laser pulse deposits finite energy in a target, the shock wave launched into it is immediately followed by a rarefaction wave. If the irradiated surface is rippled, theory and simulations predict strong oscillations of the areal mass perturbation amplitude in the target [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003).] The first experiment designed to observe this effect has become possible by adding short-driving-pulse capability to the Nike laser, and has been scheduled for the fall of 2010. Simulations show that while the driving pulse of 0.3 ns is on, the areal mass perturbation amplitude grows by a factor ˜2 due to ablative Richtmyer-Meshkov instability. It then decreases, reverses phase, and reaches another maximum, also about twice its initial value, shortly after the shock breakout at the rear target surface. This signature behavior is observable with the monochromatic x-ray imaging diagnostics fielded on Nike.

  7. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    CERN Document Server

    Shakhmuratov, R N

    2016-01-01

    The resonant filtering method transforming frequency modulated radiation field into a train of short pulses is proposed to apply in optical domain. Effective frequency modulation can be achieved by electro-optic modulator or by resonant frequency modulation of the filter with a narrow absorption line. Due to frequency modulation narrow-spectrum CW radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning narrow-bandwidth filter in resonance with $n$-th spectral component of the comb transforms the radiation field into bunches of pulses with $n$ pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in formation of pulses, while destructive interference is seen as dark windows between pulses. It is found that the optimal thickness of the resonant filter is several orders of magnitude smaller than the...

  8. Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

    Science.gov (United States)

    Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H. Y.; Fu, B. Q.; Li, M.; Liu, W.

    2013-02-01

    Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/Tmax) was found and accordingly the activation energy for grain growth in temperature evolution up to Tmax in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads.

  9. Laser-driven proton acceleration enhancement by the optimized intense short laser pulse shape

    Science.gov (United States)

    Souri, S.; Amrollahi, R.; Sadighi-Bonabi, R.

    2017-05-01

    Interactions of two distinct shapes of the pulses namely positive/negative chirped pulse and fast/slow rising-edge pulse with plasma are studied using particle-in-cell simulation. It is found that, for a pulse duration of 34 fs and intensity a0 = 12, proton acceleration could be enhanced by asymmetric pulses with either pulse envelope or pulse frequency modification. The number of accelerated protons, as well as the proton energy cut-off, is increased by asymmetric pulses. In this work, for positive chirped pulse, electrostatic field at the rear side of the target is improved by about 30%, which in turns leads to an increase in the proton energy cut-off more than 40%. Moreover, in contrary to the fast pulses, the slow one could enhance the proton energy cut-off up to 65% for 34 fs pulse with 20 fs rising-edge.

  10. Inactivation of Pseudomonas putida by pulsed electric field treatment: a study on the correlation of treatment parameters and inactivation efficiency in the short-pulse range.

    Science.gov (United States)

    Frey, Wolfgang; Gusbeth, Christian; Schwartz, Thomas

    2013-10-01

    An important issue for an economic application of the pulsed electric field treatment for bacterial decontamination of wastewater is the specific treatment energy needed for effective reduction of bacterial populations. The present experimental study performed in a field amplitude range of 40 > E > 200 kV/cm and for a suspension conductivity of 0.01 = κ(e) > 0.2 S/m focusses on the application of short pulses, 25 ns > T > 10 μs, of rectangular, bipolar and exponential shape and was made on Pseudomonas putida, which is a typical and widespread wastewater microorganism. The comparison of inactivation results with calculations of the temporal and azimuthal membrane charging dynamics using the model of Pauly and Schwan revealed that for efficient inactivation, membrane segments at the cell equator have to be charged quickly and to a sufficiently high value, on the order of 0.5 V. After fulfilling this basic condition by an appropriate choice of pulse field strength and duration, the log rate of inactivation for a given suspension conductivity of 0.2 S/m was found to be independent of the duration of individual pulses for constant treatment energy expenditure. Moreover, experimental results suggest that even pulse shape plays a minor role in inactivation efficiency. The variation of the suspension conductivity resulted in comparable inactivation performance of identical pulse parameters if the product of pulse duration and number of pulses was the same, i.e., required treatment energy can be linearly downscaled for lower conductivities, provided that pulse amplitude and duration are selected for entire membrane surface permeabilization.

  11. Multiphoton Ionization as a clock to Reveal Molecular Dynamics with Intense Short X-ray Free Electron Laser Pulses

    CERN Document Server

    Fang, L; Murphy, B; Tarantelli, F; Kukk, E; Cryan, J P; Glownia, M; Bucksbaum, P H; Coffee, R N; Chen, M; Buth, C; Berrah, N

    2013-01-01

    We investigate molecular dynamics of multiple ionization in N2 through multiple core-level photoabsorption and subsequent Auger decay processes induced by intense, short X-ray free electron laser pulses. The timing dynamics of the photoabsorption and dissociation processes is mapped onto the kinetic energy of the fragments. Measurements of the latter allow us to map out the average internuclear separation for every molecular photoionization sequence step and obtain the average time interval between the photoabsorption events. Using multiphoton ionization as a tool of multiple-pulse pump-probe scheme, we demonstrate the modi?cation of the ionization dynamics as we vary the x-ray laser pulse duration.

  12. HATS-18b: An Extreme Short-period Massive Transiting Planet Spinning Up Its Star

    Science.gov (United States)

    Penev, K.; Hartman, J. D.; Bakos, G. Á.; Ciceri, S.; Brahm, R.; Bayliss, D.; Bento, J.; Jordán, A.; Csubry, Z.; Bhatti, W.; de Val-Borro, M.; Espinoza, N.; Zhou, G.; Mancini, L.; Rabus, M.; Suc, V.; Henning, T.; Schmidt, B.; Noyes, R. W.; Lázár, J.; Papp, I.; Sári, P.

    2016-11-01

    We report the discovery by the HATSouth network of HATS-18b: a 1.980+/- 0.077 {M}{{J}}, {1.337}-0.049+0.102 {R}{{J}} planet in a 0.8378 day orbit, around a solar analog star (mass 1.037+/- 0.047 {M}⊙ and radius {1.020}-0.031+0.057 {R}⊙ ) with V=14.067+/- 0.040 mag. The high planet mass, combined with its short orbital period, implies strong tidal coupling between the planetary orbit and the star. In fact, given its inferred age, HATS-18 shows evidence of significant tidal spin up, which together with WASP-19 (a very similar system) allows us to constrain the tidal quality factor for Sun-like stars to be in the range of 6.5≲ {{log}}10({Q}* /{k}2)≲ 7 even after allowing for extremely pessimistic model uncertainties. In addition, the HATS-18 system is among the best systems (and often the best system) for testing a multitude of star-planet interactions, be they gravitational, magnetic, or radiative, as well as planet formation and migration theories. The HATSouth network is operated by a collaboration consisting of Princeton University (PU), the Max Planck Institute für Astronomie (MPIA), the Australian National University (ANU), and the Pontificia Universidad Católica de Chile (PUC). The station at Las Campanas Observatory (LCO) of the Carnegie Institute is operated by PU in conjunction with PUC, the station at the High Energy Spectroscopic Survey (H.E.S.S.) site is operated in conjunction with MPIA, and the station at Siding Spring Observatory (SSO) is operated jointly with ANU. This paper includes data gathered with the MPG 2.2 m telescope at the ESO Observatory in La Silla. This paper uses observations obtained with facilities of the Las Cumbres Observatory Global Telescope.

  13. Neutron imaging with the short-pulse laser driven neutron source at the Trident laser facility

    Science.gov (United States)

    Guler, N.; Volegov, P.; Favalli, A.; Merrill, F. E.; Falk, K.; Jung, D.; Tybo, J. L.; Wilde, C. H.; Croft, S.; Danly, C.; Deppert, O.; Devlin, M.; Fernandez, J.; Gautier, D. C.; Geissel, M.; Haight, R.; Hamilton, C. E.; Hegelich, B. M.; Henzlova, D.; Johnson, R. P.; Schaumann, G.; Schoenberg, K.; Schollmeier, M.; Shimada, T.; Swinhoe, M. T.; Taddeucci, T.; Wender, S. A.; Wurden, G. A.; Roth, M.

    2016-10-01

    Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at the laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ˜5 × 109 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5-35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ˜1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. These experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical work into the

  14. Compact Short-Pulsed Electron Linac Based Neutron Sources for Precise Nuclear Material Analysis

    Science.gov (United States)

    Uesaka, M.; Tagi, K.; Matsuyama, D.; Fujiwara, T.; Dobashi, K.; Yamamoto, M.; Harada, H.

    2015-10-01

    An X-band (11.424GHz) electron linac as a neutron source for nuclear data study for the melted fuel debris analysis and nuclear security in Fukushima is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident is established. For the purpose, we should now accumulate more precise nuclear data of U, Pu, etc., especially in epithermal (0.1-10 eV) neutrons. Therefore, we have decided to modify and install the linac in the core space of the experimental nuclear reactor "Yayoi" which is now under the decommission procedure. Due to the compactness of the X-band linac, an electron gun, accelerating tube and other components can be installed in a small space in the core. First we plan to perform the time-of-flight (TOF) transmission measurement for study of total cross sections of the nuclei for 0.1-10 eV energy neutrons. Therefore, if we adopt a TOF line of less than 10m, the o-pulse length of generated neutrons should be shorter than 100 ns. Electronenergy, o-pulse length, power, and neutron yield are ~30 MeV, 100 ns - 1 micros, ~0.4 kW, and ~1011 n/s (~103 n/cm2/s at samples), respectively. Optimization of the design of a neutron target (Ta, W, 238U), TOF line and neutron detector (Ce:LiCAF) of high sensitivity and fast response is underway. We are upgrading the electron gun and a buncher to realize higher current and beam power with a reasonable beam size in order to avoid damage of the neutron target. Although the neutron flux is limited in case of the X-band electron linac based source, we take advantage of its short pulse aspect and availability for nuclear data measurement with a short TOF system. First, we form a tentative configuration in the current experimental room for Compton scattering in 2014. Then, after the decommissioning has been finished, we move it to the "Yayoi" room and perform

  15. X-Ray and Extreme Ultraviolet Emission from Small-Sized Kr Clusters Irradiated by 150-fs Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    王骐; 程元丽; 赵永蓬; 夏元钦; 陈建新; 肖亦凡

    2003-01-01

    x-ray and extreme ultraviolet (EUV) emission from Kr clusters irradiated by 150-fs laser pulses at the peak laser intensity of 5×1015W/cm2 was experimentally investigated. Strong transitions (10nm-13nm) from Kr X and Kr 1X were observed and some spectral lines from Kr ⅩⅢ and Kr ⅩⅣ, which have been predicted to be not produced by optical-field-ionization at the laser intensity used, also appeared. The laser energy absorption and the intensity of x-ray emission started to grow remarkably above the backing pressure of 0.5 MPa and to decrease at the backing pressure of 3 MPa. It is suggested that an optimum backing pressure may exist for Kr clusters heated by 150 fs laser pulses at a certain laser intensity to produce x-ray emission.

  16. Pulse

    Science.gov (United States)

    ... resting for at least 10 minutes. Take the exercise heart rate while you are exercising. ... pulse rate can help determine if the person's heart is pumping. Pulse ... rate gives information about your fitness level and health.

  17. Ultra-short pulsed ytterbium-doped fiber laser and amplifier

    Institute of Scientific and Technical Information of China (English)

    Guanglei Ding; Xin Zhao; Yishan Wang; Wei Zhao; Guofu Chen

    2006-01-01

    @@ This paper investigates a high power all fiber ultrashort pulse laser system. This system consists of a modelocking laser oscillator, a multi-stage amplifier, a pulse selector, and a paired grating pulse compressor.With pulse energy of 12 μJ at repetition rate of 30 kHz, the laser at center wavelength of 1.05 μm was obtained. Pulse width of 525 fs was achieved after the grating pair compressor.

  18. Au-C allotrope nano-composite films at extreme conditions generated by intense ultra-short laser

    Science.gov (United States)

    Khan, Saif A.; Saravanan, K.; Tayyab, M.; Bagchi, S.; Avasthi, D. K.

    2016-07-01

    Structural evolution of gold-carbon allotrope nano-composite films under relativistically intense, ultra-short laser pulse irradiation is studied in this work. Au-C nano-composite films, having 4 and 10 at.% of Au, were deposited by co-sputtering technique on silicon substrates. Au-C60 NC films with 2.5 at.% Au were deposited on 12 μm thick Al foil using co-evaporation technique. These samples were radiated with single pulse from 45 fs, 10 TW Ti:Sapphire Laser at RRCAT at an intensity of 3 × 1018 W cm-2. The morphological and compositional changes were investigated using scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS) techniques. Laser pulse created three morphologically distinct zones around the point of impact on samples with silicon substrates. The gold content in 600 μm circular region around a point of impact is found to reduce by a factor of five. Annular rings of ∼70 nm in diameter were observed in case of Au-C NC film after irradiation. Laser pulse created a hole of about 400 μm in the sample with Al foil as substrate and wavy structures of 6 μm wavelength are found to be created around this hole. The study shows radial variation in nano-structure formation with varying local intensity of laser pulse.

  19. Au–C allotrope nano-composite films at extreme conditions generated by intense ultra-short laser

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Saif A., E-mail: khansaifahmad@gmail.com [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Saravanan, K. [Department of Physics, Tamkang University, Tamsui 251, Taiwan (China); Tayyab, M.; Bagchi, S. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Avasthi, D.K. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Amity University, Noida 201313, Uttar Pradesh (India)

    2016-07-15

    Structural evolution of gold–carbon allotrope nano-composite films under relativistically intense, ultra-short laser pulse irradiation is studied in this work. Au–C nano-composite films, having 4 and 10 at.% of Au, were deposited by co-sputtering technique on silicon substrates. Au–C{sub 60} NC films with 2.5 at.% Au were deposited on 12 μm thick Al foil using co-evaporation technique. These samples were radiated with single pulse from 45 fs, 10 TW Ti:Sapphire Laser at RRCAT at an intensity of 3 × 10{sup 18} W cm{sup −2}. The morphological and compositional changes were investigated using scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS) techniques. Laser pulse created three morphologically distinct zones around the point of impact on samples with silicon substrates. The gold content in 600 μm circular region around a point of impact is found to reduce by a factor of five. Annular rings of ∼70 nm in diameter were observed in case of Au–C NC film after irradiation. Laser pulse created a hole of about 400 μm in the sample with Al foil as substrate and wavy structures of 6 μm wavelength are found to be created around this hole. The study shows radial variation in nano-structure formation with varying local intensity of laser pulse.

  20. Multiple Ionization of Free Ubiquitin Molecular Ions in Extreme Ultraviolet Free-Electron Laser Pulses

    NARCIS (Netherlands)

    Schlathölter, Thomas; Reitsma, Geert; Egorov, Dmitrii; Gonzalez-Magaña, Olmo; Bari, Sadia; Boschman, Leon; Bodewits, Erwin; Schnorr, Kirsten; Schmid, Georg; Schröter, Claus Dieter; Moshammer, Robert; Hoekstra, Ronnie

    2016-01-01

    The fragmentation of free tenfold protonated ubiquitin in intense 70 femtosecond pulses of 90 eV photons from the FLASH facility was investigated. Mass spectrometric investigation of the fragment cations produced after removal of many electrons revealed fragmentation predominantly into immonium ions

  1. Extreme nonlinear terahertz electro-optics in diamond for ultrafast pulse switching

    Science.gov (United States)

    Shalaby, Mostafa; Vicario, Carlo; Hauri, Christoph P.

    2017-03-01

    Polarization switching of picosecond laser pulses is a fundamental concept in signal processing [C. Chen and G. Liu, Annu. Rev. Mater. Sci. 16, 203 (1986); V. R. Almeida et al., Nature 431, 1081 (2004); and A. A. P. Pohl et al., Photonics Sens. 3, 1 (2013)]. Conventional switching devices rely on the electro-optical Pockels effect and work at radio frequencies. The ensuing gating time of several nanoseconds is a bottleneck for faster switches which is set by the performance of state-of-the-art high-voltage electronics. Here we show that by substituting the electric field of several kV/cm provided by modern electronics by the MV/cm field of a single-cycle THz laser pulse, the electro-optical gating process can be driven orders of magnitude faster, at THz frequencies. In this context, we introduce diamond as an exceptional electro-optical material and demonstrate a pulse gating time as fast as 100 fs using sub-cycle THz-induced Kerr nonlinearity. We show that THz-induced switching in the insulator diamond is fully governed by the THz pulse shape. The presented THz-based electro-optical approach overcomes the bandwidth and switching speed limits of conventional MHz/GHz electronics and establishes the ultrafast electro-optical gating technology for the first time in the THz frequency range. We finally show that the presented THz polarization gating technique is applicable for advanced beam diagnostics. As a first example, we demonstrate tomographic reconstruction of a THz pulse in three dimensions.

  2. Extreme nonlinear terahertz electro-optics in diamond for ultrafast pulse switching

    Directory of Open Access Journals (Sweden)

    Mostafa Shalaby

    2017-03-01

    Full Text Available Polarization switching of picosecond laser pulses is a fundamental concept in signal processing [C. Chen and G. Liu, Annu. Rev. Mater. Sci. 16, 203 (1986; V. R. Almeida et al., Nature 431, 1081 (2004; and A. A. P. Pohl et al., Photonics Sens. 3, 1 (2013]. Conventional switching devices rely on the electro-optical Pockels effect and work at radio frequencies. The ensuing gating time of several nanoseconds is a bottleneck for faster switches which is set by the performance of state-of-the-art high-voltage electronics. Here we show that by substituting the electric field of several kV/cm provided by modern electronics by the MV/cm field of a single-cycle THz laser pulse, the electro-optical gating process can be driven orders of magnitude faster, at THz frequencies. In this context, we introduce diamond as an exceptional electro-optical material and demonstrate a pulse gating time as fast as 100 fs using sub-cycle THz-induced Kerr nonlinearity. We show that THz-induced switching in the insulator diamond is fully governed by the THz pulse shape. The presented THz-based electro-optical approach overcomes the bandwidth and switching speed limits of conventional MHz/GHz electronics and establishes the ultrafast electro-optical gating technology for the first time in the THz frequency range. We finally show that the presented THz polarization gating technique is applicable for advanced beam diagnostics. As a first example, we demonstrate tomographic reconstruction of a THz pulse in three dimensions.

  3. DEVELOPMENT OF A COMPACT PHOTO-INJECTOR WITH RFFOCUSING LENS FOR SHORT PULSE ELECTRON SOURCE APPLICATION

    Energy Technology Data Exchange (ETDEWEB)

    Grabenhofer, Alexander [Northern Illinois University; Eaton, Douglas W. [ScandiNova systems AB, Uppsala, Sweden

    2013-09-01

    For development of compact ultrafast electron source system, we are currently designing a short-pulse RF-gun with RF focusing structure by means of a series of comprehensive modeling analysis processes. EM design of a 2.5 cell resonant cavity with input coupler, acceleration dynamics of photo-emitted electron bunch, EM design of RF-lens with input coupler, and phasespace analysis of focused electron bunch are systematically examined with multi-physics simulators. All the features of the 2.856 GHz cavity geometry were precisely engineered for acceleration energies ranging from 100 keV to 500 keV (safety limited) to be powered by our 5 MW S-band klystron. The klystron (Thales TH2163) and modulator system (ScandiNova K1 turnkey system) were successfully installed and tested. Performance tests of the klystron system show peak output power > 5 MW, as per operation specifications. At the quasi-relativistic energies, the electron source is capable of generating 100fC – 1 pC electron bunch with pulse duration close to 30 fs – 1 ps and transverse size of a few hundred microns. PIC simulations have shown that the electron bunch undergoes fast RF acceleration, rapidly reaching the desired energies, which can be controlled by tuning RF injection phase and input driving power. It has been shown that it is possible to also focus/compress the bunch longitudinally using a RF-lens, which would allow us to control the temporal resolution of the system as well. While our primary analysis has been performed on a 2.5 cell design, we are also looking into half-cell (single cavity) design that is expected to provide the same range of beam energy with a simple configuration.

  4. Phase and period responses to short light pulses in a wild diurnal rodent, Funambulus pennanti.

    Science.gov (United States)

    Kumar, Dhanananajay; Singaravel, Muniyandi

    2014-04-01

    Photic phase response curves (PRCs) have been extensively studied in many laboratory-bred diurnal and nocturnal rodents. However, comparatively fewer studies have addressed the effects of photic cues on wild diurnal mammals. Hence, we studied the effects of short durations of light pulses on the circadian systems of the diurnal Indian Palm squirrel, Funambulus pennanti. Adult males entrained to a light-dark cycle (12 h-12 h) were transferred to constant darkness (DD). Free-running animals were exposed to brief light pulses (250 lux) of 15 min, 3 circadian hours (CT) apart (CT 0, 3, 6, 9, 12, 15, 18 and 21). Phase shifts evoked at different phases were plotted against CT and a PRC was constructed. F. pennanti exhibited phase-dependent phase shifts at all the CTs studied, and the PRC obtained was of type 1 at the intensity of light used. Phase advances were evoked during the early subjective day and late subjective night, while phase delays occurred during the late subjective day and early subjective night, with maximum phase delay at CT 15 (-2.04 ± 0.23 h), and maximum phase advance at CT 21 (1.88 ± 0.31 h). No dead zone was seen at this resolution. The free-running period of the rhythm was concurrently lengthened (deceleration) during the late subjective day and early subjective night, while period shortening (acceleration) occurred during the late subjective night. The maximum deceleration was noticed at CT 15 (-0.40 ± 0.09 h) and the maximum acceleration at CT 21 (0.39 ± 0.07 h). A significant positive correlation exists between the phase shifts and the period changes (r = 0.684, p = 0.001). The shapes of both the PRC and period response curve (τRC) qualitatively resemble each other. This suggests that the palm squirrel's circadian system is entrained both by phase and period responses to light. Thus, F. pennanti exhibits robust clock-resetting in response to light pulses.

  5. Short term effects of corticosteroid pulse treatment on disease activity and the wellbeing of patients with active rheumatoid arthritis

    NARCIS (Netherlands)

    Jacobs, JWG; Geenen, R; Evers, AWM; van Jaarsveld, CHM; Kraaimaat, FW; Bijlsma, JWJ

    2001-01-01

    Objective-To investigate the short term effects of corticosteroid pulse treatment (CPT) ability, and psychological wellbeing of patients with active rheumatoid arthritis (RA). Methods-Of 66 consecutive patients with active RA admitted for CPT, erythrocyte sedimentation rate, C reactive protein level

  6. Short-term effects of a standardized glucose load on region-specific aortic pulse wave velocity assessed by MRI

    NARCIS (Netherlands)

    Jonker, J.T.; Tjeerdema, N.; Hensen, L.C.; Lamb, H.J.; Romijn, J.A.; Smit, J.W.; Westenberg, J.J.; Roos, A. de

    2014-01-01

    PURPOSE: To assess the short-term effects of a standardized oral glucose load on regional aortic pulse wave velocity (PWV) using two-directional in-plane velocity encoded MRI. MATERIALS AND METHODS: A randomized, controlled intervention was performed in 16 male subjects (mean +/- standard deviation:

  7. Generating a New Higher-Dimensional Ultra-Short Pulse System: Lie-Algebra Valued Connection and Hidden Structural Symmetries

    Institute of Scientific and Technical Information of China (English)

    Hermann T. Tchokouansi; Victor K. Kuetche; Abbagari Souleymanou; Thomas B. Bouetou; Timoleon C. Kofane

    2012-01-01

    We carry out the hidden structural symmetries embedded within a system comprising ultra-short pulses which propagate in optical nonlinear media. Based upon the Wahlquist Estabrook approach, we construct the Lie-algebra valued connections associated to the previous symmetries while deriving their corresponding Lax-pairs, which are particularly useful in soliton theory. In the wake of previous results, we extend the above prolongation scheme to higher-dimensional systems from which a new (2 + l)-dimensional ultra-short pulse equation is unveiled along with its inverse scattering formulation, the application of which are straightforward in nonlinear optics where an additional propagating dimension deserves some attention.%We carry out the hidden structural symmetries embedded within a system comprising ultra-short pulses which propagate in optical nonlinear media.Based upon the Wahlquist Estabrook approach,we construct the Liealgebra valued connections associated to the previous symmetries while deriving their corresponding Lax-pairs,which are particularly useful in soliton theory.In the wake of previous results,we extend the above prolongation scheme to higher-dimensional systems from which a new (2+ 1)-dimensional ultra-short pulse equation is unveiled along with its inverse scattering formulation,the application of which are straightforward in nonlinear optics where an additional propagating dimension deserves some attention.

  8. Properties of high-frequency sub-wavelength ripples on stainless steel 304L under ultra short pulse laser irradiation

    NARCIS (Netherlands)

    Mitko, V.S.; Röer, G.R.B.E.; Huis in 't veld, A.J.; Skolski, J.Z.P.; Obona, J.V.; Ocelík, V.; Hosson, J.T.M.de

    2011-01-01

    The paper concentrates on surface texturing on sub-micro meter scale with ultra short laser pulses that has several applications, e.g. changing the hydrophilic/hydrophobic performance, optical or tribological properties of materials. In general, the formations of wavy structures, or ripples on a sur

  9. Properties of High-Frequency Sub-Wavelength Ripples on Stainless Steel 304L under Ultra Short Pulse Laser Irradiation

    NARCIS (Netherlands)

    Mitko, V.S.; Römer, G.R.B.E.; Huis in ‘t Veld, A.J.; Skolski, J.Z.P.; Obona, J.V.; Ocelík, V.; Hosson, J.T.M. De

    2011-01-01

    The paper concentrates on surface texturing on sub-micro meter scale with ultra short laser pulses that has several applications, e.g. changing the hydrophilic/hydrophobic performance, optical or tribological properties of materials. In general, the formations of wavy structures, or ripples on a sur

  10. Short term effects of corticosteroid pulse treatment on disease activity and the wellbeing of patients with active rheumatoid arthritis

    NARCIS (Netherlands)

    Jacobs, JWG; Geenen, R; Evers, AWM; van Jaarsveld, CHM; Kraaimaat, FW; Bijlsma, JWJ

    2001-01-01

    Objective-To investigate the short term effects of corticosteroid pulse treatment (CPT) ability, and psychological wellbeing of patients with active rheumatoid arthritis (RA). Methods-Of 66 consecutive patients with active RA admitted for CPT, erythrocyte sedimentation rate, C reactive protein level

  11. Pulse-front tilt for short-wavelength lasing by means of traveling-wave plasma-excitation.

    Science.gov (United States)

    Bleiner, Davide; Feurer, Thomas

    2012-12-20

    Generation of coherent short-wavelength radiation across a plasma column is dramatically improved under traveling-wave excitation (TWE). The latter is optimized when its propagation is close to the speed of light, which implies small-angle target-irradiation. Yet, short-wavelength lasing needs large irradiation angles in order to increase the optical penetration of the pump into the plasma core. Pulse-front back-tilt is considered to overcome such trade-off. In fact, the TWE speed depends on the pulse-front slope (envelope of amplitude), whereas the optical penetration depth depends on the wave-front slope (envelope of phase). Pulse-front tilt by means of compressor misalignment was found effective only if coupled with a high-magnification front-end imaging/focusing component. It is concluded that speed matching should be accomplished with minimal compressor misalignment and maximal imaging magnification.

  12. The change of electric potentials in the oral cavity after application of extremely low frequency pulsed magnetic field

    Directory of Open Access Journals (Sweden)

    Piotr Skomro

    2012-12-01

    Full Text Available Electric potentials occurring in the oral cavity deserve attention as they may cause various diseases and subjective feelings, which are very difficult to treat. The aim of this study was to evaluate the electric potentials within the oral cavity in patients with metal fillings and metal prosthetic restorations, after using a pulsed electromagnetic field. The study was carried out on 84 patients. The Viofor JPS Classic device was used in the treatment. It generates a pulsed electromagnetic field with low induction of the extremely low frequency (ELF range. Average values of electric potentials in the preliminary test were about the same in both groups; they were 148.8 mV and 145.5 mV. After another appliance of ELF fields there was found a steady decline in the average value of electric potentials in the study group. This decrease was statistically highly significant, while mean values of electric potentials in the control group were characterized by a slightly upward tendency. The obtained statistically significant reduction of electric potentials in the oral cavity of patients having metal fillings and metal prosthetic restorations, after application of the Viofor JPS Classic device, implies a huge impact of ELF pulsed electromagnetic field on inhibition of electrochemical processes, as well as on inhibition of dental alloy corrosion. 

  13. The change of electric potentials in the oral cavity after application of extremely low frequency pulsed magnetic field.

    Science.gov (United States)

    Skomro, Piotr; Lietz-Kijak, Danuta; Kijak, Edward; Bogdziewicz-Wałęsa, Olga; Opalko, Krystyna

    2012-12-11

    Electric potentials occurring in the oral cavity deserve attention as they may cause various diseases and subjective feelings, which are very difficult to treat. The aim of this study was to evaluate the electric potentials within the oral cavity in patients with metal fillings and metal prosthetic restorations, after using a pulsed electromagnetic field. The study was carried out on 84 patients. The Viofor JPS Classic device was used in the treatment. It generates a pulsed electromagnetic field with low induction of the extremely low frequency (ELF) range. Average values of electric potentials in the preliminary test were about the same in both groups; they were 148.8 mV and 145.5 mV. After another appliance of ELF fields there was found a steady decline in the average value of electric potentials in the study group. This decrease was statistically highly significant, while mean values of electric potentials in the control group were characterized by a slightly upward tendency. The obtained statistically significant reduction of electric potentials in the oral cavity of patients having metal fillings and metal prosthetic restorations, after application of the Viofor JPS Classic device, implies a huge impact of ELF pulsed electromagnetic field on inhibition of electrochemical processes, as well as on inhibition of dental alloy corrosion. 

  14. Spectral investigations of photoionized plasmas induced in atomic and molecular gases using nanosecond extreme ultraviolet (EUV) pulses

    Energy Technology Data Exchange (ETDEWEB)

    Bartnik, A.; Fiedorowicz, H.; Wachulak, P. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

    2014-07-15

    In this paper, results of spectral investigations of low temperature photoionized plasmas, created by irradiation of gases with intense pulses of extreme ultraviolet (EUV) radiation from a laser-produced plasma (LPP) source, are presented. The LPP source was based on a double-stream KrXe/He gas-puff target irradiated with 4 ns/0.8 J/10 Hz Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region λ ≈ 10–12 nm; however, spectrally integrated intensity at longer wavelengths was also significant. The EUV beam was focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in formation of photoionized plasmas emitting radiation in the EUV range. Radiation spectra, measured for plasmas produced in various gases, are dominated by emission lines, originating from single charged ions. Significant differences in spectral intensities and distributions between plasmas created in neon and molecular gases were observed.

  15. Medical and psychosocial implications of adolescent extreme obesity – acceptance and effects of structured care, short: Youth with Extreme Obesity Study (YES)

    Science.gov (United States)

    2013-01-01

    Background Prevalence rates of overweight and obesity have increased in German children and adolescents in the last three decades. Adolescents with extreme obesity represent a distinct risk group. On the basis of data obtained by the German Child and Youth Survey (KiGGS) and the German district military offices we estimate that the group of extremely obese adolescents (BMI ≥ 35 kg/m2) currently encompasses approximately 200.000 adolescents aged 14 to 21 yrs. Conventional approaches focusing on weight reduction have largely proven futile for them. In addition, only a small percentage of adolescents with extreme obesity seek actively treatment for obesity while contributing disproportionately strong to health care costs. Because of somatic and psychiatric co-morbidities and social problems adolescents with extreme obesity require special attention within the medical care system. We have initiated the project “Medical and psychosocial implications of adolescents with extreme obesity - acceptance and effects of structured care, short: ‘Youths with Extreme Obesity Study (YES)’”, which aims at improving the medical care and social support structures for youths with extreme obesity in Germany. Methods/Design We focus on identification of these subjects (baseline examination) and their acceptance of diagnostic and subsequent treatment procedures. In a randomized controlled trial (RCT) we will investigate the effectiveness of a low key group intervention not focusing on weight loss but aimed at the provision of obesity related information, alleviation of social isolation, school and vocational integration and improvement of self-esteem in comparison to a control group treated in a conventional way with focus on weight loss. Interested individuals who fulfill current recommended criteria for weight loss surgery will be provided with a structured preparation and follow-up programs. All subjects will be monitored within a long-term observational study to

  16. Propagation of an ultimately short electromagnetic pulse in a nonlinear medium described by the fifth-order Duffing model

    Science.gov (United States)

    Maĭmistov, A. I.

    2003-02-01

    We discuss propagation of an ultimately short (single-cycle) pulse of an electromagnetic field in a medium whose dispersion and nonlinear properties can be described by the cubic-quintic Duffing model, i.e., by an oscillator with third-and fifth-order anharmonicity. A system of equations governing the evolution of a unidirectional electromagnetic wave is analyzed without using the approximation of slowly varying envelopes. Three types of solutions of this system describing stationary propagation of a pulse in such a medium are found. When the signs of the anharmonicity constants are different, then the amplitude of a steady-state pulse is limited, but its energy may grow on account of an increase in its duration. The characteristics of such a pulse, referred to as an electromagnetic domain, are discussed.

  17. Pulse wave transit time measured by imaging photoplethysmography in upper extremities

    Science.gov (United States)

    Volynsky, M. A.; Mamontov, O. V.; Sidorov, I. S.; Kamshilin, A. A.

    2016-08-01

    We describe highly reliable measurement method of the pulse wave transit time (PWTT) to human limbs by using simultaneous recordings of imaging photoplethysmography and electrocardiography. High accuracy of measurements was achieved by access to a larger number of statistically independent data obtained simultaneously in different points. The method is characterized by higher diagnostic reliability because of automatic selection of the regions less affected by environmental noise. The technique was tested in the group of 12 young healthy subjects aged from 21 to 33 years. Even though PWTT in right and left hands was comparable after averaging over the whole group of subjects, significant difference in the time delay of pulse wave between the hands was found in several individuals. The technique can be used for early-stage diagnostics of various vascular diseases.

  18. Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field

    Science.gov (United States)

    Saito, Nariyuki; Ishii, Nobuhisa; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

    2016-01-01

    Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6–based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy. PMID:27752115

  19. Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field

    Science.gov (United States)

    Saito, Nariyuki; Ishii, Nobuhisa; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

    2016-10-01

    Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6-based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy.

  20. Extremely short duration high intensity interval training substantially improves insulin action in young healthy males

    DEFF Research Database (Denmark)

    Babraj, John A; Vollaard, Niels B J; Keast, Cameron

    2009-01-01

    BACKGROUND: Traditional high volume aerobic exercise training reduces cardiovascular and metabolic disease risk but involves a substantial time commitment. Extremely low volume high-intensity interval training (HIT) has recently been demonstrated to produce improvements to aerobic function, but i...

  1. Probing Pulsar Emission on Short Timescales: Rotating Radio Transients, Cyclic Spectroscopy, and Single-Pulse Studies of Millisecond Pulsars

    Science.gov (United States)

    Palliyaguru, Nipuni Tharaka

    Rotating radio transients (RRATs) are neutron stars are that characterized by the emission of strong sporadic bursts. We have analysed the long- and short-term time dependence of the pulse arrival times and the pulse detection rates for eight RRAT sources from the Parkes Multi-beam Pulsar Survey (PMPS). We find significant periodicities in the individual pulse arrival times from six RRATs. These periodicities range from ˜30 minutes to 2100 days and from one to 16 independent (i.e. non-harmonically related) periodicities are detected for each RRAT. In addition, we find that pulse emission is a random process on short (hour-long) time scales but that most of the objects exhibit longer term (months-years) non-random behaviour. We find that PSRs J1819--1458 and J1317--5759 emit more doublets (two consecutive pulses) and triplets (three consecutive pulses) than is expected in random pulse distributions. No evidence for such an excess is found for the other RRATs. There are several different models for RRAT emission depending on both extrinsic and intrinsic factors which are consistent with these properties. Light travel time changes due to gravitational waves may be detected within the next decade through precision timing of an array of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOAs) for time-variable delays due to cold plasma dispersion. However, none of the major pulsar timing groups routinely correct for delays due to scattering from multi-path propagation in the ISM. Scattering introduces a phase change in the signal that results in pulse broadening and arrival time delays. As a step toward a more comprehensive ISM propagation delay correction, we demonstrate through a simulation that we can accurately recover pulse broadening functions (PBFs), such as those that would be introduced

  2. Robust Short-Pulse, High-Peak-Power Laser Transmitter for Optical Communications

    Science.gov (United States)

    Wright, Malcolm W.

    2009-01-01

    We report on a pulsed fiber based master oscillator power amplifier laser at 1550 nm to support moderate data rates with high peak powers in a compact package suitable for interplanetary optical communications. To accommodate pulse position modulation, the polarization maintaining laser transmitter generates pulses from 0.1 to 1 ns with variable duty cycle over a pulse repetition frequency range of 10 to 100 MHz.

  3. Generating ultra-short energetic pulses with cascaded soliton compression in lithium niobate crystals

    DEFF Research Database (Denmark)

    Zhou, Binbin; Bache, Morten; Chong, A.;

    2010-01-01

    By launching energetic femtosecond pulses in a lithium niobate crystal, the phase mismatched second-harmonic generation process compresses the 50 fs input pulse at 1250 nm to 30 fs through a soliton effect.......By launching energetic femtosecond pulses in a lithium niobate crystal, the phase mismatched second-harmonic generation process compresses the 50 fs input pulse at 1250 nm to 30 fs through a soliton effect....

  4. Plasma-blueshift spectral shear interferometry for characterization of ultimately short optical pulses.

    Science.gov (United States)

    Verhoef, Aart J; Mitrofanov, Alexander; Zheltikov, Aleksei; Baltuska, Andrius

    2009-01-01

    We introduce a bandwidth-unlimited, dispersion- and shear-self-calibrated, timing-jitter-free pulse measurement technique based on a quasi-linear temporal phase modulation in a gas weakly ionized by a long pump pulse. Results of a 5 fs pulse characterization are reported.

  5. Resistance and recovery of river biofilms receiving short pulses of Triclosan and Diuron.

    Science.gov (United States)

    Proia, L; Morin, S; Peipoch, M; Romaní, A M; Sabater, S

    2011-08-01

    The effects of the herbicide Diuron (DIU) and the bactericide Triclosan (TCS) were assessed on laboratory-grown stream biofilms. Four week-old biofilms were exposed in mesocosms to 48-hours of short pulses of either DIU or TCS. The direct and indirect effects of each toxicant on the biofilms, and the subsequent recovery of the biofilms, were evaluated according to structural and functional biomarkers. These parameters were analyzed immediately before exposure, immediately after exposure, and 9 and 16days post-exposure. DIU caused an increase in diatom mortality (+79%), which persisted until the end of the experiment. TCS also affected diatom mortality (+41%), although the effect did not appear until 1week post-exposure. TCS caused an increase in bacterial mortality (+45%); however, this parameter returned to normal values 1week post-exposure. TCS compromised the cellular integrity of the green alga Spirogyra sp., whereas DIU did not. TCS also strongly inhibited phosphate uptake (-71%), which did not return to normal values until 2weeks post-exposure. DIU directly affected algae, but barely affected the heterotrophs, whereas TCS seriously impaired bacteria (direct effect) as well as autotrophs (indirect effect). However, the biofilms recovered their normal structure and function within only a few days to a few weeks. These findings demonstrate the capacity of biofilms to cope with periodic inputs of toxicants, but also the risks associated to repeated exposure or multi-contamination in aquatic ecosystems.

  6. Thermal interaction of short-pulsed laser focused beams with skin tissues

    Energy Technology Data Exchange (ETDEWEB)

    Jiao Jian; Guo Zhixiong [Department of Mechanical and Aerospace Engineering, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States)], E-mail: guo@jove.rutgers.edu

    2009-07-07

    Time-dependent thermal interaction is developed in a skin tissue cylinder subjected to the irradiation of a train of short laser pulses. The skin embedded with a small tumor is stratified as three layers: epidermis, dermis and subcutaneous fat with different optical, thermal and physiological properties. The laser beam is focused to the tumor site by an objective lens for thermal therapy. The ultrafast radiation heat transfer of the focused beam is simulated by the transient discrete ordinates method. The transient Pennes bio-heat equation is solved numerically by the finite volume method with alternating direction implicit scheme. Emphasis is placed on the characterization of the focused beam propagation and absorption and the temperature rise in the focal spot. The effects of the focal spot size and location, the laser power, and the bio-heat equation are investigated. Comparisons with collimated irradiation are conducted. The focused beam can penetrate a greater depth and produce higher temperature rise at the target area, and thus reduce the possibility of thermal damage to the surrounding healthy tissue. It is ideal for killing cancerous cells and small tumors.

  7. Thermal interaction of short-pulsed laser focused beams with skin tissues

    Science.gov (United States)

    Jiao, Jian; Guo, Zhixiong

    2009-07-01

    Time-dependent thermal interaction is developed in a skin tissue cylinder subjected to the irradiation of a train of short laser pulses. The skin embedded with a small tumor is stratified as three layers: epidermis, dermis and subcutaneous fat with different optical, thermal and physiological properties. The laser beam is focused to the tumor site by an objective lens for thermal therapy. The ultrafast radiation heat transfer of the focused beam is simulated by the transient discrete ordinates method. The transient Pennes bio-heat equation is solved numerically by the finite volume method with alternating direction implicit scheme. Emphasis is placed on the characterization of the focused beam propagation and absorption and the temperature rise in the focal spot. The effects of the focal spot size and location, the laser power, and the bio-heat equation are investigated. Comparisons with collimated irradiation are conducted. The focused beam can penetrate a greater depth and produce higher temperature rise at the target area, and thus reduce the possibility of thermal damage to the surrounding healthy tissue. It is ideal for killing cancerous cells and small tumors.

  8. Bremsstrahlung measurements for characterization of intense short-pulse, laser produced fast electrons with OMEGA EP

    Science.gov (United States)

    Daykin, Tyler; Sawada, Hiroshi; Sentoku, Yasuhiko; Pandit, Rishi; Chen, Cliff; Beg, Farhat; Chen, Hui; McLean, Harry; Patel, Pravesh; Tommasini, Riccardo

    2016-10-01

    Understanding relativistic fast electron generation and transport inside solids is important for applications such as generation of high energy x-ray sources and fast ignition. An experiment was carried out to study the scaling of the fast electron spectrum and bremsstrahlung generation in multi-pico second laser interactions using 1 ps and 10 ps OMEGA EP short-pulse beam to generate fast electrons at a similar peak intensity of 5x1018 W/cm2. The bremsstrahlung produced by collisions of the fast electrons with background ions was recorded using differential filter stacked spectrometers. A preliminary analysis with a Monte Carlo Code ITS shows that the electrons injection having an electron slope 1.8 MeV matched well with the high energy component of the 1 ps and 10 ps bremsstrahlung measurements. Details of the data analysis and modeling with Monte Carlo and a hybrid particle-in-cell codes will be presented at the conference. Work supported by the UNR Office of the Provost and by DOE/OFES under Contract No. DE-SC0008827. This collaborative work was partially supported under the auspices of the US DOE by LLNL under Contracts No. DE-AC52-07NA27344 and No. DE-FG-02-05ER54834.

  9. The implementation and data analysis of an interferometer for intense short pulse laser experiments

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jaebum; Baldis, Hector A.; Chen, Hui

    2016-01-01

    We present an interferometry setup and the detailed fringe analysis method for intense short pulse (SP) laser experiments. The interferometry scheme was refined through multiple campaigns to investigate the effects of pre-plasmas on energetic electrons at the Jupiter Laser Facility at Lawrence Livermore National Laboratory. The interferometer used a frequency doubled (${\\it\\lambda}=0.527~{\\rm\\mu}\\text{m}$) 0.5 ps long optical probe beam to measure the pre-plasma density, an invaluable parameter to better understand how varying pre-plasma conditions affect the characteristics of the energetic electrons. The hardware of the diagnostic, data analysis and example data are presented. The diagnostic setup and the analysis procedure can be employed for any other SP laser experiments and interferograms, respectively.

  10. Molecular dynamics induced by short and intense x-ray pulses from the LCLS

    Science.gov (United States)

    Berrah, Nora

    2016-12-01

    The past six years have led to a wealth of experimental and theoretical data revealing the nature of the interaction between gas-phase molecules and short and intense x-ray pulses, from the Linac coherent light source free electron laser (FEL). We present here a few highlights that describe some of the first photoabsorption measurements of gas-phase molecules. In particular, we report on a three decades long prediction of single-site double core holes (ss-DCH) and two-site double core holes (ts-DCH) in diatomic and triatomic molecules. We also describe recent measurements that validate a simple theory regarding femtosecond intense x-ray induced fragmentation dynamics of C60 as well as photoabsorption measurements of encapsulated fullerenes, Ho3N@C80. The latter investigation opens the way for even more complex molecular studies with FELs. In all of the described highlights, working in close collaboration with theorists enabled the interpretation of, or predicted our measurements, and in some cases our experiments guided the modeling. We conclude this article by describing the potential of new instrumentation for chemical and biological sciences especially in light of new or improved FELs.

  11. Short pulse generation and mode control of broadband terahertz quantum cascade lasers

    CERN Document Server

    Bachmann, Dominic; Süess, Martin J; Beck, Mattias; Unterrainer, Karl; Darmo, Juraj; Faist, Jérôme; Scalari, Giacomo

    2016-01-01

    We report on a waveguide engineering technique that enables the generation of a bandwidth up to 1 THz and record ultra-short pulse length of 2.5 ps in injection seeded terahertz quantum cascade lasers. The reported technique is able to control and fully suppress higher order lateral modes in broadband terahertz quantum cascade lasers by introducing side-absorbers to metal-metal waveguides. The side-absorbers consist of a top metalization set-back with respect to the laser ridge and an additional lossy metal layer. In continuous wave operation the side-absorbers lead to octave spanning laser emission, ranging from 1.63 to 3.37 THz, exhibiting a 725 GHz wide at top within a 10 dB intensity range as well as frequency comb operation with a bandwidth of 442 GHz. Numerical and experimental studies have been performed to optimize the impact of the side-absorbers on the emission properties and to determine the required increase of waveguide losses. Furthermore, these studies have led to a better understanding of the ...

  12. 2nd International Conference on Ultra-Wideband, Short-Pulse Electromagnetics

    CERN Document Server

    Felsen, Leopold

    1995-01-01

    The papers published in this volume were presented at the Second International Conference on Ultra-WidebandiShort-Pulse (UWB/SP) Electromagnetics, ApriIS-7, 1994. To place this second international conference in proper perspective with respect to the first conference held during October 8-10, 1992, at Polytechnic University, some background information is necessary. As we had hoped, the first conference struck a responsive cord, both in timeliness and relevance, among the electromagnetic community 1. Participants at the first conference already inquired whether and when a follow-up meeting was under consideration. The first concrete proposal in this direction was made a few months after the first conference by Prof. A. Terzuoli of the Air Force Institute of Technology (AFIT), Dayton, Ohio, who has been a strong advocate of time-domain methods and technologies. He initially proposed a follow-up time-domain workshop under AFIT auspices. Realizing that interest in this subject is lodged also at other Air Force i...

  13. Plasma processes in water under effect of short duration pulse discharges

    Science.gov (United States)

    Gurbanov, Elchin

    2013-09-01

    It is very important to get a clear water without any impurities and bacteria by methods, that don't change the physical and chemical indicators of water now. In this article the plasma processes during the water treatment by strong electric fields and short duration pulse discharges are considered. The crown discharge around an electrode with a small radius of curvature consists of plasma leader channels with a high conductivity, where the thermo ionization processes and UV-radiation are taken place. Simultaneously the partial discharges around potential electrode lead to formation of atomic oxygen and ozone. The spark discharge arises, when plasma leader channels cross the all interelectrode gap, where the temperature and pressure are strongly grown. As a result the shock waves and dispersing liquid streams in all discharge gap are formed. The plasma channels extend, pressure inside it becomes less than hydrostatic one and the collapse and UV-radiation processes are started. The considered physical processes can be successfully used as a basis for development of pilot-industrial installations for conditioning of drinking water and to disinfecting of sewage.

  14. Repetitive short-pulse light mainly inactivates photosystem I in sunflower leaves.

    Science.gov (United States)

    Sejima, Takehiro; Takagi, Daisuke; Fukayama, Hiroshi; Makino, Amane; Miyake, Chikahiro

    2014-06-01

    Under field conditions, the leaves of plants are exposed to fluctuating light, as observed in sunfleck. The duration and frequency of sunfleck, which is caused by the canopy being blown by the wind, are in the ranges from 0.2 to 50 s, and from 0.004 to 1 Hz, respectively. Furthermore, >60% of the sunfleck duration ranges from 0.2 to 0.8 s. In the present research, we analyzed the effects of repetitive illumination by short-pulse (SP) light of sunflower leaves on the photosynthetic electron flow. The duration of SP light was set in the range from 10 to 300 ms. We found that repetitive illumination with SP light did not induce the oxidation of P700 in PSI, and mainly inactivated PSI. Increases in the intensity, duration and frequency of SP light enhanced PSI photoinhibition. PSI photoinhibition required the presence of O2. The inactivation of PSI suppressed the net CO2 assimilation. On the other hand, the increase in the oxidized state of P700 suppressed PSI inactivation. That is, PSI with a reduced reaction center would produce reactive oxygen species (ROS) by SP light, leading to PSI photodamage. This mechanism probably explains the PSI photodamage induced by constant light. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  15. Theoretical analysis of saturation and limit cycles in short pulse FEL oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Piovella, N.; Chaix, P.; Jaroszynski, D. [Commissariat a l`Energie Atomique, Bruyeres-le-Chatel (France)] [and others

    1995-12-31

    We derive a model for the non linear evolution of a short pulse oscillator from low signal up to saturation in the small gain regime. This system is controlled by only two independent parameters: cavity detuning and losses. Using a closure relation, this model reduces to a closed set of 5 non linear partial differential equations for the EM field and moments of the electron distribution. An analysis of the linearised system allows to define and calculate the eigenmodes characterising the small signal regime. An arbitrary solution of the complete nonlinear system can then be expanded in terms of these eigenmodes. This allows interpreting various observed nonlinear behaviours, including steady state saturation, limit cycles, and transition to chaos. The single mode approximation reduces to a Landau-Ginzburg equation. It allows to obtain gain, nonlinear frequency shift, and efficiency as functions of cavity detuning and cavity losses. A generalisation to two modes allows to obtain a simple description of the limit cycle behaviour, as a competition between these two modes. An analysis of the transitions to more complex dynamics is also given. Finally, the analytical results are compared to the experimental data from the FELIX experiment.

  16. Extremely short relativistic-electron-bunch generation in the laser wakefield via novel bunch injection scheme

    NARCIS (Netherlands)

    Khachatryan, A.G.; Goor, van F.A.; Boller, K.-J.; Reitsma, A.J.W.; Jaroszynski, D.A.

    2004-01-01

    Recently a new electron-bunch injection scheme for the laser wakefield accelerator has been proposed [JETP Lett. 74, 371 (2001); Phys. Rev. E 65, 046504 (2002)]. In this scheme, a low energy electron bunch, sent in a plasma channel just before a high-intensity laser pulse, is trapped in the laser wa

  17. Ultra-short laser-accelerated proton pulses have similar DNA-damaging effectiveness but produce less immediate nitroxidative stress than conventional proton beams

    Science.gov (United States)

    Raschke, S.; Spickermann, S.; Toncian, T.; Swantusch, M.; Boeker, J.; Giesen, U.; Iliakis, G.; Willi, O.; Boege, F.

    2016-08-01

    Ultra-short proton pulses originating from laser-plasma accelerators can provide instantaneous dose rates at least 107-fold in excess of conventional, continuous proton beams. The impact of such extremely high proton dose rates on A549 human lung cancer cells was compared with conventionally accelerated protons and 90 keV X-rays. Between 0.2 and 2 Gy, the yield of DNA double strand breaks (foci of phosphorylated histone H2AX) was not significantly different between the two proton sources or proton irradiation and X-rays. Protein nitroxidation after 1 h judged by 3-nitrotyrosine generation was 2.5 and 5-fold higher in response to conventionally accelerated protons compared to laser-driven protons and X-rays, respectively. This difference was significant (p DNA damaging potential as conventional proton beams, while inducing less immediate nitroxidative stress, which probably entails a distinct therapeutic potential.

  18. Multiple Ionization of Free Ubiquitin Molecular Ions in Extreme Ultraviolet Free-Electron Laser Pulses.

    Science.gov (United States)

    Schlathölter, Thomas; Reitsma, Geert; Egorov, Dmitrii; Gonzalez-Magaña, Olmo; Bari, Sadia; Boschman, Leon; Bodewits, Erwin; Schnorr, Kirsten; Schmid, Georg; Schröter, Claus Dieter; Moshammer, Robert; Hoekstra, Ronnie

    2016-08-26

    The fragmentation of free tenfold protonated ubiquitin in intense 70 femtosecond pulses of 90 eV photons from the FLASH facility was investigated. Mass spectrometric investigation of the fragment cations produced after removal of many electrons revealed fragmentation predominantly into immonium ions and related ions, with yields increasing linearly with intensity. Ionization clearly triggers a localized molecular response that occurs before the excitation energy equilibrates. Consistent with this interpretation, the effect is almost unaffected by the charge state, as fragmentation of sixfold deprotonated ubiquitin leads to a very similar fragmentation pattern. Ubiquitin responds to EUV multiphoton ionization as an ensemble of small peptides.

  19. Improving Switching Performance of Power MOSFETs Used in High Rep-Rate, Short Pulse, High-Power Pulsers

    Energy Technology Data Exchange (ETDEWEB)

    Cook, E G

    2006-09-19

    As their switching and power handling characteristics improve, solid-state devices are finding new applications in pulsed power. This is particularly true of applications that require fast trains of short duration pulses. High voltage (600-1200V) MOSFETs are especially well suited for use in these systems, as they can switch at significant peak power levels and are easily gated on and off very quickly. MOSFET operation at the shortest pulse durations is not constrained by the intrinsic capabilities of the MOSFET, but rather by the capabilities of the gate drive circuit and the system physical layout. This project sought to improve MOSFET operation in a pulsed power context by addressing these issues. The primary goal of this project is to improve the switching performance of power MOSFETs for use in high rep-rate, short pulse, high-power applications by improving the design of the gate drive circuits and the circuit layouts used in these systems. This requires evaluation of new commercial gate drive circuits and upgrading the designs of LLNL-developed circuits. In addition, these circuits must be tested with the fastest available high-voltage power MOSFETs.

  20. Vaporization and recondensation dynamics of indocyanine green-loaded perfluoropentane droplets irradiated by a short pulse laser

    Science.gov (United States)

    Yu, Jaesok; Chen, Xucai; Villanueva, Flordeliza S.; Kim, Kang

    2016-12-01

    Phase-transition droplets have been proposed as promising contrast agents for ultrasound and photoacoustic imaging. Short pulse laser activated perfluorocarbon-based droplets, especially when in a medium with a temperature below their boiling point, undergo phase changes of vaporization and recondensation in response to pulsed laser irradiation. Here, we report and discuss the vaporization and recondensation dynamics of perfluoropentane droplets containing indocyanine green in response to a short pulsed laser with optical and acoustic measurements. To investigate the effect of temperature on the vaporization process, an imaging chamber was mounted on a temperature-controlled water reservoir and then the vaporization event was recorded at 5 million frames per second via a high-speed camera. The high-speed movies show that most of the droplets within the laser beam area expanded rapidly as soon as they were exposed to the laser pulse and immediately recondensed within 1-2 μs. The vaporization/recondensation process was consistently reproduced in six consecutive laser pulses to the same area. As the temperature of the media was increased above the boiling point of the perfluoropentane, the droplets were less likely to recondense and remained in a gas phase after the first vaporization. These observations will help to clarify the underlying processes and eventually guide the design of repeatable phase-transition droplets as a photoacoustic imaging contrast agent.

  1. 2D positive streamer modelling in NTP air under extreme pulse fronts. What about runaway electrons?

    Science.gov (United States)

    Marode, E.; Dessante, Ph; Tardiveau, P.

    2016-12-01

    Using a 2D model, an attempt is made to understand the properties and aspects of a diffuse discharge, appearing in a positive point-to-plane gap submitted to very high voltage pulses. After presenting the model, comparisons between the computed low and high pulse heights of 10 kV and 50 kV, respectively, will be shown and analysed. A streamer ionising wave is still formed, but its role in ionising a region of low field is replaced by the role of providing a plasma within which the electrons will benefit from the presence of a high electrical field meant to induce strong electron collision activities. A comparison between the aspect of the computed and experimental discharge carried out in the same conditions at 50 kV will be presented, which seems to be in agreement with the diffuse aspect. Although the difference in order of magnitude of the speed of development and the height of the current must be underlined, similarities between the structures of both situations will, however, be recognised. A high probability of obtaining highly energetic electrons and runaways (RAEs) will also be derived following a simple approach.

  2. All-optical wavelength conversion of short pulses and NRZ signals based on a nonlinear optical loop mirror

    DEFF Research Database (Denmark)

    Yu, Jianjun; Zheng, Xueyan; Peucheret, Christophe

    2000-01-01

    Wavelength conversion of short pulses at 10 GHz based on a nonlinear optical loop mirror (NOLM) is experimentally and numerically investigated for the case of small group velocity dispersion and walkoff between the control pulses and continuous lightwaves. Experimental and numerical simulation......, equal amplitudes and almost the same pulsewidths is obtained by using wavelength conversion in a NOLM consisting of a common dispersion shifted fiber. 10 Gb/s NRZ wavelength conversion based on the NOLM is demonstrated for the first time and certain conclusions in some of the references are confirmed...

  3. Two-dimensional angular energy spectrum of electrons accelerated by the ultra-short relativistic laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Borovskiy, A. V. [Department of Computer Science and Cybernetics, Baikal State University of Economics and Law, 11 Lenin Street, Irkutsk 664003 (Russian Federation); Galkin, A. L. [Coherent and Nonlinear Optics Department, A.M. Prokhorov General Physics Institute of the RAS, 38 Vavilov Street, Moscow 119991 (Russian Federation); Department of Physics of MBF, Pirogov Russian National Research Medical University, 1 Ostrovitianov Street, Moscow 117997 (Russian Federation); Kalashnikov, M. P., E-mail: galkin@kapella.gpi.ru [Max-Born-Institute for Nonlinear Optics and Short-Time Spectroscopy, 2a Max-Born-Strasse, Berlin 12489 (Germany)

    2015-04-15

    The new method of calculating energy spectra of accelerated electrons, based on the parameterization by their initial coordinates, is proposed. The energy spectra of electrons accelerated by Gaussian ultra-short relativistic laser pulse at a selected angle to the axis of the optical system focusing the laser pulse in a low density gas are theoretically calculated. The two-peak structure of the electron energy spectrum is obtained. Discussed are the reasons for its appearance as well as an applicability of other models of the laser field.

  4. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    Science.gov (United States)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  5. Evolution of hole shape and size during short and ultrashort pulse laser deep drilling.

    Science.gov (United States)

    Döring, Sven; Szilagyi, John; Richter, Sören; Zimmermann, Felix; Richardson, Martin; Tünnermann, Andreas; Nolte, Stefan

    2012-11-19

    A detailed study of the influence of the pulse duration, from the femtosecond to the nanosecond regime, on the evolution of the hole shape and depth during percussion drilling in silicon is presented. Real-time backlight imaging of the hole development is obtained for holes up to 2 mm deep with aspect ratios extending to 25:1. For low pulse energies, the hole-shape and drilling characteristics are similar for femtosecond, picoseconds and nanosecond regimes. At higher pulse energies, ns-pulses exhibit slower average drilling rates but eventually reach greater final depths. The shape of these holes is however dominated by branching and large internal cavities. For ps-pulses, a cylindrical shape is maintained with frequent small bulges on the side-walls. In contrast, fs-pulses cause only a limited number of imperfections on a tapered hole shape.

  6. Optimal Design and Experimental characterisation of short optical pulse compression using CDPF

    DEFF Research Database (Denmark)

    Yujun, Qian; Quist, S.

    1999-01-01

    We present optimal design and experimental characterisation ofoptical pulse compression using a comblike dispersion-profiled fibre(CDPF). A pulse train at 10GHz with puslewidth of 1ps and side-lobesuppression of 30dB can be obtained.......We present optimal design and experimental characterisation ofoptical pulse compression using a comblike dispersion-profiled fibre(CDPF). A pulse train at 10GHz with puslewidth of 1ps and side-lobesuppression of 30dB can be obtained....

  7. Alignment enhancement of a symmetric top molecule by two short laser pulses

    DEFF Research Database (Denmark)

    Bisgaard, Christer Z; Viftrup, Simon; Stapelfeldt, Henrik

    2006-01-01

    The alignment dynamics of a symmetric top molecule, tert-butyliodide, induced by two picosecond, nonresonant, linearly polarized pulses is studied experimentally and numerically using a combination of time-resolved photofragment imaging and nonperturbative solution of the time-dependent Schrodinger...... equation. It is shown that the strongest degree of one-dimensional (single axis) field-free alignment obtainable with a single pulse can be enhanced using the two-pulse sequence in a parallel polarization geometry. The conditions for alignment enhancement are: (1) The second pulse must be sent near...

  8. Short X-ray pulses from third-generation light sources.

    Science.gov (United States)

    Stepanov, A G; Hauri, C P

    2016-01-01

    High-brightness X-ray radiation produced by third-generation synchrotron light sources (TGLS) has been used for numerous time-resolved investigations in many different scientific fields. The typical time duration of X-ray pulses delivered by these large-scale machines is about 50-100 ps. A growing number of time-resolved studies would benefit from X-ray pulses with two or three orders of magnitude shorter duration. Here, techniques explored in the past for shorter X-ray pulse emission at TGLS are reviewed and the perspective towards the realisation of picosecond and sub-picosecond X-ray pulses are discussed.

  9. A Hybrid Short-Term Traffic Flow Prediction Model Based on Singular Spectrum Analysis and Kernel Extreme Learning Machine.

    Science.gov (United States)

    Shang, Qiang; Lin, Ciyun; Yang, Zhaosheng; Bing, Qichun; Zhou, Xiyang

    2016-01-01

    Short-term traffic flow prediction is one of the most important issues in the field of intelligent transport system (ITS). Because of the uncertainty and nonlinearity, short-term traffic flow prediction is a challenging task. In order to improve the accuracy of short-time traffic flow prediction, a hybrid model (SSA-KELM) is proposed based on singular spectrum analysis (SSA) and kernel extreme learning machine (KELM). SSA is used to filter out the noise of traffic flow time series. Then, the filtered traffic flow data is used to train KELM model, the optimal input form of the proposed model is determined by phase space reconstruction, and parameters of the model are optimized by gravitational search algorithm (GSA). Finally, case validation is carried out using the measured data of an expressway in Xiamen, China. And the SSA-KELM model is compared with several well-known prediction models, including support vector machine, extreme learning machine, and single KLEM model. The experimental results demonstrate that performance of the proposed model is superior to that of the comparison models. Apart from accuracy improvement, the proposed model is more robust.

  10. Electron acceleration in vacuum by a linearly-polarized ultra-short tightly-focused THz pulse

    Science.gov (United States)

    Salamin, Yousef I.

    2017-09-01

    The analytic expressions for the electric and magnetic fields of an ultra-short, tightly-focused, linearly-polarized laser pulse propagating in vacuum, derived elsewhere (Salamin, 2015) [13] to lowest-order of a truncated power-series expansion from vector and scalar potentials, are employed here for single electron acceleration calculations by THz radiation. It is shown that, while currently available THz peak powers cannot accelerate electrons appreciably, yet they result in substantial energy gradients. The field equations are used to show that an electron can be accelerated, in vacuum, from rest to 4.83 MeV by interaction with a single THz pulse of 1 TW power. Similarly, a 1 GW power pulse focused to sub-wavelength waist radius at focus is shown to accelerate the electron from rest to 5.76 keV.

  11. Consequences of extreme life history traits on population persistence: do short-lived gobies face demographic bottlenecks?

    Science.gov (United States)

    Lefèvre, Carine D.; Nash, Kirsty L.; González-Cabello, Alonso; Bellwood, David R.

    2016-06-01

    The majority of coral reef goby species are short-lived, with some highly abundant species living less than 100 d. To understand the role and consequences of this extreme life history in shaping coral reef fish populations, we quantitatively documented the structure of small reef fish populations over a 26-month period (>14 short-lived fish generations) at an inshore reef on the Great Barrier Reef, Australia. Most species with life spans >1 yr, such as pomacentrids, exhibited a peak in recruitment during the austral summer, driving seasonal changes in the small fish community composition. In contrast, there were no clear changes in goby community composition, despite the abundance of short-lived, high turnover species. Species of Eviota, the most abundant gobiid genus observed, showed remarkably similar demographic profiles year-round, with consistent densities of adults as well as recently recruited juveniles. Our results demonstrate ongoing recruitment of these small cryptic fishes, which appears to compensate for an exceptionally short life span on the reef. Our results suggest that gobiid populations are able to overcome demographic limitations, and by maintaining reproduction, larval survival and recruitment throughout the year, they may avoid population bottlenecks. These findings also underline the potential trophodynamic importance of these small species; because of this constant turnover, Eviota species and other short-lived fishes may be particularly valuable contributors to the flow of energy on coral reefs, underpinning the year-round trophic structure.

  12. Short-Term Physical and Mental Health Outcomes for Combat Amputee and Nonamputee Extremity Injury Patients

    Science.gov (United States)

    2012-01-01

    16 5.8 Pulmonary embolism± 27 7.1 11 4.0 *Percentages for amputee group . extremity group (P , 0.05). †P , 0.08. PLS, phantom limb syndrome; ±, deep...consistent with previous research.9,11 Absolute rates of other complications ( phantom limb syndrome, osteomyelitis, and infections) were consistent...Amputees had significantly greater odds of certain mental health disorders including mood, sleep, pain , and postconcussion syndrome. However, ampu- tees

  13. Comparative effects of extremely high power microwave pulses and a brief CW irradiation on pacemaker function in isolated frog heart slices.

    Science.gov (United States)

    Pakhomov, A G; Mathur, S P; Doyle, J; Stuck, B E; Kiel, J L; Murphy, M R

    2000-05-01

    The existence of specific bioeffects due to high peak power microwaves and their potential health hazards are among the most debated but least explored problems in microwave biology. The present study attempted to reveal such effects by comparing the bioeffects of short trains of extremely high power microwave pulses (EHPP, 1 micros width, 250-350 kW/g, 9.2 GHz) with those of relatively low power pulses (LPP, 0.5-10 s width, 3-30 W/g, 9.2 GHz). EHPP train duration and average power were made equal to those of an LPP; therefore both exposure modalities produced the same temperature rise. Bioeffects were studied in isolated, spontaneously beating slices of the frog heart. In most cases, a single EHPP train or LPP immediately decreased the inter-beat interval (IBI). The effect was proportional to microwave heating, fully reversible, and easily reproducible. The magnitude and time course of EHPP- and LPP-induced changes always were the same. No delayed or irreversible effects of irradiation were observed. The same effect could be repeated in a single preparation numerous times with no signs of adaptation, sensitization, lasting functional alteration, or damage. A qualitatively different effect, namely, a temporary arrest of preparation beats, could be observed when microwave heating exceeded physiologically tolerable limits. This effect also did not depend on whether the critical temperature rise was produced by LPP or EHPP exposure. Within the studied limits, we found no indications of EHPP-specific bioeffects. EHPP- and LPP-induced changes in the pacemaker rhythm of isolated frog heart preparation were identical and could be entirely attributed to microwave heating.

  14. A comprehensive model of gain recovery due to unipolar electron transport after a short optical pulse in quantum cascade lasers

    Science.gov (United States)

    Jamali Mahabadi, S. E.; Hu, Yue; Talukder, Muhammad Anisuzzaman; Carruthers, Thomas F.; Menyuk, Curtis R.

    2016-10-01

    We have developed a comprehensive model of gain recovery due to unipolar electron transport after a short optical pulse in quantum cascade lasers (QCLs) that takes into account all the participating energy levels, including the continuum, in a device. This work takes into account the incoherent scattering of electrons from one energy level to another and quantum coherent tunneling from an injector level to an active region level or vice versa. In contrast to the prior work that only considered transitions to and from a limited number of bound levels, this work include transitions between all bound levels and between the bound energy levels and the continuum. We simulated an experiment of S. Liu et al., in which 438-pJ femtosecond optical pulses at the device's lasing wavelength were injected into an I n0.653 Ga0.348 As/In0.310 Al0.690 As QCL structure; we found that approximately 1% of the electrons in the bound energy levels will be excited into the continuum by a pulse and that the probability that these electrons will be scattered back into bound energy levels is negligible, ˜10-4 . The gain recovery that is predicted is not consistent with the experiments, indicating that one or more phenomena besides unipolar electron transport in response to a short optical pulse play an important role in the observed gain recovery.

  15. An experimental study of temperature and moisture content of wet porous materials under short-pulsed laser heating

    Institute of Scientific and Technical Information of China (English)

    Renxi Jin; Xiulan Huai

    2005-01-01

    The measurements of temperature and moisture content of a wet porous material were accomplished on the micro-seconds scale. The temperature wave was observed when the wet porous material was heated by short-pulsed laser with high power. It firstly revealed that the moisture content of wet porous material rapidly rises twice in one laser irradiation. The influences of laser parameters, the thickness and initial moisture content of the wet porous material on its temperature and moisture content were investigated.

  16. Short-term impacts of salinity pulses on ionic ratios of the seagrasses Thalassia testudinum and Halodule wrightii

    OpenAIRE

    Garrote-Moreno, Aurora; McDonald, Ashley; Sherman, Timothy D.; Sánchez-Lizaso, José Luis; Kenneth L. Heck Jr.; Cebrián, Just

    2014-01-01

    We examined the effects of short-term salinity pulses on ion accumulation in the seagrasses Thalassia testudinum and Halodule wrightii. Plant fragments were exposed for approximately 1 week to 10, 23 (ambient salinity), 30, 40, 50 and 70 psu. The concentrations of total ions, Cl− and Na+ increased with higher salinity in leaves and rhizomes of both seagrass species. In contrast, the concentrations of K+ and Ca2+ generally decreased with higher salinity, although the decrease was relatively sm...

  17. Illustration of the Impedance Behaviour of Extremely Low-Profile Coupled Shorted-Patches Antennas for UHF RFID of People

    Directory of Open Access Journals (Sweden)

    Milan Svanda

    2014-01-01

    Full Text Available The recently introduced coupled shorted-patches technique for the design of extremely low-profile UHF RFID tag antennas is used to illustrate the flexibility of selected feeding methods for tuning the antenna input impedance for the complex values required for matching with typical RFID chips. We present parametric studies of the impedance behaviour of dipole-excited and directly excited antennas designed for radiofrequency identification of people in the European UHF frequency band. Our study can significantly facilitate the design of this class of on-body tag antennas.

  18. Transition from interpulse to afterglow plasmas driven by repetitive short-pulse microwaves in a multicusp magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Shail; Sahu, Debaprasad; Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India)

    2012-08-15

    In the power-off phase, plasmas generated by repetitive short-pulse microwaves in a multicusp magnetic field show a transitive nature from interpulse to afterglow as a function of pulse duration t{sub w} = 20-200 {mu}s. The ionized medium can be driven from a highly non equilibrium to an equilibrium state inside the pulses, thereby dictating the behavior of the plasma in the power-off phase. Compared to afterglows, interpulse plasmas observed for t{sub w} < 50 {mu}s are characterized by a quasi-steady-state in electron density that persists for {approx} 20-40 {mu}s even after the end of the pulse and has a relatively slower decay rate ({approx} 4.3 Multiplication-Sign 10{sup 4} s{sup -1}) of the electron temperature, as corroborated by optical measurements. The associated electron energy probability function indicates depletion in low energy electrons which appear at higher energies just after the end of the pulse. The transition occurs at t{sub w} {approx} 50 {mu}s as confirmed by time evolution of integrated electron numbers densities obtained from the distribution function.

  19. Transition from interpulse to afterglow plasmas driven by repetitive short-pulse microwaves in a multicusp magnetic field

    Science.gov (United States)

    Pandey, Shail; Sahu, Debaprasad; Bhattacharjee, Sudeep

    2012-08-01

    In the power-off phase, plasmas generated by repetitive short-pulse microwaves in a multicusp magnetic field show a transitive nature from interpulse to afterglow as a function of pulse duration tw = 20-200 μs. The ionized medium can be driven from a highly non equilibrium to an equilibrium state inside the pulses, thereby dictating the behavior of the plasma in the power-off phase. Compared to afterglows, interpulse plasmas observed for tw < 50 μs are characterized by a quasi-steady-state in electron density that persists for ˜ 20-40 μs even after the end of the pulse and has a relatively slower decay rate (˜ 4.3 × 104 s-1) of the electron temperature, as corroborated by optical measurements. The associated electron energy probability function indicates depletion in low energy electrons which appear at higher energies just after the end of the pulse. The transition occurs at tw ˜ 50 μs as confirmed by time evolution of integrated electron numbers densities obtained from the distribution function.

  20. Decoupling Electronic versus Nuclear Photoresponse of Isolated Green Fluorescent Protein Chromophores Using Short Laser Pulses

    Science.gov (United States)

    Kiefer, Hjalte V.; Pedersen, Henrik B.; Bochenkova, Anastasia V.; Andersen, Lars H.

    2016-12-01

    The photophysics of a deprotonated model chromophore for the green fluorescent protein is studied by femtosecond laser pulses in an electrostatic ion-storage ring. The laser-pulse duration is much shorter than the time for internal conversion, and, hence, contributions from sequential multiphoton absorption, typically encountered with ns-laser pulses, are avoided. Following single-photon excitation, the action-absorption maximum is shown to be shifted within the S0 to S1 band from its origin at about 490 to 450 nm, which is explained by the different photophysics involved in the detected action.

  1. An ultra short pulse reconstruction software applied to the GEMINI high power laser system

    Science.gov (United States)

    Galletti, Mario; Galimberti, Marco; Hooker, Chris; Chekhlov, Oleg; Tang, Yunxin; Bisesto, Fabrizio Giuseppe; Curcio, Alessandro; Anania, Maria Pia; Giulietti, Danilo

    2016-09-01

    The GRENOUILLE traces of Gemini pulses (15 J, 30 fs, PW, shot per 20 s) were acquired in the Gemini Target Area PetaWatt at the Central Laser Facility (CLF), Rutherford Appleton Laboratory (RAL). A comparison between the characterizations of the laser pulse parameters made using two different types of algorithms: Video Frog and GRenouille/FrOG (GROG), was made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign it has been showed how GROG, the developed algorithm, works as well as VideoFrog algorithm with the PetaWatt pulse class.

  2. Antenna Parts and Waveguide Transmission Line of Short Pulse Radar System Design

    Directory of Open Access Journals (Sweden)

    M. E. Golubcov

    2014-01-01

    Full Text Available The main point of this research was работы являлось to create a stand to explore the application of short pulse radio signals in radar. The stand consists of antenna and waveguide elements. Each element out to guarantee operation in X-band with 10 percent working bank and 5 percent instantaneous bandwidth and the power output gotta be 1.5 kW. The form of the antenna beam patten need to be similar to cosecant pattern Side-lobe level need to be less than -25 dB. Background level got to be at least -30 dB. Wave friction, which is radiated from the antenna aperture, got to simultaneous formed in a space.As the most easily realizing variant of such antenna cutting parabolic mirror antenna with offset irradiator was chosen. The irradiator phase centre is shifted from the focal point of the paraboloid to form a cosecant pattern. Method of physical optics is used for the analysis of antennas. Calculating pattern of horn irradiator and mirror antenna which were met the requirements was received. The construction choice was limited by the preproduction possibilities, mass and dimensions. Mirror antenna consists of skeleton framing with mirroring elements which are fixing on it. Mirroring plane is multiplex and consists off rectangular planes made by hydroforming method. Antenna was tested and adjusted at the antenna darkroom after fabricating. The results were meted requirements.Besides the mirror antenna and the horn antenna waveguide elements, waveguide bends and rotating joints were calculated, manufactured and researched. All calculations included the manufacturers tolerances, technological corner R etc. As the construction base of rotating joint coaxial waveguide was chosen. The decision on the one hand: let keep the axial symmetry of excited wave at rotating part of the waveguide, on the other hand there’s no necessary to apply resonant rings, which are plug into dielectric beads for the transition from rotating ring part to

  3. Diode-pumped solid state laser. (Part V). ; Short pulse laser oscillation. Handotai laser reiki kotai laser. 5. ; Tan pulse hasshin

    Energy Technology Data Exchange (ETDEWEB)

    Kuwabara, M.; Bando, N. (Asahi Glass Co. Ltd., Tokyo (Japan))

    1991-12-25

    A semiconductor laser (LD) excited solid state laser using an LD as an excited light source is under discussion for its practical applications to measurements, processing, communications, office automation, and medical areas. This paper describes the discussions given on the short pulse transmission using AOQ switching elements in the LD excited solid state laser with a long wave length band (1.3{mu}m), which is expected of its application in the communications and measurements area. Based on a possibility of raising a measurements resolution by making the pluses in the LD excited solid state laser, and experiments were performed using Nd:YLF as a laser host. as a results, it was found that the smaller the effective mode volume V {sub eff},the smaller the pulse width, and that the ratio of number of initial inversion distribution (N{sub i}/N{sub t}), an important parameter to determine pulse widths, can be obtained from the ratio of the LD exciting light to the input power (P{sub in}/P{sub t}). 7 refs., 14 figs., 2 tabs.

  4. Neutronic studies on decoupled hydrogen moderator for a short-pulse spallation source

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Masahide [Neutron Facility Group, Center for Proton Accelerator Facility, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)]. E-mail: harada@cens.tokai.jaeri.go.jp; Watanabe, Noboru [Neutron Facility Group, Center for Proton Accelerator Facility, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Teshigawara, Makoto [Neutron Facility Group, Center for Proton Accelerator Facility, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Kai, Tetsuya [Neutron Facility Group, Center for Proton Accelerator Facility, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Ikeda, Yujiro [Neutron Facility Group, Center for Proton Accelerator Facility, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

    2005-02-21

    Neutronic studies of decoupled hydrogen moderators were performed by calculations taking into account para hydrogen content, decoupling energy, moderator dimensions/shapes and reflector material. Low-energy parts of calculated spectral intensities with different para hydrogen contents were analyzed by a modified Maxwell function to characterize neutron spectra. The result shows that a 100% para hydrogen moderator gives the highest pulse peak intensity together with the narrowest pulse width and the shortest decay times. Pulse broadening with a reflector was explained by time distributions of source neutrons entering into the moderator through a decoupler. Material dependence of time distribution was studied. A decoupling energy higher than 1 eV does not bring about a large improvement in pulse widths and decay times, even at a large penalty in the peak intensity. The optimal moderator thickness was also discussed for a rectangular parallelepipe-shaped and a canteen-shaped moderator.

  5. Short pulse generation in a passively mode-locked photonic crystal semiconductor laser

    DEFF Research Database (Denmark)

    Heuck, Mikkel; Blaaberg, Søren; Mørk, Jesper

    2010-01-01

    We present a new type of passively mode-locked laser with quantum wells embedded in photonic crystal waveguides operating in the slow light regime, which is capable of emitting sub picosecond pulses with widely controllable properties......We present a new type of passively mode-locked laser with quantum wells embedded in photonic crystal waveguides operating in the slow light regime, which is capable of emitting sub picosecond pulses with widely controllable properties...

  6. Comparative analysis of short and long GPR pulses for landmine detection

    Science.gov (United States)

    Temlioǧlu, Eyyup; Nazlı, Hakkı; Aksoy, Serkan

    2016-05-01

    Ground Penetrating Radar (GPR) is one of the most popular subsurface sensing devices. It has a wide range of applications such as landmine detection, archeological investigations, road condition survey and so on. Hardware and software requirements of the GPR system are strongly dependent on type of applications. Principally, lower frequencies provide deeper penetration and low resolution, but higher frequencies are able to detect shallow objects with high resolution. As a fundamental design criterion, there is a trade-off between penetration depth and vertical resolution. In impulse radar, pulse duration (frequency related) is a key parameter because it affects the system detection performance. Specially, optimization of the pulse duration is a challenging problem for landmine detection because the GPR performance has been strongly affected from mine types, varying terrain and environmental conditions. In this work, two GPR systems with pulse durations of 650 ps and 870 ps are compared for evaluation of their detection performance. The pulses are tested with extensive data sets collected from different soil types by using surrogate mines and other objects. Receiver Operating Characteristic (ROC) curves of the system is also calculated. It seems that the 650 ps pulse duration gives better performance than the 870 ps pulse duration for the shallow landmine detection.

  7. Propagation of two short laser pulse trains in a $\\Lambda$-type three-level medium under conditions of electromagnetically induced transparency

    CERN Document Server

    Buica, Gabriela

    2014-01-01

    We investigate the dynamics of a pair of short laser pulse trains propagating in a medium consisting of three-level $\\Lambda$-type atoms by numerically solving the Maxwell-Schr\\"odinger equations for atoms and fields. By performing propagation calculations with different parameters, under conditions of electromagnetically induced transparency, we compare the propagation dynamics by a single pair of probe and coupling laser pulses and by probe and coupling laser pulse trains. We discuss the influence of the coupling pulse area, number of pulses, and detunings on the probe laser propagation and realization of electromagnetically induced transparency conditions, as well on the formation of a dark state.

  8. Emission Characteristics of Laser-Induced Plasma Using Collinear Long and Short Dual-Pulse Laser-Induced Breakdown Spectroscopy (LIBS).

    Science.gov (United States)

    Wang, Zhenzhen; Deguchi, Yoshihiro; Liu, Renwei; Ikutomo, Akihiro; Zhang, Zhenzhen; Chong, Daotong; Yan, Junjie; Liu, Jiping; Shiou, Fang-Jung

    2017-09-01

    Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.

  9. Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla

    Science.gov (United States)

    Johst, Sören; Maderwald, Stefan; Fischer, Anja; Quick, Harald H.; Ladd, Mark E.; Orzada, Stephan

    2015-01-01

    When performing non-enhanced time-of-flight MR angiography of the lower extremity arteries at 7 T with cardiac triggering, the acquisition time is a crucial consideration. Therefore, in previous studies, saturation RF pulses were applied only every second TR. In the axial source images a slight artifact with an appearance similar to aliasing could be observed. The purpose of this study was to investigate the origin of this artifact. The reason for the artifact is supposed to be related to the two effective TRs during acquisition caused by the sparsely applied saturation RF pulse. Several sequence variants were simulated and implemented within the sequence source code to examine this hypothesis. An adaptation of the excitation flip angles for each TR as well as a correction factor for the k-space data was calculated. Additionally, a different ordering of the k-space data during acquisition was implemented as well as the combination of the latter with the k-space correction factor. The observations from the simulations were verified using both a static and a flow phantom and, finally, in a healthy volunteer using the same measurement setup as in previous volunteer and patient studies. Of all implemented techniques, only the reordering of the k-space was capable of suppressing the artifact almost completely at the cost of creating a ringing artifact. The phantom measurements showed the same results as the simulations and could thus confirm the hypothesis regarding the origin of the artifact. This was additionally verified in the healthy volunteer. The origin of the artifact could be confirmed to be the periodic signal variation caused by two effective TRs during acquisition. PMID:25785837

  10. Using a short-pulse diffraction-limited laser beam to probe filamentation of a random phase plate smoothed beam.

    Science.gov (United States)

    Kline, J L; Montgomery, D S; Flippo, K A; Johnson, R P; Rose, H A; Shimada, T; Williams, E A

    2008-10-01

    A short pulse (few picoseconds) laser probe provides high temporal resolution measurements to elucidate details of fast dynamic phenomena not observable with typical longer laser pulse probes and gated diagnostics. Such a short pulse laser probe (SPLP) has been used to measure filamentation of a random phase plate (RPP) smoothed laser beam in a gas-jet plasma. The plasma index of refraction due to driven density and temperature fluctuations by the RPP beam perturbs the phase front of a SPLP propagating at a 90 degree angle with respect to the RPP interaction beam. The density and temperature fluctuations are quasistatic on the time scale of the SPLP (approximately 2 ps). The transmitted near-field intensity distribution from the SPLP provides a measure of the phase front perturbation. At low plasma densities, the transmitted intensity pattern is asymmetric with striations across the entire probe beam in the direction of the RPP smoothed beam. As the plasma density increases, the striations break up into smaller sizes along the direction of the RPP beam propagation. The breakup of the intensity pattern is consistent with self-focusing of the RPP smoothed interaction beam. Simulations of the experiment using the wave propagation code, PF3D, are in qualitative agreement demonstrating that the asymmetric striations can be attributed to the RPP driven density fluctuations. Quantification of the beam breakup measured by the transmitted SPLP could lead to a new method for measuring self-focusing of lasers in underdense plasmas.

  11. Very short NMR relaxation times of anions in ionic liquids: new pulse sequence to eliminate the acoustic ringing.

    Science.gov (United States)

    Klimavicius, Vytautas; Gdaniec, Zofia; Balevicius, Vytautas

    2014-11-11

    NMR relaxation processes of anions were studied in two neat imidazolium-based room temperature ionic liquids (RTILs) 1-decyl-3-methyl-imidazolium bromide- and chloride. The spin-lattice and spin-spin relaxations of 81Br and 35Cl nuclei were found to be extremely fast due to very strong quadrupolar interactions. The determined relaxation rates are comparable with those observed in the solids or in some critical organic solute/water/salt systems. In order to eliminate the acoustic ringing of the probe-head during relaxation times measurements the novel pulse sequence has been devised. It is based on the conventional inversion recovery pulse sequence, however, instead of the last 90° pulse the subsequence of three 90° pulses applied along axes to fulfill the phase cycling condition is used. Using this pulse sequence it was possible to measure T1 for both studied nuclei. The viscosity measurements have been carried out and the rotational correlation times were calculated. The effective 35Cl quadrupolar coupling constant was found to be almost one order lower than that for 81Br, i.e. 1.8 MHz and 16.0 MHz, respectively. Taking into account the facts that the ratio of (Q(35Cl)/Q(81Br))2≈0.1 and EFG tensors on the anions are quite similar, analogous structural organizations are expected for both RTILs. The observed T1/T2 (1.27-1.44) ratios were found to be not sufficiently high to confirm the presence of long-living (on the time scale of ≥10(-8) s) mesoscopic structures or heterogeneities in the studied neat ionic liquids.

  12. Enhancing caries resistance with a short-pulsed CO2 9.3-μm laser: a laboratory study (Conference Presentation)

    Science.gov (United States)

    Rechmann, Peter; Rechmann, Beate M.; Groves, William H.; Le, Charles; Rapozo-Hilo, Marcia L.; Featherstone, John D. B.

    2016-02-01

    The objective of this laboratory study was to test whether irradiation with a new 9.3µm microsecond short-pulsed CO2-laser enhances enamel caries resistance with and without additional fluoride applications. 101 human enamel samples were divided into 7 groups. Each group was treated with different laser parameters (Carbon-dioxide laser, wavelength 9.3µm, 43Hz pulse-repetition rate, pulse duration between 3μs to 7μs (1.5mJ/pulse to 2.9mJ/pulse). Using a pH-cycling model and cross-sectional microhardness testing determined the mean relative mineral loss delta Z (∆Z) for each group. The pH-cycling was performed with or without additional fluoride. The CO2 9.3μm short-pulsed laser energy rendered enamel caries resistant with and without additional fluoride use.

  13. Nike Experiments on Acceleration of Planar Targets Stabilized with a Short Spike Pulse^1

    Science.gov (United States)

    Weaver, J. L.; Velikovich, A. L.; Metzler, N.; Aglitskiy, Y.; Oh, J.; Mostovych, A. N.; Gardner, J. H.

    2005-10-01

    Theoretical work has shown that a low energy spike pulse in front of the drive laser pulse can help mitigate the growth of hydrodynamic instabilities in targets for inertial confinement fusion.[1]^ While other experiments [2] used higher spike pulse energies, this study reports the influence of a lower energy spike and longer spike-main pulse delay on the acceleration of planar CH targets. Time evolution of preimposed sinusoidal ripples on the target surface was observed using a monochromatic x-ray imaging system. Delayed onset and/or suppression of mode growth was found for the spike prepulse shots compared to those with a low intensity foot, in good agreement with predictions from FAST2D simulations. The propagation velocity of the decaying shock wave from the spike pulse was measured with VISAR and was also in good agreement with an analytical prediction.[3] [1] Metzler et al., Phys. Plasmas 6, 3283 (1999); 9, 5050 (2002); 10, 1897 (2003);Goncharov et al., Phys. Plasmas 10, 1906 (2003) ;Betti et al., Phys Plamas 12, 042703 (2005) ;[2]Knauer et al., Phys. Plasmas 12, 056306 (2005) ; [3]Velikovich et al., Phys. Plasmas 10, 3270 (2003). ^1Work supported by U. S. Department of Energy

  14. Short-term cropland responses to temperature extreme events during late winter

    Directory of Open Access Journals (Sweden)

    G. De Simon

    2013-04-01

    Full Text Available In recent years, several studies have focused on terrestrial ecosystem response to extreme events. Most of this research has been conducted in natural ecosystems, but few have considered agro-ecosystems. In this study, we investigated the impact of a manipulated warmer or cooler late winter-early spring on the carbon budget and final harvest of a soybean crop (Glycine max (L. Merr.. Soil temperature was altered by manipulating soil albedo by covering the soil surface with a layer of inert silica gravel. We tested three treatments: cooling (Co, warming (W, mix (M and control (C. An automated system continuously measured soil heterotrophic respiration (Rh, soil temperature profiles, and soil water content across the entire year in each plot. Phenological phases were periodically assessed and final harvest was measured in each plot. Results showed that treatments had only a transient effect on daily Rh rates which did not result in a total annual carbon budget significantly different from control, even though cooling showed a significant reduction in final harvest. We also observed anticipation in seed germination in both W and M treatments and a delay in germination for Co. Moreover, plant density and growth increased in W and M and decreased in Co.

  15. Transient Reorientation of a Doped Liquid Crystal System under a Short Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    LI Tao; XIANG Ying; LIU Yi-Kun; WANG Jian; YANG Shun-Lin

    2009-01-01

    The transient optical nonlinearity of a nematic liquid crystal doped with azo-dye DRW is examined.The optical reorientation threshold of a 25-μm-thick planar-aligned sample of 5CB using a 50 ns pulse duration 532 nm YAG laser pulse is observed to decrease from 800 mJ/mm2 to 0.6 mJ/mm2 after the addition of 1 vol% azo dopant,a reduction of three orders of magnitude.When using a laser pulse duration of 10 ns,no such effect is observed.Experimental results indicate that the azo dopant molecules undergo photoisomerization from trans-isomer to cis-isomer under exposure to light,and this conformation change reorients the 5CB molecules via intermolecular coupling between guest and host.This guest-host couphng also affects the azo photoisomerization process.

  16. Fragmentation dynamics of liquid-metal droplets under ultra-short laser pulses

    Science.gov (United States)

    Basko, M. M.; Krivokorytov, M. S.; Vinokhodov, A. Yu; Sidelnikov, Yu V.; Krivtsun, V. M.; Medvedev, V. V.; Kim, D. A.; Kompanets, V. O.; Lash, A. A.; Koshelev, K. N.

    2017-03-01

    We present the measurements and theoretical analysis of the deformation and fragmentation of spherical liquid-metal drops by picosecond and subpicosecond laser pulses. In the experiments, 60 μm droplets of Sn-In alloy were irradiated by Ti:Sa laser pulses with a peak energy fluence of  ˜100 J cm-2. The observed evolution of the droplet shape dramatically differs from that previously reported for nanosecond pulses. Invoking 2D hydrodynamic simulations, we explain how, due to the specifics of matter dynamics in the liquid-vapor phase coexistence region, a liquid droplet is transformed into a characteristic acorn-like expanding shell with two inner cavities. High sensitivity of the measured shell parameters to the details of the equation of state and metastable dynamics suggests that such experiments offer new possibilities in exploration of thermophysical properties of metals in the region of liquid-vapor phase transition.

  17. Peculiarities of Efficient Plasma Generation in Air and Water by Short Duration Laser Pulses

    Science.gov (United States)

    Adamovsky, Grigory; Floyd, Bertram M.

    2017-01-01

    We have conducted experiments to demonstrate an efficient generation of plasma discharges by focused nanosecond pulsed laser beams in air and provided recommendations on the design of optical systems to implement such plasma generation. We have also demonstrated generation of the secondary plasma discharge using the unused energy from the primary one. Focused nanosecond pulsed laser beams have also been utilized to generate plasma in water where we observed self-focusing and filamentation. Furthermore, we applied the laser generated plasma to the decomposition of methylene blue dye diluted in water.

  18. Mode-locked laser realized by selective area growth for short pulse generation and optical clock recovery in TDM systems

    Science.gov (United States)

    Lach, Eugen; Baums, Dieter; Bouayad-Amine, Jamal; Hache, Claudia; Haisch, Hansjorg; Kuhn, Edgar; Satzke, Klaus; Schilling, Michael; Weber, Juergen; Zielinski, Erich

    1996-04-01

    We report on monolithically integrated active/passive coupled cavity mode locked lasers for 1.55 micrometer realized by selective area growth technology of InGaAs(P) quantum wells. Mode locked FP or DBR lasers are fabricated with an integrated cavity comprising up to three different band gaps. The devices emit short light pulses at around 10 GHz repetition rate with pulse width down to 8.7 ps. A time-bandwidth product of 0.5 is achieved for mode locked DBR lasers. Active/passive integrated mode locked laser is used for generation of optical 10 GHz clock signal from optical 10 Gb/s PRBS RZ data stream injected into the laser cavity.

  19. Novel D-shaped fiber fabrication method for saturable absorber application in the generation of ultra-short pulses

    Science.gov (United States)

    Ahmad, H.; Safaei, R.; Rezayi, M.; Amiri, I. S.

    2017-08-01

    A cost-efficient, time-saving and effective technique for the fabrication of D-shaped fibers is presented, to provide a platform with a strong evanescent field to be used as a saturable absorber (SA). This technique provides flexibility by removing the required portion of the fiber, and a small polished length which offers a unique opportunity to deposit SA on its surface by simply submerging it in the SA solution without high losses. A compact fiber laser utilizing a graphene oxide coating on a fabricated D-shaped fiber as an SA capable of generating ultrashort pulses is designed and verified. We report the generation of ultrafast pulses as short as 227 fs with a 34.7 MHz repetition rate, having a 3 dB bandwidth of 14 nm at the 1570 nm center wavelength.

  20. Phenological Response of an Arizona Dryland Forest to Short-Term Climatic Extremes

    Directory of Open Access Journals (Sweden)

    Jessica Walker

    2015-08-01

    Full Text Available Baseline information about dryland forest phenology is necessary to accurately anticipate future ecosystem shifts. The overarching goal of our study was to investigate the variability of vegetation phenology across a dryland forest landscape in response to climate alterations. We analyzed the influence of site characteristics and climatic conditions on the phenological patterns of an Arizona, USA, ponderosa pine (Pinus ponderosa forest during a five-year period (2005 to 2009 that encompassed extreme wet and dry precipitation regimes. We assembled 80 synthetic Landsat images by applying the spatial and temporal adaptive reflectance fusion method (STARFM to 500 m MODIS and 30 m Landsat-5 Thematic Mapper (TM data. We tested relationships between site characteristics and the timing of peak Normalized Difference Vegetation Index (NDVI to assess the effect of climatic stress on the green-up of individual pixels during or after the summer monsoon. Our results show that drought-induced stress led to a fragmented phenological response that was highly dependent on microsite parameters, as both the spatial autocorrelation of peak timing and the number of significant site variables increased during the drought year. Pixels at lower elevations and with higher proportions of herbaceous vegetation were more likely to exhibit dynamic responses to changes in precipitation conditions. Our study demonstrates the complexity of responses within dryland forest ecosystems and highlights the need for standardized monitoring of phenology trends in these areas. The spatial and temporal variability of phenological signals may provide a quantitative solution to the problem of how to evaluate dryland land surface trends across time.

  1. Extremely short duration high intensity interval training substantially improves insulin action in young healthy males

    Directory of Open Access Journals (Sweden)

    Cottrell Greg

    2009-01-01

    Full Text Available Abstract Background Traditional high volume aerobic exercise training reduces cardiovascular and metabolic disease risk but involves a substantial time commitment. Extremely low volume high-intensity interval training (HIT has recently been demonstrated to produce improvements to aerobic function, but it is unknown whether HIT has the capacity to improve insulin action and hence glycemic control. Methods Sixteen young men (age: 21 ± 2 y; BMI: 23.7 ± 3.1 kg·m-2; VO2peak: 48 ± 9 ml·kg-1·min-1 performed 2 weeks of supervised HIT comprising of a total of 15 min of exercise (6 sessions; 4–6 × 30-s cycle sprints per session. Aerobic performance (250-kJ self-paced cycling time trial, and glucose, insulin and NEFA responses to a 75-g oral glucose load (oral glucose tolerance test; OGTT were determined before and after training. Results Following 2 weeks of HIT, the area under the plasma glucose, insulin and NEFA concentration-time curves were all reduced (12%, 37%, 26% respectively, all P -1, P = 0.058. Insulin sensitivity, as measured by the Cederholm index, was improved by 23% (P Conclusion The efficacy of a high intensity exercise protocol, involving only ~250 kcal of work each week, to substantially improve insulin action in young sedentary subjects is remarkable. This novel time-efficient training paradigm can be used as a strategy to reduce metabolic risk factors in young and middle aged sedentary populations who otherwise would not adhere to time consuming traditional aerobic exercise regimes.

  2. Observation of Electromagnetically Induced Transparency by a Train of Short Pulses

    Institute of Scientific and Technical Information of China (English)

    YE Cun-Yun

    2004-01-01

    @@ We report the experimental demonstration of electromagnetically induced transparency in hot rubidium (85 Rb)atomic vapour by using an actively mode-locked external cavity diode laser in Littman-Metcalf configuration.We can make opaque resonant transitions transparent to any two optical comb components in the pulse trains which excite atomic coherence in the ground states of 85Rb.

  3. Microscopy study of ripples created on steel surface by use of ultra short laser pulses

    NARCIS (Netherlands)

    Vincenc Obona, J.; Ocelik, V.; Visser, B.; Visser, B.; de Hosson, J.Th.M.; Skolski, J.Z.P.; Mitko, S.; Mitko, V.S.; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert

    2010-01-01

    This paper concentrates on ripples on the surface of steel that arise from lasermaterial interaction. In particular we have observed two different sets of ripples on steel samples that were machined by 210 fs laser pulses with 800 nm wavelength at normal incidence. Small ripples were found with

  4. Coherent propagation of a short polarised radiation pulse in a one-dimensional resonance Bragg grating

    NARCIS (Netherlands)

    Maimistov, A. I.; Polikarpov, V. V.

    2006-01-01

    The propagation of an optical ultrashort pulse in a resonance Bragg grating is considered taking into account the polarisation of electromagnetic radiation. It is assumed that the grating is formed by thin films containing two-level atoms with the triply degenerate upper energy level. The system of

  5. A comparison study of on-chip short pulse generation circuits based on a coplanar waveguide

    Institute of Scientific and Technical Information of China (English)

    邹焕; 耿永涛; 王平山; 李家胤

    2011-01-01

    A few traditional pulse-forming circuits are implemented in a commercial 0.13 μm digital complementary-metal-oxide-semiconductor (CMOS) technology. These circuits, based on a coplanar waveguide, are analyzed and compared through CadenceTM Spectre simulati

  6. Frequency Conversion of Short Optical Pulses in Negatively Spatially Dispersive Metamaterials

    Science.gov (United States)

    2015-10-22

    electromagnetic waves [4]. Current mainstream in fabricating bulk NIM slabs relies on engineering of LC nanocircuits - plasmonic mesoatoms with negative...be controlled by changing intensity and ratio of the the input pulse length to the metamaterial thickness (parameter d). It is demonstrated in Figs

  7. First-principles simulation for strong and ultra-short laser pulse propagation in dielectrics

    Science.gov (United States)

    Yabana, K.

    2016-05-01

    We develop a computational approach for interaction between strong laser pulse and dielectrics based on time-dependent density functional theory (TDDFT). In this approach, a key ingredient is a solver to simulate electron dynamics in a unit cell of solids under a time-varying electric field that is a time-dependent extension of the static band calculation. This calculation can be regarded as a constitutive relation, providing macroscopic electric current for a given electric field applied to the medium. Combining the solver with Maxwell equations for electromagnetic fields of the laser pulse, we describe propagation of laser pulses in dielectrics without any empirical parameters. An important output from the coupled Maxwell+TDDFT simulation is the energy transfer from the laser pulse to electrons in the medium. We have found an abrupt increase of the energy transfer at certain laser intensity close to damage threshold. We also estimate damage threshold by comparing the transferred energy with melting and cohesive energies. It shows reasonable agreement with measurements.

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

    Science.gov (United States)

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

    2015-03-01

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

  9. Intensity-Resolved Above Threshold Ionization of Xenon with Short Laser Pulses

    CERN Document Server

    Hart, Nathan A; Kaya, Gamze; Kaya, Necati; Kolomenskii, Alexandre A; Schuessler, Hans A

    2014-01-01

    We present intensity-resolved above threshold ionization (ATI) spectra of xenon using an intensity scanning and deconvolution technique. Experimental data were obtained with laser pulses of 58 fs and central wavelength of 800 nm from a chirped-pulse amplifier. Applying a deconvolution algorithm, we obtained spectra that have higher contrast and are in excellent agreement with characteristic 2 $U_p$ and 10 $U_p$ cutoff energies contrary to that found for raw data. The retrieved electron ionization probability is consistent with the presence of a second electron from double ionization. This recovered ionization probability is confirmed with a calculation based on the PPT tunneling ionization model [Perelomov, Popov, and Terent'ev, Sov. Phys. JETP 23, 924 (1966)]. Thus, the measurements of photoelectron yields and the proposed deconvolution technique allowed retrieval of more accurate spectroscopic information from the ATI spectra and ionization probability features that are usually concealed by volume averaging...

  10. A short-pulse K(a)-band instrumentation radar for foliage attenuation measurements.

    Science.gov (United States)

    Puranen, Mikko; Eskelinen, Pekka

    2008-10-01

    A portable K(a)-band instrumentation radar for foliage attenuation measurements has been designed. It uses direct dielectric resonator oscillator multiplier pulse modulation giving a half power pulse width of 17 ns. The dual conversion scalar receiver utilizes either a digital storage oscilloscope in envelope detection format or a special gated comparator arrangement providing 1 m resolution and associated led seven segment display for data analysis. The calibrated dynamic range is better than 37 dB with an equivalent noise floor of 0.005 dBsm at 25 m test range distance. First experiments indicate an effective beamwidth close to 1 degree. The total weight is below 5 kg and the unit can be mounted on a conventional photographic tripod. Power is supplied from a 12 V/6 A h sealed lead acid battery giving an operating time in excess of 10 h.

  11. Frequency Invariant Beam Steering for Short-Pulse Systems with a Rotman Lens

    Directory of Open Access Journals (Sweden)

    Andreas Lambrecht

    2010-01-01

    Full Text Available A promising approach for beam steering of high-voltage transient signals for HPEM-systems (High Power Electro Magnetic is presented. The inherent capability of the Rotman lens to provide true time delays is used to develop a prototype beam steering device for an antielectronics HPEM system in the frequency range from 350 MHz to 5 GHz. Results of analytical calculations, simulations, and measurements from a hardware prototype are presented. The detailed mechanical setup of the Rotman lens is presented. Additionally the output pulses are investigated when inputting a Gaussian-like transient signal. Then time domain measures of quality (full width at half maximum, ringing, delay spread, maximum of transfer function are investigated for these output transients, and the simulation and measurement results are compared. A concluding analysis of the realizable time domain array pattern shows the radiated pulse form.

  12. Composition and structure modification of a WTi/Si system by short laser pulses

    Science.gov (United States)

    Petrović, S.; Gaković, B.; Peruško, D.; Radak, B.; Desai, T.; Kovač, J.; Panjan, P.; Trtica, M.

    2010-03-01

    Picosecond (40 ps) pulsed Nd:YAG laser irradiation of a WTi thin film on silicon with a wavelength of 532 nm and a fluence 2.1 J/cm2 was performed in air. This led to significant changes of the chemical composition and morphology on the surface of the WTi thin film. The results show an increase in surface roughness, due to formation of conical structures, about 50 nm wide in the base, and a very thin oxide layer composed of WO3 and TiO2, with a dominant TiO2 phase at the top, within the depth of about 20 nm. The thickness of the oxide layer was dependent on the number of laser pulses. The samples were analyzed by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy.

  13. Selective Strong-Field Enhancement and Suppression of Ionization with Short Laser Pulses

    CERN Document Server

    Hart, Nathan A; Kolomenskii, Alexandre A; Paulus, Gerhard G; Bauer, Dieter; Schuessler, Hans A

    2015-01-01

    We experimentally demonstrate robust selective excitation and attenuation of atomic Rydberg level populations in sodium vapor (Na I) using intense laser pulses in the strong field limit ($> 10^{12} W/cm^{2}$). The coherent control of the atomic population and related ionization channels is realized for intensities above the over-the-barrier ionization intensity. A qualitative model predicts that this strong field coherent control arises through the manifestation of a Freeman resonance.

  14. Determination of the carrier envelope phase for short, circularly polarized laser pulses

    Science.gov (United States)

    Titov, Alexander I.; Kämpfer, Burkhard; Hosaka, Atsushi; Nousch, Tobias; Seipt, Daniel

    2016-02-01

    We analyze the impact of the carrier envelope phase on the differential cross sections of the Breit-Wheeler and the generalized Compton scattering in the interaction of a charged electron (positron) with an intensive ultrashort electromagnetic (laser) pulse. The differential cross sections as a function of the azimuthal angle of the outgoing electron have a clear bump structure, where the bump position coincides with the value of the carrier phase. This effect can be used for the carrier envelope phase determination.

  15. Harmonic Enhancement Mechanism of a Superposition State Atom Irradiated by Short Pulses

    Institute of Scientific and Technical Information of China (English)

    YANG Yu-Jun; ZHU Qi-Ren; CHEN Ji-Gen; HUANG Yu-Xin; GUO Fu-Ming; ZHANG Hong-Xing; SUN Jia-Zhong; ZHU Hong-Yu; WANG Li; WANG Hui

    2007-01-01

    We investigate the high-order harmonic generation (HHG) of a model atom whose initial state is prepared in a superposition of its ground state and an excited state irradiated by different duration laser pulses. Compared to the HHG generated from an atom whose initial state is in its ground state, its conversion efficiency obtains some enhancement. The enhancement originates from the higher ionization rate (rather than the ionization yield) of the atom with superposition initial state.

  16. Techniques and physical properties of 10MHz short pulse focused ultrasonic transducer

    Institute of Scientific and Technical Information of China (English)

    ZHU Guozhen; YANG Yong; LU Kean

    2004-01-01

    A focused ultrasonic transducer used for biomedical purposes with a fundamental frequency of 10MHz and a pulse width of one and a half periods is described in this paper. Its physical properties are given including (1) focused acoustic field recorded by an optical means, (2) electric waveform for triggering the transducer and the corresponding waveform of the wave received by another transducer, and (3) result of tests on a sample object.

  17. NANOSCALE STRUCTURES GENERATION WITHIN THE SURFACE LAYER OF METALS WITH SHORT UV LASER PULSES

    Directory of Open Access Journals (Sweden)

    Dmitry S. Ivanov

    2017-01-01

    Full Text Available We have completed modeling of a laser pulse influence on a gold target. We have applied a hybrid atomistic-continuum model to analyze the physical mechanisms responsible for the process of nanostructuring. The model combines the advantages of Molecular Dynamics and Two Temperature Model. We have carried out a direct comparison of the modeling results and experimental data on nano-modification due to a single ps laser pulse at the energy densities significantly exceeding the melting threshold. The experimental data is obtained due to a laser pulse irradiation at the wavelength of 248 nm and duration of 1.6 ps. The mask projection (diffraction grating creates the sinusoidal intensity distribution on a gold surface with periods of 270 nm, 350 nm, and 500 nm. The experimental data and modeling results have demonstrated a good match subject to complex interrelations between a fast material response to the laser excitation, generation of crystal defects, phase transitions and hydrodynamic motion of matter under condition of strong laser-induced non-equilibrium. The performed work confirms the proposed approach as a powerful tool for revealing the physical mechanisms underlying the process of nanostructuring of metal surfaces. Detailed understanding of the dynamics of these processes gives the possibility for designing the topology of functional surfaces on nano- and micro-scales.

  18. Adapting Particle-In-Cell simulations to the study of short pulse laser damage

    Science.gov (United States)

    Mitchell, Robert; Schumacher, Douglass; Chowdhury, Enam

    2014-10-01

    We present novel Particle-In-Cell (PIC) simulations of the full femtosecond-pulse laser damage process and the resulting damage spot morphology. At the heart of these simulations is the implementation, for the first time, of a Lennard-Jones pair potential model (LJPPM) for PIC codes. The use of PIC facilitates the first ab-initio treatment of realistic target sizes, retaining the strengths of PIC including self-consistent treatment of the laser-particle interaction and subsequent generation of plasma waves and electron heating, while the LJPPM allows a PIC code to treat a system of particles as a medium which can ablate, melt, and resolidify. Combining these two approaches, we model the effect of a femtosecond-pulse laser on metal targets near and above the damage threshold and compare to recent experimental results. In particular, we present the first simulations of the emergence of Laser-Induced Periodic Surface Structure (LIPSS) upon femtosecond-pulse laser irradiation.

  19. Time-dependent H-like and He-like Al lines produced by ultra-short pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Takako; Kato, Masatoshi [National Inst. for Fusion Science, Nagoya (Japan); Shepherd, R.; Young, B.; More, R.; Osterheld, Al

    1998-03-01

    We have performed numerical modeling of time-resolved x-ray spectra from thin foil targets heated by the LLNL Ultra-short pulse (USP) laser. The targets were aluminum foils of thickness ranging from 250 A to 1250 A, heated with 120 fsec pulses of 400 nm light from the USP laser. The laser energy was approximately 0.2 Joules, focused to a 3 micron spot size for a peak intensity near 2 x 10{sup 19} W/cm{sup 2}. Ly{alpha} and He{alpha} lines were recorded using a 900 fsec x-ray streak camera. We calculate the effective ionization, recombination and emission rate coefficients including density effects for H-like and He-like aluminum ions using a collisional radiative model. We calculate time-dependent ion abundances using these effective ionization and recombination rate coefficients. The time-dependent electron temperature and density used in the calculation are based on an analytical model for the hydrodynamic expansion of the target foils. During the laser pulse the target is ionized. After the laser heating stops, the plasma begins to recombine. Using the calculated time dependent ion abundances and the effective emission rate coefficients, we calculate the time dependent Ly{alpha} and He{alpha} lines. The calculations reproduce the main qualitative features of the experimental spectra. (author)

  20. Short pulse, high resolution, backlighters for point projection high-energy radiography at the National Ignition Facility

    Science.gov (United States)

    Tommasini, R.; Bailey, C.; Bradley, D. K.; Bowers, M.; Chen, H.; Di Nicola, J. M.; Di Nicola, P.; Gururangan, G.; Hall, G. N.; Hardy, C. M.; Hargrove, D.; Hermann, M.; Hohenberger, M.; Holder, J. P.; Hsing, W.; Izumi, N.; Kalantar, D.; Khan, S.; Kroll, J.; Landen, O. L.; Lawson, J.; Martinez, D.; Masters, N.; Nafziger, J. R.; Nagel, S. R.; Nikroo, A.; Okui, J.; Palmer, D.; Sigurdsson, R.; Vonhof, S.; Wallace, R. J.; Zobrist, T.

    2017-05-01

    High-resolution, high-energy X-ray backlighters are very active area of research for radiography experiments at the National Ignition Facility (NIF) [Miller et al., Nucl. Fusion 44, S228 (2004)], in particular those aiming at obtaining Compton-scattering produced radiographs from the cold, dense fuel surrounding the hot spot. We report on experiments to generate and characterize point-projection-geometry backlighters using short pulses from the advanced radiographic capability (ARC) [Crane et al., J. Phys. 244, 032003 (2010); Di Nicola et al., Proc. SPIE 2015, 93450I-12], at the NIF, focused on Au micro-wires. We show the first hard X-ray radiographs, at photon energies exceeding 60 keV, of static objects obtained with 30 ps-long ARC laser pulses, and the measurements of strength of the X-ray emission, the pulse duration and the source size of the Au micro-wire backlighters. For the latter, a novel technique has been developed and successfully applied.

  1. Temporal and spatial temperature distribution in the glabrous skin of rats induced by short-pulse CO2 laser

    Science.gov (United States)

    Lu, Pen-Li; Hsu, Shu-Shen; Tsai, Meng-Li; Jaw, Fu-Shan; Wang, An-Bang; Yen, Chen-Tung

    2012-11-01

    Pain is a natural alarm that aids the body in avoiding potential danger and can also present as an important indicator in clinics. Infrared laser-evoked potentials can be used as an objective index to evaluate nociception. In animal studies, a short-pulse laser is crucial because it completes the stimulation before escape behavior. The objective of the present study was to obtain the temporal and spatial temperature distributions in the skin caused by the irradiation of a short-pulse laser. A fast speed infrared camera was used to measure the surface temperature caused by a CO2 laser of different durations (25 and 35 ms) and power. The measured results were subsequently implemented with a three-layer finite element model to predict the subsurface temperature. We found that stratum corneum was crucial in the modeling of fast temperature response, and escape behaviors correlated with predictions of temperature at subsurface. Results indicated that the onset latency and duration of activated nociceptors must be carefully considered when interpreting physiological responses evoked by infrared irradiation.

  2. Short-pulse Er:YAG laser increases bond strength of composite resin to sound and eroded dentin

    Science.gov (United States)

    Cersosimo, Maria Cecília Pereira; Matos, Adriana Bona; Couto, Roberta Souza D.'Almeida; Marques, Márcia Martins; de Freitas, Patricia Moreira

    2016-04-01

    This study evaluated the influence of the irradiation with a short-pulse Er:YAG laser on the adhesion of composite resin to sound and eroded dentin (SD and ED). Forty-six samples of occlusal dentine, obtained from human molars, had half of their surface protected, while the other half was submitted to erosive cycles. Afterward, 23 samples were irradiated with Er:YAG laser, resulting in four experimental groups: SD, sound irradiated dentine (SID-Er:YAG, 50 μs, 2 Hz, 80 mJ, and 12.6 J/cm2), ED, and eroded irradiated dentin (EID-erosion + Er:YAG laser). A self-etching adhesive system was used, and then cylinders of composite resin were prepared. A microshear bond strength test was performed after 24 h storage (n=20). The morphology of SD and ED, with or without Er:YAG laser irradiation, was evaluated under scanning electron microscopy (n=3). Bond strength values (MPa) were subjected to analysis of variance followed by Tukey's test. Statistically significant differences were found among the experimental groups: SD (9.76±3.39 B), SID (12.77±5.09 A), ED (5.12±1.72 D), and EID (7.62±3.39 C). Even though erosion reduces the adhesion to dentin, the surface irradiation with a short-pulse Er:YAG laser increases adhesion to both ED and SD.

  3. Frequency entanglement characterization of short-pulse pumped SPDC biphoton source with a Mach-Zehnder interferometer

    Science.gov (United States)

    Zhai, Yiwei; Dong, Ruifang; Li, Baihong; Quan, Runai; Wang, Mengmeng; Hou, Feiyan; Liu, Tao; Zhang, Shougang

    2017-06-01

    Frequency entangled biphoton sources have played an important role in quantum information. There are two key characteristics which determine the extent of their applications: the spectral indistinguishability and the degree of frequency entanglement. Previously, the spectral indistinguishability of the biphoton state is measured by the Hong-Ou-Mandel (HOM) interference visibility, whereas the degree of frequency entanglement is normally characterized with independent spectral measurements. However, these two quantum features have not been successfully measured with a single experimental setup. In this paper, we deduce the temporal distribution of a short-pulse pumped type-II spontaneous parametric down converted (SPDC) biphoton source and its relevant temporal entanglement parameter R t for operationally quantifying the degree of frequency entanglement. Furthermore, we theoretically and experimentally demonstrate, due to the inherent group delay, the difference between the signal and idler photons at the exit of the type-II nonlinear crystal, resulting in a HOM-shape dip at both sides of the center fringed envelope of the MZ interferometric coincidence diagram. By measuring the HOM-shape dip depth, the separation between the two sideband dips as well as the MZ fringed envelope width, both the spectral indistinguishability and the temporal entanglement parameter can thus be simultaneously quantified. This implementation provides us a unified and convenient method to characterize the frequency entanglement of the short-pulse pumped biphotons.

  4. Short (

    NARCIS (Netherlands)

    Telleman, Gerdien; den Hartog, Laurens

    2013-01-01

    Aim: This systematic review assessed the implant survival rate of short (<10 mm) dental implants installed in partially edentulous patients. A case report of a short implant in the posterior region have been added. Materials and methods: A search was conducted in the electronic databases of MEDLINE

  5. Short (

    NARCIS (Netherlands)

    Telleman, Gerdien; den Hartog, Laurens

    2013-01-01

    Aim: This systematic review assessed the implant survival rate of short (<10 mm) dental implants installed in partially edentulous patients. A case report of a short implant in the posterior region have been added. Materials and methods: A search was conducted in the electronic databases of MEDLINE

  6. Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

    Science.gov (United States)

    Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

    2013-01-01

    This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

  7. STUDY OF THE PROPAGATION OF SHORT PULSE LASER WITH CAVITY USING NUMERICAL SIMULATION SOFTWARE

    Directory of Open Access Journals (Sweden)

    S. Terniche

    2015-07-01

    Full Text Available The purpose of this representation is to show the potentialities (Computational Time, access to the dynamic and feasibility of systematic studies of the numerical study of the nonlinear dynamics in laser cavity, assisted by software. We will give as an example, one type of cavity completely fibered composed of several elements and then studying the physical parameters of a pulse propagating into this cavity, determining its characteristics at the output. The results are interesting but we also projects to verify them experimentally by making assemblies similar to this type of cavities.

  8. Printed organic smart devices characterized by ultra-short laser pulses

    DEFF Research Database (Denmark)

    Pastorelli, Francesco

    Resume: In this study, we demonstrate that nonlinear optical microscopy is a promising technique to characterize organic printed electronics. Using ultrashort laser pulses we stimulate two-photon absorption in a roll coated polymer semiconductor and map the resulting two-photon induced...... propose that the TPPL is a good indicator to map and monitor the charge carrier density and the molecular packing of the printed polymer material. Importantly, simple calculations based on the signal levels, suggest that this technique can be extended to the real time mapping of the polymer semiconductor...... film, even during the printing process, in which the high printing speed poses the need for equally high acquisition rates....

  9. Raman Based Dispersive Systems for Short Pulse Generation and Optical Signal Processing

    Science.gov (United States)

    Kalyoncu, Salih Kagan

    Spatiotemporal dispersive systems have been widely utilized for nonlinear optics and optical signal processing applications. This thesis is dedicated to the investigation of dispersive and nonlinear properties of optical fibers, temporal dispersion for real time operation and spatially dispersed pulse shaping systems. In particular, this thesis is focused on Raman based dispersive systems based on such promising techniques as dispersion management, photonic time stretching and space-to-wavelength mapping for synchronous pulse generation and all-optical RF arbitrary waveform generation incorporated with mature MEMS technology. The first part of this thesis discusses a novel technique of using dispersion managed system for synchronous first and second order pulsed Raman lasers that can achieve frequency spacing of up to 1000 cm-1, which are widely utilized for CARS microscopy applications. In particular, I focus on analytical and numerical analysis of pulsed stability derived for Raman lasers by using dispersion-managed telecom fibers and pumping at near 1530 nm telecom wavelengths. I show the evolution of the first and second order Stokes signals at the output for different peak pump power and the net anomalous dispersion combinations. I determine the stability condition for dispersion-managed synchronous Raman lasers up to second order. In the second part of the thesis, the noise performance of the amplified time stretched systems is investigated. Amplified time stretched systems enabling real time applications such as high-speed analog-to-digital converters, RF arbitrary waveform generation and dispersive imaging are performance limited by the noise cumulated in the system. In particular, I analyze the noise performance and hence the effective number of bits (ENOB) performance of time stretch ADCs with distributed and lumped amplifications. I estimate that distributed amplification in time stretch system with >10GHz analog bandwidth exhibit up to 16dB higher SNR

  10. Selective laser melting of metal micropowders with short-pulse laser

    Science.gov (United States)

    Wałpuski, B.

    2016-09-01

    Selective laser melting is a unique additive technique which can manufacture solid metal objects but it require expensive, high power lasers. The primary aim of this work was to check is it possible to carry out this process by using lower power and high energy pulse laser. The secondary goal was to examine the influence of main technological parameters of selective laser melting on the quality and the thickness of produced layer. The requirements of metal powder, which allowed to obtain a layer with microthickness, were developed.

  11. A large aperture reflective wave-plate for high-intensity short-pulse laser experiments

    CERN Document Server

    Aurand, Bastian; Zhao, Huanyu; Kuschel, Stephan; Wünsche, Martin; Jäckel, Oliver; Heyer, Martin; Wunderlich, Frank; Kaluza, Malte C; Paulus, Gerhard G; Kuehl, Thomas

    2012-01-01

    We report on a reflective wave-plate system utilizing phase-shifting mirrors (PSM) for a continuous variation of elliptical polarization without changing the beam position and direction. The scalability of multilayer optics to large apertures and the suitability for high-intensity broad-bandwidth laser beams make reflective wave-plates an ideal tool for experiments on relativistic laser-plasma interaction. Our measurements confirm the preservation of the pulse duration and spectrum when a 30-fs Ti:Sapphire laser beam passes the system.

  12. Electron and phonon dynamics in laser short pulses-heated metals

    Science.gov (United States)

    Pietanza, L. D.; Colonna, G.; Capitelli, M.

    2005-07-01

    The simultaneous electron and phonon relaxation dynamic in a metal film subjected to a laser pulse has been theoretically investigated. A system of two coupled time- and energy-dependent Boltzmann equations describing the electron and phonon dynamics has been numerically solved. The collision processes considered are electron-electron (e-e) and electron-phonon (e-p) collisions. Our results show the non-equilibrium electron distribution and the electron and phonon relaxation dynamics both after a femtosecond and a picosecond laser perturbations.

  13. [Pulse-modulated Electromagnetic Radiation of Extremely High Frequencies Protects Cellular DNA against Damaging Effect of Physico-Chemical Factors in vitro].

    Science.gov (United States)

    Gapeyev, A B; Lukyanova, N A

    2015-01-01

    Using a comet assay technique, we investigated protective effects of. extremely high frequency electromagnetic radiation in combination with the damaging effect of X-ray irradiation, the effect of damaging agents hydrogen peroxide and methyl methanesulfonate on DNA in mouse whole blood leukocytes. It was shown that the preliminary exposure of the cells to low intensity pulse-modulated electromagnetic radiation (42.2 GHz, 0.1 mW/cm2, 20-min exposure, modulation frequencies of 1 and 16 Hz) caused protective effects decreasing the DNA damage by 20-45%. The efficacy of pulse-modulated electromagnetic radiation depended on the type of genotoxic agent and increased in a row methyl methanesulfonate--X-rays--hydrogen peroxide. Continuous electromagnetic radiation was ineffective. The mechanisms of protective effects may be connected with an induction of the adaptive response by nanomolar concentrations of reactive oxygen species formed by pulse-modulated electromagnetic radiation.

  14. Electron Emission from Ferroelectric/Antiferroelectric Cathodes Excited by Short High-Voltage Pulses

    CERN Document Server

    Benedek, G; Handerek, J; Riege, H

    1997-01-01

    Un-prepoled Lead Zirconate Titanate Lanthanum doped-PLZT ferroelectric cathodes have emitted intense current pulses under the action of a high voltage pulse of typically 8 kV/cm for PLZT of 8/65/35 composition and 25 kV/cm for PLZT of 4/95/5 composition. In the experiments described in this paper, the exciting electric field applied to the sample is directed from the rear surface towards the emitting surface. The resulting emission is due to an initial field emission from the metal of the grid deposited over the emitting surface with the consequent plasma formation and the switching of ferroelectric domains. These electrons may be emitted directly form the crystal or from the plasma. This emission requires the material in ferroelectric phase. In fact, PLZT cathodes of the 8/65/35 type, that is with high Titanium content, showing ferroelectric-paraelectric phase sequence, emit at room temperature, while PLZT cathodes of the 4/95/5 type, that is with low Titanium content, having antiferro-ferro-paraelectric pha...

  15. Ultrafast electron kinetics in short pulse laser-driven dense hydrogen

    Science.gov (United States)

    Zastrau, U.; Sperling, P.; Fortmann-Grote, C.; Becker, A.; Bornath, T.; Bredow, R.; Döppner, T.; Fennel, T.; Fletcher, L. B.; Förster, E.; Göde, S.; Gregori, G.; Harmand, M.; Hilbert, V.; Laarmann, T.; Lee, H. J.; Ma, T.; Meiwes-Broer, K. H.; Mithen, J. P.; Murphy, C. D.; Nakatsutsumi, M.; Neumayer, P.; Przystawik, A.; Skruszewicz, S.; Tiggesbäumker, J.; Toleikis, S.; White, T. G.; Glenzer, S. H.; Redmer, R.; Tschentscher, T.

    2015-11-01

    Dense cryogenic hydrogen is heated by intense femtosecond infrared laser pulses at intensities of {10}15-{10}16 W cm-2. Three-dimensional particle-in-cell (PIC) simulations predict that this heating is limited to the skin depth, causing an inhomogeneously heated outer shell with a cold core and two prominent temperatures of about 25 and 40 {eV} for simulated delay times up to +70 {fs} after the laser pulse maximum. Experimentally, the time-integrated emitted bremsstrahlung in the spectral range of 8-18 nm was corrected for the wavelength-dependent instrument efficiency. The resulting spectrum cannot be fit with a single temperature bremsstrahlung model, and the best fit is obtained using two temperatures of about 13 and 30 eV. The lower temperatures in the experiment can be explained by missing energy-loss channels in the simulations, as well as the inclusion of hot, non-Maxwellian electrons in the temperature calculation. We resolved the time-scale for laser-heating of hydrogen, and PIC results for laser-matter interaction were successfully tested against the experiment data.

  16. Investigation of short pulse effects in IR FELs and new simulation results

    CERN Document Server

    Asgekar, Vivek; Brunken, M; Casper, Lars; Genz, Harald; Grigore, Maria; Hessler, Christoph; Khodyachykh, Sergiy; Richter, Achim; Van der Meer, Alex F G

    2003-01-01

    The Darmstadt IR FEL is designed to generate wavelengths between 3 and 10 mum and driven by the superconducting electron linear accelerator. The pulsed electron beam has a peak current of 2.7 A leading to a small signal gain of 5%. Currently, investigations of the energy transfer process inside the undulator are performed using the 1D time-dependent simulation code FAST1D-OSC. We present simulation results for the power vs. different desynchronization and tapering parameters as well as a comparison with experimental data from the S-DALINAC IR-FEL. Furthermore, a compact autocorrelation system assuring a background-free measurement of the optical pulse length is described. In a first test experiment at FELIX, the autocorrelator has been tested at wavelengths 5.7 less than approximately equals lambda less than approximately equals 9.0 mum. The frequency doubling in a 2 mm-long ZnGeP//2-crystal resulted in a time resolution of 300 fs and a conversion efficiency of 5%.

  17. Waveguide piezoelectric micromachined ultrasonic transducer array for short-range pulse-echo imaging

    Science.gov (United States)

    Lu, Y.; Tang, H.; Wang, Q.; Fung, S.; Tsai, J. M.; Daneman, M.; Boser, B. E.; Horsley, D. A.

    2015-05-01

    This paper presents an 8 × 24 element, 100 μm-pitch, 20 MHz ultrasound imager based on a piezoelectric micromachined ultrasonic transducer (PMUT) array having integrated acoustic waveguides. The 70 μm diameter, 220 μm long waveguides function both to direct acoustic waves and to confine acoustic energy, and also to provide mechanical protection for the PMUT array used for surface-imaging applications such as an ultrasonic fingerprint sensor. The imager consists of a PMUT array bonded with a CMOS ASIC using wafer-level conductive eutectic bonding. This construction allows each PMUT in the array to have a dedicated front-end receive amplifier, which together with on-chip analog multiplexing enables individual pixel read-out with high signal-to-noise ratio through minimized parasitic capacitance between the PMUT and the front-end amplifier. Finite element method simulations demonstrate that the waveguides preserve the pressure amplitude of acoustic pulses over distances of 600 μm. Moreover, the waveguide design demonstrated here enables pixel-by-pixel readout of the ultrasound image due to improved directivity of the PMUT by directing acoustic waves and creating a pressure field with greater spatial uniformity at the end of the waveguide. Pulse-echo imaging experiments conducted using a one-dimensional steel grating demonstrate the array's ability to form a two-dimensional image of a target.

  18. Decoration of silica nanowires with gold nanoparticles through ultra-short pulsed laser deposition

    Science.gov (United States)

    Gontad, F.; Caricato, A. P.; Cesaria, M.; Resta, V.; Taurino, A.; Colombelli, A.; Leo, C.; Klini, A.; Manousaki, A.; Convertino, A.; Rella, R.; Martino, M.; Perrone, A.

    2017-10-01

    The ablation of a metal target at laser energy densities in the range of 1-10 TW/cm2 leads to the generation of nanoparticles (NP) of the ablated material. This aspect is of particular interest if the immobilization of NPs on three-dimensional (3D) substrates is necessary as for example in sensing applications. In this work the deposition of Au NP by irradiation of a Au bulk target with a sub-picosecond laser beam (500 fs; 248 nm; 10 Hz) on 2D (silica and Si(100)) and 3D substrates (silica nanowire forests) is reported for different number of laser pulses (500, 1000, 1500, 2000, 2500). A uniform coverage of small Au NPs (with a diameter of few nm) on both kinds of substrates has been obtained using a suitable number of laser pulses. The presence of spherical droplets, with a diameter ranging from tens of nm up to few μm was also detected on the substrate surface and their presence can be explained by the weak electron-phonon coupling of Au. The optical characterization of the samples on 2D and 3D substrates evidenced the surface plasmon resonance peak characteristic of the Au NPs although further improvements of the size-distribution are necessary for future applications in sensing devices.

  19. Optically induced mode conversion in graded-index fibers using ultra-short laser pulses

    CERN Document Server

    Hellwig, Tim; Fallnich, Carsten

    2013-01-01

    We propose the use of graded-index few-mode fibers for mode-conversion by long-period gratings (LPG) transiently written by ultrashort laser pulses using the optical Kerr effect. The mode inter- action is studied by numerically solving the multi-mode coupled nonlinear Schroedinger equations. We present highly efficient conversion of the LP 01 - into the LP 11 -mode preserving the pulse shape in contrast to previous results in step-index fibers. Furthermore, mode conversion using different wavelengths for inducing and probing the LPG is shown. Due to the flat phase-matching curve of the examined modes in the graded-index fiber, mode-conversion can be observed for probe center wavelengths of 1100nm up to 1800nm with a write beam centered around 1030nm. Therefore, a complete separation of the probe from the write beam should be possible as well as the application of optically induced guided mode conversion for all optical modulation across a broad wavelength range.

  20. Bilayer Bismuth Selenide nanoplatelets based saturable absorber for ultra-short pulse generation (Invited)

    Science.gov (United States)

    Xu, Yanhua; Xie, Hanhan; Jiang, Guobao; Miao, Lili; Wang, Ke; Tang, Siying; Yu, Xuefeng; Zhang, Han; Bao, Qiaoliang

    2017-07-01

    Based on an efficient and bottom-up synthesis technique, Bismuth Selenide (Bi2Se3) nanoplatelets with uniform morphology and average thickness down to 3-7 nm had been fabricated. Its nonlinear absorption property under high power excitation had been well characterized by our Z-scan measurement system at different illumination wavelengths, and we found that the as-fabricated bi-layer Bi2Se3 nanoplatelets show unique nonlinear optical responses, that is, with a saturable optical intensity of 32 GW/cm2 (resp. 3.7 MW/cm2) and a modulation depth of 88% (resp. 36%) at 800 nm (resp. 1565 nm). By implementing its saturable absorption property, we designed an optical saturable absorber device based on bilayer Bi2Se3 nanoplatelets through deposited them onto the end-facet of optical fiber. The as-fabricated optical saturable absorber device allows for the generation of mode-locking pulses at 1571 nm with pulse duration of 579 fs and a repetition rate of 12.54 MHz at a pump power of 160 mW. The method on fabricating ultrathin Bi2Se3 nanoplatelets may pave a new way to massive production of large-area topological insulator thin films that can be used in two-dimensional layered materials related photonics device.

  1. Investigating the Inverse Faraday Effect with an intense short pulse laser

    Science.gov (United States)

    Najmudin, Zulfikar; Tatarakis, Michealis; Krushelnick, Karl; Clark, Eugene; Santala, Marko; Dangor, Bucker; Clarke, Robert; Neely, David; Faure, Jerome; Malka, Victor

    2000-10-01

    A circularly polarised laser beam traversing through a plasma can generate an azimuthal electron current, due to their combined quiver motion. This will generate a solenoidal magnetic field in the plasma colinear with the laser propagation. This phenomena is known as the Inverse Faraday Effect (IFE), and can result in sizeable magnetic field strength for an ultra-intense laser pulses traversing through sufficiently dense plasmas. We present here measurements of the IFE field generated by the ultra-intense Vulcan:CPA laser travelling through underdense plasmas. The Vulcan:CPA laser can be focused to greater than 5 × 10^18 Wcm-2, and can generate IFE magnetic fields in excess of 2 MG. We present here the variation of the field with intensity and density, as well as measurements of its temporal and spatial behaviour. Noticeably the field is only observed for the time duration of the driver pulse, and decreases in spatial extent with increasing strength of magnetic field.

  2. 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.

  3. APPLICATION OF EXTREME VALUE THEORY AND FUNDAMENTAL ANALYSIS IN LONG-SHORT STRATEGIES: AN ANALYSIS OF PAIR TRADINGS IN THE BRAZILIAN MARKET

    Directory of Open Access Journals (Sweden)

    Danilo Soares Monte-Mor

    2014-09-01

    Full Text Available In recent decades, the number of funds has increased which aim to explore market inefficiencies through arbitrage strategies, among which the long-short strategy stands out. A large part of the analyses used to obtain the pair tradings, however, does not consider the extreme deviations that exist in the interdependence process between the assets involved and the firms’ operational quality indicators. The Extreme Value Theory and Fundamental Analysis were used in this study to model the series of the asset pair price indices obtained based on the accounting indicator structure proposed by Piotroski (2000. These approaches permitted considering companies with positive signs of profitability, an operational capital structure and efficiency, besides distributions that are capable of capturing the extreme co-movements associated with the selected pair tradings. Based on this model, a new quantitative approach was created for the long-short strategy, called the GEV Long-Short. The obtained results suggest that the best adjustment of the extreme quantiles through the extreme value distribution can provide more refined probabilistic support for the return to the average to justify the possibility of long-short arbitrage.

  4. Using Short Pulse Lasers to Address Frontiers in High Pressure Physics

    Energy Technology Data Exchange (ETDEWEB)

    Wildmann, K.; Springer, P.T.; Cauble, R.; Foord, M.E.; Guethlein, G.; Ng, A.; Patel, P.K.; Price, D.F.; Rogers, F.J; Wicks, S.C.

    1999-08-10

    Having laser intensities of 10{sup 21} W/cm{sup 2} yield electrical field strengths of 10{sup 12} V/cm which is comparable to the field strength at the K-shell of neon. Instant field ionization becomes part of the laser-matter interaction allowing to transfer most of the photons momenta directly onto the ions by driving an electrostatic shock through the target equivalent to pressures of several 100 Gbar. Utilization of these high-pressure conditions in form of equation of state measurements, however, strongly depends on the contrast of the femtosecond laser pulse. Currently, the Livermore USP and JanUSP lasers reach contrast values up to 10{sup 8}. This is sufficient to explore near-isochorically heated materials at moderate intensities (10{sup 13}-10{sup 15} W/cm{sup 2}) attaining pressures around 100 Mbar.

  5. Ultrahigh-current proton beams from short-pulse laser-solid interactions

    Energy Technology Data Exchange (ETDEWEB)

    Badziak, J; Jablowski, S; Parys, P; Rosinski, M; Suchanska, R; Wolowski, J [Institute of Plasma Physics and Laser Microfusion, EURATOM Association, Warsaw (Poland); Antici, P; Fuchs, J; Lancia, L; Mancic, A [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, Route de Saclay, 91128 Palaiseau (France); Szydlowski, A [Andrzej Soltan Institute for Nuclear Studies, Warsaw (Poland)], E-mail: badziak@ifpilm.waw.pl

    2008-05-01

    The results of studies of high-current proton beam generation from thin (1-3{mu}m) solid targets irradiated by 0.35-ps laser pulse of intensity up to 2x10{sup 19} W/cm{sup 2} are reported. It is shown that the proton beams of multi-MA currents and multi-TA/cm{sup 2} current densities at the source can be produced when the laser-target interaction conditions approach the skin-layer ponderomotive acceleration requirements. The current and energy spectrum of protons remarkably depend on the target structure. In particular, using a double-layer Au/PS target (plastic covered by 0.1 - 0.2{mu}m Au front layer) results in two-fold higher proton currents and higher proton energies than in the case of a plastic target.

  6. Generation of fluorescent CdSe nanocrystals by short-pulse laser fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Zholudov, Yu. T., E-mail: yurets-z@rambler.ru [Kharkiv National University of Radioelectronics (Ukraine); Sajti, C. L., E-mail: l.sajti@lzh.de [Laser Zentrum Hannover e.V. (Germany); Slipchenko, N. N. [Kharkiv National University of Radioelectronics (Ukraine); Chichkov, B. N. [Laser Zentrum Hannover e.V. (Germany)

    2015-12-15

    A simple liquid-phase laser fragmentation approach, resulting in the rapid transformation of CdSe microcrystals into colloidal quantum dots (QDs), is presented. Laser fragmentation is achieved by irradiating a CdSe suspension in dimethylformamide with intense infrared, picosecond laser pulses followed by surface passivation with oleylamine or different types of phosphines. The generated QDs reveal perfect colloidal stability preventing agglomeration and precipitation, and show characteristic QD absorption and fluorescence characteristics, whereas their emission properties strongly depend on the surface states and applied capping ligands. These QDs show distinct photoemission under 405-nm single-photon and 800-nm multi-photon excitations in the 560- to 610-nm spectral region corresponding to the QDs size of about 1.5–2 nm in diameter which is confirmed by transmission electron microscopy.

  7. Soliton compression to ultra-short pulses using cascaded quadratic nonlinearities in silica photonic crystal fibers

    DEFF Research Database (Denmark)

    Bache, Morten; Lægsgaard, Jesper; Bang, Ole;

    2007-01-01

    We investigate the possibility of using poled silica photonic crystal fibers for self-defocusing soliton compression with cascaded quadratic nonlinearities. Such a configuration has promise due to the desirable possibility of reducing the group-velocity mismatch. However, this unfortunately leads...... nonlinearity, and show that compression of nJ pulses to few-cycle duration is possible in such a fiber. A small amount of group-velocity mismatch optimizes the compression.......We investigate the possibility of using poled silica photonic crystal fibers for self-defocusing soliton compression with cascaded quadratic nonlinearities. Such a configuration has promise due to the desirable possibility of reducing the group-velocity mismatch. However, this unfortunately leads...

  8. Satellite and Opacity Effects on Resonance Line Shapes Produced from Short-Pulse Laser Heated Foils

    Energy Technology Data Exchange (ETDEWEB)

    Shepherd, R; Audebert, P; Chen, H-K; Fournier, K B; Peyreusse, O; Moon, S; Lee, R W; Price, D; Klein, L; Gauthier, J C; Springer, P

    2002-12-03

    We measure the He-like, time-resolved emission from thin foils consisting of 250 {angstrom} of carbon-250 {angstrom} of aluminum and 500 {angstrom} aluminum illuminated with a 150 fs laser pulse at an intensity of 1 x 10{sup 19} W/cm{sup 2}. Dielectronic satellite contributions to the 1s{sup 2}-1s2p({sup 1}P), 1s{sup 2}-1s3p({sup 1}P), and 1s{sup 2}1s4p({sup 1}P) line intensities are modeled using the configuration averaged code AVERROES and is found to be significant for all three resonance lines. The contribution of opacity broadening is inferred from the data and found to be significant only in the 1s{sup 2}-1s2p({sup 1}P).

  9. Particle characteristics of different materials after ultra-short pulsed laser (USPL) irradiation

    Science.gov (United States)

    Meister, Joerg; Schelle, Florian; Kowalczyk, Philip; Frentzen, Matthias

    2012-01-01

    The exposition of nanoparticles caused by laser application in dental health care is an open discussion. Based on the fact that nanoparticles can penetrate through the mucosa, the knowledge about particle characteristics after irradiation with an USPL is of high importance. Therefore, the aim of this study was to investigate the particle characteristics, especially the size of the ablated debris after USPL irradiation. The irradiation was carried out with an USP Nd:YVO4 laser with a center wavelength of 1064 nm. Based on the pulse duration of 8 ps and a pulse repetition rate of 500 kHz the laser emits an average power of 9 W. The materials investigated were dental tissues and dental restorative materials (composite and amalgam), ceramic and different metals (gold and aluminium). The samples were irradiated with a power density in the order of 300 GW/cm2 at distances of 5, 10, 15, and 20 mm. The debris was collected on an object plate. SEM pictures were used for analysis of the ablation debris. Depending on the irradiated material, we observed different kinds of structures: vitreous, flocculent, and pellet-like. The mean particle sizes were 10 x 10 up to 30 x 30 μm2. In addition, a cluster of ablated matter (nanometer range) distributed over the whole irradiated area was found. With increasing distances the cluster structure reduced from multi-layer to mono-layer clusters. Particle sizes in the micrometer and nanometer range were found after irradiation with an USPL. The nanoparticles create a cluster structure which is influenced by increasing distances.

  10. An old male patient with paroxysmal chest distress,shortness of breath and edema of both lower extremities (the 27th case)

    Institute of Scientific and Technical Information of China (English)

    陈琪

    2008-01-01

    @@ The patient,a 78-year-old male,was admitted to the hospital on Nov.15,2007 because of paroxysmal chest distress and shortness of breath for 11years and edema of lower extremities for 3 days.The patient began to suffer from paroxysmal chest distress and shortness of breath after exertion in 1997,then these symptoms recurred frequently,which lasted 10 min to several hours.

  11. Nonlinear Dichroism in Back-to-Back Double Ionization of He by an Intense Elliptically Polarized Few-Cycle Extreme Ultraviolet Pulse.

    Science.gov (United States)

    Ngoko Djiokap, J M; Manakov, N L; Meremianin, A V; Hu, S X; Madsen, L B; Starace, Anthony F

    2014-11-28

    Control of double ionization of He by means of the polarization and carrier-envelope phase (CEP) of an intense, few-cycle extreme ultraviolet (XUV) pulse is demonstrated numerically by solving the six-dimensional two-electron, time-dependent Schrödinger equation for He interacting with an elliptically polarized XUV pulse. Guided by perturbation theory (PT), we predict the existence of a nonlinear dichroic effect (∝I^{3/2}) that is sensitive to the CEP, ellipticity, peak intensity I, and temporal duration of the pulse. This dichroic effect (i.e., the difference of the two-electron angular distributions for opposite helicities of the ionizing XUV pulse) originates from interference of first- and second-order PT amplitudes, allowing one to probe and control S- and D-wave channels of the two-electron continuum. We show that the back-to-back in-plane geometry with unequal energy sharing is an ideal one for observing this dichroic effect that occurs only for an elliptically polarized, few-cycle attosecond pulse.

  12. Differential light effects on the dark motility rhythm in Euglena gracilis by series of short light pulses: Induction of long-term fluctuations and holding of the circadian oscillator

    Science.gov (United States)

    Balzer, Ivonne; Hardeland, Rüdiger

    1991-12-01

    Dark motility was measured by means of an infrared beam in stationary, 8- to 10-months-old autotrophic cultures of Euglena gracilis, strain Z. Controls in constant darkness exhibited circadian rhythms for several weeks. Cells were subjected to series of short light pulses of 800 lx covering, in most of the experiments, not more than 1/240 of the intermittent dark periods. When the overall amount of light per day was kept constant, the results of the light treatment strongly depended on the frequency of the light pulses. In light/dard cycles of more than 1 h, the circadian rhythmicity persited, whereas the oscillator was affected by cycles of 40 min or less. Such treatment by a high-frequency series of light pulses led to long-term fluctuations lasting for several days and a subsequent holding of the oscillator. The temporal position of extreme values of the fluctuations correlated with the frequency of the light pulses. The potency of light to suppress rhythmicity, as known from fading-out phenomena in constant illumination, is not restricted to the continuous presence of light, but is also immanent in the Zeitgeber signals of dark/light transitions. Hence, the results reflect differential effects in the action of light.

  13. Short-pulsed diode lasers as an excitation source for time-resolved fluorescence applications and confocal laser scanning microscopy in PDT

    Science.gov (United States)

    Kress, Matthias; Meier, Thomas H.; El-Tayeb, Tarek A. A.; Kemkemer, Ralf; Steiner, Rudolf W.; Rueck, Angelika C.

    2001-11-01

    This article describes a setup for subcellular time-resolved fluorescence spectroscopy and fluorescence lifetime measurements using a confocal laser scanning microscope in combination with a short pulsed diode laser for fluorescence excitation and specimen illumination. The diode laser emits pulses at 398 nm wavelength with 70 ps full width at half maximum (FWHM) duration. The diode laser can be run at a pulse repetition rate of 40 MHz down to single shot mode. For time resolved spectroscopy a spectrometer setup consisting of an Czerny Turner spectrometer and a MCP-gated and -intensified CCD camera was used. Subcellular fluorescence lifetime measurements were achieved using a time-correlated single photon counting (TCSPC) module instead of the spectrometer setup. The capability of the short pulsed diode laser for fluorescence imaging, fluorescence lifetime measurements and time-resolved spectroscopy in combination with laser scanning microscopy is demonstrated by fluorescence analysis of several photosensitizers on a single cell level.

  14. Compression and radiation of high-power short rf pulses. II. A novel antenna array design with combined compressor/radiator elements

    KAUST Repository

    Sirenko, Kostyantyn

    2011-01-01

    The paper discusses the radiation of compressed high power short RF pulses using two different types of antennas: (i) A simple monopole antenna and (ii) a novel array design, where each of the elements is constructed by combining a compressor and a radiator. The studies on the monopole antenna demonstrate the possibility of a high power short RF pulse\\'s efficient radiation even using simple antennas. The studies on the novel array design demonstrate that a reduced size array with lower pulse distortion and power decay can be constructed by assembling the array from elements each of which integrates a compressor and a radiator. This design idea can be used with any type of antenna array; in this work it is applied to a phased array.

  15. VERNIER CHRONOTRON UTILIZING AT LEAST TWO SHORTED DELAY LINES

    Science.gov (United States)

    Rufer, R.P.

    1964-02-25

    An improved vernier chronotron featuring pulse-forming circuits of a ringing'' or back and forth'' oscillatory type is described. A delay line shorted at both ends together with transistor circuitry to introduce a pulse into that line and also to provide reinforcement of the pulse as it oscillates between the pulse-reflective extremities is provided. A transistorized coincidence circuit is also provided. Enhanced measurement of time intervals in the nanosecond range is afforded. (AEC)

  16. The formation of diffuse discharge by short-front nanosecond voltage pulses and the modification of dielectrics in this discharge

    Science.gov (United States)

    Orlovskii, V. M.; Panarin, V. A.; Shulepov, M. A.

    2014-07-01

    The dynamics of diffuse discharge formation under the action of nanosecond voltage pulses with short fronts (below 1 ns) in the absence of a source of additional preionization and the influence of a dielectric film on this process have been studied. It is established that the diffuse discharge is induced by the avalanche multiplication of charge initiated by high-energy electrons and then maintained due to secondary breakdowns propagating via ionized gas channels. If a dielectric film (polyethylene, Lavsan, etc.) is placed on the anode, then multiply repeated discharge will lead to surface and bulk modification of the film material. Discharge-treated polyethylene film exhibits a change in the optical absorption spectrum in the near-IR range.

  17. The steady state of a particle in a vibrating box and possible application in short pulse generation of charged particles

    Indian Academy of Sciences (India)

    Nandan Jha; Sudhir R Jain

    2013-09-01

    In this paper the classical evolution of a particle is studied which bounces back and forth in a 1D vibrating cavity such that the reflection from the wall does not change the speed of the particle. A peculiar behaviour of the particle motion can be seen where the time evolution of the motion shows superposition of linear and oscillatory behaviour. In particular, the parameter range is found in which the particle oscillates between the walls in steady state as if the wall was static and it is showed that for these parameter ranges the particle settles to this steady state for all initial conditions. It is proposed that this phenomenon can be used to bunch charged particles in short pulses where the synchronization proposed in our model should work against the space charge effect in the charged particle bunch.

  18. The new methods of treatment for age-related macular degeneration using the ultra-short pulsed laser

    Science.gov (United States)

    Iwamoto, Yumiko; Awazu, Kunio; Suzuki, Sachiko; Ohshima, Tetsuro; Sawa, Miki; Sakaguchi, Hirokazu; Tano, Yasuo; Ohji, Masahito

    2007-02-01

    The non-invasive methods of treatments have been studying for the improvement of quality of life (QOL) of patients undergoing treatment. A photodynamic therapy (PDT) is one of the non-invasive treatments. PDT is the methods of treatment using combination of a laser and a photosensitizer. PDT has few risks for patients. Furthermore, PDT enables function preservation of a disease part. PDT has been used for early cancer till now, but in late years it is applied for age-related macular degeneration (AMD). AMD is one of the causes of vision loss in older people. However, PDT for AMD does not produce the best improvement in visual acuity. The skin photosensivity by an absorption characteristic of a photosensitizer is avoided. We examined new PDT using combination of an ultra-short pulsed laser and indocyanine green (ICG).

  19. Laser Processing of Carbon Fiber Reinforced Plastics - Release of Carbon Fiber Segments During Short-pulsed Laser Processing of CFRP

    Science.gov (United States)

    Walter, Juergen; Brodesser, Alexander; Hustedt, Michael; Bluemel, Sven; Jaeschke, Peter; Kaierle, Stefan

    Cutting and ablation using short-pulsed laser radiation are promising technologies to produce or repair CFRP components with outstanding mechanical properties e.g. for automotive and aircraft industry. Using sophisticated laser processing strategies and avoiding excessive heating of the workpiece, a high processing quality can be achieved. However, the interaction of laser radiation and composite material causes a notable release of hazardous substances from the process zone, amongst others carbon fiber segments or fibrous particles. In this work, amounts and geometries of the released fiber segments are analyzed and discussed in terms of their hazardous potential. Moreover, it is investigated to what extent gaseous organic process emissions are adsorbed at the fiber segments, similar to an adsorption of volatile organic compounds at activated carbon, which is typically used as filter material.

  20. Correlation dynamics between electrons and ions in the fragmentation of D$_2$ molecules by short laser pulses

    CERN Document Server

    Tong, X M; Lin, C D

    2003-01-01

    We studied the recollision dynamics between the electrons and D$_2^+$ ions following the tunneling ionization of D$_2$ molecules in an intense short pulse laser field. The returning electron collisionally excites the D$_2^+$ ion to excited electronic states from there D$_2^+$ can dissociate or be further ionized by the laser field, resulting in D$^+$ + D or D$^+$ + D$^+$, respectively. We modeled the fragmentation dynamics and calculated the resulting kinetic energy spectrum of D$^+$ to compare with recent experiments. Since the recollision time is locked to the tunneling ionization time which occurs only within fraction of an optical cycle, the peaks in the D$^+$ kinetic energy spectra provides a measure of the time when the recollision occurs. This collision dynamics forms the basis of the molecular clock where the clock can be read with attosecond precision, as first proposed by Corkum and coworkers. By analyzing each of the elementary processes leading to the fragmentation quantitatively, we identified ho...

  1. Dimensionality reduction in nonlinear optical datasets via diffusion mapping: case study of short-pulse second harmonic generation

    Science.gov (United States)

    Romanov, Dmitri; Smith, Stanley; Brady, John; Levis, Robert J.

    2008-02-01

    We have studied the application of the diffusion mapping technique to dimensionality reduction and clustering in multidimensional optical datasets. The combinational (input-output) data were obtained by sampling search spaces related to optimization of a nonlinear physical process, short-pulse second harmonic generation. The diffusion mapping technique hierarchically reduces the dimensionality of the data set and unifies the statistics of input (the pulse shape) and output (the integral output intensity) parameters. The information content of the emerging clustered pattern can be optimized by modifying the parameters of the mapping procedure. The low-dimensional pattern captures essential features of the nonlinear process, based on a finite sampling set. In particular, the apparently parabolic two-dimensional projection of this pattern exhibits regular evolution with the increase of higher-intensity data in the sampling set. The basic shape of the pattern and the evolution are relatively insensitive to the size of the sampling set, as well as to the details of the mapping procedure. Moreover, the experimental data sets and the sets produced numerically on the basis of a theoretical model are mapped into patterns of remarkable similarity (as quantified by the similarity of the related quadratic-form coefficients). The diffusion mapping method is robust and capable of predicting higher-intensity points from a set of low-intensity points. With these attractive features, diffusion mapping stands poised to become a helpful statistical tool for preprocessing analysis of vast and multidimensional combinational optical datasets.

  2. Development Of A Compact Photo-injector With RF-focusing Lens For Short Pulse Electron Source Application

    CERN Document Server

    Grabenhofer, Alexander; Shin, Young-Min

    2014-01-01

    For development of compact ultrafast electron source system, we are currently designing a short-pulse RF-gun with RF focusing structure by means of a series of comprehensive modeling analysis processes. EM design of a 2.5 cell resonant cavity with input coupler, acceleration dynamics of photo-emitted electron bunch, EM design of RF-lens with input coupler, and phasespace analysis of focused electron bunch are systematically examined with multi-physics simulators. All the features of the 2.856 GHz cavity geometry were precisely engineered for acceleration energies ranging from 100 keV to 500 keV (safety limited) to be powered by our 5 MW S-band klystron. The klystron (Thales TH2163) and modulator system (ScandiNova K1 turnkey system) were successfully installed and tested. Performance tests of the klystron system show peak output power > 5 MW, as per operation specifications. At the quasi-relativistic energies, the electron source is capable of generating 100fC -- 1 pC electron bunch with pulse duration close ...

  3. Computational study of the generation of crystal defects in a bcc metal target irradiated by short laser pulses

    Science.gov (United States)

    Lin, Zhibin; Johnson, Robert A.; Zhigilei, Leonid V.

    2008-06-01

    The generation of crystal defects in a Cr target irradiated by a short, 200 fs, laser pulse is investigated in computer simulations performed with a computational model that combines the classical molecular dynamics method with a continuum description of the laser excitation of conduction band electrons, electron-phonon coupling, and electron heat conduction. Interatomic interactions are described by the embedded atom method (EAM) potential with a parametrization designed for Cr. The potential is tested by comparing the properties of the EAM Cr material with experimental data and predictions of density functional theory calculations. The simulations are performed at laser fluences close to the threshold for surface melting. Fast temperature variation and strong thermoelastic stresses produced by the laser pulse are causing surface melting and epitaxial resolidification, transient appearance of a high density of stacking faults along the {110} planes, and generation of a large number of point defects (vacancies and self-interstitials). The stacking faults appear as a result of internal shifts in the crystal undergoing a rapid uniaxial expansion in the direction normal to the irradiated surface. The stacking faults are unstable and disappear shortly after the laser-induced tensile stress wave leaves the surface region of the target. Thermally activated generation of vacancy-interstitial pairs during the initial temperature spike and quick escape of highly mobile self-interstitials to the melting front or the free surface of the target, along with the formation of vacancies at the solid-liquid interface during the fast resolidification process, result in a high density of vacancies, on the order of 10-3 per lattice site, created in the surface region of the target. The strong supersaturation of vacancies can be related to the incubation effect in multipulse laser ablation/damage and should play an important role in mixing/alloying of multicomponent or composite

  4. Field and photo-emission in a short-pulse, high-charge Cesium telluride RF photoinjector

    Science.gov (United States)

    Wisniewski, Eric E.

    A new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5 cell 1.3 GHz gun uses a Cesium telluride photocathode driven with a 248 nm laser to provide short-pulse, high charge electron beams for the new 75 MeV drive beamline. The high-gradient RF gun (peak field on the cathode > 80MV/m) is a key piece of the facility upgrade. The large Cs2Te photocathode (diameter > 30 mm) was fabricated in-house. The photo-injector will be used to generate high-charge, short pulse, single bunches (Q > 100 nC) and bunch-trains (Q > 1000 nC) for wakefield experiments, typically involving dielectric-loaded accelerating structures. Details of the photocathode fabrication process and the results of associated diagnostic measurements are presented, including QE measurements and work function measurements performed with a Kelvin probe. Fieldemitted dark current from the Cs2Te cathode was measured during RF conditioning and characterized. Fowler-Nordheim plots of the data are presented and compared to similar measurements made using a copper cathode in the initial phase of conditioning. The results for cesium telluride exhibited non-linear regions within the Fowler-Nordheim plots similar to previous experimental results for other p-type semiconductors. Results of quantum efficiency (QE) studies are presented with the cathode operating in both single and bunch-train modes. QE uniformity and lifetime studies are presented. During commissioning, the cesium telluride photocathode produced bunch-charge of 100 nC, breaking the previous record. No evidence of bunch-train position-dependence of QE was found when generating four-bunch trains with total charge up to 200 nC.

  5. Short-pulse Er:YAG laser increases bond strength of composite resin to sound and eroded dentin.

    Science.gov (United States)

    Cersosimo, Maria Cecília Pereira; Matos, Adriana Bona; Couto, Roberta Souza D'Almeida; Marques, Márcia Martins; de Freitas, Patricia Moreira

    2016-04-30

    This study evaluated the influence of the irradiation with a short-pulse Er:YAG laser on the adhesion of composite resin to sound and eroded dentin (SD and ED). Forty-six samples of occlusal dentine, obtained from human molars, had half of their surface protected, while the other half was submitted to erosive cycles. Afterward, 23 samples were irradiated with Er:YAG laser, resulting in four experimental groups: SD, sound irradiated dentine (SID—Er:YAG, 50  μs 50  μs , 2 Hz, 80 mJ, and 12.6  J/cm 2 12.6  J/cm2 ), ED, and eroded irradiated dentin (EID—erosion + Er:YAG laser). A self-etching adhesive system was used, and then cylinders of composite resin were prepared. A microshear bond strength test was performed after 24 h storage (n=20 n=20 ). The morphology of SD and ED, with or without Er:YAG laser irradiation, was evaluated under scanning electron microscopy (n=3 n=3 ). Bond strength values (MPa) were subjected to analysis of variance followed by Tukey’s test. Statistically significant differences were found among the experimental groups: SD (9.76±3.39  B 9.76±3.39  B ), SID (12.77±5.09 A 12.77±5.09 A ), ED (5.12±1.72 D 5.12±1.72 D ), and EID (7.62±3.39 C 7.62±3.39 C ). Even though erosion reduces the adhesion to dentin, the surface irradiation with a short-pulse Er:YAG laser increases adhesion to both ED and SD.

  6. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P

    2003-07-28

    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  7. Computational modeling of stress transient and bubble evolution in short-pulse laser irradiated melanosome particles

    Energy Technology Data Exchange (ETDEWEB)

    Strauss, M.; Amendt, P.A.; London, R.A.; Maitland, D.J.; Glinsky, M.E.; Lin, C.P.; Kelly, M.W.

    1997-03-04

    Objective is to study retinal injury by subnanosecond laser pulses absorbed in the retinal pigment epithelium (RPE) cells. The absorption centers in the RPE cell are melanosomes of order 1 {mu}m radius. Each melanosome includes many melanin particles of 10-15 nm radius, which are the local absorbers of the laser light and generate a discrete structure of hot spots. This work use the hydrodynamic code LATIS (LAser-TISsue interaction modeling) and a water equation of state to first simulate the small melanin particle of 15 nm responsible for initiating the hot spot and the pressure field. A average melanosome of 1 {mu}m scale is next simulated. Supersonic shocks and fast vapor bubbles are generated in both cases: the melanin scale and the melanosome scale. The hot spot induces a shock wave pressure than with a uniform deposition of laser energy. It is found that an absorption coefficient of 6000 -8000 cm{sup -1} can explain the enhanced shock wave emitted by the melanosome. An experimental and theoretical effort should be considered to identify the mechanism for generating shock wave enhancement.

  8. Thermalization time of thin metal film heated by short pulse laser

    Institute of Scientific and Technical Information of China (English)

    Xu Hong-Yu; Zhang Yuan-Chong; Song Ya-Qin; Chen Dian-Yun

    2004-01-01

    Based on the hyperbolic two-step heat conduction model, using the Laplace transform and numerical inverse transform method (Riemann-sum approximation method), the thermal behaviour of thin metal films has been studied during femtosecond pulse laser heating. Also the thermalization time, which is the time for the electron gas and solid lattice to reach thermal balance, has been studied in detail. The values of thermalization time for silver (Ag), gold (Au),copper (Cu) and lead (Pb) are obtained. The effects of material parameters of the thin metal film on the thermalization time are considered for the four kinds of metals by changing one of the parameters and regarding the other parameters as constant. For a typical metal material, the order of the thermalization time is of the order of hundreds of picoseconds.The thermalization time decays exponentially with the increase of phonon-electron coupling factor or electron gas thermal conductivity, and it increases linearly with the increase of the ratio of lattice heat capacity to electron gas heat capacity. However, the relaxation time of the electron gas has very little effect on the thermalization time.

  9. Relativistic electron transport in wire and foil targets driven by intense short pulse lasers

    Science.gov (United States)

    Mason, R. J.; Stephens, R. B.; Wei, M.; Freeman, R. R.; Hill, J.; van Woerkom, L. D.

    2006-10-01

    We model intense laser driven electron transport in wires and foils with the new implicit hybrid code e-PLAS. We focus on background plasma heating for Fast Ignitor applications. The model tracks collisional relativistic PIC electrons undergoing scatter and drag in a background plasma of colliding cold electron and ion Eulerian fluids. Application to 10 μm diameter, 250 μm long, fully ionized carbon wires with an attached cone [Kodama et al. Nature 432 1005 (2004)], exposed to 1 ps, 10^19 W/cm^2 pulses in a 30 μm centered spot, directly calculates resistive Joule heating of the background electrons in the wire to 1.7 KeV. 150 MG magnetic fields arise at the wire surfaces corresponding to hot electron flow outside the wire and a return electron flow just within it. Shorter wires (25 μm) exhibit hot electron recycling. Preliminary simulations indicate that reduction of the cone to a 30 μm diameter nail head produces little change in these results. We also report on tapered wires, wires attached to foils, and the modifying effects of pre-plasma on electron transport into the foils.

  10. Heating in short-pulse laser-driven cone-capped wire targets

    Science.gov (United States)

    Mason, R. J.; Wei, M.; King, J.; Beg, F.; Stephens, R. B.

    2007-11-01

    The 2-D implicit hybrid simulation code e-PLAS has been used to study heating in cone-capped copper wire targets. The code e-PLAS tracks collisional particle-in-cell (PIC) electrons traversing background plasma of collisional Eulerian cold electron and ion fluids. It computes E- and B-fields by the Implicit Moment Method [1,2]. In recent experiments [3] at the Vulcan laser facility, sub- picosecond laser pulses at 1.06 μm, and 4.0 x 10^20 W/cm^2 intensity were focused into thin-walled (˜10 μm) cones attached to copper wires. The wire diameter was varied from 10-40 μm with a typical length of 1 mm. We characterize heating of the wires as a function of their diameters and length, and relate modifications of this heating to changes in the assumed laser-generated hot electron spectrum and directivity. As in recent nail experiments [4], the cones can serve as reservoirs for hot electrons, diverting them from passage down the wires. [1] R. J. Mason, and C. Cranfill, IEEE Trans. Plasma Sci. PS-14, 45 (1986). [2] R. J. Mason, J. Comp. Phys. 71, 429 (1987). [3] J. King et al., to be submitted to Phys. Rev. Lett.. [4] R. J. Mason, M. Wei, F. Beg, R. Stephens, and C. Snell, in Proc. of ICOPS07, Albuquerque, NM, June 17-22, 2007, Talk 7D4.

  11. Thermalization time of thin metal film heated by short pulse laser

    Science.gov (United States)

    Xu, Hong-Yu; Zhang, Yuan-Chong; Song, Ya-Qin; Chen, Dian-Yun

    2004-10-01

    Based on the hyperbolic two-step heat conduction model, using the Laplace transform and numerical inverse transform method (Riemann-sum approximation method), the thermal behaviour of thin metal films has been studied during femtosecond pulse laser heating. Also the thermalization time, which is the time for the electron gas and solid lattice to reach thermal balance, has been studied in detail. The values of thermalization time for silver (Ag), gold (Au), copper (Cu) and lead (Pb) are obtained. The effects of material parameters of the thin metal film on the thermalization time are considered for the four kinds of metals by changing one of the parameters and regarding the other parameters as constant. For a typical metal material, the order of the thermalization time is of the order of hundreds of picoseconds. The thermalization time decays exponentially with the increase of phonon-electron coupling factor or electron gas thermal conductivity and it increases linearly with the increase of the ratio of lattice heat capacity to electron gas heat capacity. However, the relaxation time of the electron gas has very little effect on the thermalization time.

  12. Pondermotive acceleration of electrons to GeV energies by a tightly focused ultra-short ultra-intense laser pulse

    Science.gov (United States)

    Tian, Youwei; Yu, Wei; Lu, Peixiang; He, Feng; Xu, Han

    2005-12-01

    Laser-driven pondermotive acceleration of electrons in vacuum has been considered using computer simulations. It is demonstrated that a low-energy free electron can be violently accelerated to final kinetic energy of GeV by a tightly focused ultra-short ultra-intense laser pulse. Suitable conditions that are crucial for this phenomenon to occur have been investigated. It is shown that selection of appropriate initial conditions like relative time delay between electron and the laser pulse, electron's incident angle and momentum, laser pulse duration and its focal spot size play important roles in the efficient acceleration scheme.

  13. Hot dense matter creation in short-pulse laser interaction with tamped foils

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S; Pasley, J; Beg, F; Gregori, G; Evans, R G; Notley, M; Mackinnon, A; Glenzer, S; Hansen, S; King, J; Chung, H; Wilks, S; Stephens, R; Freeman, R; Weber, R; Saiz, E G; Khattak, F; Riley, D

    2006-08-15

    The possibility of producing hot dense matter has important applications for the understanding of transport processes in inertial confinement fusion (ICF) [1] and laboratory astrophysics experiments [2]. While the success of ICF requires the correct solution of a complex interaction between laser coupling, equation-of-state, and particle transport problems, the possibility of experimentally recreating conditions found during the ignition phase in a simplified geometry is extremely appealing. In this paper we will show that hot dense plasma conditions found during ICF ignition experiments can be reproduced by illuminating a tamped foil with a high intensity laser. We will show that temperatures on the order of kiloelectronvolts at solid densities can be achieved under controlled conditions during the experiment. Hydrodynamic tamping by surface coatings allows to reach higher density regimes by enabling the diagnosis of matter that has not yet begun to decompress, thus opening the possibility of directly investigating strongly coupled systems [3]. Our experimental diagnostics is based on K-shell spectroscopy coupled to x-ray imaging techniques. Such techniques have recently become prevalent in the diagnosis of hot dense matter [4]. By looking at the presence, and relative strengths, of lines associated with different ionization states, spectroscopy provides considerable insight into plasma conditions. At the same time, curved crystal imaging techniques allow for the spatial resolution of different regions of the target, both allowing for comparison of heating processes with the results of Particle-In-Cell (PIC) and hybrid simulation codes.

  14. Facing the Future: Effects of Short-Term Climate Extremes on Isoprene-Emitting and Nonemitting Poplar1

    Science.gov (United States)

    Vanzo, Elisa; Jud, Werner; Li, Ziru; Albert, Andreas; Domagalska, Malgorzata A.; Ghirardo, Andrea; Niederbacher, Bishu; Frenzel, Juliane; Beemster, Gerrit T.S.; Asard, Han; Rennenberg, Heinz; Sharkey, Thomas D.; Hansel, Armin; Schnitzler, Jörg-Peter

    2015-01-01

    Isoprene emissions from poplar (Populus spp.) plantations can influence atmospheric chemistry and regional climate. These emissions respond strongly to temperature, [CO2], and drought, but the superimposed effect of these three climate change factors are, for the most part, unknown. Performing predicted climate change scenario simulations (periodic and chronic heat and drought spells [HDSs] applied under elevated [CO2]), we analyzed volatile organic compound emissions, photosynthetic performance, leaf growth, and overall carbon (C) gain of poplar genotypes emitting (IE) and nonemitting (NE) isoprene. We aimed (1) to evaluate the proposed beneficial effect of isoprene emission on plant stress mitigation and recovery capacity and (2) to estimate the cumulative net C gain under the projected future climate. During HDSs, the chloroplastidic electron transport rate of NE plants became impaired, while IE plants maintained high values similar to unstressed controls. During recovery from HDS episodes, IE plants reached higher daily net CO2 assimilation rates compared with NE genotypes. Irrespective of the genotype, plants undergoing chronic HDSs showed the lowest cumulative C gain. Under control conditions simulating ambient [CO2], the C gain was lower in the IE plants than in the NE plants. In summary, the data on the overall C gain and plant growth suggest that the beneficial function of isoprene emission in poplar might be of minor importance to mitigate predicted short-term climate extremes under elevated [CO2]. Moreover, we demonstrate that an analysis of the canopy-scale dynamics of isoprene emission and photosynthetic performance under multiple stresses is essential to understand the overall performance under proposed future conditions. PMID:26162427

  15. Facing the Future: Effects of Short-Term Climate Extremes on Isoprene-Emitting and Nonemitting Poplar.

    Science.gov (United States)

    Vanzo, Elisa; Jud, Werner; Li, Ziru; Albert, Andreas; Domagalska, Malgorzata A; Ghirardo, Andrea; Niederbacher, Bishu; Frenzel, Juliane; Beemster, Gerrit T S; Asard, Han; Rennenberg, Heinz; Sharkey, Thomas D; Hansel, Armin; Schnitzler, Jörg-Peter

    2015-09-01

    Isoprene emissions from poplar (Populus spp.) plantations can influence atmospheric chemistry and regional climate. These emissions respond strongly to temperature, [CO2], and drought, but the superimposed effect of these three climate change factors are, for the most part, unknown. Performing predicted climate change scenario simulations (periodic and chronic heat and drought spells [HDSs] applied under elevated [CO2]), we analyzed volatile organic compound emissions, photosynthetic performance, leaf growth, and overall carbon (C) gain of poplar genotypes emitting (IE) and nonemitting (NE) isoprene. We aimed (1) to evaluate the proposed beneficial effect of isoprene emission on plant stress mitigation and recovery capacity and (2) to estimate the cumulative net C gain under the projected future climate. During HDSs, the chloroplastidic electron transport rate of NE plants became impaired, while IE plants maintained high values similar to unstressed controls. During recovery from HDS episodes, IE plants reached higher daily net CO2 assimilation rates compared with NE genotypes. Irrespective of the genotype, plants undergoing chronic HDSs showed the lowest cumulative C gain. Under control conditions simulating ambient [CO2], the C gain was lower in the IE plants than in the NE plants. In summary, the data on the overall C gain and plant growth suggest that the beneficial function of isoprene emission in poplar might be of minor importance to mitigate predicted short-term climate extremes under elevated [CO2]. Moreover, we demonstrate that an analysis of the canopy-scale dynamics of isoprene emission and photosynthetic performance under multiple stresses is essential to understand the overall performance under proposed future conditions.

  16. Effect of pulsed short wave diathermy on skeletal muscle injury in rabbits.

    Science.gov (United States)

    Brown, M; Baker, R D

    1987-02-01

    The purpose of this study was to determine whether short wave diathermy (SWD) would enhance healing of a skeletal muscle injury. Thirty-two rabbits were divided into the following four groups: Experimental Group 1 (n = 8), which was given SWD twice daily for 8 consecutive days; Control Group 1 (n = 8), which was followed for 8 days but not given treatment; Experimental Group 2 (n = 8), which was given SWD twice daily for 16 consecutive days; and Control Group 2 (n = 8), which was followed for 16 days but not given treatment. The muscle injury was induced by giving all 32 rabbits three local injections of a myotoxic drug into the right gastrocnemius muscle. After the 8 or 16 days, all muscles were removed, then embedded in paraffin or frozen, sectioned, stained with adenosine triphosphatase or hematoxylin and eosin and examined with a light microscope. No statistically significant differences in the degree of muscle healing were found between the animals in Experimental Group 1 and Control Group 1 and those in Experimental Group 2 and Control Group 2. A trend toward faster resolution of the muscle injury was observed among those rabbits in Experimental Group 2 as compared with those rabbits in Control Group 2. Further study is required to determine whether SWD can be more effective for enhancing recovery from skeletal muscle injury.

  17. QCL seeded, ns-pulse, multi-line, CO2 laser oscillator for laser-produced-plasma extreme-UV source

    Science.gov (United States)

    Nowak, Krzysztof Michał; Suganuma, Takashi; Kurosawa, Yoshiaki; Ohta, Takeshi; Kawasuji, Yasufumi; Nakarai, Hiroaki; Saitou, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru; Sumitani, Akira; Endo, Akira

    2017-01-01

    Successful merger of state-of-the-art, semiconductor quantum-cascade lasers (QCL), with the mature CO2 laser technology, resulted in a delivery of highly-desired qualities of CO2 laser output that were not available previously without much effort. These qualities, such as multi-line operation, excellent spectro-temporal stability and pulse waveform control, became available from a single device of moderate complexity. This paper describes the operation principle and the unique properties of the solid{state seeded CO2 laser, invented for an application in laser-produced-plasma (LPP), extreme-UV (EUV) light source.

  18. Formation of silicon carbide and diamond nanoparticles in the surface layer of a silicon target during short-pulse carbon ion implantation

    Science.gov (United States)

    Remnev, G. E.; Ivanov, Yu. F.; Naiden, E. P.; Saltymakov, M. S.; Stepanov, A. V.; Shtan'ko, V. F.

    2009-04-01

    Synthesis of silicon carbide and diamond nanoparticles is studied during short-pulse implantation of carbon ions and protons into a silicon target. The experiments are carried out using a TEMP source of pulsed powerful ion beams based on a magnetically insulated diode with radial magnetic field B r . The beam parameters are as follows: the ion energy is 300 keV, the pulse duration is 80 ns, the beam consists of carbon ions and protons, and the ion current density is 30 A/cm2. Single-crystal silicon wafers serve as a target. SiC nanoparticles and nanodiamonds form in the surface layer of silicon subjected to more than 100 pulses. The average coherent domain sizes in the SiC particles and nanodiamonds are 12-16 and 8-9 nm, respectively.

  19. 短脉冲激光作用下丙酮液池的温度场计算%Temperature Calculation in Acetone Pool Under Short Pulsed Laser - heated

    Institute of Scientific and Technical Information of China (English)

    金仁喜; 华顺芳; 刘登瀛; 张正芳

    2001-01-01

    采用短脉冲激光加热浸没在丙酮液体里的钥薄膜电阻,并结合数值模拟计算,研究了高温升率条件下丙酮液体温度场随时间的变化规律及汽泡行为,得到丙酮液池温度过界层的数量级大约为30~40μm。认为薄汽膜的形成和热边界层外移是激光脉冲过后很长一段时间内汽泡依然长大的主要原因,确定了铂薄膜电阻的激光反射损失。%Extremely small platinum film that is immersed in acetone pool is heated by short pulsed laser. Acetone temperature variations and its boiling bubble behavior are studied experimentally and by two -dimensional heat conduction numerical simulation. It shows that the thermal boundary layer in acetone is an order of 30~ 40μm, and the formation of vapor and thermal boundary layer being thicker are the main reasons that vapor bubble still grows up long after laser pulse shorts. Laser reflection loss by platinum film is calculated.

  20. Amplification of short pulses from a mode-locked diode laser in an ytterbium-doped fiber

    NARCIS (Netherlands)

    Hekelaar, M.G.; Adhimoolam, B.; Gross, P.; Lindsay, I.D.; Boller, Klaus J.

    2005-01-01

    We report the first mode-locked diode laser at 1.04 µm with subsequent amplification of the pulses in an ytterbium-doped fiber amplifier. The generated pulses have a pulse duration of 70ps and peak power of 50W.